全文获取类型
收费全文 | 1174篇 |
免费 | 72篇 |
专业分类
1246篇 |
出版年
2023年 | 7篇 |
2022年 | 18篇 |
2021年 | 31篇 |
2020年 | 18篇 |
2019年 | 20篇 |
2018年 | 24篇 |
2017年 | 35篇 |
2016年 | 45篇 |
2015年 | 50篇 |
2014年 | 59篇 |
2013年 | 84篇 |
2012年 | 93篇 |
2011年 | 84篇 |
2010年 | 47篇 |
2009年 | 44篇 |
2008年 | 55篇 |
2007年 | 63篇 |
2006年 | 49篇 |
2005年 | 60篇 |
2004年 | 44篇 |
2003年 | 54篇 |
2002年 | 42篇 |
2001年 | 10篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1996年 | 5篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1988年 | 5篇 |
1986年 | 4篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1976年 | 4篇 |
1928年 | 3篇 |
1926年 | 4篇 |
1913年 | 8篇 |
1912年 | 5篇 |
1911年 | 3篇 |
1910年 | 3篇 |
1909年 | 4篇 |
1908年 | 6篇 |
1907年 | 4篇 |
1904年 | 7篇 |
1865年 | 5篇 |
1860年 | 3篇 |
排序方式: 共有1246条查询结果,搜索用时 15 毫秒
91.
BACKGROUND: Traditionally, the bone maturity at birth has been estimated from the radiological presence and size of the ossified distal femoral epiphysis. This study was conducted in a search for a sonographic tool for the evaluation of neonatal bone maturity. METHODS: We examined sonographically 256 neonates within 24 h of birth. Gestational ages ranged from 36 to 42 weeks (mean: 39.4; median: 40). Birth weights ranged from 1,945 to 5,000 g (mean: 3,175; median: 3,180). The distal femoral epiphysis was imaged on the coronal plane sonogram of the distal femur with the knee at 90 degrees flexion and the distal femoral epiphysis maximal height was recorded. The acetabulum was imaged using Graf's method in the coronal plane image and the acetabular diameter recorded. RESULTS: It was found that plotting the distal femoral epiphysis against neonatal birth weight and gestational age provided a simple method for assessing the bone maturity. According to our study, a neonate can be regarded as bone maturity percentile X when plotting distal femoral epiphysis height or acetabulum diameter against birth weight and gestational age or when averaging the four readings. CONCLUSIONS: We suggest performing sonography of the distal femoral epiphysis as a bedside tool for the assessment of skeletal maturity in newborns. 相似文献
92.
Fiscella M Perry JW Teng B Bloom M Zhang C Leung K Pukac L Florence K Concepcion A Liu B Meng Y Chen C Elgin EC Kanakaraj P Kaufmann TE Porter J Cibotti R Mei Y Zhou J Chen G Roschke V Komatsoulis G Mansfield B Ruben S Sanyal I Migone TS 《Nature biotechnology》2003,21(3):302-307
A coordinated effort combining bioinformatic tools with high-throughput cell-based screening assays was implemented to identify novel factors involved in T-cell biology. We generated a unique library of cDNAs encoding predicted secreted and transmembrane domain-containing proteins generated by analyzing the Human Genome Sciences cDNA database with a combination of two algorithms that predict signal peptides. Supernatants from mammalian cells transiently transfected with this library were incubated with primary T cells and T-cell lines in several high-throughput assays. Here we describe the discovery of a T cell factor, TIP (T cell immunomodulatory protein), which does not show any homology to proteins with known function. Treatment of primary human and murine T cells with TIP in vitro resulted in the secretion of IFN-gamma, TNF-alpha, and IL-10, whereas in vivo TIP had a protective effect in a mouse acute graft-versus-host disease (GVHD) model. Therefore, combining functional genomics with high-throughput cell-based screening is a valuable and efficient approach to identifying immunomodulatory activities for novel proteins. 相似文献
93.
Reeve JR Green GM Chew P Eysselein VE Keire DA 《American journal of physiology. Gastrointestinal and liver physiology》2003,285(2):G255-G265
CCK-58 differs from CCK-8 in patterns of expression of pancreatic secretion of fluid and amylase and gallbladder contraction. These differences have physiological relevance only if CCK-58 release is stimulated by nutrients entering the intestine and if CCK-58 circulates in sizeable amounts. In this study, we report that when radiolabeled CCK-58 is added to rat blood and plasma is formed, there is extensive loss and degradation of the radioactive peptide. Therefore, a new method was developed to minimize loss and degradation of this label. This method recovered >85% of the label with no detectable degradation. Furthermore, the optimized method recovered all unlabeled exogenous cholecystokinin molecular forms in >80% yields. Blood from fasted rats and rats in which cholecystokinin release was stimulated by the trypsin inhibitor camostat contained only CCK-58 (3.5 +/- 0.5 and 17 +/- 1.5 fmol/ml, respectively). Because CCK-58 predominates in the blood, this molecular form should be used in studies on the physiology and pathophysiology of cholecystokinin. 相似文献
94.
Tóth EC Vissi E Kovács I Szöke A Ariño J Gergely P Dudits D Dombrádi V 《Plant molecular biology》2000,43(4):527-536
We detected an about 200 kDa holoenzyme of protein phosphatase 2A (PP2A) in the crude extract of Medicago sativa microcallus cells by gel permeation chromatography. By polymerase chain reaction (PCR) we isolated two M. sativa cDNA fragments corresponding to the catalytic (C) subunit, and one each coding for the A and the B regulatory subunits of PP2A. The C subunit sequences were different from that published previously, indicating the existence of at least three different isoforms in M. sativa. Using the PCR fragments as probes, we obtained two distinct full-length clones for both the A and B subunits from an alfalfa cDNA library. Our results demonstrate that the components of the PP2A holoenzyme, namely the catalytic and regulatory subunits, are present in alfalfa in several isoforms and that their sequences are highly similar to their plant, yeast and animal counterparts. The distinct regulatory subunit genes are constitutively expressed during the cell cycle. Interestingly, two A-B subunit pairs had parallel mRNA steady-state levels in different plant tissues suggesting that not all of the possible isoform combinations are present in all tissues. The expression of the MsPP2A B subunit form was induced by abscisic acid indicating a specific function for this protein in the stress response. 相似文献
95.
Elsa G. Escamilla-Chimal Claudia C. Garcí a-Rivera Marcela Aguilar-Morales Viktor J. Romero-Dí az Ma. Luisa L. Fanjul-Moles 《Biological Rhythm Research》1998,29(5):471-479
The aim of this work was to investigate possible changes in serotonin (5-HT) and tryptophan hydroxylase (TPH)-like immunoreactivity related to time of day in Procambarus clarkii retina during the first developmental stages. Forty-five animals from postembryonic instars (PO1, PO2) to juvenile stage were kept under LD 12:12 cycles. All animals were anesthetized and decapitated at three times of day, 08:00, 15:00 and 20:00 h. Isolated eyestalks were processed by immunohistochemical methods. The 5-HT-like immunoreactive area of retina was measured using computer-based image analysis. Results indicated 5-HT-like immunoreactive differences among the three crayfish instars studied. In PO1 animals, ANOVA revealed no significant differences in 5-HT-like immunoreactivity in the retina at different times of day. PO2 instars as well as juvenile instars, showed statistically significant retinal 5-HT-like immunoreactivity changes related to time of day. Preliminary results indicated that TPH-like immunoreactivity was located only in the tapetal and retinal cells, and it was related to time of day. These changes suggest a diurnal cyclic regulation in the synthesis of 5-HT in the retina. 相似文献
96.
Viktor Reinhardt 《Zoo biology》1985,4(3):295-300
During twelve 2-h observation sessions courtship behavior was recorded among seven musk-ox males (Ovibos moschatus) kept in a paddock together with six females. The animals were sexually mature and of the same age. Foreleg kicking and genital sniffing were more common than mounting. All three activities were of a nonaggressive nature but were shown almost exclusively by dominants toward subordinate partners. Assuming the role of courted females, recipients were never the target of aggressive acts. It was concluded that courtship among mature musk-ox males functions as a nonaggressive reinforcement of dominance, promoting low-risk coexistence of males. 相似文献
97.
A flexible multi-dimensional QoS performance measure framework for distributed heterogeneous systems
Jong-Kook Kim Debra A. Hensgen Taylor Kidd Howard Jay Siegel David St. John Cynthia Irvine Tim Levin N. Wayne Porter Viktor K. Prasanna Richard F. Freund 《Cluster computing》2006,9(3):281-296
When users’ tasks in a distributed heterogeneous computing environment (e.g., cluster of heterogeneous computers) are allocated
resources, the total demand placed on some system resources by the tasks, for a given interval of time, may exceed the availability
of those resources. In such a case, some tasks may receive degraded service or be dropped from the system. One part of a measure
to quantify the success of a resource management system (RMS) in such a distributed environment is the collective value of
the tasks completed during an interval of time, as perceived by the user, application, or policy maker. The Flexible Integrated
System Capability (FISC) measure presented here is a measure for quantifying this collective value. The FISC measure is a
flexible multi-dimensional measure such that any task attribute can be inserted and may include priorities, versions of a
task or data, deadlines, situational mode, security, application- and domain-specific QoS, and task dependencies. For an environment
where it is important to investigate how well data communication requests are satisfied, the data communication request satisfied
can be the basis of the FISC measure instead of tasks completed. The motivation behind the FISC measure is to determine the
performance of resource management schemes if tasks have multiple attributes that needs to be satisfied. The goal of this
measure is to compare the results of different resource management heuristics that are trying to achieve the same performance
objective but with different approaches.
This research was supported by the DARPA/ITO Quorum Program, by the DARPA/ISO BADD Program and the Office of Naval Research
under ONR grant number N00014-97-1-0804, by the DARPA/ITO AICE program under contract numbers DABT63-99-C-0010 and DABT63-99-C-0012,
and by the Colorado State University George T. Abell Endowment. Intel and Microsoft donated some of the equipment used in
this research.
Jong-Kook Kim is pursuing a Ph.D. degree from the School of Electrical and Computer Engineering at Purdue University (expected in August
2004). Jong-Kook received his M.S. degree in electrical and computer engineering from Purdue University in May 2000. He received
his B.S. degree in electronic engineering from Korea University, Seoul, Korea in 1998. He has presented his work at several
international conferences and has been a reviewer for numerous conferences and journals. His research interests include heterogeneous
distributed computing, computer architecture, performance measure, resource management, evolutionary heuristics, and power-aware
computing. He is a student member of the IEEE, IEEE Computer Society, and ACM.
Debra Hensgen is a member of the Research and Evaluation Team at OpenTV in Mountain View, California. OpenTV produces middleware for set-top
boxes in support of interactive television. She received her Ph.D. in the area of Distributed Operating Systems from the University
of Kentucky. Prior to moving to private industry, as an Associate Professor in the systems area, she worked with students
and colleagues to design and develop tools and systems for resource management, network re-routing algorithms and systems
that preserve quality of service guarantees, and visualization tools for performance debugging of parallel and distributed
systems. She has published numerous papers concerning her contributions to the Concurra toolkit for automatically generating
safe, efficient concurrent code, the Graze parallel processing performance debugger, the SAAM path information base, and the
SmartNet and MSHN Resource Management Systems.
Taylor Kidd is currently a Software Architect for Vidiom Systems in Portland Oregon. His current work involves the writing of multi-company
industrial specifications and the architecting of software systems for the digital cable television industry. He has been
involved in the establishment of international specifications for digital interactive television in both Europe and in the
US. Prior to his current position, Dr. Kidd has been a researcher for the US Navy as well as an Associate Professor at the
Naval Postgraduate School. Dr Kidd received his Ph.D. in Electrical Engineering in 1991 from the University of California,
San Diego.
H. J. Siegel was appointed the George T. Abell Endowed Chair Distinguished Professor of Electrical and Computer Engineering at Colorado
State University (CSU) in August 2001, where he is also a Professor of Computer Science. In December 2002, he became the first
Director of the CSU Information Science and Technology Center (ISTeC). ISTeC is a university-wide organization for promoting,
facilitating, and enhancing CSU’s research, education, and outreach activities pertaining to the design and innovative application
of computer, communication, and information systems. From 1976 to 2001, he was a professor at Purdue University. He received
two BS degrees from MIT, and the MA, MSE, and PhD degrees from Princeton University. His research interests include parallel
and distributed computing, heterogeneous computing, robust computing systems, parallel algorithms, parallel machine interconnection
networks, and reconfigurable parallel computer systems. He has co-authored over 300 published papers on parallel and distributed
computing and communication, is an IEEE Fellow, is an ACM Fellow, was a Coeditor-in-Chief of the Journal of Parallel and Distributed
Computing, and was on the Editorial Boards of both the IEEE Transactions on Parallel and Distributed Systems and the IEEE
Transactions on Computers. He was Program Chair/Co-Chair of three major international conferences, General Chair/Co-Chair
of four international conferences, and Chair/Co-Chair of five workshops. He has been an international keynote speaker and
tutorial lecturer, and has consulted for industry and government.
David St. John is Chief Information Officer for WeatherFlow, Inc., a weather services company specializing in coastal weather observations
and forecasts. He received a master’s degree in Engineering from the University of California, Irvine. He spent several years
as the head of staff on the Management System for Heterogeneous Networks project in the Computer Science Department of the
Naval Postgraduate School. His current relationship with cluster computing is as a user of the Regional Atmospheric Modeling
System (RAMS), a numerical weather model developed at Colorado State University. WeatherFlow runs RAMS operationally on a
Linux-based cluster.
Cynthia Irvine is a Professor of Computer Science at the Naval Postgraduate School in Monterey, California. She received her Ph.D. from
Case Western Reserve University and her B.A. in Physics from Rice University. She joined the faculty of the Naval Postgraduate
School in 1994. Previously she worked in industry on the development of high assurance secure systems. In 2001, Dr. Irvine
received the Naval Information Assurance Award. Dr. Irvine is the Director of the Center for Information Systems Security
Studies and Research at the Naval Postgraduate School. She has served on special panels for NSF, DARPA, and OSD. In the area
of computer security education Dr. Irvine has most recently served as the general chair of the Third World Conference on Information
Security Education and the Fifth Workshop on Education in Computer Security. She co-chaired the NSF workshop on Cyber-security
Workforce Needs Assessment and Educational Innovation and was a participant in the Computing Research Association/NSF sponsored
Grand Challenges in Information Assurance meeting. She is a member of the editorial board of the Journal of Information Warfare
and has served as a reviewer and/or program committee member of a variety of security related conferences. She has written
over 100 papers and articles and has supervised the work of over 80 students. Professor Irvine is a member of the ACM, the
AAS, a life member of the ASP, and a Senior Member of the IEEE.
Timothy E. Levin is a Research Associate Professor at the Naval Postgraduate School. He has spent over 18 years working in the design, development,
evaluation, and verification of secure computer systems, including operating systems, databases and networks. His current
research interests include high assurance system design and analysis, development of models and methods for the dynamic selection
of QoS security attributes, and the application of formal methods to the development of secure computer systems.
Viktor K. Prasanna received his BS in Electronics Engineering from the Bangalore University and his MS from the School of Automation, Indian
Institute of Science. He obtained his Ph.D. in Computer Science from the Pennsylvania State University in 1983. Currently,
he is a Professor in the Department of Electrical Engineering as well as in the Department of Computer Science at the University
of Southern California, Los Angeles. He is also an associate member of the Center for Applied Mathematical Sciences (CAMS)
at USC. He served as the Division Director for the Computer Engineering Division during 1994–98. His research interests include
parallel and distributed systems, embedded systems, configurable architectures and high performance computing. Dr. Prasanna
has published extensively and consulted for industries in the above areas. He has served on the organizing committees of several
international meetings in VLSI computations, parallel computation, and high performance computing. He is the Steering Co-chair
of the International Parallel and Distributed Processing Symposium [merged IEEE International Parallel Processing Symposium
(IPPS) and the Symposium on Parallel and Distributed Processing (SPDP)] and is the Steering Chair of the International Conference
on High Performance Computing(HiPC). He serves on the editorial boards of the Journal of Parallel and Distributed Computing
and the Proceedings of the IEEE. He is the Editor-in-Chief of the IEEE Transactions on Computers. He was the founding Chair
of the IEEE Computer Society Technical Committee on Parallel Processing. He is a Fellow of the IEEE.
Richard F. Freund is the originator of GridIQ’s network scheduling concepts that arose from mathematical and computing approaches he developed
for the Department of Defense in the early 1980’s. Dr. Freund has over twenty-five years experience in computational mathematics,
algorithm design, high performance computing, distributed computing, network planning, and heterogeneous scheduling. Since
1989, Dr. Freund has published over 45 journal articles in these fields. He has also been an editor of special editions of
IEEE Computer and the Journal of Parallel and Distributed Computing. In addition, he is a founder of the Heterogeneous Computing
Workshop, held annually in conjunction with the International Parallel Processing Symposium. Dr. Freund is the recipient of
many awards, which includes the prestigious Department of Defense Meritorious Civilian Service Award in 1984 and the Lauritsen-Bennet
Award from the Space and Naval Warfare Systems Command in San Diego, California. 相似文献
98.
Federenko YF Deogenov VA Kakuris KK Yerullis KB 《Biological trace element research》2011,143(2):668-676
Hypokinesia (HK) induces electrolyte losses in electrolyte-deficient tissue, yet the mechanisms of electrolyte losses in electrolyte-deficient
tissue remain unknown. Mechanisms of electrolyte deposition could be involved. To determine the effect of prolonged HK on
potassium (K+) deposition were measured muscle K+ content and K+ losses. Studies were conducted on 20 physically healthy male volunteers during 30 days pre-experimental period and 364 days
experimental period. Subjects were equally divided into two groups: control subjects (CS) and experimental subjects (ES).
The CS group was run average distances of 9.8 ± 1.7 km day−1 and the ES group was walked average distances of 2.7 ± 0.6 km day−1. Muscle K+ content decreased (p < 0.05) and plasma K+ concentration, and K+ losses in urine and feces increased (p < 0.05) in the ES group compared to their pre-experimental level and the values in their respective CS group. Muscle K+ content, plasma K+ level, and urine and fecal K+ losses did not show any changes in the CS group compared to their pre-experimental values. The conclusion was that K+ losses in K+-deficient muscle of healthy subjects could have been attributable to the less efficient K+ deposition inherently to prolonged HK. 相似文献
99.
Stejskal D Růzicka V Adamovská S Juráková R Prosková J Jedelský L Bartek J 《Biomedical papers of the Medical Faculty of the University Palacky, Olomouc, Czechoslovakia》2003,147(2):167-172
Adiponectin (ADP) is an adipocytokin with many antiatherogenic properties; its decreased level is associated with numerous atherogenic diseases and syndromes (e.g. diabetes mellitus (DM), dyslipidemia, endothelial dysfunction, hypertension, and obesity). Decreased ADP values in blood may be an independent risk factor of atherosclerotic (ATS) complications. AIM OF THE STUDY: 1) Do persons with type 2 diabetes have lower ADP values than individuals without DM but with a high risk of ATS complications? 2) Do ADP values differ between persons with well controlled and persons with uncontrolled type 2 diabetes? We examined 109 patients of the Metabolic Center of Hospital Sternberk. Out of them, 58 had type 2 diabetes, others were individuals with variously expressed risk factors of early atherosclerosis (obesity, hypertension, age, family history, smoking, dyslipidemia, etc.). In all persons under this study the following parameters were determined in peripheral venous blood: adiponectin, resistin, leptin, ObRe, cholesterol, HDL-cholesterol, triacylglycerols, glucose, HbA1c, creatinine, urea, ALT, AST, CRP, homocysteine, thrombocyte aggregation after CPG induction. The whole group was divided according to the presence of type 2DM into two subgroups; persons with diabetes were divided into the well controlled and uncontrolled subgroups. All data obtained were processed statistically using the software SPSS for Windows and Medcalc. The adiponectin/BMI index correlated negatively with HbA1c value (correlation coefficient -0.37, p = 0.00053), triacylglycerols (-0.4, p = 0.000001), P-glucose (-0.3, p = 0.0017), uricemia (-0.35, p = 0.0007) and positively with HDL-cholesterol value (0.6, p=0.00001). Women had higher adiponectin values than men. Persons with hypertension and with diabetes mellitus, individuals with atherogenic lipotype or persons with inflammation signs had lower values than individuals without these diseases and syndromes. Persons with wellcontrolled diabetes mellitus had higher values than persons with uncontrolled diabetes (medians of the adiponectin/BMI index 9.7 vs. 6.7, p < 0.01). Persons with type 2 diabetes mellitus have lower ADP values than persons with a high ATS risk without diabetes mellitus. Persons with wellcontrolled diabetes mellitus (DM) and with satisfactory compensation have significantly higher ADP levels (independently of other metabolic parameters of DM control). ADP may be a new marker of metabolic control in persons with a high risk of atherosclerotic complications. 相似文献
100.
Viktor Schiffner 《Plant Systematics and Evolution》1909,59(3):84-89
Ohne Zusammenfassung 相似文献