全文获取类型
收费全文 | 610篇 |
免费 | 37篇 |
出版年
2024年 | 2篇 |
2023年 | 4篇 |
2021年 | 12篇 |
2020年 | 9篇 |
2019年 | 8篇 |
2018年 | 18篇 |
2017年 | 15篇 |
2016年 | 9篇 |
2015年 | 29篇 |
2014年 | 28篇 |
2013年 | 45篇 |
2012年 | 44篇 |
2011年 | 39篇 |
2010年 | 29篇 |
2009年 | 31篇 |
2008年 | 35篇 |
2007年 | 43篇 |
2006年 | 46篇 |
2005年 | 34篇 |
2004年 | 28篇 |
2003年 | 35篇 |
2002年 | 27篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 6篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1991年 | 2篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1970年 | 3篇 |
排序方式: 共有647条查询结果,搜索用时 31 毫秒
61.
Dolic K Weinstock-Guttman B Marr K Valnarov V Carl E Hagemeier J Brooks C Kilanowski C Hojnacki D Ramanathan M Zivadinov R 《PloS one》2011,6(11):e28062
Background
The role of intra- and extra-cranial venous system impairment in the pathogenesis of various vascular, inflammatory and neurodegenerative neurological disorders, as well as in aging, has not been studied in detail. Nor have risk factors been determined for increased susceptibility of venous pathology in the intra-cranial and extra-cranial veins. The aim of this study was to investigate the association between presence of a newly proposed vascular condition called chronic cerebrospinal venous insufficiency (CCSVI) and environmental factors in a large volunteer control group without known central nervous system pathology.Methods and Findings
The data were collected in a prospective study from 252 subjects who were screened for medical history as part of the entry criteria and participated in the case-control study of CCSVI prevalence in multiple sclerosis (MS) patients, and then were analyzed post-hoc. All participants underwent physical and Doppler sonography examinations, and were assessed with a structured environmental questionnaire. Fullfilment of ≥2 positive venous hemodynamic (VH) criteria on Doppler sonography was considered indicative of CCSVI diagnosis. Risk and protective factors associated with CCSVI were analyzed using logistic regression analysis. Seventy (27.8%) subjects presented with CCSVI diagnosis and 153 (60.7%) presented with one or more VH criteria. The presence of heart disease (p = .001), especially heart murmurs (p = .007), a history of infectious mononucleosis (p = .002), and irritable bowel syndrome (p = .005) were associated with more frequent CCSVI diagnosis. Current or previous smoking (p = .029) showed a trend for association with more frequent CCSVI diagnosis, while use of dietary supplements (p = .018) showed a trend for association with less frequent CCSVI diagnosis.Conclusions
Risk factors for CCSVI differ from established risk factors for peripheral venous diseases. Vascular, infectious and inflammatory factors were associated with higher CCSVI frequency. 相似文献62.
Among new insights coming from the completion of sequencing of the human genome, reported in Nature and Science, are clues of how evolution has increased the complexity of species, and in particular how the genetic code has enabled this process. It is clear that life has not only evolved by increasing the number of genes, but also by ingeniously evolving an efficient code for expressing diversity in the building blocks (i.e. the amino acids). The rules of nucleic acid base pairing and the classification of amino acids according to hydrophobicity/hydrophilicity relationships define a binary DNA code, which determines the general biophysical characteristics of proteins. Sense and antisense strands can encode protein segments having inverted and complementary hydropathy. The underlying binary code controls association and dissociation of proteins and presumably represents a primordial code that might have emerged in the early stages of self-organizing biochemical cycles. It is the purpose of this communication to provide a perspective of the code in the context of a binary language from its primordial origin to its present day format and to propose to use this code as a genomic mining tool. 相似文献
63.
Chandra M Tschirgi ML Tardiff JC 《American journal of physiology. Heart and circulatory physiology》2005,289(5):H2112-H2119
How different mutations in cardiac troponin T (cTnT) lead to distinct secondary downstream cellular remodeling in familial hypertrophic cardiomyopathy (FHC) remains elusive. To explore the molecular basis for the distinct impact of different mutations in cTnT on cardiac myocytes, we studied mechanical activity of detergent-skinned muscle fiber bundles from different lines of transgenic (TG) mouse hearts that express wild-type cTnT (WTTG), R92W cTnT, R92L cTnT, and Delta-160 cTnT (deletion of amino acid 160). The amount of mutant cTnT is approximately 50% of the total myocellular cTnT in both R92W and R92L TG mouse hearts and approximately 35% in Delta-160 TG mouse hearts. Myofilament Ca2+ sensitivity was enhanced in all mutant cTnT TG cardiac muscle fibers. Compared with the WTTG fibers, Ca2+ sensitivity increased significantly at short sarcomere length (SL) of 1.9 microm (P < 0.001) in R92W TG fibers by 2.2-fold, in R92L by 2.0-fold, and in Delta-160 by 1.3-fold. At long SL of 2.3 microm, Ca2+ sensitivity increased significantly (P < 0.01) in a similar manner (R92W, 2.5-fold; R92L, 1.9-fold; Delta-160, 1.3-fold). Ca2+-activated maximal tension remained unaltered in all TG muscle fibers. However, tension-dependent ATP consumption increased significantly in Delta-160 TG muscle fibers at both short SL (23%, P < 0.005) and long SL (37%, P < 0.0001), suggesting a mutation-induced change in cross-bridge detachment rate constant. Chronic stresses on relative cellular ATP level in cardiac myocytes may cause a strain on energy-dependent Ca2+ homeostatic mechanisms. This may result in pathological remodeling that we observed in Delta-160 TG cardiac myocytes where the ratio of sarco(endo)plasmic reticulum Ca2+-ATPase 2/phospholamban decreased significantly. Our results suggest that different types of stresses imposed on cardiac myocytes would trigger distinct cellular signaling, which leads to remodeling that may be unique to some mutants. 相似文献
64.
Characterisation of uterine sarcoma cell lines exhibiting MDR phenotype by vibrational spectroscopy 总被引:1,自引:0,他引:1
Murali Krishna C Kegelaer G Adt I Rubin S Kartha VB Manfait M Sockalingum GD 《Biochimica et biophysica acta》2005,1726(2):160-167
Multidrug resistance (MDR) enables cancer cells to escape cytotoxic insults of anticancer drugs. Rapid identification of cells exhibiting the MDR phenotype is very important since it can lead to an effective and individual patient based treatment plan. We have investigated a combined vibrational spectroscopic approach, using both micro-Raman and FTIR techniques, in order to characterise a sensitive human uterine sarcoma cell line MES-SA and its multidrug-resistant derivative Garf. In this study, these two complementary methods have been evaluated via the use of principal components analysis (PCA), for discrimination of cells exhibiting the MDR phenotype. Our results indicate that, though they inherently have different sensitivities, both Raman and IR methods can provide a good differentiation of cell phenotypes. 相似文献
65.
In non-irrigated agricultural fields in tropical zones, high temperature and water stress prevail during the main cropping season. Natural epizootics of Beauveria bassiana on lepidopteran pests occur during winter. Application of B. bassiana during hot months when pest populations are at their climax may prove an effective management strategy. Therefore, 29 isolates of B. bassiana were tested for their ability to germinate and grow in temperature and water availability conditions prevailing during the pest season in these fields. The effect of temperature cycles with 8 h duration of high temperature fluctuating with 16 h duration of lower temperature (similar to field conditions); low water availability; and a combination of these two stress conditions was studied. Germination and growth assays were done at fluctuating temperature cycles of 32, 35, 38, and 42+/-1 degrees C (8 h)/25+/-1 degrees C (16 h) and in media with water stress created by 10, 20, 30, and 40% polyethylene glycol (PEG 6000). Assays set at a continuous temperature of 25+/-1 degrees C with no PEG in the medium served as controls. Stress was assessed as percentage germination or as growth relative to control. Isolates showing 90% growth relative to the control at temperature cycles including high temperatures of 35 and 38+/-1 degrees C were identified. One isolate (ARSEF 2860) had a thermal threshold above 43 degrees C. At 25 degrees C, all but one isolate of B. bassiana showed >90% growth relative to the control in 10% PEG (-0.45 MPa). Some isolates were found with >90% growth relative to control in medium having 30% PEG with water availability (1.33 MPa), nearly equivalent to that in soils which induce permanent wilting point of plants. When isolates that showed >90% growth relative to the control at both stress conditions, were stressed simultaneously, a decrease in growth was observed. Growth was reduced by approximately 20% at 35+/-1 degrees C (8 h)/25+/-1 degrees C (16 h) and 10% PEG and was affected to a greater degree in combinations of harsher stress conditions. The isolate ARSEF 2860 with a thermal threshold of >43 degrees C showed approximately 80% relative growth at a combined stress of 38+/-1 degrees C (8 h)/25+/-1 degrees C (16 h) and 10% PEG. These findings will aid the selection of isolates for use in field trials in hot or dry agricultural climates. 相似文献
66.
The health and wellness of an individual are reliant on the integrated effects of mind, body, and spirit. This triad is intricately set within a backdrop of the environment, our earth. Western cultures often disregard this holism, especially this fourth component, in its considerations of wellness as described by modern medicine. This practice is unlike that of many of the traditional cultures in the world. These cultures focus more on balance in the context of environmental respect. Varied cultures share remarkable similarities in their healing modalities, especially considering the relative isolation from one to another—evidence that there is truth to the healing knowledge they possess. We are not disconnected from the natural world in terms of health, but dependent and interconnected within ourselves and to everything around us. Social change is required to assure that the practice of modern medicine evolves to incorporate this integral aspect of health and wellness, and this can be done through partnerships with traditional healers.There is a growing demand for wellness and earthly responsibility. It is time to appropriately learn from age-old societies and their healing traditions for they do have answers we are seeking in sustainability and harmony, environmental stewardship and planetary respect, and holistic health. For thousands of years, our ancestors have known the secrets of long life—this knowledge needs to be preserved through the apprenticeship of future generations. We propose a collaboration that develops mutually beneficial learning partnerships combining modern medical knowledge with the wisdom of traditional healers around the world. 相似文献
67.
Woochang Hwang Young-Rae Cho Aidong Zhang Murali Ramanathan 《Algorithms for molecular biology : AMB》2006,1(1):24-11
Background
The sparse connectivity of protein-protein interaction data sets makes identification of functional modules challenging. The purpose of this study is to critically evaluate a novel clustering technique for clustering and detecting functional modules in protein-protein interaction networks, termed STM. 相似文献68.
69.
Ling Ling Sadasivam Murali Gary S. Stein Andre J. van Wijnen Simon M. Cool 《Journal of cellular biochemistry》2010,109(6):1222-1231
Skeletal integrity is tightly regulated by the activity of osteoblasts and osteoclasts that are both under the control of extracellular glycosaminoglycans (GAGs) through their interactions with endogenous growth factors and differentiation‐promoting ligands. Receptor activator of NF‐kappa‐B ligand (RANKL), which is a tumor necrosis factor (TNF)‐related protein that is critical for osteoclast formation, is produced by osteoblasts and further modulated by certain types of GAGs. Using unfractionated osteoblast‐derived GAGs that reflect the complex tissue microenvironment within which osteoclasts reside, we demonstrate that these GAGs block the osteoclastogenic activity of RANKL. Furthermore, RANKL significantly reduces extracellular signal‐regulated protein kinase (ERK) activity, a putative suppressor of osteoclastogenesis, but osteoblast‐derived GAGs eliminate the inhibitory effects of RANKL on ERK activity. Notably, while imposing an anti‐osteoclastic effect, these GAGs also enhanced the proliferation of osteoblasts. Thus, the osteoblast microenvironment is a potent source of GAGs that promote bone anabolic activities. The anti‐osteoclastogenic and osteoblast‐related mitogenic activities of these GAGs together may provide a key starting point for the development of selective sugar‐based therapeutic compounds for the treatment of osteopenic disorders. J. Cell. Biochem. 109: 1222–1231, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
70.
McCarl CA Khalil S Ma J Oh-hora M Yamashita M Roether J Kawasaki T Jairaman A Sasaki Y Prakriya M Feske S 《Journal of immunology (Baltimore, Md. : 1950)》2010,185(10):5845-5858
ORAI1 is the pore-forming subunit of the Ca(2+) release-activated Ca(2+) (CRAC) channel, which is responsible for store-operated Ca(2+) entry in lymphocytes. A role for ORAI1 in T cell function in vivo has been inferred from in vitro studies of T cells from human immunodeficient patients with mutations in ORAI1 and Orai1(-/-) mice, but a detailed analysis of T cell-mediated immune responses in vivo in mice lacking functional ORAI1 has been missing. We therefore generated Orai1 knock-in mice (Orai1(KI/KI)) expressing a nonfunctional ORAI1-R93W protein. Homozygosity for the equivalent ORAI1-R91W mutation abolishes CRAC channel function in human T cells resulting in severe immunodeficiency. Homozygous Orai1(KI/KI) mice die neonatally, but Orai1(KI/KI) fetal liver chimeric mice are viable and show normal lymphocyte development. T and B cells from Orai1(KI/KI) mice display severely impaired store-operated Ca(2+) entry and CRAC channel function resulting in a strongly reduced expression of several key cytokines including IL-2, IL-4, IL-17, IFN-γ, and TNF-α in CD4(+) and CD8(+) T cells. Cell-mediated immune responses in vivo that depend on Th1, Th2, and Th17 cell function were severely attenuated in ORAI1-deficient mice. Orai1(KI/KI) mice lacked detectable contact hypersensitivity responses and tolerated skin allografts significantly longer than wild-type mice. In addition, T cells from Orai1(KI/KI) mice failed to induce colitis in an adoptive transfer model of inflammatory bowel disease. These findings reaffirm the critical role of ORAI1 for T cell function and provide important insights into the in vivo functions of CRAC channels for T cell-mediated immunity. 相似文献