全文获取类型
收费全文 | 1652篇 |
免费 | 96篇 |
国内免费 | 1篇 |
出版年
2023年 | 12篇 |
2022年 | 12篇 |
2021年 | 32篇 |
2020年 | 29篇 |
2019年 | 26篇 |
2018年 | 48篇 |
2017年 | 43篇 |
2016年 | 65篇 |
2015年 | 100篇 |
2014年 | 81篇 |
2013年 | 119篇 |
2012年 | 155篇 |
2011年 | 123篇 |
2010年 | 70篇 |
2009年 | 60篇 |
2008年 | 109篇 |
2007年 | 67篇 |
2006年 | 78篇 |
2005年 | 71篇 |
2004年 | 48篇 |
2003年 | 62篇 |
2002年 | 44篇 |
2001年 | 18篇 |
2000年 | 15篇 |
1999年 | 14篇 |
1998年 | 9篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 10篇 |
1989年 | 14篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1985年 | 12篇 |
1981年 | 5篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1975年 | 6篇 |
1974年 | 12篇 |
1973年 | 20篇 |
1972年 | 9篇 |
1971年 | 10篇 |
1970年 | 11篇 |
1969年 | 6篇 |
1968年 | 9篇 |
1967年 | 6篇 |
1966年 | 9篇 |
1965年 | 9篇 |
排序方式: 共有1749条查询结果,搜索用时 15 毫秒
91.
Hai-Sheng?Li Kuntala?Shome Raúl?Rojas Mark?A?Rizzo Chandrasekaran?Vasudevan Eric?Fluharty Lorraine?C?Santy James?E?Casanova Guillermo?RomeroEmail author 《BMC cell biology》2003,4(1):13
Background
Phospholipase D (PLD) is involved in many signaling pathways. In most systems, the activity of PLD is primarily regulated by the members of the ADP-Ribosylation Factor (ARF) family of GTPases, but the mechanism of activation of PLD and ARF by extracellular signals has not been fully established. Here we tested the hypothesis that ARF-guanine nucleotide exchange factors (ARF-GEFs) of the cytohesin/ARNO family mediate the activation of ARF and PLD by insulin. 相似文献92.
Norepinephrine-induced cardiac hypertrophy and fibrosis are not due to mast cell degranulation 总被引:5,自引:0,他引:5
The norepinephrine (NE)-induced hypertrophy of the left ventricle (LV) in the rat is preceded by increased interleukin (IL)-6 expression and associated with LV fibrosis. We have examined whether the elevated level of IL-6 may be due to mast cell degranulation. Therefore we tested the effect of cromoglycate sodium salt (cromolyn), an inhibitor of mast cell degranulation with anti-inflammatory and membrane-stabilizing activity, on the increased expression of IL-6 mRNA and of mRNAs of proteins involved in the remodelling of the extracellular matrix (ECM) which is induced by NE (0.1 mg/kg·h). After 4 h, the NE-induced increase in IL-6 mRNA expression was not influenced by cromolyn (20 mg/kg·h). Cromolyn-infusion for 3 days did not affect the extent of LV hypertrophy induced by NE, as measured by the LV weight/body weight (LVW/BW) ratio and by atrial natriuretic peptide (ANP) expression. Cromolyn induced a slight depression of the NE-induced elevation of the matrix metalloproteinase (MMP)-2. However, it did not affect the NE-induced elevated levels of mRNAs of collagen I and III and the tissue inhibitor of matrix metalloproteinase (TIMP)-2. Since cromolyn did not reduce the NE-effects in rat hearts in vivo we conclude that mast cell degranulation seems not to be involved in them. 相似文献
93.
94.
Sequential requirements of the N-terminal palmitoylation site and SH2 domain of Src family kinases in the initiation and progression of FcepsilonRI signaling 下载免费PDF全文
Honda Zi Suzuki T Kono H Okada M Yamamoto T Ra C Morita Y Yamamoto K 《Molecular and cellular biology》2000,20(5):1759-1771
Initial biochemical signaling originating from high-affinity immunoglobulin E receptor (FcepsilonRI) has been ascribed to Src family kinases. To understand the mechanisms by which individual kinases drive the signaling, we conducted reconstitution experiments: FcepsilonRI signaling in RBL2H3 cells was first suppressed by a membrane-anchored, gain-of-function C-terminal Src kinase and then reconstructed with Src family kinases whose C-terminal negative regulatory sequence was replaced with a c-myc epitope. Those constructs derived from Lyn and Fyn, which are associated with detergent-resistant membranes (DRMs), physically interacted with resting FcepsilonRI and reconstructed clustering-induced signaling that leads to calcium mobilization and ERK1 and -2 activation. c-Src-derived construct, which was excluded from DRMs, failed to interact with FcepsilonRI and to restore the signaling, whereas creation of palmitoylatable Cys3 enabled it to interact with DRMs and with FcepsilonRI and to restore the signaling. Deletion of Src homology 3 (SH3) domain from the Lyn-derived construct did not alter its ability to transduce the series of signaling. Deletion of SH2 domain did not affect its association with DRMs and with FcepsilonRI nor clustering-induced tyrosine phosphorylation of FcepsilonRI beta and gamma subunits, but it almost abrogated the next step of tyrosine phosphorylation of Syk and its recruitment to FcepsilonRI. These findings suggest that Lyn and Fyn could, but c-Src could not, drive FcepsilonRI signaling and that N-terminal palmitoylation and SH2 domain are required in sequence for the initial interaction with FcepsilonRI and for the signal progression to the molecular assembly. 相似文献
95.
Furumoto Y Hiraoka S Kawamoto K Masaki S Kitamura T Okumura K Ra C 《Biochemical and biophysical research communications》2000,273(2):765-771
Genetic polyymorphisms that result in three amino acid changes in FcepsilonRI beta chain (Ile(181)-->Leu, Val(183)-->Leu, and Glu(237)-->Gly) have been identified as candidates that associate with allergic disorders such as atopy and asthma. To elucidate the biological significance of these polymorphisms in regulating the expression and function of FcepsilonRI, we generated four types of transfectants that express wild-type or mutant mouse beta chains corresponding to these human variants by retrovirus-mediated gene transfer into beta chain-deficient mouse-derived mast cells. No significant functional differences between the wild-type beta chain transfectant and any of the mutant beta chain transfectants were observed in beta-hexosaminidase release, intracellular calcium mobilization, or cytokine and leukotriene C(4) production in response to FcepsilonRI crosslinking. Our results suggest that these polymorphisms in FcepsilonRI beta chain do not affect FcepsilonRI-mediated mast cell activation at least in our mouse in vitro system. 相似文献
96.
Zaĭchenko MI Mikhaĭlova NG Raĭgorodskiĭ IuV 《Zhurnal vysshe? nervno? deiatelnosti imeni I P Pavlova》2000,50(3):492-499
Unit activity in the right and left prefrontal cortex was recorded in male Wistar rats after testing by the emotional resonance technique. Rats were divided in two groups by their reaction to the suffering cry of a partner. Rats from the group A ("altruists") escaped partner's crying, and those from the group E ("egoists") did not. Activity of neurons was analyzed in hungry rats, after feeding, during intracranial emotionally positive and negative stimulation, and during crying of the rat partner. Some differences in neural activity between A and E groups were revealed. In the hungry state the rate of neuronal discharges was higher in the A group. In both groups of animals the positive emotional stimulation was accompanied by more intensive neuronal reaction that the negative stimulation, but in the E group increase in the rate of neuronal discharges in both hemispheres was significantly more pronounced. Negative stimulation produced in both groups a significantly greater activation in the left hemisphere than in the right one while during the positive stimulation the neural activity was more intensive in the left hemisphere. The neuronal reaction to partner's crying was significantly higher in the A group in both hemispheres, while the neuronal activity in E group did not significantly change. 相似文献
97.
Haluk Topcuoglu Salim Hariri Dongmin Kim Yoonhee Kim Xue Bing Baoqing Ye Ilkyeun Ra Jon Valente 《Cluster computing》1998,1(1):81-93
Current advances in high-speed networks such as ATM and fiber-optics, and software technologies such as the JAVA programming
language and WWW tools, have made network-based computing a cost-effective, high-performance distributed computing environment.
Metacomputing, a special subset of network-based computing, is a well-integrated execution environment derived by combining
diverse and distributed resources such as MPPs, workstations, mass storage, and databases that show a heterogeneous nature
in terms of hardware, software, and organization. In this paper we present the Virtual Distributed Computing Environment (VDCE),
a metacomputing environment currently being developed at Syracuse University. VDCE provides an efficient web-based approach
for developing, evaluating, and visualizing large-scale distributed applications that are based on predefined task libraries
on diverse platforms. The VDCE task libraries relieve end-users of tedious task implementations and also support reusability.
The VDCE software architecture is described in terms of three modules: (a) the Application Editor, a user-friendly application
development environment that generates the Application Flow Graph (AFG) of an application; (b) the Application Scheduler,
which provides an efficient task-to-resource mapping of AFG; and (c) the VDCE Runtime System, which is responsible for running
and managing application execution and for monitoring the VDCE resources. We present experimental results of an application
execution on the VDCE prototype for evaluating the performance of different machine and network configurations. We also show
how the VDCE can be used as a problem-solving environment on which large-scale, network-centric applications can be developed
by a novice programmer rather than by an expert in low-level details of parallel programming languages.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
98.
Artificial endosperm of Cleopatra tangerine zygotic embryos: a model for somatic embryo encapsulation 总被引:1,自引:0,他引:1
Nieves Nadina Lorenzo Jose C. Blanco Maria de los A. González Justo Peralta Hipólito Hernández Martha Santos Ramón Concepción Oscar Borroto Carlos G. Borroto Eduviges Tapia Raúl Martinez Marcos E. Fundora Zaida González Alfredo 《Plant Cell, Tissue and Organ Culture》1998,54(2):77-83
Synthetic seed technology may be of value in breeding programs and allow the propagation of many elite genotype-derived plants
in a short time. In this work, a range of artificial endosperm treatments of Cleopatra tangerine zygotic embryos were evaluated
for suitability for encapsulation of somatic embryos. Different complexing ions in the form of alginate capsules, zeolite
as an ion exchanger and the relationship between capsule-nutrient gel on germination of zygotic embryos, were evaluated. Artificial
endosperm assays showed that abscisic acid (1 μM) and mannitol (0.25 M) delayed germination and conversion of zygotic embryos,
whereas amino acid supplements (proline, glutamic acid and arginine) accelerated the conversion process. An artificial endosperm
was used to encapsulate somatic and zygotic embryos. After encapsulation, zygotic embryos germinated after four days of culture
while somatic embryos germinated asynchronously after 20 days. Somatic embryo-derived plantlets showed greater vigour than
zygotic embryo-derived plantlets. Results showed that this artificial endosperm is adequate for Cleopatra tangerine somatic
embryo germination and conversion into plants.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
99.
Rocio Duque‐Jamaica Azucena Arévalo‐Galvis Raúl A. Poutou‐Piñales Alba A. Trespalacios 《Helicobacter》2010,15(4):303-312
Background: Colonization of the gastric mucosa by Helicobacter pylori is one of the most important causes of acute and chronic gastric pathologies in humans. Achieving the growth of H. pylori in liquid media is of great importance in the development of clinical studies. In this study, we developed a sequential optimization strategy based on statistical models to improve the conditions of liquid culture of H. pylori. Materials and Methods: Four statistical models were sequentially used. First, a Box‐Behnken design was used to select the best process conditions (shaking speed, inoculum concentration, and final volume of culture). Secondly, a general factorial design was used to evaluate the influence of adding gel blocks or gel beads (shape and composition). Then a D‐optimal reduce design was carried out to allow the selection of the most influential factors in increasing the cell concentration (culture media components). Finally, another Box‐Behnken design was used to optimize the concentration of the culture media components previously selected. Results: After 12 hours of liquid culture a concentration of 25 × 108 cells per mL (9.4 log10 cells per mL) of H. pylori was obtained, compared with a predicted 32 × 108 (9.5 log10 cells per mL), which means between 1 and 5 log10 units higher than some previous reports. Conclusions: The sequential statistical approach increased the planktonic H. pylori cell culture. The final culture media and conditions were: Brain Heart Infusion, blood agarose (1.5% w/v), lamb’s blood (3.18% v/v), DENT (0.11% v/v), and Vitox (0.52% v/v) at 60 rpm and 37 °C with filtered CO2 (5% v/v) bubbled directly into the culture media in a final volume of 76.22 mL. 相似文献
100.