全文获取类型
收费全文 | 7195篇 |
免费 | 487篇 |
国内免费 | 11篇 |
出版年
2023年 | 78篇 |
2022年 | 118篇 |
2021年 | 396篇 |
2020年 | 156篇 |
2019年 | 194篇 |
2018年 | 295篇 |
2017年 | 202篇 |
2016年 | 276篇 |
2015年 | 430篇 |
2014年 | 420篇 |
2013年 | 548篇 |
2012年 | 546篇 |
2011年 | 520篇 |
2010年 | 316篇 |
2009年 | 263篇 |
2008年 | 313篇 |
2007年 | 335篇 |
2006年 | 264篇 |
2005年 | 215篇 |
2004年 | 211篇 |
2003年 | 159篇 |
2002年 | 153篇 |
2001年 | 114篇 |
2000年 | 89篇 |
1999年 | 69篇 |
1998年 | 48篇 |
1997年 | 36篇 |
1996年 | 31篇 |
1995年 | 29篇 |
1994年 | 26篇 |
1993年 | 28篇 |
1992年 | 64篇 |
1991年 | 47篇 |
1990年 | 58篇 |
1989年 | 52篇 |
1988年 | 42篇 |
1987年 | 33篇 |
1986年 | 39篇 |
1985年 | 35篇 |
1984年 | 41篇 |
1983年 | 38篇 |
1982年 | 38篇 |
1981年 | 37篇 |
1980年 | 45篇 |
1979年 | 20篇 |
1978年 | 32篇 |
1977年 | 20篇 |
1975年 | 19篇 |
1974年 | 28篇 |
1973年 | 21篇 |
排序方式: 共有7693条查询结果,搜索用时 31 毫秒
1.
2.
Ahmed Hasbi Jocelyne Polastron Stéphane Allouche Laura Stanasila Dominique Massotte Philippe Jauzac 《Journal of neurochemistry》1998,70(5):2129-2138
Abstract: Phosphorylation of G protein-coupled receptors is considered an important step during their desensitization. In SK-N-BE cells, recently presented as a pertinent model for the studies of the human δ-opioid receptor, pretreatment with the opioid agonist etorphine increased time-dependently the rate of phosphorylation of a 51-kDa membrane protein. Immunological characterization of this protein with an antibody, raised against the amino-terminal region of the cloned human δ-opioid receptor, revealed that it corresponded to the δ-opioid receptor. During prolonged treatment with etorphine, phosphorylation increased as early as 15 min to reach a maximum within 1 h. Phosphorylation and desensitization of adenylyl cyclase inhibition paralleled closely and okadaic acid inhibited the resensitization, a result strongly suggesting that phosphorylation of the δ-opioid receptor plays a prominent role in its rapid desensitization. The increase in phosphorylation of the δ-opioid receptor, as well as its desensitization, was not affected by H7, an inhibitor of protein kinase A and protein kinase C, but was drastically reduced by heparin or Zn2+ , known to act as G protein-coupled receptor kinase (GRK) inhibitors. These results are the first to show, on endogenously expressed human δ-opioid receptor, that a close link exists between receptor phosphorylation and agonist-promoted desensitization and that desensitization involves a GRK. 相似文献
3.
Branchingprocess(BP)isusedtomodeltheearlystagesofthespreadofasexuallytransmitteddisease.TheearlystagesofAIDSspreadwhichistransmittedbothhomosexuallyandheterosexuallyarestudiedasaBP. 相似文献
4.
5.
Amal Bhattacharya Mrinal Ghosh Amalesh Choudhury 《The Journal of eukaryotic microbiology》1987,34(4):403-405
Acanthamoeba rhysodes has been found to be a predominant intertidal benthic gymnamoeba in the mangrove ecosystem of Sundarbans of lower deltaic Bengal, facing the Bay. The sampling zones under study were the highest high tide regions, with characteristic mangrove litter-soil, inundated twice per month during the highest ebb of spring tide. Population abundance of this species, both in its trophic and cystic forms in the three distinct seasonal periods of pre-monsoon (March to June), monsoon (July to October), and post-monsoon (November to February) has been surveyed for over two years. These seasonal periods affect the physico-chemical parameters of the habitat substrata, including temperature, pH, and salinity. It has been found that the overall number of organisms per gram of soil attains peak value during the monsoon period. This value comes down in post-monsoon samples and is the least in pre-monsoon ones. 相似文献
6.
Energy is one of the most important factors in the socioeconomic development of a country. In a developing country like Malaysia, the development of islands is mostly related to the availability of electric power. Power generated by renewable energy sources has recently become one of the most promising solutions for the electrification of islands and remote rural areas. But high dependency on weather conditions and the unpredictable nature of these renewable energy sources are the main drawbacks. To overcome this weakness, different green energy sources and power electronic converters need to be integrated with each other. This study presents a battery storage hybrid standalone photovoltaic-wind energy power supply system. In the proposed standalone hybrid system, a DC-DC buck-boost bidirectional converter controller is used to accumulates the surplus hybrid power in the battery bank and supplies this power to the load during the hybrid power shortage by maintaining the constant dc-link voltage. A three-phase voltage source inverter complex vector control scheme is used to control the load side voltage in terms of the voltage amplitude and frequency. Based on the simulation results obtained from MATLAB/Simulink, it has been found that the overall hybrid framework is capable of working under variable weather and load conditions. 相似文献
7.
8.
Ahmed Imrul Mosaddek Nadira Umme Aktari Cao Fangbin He Xiaoyan Zhang Guoping Wu Feibo 《Planta》2016,243(4):973-985
Planta - The drought-stimulated gene expression of NCED, SUS, and KS - DHN and ABA signal cross-talk with other phytohormones maintains barley root growth under drought stress at pH 4.0 plus... 相似文献
9.
Tarun K. Dam Manju Sarkar Jharna Ghosal Amalesh Choudhury 《Molecular and cellular biochemistry》1992,117(1):1-9
Control Analysis has been carried out in the first steps of a rat liver glycolytic system. Attention has been focused on the effect of several glucose concentrations on the control, particularly regarding the role of glucokinase. From kinetic studies of the whole metabolic system we have obtained information on the flux variation under different glucose concentrations. This information together with the kinetics of glucokinase has allowed us to calculate Flux Control and Elasticity Coefficients for glucokinase and the Response Coefficient of the system with respect to glucose. The changes in of the value of Flux Control Coefficients demonstrates that in conditions of low glucose concentration, glucokinase is the main enzyme in controlling the flux through the pathway, but at high glucose concentration the control moves to phosphofructokinase. Next, we have compared our results with those obtained with the shortening and titration method, previously described (Torres, N.V., Mateo, F., Mélendez-Hevia, E. and Kacser, H., (1986) Biochem. J. 234, 169–174; Torres, N.V. and Meléndez-Hevia, E. 1991. Molec. Cell. Biochem. 101, 1–10). Furthermore, from knowledge of the enzyme kinetics of the system we have been able to build a model of the pathway that allows us computer similation of its behavior and calculation of the Flux Control Coefficient profile at different glucose concentrations. By the three methods the results correlate, supporting the use of the pathway substrate as external modulator of the metabolic system as a tool for practical application of Control Analysis. 相似文献
10.
O Ahmed 《BMJ (Clinical research ed.)》1980,280(6207):119