首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7526篇
  免费   851篇
  国内免费   1篇
  8378篇
  2022年   65篇
  2021年   167篇
  2020年   94篇
  2019年   110篇
  2018年   133篇
  2017年   129篇
  2016年   183篇
  2015年   338篇
  2014年   339篇
  2013年   395篇
  2012年   499篇
  2011年   499篇
  2010年   307篇
  2009年   286篇
  2008年   390篇
  2007年   415篇
  2006年   386篇
  2005年   358篇
  2004年   315篇
  2003年   334篇
  2002年   287篇
  2001年   120篇
  2000年   100篇
  1999年   104篇
  1998年   93篇
  1997年   73篇
  1996年   59篇
  1995年   65篇
  1994年   67篇
  1993年   49篇
  1992年   80篇
  1991年   93篇
  1990年   73篇
  1989年   101篇
  1988年   80篇
  1987年   79篇
  1986年   62篇
  1985年   57篇
  1984年   72篇
  1983年   52篇
  1982年   47篇
  1981年   38篇
  1980年   52篇
  1979年   58篇
  1978年   58篇
  1976年   45篇
  1974年   46篇
  1973年   47篇
  1972年   36篇
  1971年   36篇
排序方式: 共有8378条查询结果,搜索用时 19 毫秒
61.
Orally bioavailable, dual inhibitors of TIE-2/VEGF-R2 were identified by elaborating the C3/N13 SAR around a fused pyrrolodihydroindazolocarbazole scaffold. Analogs bearing a C3-thiophencarbonyl group were evaluated in enzymatic and cellular biochemical assays; two orally bioavailable analogs were further profiled in functional assays and found to inhibit microvessel growth in rat aortic explant cultures and inhibit Ang-1-stimulated chemotaxis of HUVECs.  相似文献   
62.
Prion infection and pathogenesis are dependent on the agent crossing an epithelial barrier to gain access to the recipient nervous system. Several routes of infection have been identified, but the mechanism(s) and timing of in vivo prion transport across an epithelium have not been determined. The hamster model of nasal cavity infection was used to determine the temporal and spatial parameters of prion-infected brain homogenate uptake following inhalation and to test the hypothesis that prions cross the nasal mucosa via M cells. A small drop of infected or uninfected brain homogenate was placed below each nostril, where it was immediately inhaled into the nasal cavity. Regularly spaced tissue sections through the entire extent of the nasal cavity were processed immunohistochemically to identify brain homogenate and the disease-associated isoform of the prion protein (PrPd). Infected or uninfected brain homogenate was identified adhering to M cells, passing between cells of the nasal mucosa, and within lymphatic vessels of the nasal cavity at all time points examined. PrPd was identified within a limited number of M cells 15 to 180 min following inoculation, but not in the adjacent nasal mucosa-associated lymphoid tissue (NALT). While these results support M cell transport of prions, larger amounts of infected brain homogenate were transported paracellularly across the respiratory, olfactory, and follicle-associated epithelia of the nasal cavity. These results indicate that prions can immediately cross the nasal mucosa via multiple routes and quickly enter lymphatics, where they can spread systemically via lymph draining the nasal cavity.  相似文献   
63.
Polymyxin peptide conjugated to the end groups of highly branched poly(N-isopropyl acrylamide) was shown to bind to a Gram negative bacterium, Pseudomonas aeruginosa . The nonbound polymer had a lower critical solution temperature (LCST) above 60 °C. However, binding caused aggregation, which was disrupted on cooling of the bacteria and polymer mixture. The data indicate that polymer binding of bacteria occurred by interaction of the end groups with lipopolysaccharide and that the binding decreased the LCST to below 37 °C. Cooling then progressed the polymer/bacteria aggregate through a bound LCST into an open polymer coil conformation that was not adhesive to P. aeruginosa .  相似文献   
64.
Summary Callus was initiated from in vitro-grown plants of Gladiolus cultivars ‘Jenny Lee’ and ‘Florida Flame.’ The age of callus used for regeneration of plants was either 9 mo. old or 8 yr old from ‘Jenny Lee,’ and 4 mo. old from ‘Florida Flame.’ Regeneration medium consisted of Murashige and Skoog’s basal salts medium supplemented with 2.0 mg/l (9.3 μM) kinetin. This medium was supplemented with various concentrations of either bialaphos (Meiji Seika, Tokyo, Japan) or phosphinothricin (Hoechst-Roussell, Frankfurt, Germany). Bialaphos was more effective than phosphinothricin at stimulating plant regeneration. Plants regenerated from 8-yr-old callus of ‘Jenny Lee’ only when the regeneration medium was supplemented with 0.10 mg/l bialaphos. A bialaphos concentration of 0.01 mg/l stimulated regeneration from 9-mo.-old callus of cultivar ‘Jenny Lee’ and 4-mo.-old callus of ‘Florida Flame.’  相似文献   
65.
66.
67.
68.

Background  

Thioredoxin reductase (TR) is a redox active protein involved in many cellular processes as part of the thioredoxin system. Presently there are three recognised forms of mammalian thioredoxin reductase designated as TR1, TR3 and TGR, that represent the cytosolic, mitochondrial and novel forms respectively. In this study we elucidated the genomic organisation of the mouse (Txnrd1) and human thioredoxin reductase 1 genes (TXNRD1) through library screening, restriction mapping and database mining.  相似文献   
69.
70.
Severe Plasmodium falciparum malaria encompasses a complex syndrome affecting many organs and causing physiological perturbations that have many features in common with children with sepsis. Among these, metabolic acidosis has emerged as a central feature of severe malaria and is the best independent predictor of a fatal outcome in both adults and children. There is now clear evidence that intravascular hypovolaemia (shock) is common in children with malarial acidosis. How it should be treated presents a therapeutic dilemma because acidosis often coexists with impaired consciousness (cerebral malaria). We summarize the results of recent clinical trials examining the safety and efficacy of volume expansion in children with 'cerebral malaria' complicated by acidosis.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号