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   10919篇
  免费   933篇
  国内免费   912篇
  2024年   29篇
  2023年   141篇
  2022年   259篇
  2021年   488篇
  2020年   360篇
  2019年   446篇
  2018年   503篇
  2017年   345篇
  2016年   495篇
  2015年   698篇
  2014年   834篇
  2013年   910篇
  2012年   1044篇
  2011年   914篇
  2010年   598篇
  2009年   421篇
  2008年   559篇
  2007年   462篇
  2006年   408篇
  2005年   374篇
  2004年   360篇
  2003年   365篇
  2002年   283篇
  2001年   181篇
  2000年   148篇
  1999年   173篇
  1998年   96篇
  1997年   70篇
  1996年   55篇
  1995年   68篇
  1994年   61篇
  1993年   42篇
  1992年   59篇
  1991年   51篇
  1990年   34篇
  1989年   32篇
  1988年   36篇
  1987年   19篇
  1986年   27篇
  1985年   23篇
  1984年   25篇
  1983年   15篇
  1982年   14篇
  1981年   14篇
  1979年   12篇
  1974年   12篇
  1973年   21篇
  1972年   12篇
  1966年   12篇
  1958年   13篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
991.
992.
993.
The kallikrein-kinin system (KKS) serves as the physiologic counterbalance to the renin-angiotensin system. This study was conducted to examine the changes in the expression of KKS components in podocytes under diabetic conditions and to elucidate the functional role of bradykinin (BK) in diabetes-associated podocyte apoptosis. Thirty-two rats were injected with either diluent (n = 16, C) or with streptozotocin intraperitoneally (n = 16, DM), and 8 rats from each group were treated with BK infusion for 6 weeks. Immortalized mouse podocytes were cultured in media containing 5.6 mmol/l glucose (NG), NG + 10(-7) mol/l AII (AII), or 30 mmol/l glucose (HG) with or without 10(-8) mol/l BK. Urinary albumin excretion was significantly higher in DM rats, and this increase was ameliorated by BK. Not only kininogen, kallikrein, and BK B1- and B2-receptor expression but also BK levels were significantly decreased in DM glomeruli and in cultured podocytes exposed to HG. The changes in the expressions of apoptosis-related molecules and the increase in the number of apoptotic cells in DM glomeruli as well as in HG- and AII-stimulated podocytes were significantly abrogated by BK. The suppressed KSS within podocytes under diabetic condition was associated with podocyte apoptosis, suggesting that BK may be beneficial in preventing podocyte loss in diabetic nephropathy.  相似文献   
994.
995.
ENA Actimineral Resource A (ENA-A) is alkaline water that is composed of refined edible cuttlefish bone and two different species of seaweed, Phymatolithon calcareum and Lithothamnion corallioides. In the present study, ENA-A was investigated as an antioxidant to protect against CCl(4)-induced oxidative stress and hepatotoxicity in rats. Liver injury was induced by either subacute or chronic CCl(4) administration, and the rats had free access to tap water mixed with 0% (control group) or 10% (v/v) ENA-A for 5 or 8?weeks. The results of histological examination and measurement of antioxidant activity showed that the reactive oxygen species production, lipid peroxidation, induction of CYP2E1 were decreased and the antioxidant activity, including glutathione and catalase production, was increased in the ENA-A groups as compared with the control group. On 2-DE gel analysis of the proteomes, 13 differentially expressed proteins were obtained in the ENA-A groups as compared with the control group. Antioxidant proteins, including glutathione S-transferase, kelch-like ECH-associated protein 1, and peroxiredoxin 1, were increased with hepatocyte nuclear factor 3-beta and serum albumin precursor, and kininogen precursor decreased more in the ENA-A groups than compared to the control group. In conclusion, our results suggest that ENA-A does indeed have some protective capabilities against CCl(4)-induced liver injury through its antioxidant function.  相似文献   
996.
The major processes generating pattern in plant community composition depend upon the spatial scale and resolution of observation, therefore understanding the role played by spatial scale on species patterns is of major concern. In this study, we investigate how well environmental (topography and soil variables) and spatial variables explain variation in species composition in a 25-ha temperate forest in northeastern China. We used new variation partitioning approaches to discover the spatial scale (using multi-scale spatial PCNM variables) at which environmental heterogeneity and other spatially structured processes influence tree community composition. We also test the effect of changing grain of the study (i.e. quadrat size) on the variation partitioning results. Our results indicate that (1) species composition in the Changbai mixed broadleaf-conifer forest was controlled mainly by spatially structured soil variation at broad scales, while at finer scales most of the explained variation was of a spatial nature, pointing to the importance of biotic processes. (2) These results held at all sampling grains. However, reducing quadrat size progressively reduced both spatially and environmentally explained variance. This probably partly reflects increasing stochasticity in species abundances, and the smaller proportion of quadrats occupied by each species, when quadrat size is reduced. The results suggest that environmental heterogeneity (i.e. niche processes) and other biotic processes such as dispersal work together, but at different spatial scales, to build up diversity patterns.  相似文献   
997.
998.
目的:探讨四逆散对疲劳大鼠学习记忆及脑内GABA_B1受体的影响。方法:应用游泳训练和睡眠剥夺方法复制疲劳动物模型,运用Y-迷宫检测各组大鼠的学习记忆能力,采用免疫组化方法检测大鼠脑内GABA_B1受体阳性反应物的变化。结果:模型组与正常组相比,大鼠Y-迷宫正确反应率明显下降,错误反应率明显升高,大鼠脑内GABA_B1的阳性反应物数目明显增多;中药治疗组与模型组相比,正确反应率明显升高,错误反应次数明显下降,脑内GABA_B1受体的阳性反应物数目明显减少。结论:四逆散对疲劳大鼠学习记忆能力的下降具有改善作用。  相似文献   
999.
Lee BH  Kim JY  Song S  Hur JM  Cho JY  Park YC 《Mitochondrial DNA》2011,22(5-6):168-170
The complete mitochondrial genome (JN415127) was sequenced and annotated newly from an individual of Hynobius yangi populations which were collected in Ulju-gun, Korea. The total length of the H. yangi genome is 16,403 bp, with a total base composition of 33.5% A, 32.3% T, 20.5% C, and 13.6% G.  相似文献   
1000.
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