首页 | 官方网站   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   241376篇
  免费   8082篇
  国内免费   4916篇
数理化   254374篇
  2022年   2418篇
  2021年   2987篇
  2020年   3272篇
  2019年   3399篇
  2018年   3945篇
  2017年   3767篇
  2016年   5510篇
  2015年   4046篇
  2014年   5725篇
  2013年   11733篇
  2012年   10432篇
  2011年   12035篇
  2010年   8308篇
  2009年   8145篇
  2008年   10334篇
  2007年   10266篇
  2006年   9791篇
  2005年   8487篇
  2004年   7711篇
  2003年   6734篇
  2002年   6495篇
  2001年   7209篇
  2000年   5753篇
  1999年   4595篇
  1998年   3753篇
  1997年   3713篇
  1996年   3466篇
  1995年   3224篇
  1994年   2999篇
  1993年   2759篇
  1992年   3106篇
  1991年   2985篇
  1990年   2895篇
  1989年   2629篇
  1988年   2649篇
  1987年   2617篇
  1986年   2430篇
  1985年   3111篇
  1984年   3318篇
  1983年   2702篇
  1982年   2857篇
  1981年   2807篇
  1980年   2653篇
  1979年   2737篇
  1978年   2821篇
  1977年   2821篇
  1976年   2886篇
  1975年   2670篇
  1974年   2644篇
  1973年   2776篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
In this study, the functional interaction of HPLW peptide with VEGFR2 (Vascular Endothelial Growth Factor Receptor 2) was determined by using fast 15N‐edited NMR spectroscopic experiments. To this aim, 15N uniformly labelled HPLW has been added to Porcine Aortic Endothelial Cells. The acquisition of isotope‐edited NMR spectroscopic experiments, including 15N relaxation measurements, allowed a precise characterization of the in‐cell HPLW epitope recognized by VEGFR2.  相似文献   
22.
23.
24.
Three‐dimensional (3D) nanometal films serving as current collectors have attracted much interest recently owing to their promising application in high‐performance supercapacitors. In the process of the electrochemical reaction, the 3D structure can provide a short diffusion path for fast ion transport, and the highly conductive nanometal may serve as a backbone for facile electron transfer. In this work, a novel polypyrrole (PPy) shell@3D‐Ni‐core composite is developed to enhance the electrochemical performance of conventional PPy. With the introduction of a Ni metal core, the as‐prepared material exhibits a high specific capacitance (726 F g?1 at a charge/discharge rate of 1 A g?1), good rate capability (a decay of 33 % in Csp with charge/discharge rates increasing from 1 to 20 A g?1), and high cycle stability (only a small decrease of 4.2 % in Csp after 1000 cycles at a scan rate of 100 mV s?1). Furthermore, an aqueous symmetric supercapacitor device is fabricated by using the as‐prepared composite as electrodes; the device demonstrates a high energy density (≈21.2 Wh kg?1) and superior long‐term cycle ability (only 4.4 % and 18.6 % loss in Csp after 2000 and 5000 cycles, respectively).  相似文献   
25.
26.
27.
28.
29.
30.
Dioscin (DIS), one of the most abundant bioactive steroidal saponins in Dioscorea sp., is used as a complementary medicine to treat coronary disease and angina pectoris in China. Although the pharmacological activities and pharmacokinetics of DIS have been well demonstrated, information regarding the final metabolic fates is very limited. This study investigated the in vivo metabolic profiles of DIS after oral administration by ultra‐performance liquid chromatography quadrupole time‐of‐flight mass spectrometry method. The structures of the metabolites were identified and tentatively characterized by means of comparing the molecular mass, retention time and fragmentation pattern of the analytes with those of the parent compound. A total of eight metabolites, including seven phase I and one phase II metabolites, were detected and tentatively identified for the first time. Oxidation, deglycosylation and glucuronidation were found to be the major metabolic processes of the compound in rats. In addition, a possible metabolic pathway on the biotransformation of DIS in vivo was proposed. This study provides valuable and new information on the metabolism of DIS, which will be helpful for further understanding its mechanism of action. Copyright © 2015 John Wiley & Sons, Ltd.  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-23

京公网安备 11010802026262号