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   87438篇
  免费   1083篇
  国内免费   743篇
化学   30465篇
晶体学   850篇
力学   7128篇
综合类   40篇
数学   33115篇
物理学   17666篇
  2023年   107篇
  2022年   152篇
  2021年   282篇
  2020年   339篇
  2019年   297篇
  2018年   10616篇
  2017年   10419篇
  2016年   6417篇
  2015年   1208篇
  2014年   680篇
  2013年   914篇
  2012年   4465篇
  2011年   11262篇
  2010年   6065篇
  2009年   6468篇
  2008年   7192篇
  2007年   9318篇
  2006年   775篇
  2005年   1811篇
  2004年   1941篇
  2003年   2267篇
  2002年   1295篇
  2001年   420篇
  2000年   402篇
  1999年   281篇
  1998年   265篇
  1997年   225篇
  1996年   293篇
  1995年   187篇
  1994年   171篇
  1993年   171篇
  1992年   133篇
  1991年   112篇
  1990年   109篇
  1989年   99篇
  1988年   92篇
  1987年   87篇
  1986年   86篇
  1985年   103篇
  1984年   104篇
  1983年   66篇
  1982年   94篇
  1981年   78篇
  1980年   82篇
  1979年   101篇
  1978年   77篇
  1977年   53篇
  1976年   53篇
  1975年   47篇
  1973年   47篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
11.
12.
13.
14.
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   
15.
16.
The structure and properties of 12Cr1MoV steel irradiated with a zirconium ion beam were studied by optical microscopy, scanning electron microscopy, and micro- and nanoindentation. It is shown that the modification covers the entire cross-section of the irradiated specimens to a depth of 1 mm. The data on irradiation-induced structural changes are used to interpret the changes in mechanical properties of the irradiated specimens under static and cyclic loading. Particular attention is given to analysis of strain estimation by the digital image correlation method.  相似文献   
17.
Ni–Co alloys have a wide range of applications in various fields owning to their excellent physical, chemical, and mechanical properties. In this paper, we prepare Ni–Co alloy coatings on 316L stain steel surfaces by electroplating. We present a novel approach utilizing a nanosecond laser to induce microtextures on Ni–Co alloy coatings. We study experimentally the effects of laser power and scanning rate on the surface morphologies of Ni–Co alloy coatings. The results indicate that the shape and size of induced microtextures can be controlled by the laser power and scanning rate. The size of grains increases with increase in the work current of the laser (WCL) at a certain scanning rate. With the WCL constant, the size of grains decreases with increase in scanning rate while their average height increases. It is a simple and easily-controlled method for the fabrication of microstructures on Ni–Co alloy coatings, which has promising applications in investigations of the properties of microtextured surfaces, such as friction, adhesion, and wetting.  相似文献   
18.
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   
19.
20.
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