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   105419篇
  免费   4420篇
  国内免费   3073篇
化学   43365篇
晶体学   1034篇
力学   8452篇
综合类   279篇
数学   34937篇
物理学   24845篇
  2024年   72篇
  2023年   571篇
  2022年   549篇
  2021年   857篇
  2020年   1116篇
  2019年   1067篇
  2018年   11063篇
  2017年   10825篇
  2016年   7159篇
  2015年   1999篇
  2014年   1764篇
  2013年   2280篇
  2012年   6241篇
  2011年   12934篇
  2010年   7190篇
  2009年   7553篇
  2008年   8240篇
  2007年   10263篇
  2006年   1689篇
  2005年   2493篇
  2004年   2433篇
  2003年   2722篇
  2002年   1733篇
  2001年   802篇
  2000年   845篇
  1999年   802篇
  1998年   769篇
  1997年   722篇
  1996年   813篇
  1995年   615篇
  1994年   535篇
  1993年   477篇
  1992年   414篇
  1991年   378篇
  1990年   297篇
  1989年   260篇
  1988年   216篇
  1987年   192篇
  1986年   182篇
  1985年   164篇
  1984年   130篇
  1983年   96篇
  1982年   82篇
  1981年   74篇
  1980年   63篇
  1979年   60篇
  1978年   53篇
  1975年   44篇
  1914年   45篇
  1909年   41篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
32.
A green and sustainable strategy synthesizes clinical medicine warfarin anticoagulant by using lipase‐supported metal–organic framework (MOF) bioreactors (see scheme). These findings may be beneficial for future studies in the industrial production of chemical, pharmaceutical, and agrochemical precursors.  相似文献   
33.
Mass spectrometry (MS) driven metabolomics is a frequently used tool in various areas of life sciences; however, the analysis of polar metabolites is less commonly included. In general, metabolomic analyses lead to the detection of the total amount of all covered metabolites. This is currently a major limitation with respect to metabolites showing high turnover rates, but no changes in their concentration. Such metabolites and pathways could be crucial metabolic nodes (e.g., potential drug targets in cancer metabolism). A stable-isotope tracing capillary electrophoresis–mass spectrometry (CE-MS) metabolomic approach was developed to cover both polar metabolites and isotopologues in a non-targeted way. An in-house developed software enables high throughput processing of complex multidimensional data. The practicability is demonstrated analyzing [U-13C]-glucose exposed prostate cancer and non-cancer cells. This CE-MS-driven analytical strategy complements polar metabolite profiles through isotopologue labeling patterns, thereby improving not only the metabolomic coverage, but also the understanding of metabolism.  相似文献   
34.
Huang  Jian  Cen  Zhongdi  Xu  Aimin  Liu  Li-Bin 《Numerical Algorithms》2020,83(2):549-563
Numerical Algorithms - A singularly perturbed Volterra integro-differential equation with an integrable singularity in the integral term is considered. The upwind difference method is used to...  相似文献   
35.
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   
36.
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   
37.
38.
39.
40.
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