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   367860篇
  免费   4004篇
  国内免费   1015篇
化学   178214篇
晶体学   4459篇
力学   17418篇
综合类   7篇
数学   56399篇
物理学   116382篇
  2020年   2195篇
  2019年   2369篇
  2018年   11373篇
  2017年   12180篇
  2016年   8710篇
  2015年   4173篇
  2014年   4830篇
  2013年   12960篇
  2012年   13781篇
  2011年   23678篇
  2010年   14616篇
  2009年   14393篇
  2008年   20730篇
  2007年   24149篇
  2006年   9888篇
  2005年   15803篇
  2004年   11429篇
  2003年   10341篇
  2002年   8235篇
  2001年   7985篇
  2000年   6197篇
  1999年   4645篇
  1998年   3915篇
  1997年   3846篇
  1996年   3561篇
  1995年   3517篇
  1994年   3374篇
  1993年   3422篇
  1992年   3760篇
  1991年   3600篇
  1990年   3428篇
  1989年   3378篇
  1988年   3433篇
  1987年   3298篇
  1986年   3164篇
  1985年   4412篇
  1984年   4567篇
  1983年   3741篇
  1982年   4108篇
  1981年   3997篇
  1980年   3878篇
  1979年   3924篇
  1978年   4145篇
  1977年   3900篇
  1976年   4120篇
  1975年   3690篇
  1974年   3817篇
  1973年   4101篇
  1972年   2468篇
  1971年   1925篇
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
101.
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   
102.
103.
104.
Acetyl‐l ‐carnitine (ALCAR) is a potential biomarker for the modulation of brain neurotransmitter activity, but is also present in cerebrospinal fluid (CSF). Recent studies have utilized hydrophilic interaction liquid chromatography–tandem mass spectrometry (HILIC‐MS/MS) based assays to detect and quantify ALCAR within biofluids such as urine, plasma and serum, using various sample pretreatment procedures. In order to address the need to quantify ALCAR in CSF on a high‐throughput scale, a new and simple HILIC‐MS/MS assay has been successfully developed and validated. For rapid analysis, CSF sample pretreatment was performed via ‘dilute and shoot’ directly onto an advanced HILIC column prior to MS/MS detection. This newly developed HILIC‐MS/MS assay shows good recoveries of ALCAR without the need for chemical derivatization and multistep sample extraction procedures. The employment of this assay is suitable for the high‐throughput bioanalysis and quantification of ALCAR within the CSF of various animal models and human clinical studies. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
105.
106.
Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO2/N2 selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557  相似文献   
107.
Russian Journal of Organic Chemistry - The Reformatsky reaction of (3R,4R)-4-acetoxy-3-((1R)-1-{[tert-butyl(dimethyl)silyl]oxy}ethyl)­azetidin-2-one with ethyl 4-bromo-3-oxopentanoate gave...  相似文献   
108.
109.
Journal of Thermal Analysis and Calorimetry - The operating temperature of Li-ion batteries used in modern electric vehicles should be maintained within an allowable range to avoid thermal runaway...  相似文献   
110.
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