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   584798篇
  免费   4667篇
  国内免费   1299篇
化学   285516篇
晶体学   8294篇
力学   30798篇
综合类   17篇
数学   85008篇
物理学   181131篇
  2021年   5051篇
  2020年   5489篇
  2019年   6237篇
  2018年   13040篇
  2017年   13432篇
  2016年   13911篇
  2015年   6591篇
  2014年   10521篇
  2013年   23567篇
  2012年   20897篇
  2011年   29170篇
  2010年   20582篇
  2009年   20566篇
  2008年   26785篇
  2007年   28908篇
  2006年   18742篇
  2005年   20047篇
  2004年   17204篇
  2003年   16101篇
  2002年   14821篇
  2001年   14827篇
  2000年   11593篇
  1999年   8782篇
  1998年   7625篇
  1997年   7484篇
  1996年   7082篇
  1995年   6352篇
  1994年   6342篇
  1993年   6087篇
  1992年   6440篇
  1991年   6932篇
  1990年   6639篇
  1989年   6559篇
  1988年   6405篇
  1987年   6205篇
  1986年   5950篇
  1985年   7493篇
  1984年   7866篇
  1983年   6611篇
  1982年   6901篇
  1981年   6405篇
  1980年   6087篇
  1979年   6604篇
  1978年   6836篇
  1977年   6654篇
  1976年   6639篇
  1975年   6352篇
  1974年   6172篇
  1973年   6508篇
  1972年   4740篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
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   
72.
Russian Chemical Bulletin - Terminal disaccharide fragment of phenolic glycolipid from Mycobacterium leprae (PGL-I) was synthesized as a glycoside with 4-(2-aminoethoxy)phenyl aglycon. The obtained...  相似文献   
73.
The external photocontrol over peptide folding, by the incorporation of molecular photoswitches into their structure, provides a powerful tool to study biological processes. However, it is limited so far to switches that exhibit only a rather limited geometrical change upon photoisomerization and that show thermal instability of the photoisomer. Here we describe the use of an overcrowded alkene photoswitch to control a model β-hairpin peptide. This photoresponsive unit undergoes a large conformational change and has two thermally stable isomers which has major influence on the secondary structure and the aggregation of the peptide, permitting the phototriggered formation of amyloid-like fibrils.  相似文献   
74.
75.
76.
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   
77.
78.
79.
80.
Influence of the nuclear energy structure, the conditions of fuel burnup, and accumulation of new fissile isotopes from the raw isotopes on the main parameters of a closed fuel cycle is considered. The effects of the breeding ratio, the cooling time of the spent fuel in the external fuel cycle, and the separation of the breeding area and the fissile isotope burning area on the parameters of the fuel cycle are analyzed.  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