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   662857篇
  免费   7988篇
  国内免费   1990篇
化学   344925篇
晶体学   9948篇
力学   30634篇
综合类   20篇
数学   82772篇
物理学   204536篇
  2021年   5814篇
  2020年   6369篇
  2019年   6972篇
  2018年   9242篇
  2017年   9289篇
  2016年   13679篇
  2015年   8405篇
  2014年   13261篇
  2013年   31412篇
  2012年   23989篇
  2011年   29286篇
  2010年   21002篇
  2009年   20768篇
  2008年   26627篇
  2007年   26513篇
  2006年   24437篇
  2005年   21556篇
  2004年   20155篇
  2003年   17751篇
  2002年   17750篇
  2001年   20020篇
  2000年   15193篇
  1999年   11942篇
  1998年   9995篇
  1997年   9641篇
  1996年   9196篇
  1995年   8122篇
  1994年   8102篇
  1993年   7813篇
  1992年   8616篇
  1991年   8843篇
  1990年   8467篇
  1989年   8214篇
  1988年   8061篇
  1987年   8038篇
  1986年   7605篇
  1985年   9829篇
  1984年   10027篇
  1983年   8134篇
  1982年   8286篇
  1981年   8040篇
  1980年   7613篇
  1979年   8243篇
  1978年   8364篇
  1977年   8246篇
  1976年   8179篇
  1975年   7685篇
  1974年   7595篇
  1973年   7574篇
  1972年   5397篇
排序方式: 共有10000条查询结果,搜索用时 3 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.
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   
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.
Small molecule additives have been shown to increase the device efficiency of conjugated polymer (donor) and fullerene derivative (acceptor) based organic solar cells by modifying the morphology of the device active layer. In this paper we conduct a systematic study of how additives affect the donor‐acceptor morphology using molecular dynamics simulations of blends of thiophene‐based oligomers, mimicking poly(3‐dodecylthiophene) (P3DDT) or poly(2,2′:5′,2”‐3,3”‐didocyl‐terthiophene) (PTTT), and fullerene derivatives with additives of varying length and chemical functionalization, mimicking experimentally used additives like methyl ester additives, diiodooctane, and alkanedithiols. We find that functionalization of additives with end groups that are attracted to acceptor molecules are necessary to induce increased donor‐acceptor macrophase separation. In blends where acceptors intercalate between oligomer alkyl side chains, functionalized additives decrease acceptor intercalation. Functionalized additives with shorter alkyl segments increase acceptor macrophase separation more than additives with same chemical functionalization but longer alkyl segments. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1046–1057  相似文献   
107.
108.
109.
110.
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