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   2601篇
  免费   101篇
  国内免费   13篇
化学   1661篇
晶体学   14篇
力学   116篇
数学   420篇
物理学   504篇
  2023年   28篇
  2021年   57篇
  2020年   60篇
  2019年   62篇
  2018年   41篇
  2017年   32篇
  2016年   78篇
  2015年   71篇
  2014年   66篇
  2013年   112篇
  2012年   156篇
  2011年   174篇
  2010年   94篇
  2009年   80篇
  2008年   160篇
  2007年   147篇
  2006年   158篇
  2005年   136篇
  2004年   78篇
  2003年   86篇
  2002年   43篇
  2001年   46篇
  2000年   24篇
  1999年   18篇
  1998年   18篇
  1997年   19篇
  1996年   25篇
  1995年   19篇
  1994年   21篇
  1993年   25篇
  1992年   26篇
  1991年   26篇
  1990年   17篇
  1989年   18篇
  1988年   18篇
  1987年   21篇
  1986年   28篇
  1985年   16篇
  1984年   26篇
  1983年   17篇
  1982年   22篇
  1981年   31篇
  1980年   34篇
  1978年   25篇
  1977年   30篇
  1976年   24篇
  1975年   21篇
  1974年   20篇
  1973年   17篇
  1972年   18篇
排序方式: 共有2715条查询结果,搜索用时 31 毫秒
1.
Annals of Operations Research - We consider the use of the new C-130J-30 aircraft for long distance (strategic) cargo movement. Currently, only large aircraft, the C-5 and the C-17, are identified...  相似文献   
2.
3.
4.
Octahedral titanium(IV) complexes of phenolato hexadentate ligands were developed and showed very high stability for days in water solutions. In vitro cytotoxicity studies showed that, whereas tetrakis(phenolato) systems are generally of low activity presumably due to inaccessibility, smaller bis(phenolato)bis(alkoxo) complexes feature high anticancer activity and accessibility even without formulations, also toward a cisplatin‐resistant cell line. An all‐aliphatic control complex was unstable and inactive. A leading phenolato complex also revealed: 1) high durability in fully aqueous solutions; accordingly, negligible loss of activity after preincubation for three days in medium or in serum; 2) maximal cellular accumulation and induction of apoptosis following 24–48 h of administration; 3) reduced impact on noncancerous fibroblast cells; 4) in vivo efficacy toward lymphoma cells in murine model; 5) high activity in NCI‐60 panel, with average GI50 of 4.6±2 μm . This newly developed family of TiIV complexes is thus of great potential for anticancer therapy.  相似文献   
5.
6.
7.
An asymmetric total synthesis of [13C4]-anatoxin-a ([13C4]- 1 ) has been developed from commercially available ethyl [13C4]-acetoacetate ([13C4]- 15 ). The unique requirements associated with isotope incorporation inspired a new, robust, and highly scalable route, providing access to 0.110 g of this internal standard for use in the detection and precise quantification of anatoxin-a in freshwater. A highlight of the synthesis is a method that leverages a cyclic iminium ion racemization to achieve dynamic kinetic resolution in an enantioselective Morita–Baylis–Hillman (MBH) cyclization.  相似文献   
8.
Polymeric membranes have shown tremendous promise for the separation of CO2 from flue gas streams. However, few systematic studies have been conducted to better understand the impact that chemical functionalities have on membrane-based gas separation performance. To address this gap, we herein describe the synthesis and gas separation performance of a series of vinyl-addition polynorbornenes bearing various CO2-philic functional groups. To facilitate direct comparison between functional groups, each material was designed to maintain a common polymer backbone. Though the incorporation of CO2-philic moieties within a dense polymeric membrane is frequently hypothesized to enhance CO2 solubility, and thereby increase CO2/N2 selectivity, our results demonstrate that the incorporation of CO2-philic groups onto a common polymer backbone do not necessarily result in increased gas separation performance. Experimental and computational results demonstrate that the incorporation of amidoxime groups onto a polynorbornene backbone increase CO2/N2 selectivity, whereas commonly employed ethereal side chains only increased permeability.  相似文献   
9.
Journal of Computer-Aided Molecular Design - The decoupling approach to solvation free energy calculations requires scaling the interactions between the solute and the solution with all...  相似文献   
10.
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