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   439篇
  免费   21篇
化学   363篇
晶体学   3篇
力学   3篇
数学   20篇
物理学   71篇
  2021年   4篇
  2020年   6篇
  2019年   12篇
  2018年   3篇
  2017年   3篇
  2016年   12篇
  2015年   11篇
  2014年   7篇
  2013年   13篇
  2012年   24篇
  2011年   17篇
  2010年   9篇
  2009年   8篇
  2008年   16篇
  2007年   16篇
  2006年   27篇
  2005年   14篇
  2004年   14篇
  2003年   10篇
  2002年   7篇
  2001年   4篇
  2000年   4篇
  1999年   4篇
  1997年   5篇
  1996年   6篇
  1995年   3篇
  1994年   5篇
  1993年   6篇
  1991年   4篇
  1990年   7篇
  1989年   11篇
  1988年   10篇
  1987年   3篇
  1986年   3篇
  1985年   10篇
  1984年   18篇
  1983年   4篇
  1982年   11篇
  1981年   11篇
  1980年   8篇
  1979年   11篇
  1978年   14篇
  1977年   8篇
  1976年   8篇
  1975年   7篇
  1974年   12篇
  1973年   15篇
  1967年   2篇
  1956年   3篇
  1955年   2篇
排序方式: 共有460条查询结果,搜索用时 15 毫秒
71.
Highly fluorinated epoxides were polymerized under mild conditions regioregularly, which gave easy access to isotactic polymers by using optically pure epoxides.  相似文献   
72.
73.

According to one suggested model, bending of a single crystal introduces edge dislocations of the same sign. In the present study, this model is examined by computer simulation using molecular dynamics. When a notch is present on the tension surface, Heidenreich-Shockley partial dislocations are created near the tip of the notch. In the compression surface, partial dislocations are created due to wrinkling of the crystal plane. The results of simulation shows that dislocations are more easily created in a compressive bending region than in a tension bending region or simple tension region.  相似文献   
74.
75.
76.
77.
Many regulatory enzymes are considered attractive therapeutic targets, and their inhibitors are potential drug candidates. Screening combinatorial libraries for enzyme inhibitors is pivotal to identifying hit compounds for the development of drugs targeting regulatory enzymes. Here, we introduce the first inhibitor screening method that consumes only nanoliters of the reactant solutions and is applicable to regulatory enzymes. The method is termed inject-mix-react-separate-and-quantitate (IMReSQ) and includes five steps. First, nanoliter volumes of substrate, candidate inhibitor, and enzyme solutions are injected by pressure into a capillary as separate plugs. Second, the plugs are mixed inside this capillary microreactor by transverse diffusion of laminar flow profiles. Third, the reaction mixture is incubated to form the enzymatic product. Fourth, the product is separated from the substrate inside the capillary by electrophoresis. Fifth, the amounts of the product and substrate are quantitated. In this proof-of-principle work, we applied IMReSQ to study inhibition of recently cloned protein farnesyltransferase from parasite Entamoeba histolytica. This enzyme is a potential therapeutic target for antiparasitic drugs. We identified three previously unknown inhibitors of this enzyme and proved that IMReSQ could be used for quantitatively ranking the potencies of inhibitors.  相似文献   
78.
Skeletal Ni catalysts were prepared from Ni–Zr alloys, which possess different chemical composition and atomic arrangements, by a combination of thermal treatment and treatment with aqueous HF. Hydrogen generation from ammonia borane over the skeletal Ni catalysts proceeded efficiently, whereas the amorphous Ni–Zr alloy was inactive. Skeletal Ni prepared from amorphous Ni30Zr70 alloy had a higher catalytic activity than that prepared from amorphous Ni40Zr60 and Ni50Zr50 alloys. The atomic arrangement of the Ni–Zr alloy also strongly affected the surface structure and catalytic activities. Thermal treatment of the amorphous Ni–Zr alloys at a temperature slightly lower than the crystallization temperature led to an increase of the number of surface‐exposed Ni atoms and an enhancement of the catalytic activities for hydrogen generation from ammonia borane. The skeletal Ni catalysts also showed excellent durability and recyclability.  相似文献   
79.
Photochemical profiles of omega-cleavage of carbon-X (X = Br and Cl) bonds in m-bromo- and m-chloromethylbenzophenones (m-BMBP and m-CMBP) were investigated by laser photolysis techniques and DFT calculations. m-BMBP and m-CMBP were found to undergo omega-bond cleavage to yield the m-benzoylbenzyl radical (m-BBR) at 295 K, and the quantum yields were determined. No CIDEP signal was detected upon 308 nm laser photolysis of both the compounds. From these observations, it was inferred that the omega-bond of these m-halomethylbenzophenones (m-HMBP) cleaves in the lowest excited singlet state (S(1)(n,pi(*))) upon direct excitation. Upon triplet sensitization of acetone (Ac), the m-BBR formation was observed in transient absorption for an Ac-m-BMBP system, and an efficiency of the C-Br bond cleavage in the lowest triplet state (T(1)(n,pi(*))) of m-BMBP was determined. In contrast, formation of triplet m-CMBP was seen for an Ac-m-CMBP system. Absence of C-Cl bond cleavage in the triplet state of m-CMBP indicated the reactive state of m-CMBP for omega-cleavage is only the S(1)(n,pi(*)) state. Based on the efficiencies and DFT calculations for excited state energies, photoinduced omega-bond dissociation of m- and p-HMBPs was characterized.  相似文献   
80.
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