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   705篇
  免费   43篇
  国内免费   6篇
化学   588篇
晶体学   6篇
力学   28篇
数学   22篇
物理学   110篇
  2023年   9篇
  2022年   22篇
  2021年   14篇
  2020年   34篇
  2019年   22篇
  2018年   26篇
  2017年   30篇
  2016年   36篇
  2015年   29篇
  2014年   31篇
  2013年   60篇
  2012年   74篇
  2011年   48篇
  2010年   45篇
  2009年   30篇
  2008年   59篇
  2007年   33篇
  2006年   27篇
  2005年   18篇
  2004年   12篇
  2003年   6篇
  2002年   8篇
  2000年   2篇
  1999年   3篇
  1998年   7篇
  1997年   4篇
  1996年   6篇
  1995年   2篇
  1994年   4篇
  1992年   3篇
  1991年   5篇
  1990年   4篇
  1989年   2篇
  1988年   1篇
  1986年   1篇
  1985年   2篇
  1984年   7篇
  1983年   1篇
  1981年   2篇
  1980年   3篇
  1979年   5篇
  1977年   5篇
  1976年   1篇
  1975年   1篇
  1974年   2篇
  1972年   1篇
  1970年   1篇
  1969年   1篇
  1968年   2篇
  1947年   1篇
排序方式: 共有754条查询结果,搜索用时 20 毫秒
51.
52.
Laboratory formation of four isomers of C5H2 molecule is reported and detection of the ring-chain isomer (isomer 1) of C5H2 in cosmic objects has been suggested. For identification of a molecule in cosmic objects, one of the required input data is EinsteinA-coefficients (radiative transition probabilities) for the molecule. Here, we report EinsteinA-coefficients for electric dipole transitions in the ring-chain isomer of C5H2 among the rotational levels of the ground electronic and ground vibrational states up to 21 cm−1.  相似文献   
53.
An external electric field induced reversible modulation of a room temperature magnetic moment and coercive field is achieved in an epitaxial and insulating thin film of dilutely cobalt-doped anatase TiO2. This first demonstration of an electric field effect in any oxide-based diluted ferromagnet is realized in a high quality epitaxial heterostructure of PbZr(0.2)Ti(0.8)O(3)/Co: TiO(2)/SrRuO(3) grown on (001) LaAlO3. The observed effect, which is about 15% in strength in a given heterostructure, can be modulated over several cycles. Possible mechanisms for electric field induced modulation of insulating ferromagnetism are discussed.  相似文献   
54.
JPC – Journal of Planar Chromatography – Modern TLC - Sensitive and selective detection of monocrotophos after TLC is possible by use of vanillin as reagent. The product from alkaline...  相似文献   
55.
In real catalyst systems, it is difficult to establish a correlation between catalytic properties and the shape (crystal planes, corners and steps) of the active catalytic particles. In this paper we present a clear shape dependence of the catalytic properties of a Vulcan‐supported fuel cell catalyst having 4 nm cubo‐octahedral platinum(0) nanocrystallites with (111) and (100) surfaces stabilized by sodium polyacrylate. The electrode materials were characterized by CO‐stripping cyclic voltammetry and transmission electron microscopy (TEM), showing that no agglomeration had occurred among the nanoparticles on the catalyst surfaces. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
56.
JPC – Journal of Planar Chromatography – Modern TLC - Cypermethrin is frequently encountered in poisoning cases in India. In TLC, the compound can be detected by spraying the plate with...  相似文献   
57.
Catalyst-free alcoholytic deprotection of borane-protected phosphorus compounds offers a smooth, efficient, and clean alternative to existing deprotection methods. In this paper we report our results on the general applicability of deprotecting phosphane- and phosphite-borane adducts by means of simple alcoholysis without the use of molecular sieves as a catalyst. Phosphane-boranes bearing at least one aromatic substituent are readily deprotected in high yields. Borane complexes of trialkylphosphanes or phosphites, however, cannot be deprotected in this way. The main merit of our method is its simplicity: apart from evaporation of the solvent, no further work-up or purification is needed.  相似文献   
58.
A highly sensitive and selective on‐line two‐dimensional reversed‐phase liquid chromatography/electrospray ionization–tandem mass spectrometry (2D‐LC‐ESI/MS/MS) method was developed and validated to determine rifaximin in rat serum by direct injection. The 2D‐LC‐ESI/MS/MS system consisted of a restricted access media column for trapping proteins as the first dimension and a Waters C18 column as second dimension using 0.1% aqueous acetic acid:acetonitrile as mobile phase in a gradient elution mode. Rifampacin was used as an internal standard. The linear dynamic range was 0.5–10 ng/mL (r2 > 0.998). Acceptable precision and accuracy were obtained over the calibration range. The assay was successfully used in analysis of rat serum to support pharmacokinetic studies. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
59.
60.
Summary. 2,4,5-Triaryl-1H-imidazoles were efficiently synthesized from benzoin or benzil, ammonium acetate, and aromatic or heteroaromatic aldehydes in the presence of sodium bisulfite as catalyst. The present protocol offers significant improvements for the synthesis of 2,4,5-triaryl-1H-imidazoles with regard to yield of products, simplicity in operation, and cheap catalyst.  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