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   824篇
  免费   57篇
  国内免费   71篇
化学   551篇
晶体学   7篇
力学   25篇
综合类   6篇
数学   189篇
物理学   174篇
  2023年   4篇
  2022年   34篇
  2021年   36篇
  2020年   24篇
  2019年   35篇
  2018年   27篇
  2017年   23篇
  2016年   38篇
  2015年   34篇
  2014年   34篇
  2013年   68篇
  2012年   44篇
  2011年   50篇
  2010年   37篇
  2009年   39篇
  2008年   48篇
  2007年   37篇
  2006年   18篇
  2005年   22篇
  2004年   26篇
  2003年   21篇
  2002年   49篇
  2001年   37篇
  2000年   22篇
  1999年   19篇
  1998年   9篇
  1997年   5篇
  1996年   5篇
  1995年   12篇
  1994年   5篇
  1993年   5篇
  1992年   6篇
  1991年   5篇
  1990年   3篇
  1989年   2篇
  1988年   4篇
  1987年   2篇
  1985年   4篇
  1984年   5篇
  1982年   5篇
  1981年   6篇
  1980年   5篇
  1979年   5篇
  1978年   7篇
  1977年   2篇
  1974年   8篇
  1973年   6篇
  1971年   1篇
  1970年   2篇
  1966年   2篇
排序方式: 共有952条查询结果,搜索用时 15 毫秒
91.
Ouyang C  Shum P  Wu K  Wong JH  Lam HQ  Aditya S 《Optics letters》2011,36(11):2089-2091
We present an all-fiber bidirectional passively mode-locked soliton laser with what we believe is a novel cavity configuration. Using a four-port circulator, we incorporate two different semiconductor saturable absorber mirrors (SESAMs) into the laser cavity, which enables bidirectional mode locking. The laser allows the generation of two independent countercirculating mode-locked pulse trains, each with an individual fundamental repetition rate that can be adjusted by varying the SESAM pigtail length. Two countercirculating pulse trains with repetition rates of 21.3 and 15.2 MHz are obtained simultaneously. By controlling the intracavity loss imposed on these two pulse trains, either one of the two pulse trains can be switched on or off. The bidirectional operation with other repetition rates is also demonstrated.  相似文献   
92.
93.
A molecular dynamic method in conjunction with a statistic test has been utilized to model chiral recognition of a -phenylethylamine on heptakis (2,6-di-O-butyl-3-O-butyryl)-b -cyclodextrin in gas chromatography. The modelling data correlated with the chromatographic elution order, and indicated that the preferred site of a -phenylethylamine is the interior of cavity.  相似文献   
94.
Magnetic bunch compressor is one of the key technologies on the path to next generation accelerator driven facilities. In this paper we report the design principles and the first experimental research of the bunch compressor developed at Chinese Academy of Engineering Physics (CAEP). The length of the bunch after compressor is found to be about 0.7 ps (rms) and the peak current exceeds 500 A when operated in the optimized condition. The sensitivity of the bunch length on the phase of the acceleration field and magnetic field of the bunch compressor was also measured and analyzed.  相似文献   
95.
96.
New triphenylamine derivatives 1, 2, 3, and 4 were synthesized and characterized by IR, FAB‐MS, EPR and EA. All of them displayed similar absorption and fluorescence spectra except compound 1, for which a possible explanation was proposed. Quasi‐reversible oxidation waves at about 0.76 V (vs. SCE) and 1.1 V for nitronyl nitroxide and iminyl nitroxide respectively as well as irreversible one at about 1.5 V for triphenylamine group were detected with cyclic voltammetry for compounds 1, 2, 3 and 4. Crystal structures of 2 and 4 were determined by X‐ray diffraction analysis. Their crystal data are as follows: for 2: monoclinic, C2/c, a = 1.69914 (4), b = 1.37435(5), c = 1.24621(5) ran, β= 106.553(2)°, V = 2.7896(2) nm3 Z = 4; for 4: orthorhombic, Pbca, a = 1.95970(6), b = 1.33096(4), c = 4.84691(14) nm, V = 12.6421(7) nm3, Z = 8. Magnetic studies indicated that all of them showed antiferromagnetic properties in solid state, but with strong intermolecular spin‐spin coupling as indicated by the relatively large values of 6, in particular for 4 (θ = ?12 K). Possible spin‐spin interaction mechanism was suggested based on the crystal structures of 2 and 4.  相似文献   
97.
用毛细管离子分析 (CIA)法 ,采用 10mmol·L- 1咪唑为背景电解质 ,4 0 %甲醇为选择性改性剂 ,在 pH 2 .5、分离电压为 2 5kV、柱温为 2 2℃的电泳条件下 ,采用间接紫外检测 (2 14nm ) ,在5min内测定了人发中铝 ,方法简便、快速、灵敏度高、重现性好、测定成本低  相似文献   
98.
99.
100.
We propose a Raman spectroscopy technique which is able to probe the one-particle Green function, the Fermi surface, and the quasiparticles of a gas of strongly interacting ultracold atoms. We give quantitative examples of experimentally accessible spectra. The efficiency of the method is validated by means of simulated images for the case of a usual Fermi liquid as well as for more exotic states: specific signatures of, e.g., a d-wave pseudogap are clearly visible.  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