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   14828篇
  免费   4232篇
  国内免费   1166篇
化学   3806篇
晶体学   318篇
力学   1011篇
综合类   102篇
数学   991篇
物理学   13998篇
  2024年   18篇
  2023年   81篇
  2022年   220篇
  2021年   265篇
  2020年   285篇
  2019年   225篇
  2018年   263篇
  2017年   419篇
  2016年   511篇
  2015年   433篇
  2014年   830篇
  2013年   964篇
  2012年   943篇
  2011年   1191篇
  2010年   844篇
  2009年   1023篇
  2008年   1136篇
  2007年   1232篇
  2006年   1058篇
  2005年   947篇
  2004年   932篇
  2003年   736篇
  2002年   752篇
  2001年   607篇
  2000年   622篇
  1999年   573篇
  1998年   459篇
  1997年   419篇
  1996年   360篇
  1995年   315篇
  1994年   262篇
  1993年   225篇
  1992年   239篇
  1991年   167篇
  1990年   129篇
  1989年   106篇
  1988年   82篇
  1987年   81篇
  1986年   52篇
  1985年   28篇
  1984年   36篇
  1983年   13篇
  1982年   21篇
  1981年   31篇
  1980年   13篇
  1979年   23篇
  1978年   12篇
  1977年   7篇
  1976年   10篇
  1973年   13篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
961.
962.
This paper describes the dynamics of a water-in-oil microemulsion from the dilute to the dense droplet region. Using the relative intermediate form factor method for neutron spin echo data analyses [M. Nagao, H. Seto, Phys. Rev. E 78 (2008) 011507], the shape and structure fluctuations of a droplet microemulsion are successfully decoupled. In the previous paper, we used the first cumulant analysis of the shape fluctuation model, while the full fitting form of the same model is applied in this paper. The final results of the fittings using the first cumulant approximation and the full form of the model are almost identical, and therefore, the validity of the method is strengthened. The estimated bending modulus of the surfactant membrane, κ, is basically the same, within the experimental errors, in the previous and present results. The κ is not affected much by an increase of the droplet concentration. A clear dynamic slowing down of the water droplets is highlighted at the length scale corresponding to the inter-droplet distance from the structure fluctuation analysis.  相似文献   
963.
The quantized states in a quantum-well semiconductor laser are simulated analytically by a magnetic field perpendicular to the well (infinite quasi-one-dimensional potential well) by deriving a close relationship for the magnetic-field strength which becomes a discrete quantity.  相似文献   
964.
A new kind of four-mode continuous variable coherent-entangled state is proposed in the Fock space by using the technique of integration within an ordered product,which exhibits both the properties of a coherent state and an entangled state,and spans a complete and orthonormal representation.The conjugate state of the four-mode continuous variable coherent-entangled state is derived by using the Fourier transformation.Moreover,a simple experimental protocol of generating a four-mode continuous variable coherent-entangled state is proposed by using beam splitters.As applications of this four-mode continuous variable coherent-entangled state,a four-mode entangled state and a four-mode squeezing-Fresnel operator are constructed.  相似文献   
965.
研究了脉冲HF激光与水柱表面相互作用下电信号的产生过程。电信号显示了与激光能量线性相关的峰值间有时间间隔的两峰结构,且第二个尖峰在水柱底部的蒸汽腔塌缩后出现。实验还显示电信号的幅值和激光脉冲照射过程中是否存在膨胀和挤压的薄水层密切相关。如果在电池上边缘和石英平板(石英板紧邻电池,并与水柱上表面相接)之间存在一薄水层,电信号强度会增加10倍。  相似文献   
966.
The incorporation of oxygen atoms in oxide films grown by pulsed laser deposition depends upon the oxygen pressure and laser power density. By carefully controlling these two parameters it is possible to control the oxygen deficiency in the samples, and thus to change their physical properties from insulating and transparent to absorbing and conducting. By using X-ray diffraction, Rutherford backscattering spectroscopy and resistivity measurements, we show that depending upon the oxide materials oxygen deficiency in the films can induce either the growth of stable sub-oxide phases or the formation of nanocomposite films by phase separation. The first case corresponds to oxides with a mixed valency cation like Ti, which leads to the formation of stable, crystalline and highly conductive TiOx sub-oxide phases. The second case is well described by the indium tin oxides (ITO) in which a large oxygen deficiency leads to metallic clusters embedded into a stoichiometric matrix, i.e. nanocomposite films. This phenomenon is due to the fact that sub-oxides of these compounds are not stable and thus the oxygen deficiency induced a phase separation.  相似文献   
967.
A high‐repetition‐rate pump–probe experiment is presented, based on the asynchronous sampling approach. The low‐α mode at the synchrotron ANKA can be used for a time resolution down to the picosecond limit for the time‐domain sampling of the coherent THz emission as well as for hard X‐ray pump–probe experiments, which probe structural dynamics in the condensed phase. It is shown that a synchronization of better than 1 ps is achieved, and examples of phonon dynamics of semiconductors are presented.  相似文献   
968.
Excimer laser emitting at 248 nm is applied to produce microstructures on the surface of aluminum alloy. The surface morphology shows that hotspots and thermal fluidic structures both come to light. Two possible mechanisms of hotspots formation are proposed: near-field diffraction and interference, and extremely fast rapid thermal annealing. And for the formation of thermal fluidic pattern structure, a thin film model is applied.  相似文献   
969.
970.
Covalent bonds are often created by a reaction between chemicals and protein before causing various adverse effects in a cell. Dimethylaminoethyl methacrylate (DMAEMA), which has moderate toxicity, causes skin inflammation and throat irritation. For this study, we investigated a reaction mechanism between myoglobin and (DMAEMA) using a new analytical tool developed at our laboratory: laser spray mass spectrometry technique. It was found that initially DMAEMA was added to the amino group of protein by the Michael addition mechanism; the added DMAEMA was hydrolyzed to methacrylic acid using an autocatalytic system. The results of this study indicate the feasibility of the laser spray technique in analyses of reaction dynamics. Copyright © 2012 John Wiley & Sons, Ltd.  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