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   221498篇
  免费   11701篇
  国内免费   3522篇
化学   135318篇
晶体学   2976篇
力学   10321篇
综合类   215篇
数学   24000篇
物理学   63891篇
  2021年   2073篇
  2020年   3285篇
  2019年   5086篇
  2018年   4614篇
  2017年   4398篇
  2016年   7736篇
  2015年   5640篇
  2014年   7352篇
  2013年   11590篇
  2012年   9108篇
  2011年   9478篇
  2010年   8993篇
  2009年   9068篇
  2008年   9369篇
  2007年   8732篇
  2006年   7707篇
  2005年   7066篇
  2004年   6639篇
  2003年   6047篇
  2002年   6865篇
  2001年   6642篇
  2000年   5172篇
  1999年   3361篇
  1998年   2791篇
  1997年   2603篇
  1996年   2374篇
  1995年   2148篇
  1994年   2095篇
  1993年   2112篇
  1992年   2140篇
  1991年   2446篇
  1990年   2366篇
  1989年   2413篇
  1988年   2301篇
  1987年   2326篇
  1986年   2148篇
  1985年   2695篇
  1984年   2689篇
  1983年   2334篇
  1982年   2379篇
  1981年   2290篇
  1980年   2082篇
  1979年   2399篇
  1978年   2537篇
  1977年   2638篇
  1976年   2710篇
  1975年   2521篇
  1974年   2459篇
  1973年   2631篇
  1972年   2140篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
991.
A mathematical model of the system composed of two sensors, the semicircular canal and the sacculus, is suggested. The model is described by three lines of blocks, each line of which has the following structure: a biomechanical block, a mechanoelectrical transduction mechanism, and a block describing the hair cell ionic currents and membrane potential dynamics. The response of this system to various stimuli (head rotation under gravity and falling) is investigated. Identification of the model parameters was done with the experimental data obtained for the axolotl (Ambystoma tigrinum) at the Institute of Physiology, Autonomous University of Puebla, Mexico. Comparative analysis of the semicircular canal and sacculus membrane potentials is presented. __________ Translated from Fundamentalnaya i Prikladnaya Matematika, Vol. 11, No. 7, pp. 207–220, 2005.  相似文献   
992.
Single-particle matrix elements of nucleon transfer were calculated by the Woods-Saxon potential wave functions. The results are compared with the ones calculated by the spherical-well approximation. The eligibility of the approximation of the mean field of nuclei by the spherical well to study the initial stage of nuclear reactions at heavy-ion collisions is demonstrated. The text was submitted by the authors in English.  相似文献   
993.
Methods for solving the Cauchy problem are suggested. The use nonpolynomial splines, which ensure the required accuracy for a rather wide class of functions. Computational results are presented.  相似文献   
994.
995.
996.
In this work, charge-carrier capture by an array of self-assembled InAs/GaAs quantum dots was directly observed for the first time by capacitance recharge. It is proposed to process the obtained transient-capture data by a similar method to that used for emission, by the box-car method. The capture activation energies are determined and compared with the emission activation energies.  相似文献   
997.
Distortions induced by an external magnetic field in the magnetic structure of a thin layer of a uniaxial collinear antiferromagnet with rough surfaces are studied using computer simulation. It is shown that, under certain conditions, the presence of atomic steps at the layer surfaces causes the antiferromagnetic layer to break up into domains. The character and magnitude of distortions are found for an arbitrary ratio of the distance between atomic steps to the order parameter correlation length. Original Russian Text ? A.I. Morosov, I.A. Morosov, A.S. Sigov, 2007, published in Fizika Tverdogo Tela, 2007, Vol. 49, No. 7, pp. 1228–1235.  相似文献   
998.
999.
1000.
All electronic devices are plagued with 1/f noise originating from many causes. The most important factors contributing to 1/f noise in a semiconductor is believed to be recombination of carriers and their trapping at defects and impurity sites. Adsorption of moisture and electron acceptor molecules enhances the intensity of 1/f noise. Amazingly, some molecular species that strongly chelate to the semiconductor surface, suppress 1/f noise owing to passivation of the recombination sites. Thus in addition to sensitization, the dye adsorbed on the nanocrystallites plays a key role in mitigation of recombinations. For this reason dye-sensitized heterojunctions could also find application as low noise NIR photon detectors. Experiments conducted with oxide semiconductors (TiO2, ZnO, SnO2) indicate that the mode of binding of dyes at specific sites determines the extent to which the recombination and 1/f noise are suppressed. The transport of electrons in a nanocrystalline matrix is diffusive with a diffusion coefficient D depending on the trapping and detrapping processes. Thus passivation of trapping sites by the adsorbed dye is expected to increase the response time which can be expressed as τ  L2/D, where L = thickness of the nanocrystalline film. Measurement techniques and construction of a dye-sensitized NIR photon detector will be discussed.  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