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   290700篇
  免费   2079篇
  国内免费   1000篇
化学   140982篇
晶体学   4016篇
力学   14953篇
综合类   6篇
数学   54509篇
物理学   79313篇
  2020年   1970篇
  2019年   2264篇
  2018年   13389篇
  2017年   13158篇
  2016年   10186篇
  2015年   3181篇
  2014年   4085篇
  2013年   9529篇
  2012年   10523篇
  2011年   18605篇
  2010年   11533篇
  2009年   11789篇
  2008年   14501篇
  2007年   16665篇
  2006年   7806篇
  2005年   8160篇
  2004年   7626篇
  2003年   7535篇
  2002年   6467篇
  2001年   6165篇
  2000年   4949篇
  1999年   3596篇
  1998年   3179篇
  1997年   3168篇
  1996年   3005篇
  1995年   2432篇
  1994年   2495篇
  1993年   2542篇
  1992年   2647篇
  1991年   2719篇
  1990年   2609篇
  1989年   2593篇
  1988年   2519篇
  1987年   2490篇
  1986年   2414篇
  1985年   3084篇
  1984年   3237篇
  1983年   2595篇
  1982年   2866篇
  1981年   2740篇
  1980年   2547篇
  1979年   2761篇
  1978年   2866篇
  1977年   2874篇
  1976年   2847篇
  1975年   2703篇
  1974年   2677篇
  1973年   2835篇
  1972年   1892篇
  1967年   1840篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
An estimate of the factors which influence the rate of growth of filamentary silicon crystals in a standard chloride system using a quartz reactor with hot walls is given. It is shown that a diffusion form of crystallization is observed under the conditions investigated.Voronezh State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 22–26, October, 1995.  相似文献   
82.
Nonperturbative nolocal structure of QCD vacuum is well described by instanton model. Specific helicity and flavor structure of zero modes of quarks, in instanton field allows simultaneously to explain some important features of low-and high-energy hadron phenomemology. The basic characteristics of hadron spectrum, partonic sum rules, heavyquark potential etc within the instanton liquid model are briefly discussed.  相似文献   
83.
The microhardness and content of carbon in electroplated gold coatings were studied as influenced by the operation time of citrate and citrate-phosphate gold-plating electrolytes. Such physicomechanical properties as porosity, microhardness, internal stress, plasticity, and microstructure of electroless-plated and electroplated nickel coatings were studied and analyzed.  相似文献   
84.
A forecasting model is developed for the number of daily applications for loans at a financial services telephone call centre. The purpose of the forecasts and the associated prediction intervals is to provide effective staffing policies within the call centre. The model building process is constrained by the availability of only 2 years and 7 months of data. The distinctive feature of the data is that demand is driven in the main by advertising. The analysis given focuses on applications stimulated by press advertising. Unlike previous analyses of broadly similar data, where ARIMA models were used, a model with a dynamic level, multiplicative calendar effects and a multiplicative advertising response is developed and shown to be effective.  相似文献   
85.
86.
87.
A convenient method is proposed for the synthesis of all the individual methyl ethers of methyl 2-acetamido-2-deoxy-α-D-glucopyranoside based on the partial methylation of 2-acetamido-2-deoxy-α-D-glucopyranoside with dimethyl sulfate in an alkaline medium followed by preparative liquid column chromatography on silica gel of the resulting mixture of methyl ethers.  相似文献   
88.
A test for a function to be a solution of an elliptic PDE is given in terms of extensions, as solutions, from the boundaries inside the domains belonging to an isotopic family. It generalizes a result of Ehrenpreis for spheres moved along a straight line.

  相似文献   

89.
The feasibility of an 84 GHz, 500 kW, CW gyrotron for ECRH on an experimental tokamak will be presented in this paper. Mode competition and mode selection procedures are carefully investigated by considering various candidate modes and the TE10,4 mode is chosen as the operating mode. A conventional cylindrical cavity resonator with weak input and output tapers and parabolic roundings is considered for interaction studies. Self-consistent, both single mode and time-dependent, calculations are carried out and power and efficiencies are computed for a typical set of beam parameters. The results show that an output power of well over 500 kW, CW and efficiency around 40% can be reached without a depressed collector.  相似文献   
90.
The mass power spectrum for a Universe dominated by the Chaplygin gas is evaluated numerically from scales of the order of the Hubble horizon to 100 Mpc. The results are compared with a pure baryonic Universe and a cosmological constant model. In all three cases, the spectrum increases with k, the wavenumber of the perturbations. The slope of the spectrum is higher for the baryonic model and smaller for the cosmological constant model, the Chaplygin gas interpolating these two models. The results are analyzed in terms of the sound velocity of the Chaplygin gas and the moment the Universe begins to accelerate.  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