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   353135篇
  免费   6940篇
  国内免费   5408篇
化学   170941篇
晶体学   5067篇
力学   21240篇
综合类   332篇
数学   63487篇
物理学   104416篇
  2022年   2848篇
  2021年   3774篇
  2020年   3995篇
  2019年   4662篇
  2018年   15872篇
  2017年   15545篇
  2016年   13328篇
  2015年   5241篇
  2014年   7431篇
  2013年   12915篇
  2012年   14694篇
  2011年   22480篇
  2010年   15294篇
  2009年   15802篇
  2008年   17504篇
  2007年   19265篇
  2006年   9947篇
  2005年   9838篇
  2004年   9482篇
  2003年   9142篇
  2002年   8327篇
  2001年   7810篇
  2000年   5988篇
  1999年   4551篇
  1998年   4116篇
  1997年   3899篇
  1996年   3736篇
  1995年   3197篇
  1994年   3328篇
  1993年   3192篇
  1992年   3395篇
  1991年   3534篇
  1990年   3460篇
  1989年   3431篇
  1988年   3239篇
  1987年   3225篇
  1986年   3086篇
  1985年   3697篇
  1984年   3762篇
  1983年   3187篇
  1982年   3133篇
  1981年   3011篇
  1980年   2826篇
  1979年   3280篇
  1978年   3251篇
  1977年   3409篇
  1976年   3497篇
  1975年   3202篇
  1974年   3162篇
  1973年   3310篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
成功地在六路高功率Nd玻璃激光装置上建立了2660紫外激光探针和适合紫外波段的Normaski干涉仪,首次将可见波长的连续激光应用于紫外干涉仪中靶成像调整和光路准直。利用该紫外光干涉仪,在铜柱状靶(φ500μm)上测量了厚等离子体中高达0.6n。的电子密度。  相似文献   
72.
Courses which teach discrete-event simulation are based on many different simulation languages. The requirements for a language to support teaching simulation are discussed. In particular, it is recommended that such languages separate into distinct modules those aspects of simulation which are taught as separate topics. Implementation of the separation is discussed. The SEESIM language, developed as a teaching aid, is described, and examples of its use are given. Straightforward use of SEESIM can be learned quickly, yet the language provides facilities for a staged introduction to advanced concepts of simulation.  相似文献   
73.
Yu V Sharvin 《Pramana》1987,28(5):592-592
Investigation of the galvanomagnetic properties of disordered metals in weak magnetic fields [r(H)?l, wherer(H) is the electron trajectory radius andl, the electron free path], proved to be one of the effective experimental methods of studying disordered metals. The phase difference between the interfering electron waves is affected by the presence of magnetic flux in the sample. One of the observable effects is the oscillatory magnetoresistanceK(H) of multiconnected samples predicted by Altshuleret al (1981). The period ofK(H) oscillations for the hollow cylinders, networks or chains with orifices cross-sections areasS isΔH=φ 0/2S [whereφ 0=hc/e]. The amplitude and the phase of the oscillations depend on the spin orbit interaction, the intensity of superconductive fluctuation etc. It should be noted that in small “mesoscopic” single loops the oscillations with the periodΔH?φ 0/S were also observed recently (see also Altshuleret al 1987 included in this issue).  相似文献   
74.
75.
We demonstrate a method that permits to obtain generalized solutions for some quasilinear equations and systems of hyperbolic type. The corresponding variational principle is constructed using the theory of equilibrium of a potential in an external field. Dedicated to the memory of B. M. Levitan Supported by RFBR grants Nos. 05-01-00522 and NSh-1551.2003.1, by Program No. 1 of the Branch of Mathematics, Russian Academy of Sciences, and by INTAS project No. 03-51-6637.  相似文献   
76.
Renormalization formulas connecting the points of the orbits O 0 ± , i.e., the sequences generated by an irrational shift on the half-open interval [0, 1) or (0, 1], and the points of the orbits' derivatives dmO 0 ± , i.e., the sequences obtained by restricting O 0 ± to half-open intervals of smaller length, are obtained. Bibliography: 5 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 314, 2004, pp. 142–154.  相似文献   
77.
The enthalpies of reactions of La2CoO4(cr) and CoCl2(cr) with hydrochloric acid were measured with an isothermal-jacket calorimeter. The results obtained and the available literature data were used to calculate the standard enthalpy of formation of La2CoO4(cr) at 298.15 K, Δf H o = ?2179 ± 7 kJ/mol.  相似文献   
78.
79.
We consider generalizations of the earlier results, obtained for one-dimensional equations of the Kadomtsev–Petviashvili (KP) class, to two- and three-dimensional KP-class equations with an arbitrary nonlinearity index with allowance for the higher-order dispersion correction and terms describing dissipation and instability. The asymptotics of soliton and nonsoliton solutions are derived. Constructing phase portraits in the 8-dimensional space based on the results of a qualitative analysis of generalized Korteweg–de Vries (KdV) equations is discussed.  相似文献   
80.
A noiselike fine structure of ferromagnetic resonance spectra in magnetic powders was investigated after ultrasonic treatment. Magnetic interactions between particles are proved to have an influence upon the fine structure formation. After decreasing dipole-dipole magnetic interactions in dilute suspension a special order appears in fine-structure spectra, which is generally the same for different systems.  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