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   79123篇
  免费   577篇
  国内免费   117篇
化学   42396篇
晶体学   1267篇
力学   3293篇
综合类   1篇
数学   7992篇
物理学   24868篇
  2022年   666篇
  2021年   910篇
  2020年   1012篇
  2019年   1137篇
  2018年   1612篇
  2017年   1711篇
  2016年   2199篇
  2015年   1076篇
  2014年   1764篇
  2013年   3339篇
  2012年   2988篇
  2011年   3392篇
  2010年   2692篇
  2009年   2683篇
  2008年   3090篇
  2007年   2978篇
  2006年   2851篇
  2005年   2517篇
  2004年   2296篇
  2003年   2136篇
  2002年   2200篇
  2001年   2246篇
  2000年   1636篇
  1999年   1257篇
  1998年   1134篇
  1997年   1042篇
  1996年   924篇
  1995年   853篇
  1994年   828篇
  1993年   822篇
  1992年   880篇
  1991年   937篇
  1990年   883篇
  1989年   908篇
  1988年   821篇
  1987年   772篇
  1986年   740篇
  1985年   870篇
  1984年   967篇
  1983年   821篇
  1982年   837篇
  1981年   747篇
  1980年   703篇
  1979年   769篇
  1978年   890篇
  1977年   914篇
  1976年   808篇
  1975年   774篇
  1974年   790篇
  1973年   760篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Electrochemical separation of lead-silver alloys into the constituents by thin-layer electrolysis in molten electrolytes, with bismuth as metal separator, is studied. It is proposed to determine the extent of component recovery by potentiometry.  相似文献   
32.
The effect of hydrophilic ionic liquids (ILs) on the activity of chloroperoxidase (CPO) was checked through kinetic and stereochemical studies. The possibility to employ this enzyme in synthesis has been demonstrated investigating the chemo- and stereoselectivity of oxidation of phenyl methylsulfide in several citrate buffer-IL mixtures.  相似文献   
33.
The classical Volterra model, equipped with the Faddeev-Takhtajan Poisson bracket provides a lattice version of the Virasoro algebra. The Volterra model being integrable, we can express the dynamical variables in terms of the so-called separated variables. Taking the continuum limit of these formulae, we obtain the Virasoro generators written as determinants of infinite matrices, the elements of which are constructed with a set of points lying on an infinite genus Riemann surface. The coordinates of these points are separated variables for an infinite set of Poisson commuting quantities including L 0. The scaling limit of the eigenvector can also be calculated explicitly, so that the associated Schroedinger equation is in fact exactly solvable.  相似文献   
34.
35.
A convenient method of synthesis of 2-(methoxycarbonylmethylene)-substituted imidazolidines and imidazolidinium bromides, and also of bicyclic diazo compounds has been developed starting from methyl bromopropiolate and ethylenediamine and its derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1205–1208, September, 1991.  相似文献   
36.
We propose a scheme to obtain the distance of two identical atoms placed inside the standing wave field by monitoring the collective resonance fluorescence spectrum emitted by the two particles. We find three different parameter ranges, depending on the distance of the atoms as compared to the transition wavelength. For large interparticle distances, dipole-dipole coupling is negligible, and the main system evolution arises from the interaction with the standing wave field. In the small-distance limit, the dynamics is dominated by the dipole-dipole interaction. Finally, in the intermediate region, a rich interplay of the various couplings arises, which however is lifted for strong driving laser fields. The present measurement procedure allows us to distinguish the three cases. In each of the cases, we show how to determine the distance of the two particles and their respective positions relative to the nodes of the standing wave field with fractional-wavelength precision.  相似文献   
37.
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   
38.
Analytical formulas are derived that describe the dependences of the transition probabilities in vibrational-rotational spectra of XY3-type molecules with C 3v symmetry on the rotational quantum numbers.  相似文献   
39.
We analyze diffusion from a periodic array of hemispherical droplets through a membrane. We find that the multiple sources do not interact strongly, even when the droplets are closely spaced, so that the flux through the membrane appears nearly additive.  相似文献   
40.
We propose a model of coherent-echo signals during the monostatic sounding of the ionosphere. The model is based on the previously obtained radar equation for separate samples of the scattered signal. The dielectric-permittivity perturbation described by a discrete set of spatial harmonics modulated in space and time is used as the scattering irregularities. The model was tested using Irkutsk incoherent-scatter radar data obtained during the coherent-echo observations in July 15 and 16, 2000. The test shows that the model is suitable for describing the observed characteristics of separate sample spectra of the coherent-echo signals. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 49, No. 6, pp. 459–477, June 2006.  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