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   108959篇
  免费   6733篇
  国内免费   5775篇
化学   63050篇
晶体学   1442篇
力学   6233篇
综合类   386篇
数学   13086篇
物理学   37270篇
  2023年   975篇
  2022年   2069篇
  2021年   2482篇
  2020年   2698篇
  2019年   2883篇
  2018年   3238篇
  2017年   3169篇
  2016年   3944篇
  2015年   2864篇
  2014年   3991篇
  2013年   5646篇
  2012年   5848篇
  2011年   6230篇
  2010年   4846篇
  2009年   4805篇
  2008年   5139篇
  2007年   4742篇
  2006年   4325篇
  2005年   3760篇
  2004年   3373篇
  2003年   2964篇
  2002年   3110篇
  2001年   2736篇
  2000年   2180篇
  1999年   1839篇
  1998年   1706篇
  1997年   1453篇
  1996年   1429篇
  1995年   1207篇
  1994年   1249篇
  1993年   1197篇
  1992年   1148篇
  1991年   1207篇
  1990年   1192篇
  1989年   1097篇
  1988年   957篇
  1987年   950篇
  1986年   901篇
  1985年   951篇
  1984年   934篇
  1983年   835篇
  1982年   812篇
  1979年   804篇
  1978年   817篇
  1977年   807篇
  1976年   922篇
  1975年   815篇
  1974年   844篇
  1973年   849篇
  1972年   754篇
排序方式: 共有10000条查询结果,搜索用时 12 毫秒
61.
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, No. 6, pp. 96–103, November–December, 1992.  相似文献   
62.
The nonstationary Reynolds equation of the theory of gas lubrication is considered. The existence and uniqueness of a solution to the initial-boundary value problem for this equation are established in the case of sufficiently smooth data. Estimates for the solution are obtained for large bearing numbers. Bibliography: 8 titles.  相似文献   
63.
The fluorescence of solid solutions of CdSe/ZnS quantum dots and the organic dye DODCI is investigated. It is shown that nonradiative transfer of electronic excitation energy to dye molecules, which with some probability lose their acceptor properties as a result of photoisomerization or photodegradation, is responsible for a significant increase in the fluorescence intensity of a donor. The degree of polarization of the donor fluorescence attains values exceeding 0.5, which is due to the difference in the fluorescence quantum yields of donors with different orientations of the oscillator with respect to the electric vector of an excitation light wave. A numerical simulation of the experimentally observed dependences is performed.  相似文献   
64.
The initial stage of propagation of a vertical hydraulic fracture in an impermeable or low-permeability stratum is considered within the framework of the pseudo-three-dimensional Perkins-Kern model.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 6, pp. 79–86, November–December, 1995.  相似文献   
65.
S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of the Ukraine. Translated from Prikladnaya Mekhanika, Vol. 31, No. 9, pp. 15–23, September, 1995.  相似文献   
66.
We have measured the concentration dependence of the average magnetic moment per Fe atom Fe(x) in microcrystalline and amorphous Fe-P alloys obtained over a wide concentration range using electrochemical deposition. The model of local magnetic moments has been used to described Fe(x). On the basis of this model the effects of phosphorus on the value Fe are explained in terms of the parameters of the local environment of the Fe atom.  相似文献   
67.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 994–996, July, 1992.  相似文献   
68.
Advantage of use residue from thermal cracking and products of its condensation as components of the mixture for manufacturing mechanically rigid (93%) granulated and ground carbon sorbents with extended volume of micropores (up to 0.27 cm3/cm3), showing enhanced sorption activity (E is up to 25.6 kJ mol?1) and high ability of separation various gas mixtures is demonstrated. As a carrier for medicine preparations these adsorbents show higher performance as compared with industrial samples. Solutions of the cracking residue can be used for impregnation of worked out zeolites for petroleum technology and for production of organomineral adsorbents with high adsorption capacity on extraction mercury from sewages.  相似文献   
69.
The capillary pressure in a liquid interlayer between two spherical particles is calculated as a function of their sizes and the wetting properties of the liquid.  相似文献   
70.
The crystallization behavior of miscible syndiotactic polystyrene (sPS) and atactic polystyrene (aPS) blends with different sPS/aPS weight ratios was investigated in supercritical CO2 by using Fourier‐transform infrared spectroscopy, differential scanning calorimetry, and wide‐angle X‐ray diffraction. Supercritical CO2 and aPS exhibited different effects on the conformational change of sPS and competed with each other. Increasing the content of amorphous aPS in the blends made its effect on the conformational change of sPS gradually surpass that of supercritical CO2. Supercritical CO2 favored the formation of the helical conformation of sPS in lower temperature range and the all trans planar conformation in higher temperature range, instead of forming the latter one only in higher temperature range in ambient atmosphere. However, increasing aPS content in the blends pushed the range for forming the helical conformation to lower temperature and made the all trans planar conformation dominant in aPS/sPS 25/75 blend after treating in supercritical CO2 above 60 °C. The all trans planar zigzag conformation was more favorable than the helical conformation after mixing aPS in sPS in supercritical CO2. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1755–1764, 2007  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