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   495806篇
  免费   2925篇
  国内免费   1072篇
化学   226762篇
晶体学   6992篇
力学   28994篇
综合类   9篇
数学   86230篇
物理学   150816篇
  2021年   3848篇
  2020年   4252篇
  2019年   5050篇
  2018年   17225篇
  2017年   17123篇
  2016年   15541篇
  2015年   5540篇
  2014年   8945篇
  2013年   17690篇
  2012年   17613篇
  2011年   26721篇
  2010年   18645篇
  2009年   19270篇
  2008年   22226篇
  2007年   24068篇
  2006年   14528篇
  2005年   13827篇
  2004年   13310篇
  2003年   12765篇
  2002年   12023篇
  2001年   11387篇
  2000年   9051篇
  1999年   6759篇
  1998年   6253篇
  1997年   6030篇
  1996年   5543篇
  1995年   5017篇
  1994年   5020篇
  1993年   4930篇
  1992年   5104篇
  1991年   5613篇
  1990年   5377篇
  1989年   5380篇
  1988年   5124篇
  1987年   5117篇
  1986年   4749篇
  1985年   5752篇
  1984年   6073篇
  1983年   5138篇
  1982年   5480篇
  1981年   5067篇
  1980年   4783篇
  1979年   5339篇
  1978年   5562篇
  1977年   5554篇
  1976年   5665篇
  1975年   5309篇
  1974年   5221篇
  1973年   5390篇
  1972年   4253篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
It has been shown by the ESR of spin probes that thionin initially interacts with with negatively charged membranes electrostatically and then passes into the membranes to a depth comparable with the length of the hydrophobic sections of the protein loops.Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Brigham Young University, Provo, Utah, USA. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 594–597, July–August, 1993.  相似文献   
43.
44.
Twelve series of linear oligomers of four different degrees of polymerization (xn = 8.77−41.55), having a common perfluorinated random copolymeric chain as molecular body and two equal foreign end units of one of the types listed in Table 1, have been synthesized by derivatization of base samples of one of them having a diolic---CH2OH functionality. The glass transition temperature Tg of all the series was measured and thus examined as a function of xn. A clear end unit effect is observed, dominantly determined in every series by chemical nature and structure of the end units, quantitatively expressed at any xn by different positive or negative Tg deviations from the common asymptotic Tg value. The results are also discussed in terms of copolymer end effect and of relation between Tg and end copolymeric composition.  相似文献   
45.
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   
46.
On the basis of the method of successive approximations in formal series we construct systems of particular solutions of the equations of planar and flexural harmonic vibrations of thin rectilinear anisotropic plates with a plane of symmetry of elastic properties parallel to the faces. The solutions constructed are classified as special sk-functions of generalized complex variables. Translated fromTeoreticheskaya i Prikladnaya Mekhanika No. 24, 1993, pp. 54–61.  相似文献   
47.
We present the results of an experimental investigation of a RF splitting of57Fe hyperfine lines in the regime of NMR and Mössbauer double resonance. The experiments have been performed as a function of RF field intensity and static magnetic field magnitude. The intensity of the RF components and the separation between them are extremely sensitive to the frequency and amplitude of the RF magnetic field. The RF splitting of hyperfine lines is inversely proportional to the strength of the static magnetic field.  相似文献   
48.
The characterization of the clusters formed on alkaline hydrolysis of [PdCl4]2– was performed using17O,23Na,35Cl,133Cs NMR and UV spectroscopy. The chemical composition of the clusters was found to be [Pd(OH)2] n ·nNaCl. No mononuclear oxo- or hydroxocomplexes were detected. The spatial structure of the clusters is stabilized by alkali metal cations.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 675–679, April, 1993.  相似文献   
49.
The electrical conductivity of hydrosols of ultradispersed diamonds was studied. The electromembrane method for cleaning and concentrating of ultradispersed diamonds in hydrosols was considered. The influence exerted by the concentration of the dispersed phase on the electrical characteristics of the cleaning process was analyzed. A mathematical relation making it possible to evaluate the output characteristics of the process and to determine the geometrical characteristics of the apparatus was proposed.  相似文献   
50.
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   
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