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   430951篇
  免费   6986篇
  国内免费   5298篇
化学   195057篇
晶体学   6040篇
力学   27234篇
综合类   325篇
数学   81817篇
物理学   132762篇
  2021年   4652篇
  2020年   5140篇
  2019年   5921篇
  2018年   17826篇
  2017年   17600篇
  2016年   15761篇
  2015年   6172篇
  2014年   9534篇
  2013年   15726篇
  2012年   17287篇
  2011年   25397篇
  2010年   18121篇
  2009年   18613篇
  2008年   20624篇
  2007年   22192篇
  2006年   12701篇
  2005年   12013篇
  2004年   11685篇
  2003年   11301篇
  2002年   10699篇
  2001年   9440篇
  2000年   7565篇
  1999年   5742篇
  1998年   5452篇
  1997年   5098篇
  1996年   4751篇
  1995年   4117篇
  1994年   4172篇
  1993年   4171篇
  1992年   4054篇
  1991年   4463篇
  1990年   4435篇
  1989年   4372篇
  1988年   4088篇
  1987年   4137篇
  1986年   3804篇
  1985年   4354篇
  1984年   4556篇
  1983年   3927篇
  1982年   4099篇
  1981年   3736篇
  1980年   3501篇
  1979年   4040篇
  1978年   4109篇
  1977年   4221篇
  1976年   4378篇
  1975年   4075篇
  1974年   3972篇
  1973年   4109篇
  1972年   3561篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Some features of the kinetics of the hydrolysis of apple protopectin have been studied on the basis of an analysis of monosaccharide residues of the pectin substances and determinations of characteristic viscosity. It has been shown that the fine regulation of the physicochemical parameters of the hydrolysis of protopectin leads to the formation of pectin substances with different properties.  相似文献   
42.
43.
44.
45.
46.
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   
47.
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   
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