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   356389篇
  免费   2066篇
  国内免费   640篇
化学   170371篇
晶体学   5410篇
力学   18521篇
综合类   9篇
数学   52541篇
物理学   112243篇
  2019年   2291篇
  2018年   11088篇
  2017年   11869篇
  2016年   8210篇
  2015年   3410篇
  2014年   4388篇
  2013年   10779篇
  2012年   12033篇
  2011年   21168篇
  2010年   13568篇
  2009年   13464篇
  2008年   18860篇
  2007年   22218篇
  2006年   9056篇
  2005年   13928篇
  2004年   10448篇
  2003年   9878篇
  2002年   7943篇
  2001年   7474篇
  2000年   5963篇
  1999年   4396篇
  1998年   3897篇
  1997年   3861篇
  1996年   3756篇
  1995年   3435篇
  1994年   3580篇
  1993年   3266篇
  1992年   3731篇
  1991年   3735篇
  1990年   3672篇
  1989年   3540篇
  1988年   3655篇
  1987年   3543篇
  1986年   3359篇
  1985年   4444篇
  1984年   4730篇
  1983年   3959篇
  1982年   4091篇
  1981年   4017篇
  1980年   3990篇
  1979年   3975篇
  1978年   4293篇
  1977年   4140篇
  1976年   4229篇
  1975年   3897篇
  1974年   3938篇
  1973年   4127篇
  1972年   2883篇
  1971年   2399篇
  1970年   2205篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
121.
The distribution of mono- poly- and unlabelled protein molecules in the radiolabelling mixture was calculated from probability point of view as a function of the radioiodine/protein ratio.  相似文献   
122.
On the basis of a computer analysis of four classes of toxic polypeptides, generalized primary structures of each class have been obtained which can be used for planning the synthesis of biologically active compounds.  相似文献   
123.
The precision of intensity modulated fiber optic sensor systems mainly is restricted by the attenuation characteristics of the analog fiber optical data link. Special encoding and referencing schemes are used to overcome this data link dependence. In this paper encoding and referencing principles for optical sensors are outlined and compared. Especially the two wavelengths referencing and the optical delay line processing techniques are discussed in more detail and results are presented.  相似文献   
124.
The synergetic effect of corrosion and corrosion induced hydrogen embrittlement damage processes which occur at local scale has been found to result in a dramatic macroscopic tensile ductility loss of the 2024 aluminum alloy. In the present work, the tensile behaviour of corroded 2024 T351 specimens has been estimated on the basis of FE analysis by taking into account the local material properties in the damaged areas. A parametric study is involved to account for the effect of thickness in the results. Calculated tensile properties obtained with the analysis agree well with experimental data.  相似文献   
125.
Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca1?x R xF2+x (R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region.  相似文献   
126.
Summary Three weak variants of compactness which lie strictly between compactness and quasicompactness, are introduced. Their basic properties are studied. The interplay with mapping and their direct and inverse preservation under mappings are investigated. In the process three decompositions of compactness are observed.  相似文献   
127.
128.
129.
A mixed problem is considered for a system of partial differential equations modeling the process of adsorption dynamics. An existence and uniqueness theorem is proved for this problem, and the solution properties are investigated. The inverse problem is posed, involving the determination of the system coefficient given additional information about the solution. A uniqueness theorem is proved for the solution of the inverse problem.__________Translated from Prikladnaya Matematika i Informatika, No. 16, pp. 5 – 14, 2004.  相似文献   
130.
The effect of ethylene glycol (EG) on the formation of whiskers and fibers of complex oxides with the general formula MCo2O4 upon the thermolysis of M1/3Co2/3C2O4 (M = Zn, Mn) oxalates has been studied. New compounds (solvates) are formed when powdered oxalates are heated with EG. In the solvates, EG molecules substitute for water molecules according to the reaction M1/3Co2/3C2O4 · 2H2O + HOCH2CH2OH = M1/3Co2/3C2O4(HOCH2CH2OH) + 2H2O. The solvates have been characterized using X-ray powder diffraction, microscopy, IR spectroscopy, thermogravimetry, and chemical analysis. The shape, structure, and particle size of the thermolysis products of EG-modified oxalates have been determined using scanning electron microscopy.  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