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   32644篇
  免费   124篇
  国内免费   280篇
化学   12358篇
晶体学   322篇
力学   1697篇
综合类   12篇
数学   9286篇
物理学   9373篇
  2022年   65篇
  2021年   117篇
  2020年   88篇
  2019年   108篇
  2018年   1344篇
  2017年   1590篇
  2016年   873篇
  2015年   616篇
  2014年   596篇
  2013年   845篇
  2012年   3283篇
  2011年   2485篇
  2010年   1971篇
  2009年   1685篇
  2008年   734篇
  2007年   781篇
  2006年   701篇
  2005年   4527篇
  2004年   3989篇
  2003年   2385篇
  2002年   564篇
  2001年   388篇
  2000年   149篇
  1999年   211篇
  1998年   149篇
  1997年   104篇
  1996年   79篇
  1995年   72篇
  1994年   65篇
  1992年   200篇
  1991年   199篇
  1990年   169篇
  1989年   154篇
  1988年   125篇
  1987年   83篇
  1986年   78篇
  1985年   76篇
  1984年   65篇
  1982年   57篇
  1980年   54篇
  1979年   57篇
  1978年   70篇
  1977年   61篇
  1976年   99篇
  1975年   73篇
  1974年   68篇
  1973年   86篇
  1972年   78篇
  1969年   52篇
  1968年   51篇
排序方式: 共有10000条查询结果,搜索用时 937 毫秒
1.
Russian Journal of General Chemistry - Aminophosphabetaines, i.e., isobutyl {[alkyl(dimethyl)ammonio]methyl}phosphonates with higher alkyl substituents at the nitrogen atom, were obtained by a...  相似文献   
2.
Russian Journal of Applied Chemistry - A method for the disposal of hydrolysis lignin waste based on its modification with ZnCl2 and FeCl3 and subsequent carbonization at 800°C was proposed....  相似文献   
3.
4.
ABSTRACT

The authors present the results of an investigation in Fe–Ni-Cr austenitic alloys of the low-temperature deformation-induced segregations of nickel that form in the micro regions being (i) located close to grain- and subgrain boundaries and (ii) characteristic of the concentration and magnetic inhomogeneities indicated by the appearance of a dark diffraction contrast at the electron diffraction patterns taken from these regions typical (at the same time) of an enhanced value of Curie temperature. The observed effects were connected with the micro distortions caused by the local change of lattice parameter because of an increase in nickel concentration, as well as in the result of a magnetostriction dilatation. Using methods of the X-ray energy dispersive spectroscopy (XEDS) and atomic-probe body-section radiography (tomography – APT) has made it possible to determine the borders of those regions of austenite that were characteristic of an enhanced concentration of nickel in the fields of the localisation of a deformation-induced segregation of nickel in the vicinity of grain (subgrain) boundaries of austenitic alloys of the types Fe–13Cr–30Ni and Fe–37Ni–3Ti.  相似文献   
5.
Russian Journal of Applied Chemistry - Organo-inorganic composite materials based on films of polytetrafluoroethylene and tetrafluoroethylene–hexafluoropropylene copolymer, modified with...  相似文献   
6.
7.
8.
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards.  相似文献   
9.
The versatile behavior of a trihydrazidophosphoradamantane allowing the synthesis of a variety of neutral, mono- or di-cationic water-soluble molecules of potential interest for biphasic catalysis is reported.  相似文献   
10.
In this paper we construct an example of a word metric on an infinite cyclic subgroup. This example shows that subexponential distortion does not obstruct non-trivial growth of connected radii. This answers a question of Gromov [6]. The constructed metric has other pathological properies. Specifically, its asymptotic cone depends on the choice of ultrafilter and scaling sequence. The work has been partially supported by the Swiss National Science Foundation.  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