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   119529篇
  免费   1087篇
  国内免费   586篇
化学   43434篇
晶体学   1771篇
力学   7953篇
综合类   33篇
数学   27082篇
物理学   40929篇
  2023年   131篇
  2022年   224篇
  2021年   225篇
  2020年   252篇
  2019年   244篇
  2018年   9968篇
  2017年   10935篇
  2016年   4831篇
  2015年   1272篇
  2014年   531篇
  2013年   723篇
  2012年   5416篇
  2011年   14558篇
  2010年   8340篇
  2009年   8485篇
  2008年   12283篇
  2007年   16210篇
  2006年   672篇
  2005年   7968篇
  2004年   4162篇
  2003年   4068篇
  2002年   1887篇
  2001年   434篇
  2000年   570篇
  1999年   288篇
  1998年   231篇
  1997年   185篇
  1996年   365篇
  1995年   242篇
  1994年   218篇
  1993年   192篇
  1992年   193篇
  1991年   213篇
  1990年   189篇
  1989年   172篇
  1988年   162篇
  1987年   170篇
  1986年   168篇
  1985年   175篇
  1984年   200篇
  1983年   193篇
  1982年   181篇
  1981年   191篇
  1980年   196篇
  1979年   189篇
  1978年   218篇
  1977年   130篇
  1976年   141篇
  1973年   140篇
  1968年   129篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
The launch of the gamma-ray telescope Fermi Large Area Telescope (Fermi-LAT) started a pivotal period in indirect detection of dark matter. By outperforming expectations, for the first time a robust and stringent test of the paradigm of weakly interacting massive particles (WIMPs) is within reach. In this paper, we discuss astrophysical targets for WIMP detection and the challenges they present, review the analysis tools which have been employed to tackle these challenges, and summarize the status of constraints on and the claimed detections in the WIMP parameter space. Methods and results will be discussed in comparison to Imaging Air Cherenkov Telescopes. We also provide an outlook on short term and longer term developments.  相似文献   
24.
The structure and properties of 12Cr1MoV steel irradiated with a zirconium ion beam were studied by optical microscopy, scanning electron microscopy, and micro- and nanoindentation. It is shown that the modification covers the entire cross-section of the irradiated specimens to a depth of 1 mm. The data on irradiation-induced structural changes are used to interpret the changes in mechanical properties of the irradiated specimens under static and cyclic loading. Particular attention is given to analysis of strain estimation by the digital image correlation method.  相似文献   
25.
26.
27.
28.
Submicron CaZrO3 powder is obtained in combustion reactions (solution combustion synthesis—SCS) with glycine. It is found that SCS reduces the sintering temperature of CaZrO3 powders. The dielectric properties of calcium zirconate ceramics are studied by the electrochemical impedance method. It is shown that a ceramics of powders obtained by the SCS method has high dielectric characteristics.  相似文献   
29.
Inorganic planar ring-shape molecules with 4n + 2 π electrons are always the focus of experimental synthesis and theoretical research due to their potential aromaticity and stability. In this work, the whole series of five-membered heterocycle monoanions X nY5-n (X, Y = group 15 elements; n = 1-4) were thoroughly investigated by means of density functional theory calculations. They all have large formation energies and HOMO-LUMO gap energies, suggesting the potential thermodynamic and kinetic stability. Their aromaticities are comparable to that of typical aromatic hydrocarbons. Their thermal stabilities were firmly established by the ab initio molecular dynamics simulations. As most of them are predicted for the first time, their various spectra were simulated for experimental characterization. Furthermore, we demonstrate that these five-membered cyclic anions can be employed as η5-ligand to construct novel all-inorganic metallocenes, which may serve as the building blocks of low-dimensional nanomaterials.  相似文献   
30.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  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