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   518058篇
  免费   5150篇
  国内免费   1550篇
化学   263907篇
晶体学   6279篇
力学   23604篇
综合类   10篇
数学   73954篇
物理学   157004篇
  2021年   3450篇
  2020年   3846篇
  2019年   4321篇
  2018年   12663篇
  2017年   13083篇
  2016年   11510篇
  2015年   5852篇
  2014年   7898篇
  2013年   20270篇
  2012年   18541篇
  2011年   28337篇
  2010年   18174篇
  2009年   18031篇
  2008年   25420篇
  2007年   28362篇
  2006年   15970篇
  2005年   19858篇
  2004年   15600篇
  2003年   14360篇
  2002年   12477篇
  2001年   12296篇
  2000年   9771篇
  1999年   7281篇
  1998年   6240篇
  1997年   6273篇
  1996年   5789篇
  1995年   5189篇
  1994年   5082篇
  1993年   5164篇
  1992年   5584篇
  1991年   5613篇
  1990年   5328篇
  1989年   5270篇
  1988年   5266篇
  1987年   5113篇
  1986年   4901篇
  1985年   6557篇
  1984年   6951篇
  1983年   5650篇
  1982年   6190篇
  1981年   5989篇
  1980年   5667篇
  1979年   5947篇
  1978年   6278篇
  1977年   6072篇
  1976年   6271篇
  1975年   5726篇
  1974年   5749篇
  1973年   6253篇
  1972年   3976篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
41.
Crystallography Reports - Methods of coherent X-ray diffraction imaging of the spatial structure of noncrystalline objects and nanocrystals (nanostructures) are considered. Particular attention is...  相似文献   
42.
Physics of Particles and Nuclei Letters - When creating accelerators and storage-ring installations in a compact space, there is not always enough space for all the necessary magnet elements. In...  相似文献   
43.
Russian Physics Journal - A relationship between the structural-morphological and physical-mechanical properties of macro-porous calcium phosphate (CaP) coatings on the surface of titanium implants...  相似文献   
44.
45.
Russian Journal of Physical Chemistry A - Rapidly quenched alloys of aluminum with cobalt and zirconium are investigated using a combination of means of physicochemical analysis to study the...  相似文献   
46.
The change in the free-electron density in ultrathin (5 nm) superconducting NbN films in the initial state and after irradiation by O+ ions to doses of (0.1–0.9) × 1017 cm–2 has been studied by electron energy-loss spectroscopy (EELS). The analysis has been performed on cross section samples prepared by the focused ion beam method, using plasmon oscillations with energies up to 50 eV. The radiation-induced replacement of nitrogen atoms with oxygen atoms in niobium nitride is found to change the electrical properties of the material, which leads to a decrease in the free-electron density with an increase in the irradiation dose.  相似文献   
47.
The growth-fragmentation equation describes a system of growing and dividing particles, and arises in models of cell division, protein polymerisation and even telecommunications protocols. Several important questions about the equation concern the asymptotic behaviour of solutions at large times: at what rate do they converge to zero or infinity, and what does the asymptotic profile of the solutions look like? Does the rescaled solution converge to its asymptotic profile at an exponential speed? These questions have traditionally been studied using analytic techniques such as entropy methods or splitting of operators. In this work, we present a probabilistic approach: we use a Feynman–Kac formula to relate the solution of the growth-fragmentation equation to the semigroup of a Markov process, and characterise the rate of decay or growth in terms of this process. We then identify the Malthus exponent and the asymptotic profile in terms of a related Markov process, and give a spectral interpretation in terms of the growth-fragmentation operator and its dual.  相似文献   
48.

A complex study of a spearhead dated back to IV mill. BC from burial mound no. 1 near Novosvobodnaya village (collection of the State Historical Museum) and, in particular, the material of spearhead superficial crust has been performed. The elemental and phase composition of the metal of spearhead and the superficial crust on its surface have been determined by scanning electron microscopy, jointly with energydispersive X-ray microanalysis and X-ray phase analysis. A comparative analysis of the results of studying the spearhead superficial crust and similar crusts on other artifacts from the mounds near Novosvobodnaya village suggest natural origin of the crust on copper?arsenic artifacts.

  相似文献   
49.
50.
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