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   388755篇
  免费   4695篇
  国内免费   1864篇
化学   206584篇
晶体学   5919篇
力学   17119篇
综合类   64篇
数学   45060篇
物理学   120568篇
  2020年   3247篇
  2019年   3593篇
  2018年   4725篇
  2017年   4645篇
  2016年   6774篇
  2015年   4349篇
  2014年   6600篇
  2013年   16630篇
  2012年   13610篇
  2011年   16464篇
  2010年   11562篇
  2009年   11325篇
  2008年   15225篇
  2007年   15483篇
  2006年   14653篇
  2005年   13193篇
  2004年   12023篇
  2003年   10661篇
  2002年   10431篇
  2001年   11690篇
  2000年   9006篇
  1999年   6796篇
  1998年   5574篇
  1997年   5533篇
  1996年   5320篇
  1995年   4830篇
  1994年   4788篇
  1993年   4559篇
  1992年   5107篇
  1991年   5108篇
  1990年   4839篇
  1989年   4602篇
  1988年   4590篇
  1987年   4547篇
  1986年   4375篇
  1985年   5767篇
  1984年   6057篇
  1983年   5022篇
  1982年   5387篇
  1981年   5144篇
  1980年   4856篇
  1979年   5083篇
  1978年   5417篇
  1977年   5417篇
  1976年   5442篇
  1975年   5034篇
  1974年   5120篇
  1973年   5308篇
  1972年   3804篇
  1971年   3003篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Journal of Radioanalytical and Nuclear Chemistry - In this paper a study for the selection of an NPE (nonylphenol ethoxylates)—free cocktail is discussed in order to be used for our routine...  相似文献   
22.
23.
Ukrainian Mathematical Journal - We establish new criteria of compatibility for a linear system of equations (equivalent to the Kronecker–Capelli theorem) or inequalities (equivalent to the...  相似文献   
24.
Chen  R. J.  Chen  W.  Kong  F. L. 《Analysis Mathematica》2022,48(1):19-28

Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.

  相似文献   
25.
A temperature control unit was implemented to vary the temperature of samples studied on a commercial Mobile Universal Surface Explorer nuclear magnetic resonance (MOUSE-NMR) apparatus. The device was miniaturized to fit the maximum MOUSE sampling depth (25 mm). It was constituted by a sample holder sandwiched between two heat exchangers placed below and above the sample. Air was chosen as the fluid to control the temperature at the bottom of the sample, at the interface between the NMR probe and the sample holder, in order to gain space. The upper surface of the sample was regulated by the circulation of water inside a second heat exchanger placed above the sample holder. The feasibility of using such a device was demonstrated first on pure water and then on several samples of bread dough with different water contents. For this, T1 relaxation times were measured at various temperatures and depths and were then compared with those acquired with a conventional compact closed-magnet spectrometer. Discussion of results was based on biochemical transformations in bread dough (starch gelatinization and gluten heat denaturation). It was demonstrated that, within a certain water level range, and because of the low magnetic field strength of the MOUSE, a linear relationship could be established between T1 relaxation times and the local temperature in the dough sample.  相似文献   
26.
Crystallography Reports - The orientation of grains and the special boundaries formed by them in multicrystalline silicon has been studied by electron backscattered diffraction. It is found that...  相似文献   
27.
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   
28.
29.
30.
In a 2:2 reaction with silver(I) chloride or bromide, 1,5-bis(1-phospholano)pentane ( 1a ) afforded frame-like macrocyclic structures, with intra- ( 2 , Cl) or intermolecular ( 3 , Br) halido bridges. In contrast, 1,7-bis(1-phospholano)heptane ( 1b ) formed coordination polymers 4a (Cl) and 4b (Br) with bridging bis-phospholane and halido ligands. A unique paddle wheel-type metallacryptand structure 5 was obtained from 1a and silver(I) bromide in a 2:3 reaction (M:L). All complexes were fully characterized by NMR, IR spectroscopy, mass spectrometry, and X-ray crystallography.  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