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   28122篇
  免费   1824篇
  国内免费   1593篇
化学   16005篇
晶体学   129篇
力学   442篇
综合类   611篇
数学   6482篇
物理学   7870篇
  2023年   197篇
  2022年   328篇
  2021年   1151篇
  2020年   601篇
  2019年   716篇
  2018年   478篇
  2017年   502篇
  2016年   665篇
  2015年   758篇
  2014年   948篇
  2013年   1786篇
  2012年   1147篇
  2011年   1322篇
  2010年   1273篇
  2009年   1662篇
  2008年   1759篇
  2007年   1912篇
  2006年   1421篇
  2005年   837篇
  2004年   799篇
  2003年   881篇
  2002年   867篇
  2001年   846篇
  2000年   573篇
  1999年   453篇
  1998年   462篇
  1997年   321篇
  1996年   401篇
  1995年   355篇
  1994年   374篇
  1993年   423篇
  1992年   421篇
  1991年   276篇
  1990年   231篇
  1989年   187篇
  1988年   218篇
  1987年   185篇
  1986年   200篇
  1985年   310篇
  1984年   226篇
  1983年   139篇
  1982年   285篇
  1981年   466篇
  1980年   423篇
  1979年   463篇
  1978年   368篇
  1977年   278篇
  1976年   237篇
  1974年   74篇
  1973年   149篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
992.
993.
994.
We study Brauer–Manin obstructions to the Hasse principle and to weak approximation on algebraic surfaces over number fields. A technique for constructing Azumaya algebra representatives of Brauer group elements is given, and this is applied to the computation of obstructions.  相似文献   
995.
996.
Magnetic resonance (MR) microscopy of up to 1–5-μm resolutions have been reported previously. The tested phantom structures, however, had widths one order of magnitude bigger than the reported resolutions, e.g., spherical beads or capillary tubes of tens-of-micron diameters or wall thicknesses have been imaged. In this study, we fabricated structures having a few micron widths on a silicon wafer and imaged them using our 1-μm-resolution MR microscopy at 14.1 T. Micron scale width structures were, for the first time, resolved by MR microscopy.  相似文献   
997.
Modern advances in radiation medicine – radiodiagnosis, radiotherapy and interventional radiography – each present dosimetry challenges for the medical physicist that did not exist previously. In all of these areas a constant balance has to be made between the treatment necessary to destroy the tumor and the unnecessary exposure of healthy tissue. Innovative applications of OSL dosimetry are now appearing in each of these areas to help the medical physicist and oncologist design the most effective, and least deleterious, treatment for their patients. High sensitivity, precise delivery of light, fast readout times, simpler readers and easier automation are the main advantages of OSL in comparison with TLD.This work aimed to study the application of OSL technique using lithium fluoride dosimeters doped with magnesium and titanium (LiF:Mg,Ti) for application in beta and gamma dosimetry.  相似文献   
998.
Binding of multiple proteins to DNA is crucial in many regulatory cellular processes. The kinetics of assembly and disassembly of DNA–multiple protein complexes is very difficult to study in detail due to the lack of suitable experimental approaches. A separation-based approach has been recently proposed to resolve disassembly kinetics of such complexes. While conceptually simple, the separation-based approach generates experimental data with very complex patterns. The analysis of these patterns is a challenging problem on its own. Here we report on a mathematical approach that can extract a solution for the experimental data obtained in separation-based analysis of sequential dissociation of a DNA complex with multiple proteins. This case describes the dissociation of proteins one-by-one from the complex. Generally speaking, a mathematical solution of such problems requires calculations of multiple integrals. Our approach reduces this procedure to taking double integrals and constructing their superposition. We tested this approach with the experimental data obtained for three-step sequential dissociation of complexes of DNA with two protein copies.  相似文献   
999.
《Analytical letters》2012,45(12):1305-1313
Abstract

The solid monoxime of 2, 3-butanedione is a more convenient material than liquid dione for the homogenous generation of DMG. 2, 3-butanedione dioxime. Determinations of Ni in steels and in pure Ni(II) solutions have shown the optimum pH and order of adding reagents. Gravimetric and/or an EDTA titrimetric finish are possible for a method of reliability within ± 0.2 mg of Ni in 50–150 mg Ni. The solid has the same character and filterability as that from the 1960 dione method of Salesin and Gordon1.  相似文献   
1000.
Wine derives its economic value to a large extent from geographical origin, which has a significant impact on the quality of the wine. According to the food legislation, wines can be without geographical origin (table wine) and wines with origin. Wines with origin must have characteristics which are essential due to its region of production and must be produced, processed and prepared, exclusively within that region.  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