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   690780篇
  免费   5436篇
  国内免费   1973篇
化学   339519篇
晶体学   9711篇
力学   36500篇
综合类   20篇
数学   108276篇
物理学   204163篇
  2021年   5607篇
  2020年   6112篇
  2019年   6887篇
  2018年   18820篇
  2017年   18735篇
  2016年   18561篇
  2015年   7885篇
  2014年   12026篇
  2013年   27613篇
  2012年   24640篇
  2011年   34831篇
  2010年   23992篇
  2009年   24335篇
  2008年   30029篇
  2007年   31642篇
  2006年   22110篇
  2005年   20781篇
  2004年   19550篇
  2003年   18268篇
  2002年   17126篇
  2001年   18423篇
  2000年   14134篇
  1999年   10880篇
  1998年   9090篇
  1997年   8992篇
  1996年   8476篇
  1995年   7621篇
  1994年   7571篇
  1993年   7215篇
  1992年   7918篇
  1991年   8409篇
  1990年   8029篇
  1989年   7870篇
  1988年   7709篇
  1987年   7562篇
  1986年   7136篇
  1985年   9073篇
  1984年   9402篇
  1983年   7803篇
  1982年   8127篇
  1981年   7508篇
  1980年   7252篇
  1979年   7873篇
  1978年   8195篇
  1977年   8014篇
  1976年   7947篇
  1975年   7584篇
  1974年   7373篇
  1973年   7680篇
  1972年   5538篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
V. A. Steklov Mathematics Institute, USSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 79, No. 3, pp. 347–358, June, 1989.  相似文献   
14.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 1, pp. 46–50, January, 1991.  相似文献   
15.
16.
A systematic study on the electrochemical behavior of diosmin in Britton-Robinson buffer (pH 2.0-10.0) at a glassy carbon electrode (GCE) was made. The oxidation process of the drug was found to be quasi-reversible with an adsorption-controlled step. The adsorption stripping response was evaluated with respect to various experimental conditions, such as the pH of the supporting electrolyte, the accumulation potential and the accumulation time. The observed anodic peak current at +0.73 V vs. Ag/AgCl reference electrode increased linearly over two orders of magnitude from 5.0x10(-8) M to 9.0x10(-6) M. A limit of detection down to 3.5x10(-8) M of diosmin at the GCE was achieved with a mean recovery of 97+/-2.1%. Based on the electrochemical data, an open-circuit accumulation step in a stirred sample solution of BR at pH 3.0 was developed. The proposed method was successfully applied to the determination of the drug in pharmaceutical formulations. The results compared favorably with the data obtained via spectrophotometric and HPLC methods.  相似文献   
17.
Ionic conductivity of dry quaternary ammonium polymer, polydiallyldimethylammonium with Cl and H2PO4 counter ions was studied in a wide range of frequencies (10−2-107 Hz) and temperatures (300-470 K). The data were analysed within the formalism of permittivity. WAXS, and thermal properties of this polymer were investigated prior to conductivity measurements.  相似文献   
18.
19.
Systems for automatic detection and correction of spelling errors in natural language texts are considered. The development of such systems for both English and Russian (and for inflected languages in general, including all Slavic languages) is discussed. An approach associated with morphological analysis of the wordforms in the given text is described. The topics considered in the paper include the main methods of automatic spelling correction, levels of automation of the spelling error correction process, the effect of the type of computer used, the use of spelling error correctors in a stand-alone mode and in combination with word-processing software, and the maintenance of auxiliary dictionaries.Translated from Itogi Nauki i Tekhniki, Seriya Teoriya Veroyatnostei, Matematicheskaya Statistika, Teoreticheskaya Kibernetika, Vol. 28, pp. 111–139, 1988.  相似文献   
20.
Consider a projective algebraic variety W which is an irreducible component of the set of all common zeros of a family of homogeneous polynomials of degrees less than d in n + 1 variables over a field of zero characteristic. Consider a dominant rational morphism from W to W′ given by homogeneous polynomials of degree d′. We suggest algorithms for constructing objects in general position related to this morphism. They generalize some algorithms from the first part of the paper to the case dim W > dim W′. These algorithms are deterministic and polynomial in (dd′)n and the size of the input. Bibliography: 12 titles. __________ Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 325, 2005, pp. 181–224.  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