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   10430篇
  免费   314篇
  国内免费   48篇
化学   7700篇
晶体学   115篇
力学   142篇
数学   545篇
物理学   2290篇
  2022年   36篇
  2021年   83篇
  2020年   114篇
  2019年   150篇
  2018年   98篇
  2017年   80篇
  2016年   186篇
  2015年   176篇
  2014年   234篇
  2013年   519篇
  2012年   542篇
  2011年   629篇
  2010年   346篇
  2009年   385篇
  2008年   639篇
  2007年   591篇
  2006年   649篇
  2005年   585篇
  2004年   559篇
  2003年   442篇
  2002年   448篇
  2001年   225篇
  2000年   221篇
  1999年   141篇
  1998年   124篇
  1997年   117篇
  1996年   105篇
  1995年   85篇
  1994年   95篇
  1993年   128篇
  1992年   116篇
  1991年   101篇
  1990年   81篇
  1989年   70篇
  1988年   92篇
  1987年   96篇
  1986年   110篇
  1985年   151篇
  1984年   135篇
  1983年   56篇
  1982年   113篇
  1981年   124篇
  1980年   108篇
  1979年   98篇
  1978年   81篇
  1977年   90篇
  1976年   75篇
  1975年   54篇
  1974年   61篇
  1973年   47篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
72.
A note on unit and class number of real quadratic fields   总被引:1,自引:0,他引:1  
Letp be an odd prime withp1 (mod 4) andQ(p) be the real quadratic field. Also let andh denote the fundamental unit and the class number of Q(p), respectively. The main purpose of this paper is to study the explicit expressions of h and 2h , and to discuss the problems related to the conjecture of Ankeny-Artin-Chowla.  相似文献   
73.
74.
75.
76.
The solubilities of o-, m- and p-xylene in water were measured at 25.0°C up to 250, 385, and 50 MPa, respectively. The solubility increased with increasing pressure up to 120 MPa (50 MPa for p-xylene) and then decreased. The reaction volumes, Vo accompanying the dissolution at 0.1 MPa were estimated as –3.6±0.5, –3.4±0.5, and –4.1±0.5 cm3-mol–1 for o-, m-, and p-xylene, respectively, from the pressure dependences of the solubilities. The limiting partial molar volumes, of p- and o-xylene in water under high pressure were estimated from Vo and the molar volume of the xylene. The partial molar volumes decreased with increasing pressure. The reaction volume for the formation of intra-molecular pairwise hydrophobic interaction between the methyl groups, as proposed by Ben-Naim, is discussed for the Vo of p- and o-xylene at 0.1 MPa.  相似文献   
77.
Reaction of gem-difluorinated vinyloxiranes with RCu(X)Li allowed us to introduce the R group regioselectively at the fluorine-attached terminal carbon atom in an SN2′ manner to afford (E)-allylic alcohols exclusively, while homoallylic alcohols with anti stereochemical relationship were found to be obtained selectively from higher-ordered cuprates derived from CuCl and RMgBr in a ratio of 1:3.  相似文献   
78.
Effects of non-steroidal anti-inflammatory drugs (NSAID: amfenac sodium, diclofenac sodium, indomethacin and ketoprofen) on the generation of superoxide anion (O2-) by isolated rat polymorphonuclear leukocytes (PMN) were studied spectrophotometrically using cytochrome c. The effects of these drugs were also studied on O2- production by the xanthine-xanthine oxidase and reduced nicotinamide adenine dinucleotide phosphate (NADPH)-NADPH oxidase systems. Amfenac sodium, at 0.1 mM, inhibited significantly O2- generation in rat PMN induced by opsonized zymosan. At 0.5 mM, diclofenac sodium and indomethacin inhibited the O2- generation in rat PMN. All of the above drugs slightly inhibited O2- production by the xanthine-xanthine oxidase system. On the other hand, O2- production by the NADPH-NADPH oxidase system was significantly inhibited by the addition of amfenac sodium, ketoprofen or indomethacin. These results suggest that non-steroidal anti-inflammatory drugs do not work as an O2- scavenger and block O2- production by the NADPH-NADPH oxidase system of rat PMN. It is concluded that amfenac sodium and the other drugs are able to inhibit granulocyte O2- production by blocking the activation of NADPH-oxidase.  相似文献   
79.
Quantum yields, lifetimes and shapes of fluorescence from polymers containing the trans-1,2-dicarbazolylcyclobutane (DCZB) or carbazolyl structures were studied in N,N-dimethylformamide. No sandwich-type excimer formation was observed for DCZB polymers. The so-called second excimer observed in poly(9-vinylcarbazole) might also be produced in poly(9-ethyl-3-vinylcarbazole).  相似文献   
80.
A very short synthesis of chiral prostaglandin E1 methyl ester is described.  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