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   5826篇
  免费   162篇
  国内免费   21篇
化学   4075篇
晶体学   81篇
力学   81篇
数学   264篇
物理学   1508篇
  2022年   30篇
  2021年   33篇
  2020年   59篇
  2019年   63篇
  2018年   62篇
  2017年   40篇
  2016年   88篇
  2015年   97篇
  2014年   124篇
  2013年   282篇
  2012年   263篇
  2011年   289篇
  2010年   168篇
  2009年   169篇
  2008年   328篇
  2007年   263篇
  2006年   285篇
  2005年   271篇
  2004年   264篇
  2003年   208篇
  2002年   216篇
  2001年   155篇
  2000年   162篇
  1999年   88篇
  1998年   66篇
  1997年   66篇
  1996年   69篇
  1995年   46篇
  1994年   69篇
  1993年   95篇
  1992年   100篇
  1991年   76篇
  1990年   67篇
  1989年   57篇
  1988年   77篇
  1987年   75篇
  1986年   81篇
  1985年   111篇
  1984年   102篇
  1983年   46篇
  1982年   80篇
  1981年   85篇
  1980年   79篇
  1979年   67篇
  1978年   60篇
  1977年   76篇
  1976年   59篇
  1975年   45篇
  1974年   53篇
  1973年   32篇
排序方式: 共有6009条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
45.
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   
46.
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   
47.
A very short synthesis of chiral prostaglandin E1 methyl ester is described.  相似文献   
48.
Six sulfonazo-III isomers were synthesized, and their color reactions with alkaline earth metals and lanthanum investigated. All six reagents had good sensitivities for lanthanum (? = 1.9–5.0·104), but the sensitivities for alkaline earth metals were fairly low except for the barium chelate of sulfonazo-III (? = 2.8 · 104). The position of the sulfo group on the phenyl ring and the symmetry of the reagent are important for the barium reactions, but of little significance for the lanthanum reactions. The effects of water-miscible solvents are also described.  相似文献   
49.
A novel tumor-detection system consisting of complementmediated cytolytic reaction and an image processing system was developed for the simple and rapid determination of tumor cells. The present system consists of a CCD image sensor, image memory board, personal computer, and microscope. When monoclonal antibody 3C4, which is specific to the guinea pig hepatoma L-10, was added to cell suspension, only L-10 cytolysis occurred. Cytolysis caused a decrease in brightness of the cells observed by phase-contrast microscopy. The phase contrast image of the cells before cytolysis was converted to a digitalized signal and stored in computer memory. After cytolysis, a brightness threshold above that of lysed cells was subtracted from the digitalized signal and compared to the signal stored before reaction. L-10 cells in mixed cell suspension were determined specifically by the system. Measurement time was only 2 sec and overall time, including reaction time, was approximately 30 min. Since this method does not require a cell washing process, automation of the whole system is possible.  相似文献   
50.
Oligo(phenylene sulfide) (OPS) containing one disulfide bond at the end of the chain, which was obtained by the oxidative polymerization of diphenyl disulfide, had a relatively low Td10%(temperature for 10% weight loss) of 412 °C because of degradation of the disulfide bond. But this thermal cleavage of the disulfide bond promoted the curing reaction through thiophenoxy radical formation. OPS was allowed to react with diiodobenzene at 220 °C. The thermal stability of OPS was improved through the consumption of the disulfide bond and the coupling of the chain.  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