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   30590篇
  免费   999篇
  国内免费   179篇
化学   20625篇
晶体学   287篇
力学   978篇
综合类   1篇
数学   2704篇
物理学   7173篇
  2023年   180篇
  2022年   454篇
  2021年   562篇
  2020年   480篇
  2019年   498篇
  2018年   379篇
  2017年   359篇
  2016年   834篇
  2015年   723篇
  2014年   911篇
  2013年   1695篇
  2012年   2150篇
  2011年   2417篇
  2010年   1443篇
  2009年   1290篇
  2008年   1962篇
  2007年   1815篇
  2006年   1714篇
  2005年   1567篇
  2004年   1389篇
  2003年   1099篇
  2002年   1095篇
  2001年   745篇
  2000年   656篇
  1999年   386篇
  1998年   287篇
  1997年   340篇
  1996年   372篇
  1995年   289篇
  1994年   297篇
  1993年   306篇
  1992年   302篇
  1991年   226篇
  1990年   182篇
  1989年   170篇
  1988年   154篇
  1987年   133篇
  1986年   109篇
  1985年   195篇
  1984年   135篇
  1983年   113篇
  1982年   139篇
  1981年   99篇
  1980年   92篇
  1978年   95篇
  1977年   104篇
  1976年   106篇
  1975年   112篇
  1974年   83篇
  1973年   110篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
The neutron irradiated potassium hexacyanoferrate(III) solutions were analyzed for Fe(CN)64?, Fe(CN)63?, and Prussian blue. The retention values (1.1%) were constant throughout the pH and concentration ranges studied, and did not change with the length of irradiation. The complex behavior of the radiochemical yield of the Fe(CN)64? and Prussian blue was attributed to the competition of the various reactions involved in the irradiation.  相似文献   
44.
45.
It is conceivable that the high-T c superconducting perovskites are conventional electronphonon superconductors. In this case one expects significant strong-coupling effects because of the unusually high ratiok B T c / of the order 0.1 and greater. We use a set of reasonable models for the Eliashberg function 2 F() (which takes into account available information on the phonon spectra and which fit the measuredT c 's) and calculate strong-coupling effects in the specific heatc s (T)/T c , the ratio 0/k B T c , the critical fieldsH c (T) andH c2 (T) including Pauli limiting, and other measurable quantities. Strongcoupling corrections turn out to be in the range of 0 to about 100%, depending on the quantity of interest. We discuss the perspectives of using strong-coupling effects as indicators for conventional electron-phonon superconductivity in the new materials.  相似文献   
46.
47.
[reaction: see text] Anomalous ozonolysis of strained bicyclic allylic alcohols yields alpha-hydroxymethyl ketones. The proposed mechanism involves an unusual trapping of the primary ozonide that undergoes a Grob-like fragmentation instead of dissociating into the Criegee intermediates.  相似文献   
48.
A rapid flow-injection sandwich enzyme immunoassay suitable for the direct determination of proteins in biological samples is described. The proposed system utilizes highly active adenosine deaminase—antibody conjugates in conjunction with a flow-through immunoreactor and an ammonium ion-selective potentiometric detector. After appropriate sample/reagent injection steps, the enzyme activity bound to the reactor is measured by diverting a coninuously flowing stream of substrate (adenosine) through the packed immunocolumn and detecting liberated ammonium ions downstream with a tubular ammonium ion-selective electrode. The bound enzyme activity is directly proportional to the concentration of analyte in the original sample. By using non-equilibrium flow-rates of sample and reagent slugs, a single protein assay takes less than 12 min, including regeneration of the reactor. The proposed method is shown to be selective, reproducible and capable of determining accurately the model protein (human IgC) at sub-μg ml?1 concentrations.  相似文献   
49.
K K Lee  A E Ellis 《Electrophoresis》1989,10(10):729-731
A rapid and sensitive silver-lipopolysaccharide staining method has been developed by using PhastSystem. The total time of the procedure (including time of Phastgel electrophoresis) is within 2 h. It is at least 10 times faster than the previous reported methods and the sensitivity is also increased.  相似文献   
50.
Applied Biochemistry and Biotechnology - By inserting metallocatalysts (such as platinum, osmium, or ruthenium) at the reducing site of photosystem I (PSI), electrons that emerge from PSI can be...  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