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   2043篇
  免费   36篇
  国内免费   22篇
化学   1336篇
晶体学   61篇
力学   26篇
数学   125篇
物理学   553篇
  2022年   7篇
  2021年   7篇
  2019年   21篇
  2018年   17篇
  2017年   11篇
  2016年   27篇
  2015年   30篇
  2014年   26篇
  2013年   137篇
  2012年   69篇
  2011年   91篇
  2010年   57篇
  2009年   69篇
  2008年   97篇
  2007年   129篇
  2006年   96篇
  2005年   86篇
  2004年   103篇
  2003年   93篇
  2002年   86篇
  2001年   61篇
  2000年   45篇
  1999年   37篇
  1998年   30篇
  1997年   29篇
  1996年   32篇
  1995年   28篇
  1994年   37篇
  1993年   44篇
  1992年   41篇
  1991年   20篇
  1990年   23篇
  1989年   24篇
  1988年   29篇
  1987年   12篇
  1986年   21篇
  1985年   24篇
  1984年   25篇
  1983年   20篇
  1982年   23篇
  1981年   29篇
  1980年   11篇
  1979年   31篇
  1978年   20篇
  1977年   19篇
  1976年   20篇
  1975年   26篇
  1974年   23篇
  1973年   16篇
  1972年   10篇
排序方式: 共有2101条查询结果,搜索用时 31 毫秒
821.
The g-factors of two isomeric states at Ex = 3763 and 5170 keV in 216Ra have been measured to be 0.51 ± 0.03 and 0.63 ± 0.06, respectively, with a TDPAD method. Spin and parity assignments of 19? for the 3763 keV state and 25? or 24+ for the 5170 keV state are consistent with the measured g-factors. Proposed configurations for the 19? and 25? assignments are of the same type as those predicted by a deformed independent-particle model for 214Rn, which is an isotone of 216Ra.  相似文献   
822.
823.
824.
825.
We give a sufficient condition in order that an ideal of a real quadratic field capitulates in the cyclotomic -extension of by using a unit of an intermediate field. Moreover, we give new examples of 's for which Greenberg's conjecture holds by calculating units of fields of degree 6, 18, 54 and 162.

  相似文献   

826.
We give new examples of real quadratic fields for which the Iwasawa invariant and are both zero by calculating cyclotomic units of real cyclic number fields of degree 18.

  相似文献   

827.
A novel series of 5-(omega-aryloxyalkyl)oxazole derivatives was prepared and their effects on brain-derived neurotrophic factor (BDNF) production were evaluated in human neuroblastoma (SK-N-SH) cells. Syntheses were performed by construction of an oxazole ring as a key reaction. Most of the 5-(omega-aryloxyalkyl)oxazole derivatives markedly increased BDNF production in SK-N-SH cells. 4-(4-Chlorophenyl)-2-(2-methyl-1H-imidazol-1-yl)-5-[3-(2-methoxyphenoxy)propyl]-1, 3-oxazole, one of the most promising compounds, showed potent activity (EC(50)=7.9 microM) and the improvement of the motor nerve conduction velocity and the tail-flick response accompanied by a recovery of the brain-derived neurotrophic factor level in the sciatic nerve of streptozotocin (STZ)-diabetic rats.  相似文献   
828.
A stereoselective assay for the determination of tolperisone enantiomers in plasma by high performance liquid chromatography was developed. Calibration curves obtained for the enantiomers were linear over plasma concentrations of 0.1-3.0 micrograms/ml with a detection limit of 20 ng/ml. Following intravenous bolus administration of 10 mg/kg of racemic tolperisone to rats, stereoselective disposition of tolperisone enantiomers was observed, and plasma concentrations were significantly higher for l-tolperisone than for d-tolperisone at 5, 15 and 30 min after administration. When either enantiomer was administered alone to rats, both enantiomers were found in plasma, indicating that a mutual chiral inversion occurs in the body.  相似文献   
829.
A polymethacrylate derivative containing 6-cyanouracil was prepared, and its photochemical reaction was studied. The 6-cyanouracil derivative was found to show high reactivity for the photochemiccal reaction. The photochemical-reaction product was identified as a cyclobutanetype photodimer, and the photodimer was formed in high yield even from the monomeric compound of 6-cyanouracil under UV irradiation in low concentration. The quantum yield of the photodimerization of the 6-cyanouracil derivative was greater than that of the thymine derivative. The photodimerization of the 6-cyanouracil derivative could not be quenched by usual triplet quenchers, but was found to be quenched by the polymeric derivative of adenine, suggesting a specific interaction.  相似文献   
830.
The photodimerization reaction between thymine bases in thymine-grafted poly-D - and poly-L -lysine derivatives was studied in an alkaline, aqueous, buffered solution. It was found that the helix content of the polymers changes by photodimerization. The result was discussed in terms of conversion, the rate of photodimerization, and the helix content of the polymers.  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