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   217篇
  免费   4篇
化学   135篇
晶体学   2篇
数学   45篇
物理学   39篇
  2022年   1篇
  2021年   1篇
  2018年   4篇
  2017年   1篇
  2015年   4篇
  2014年   7篇
  2013年   11篇
  2012年   11篇
  2011年   15篇
  2010年   7篇
  2009年   7篇
  2008年   16篇
  2007年   8篇
  2006年   9篇
  2005年   10篇
  2004年   9篇
  2003年   6篇
  2002年   7篇
  2001年   6篇
  2000年   7篇
  1999年   2篇
  1998年   1篇
  1997年   1篇
  1996年   3篇
  1994年   3篇
  1993年   4篇
  1992年   4篇
  1991年   6篇
  1990年   5篇
  1989年   4篇
  1988年   3篇
  1987年   8篇
  1985年   2篇
  1984年   2篇
  1983年   1篇
  1982年   4篇
  1981年   2篇
  1980年   2篇
  1979年   4篇
  1978年   3篇
  1977年   1篇
  1976年   2篇
  1974年   3篇
  1973年   1篇
  1967年   3篇
排序方式: 共有221条查询结果,搜索用时 0 毫秒
1.
Two optional routes to β-phenylnaphthalene structure are developed by introducing α- and β-styryl groups onto different positions in the benzocyclobutene ring followed by ring enlargement.  相似文献   
2.
A high magnetic field of 5 T was used to fabricate a magnetically aligned, optically anisotropic, liquid‐crystalline chitin/poly(acrylic acid) composite. The aligned mesophase was fixed by photoinitiated free‐radical polymerization. From an examination of polarized optical micrographs and an X‐ray diffraction study, a high degree of orientation of 0.70 was observed for the composite with a higher liquid‐crystalline chitin concentration (10.70 wt %); the orientation was reduced with a decreased chitin concentration at a given acrylic acid concentration. The X‐ray data for the developed composite showed a uniplanar orientation for the chitin crystallites, with its molecular long axes perpendicular to the direction of the magnetic field. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 711–714, 2003  相似文献   
3.
For the purpose of testing the spherical uniformity based on i.i.d. directional data (unit vectors) zi, i=1,…,n, Anderson and Stephens (Biometrika 59 (1972) 613–621) proposed testing procedures based on the statistics Smax=maxu S(u) and Smin=minu S(u), where u is a unit vector and nS(u) is the sum of squares of uzi's. In this paper, we also consider another test statistic Srange=SmaxSmin. We provide formulas for the P-values of Smax, Smin, Srange by approximating tail probabilities of the limiting null distributions by means of the tube method, an integral-geometric approach for evaluating tail probability of the maximum of a Gaussian random field. Monte Carlo simulations for examining the accuracy of the approximation and for the power comparison of the statistics are given.  相似文献   
4.
Abstract— The absorption and emission spectra, lifetimes and quantum yields of all-trans retinol have been examined as a function of solvent and temperature. In addition, the spectroscopy of retinyl ether and 2 other polyene alcohols have been determined. Based on the results obtained, we conclude that the singlet excited state of retinol and retinyl cther is of a forbidden character and of the type loosely called 1A-g. Retinol forms a dimer in an alkane solvent when cooling from 298 to 77 K. A general structure for the dimer is proposed.  相似文献   
5.
6.
Pyrene-azacrown ether hybrid: cation-π interaction   总被引:1,自引:0,他引:1  
A pyrene-modified lariat ether was synthesized in order to observe the cation-π interaction in solution.  相似文献   
7.
8.
TUMOR-LOCALIZING FLUORESCENT DIAGNOSTIC AGENTS WITHOUT PHOTOTOXICITY   总被引:2,自引:0,他引:2  
In order to develop tumor-localizing fluorescent diagnostic agents without phototoxicity, various heterodimers linked by some spacers between a chlorine derivative and its Mn or Cu complex were synthesized. The representative agent of them was named HAT-D01 and has a molecular formula of m -phthalyl-{[13,17-bispropanoic acid-3-ethenyl-8-formylethylidene-7-hydroxy-2,7,12,18-tetramethyl-porphyrinate]-manganese (III)}-[3'-ethenyl-8'-formylethylidene-7'-hydroxy-2',7', 12', 18'-tetramethyl-porphine-13', 17'-bispropanoyl aspartic acid]-bishydrazone.  相似文献   
9.
The diethylstilbestrol-related compounds 3,3'-dihydroxy-alpha, beta-diethyldiphenylethane (I), diethylstilbestrol (II) and hexestrol (III) showed hypotensive effects on spontaneously hypertensive rats (SHR) and antifungal activities against all Fusarium oxysporum sp. tested. As previously reported, I had strong hypotensive action on normotensive rats at the dose of 10 mg/kg, while II and III showed weak hypotensive effects on these rats at the same dose. In this work, all three compounds also had hypotensive actions on SHR at the same dose. I showed the strongest hypotensive effect (-80.0 +/- 5.0 mmHg, 10 mg/kg, i.v.) on both SHR and normotensive rats. The three compounds also had antifungal activities against five kinds of Fusarium oxysporum sp. tested. Especially, II strongly inhibited the growth of Fusarium oxysporum f. sp. raphani IFO-9972 (minimum inhibitory concentration (MIC): 1.0 micrograms/ml).  相似文献   
10.
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