全文获取类型
收费全文 | 688篇 |
免费 | 41篇 |
专业分类
化学 | 570篇 |
晶体学 | 10篇 |
力学 | 23篇 |
数学 | 5篇 |
物理学 | 121篇 |
出版年
2023年 | 7篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 23篇 |
2015年 | 23篇 |
2014年 | 18篇 |
2013年 | 32篇 |
2012年 | 37篇 |
2011年 | 44篇 |
2010年 | 22篇 |
2009年 | 22篇 |
2008年 | 40篇 |
2007年 | 28篇 |
2006年 | 28篇 |
2005年 | 26篇 |
2004年 | 24篇 |
2003年 | 19篇 |
2002年 | 25篇 |
2001年 | 18篇 |
2000年 | 21篇 |
1999年 | 12篇 |
1997年 | 6篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 13篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 17篇 |
1983年 | 14篇 |
1982年 | 13篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 10篇 |
1977年 | 14篇 |
1976年 | 7篇 |
1975年 | 10篇 |
1974年 | 7篇 |
1973年 | 5篇 |
1972年 | 4篇 |
排序方式: 共有729条查询结果,搜索用时 31 毫秒
171.
172.
It was established by chemical degradation that RhCl3·3H2O catalyzed tritiation with HTO occurred with virtually 100% regioselectivity at the ortho-positions of benzamide as well as various anilides and benzoic acid. While tritiation has not been found in the alkyl C–H bond in anilide molecules, in the present experiments tritium was incorporated into the active methylene group of -phenylacetamide. This finding suggests that the present tritiation occurs more readily at polar C-–H+ bonds than at nonpolar ones in accordance with previous results. 相似文献
173.
Kawamura K Horikiri H Hayakawa J Seki C Yoshizawa K Umeuchi H Nagase H 《Chemical & pharmaceutical bulletin》2004,52(6):670-674
Chemical syntheses of three kinds of potential metabolites of TRK-820, a potent kappa-opioid receptor agonist, were described. One of the potential metabolites 2, 17-N-dealkylated TRK-820, was synthesized starting from noroxycodone through 8 steps in 21% total yield. Glucuronidation of intermediate 10 and compound 1, the free base of TRK-820, was carried out stereoselectively to give 3-O-beta-D-glucuronides 15 and 16 in good yields, respectively. Syntheses of potential conjugated metabolites 3 and 4 were accomplished through 10 steps and 2 steps in 11% and 43% total yields, respectively. Among the potential metabolites of TRK-820, compounds 2 and 4 were identified as metabolites in human hepatocytes. The results of pharmacological studies of compounds 2, 3, and 4 are described. 相似文献
174.
A novel ABA-type triblock copolymer, where A and B correspond to azobenzene (Az) containing polymethacrylate and poly(ethylene oxide) (PEO), respectively, was synthesized by atom transfer radical polymerization. Langmuir-Blodgett monolayers showed characteristic microphase separation structures depending on the isomerization state of the Az unit. The trans-to-cis isomerization induced an anisotropic elongation of the domain of the Az polymer parallel to the rod maintaining the width. Thus, successful photocontrol of nanostructures formed by the block copolymer in the two dimensions was performed. A plausible model for the Az packing and PEO conformation is proposed. 相似文献
175.
Treatment of thiol esters 1 with zinc reagent 2 in the presence of a small amount (相似文献
176.
Kazuhiro Tsuji Michio Sorai Hiroshi Suga Syüzö Seki 《Molecular Crystals and Liquid Crystals》2013,570(3-4):305-317
Abstract The heat capacity of HBAF has been measured between 15 K and 385 K. Four phase transitions were found at 328.07 K (crystal-smectic B); 330.33 K (smectic B-smectic A); 334.88 K (smectic A-nematic); and 336.33 K (nematic-isotropic liquid), respectively. The enthalpies and entropies of these transitions were determined to be 23.22 kJ mol?1/70.7 JK?1 mol?1; 3.05/9.2; 3.41/10.2; and 1.17/3.5, respectively. The total transition entropy of HBAF agreed well with those previously reported for the present homologues. The standard thermodynamic functions were estimated up to 385 K. The heat capacity curve of HBAF in the transition region had a close resemblance to that of p-n-hexyloxybenzylideneamino-p'-chlorobenzene. The entropies of the smectic A-nematic and nematicisotropic liquid transitions were compared with those theoretically derived by McMillan. The smectic B-smectic A transition entropy was interpreted in terms of order-disorder phase transition associated with the orientation of molecule. 相似文献
177.
178.
179.
180.