全文获取类型
收费全文 | 1733篇 |
免费 | 78篇 |
国内免费 | 3篇 |
专业分类
化学 | 1378篇 |
晶体学 | 16篇 |
力学 | 17篇 |
数学 | 75篇 |
物理学 | 328篇 |
出版年
2023年 | 15篇 |
2022年 | 19篇 |
2021年 | 10篇 |
2020年 | 30篇 |
2019年 | 34篇 |
2018年 | 22篇 |
2017年 | 14篇 |
2016年 | 46篇 |
2015年 | 42篇 |
2014年 | 48篇 |
2013年 | 76篇 |
2012年 | 104篇 |
2011年 | 147篇 |
2010年 | 60篇 |
2009年 | 51篇 |
2008年 | 127篇 |
2007年 | 88篇 |
2006年 | 117篇 |
2005年 | 111篇 |
2004年 | 99篇 |
2003年 | 79篇 |
2002年 | 73篇 |
2001年 | 44篇 |
2000年 | 30篇 |
1999年 | 21篇 |
1998年 | 10篇 |
1997年 | 16篇 |
1996年 | 13篇 |
1995年 | 12篇 |
1994年 | 16篇 |
1993年 | 9篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 8篇 |
1986年 | 11篇 |
1985年 | 28篇 |
1984年 | 15篇 |
1983年 | 13篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 6篇 |
1979年 | 18篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1975年 | 5篇 |
1974年 | 7篇 |
1973年 | 7篇 |
排序方式: 共有1814条查询结果,搜索用时 15 毫秒
1.
Tsuyoshi Kitamura 《Tetrahedron》2004,60(43):9649-9657
Synthesis of (+)-anthramycin was examined. A pyrrolobenzodiazepine skeleton could be synthesized by reductive cyclization of pyrrolidine derivative, which was obtained by enyne metathesis. The conjugated enamide ester part of (+)-anthramycin derivative was constructed by cross-metathesis. 相似文献
2.
3.
Tsuyoshi Katayama 《Queueing Systems》1992,11(3):299-306
This paper derives a conservation law for mean waiting times in a single-server multi-class service queueing system (M
X/G/1 type queue) with setup times which may be dependent on multiple customer classes and its arrival batch size by using the work decomposition property in the queueing system with vacations. 相似文献
4.
We investigate low-temperature behaviors of a system with chirality-pair interaction on a one-dimensional lattice. In the course of the investigation, we evaluate asymptotic forms of the characteristic values of the integral equation satisfied by the Mathieu functions. It turns out that the low-temperature behavior of correlation length of the chirality-pair correlation function is different from the one for the Ising model of spin ±1 but akin to the one for the Ising model of infinite spin. 相似文献
5.
6.
7.
Ryosuke Sakai Issei Otsuka Toshifumi Satoh Ryohei Kakuchi Harumi Kaga Toyoji Kakuchi 《Journal of polymer science. Part A, Polymer chemistry》2006,44(1):325-334
The asymmetric polymerization of 4′‐isocyanatobenzo‐18‐crown‐6 with the lithium amide of (S)‐(2‐methoxymethyl)pyrrolidine successfully proceeded to afford end‐functionalized poly(4′‐isocyanatobenzo‐18‐crown‐6) with (S)‐(2‐methoxymethyl)pyrrolidine (polymer 2 ). In the circular dichroism (CD) spectrum of 2 , a clear positive Cotton effect was observed in the range of 240–350 nm corresponding to the absorption of the polymer backbone, indicating that 2 partially formed a one‐handed helical structure, which was preserved by the chirality of (S)‐(2‐methoxymethyl)pyrrolidine bonding to the terminal end in 2 . In the titration experiments for the CD intensity of 2 in the presence of D ‐ and L ‐Phe·HClO4 (where Phe is phenylalanine), a small but remarkable difference was observed in the amount of the chiral guest needed for saturation of the CD intensity and in the saturated CD intensity, indicating that the extremely stable, one‐handed helical part should exist in the main chain of 2 , which was not inverted even when the unfavorable chiral guest for the predominant helical sense, L ‐Phe·HClO4, was added. In addition, helical polymer 2 exhibited a chiral discrimination ability toward racemic guests; that is, the guests were extracted from the aqueous phase into the organic phase with enantiomeric excess. The driving force of the chiral discrimination ability of 2 should certainly be attributed to the one‐handed helical structure in 2 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 325–334, 2006 相似文献
8.
9.
Anionic cycloaddition of methyl isocyanoacetate to diethoxyacetonitrile afforded methyl 5-diethoxymethylimidazole-4-carboxylate, a useful imidazole nucleus with two different functional groups. 相似文献
10.
Kiyotake Suenaga Tsuyoshi Mutou Takashi Itoh Noboru Takada Masaki Takagi Hideo Kigoshi Kiyoyuki Yamada 《Tetrahedron》2004,60(38):8509-8527
The bioassay-guided fractionation of the cytotoxic constituents of the Japanese sea hare Dollabella auricularia led to the isolation of aurilide (1), a 26-membered cyclodepsipeptide. The gross structure of 1 was established by spectroscopic analysis including 2D NMR techniques. The absolute stereostructure was determined by chiral HPLC analysis of acid hydrolysates of 1 and by the enantioselective synthesis of a degradation product arising from a dihydroxylated fatty acid portion. The enantioselective synthesis of 1 was achieved in 12% overall yield (16 steps) and confirmed the absolute stereostructure of 1. The cytotoxicity of 1 was evaluated using a synthetic sample, which was found to exhibit potent cytotoxicity against HeLa S3 cells with an IC50 of 0.011 μg/mL. Further biological and pharmacological studies of 1 have been carried out by using synthetic 1. 相似文献