全文获取类型
收费全文 | 4035篇 |
免费 | 119篇 |
国内免费 | 21篇 |
专业分类
化学 | 2952篇 |
晶体学 | 42篇 |
力学 | 47篇 |
数学 | 182篇 |
物理学 | 952篇 |
出版年
2023年 | 22篇 |
2022年 | 32篇 |
2021年 | 30篇 |
2020年 | 46篇 |
2019年 | 61篇 |
2018年 | 36篇 |
2017年 | 38篇 |
2016年 | 75篇 |
2015年 | 74篇 |
2014年 | 84篇 |
2013年 | 186篇 |
2012年 | 202篇 |
2011年 | 222篇 |
2010年 | 126篇 |
2009年 | 123篇 |
2008年 | 220篇 |
2007年 | 225篇 |
2006年 | 239篇 |
2005年 | 187篇 |
2004年 | 201篇 |
2003年 | 166篇 |
2002年 | 148篇 |
2001年 | 101篇 |
2000年 | 75篇 |
1999年 | 51篇 |
1998年 | 38篇 |
1997年 | 39篇 |
1996年 | 53篇 |
1995年 | 60篇 |
1994年 | 40篇 |
1993年 | 52篇 |
1992年 | 58篇 |
1991年 | 42篇 |
1990年 | 32篇 |
1989年 | 36篇 |
1988年 | 44篇 |
1987年 | 37篇 |
1986年 | 24篇 |
1985年 | 74篇 |
1984年 | 61篇 |
1983年 | 41篇 |
1982年 | 53篇 |
1981年 | 47篇 |
1980年 | 45篇 |
1979年 | 40篇 |
1978年 | 39篇 |
1977年 | 40篇 |
1976年 | 37篇 |
1975年 | 32篇 |
1973年 | 34篇 |
排序方式: 共有4175条查询结果,搜索用时 31 毫秒
31.
32.
Yamada K Harada Y Miyamoto T Isobe R Higuchi R 《Chemical & pharmaceutical bulletin》2000,48(1):157-159
A new ganglioside molecular species, HPG-7 (1) was obtained from the polar fraction of the chloroform/methanol extract of the sea cucumber, Holothuria pervicax. On the basis of chemical and spectroscopic evidence, the structure of 1 was determined, and the major component was 1-O-[alpha-L-fucopyranosyl-(1-->4)-(N-acetyl-alpha-D-neuraminosyl) - (2-->11)-(N-glycolyl-alpha-D-neuraminosyl)-(2-->4)-(N-acetyl -alpha-D- neuraminosyl)-(2-->6)-beta-D-glucopyranosyl]-(2S,3S,4R)-2-[(2R)-2- hydroxytetracosanoylamino]-14-methyl-hexadecane-1,3,4-triol. This is the first report on the isolation and structure elucidation of trisialo-ganglioside from sea cucumber. 1 showed neuritogenic activity toward the rat pheochromocytoma cell line, PC-12 cell. 相似文献
33.
34.
Sachiko Yamada Keiko Nakayama Hiroaki Takayama Toshimasa Shinki Tatsuo Suda 《Tetrahedron letters》1984,25(30):3239-3242
(25)-25,26-Dihydroxy-23-oxovitamin D3 was synthesized efficiently and stereoselectively, and it was converted enzymatically to (25)-1α,25,26-trihydroxy-23-oxovitamin D3, a putative metabolite of 1α,25-dihydroxyvitamin D3. The spectral and chemical properties of (25)-25,26-dihydroxy-23-oxovitamin D3 and its 1α,hydroxylated derivative disagree with those reported for the isolated metabolite. 相似文献
35.
36.
37.
38.
39.
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
40.
A poly(N-isopropylacrylamide) (PNIPAAm)-like biodegradable thermosensitive polydepsipeptide, poly[Glc-Asn(N-isopropyl)], was synthesized by introducing an isopropyl amide group into poly[Glc-Asn]. Poly[Glc-Asn(N-isopropyl)] was degraded in vitro by cleavage of the ester bonds in the main chain in water at room temperature. The non-toxic nature of the polymer and its degradation products, coupled with a cloud point at 29 degrees C in water, make this polymer attractive for biomedical implant applications. 相似文献