全文获取类型
收费全文 | 1749篇 |
免费 | 85篇 |
国内免费 | 5篇 |
专业分类
化学 | 1283篇 |
晶体学 | 29篇 |
力学 | 21篇 |
数学 | 89篇 |
物理学 | 417篇 |
出版年
2023年 | 13篇 |
2022年 | 18篇 |
2021年 | 10篇 |
2020年 | 25篇 |
2019年 | 31篇 |
2018年 | 19篇 |
2017年 | 12篇 |
2016年 | 47篇 |
2015年 | 35篇 |
2014年 | 45篇 |
2013年 | 71篇 |
2012年 | 115篇 |
2011年 | 133篇 |
2010年 | 59篇 |
2009年 | 56篇 |
2008年 | 125篇 |
2007年 | 90篇 |
2006年 | 102篇 |
2005年 | 107篇 |
2004年 | 98篇 |
2003年 | 88篇 |
2002年 | 62篇 |
2001年 | 28篇 |
2000年 | 23篇 |
1999年 | 18篇 |
1998年 | 18篇 |
1997年 | 12篇 |
1996年 | 21篇 |
1995年 | 21篇 |
1994年 | 21篇 |
1993年 | 11篇 |
1992年 | 29篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 18篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 10篇 |
1985年 | 20篇 |
1984年 | 15篇 |
1983年 | 14篇 |
1982年 | 9篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1978年 | 11篇 |
1977年 | 15篇 |
1976年 | 12篇 |
1975年 | 13篇 |
1973年 | 9篇 |
排序方式: 共有1839条查询结果,搜索用时 46 毫秒
41.
Asner DM Athanas M Bliss DW Brower WS Masek G Paar HP Gronberg J Korte CM Kutschke R Menary S Morrison RJ Nakanishi S Nelson HN Nelson TK Qiao C Richman JD Roberts D Ryd A Tajima H Witherell MS Balest R Cho K Ford WT Lohner M Park H Rankin P Smith JG Alexander JP Bebek C Berger BE Berkelman K Bloom K Browder TE Cassel DG Cho HA Coffman DM Crowcroft DS Dickson M Drell PS Dumas DJ Ehrlich R Elia R Gaidarev P Garcia-Sciveres M Gittelman B Gray SW Hartill DL Heltsley BK Henderson S Jones CD 《Physical review D: Particles and fields》1996,53(3):1039-1050
42.
A bioassay-directed fractionation of the cytotoxic constituents of the Japanese sea hare Dolabella auricularia resulted in the isolation of two 35-membered depsipeptides dolastatin G (1) and nordolastatin G (2), which showed cytotoxicity against HeLa S(3) cells with IC(50) values of 1.0 and 5.3 &mgr;g/mL, respectively. The gross structures of these substances were established by spectroscopic analysis including 2D NMR techniques. The absolute stereostructure of 1 was determined by chiral HPLC analysis of amino acid components obtained from acid hydrolysis of 1 and by the enantioselective syntheses of two degradation products arising from polyketide portions. Nordolastatin G (2) is a congener that has the same absolute stereochemistry as that of 1. 相似文献
43.
44.
Bean A Gronberg J Kutschke R Menary S Morrison RJ Nelson H Richman J Tajima H Schmidt D Sperka D Witherell M Procario M Yang S Daoudi M Ford WT Johnson DR Lingel K Lohner M Rankin P Smith JG Alexander JP Bebek C Berkelman K Besson D Browder TE Cassel DG Coffman DM Drell PS Ehrlich R Galik RS Garcia-Sciveres M Geiser B Gittelman B Gray SW Hartill DL Heltsley BK Honscheid K Jones C Kandaswamy J Katayama N Kim PC Kreinick DL Ludwig GS Masui J Mevissen J Mistry NB Ng CR Nordberg E O'Grady C 《Physical review letters》1993,70(2):138-142
45.
Miura T Goto K Waragai H Matsumoto H Hirose Y Ohmae M Ishida HK Satoh A Inazu T 《The Journal of organic chemistry》2004,69(16):5348-5353
The Bfp-OH, a novel fluorous protecting reagent, was able to be easily prepared. The Bfp group was readily introduced to a carbohydrate, removed in high yield, and recyclable after cleavage. The use of the Bfp group made it possible to synthesize a pentasaccharide by minimal column chromatography purification. Each synthetic intermediate was able to be easily purified only by simple fluorous-organic solvent extraction and monitored by TLC, NMR, and MS. 相似文献
46.
Katayama H Satoh K Takeuchi M Deguchi-Tawarada M Oda Y Nagasu T 《Rapid communications in mass spectrometry : RCM》2003,17(10):1071-1078
Improvement of in-gel digestion efficiency is highly desirable for one- or two-dimensional gel electrophoretic separation and mass spectrometric (MS) analysis in proteomics, because the resultant increases in sequence coverage and MS signal intensity lead to higher confidence in protein identification. Here an optimized in-gel digestion system, in combination with thin-gel separation and negative staining in a high-throughput format using 96-well plates, is described. The combination of negative staining and protein separation on a 0.9 mm thick gel showed a clear improvement in in-gel digestion efficiency in comparison with the more typical protocols such as the combination of silver staining and a 1.0 mm gel. In addition, the use of 96-well plates to increase throughput did not decrease the efficiency of this strategy when the stirring of the gel pieces in processes such as destaining, washing, gel-shrinking and peptide extraction was performed by sonication instead of shaking the plates. This procedure was optimized and applied to identify proteins of the postsynaptic density fraction; 105 proteins were identified after SDS-PAGE separation. 相似文献
47.
Rapid synthesis of oligosaccharide moieties of globotriaosylceramide using fluorous protective group
Tsuyoshi MiuraToshiyuki Inazu 《Tetrahedron letters》2003,44(9):1819-1821
The use of the Bfp (bisfluorous chain type propanoyl) group as a fluorous protective group made it possible to rapidly synthesize galabiose and the Gb3 oligosaccharide derivatives by a simple fluorous-organic extraction purification. The fluorous oligosaccharide synthesis using the Bfp group is an excellent strategic alternative to solid phase oligosaccharide synthesis, and removes some of the disadvantages of the solid phase method. 相似文献
48.
49.
Inorganic-organic hybrids have been synthesized by incorporation of the inorganic component of Ti(OC2H5)4 into the organic polymer of ethyl cellulose. The inorganic-organic hybrids did not dissolve in toluene used as a solvent for the starting materials. The ethanol was formed as a by-product of the alcoholysis condensation reaction between Ti(OC2H5)4 and ethyl cellulose. These results suggest that ethoxy groups of Ti(OC2H5)4 react with hydroxy groups of ethyl cellulose to form cross-linking bonds of –O–Ti–O–. The reaction of Ti(OC2H5)4 with ethyl cellulose was further investigated by Fourier transform infrared (FT-IR) spectroscopy. The FT-IR spectroscopic experiments revealed that the Ti–O bond state of Ti(OC2H5)4 was changed by refluxing a toluene solution of Ti(OC2H5)4 with ethyl cellulose. The inorganic-organic hybrids have an interesting dielectric property; their dielectric constant is higher than that of ethyl cellulose and that of a simple mixture of TiO2 and ethyl cellulose. 相似文献
50.
Treatment of magnesium alkylidene carbenoids, generated from 1-chlorovinyl p-tolyl sulfoxides with isopropylmagnesium chloride at −78 °C in toluene, with 2-lithiothiophenes gave 2-alkenylated thiophenes in good to high yields. The intermediate of this reaction was found to be an alkenylmagnesium, which could be trapped with iodoalkanes and ethyl chloroformate. This procedure offers a novel and efficient one-pot synthesis of thiophenes having a disubstituted or a trisubstituted olefin at the 2-position from thiophenes in good yields. 相似文献