全文获取类型
收费全文 | 1984篇 |
免费 | 64篇 |
国内免费 | 9篇 |
专业分类
化学 | 1632篇 |
晶体学 | 7篇 |
力学 | 28篇 |
数学 | 76篇 |
物理学 | 314篇 |
出版年
2023年 | 18篇 |
2022年 | 11篇 |
2021年 | 22篇 |
2020年 | 44篇 |
2019年 | 33篇 |
2018年 | 14篇 |
2017年 | 13篇 |
2016年 | 36篇 |
2015年 | 34篇 |
2014年 | 36篇 |
2013年 | 84篇 |
2012年 | 91篇 |
2011年 | 130篇 |
2010年 | 54篇 |
2009年 | 61篇 |
2008年 | 106篇 |
2007年 | 84篇 |
2006年 | 121篇 |
2005年 | 111篇 |
2004年 | 106篇 |
2003年 | 78篇 |
2002年 | 98篇 |
2001年 | 58篇 |
2000年 | 37篇 |
1999年 | 29篇 |
1998年 | 20篇 |
1997年 | 17篇 |
1996年 | 21篇 |
1995年 | 15篇 |
1994年 | 17篇 |
1993年 | 20篇 |
1992年 | 27篇 |
1991年 | 24篇 |
1990年 | 26篇 |
1989年 | 22篇 |
1988年 | 18篇 |
1987年 | 16篇 |
1986年 | 15篇 |
1985年 | 33篇 |
1984年 | 22篇 |
1983年 | 11篇 |
1982年 | 22篇 |
1981年 | 21篇 |
1980年 | 13篇 |
1979年 | 29篇 |
1977年 | 13篇 |
1976年 | 17篇 |
1975年 | 18篇 |
1974年 | 26篇 |
1973年 | 12篇 |
排序方式: 共有2057条查询结果,搜索用时 15 毫秒
1.
2.
I Kitagawa A Matsuda T Nishimura S Hirai I Yoshioka 《Chemical & pharmaceutical bulletin》1967,15(9):1435-1437
3.
An antiviral nucleoside or virazole was synthesized efficiently and regioselectively starting with benzyl cyanoformate. 相似文献
4.
The first total synthesis of (+)?3-deoxyaphidicolin, a selective inhibitor of eukaryotic DNA polymerase α, has been completed efficiently and stereoselectively starting from 1-abietic acid. 相似文献
5.
Caffeine concentration in human sweat was estimated by measuring separately the amounts of water and caffeine. After washing a finger with tap water for 15 s and waiting 2 min for drying, 70 microL aqueous ethanol solution in a small vial (0.6 mL) was used to sample for several minutes. Then 3 microL of the aliquot was used for GC/MS analysis of caffeine. As a first-order relationship between the sweat amount secreted on the left and right hands was obtained (correlation factor 0.848), the amount of sweat secretion during sampling on one hand was estimated by the value obtained on the other hand. This new indirect evaluation was used for the estimation of the amount of sweat secreted during sampling. Typical variations of caffeine concentration in sweat were demonstrated. Thirty minutes after the intake of caffeine, it was secreted in sweat, and the secretion had continued for more than 4 h. 相似文献
6.
7.
8.
Racemic 2-amino-3-(heteroaryl)propanoic acids (1), mostly with a furan or thiophene nucleus as a heteroaryl group, were synthesized in 48-94% yield by the reduction of 3-(heteroaryl)-2-(hydroxyimino)propanoic acids (5) with zinc dust and formic acid in the presence of a catalytic amount of iron dust at 60 degrees C for 2 h. Under these conditions, unfavorable hydrogenolysis of bromine on the thiophene nucleus does not occur. Traditional N-formylation of the prepared 3-(heteroaryl)alanine (1) with a mixture of formic acid and acetic anhydride afforded 2-(formylamino)-3-(heteroaryl)propanoic acids (6) in 51-95% yield. 相似文献
9.
Solid sampling technique for direct detection of condensed tannins in bark by matrix-assisted laser desorption/ionization mass spectrometry 总被引:2,自引:0,他引:2
Ishida Y Kitagawa K Goto K Ohtani H 《Rapid communications in mass spectrometry : RCM》2005,19(5):706-710
A novel method for the direct analysis of condensed tannin components in bark was developed on the basis of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) combined with a simple solid sampling technique. The MALDI mass spectra obtained from the wood (bark) powder sample clearly showed a series of peaks corresponding to the sodium ion adducts of condensed tannin oligomers up to around m/z 3000. The results indicate that the condensed tannins in the bark sample used in this work mostly consist of combinations of flavan-3-ol units such as profisetinidin (PF), prorobinetinidin (PR) and prodelphinidin (PD), at least up to 10-mers (m/z approximately 3000). 相似文献
10.
Important role of molecular permanent dipoles of the Alq3/Al interface studied from first-principles
We have studied the atomic geometries and electronic properties of the tris-(8-hydroxyquinoline) aluminum (Alq3)/Al interface using density functional calculations. The calculated interface dipoles agree reasonably well with the experiments and the origin of the interface dipole formation mainly comes from the alignment of the permanent dipoles of Alq3 molecules. The HOMO levels of the Alq3 molecules significantly depend on the orientation of the molecular permanent dipoles and the interfacial gap state observed by experiments is ascribed to the co-existence of the two orientations of the molecular dipoles. 相似文献