全文获取类型
收费全文 | 1414篇 |
免费 | 62篇 |
国内免费 | 5篇 |
专业分类
化学 | 1172篇 |
晶体学 | 10篇 |
力学 | 4篇 |
数学 | 68篇 |
物理学 | 227篇 |
出版年
2023年 | 10篇 |
2022年 | 13篇 |
2021年 | 11篇 |
2020年 | 22篇 |
2019年 | 29篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 30篇 |
2015年 | 35篇 |
2014年 | 38篇 |
2013年 | 73篇 |
2012年 | 91篇 |
2011年 | 82篇 |
2010年 | 52篇 |
2009年 | 53篇 |
2008年 | 94篇 |
2007年 | 90篇 |
2006年 | 98篇 |
2005年 | 90篇 |
2004年 | 81篇 |
2003年 | 46篇 |
2002年 | 58篇 |
2001年 | 24篇 |
2000年 | 27篇 |
1999年 | 26篇 |
1998年 | 19篇 |
1997年 | 22篇 |
1996年 | 17篇 |
1995年 | 8篇 |
1994年 | 13篇 |
1993年 | 11篇 |
1992年 | 22篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1979年 | 6篇 |
1976年 | 3篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1972年 | 6篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1967年 | 5篇 |
排序方式: 共有1481条查询结果,搜索用时 31 毫秒
131.
132.
133.
We give a decomposition formula for the zeta function of a group covering of a graph. 相似文献
134.
135.
Cross-benzoin condensation catalyzed by NHC, prepared from chiral triazolium salts bearing a pyridine ring, afforded α-hydroxy ketones with reasonable chemical yields and enantioselectivities. A wide range of aliphatic and aromatic aldehydes were successfully used in the reaction. 相似文献
136.
Eisuke Ohtomi Takanori Takiue Makoto Aratono Hiroki Matsubara 《Colloid and polymer science》2010,288(12-13):1333-1339
We have performed ellipsometry and surface tensiometry at tetradecyltrimethylammonium bromide (TTAB) aqueous solution surface coexisting with tetradecane lens as a function of the molality of TTAB and the temperature under atmospheric pressure. From the theoretical analysis of the coefficient of ellipticity, it was clarified that the liquid monolayer comprising the surfactant and alkane is formed at higher surfactant concentrations by the wetting transition of tetradecane lens on the aqueous solution, and the solid monolayer is formed by lowering temperature (freezing transition). The results of the surface tension measurement support the occurrence of wetting transition and the freezing transition. A phase diagram of the wetting film was constructed by ellipsometry and surface tensiometry, of which the mixed solid monolayer had never been reported before. From the thermodynamic analysis of the phase diagram, it is also demonstrated that the TTAB surface density decreases accompanied with the freezing transition, which agrees with surface densities of TTAB calculated from surface tension vs. concentration curves. 相似文献
137.
Diastereoselectivity in the photoallylation and photoreduction of 1,1-dicyano-2-methyl-3-phenyl-1-butene by allyltrimethylsilane
in the presence of phenanthrene was dependent on the structures and stoichiometry of the added carboxylic acids. Diastereoselectivity
increased up to 72% by the addition of equimolar amount of l-lactic acid based on the alkene. 相似文献
138.
Kenshu Fujiwara Yuta Hirose Hidetoshi Kawai Takanori Suzuki 《Tetrahedron letters》2010,51(32):4263-4546
Armatol F, isolated from the red alga Chondria armata as a polyether triterpene, has a solitary oxepane (A-ring) and a fused tricyclic ether moiety (BCD-ring). The A-ring features a rare cis-relationship between the hydroxy group at the quaternary carbon C6 and the carbon chain at C7. As part of our program toward the total synthesis of armatol F, a new stereoselective method for the construction of the C6 and C7 stereocenters has been developed based on chirality-transferring Ireland-Claisen rearrangement. The A-ring skeleton has also been synthesized from the rearrangement product by a process including ring-closing olefin metathesis. 相似文献
139.
140.
K. Mizuno T. Matsubara K. Sugahara M. Ichida H. Ando T. Itoh 《Journal of luminescence》2011,131(3):506-509
A persistent hole-burning is observed in β-perylene microcrystallites, which were embedded in poly-vinyl alcohol. By laser light excitation at 22,535 cm−1 and at 10 K, the hole is found at the excitation photon energy. The mechanism of the persistent hole-burning is interpreted in terms of the resolution of microcrystallites into smaller microcrystallites. This is a novel observation of the persistent hole-burning in aromatic microcrystallites. When the specimen, which includes a hole, is annealed at high temperatures, the resolved microcrystallites restore back to the old position as had been. The β-perylene microcrystallite specimen that we have grown was as small as 1.5 nm in average diameter. They are one order smaller in number of molecules included, compared to those that have been reported on aromatic microcrystallites, anthracene for example. Due to this, we were able to observe the 0-0 transition energy, which varied according as the number of molecules involved in the microcrystallites. We also observed the 0-0 absorption (excitation) spectrum, which depends on the molecular arrays in the microcrystallites. The 0-0 transition of a single molecule in poly-vinyl alcohol matrix is anticipated to be located at 22,885 cm−1. 相似文献