全文获取类型
收费全文 | 612篇 |
免费 | 38篇 |
国内免费 | 5篇 |
专业分类
化学 | 373篇 |
晶体学 | 5篇 |
力学 | 21篇 |
数学 | 69篇 |
物理学 | 187篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 9篇 |
2021年 | 48篇 |
2020年 | 24篇 |
2019年 | 21篇 |
2018年 | 30篇 |
2017年 | 19篇 |
2016年 | 44篇 |
2015年 | 28篇 |
2014年 | 34篇 |
2013年 | 53篇 |
2012年 | 39篇 |
2011年 | 49篇 |
2010年 | 26篇 |
2009年 | 25篇 |
2008年 | 13篇 |
2007年 | 18篇 |
2006年 | 21篇 |
2005年 | 24篇 |
2004年 | 15篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 3篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 10篇 |
1994年 | 7篇 |
1992年 | 5篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1966年 | 2篇 |
排序方式: 共有655条查询结果,搜索用时 15 毫秒
91.
Salman R. Salman 《Magnetic resonance in chemistry : MRC》1984,22(6):385-387
Long-range proton–proton coupling constants between the hydroxy proton and ring protons were employed to deduce the conformational preferences of 1- and 2-hydroxynaphthalene. 2,6-Dibromo-1,5-dihydroxy-naphthalene, 2-acetyl-1-hydroxynaphthalene, 1,6-dibromo-2-hydroxynaphthalene and 2-hydroxy-1-naphthaldehyde were used as model compounds. Molecular orbital calculations at the CNDO/2 and INDO level were used to calculate the energy and the long-range proton–proton coupling of different conformers of 1- and 2-hydroxynaphthalene. 相似文献
92.
93.
94.
A Raman scattering study of the pressure induced phase transition in thallium azide is discussed. The transition appears to be triggered by the softening of a mode at 33 cm?1, which is shown by a Green's function calculation to be anharmonically coupled to another mode of the same symmetry at 48 cm?1. 相似文献
95.
Choudhary MI Musharraf SG Siddiqui ZA Khan NT Ali RA Ur-Rahman A 《Chemical & pharmaceutical bulletin》2005,53(8):1011-1013
The microbial transformation of an oral contraceptive, mestranol (1) by Cunninghamella elegans yielded two hydroxylated metabolites, 6beta-hydroxymestranol (2) and 6beta,12beta-dihydroxymestranol (3). Metabolite 3 was found to be a new compound. These metabolites were structurally characterized on the basis of spectroscopic techniques. 相似文献
96.
S. R. Salman 《Magnetic resonance in chemistry : MRC》1982,19(4):181-184
The spectra of several 2-methyl-6-R-disubstituted naphthalenes (R=H, Me, I, NO2, Cl, SO2Cl, OH, OMe, COMe, Br, F and NHCOMe), have been analysed. Chemical shift and coupling constant values of these compounds are presented. The proton chemical shifts have been found to correlate with the ortho parameter, Q. 相似文献
97.
A model for multiparticle production process in high-energy hadronic collisions is proposed. In the centre of mass (CM) system
of colliding particles the target and the projectile are assumed to pass through each other sharing energies allowed by kinematical
constraints. Thus in app collision the energy associated with each is √S/2 (S being the square of the CM energy) which is taken to be the real variable that governs the number of particles produced.
In the case of hadronnucleus collisions the projectile and the target ofv nucleons lying in a (Lorentz contracted) tube pass through each other sharing energies ⋍ √S
A2, whereS
A ⋍vS. Before the final state particles emerge from these systems, the constituents of the target, i.e.,v nucleons share equally (= √S
A2v) the total energy associated with the target and become the centres from which final state particles stem out. Several results
have been discussed. 相似文献
98.
Thermal degradation of PVC in various solvents at 180° has been observed to be in the following order: benzonitrite > nitrobenzene > cyclohexanone > dioctyl phthalate > α-bromonaphthalane > decahydronaphthalene. The effect has been explained on the basis of β-eliminations of E1-type favoured by polar solvents. An inhibition in PVC degradation has been observed in nitrobenzene containing stationary hydrogen chloride gas. The deceleration in degradation by predissolved HCl has been accounted for as a Mass Law effect. 相似文献
99.
Jabbar A Tufail M Arshed W Bhatti AS Ahmad SS Akhter P Dilband M 《Isotopes in environmental and health studies》2010,46(4):495-505
In Rechna Doab, samples of the most common vegetation, perennial grass Desmostachya bipinnata (dab), were collected along with soil samples from 29 sites. Natural radioactivity of 22?Ra, 232Th/22?Ac and ??K was measured by using high purity germanium-based gamma ray spectrometer. Activity concentration levels of 22?Ra, 232Th/22?Ac and ??K in soil were found to be 46.8 ± 6.2 (36.0-57.6), 61.4 ± 5.9 (48.2-73.2) and 644.8 ± 73.9 (537.7-868.4) Bq kg?1 (dry mass), respectively, and those in vegetation were 2.74 ± 1.70 (1.00-6.39), 2.24 ± 0.59 (1.56-2.61) and 172.72±113.37 (53.14-469.24) Bq kg?1 (dry mass), respectively. The measured values of the activity concentration in vegetation are comparable with some other international data. Calculated soil to vegetation transfer factors of 22?Ra, 22?Ac and ??K were 0.06 ± 0.03 (0.02-0.14), 0.04 ± 0.01 (0.03-0.04) and 0.26 ± 0.16 (0.09-0.69). The mean outdoor absorbed dose rate in air for the area under study was determined as 8.22 nGy h?1 and the mean indoor absorbed dose rate in air was 11.52 nGy h?1. The total annual effective dose to the general public from the vegetation was found to be (0.02-0.16) mSv, which is below the recommended limit value of 1 mSv y?1 for the general public. The dab vegetation under study was found to be radiologically safe for the population and environment. 相似文献
100.
A Lanczos potential for an arbitrary Petrov type D vacuum spacetimes, using the compacted spin coefficient formalism (or GHP-formalism),
has been obtained; which in turn leads to a solution of Weyl-Lanczos equations. 相似文献