全文获取类型
收费全文 | 978篇 |
免费 | 31篇 |
国内免费 | 1篇 |
专业分类
化学 | 665篇 |
晶体学 | 5篇 |
力学 | 95篇 |
数学 | 66篇 |
物理学 | 179篇 |
出版年
2023年 | 11篇 |
2022年 | 5篇 |
2021年 | 18篇 |
2020年 | 14篇 |
2019年 | 13篇 |
2018年 | 9篇 |
2017年 | 8篇 |
2016年 | 18篇 |
2015年 | 28篇 |
2014年 | 30篇 |
2013年 | 39篇 |
2012年 | 55篇 |
2011年 | 69篇 |
2010年 | 59篇 |
2009年 | 36篇 |
2008年 | 63篇 |
2007年 | 57篇 |
2006年 | 47篇 |
2005年 | 51篇 |
2004年 | 38篇 |
2003年 | 43篇 |
2002年 | 32篇 |
2001年 | 20篇 |
2000年 | 16篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 17篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 19篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 9篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1975年 | 4篇 |
1973年 | 2篇 |
排序方式: 共有1010条查询结果,搜索用时 203 毫秒
1.
The preliminary results of the hydroformylation of 2-phenylsulfonyl substituted norbornene and norbornadiene derivatives catalyzed by the unmodified Rh(CO)2acac system are presented. The reaction, occurring under standard oxo conditions, gives polyfunctionalized exo norbornene- and exo norbornanecarboxaldehydes. The effect of the phenylsulfonyl group has been evaluated: it has been found that the steric properties of the sulfonyl substituent, more than the electronic ones, influence the regioselectivity of the process. 相似文献
2.
A model is reported to foresee ,for different mirror choices, the spectral properties of a high pressure, frequency tunable, CO2 laser, operating with a non-Littrow grating mounting. The calculations show a larger frequency selectivity for not collimated plane cavities. The model is experimentally verified in a suitable high pressure laser. In particular narrowed linewidths less than 300MHz ( FWHM) are obtained. 相似文献
3.
Some bounds on the entries and on the norm of the inverse of triangular matrices with nonnegative and monotone entries are found. All the results are obtained by exploiting the properties of the fundamental matrix of the recurrence relation which generates the sequence of the entries of the inverse matrix. One of the results generalizes a theorem contained in a recent article of one of the authors about Toeplitz matrices. 相似文献
4.
5.
Domingos H. U. Marchetti 《Journal of statistical physics》1990,61(3-4):909-911
A simple argument is presented by which one can show that the critical inverse temperature
c
of a two-dimensional Coulomb gas (standard or hard-core) with activityz satisfies
, where
in the low-activity limit. Previous results yield
. 相似文献
6.
We develop the quantization of topological solitons (vortices) in three-dimensional quantum field theory, in terms of the Euclidean region functional integral. We analyze in some detail the vortices of the abelian Higgs model. If a Chern-Simons term is added to the action, the vortices turn out to be anyons, i.e. particles with arbitrary real spin and intermediate () statistics. Localization properties of the interpolating field, scattering theory and spin-statistics connection of anyons are discussed. Such analysis might be relevant in connection with the fractional quantum Hall effect and two-dimensional models of HighT
csuperconductors. 相似文献
7.
Strategically designed sample composition (SSC) is a new technique that decreases the number of analytical determinations needed in routine screening to as few as the number of original sample specimens while providing information that is specific to them. Although this new technique has been applied to environmental studies, this paper describes its first application to food safety studies. Contamination of milk samples with polychlorinated biphenyls (PCBs) was chosen as a case study to show the usefulness and potential of the SSC technique with a fast analytical procedure that involves saponification of the samples and solid-phase microextraction of the PCBs. A total of 20 sample specimens can be analyzed in 11 determinations with excellent predictions of the positive samples and the concentration levels of the contaminants. The robustness of the strategy was investigated and demonstrated. 相似文献
8.
Indolinone nitroxides undergo a homolytic substitution with aroyl oxyl radicals, leading to two isomers, 7-aroyloxy- and 5-aroyloxy-derivative, respectively, whose structures were assigned on the basis of the ESR hfccs and of the 1H NMR spectra of the corresponding amines. The presence of aroyl oxyl radicals in the reaction medium was demonstrated by thermal decomposition of benzoyl peroxide in the presence of aromatic acids. 相似文献
9.
Domenico Armenise Nicolino De Laurentis Antonia Reho Antonio Rosato Flaviano Morlacchi 《Journal of heterocyclic chemistry》2004,41(5):771-775
A series of 6‐fluoro‐4‐(5 or 7)‐chloro‐2‐(difluorobenzoyl)aminobenzothiazoles 3a‐r were prepared to investigate their potential biological activity. In this work, the results of their in vitro antifungal activity against some strains of Candida albicans are reported. It was found that some derivatives displayed antifungal activity higher than that for 3k [1a] compound already described in literature. 相似文献
10.
Giuseppe Trapani Andrea Latrofa Antonia Reho Massimo Franco Gaetano Liso 《Journal of heterocyclic chemistry》1992,29(5):1155-1159
The title compounds 3a-j together with the N-alkylacylketene S,N-acetals 12a-j were obtained by reaction of N,N'-dialkyldithiodianilines with β-ketoesters compounds. A possible reaction pathway is suggested. 相似文献