全文获取类型
收费全文 | 1370篇 |
免费 | 272篇 |
国内免费 | 191篇 |
专业分类
化学 | 721篇 |
晶体学 | 92篇 |
力学 | 102篇 |
综合类 | 26篇 |
数学 | 292篇 |
物理学 | 600篇 |
出版年
2023年 | 13篇 |
2022年 | 44篇 |
2021年 | 30篇 |
2020年 | 47篇 |
2019年 | 36篇 |
2018年 | 45篇 |
2017年 | 60篇 |
2016年 | 41篇 |
2015年 | 67篇 |
2014年 | 88篇 |
2013年 | 122篇 |
2012年 | 156篇 |
2011年 | 176篇 |
2010年 | 152篇 |
2009年 | 133篇 |
2008年 | 116篇 |
2007年 | 87篇 |
2006年 | 53篇 |
2005年 | 41篇 |
2004年 | 32篇 |
2003年 | 13篇 |
2002年 | 22篇 |
2001年 | 22篇 |
2000年 | 21篇 |
1999年 | 15篇 |
1998年 | 12篇 |
1997年 | 10篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1993年 | 8篇 |
1991年 | 12篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 8篇 |
1987年 | 5篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 10篇 |
1973年 | 10篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1969年 | 6篇 |
1968年 | 5篇 |
排序方式: 共有1833条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
5.
V. A. Ozhiganov A. P. Kotov L. P. Andreeva L. P. Zelenin P. V. Gel'd 《Russian Physics Journal》1991,34(5):418-421
The effect of composition and temperature on the properties of the alloy PdV-20 doped with nickel was investigated. It was established that the microhardness, electroresistivity, and the normal elasticity modulus depend nonmonotonically on the content of nickel, and also that these quantities are affected significantly by the past thermal history of the samples. The results' are discussed, taking into account the nature of their intrinsic short-range order structure.Translated from Izvestiya Vysshikh. Uchebnykh Zavedenii, Fizika, No. 5, pp. 42–46, May, 1991. 相似文献
6.
A. N. Kost L. N. Khaimov Yu. Dzhurakulov K. Kh. Khaidarov L. D. Lebedeva A. L. Kotov 《Chemistry of Heterocyclic Compounds》1975,11(11):1263-1266
2-Substituted or 2,2-disubstituted 4,6-dioxo-1,3-dioxanes, which are analogs of Meldrum's acid and were obtained by reaction of malonic acid with acetic anhydride and the appropriate carbonyl compound in the presence of sulfuric acid, exist in solution preferably in a single form according to the PMR and 13C NMR spectral data. Fluctuation of the CH2 group is not observed. The mass spectra are characteristic and are distinguished by splitting out of the carbonyl compound from the molecular ion or successive splitting out of CO2 and ketene molecules. The Meldrum acid analogs do not affect plant growth but have a depressive effect on the central nervous system of animals and low toxicity.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1482–1486, November, 1975. 相似文献
7.
8.
A. G. Kotov Yu. A. Breslav S. Ya. Pshezhetskii 《Theoretical and Experimental Chemistry》1969,5(3):236-239
The adsorption of the paramagnetic molecules of NO and NO2 by zeolites in the alkali and alkaline earth cationic forms has been studied by EPR and reflectance spectroscopic methods. The change in the EPR spectra of adsorbed nitric oxide with increase in the degree of covering of the surface of the alkali cationic form of the zeolites, and also the nature of the change in the spectra when oxygen is adsorbed on zeolites on which NO has previously been adsorbed, indicate the existence of two types of adsorption center. At low degrees of covering of the surface, on the order of 1018 g–1, as can be judged from the EPR spectra, the adsorbed NO molecule is strongly polarized and the unpaired electron is almost completely localized on the oxygen atom. At high degrees of covering, for an appreciable proportion of the NO molecules, the bond with the surface is weaker. In this case, the EPR spectra show a hyperfine structure (HFS) with a constant which changes with change in the cation in the order Li+ Na+ K+. The replacement of the singly charged Na+ by the doubly charged Ca2+ produces a marked change in the adsorption properties of the zeolite. The adsorption of NO on CaA leads not only to polarization of the adsorbed molecule but also to transfer of the electron from the nitrogen atom to the atoms of the adsorbent; this is recorded in the EPR spectrum in the form of an F-center. On further adsorption, the NO molecules are adsorbed both on the nitrogen atom and on the oxygen atom of the first molecule; thus, NO2 and N2O are formed. 相似文献
9.
Aqueous dispersions of single-wall and multiwall carbon nanotubes with designed amphiphilic polycations 总被引:1,自引:0,他引:1
Sinani VA Gheith MK Yaroslavov AA Rakhnyanskaya AA Sun K Mamedov AA Wicksted JP Kotov NA 《Journal of the American Chemical Society》2005,127(10):3463-3472
Poor solubility of single-walled and multiwalled carbon nanotubes (NTs) in water and organic solvents presents a considerable challenge for their purification and applications. Macromolecules can be convenient solubilizing agents for NTs and a structural element of composite materials for them. Several block copolymers with different chemical functionalities of the side groups were tested for the preparation of aqueous NT dispersions. Poly(N-cetyl-4-vinylpyridinium bromide-co-N-ethyl-4-vinylpyridinium bromide-co-4-vinylpyridine) was found to form exceptionally stable NT dispersions. It is suggested that the efficiency of macromolecular dispersion agents for NT solubilization correlates with the topological and electronic similarity of polymer-NT and NT-NT interactions in the nanotube bundles. Raman spectroscopy and atomic force and transmission electron microcopies data indicate that the polycations are wrapped around NTs forming a uniform coating 1.0-1.5 nm thick. The ability to wind around the NT originates in the hydrophobic attraction of the polymer backbone to the graphene surface and topological matching. Tetraalkylammonium functional groups in the side chains of the macromolecule create a cloud of positive charge around NTs, which makes them hydrophilic. The prepared dispersions could facilitate the processing of the nanotubes into composites with high nanotube loading for electronic materials and sensing. Positive charge on their surface is particularly important for biological and biomedical applications because it strengthens interactions with negatively charged cell membranes. A high degree of spontaneous bundle separation afforded by the polymer coating can also be beneficial for NT sorting. 相似文献
10.
Kotov V. V. D'yakonova O. V. Sokolova S. A. Volkov V. I. 《Russian Journal of Electrochemistry》2002,38(8):888-891
The transport of water molecules and the distribution of functional groups in polyamidoacid carboxyl-containing cation-exchange membranes based on pyromellitic acid are studied by NMR and ESR techniques. It is shown that the self-diffusion coefficients of water differ in the gel and intergel regions. Structural parameters of conducting channels in the gel regions are determined. In electrodialysis of one-component and binary solutions, polyamidoacid membranes possess higher transport numbers and separation coefficients of counterions that are less hydrated in solution. 相似文献