全文获取类型
收费全文 | 329624篇 |
免费 | 1421篇 |
国内免费 | 757篇 |
专业分类
化学 | 137726篇 |
晶体学 | 4236篇 |
力学 | 21246篇 |
综合类 | 7篇 |
数学 | 70642篇 |
物理学 | 97945篇 |
出版年
2021年 | 2080篇 |
2020年 | 2218篇 |
2019年 | 2665篇 |
2018年 | 19021篇 |
2017年 | 19487篇 |
2016年 | 12720篇 |
2015年 | 3540篇 |
2014年 | 4426篇 |
2013年 | 8279篇 |
2012年 | 12603篇 |
2011年 | 25542篇 |
2010年 | 16072篇 |
2009年 | 16779篇 |
2008年 | 20669篇 |
2007年 | 25312篇 |
2006年 | 6200篇 |
2005年 | 11568篇 |
2004年 | 8850篇 |
2003年 | 9115篇 |
2002年 | 6755篇 |
2001年 | 5392篇 |
2000年 | 4283篇 |
1999年 | 3028篇 |
1998年 | 2841篇 |
1997年 | 2632篇 |
1996年 | 2596篇 |
1995年 | 2261篇 |
1994年 | 2172篇 |
1993年 | 2210篇 |
1992年 | 2200篇 |
1991年 | 2514篇 |
1990年 | 2437篇 |
1989年 | 2520篇 |
1988年 | 2413篇 |
1987年 | 2447篇 |
1986年 | 2258篇 |
1985年 | 2802篇 |
1984年 | 2828篇 |
1983年 | 2454篇 |
1982年 | 2515篇 |
1981年 | 2405篇 |
1980年 | 2222篇 |
1979年 | 2542篇 |
1978年 | 2703篇 |
1977年 | 2694篇 |
1976年 | 2814篇 |
1975年 | 2604篇 |
1974年 | 2526篇 |
1973年 | 2744篇 |
1972年 | 2207篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
951.
952.
Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, p. 2899, December, 1991. 相似文献
953.
V. D. Levchenko A. I. Morozov A. S. Sigov 《Journal of Experimental and Theoretical Physics》2002,94(5):985-991
Multilayer ferromagnet-layered antiferromagnet (Fe/Cr) structures frustrated because of roughness of interlayer boundaries were studied by mathematical modeling methods. The phase diagram of a three-layer system (plotted as film thickness versus the degree of roughness of the interfaces) was obtained, and the order parameter distributions in each phase were determined. The character of phase transitions in this system was studied. The applicability range of the Slonczewski magnetic proximity model was determined. 相似文献
954.
R. Kimmich F. Klammler V. D. Skirda I. A. Serebrennikova A. I. Maklakov N. Fatkullin 《Applied magnetic resonance》1993,4(4):425-440
Geometrical restrictions of water diffusion in different aqueous protein systems were studied using two versions of the NMR field gradient technique. The samples were aqueous systems of bovine serum albumin, gelatin and horse myoglobin at concentrations ranging from diluted solutions to almost dry powders being only partly hydrated. Hydrated protein aerogels were produced by the aid of a special preparation procedure and studied in addition. The experiments referred to the, temperature and concentration dependences of the water diffusion coefficient above and below the free-water freezing temperature. The diffusion coefficient within clusters of overlapping hydration shells is reduced by one order of magnitude compared with that of bulk water. Geometrical restrictions manifest themselves (a) by the obstruction effect observed at low protein concentrations, (b) by the topologically two-dimensional diffusion in the network of overlapping hydration shells, (c) by the percolation threshold appearing at about 15%b.w. water and (d) by the anomalous diffusion behaviour concluded from the protein aerogel study. 相似文献
955.
S. A. J. Wiegers B. Tieke U. Zeitler R. Fletcher A. K. Geim J. C. Maan M. Henini 《Czechoslovak Journal of Physics》1996,46(5):2461-2462
We have investigated the interaction of phonons with a 2DEG in the FQH regime with phonon drag thermoelectric power (TEP). We find that the TEP at filling factors with the same even denominator is identical and at other even denominator filling factors they differ only by a constant. Assuming these states to be Composite Fermions (CF), we can explain our observations by extending a zero magnetic field theory for phonon drag to the CF-phonon interaction. This analysis is further corroborated by the observed T4 dependence of the CF TEP. 相似文献
956.
V. I. Pogorelov 《Radiophysics and Quantum Electronics》1995,38(7):417-422
A general expression describing the coherent scattering indicatrix by arbitrary inhomogeneities of the medium is derived. It is shown that a universal program can be devised for calculation of such indicatrices to avoid difficulties in the analytical and experimental investigations of the media through the wave processes.Institute of Applied Geophysics, Moscow. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 7, pp. 631–638, July, 1995. 相似文献
957.
A generalized Gibbs-ensemble methodology with a fluctuating particle is used to determine the coexistence vapor-liquid densities for a square-well fluid. It is shown that the presence of the fluctuating particle in sub-states of the Markov chain of states supresses considerably density fluctuations which makes it possible to carry out simulations efficiently even for temperatures very close to the critical temperature. 相似文献
958.
The problem with unknown boundaries for a first-order semilinear hyperbolic system is studied in the case where the curve of definition of the initial conditions degenerates to a point. An existence and uniqueness theorem for a classical solution of the problem is proved for small t. 相似文献
959.
A. Sachdev R. I. Masel J. B. Adams 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1993,26(1):310-312
The embedded atom method (EAM) was used to determine the equilibrium shapes of small platinum and palladium clusters (N=5–60 atoms). The stability of various polyhedral symmetries was performed at 0K. A search for the presence of any other lower energy structures was also carried out. Pt clusters reconstructed to lower energy clusters even at the magic numbers. Pd also reconstructed to lower energy structures except at the magic number sizes where the icosahedron was found to be the most stable. 相似文献
960.
This Review discusses the synthesis and characterization by our Group of new antibiotics belonging to the class of penicillins, cephalosporins and rifamycins with ferrocenyl and 1, 1′-ferrocenilene residues in the molecule. As reactants for 6-aminopenicillanic acid (6-APA) and 7-aminocephalosporanic acid (7-ACA) the following were used: 1, 1-bis(chlorocarbonyl)ferrocene, ferrocenyl sulfochloride, 1, 1′-ferrocenylenedisulfochloride and thioglycolic acids S-modified with ferrocene. In the synthesis of rifamycins, the hydrazides of the thioglycolic acids, S-modified with ferrocene, were employed as nucleophilic agents. The synthesized intermediates were characterized by elemental analysis, TLC, IR, UV and 1H NMR spectra. The characterization of new antibiotics was made by TLC, IR and UV spectral analysis. Biological activity was tested on Gram-negative and Gram-positive bacteria. Good activity is reported towards Gram-positive bacteria in the case of derivatives containing residues of thioglycolic acid S-modified with ferrocene, the antibacterial activity being similar to that of amoxicillin, carbenicillin and cephalothin. All compounds are inactive towards Gram-negative bacteria. 相似文献