全文获取类型
收费全文 | 453734篇 |
免费 | 3059篇 |
国内免费 | 1409篇 |
专业分类
化学 | 223756篇 |
晶体学 | 6698篇 |
力学 | 24038篇 |
综合类 | 16篇 |
数学 | 74118篇 |
物理学 | 129576篇 |
出版年
2020年 | 3510篇 |
2019年 | 4180篇 |
2018年 | 15852篇 |
2017年 | 15648篇 |
2016年 | 13672篇 |
2015年 | 5017篇 |
2014年 | 7451篇 |
2013年 | 16483篇 |
2012年 | 15911篇 |
2011年 | 24751篇 |
2010年 | 16530篇 |
2009年 | 16961篇 |
2008年 | 20478篇 |
2007年 | 22385篇 |
2006年 | 13036篇 |
2005年 | 12784篇 |
2004年 | 12067篇 |
2003年 | 11588篇 |
2002年 | 10507篇 |
2001年 | 10619篇 |
2000年 | 8315篇 |
1999年 | 6196篇 |
1998年 | 5381篇 |
1997年 | 5457篇 |
1996年 | 5109篇 |
1995年 | 4315篇 |
1994年 | 4472篇 |
1993年 | 4435篇 |
1992年 | 4811篇 |
1991年 | 4950篇 |
1990年 | 4732篇 |
1989年 | 4794篇 |
1988年 | 4656篇 |
1987年 | 4627篇 |
1986年 | 4431篇 |
1985年 | 5689篇 |
1984年 | 5863篇 |
1983年 | 4797篇 |
1982年 | 5062篇 |
1981年 | 4916篇 |
1980年 | 4538篇 |
1979年 | 5081篇 |
1978年 | 5171篇 |
1977年 | 5310篇 |
1976年 | 5326篇 |
1975年 | 4984篇 |
1974年 | 4896篇 |
1973年 | 5133篇 |
1972年 | 3683篇 |
1971年 | 3348篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Off-the-shell anomalous factors of the two-body Coulomb transition matrices appear in the integral form of the Faddeev second-order
nuclear-electronic amplitude, for proton-hydrogen charge transfer scattering in a typical nlm → n′l′m′ transition. A symmetric-impulse approximation (SIA) is applied to eliminate these factors and an induction method is proposed
to analytically calculate the remaining integrals. The nuclear-electronic amplitude is derived for the general case, and for
totally symmetric collisions, in terms of generalized hypergeometric functions of two variables, F
4, and of one variable, 3
F
2, respectively. The angular distribution of the second-order nuclear-electronic charge transfer amplitude shows the Thomas
mechanism as a peak or a hump for symmetric and asymmetric collisions. There also exists a peak in the forward angular distribution
of the second-order nuclear-electronic amplitude, which partly cancels the kinematic peak in the angular distribution of the
charge transfer differential cross sections. 相似文献
82.
83.
Phase synchronization in a system of three virtual-cathode microwave oscillators (vircators) simulated by coupled van der Pol oscillators is studied. The phasing dynamics of the vircators is visualized with the phase portraits of the system in the triangular coordinates. Different phasing conditions are found. 相似文献
84.
V. A. Zayats A. N. Nikolaevskii T. A. Filippenko O. P. Kniga G. A. Tikhonova 《Russian Journal of Applied Chemistry》2006,79(10):1651-1654
Specific features of the initiated oxidation of polyethylene and its low-molecular-weight analogue tridecane, associated with the occurrence of the process in the short-chain mode, were studied. 相似文献
85.
E. Kyriakopoulos 《General Relativity and Gravitation》1989,21(2):125-136
The class of previously found stationary axisymmetric perfect fluid solutions of Einstein's equations is written inh-orthogonal coordinates,h being a space-like coordinate. Matching of a big number of solutions of the class with each other seems to be possible for a proper choice of some parameters. The exterior solutions of the class are matched explicitly with interior solutions. Also, interior solutions are matched explicitly with each other. 相似文献
86.
87.
Salimgareeva V. N. Polevoi R. M. Kolesov S. V. Ostakhov S. S. Ponomareva V. A. Leplyanin G. V. 《Russian Journal of Applied Chemistry》2003,76(5):804-808
The luminescence and scintillation properties of poly(methyl methacrylate) containing 1,1,3-trimethyl-3-phenylindan were studied. 相似文献
88.
The known plant growth regulator, Al'den [1-(3,7-dimethyloctyl)-1-allylpiperidinium bromide], and also 1-(3,7-dimethyloctyl)-1-methylpiperidinium iodide were synthesized by treatment with allyl bromide and methyl iodide, respectively, of exhaustively hydrogenated 1-nerylpiperidine which was obtained by anionic telomerization of isoprene with piperidine. Various quaternary ammonium salts having a terpene sub- stituent with unnatural dimethyloctane skeleton, which effectively stimulate florification of Aster Chinensis L., were prepared by the action of alkyl halides on telomerization products derived from isoprene and piperidine or morpholine in the presence of palladium complexes. 相似文献
89.
90.
H. Okumura T. Takahagi N. Nagai S. Shingubara 《Journal of Polymer Science.Polymer Physics》2003,41(17):2071-2078
The structural change in the depth direction of a polyimide (UPILEX‐S) film treated in alkaline solution, which was a representative surface treatment used to form a seed layer for plating and to improve the adhesive strength, was analyzed by means of micro Fourier transform infrared attenuated total reflection (FTIR‐ATR) line analysis with gradient shaving preparation. The polyimide film was treated with KOH. The imide ring opened through the alkaline treatment, and the amide structure and carboxylic acid salt were formed. The attainment depth of this structural change was almost proportional to the treatment time, and it reached about 8 μm after a 30‐min treatment. The degree of structural change through the alkaline treatment was almost constant after it reached a considerably degraded stage, and the chemically changed region penetrated into the inner part of the film from the surface. An intermediate layer before the final degraded stage appeared in the treated layer, and its thickness increased with the treatment time. The region that was changed chemically by the alkaline treatment progressed to the inner part simultaneously and continuously as the treatment time increased. The combined use of gradient shaving preparation and micro FTIR‐ATR line analysis was found to be extremely effective for the depth profiling of organic materials. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2071–2078, 2003 相似文献