全文获取类型
收费全文 | 39784篇 |
免费 | 5863篇 |
国内免费 | 5438篇 |
专业分类
化学 | 20724篇 |
晶体学 | 973篇 |
力学 | 3666篇 |
综合类 | 635篇 |
数学 | 9106篇 |
物理学 | 15981篇 |
出版年
2024年 | 53篇 |
2023年 | 445篇 |
2022年 | 835篇 |
2021年 | 911篇 |
2020年 | 1120篇 |
2019年 | 967篇 |
2018年 | 977篇 |
2017年 | 1295篇 |
2016年 | 1558篇 |
2015年 | 1284篇 |
2014年 | 1911篇 |
2013年 | 3212篇 |
2012年 | 2320篇 |
2011年 | 2683篇 |
2010年 | 2408篇 |
2009年 | 2801篇 |
2008年 | 2757篇 |
2007年 | 2908篇 |
2006年 | 2665篇 |
2005年 | 2159篇 |
2004年 | 1974篇 |
2003年 | 1757篇 |
2002年 | 1496篇 |
2001年 | 1359篇 |
2000年 | 1247篇 |
1999年 | 1090篇 |
1998年 | 1005篇 |
1997年 | 851篇 |
1996年 | 774篇 |
1995年 | 645篇 |
1994年 | 592篇 |
1993年 | 456篇 |
1992年 | 456篇 |
1991年 | 310篇 |
1990年 | 236篇 |
1989年 | 227篇 |
1988年 | 179篇 |
1987年 | 156篇 |
1986年 | 115篇 |
1985年 | 125篇 |
1984年 | 123篇 |
1983年 | 58篇 |
1982年 | 129篇 |
1981年 | 85篇 |
1980年 | 71篇 |
1979年 | 95篇 |
1978年 | 50篇 |
1977年 | 40篇 |
1976年 | 25篇 |
1973年 | 29篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
M. D. Srinivas 《Pramana》2003,60(6):1137-1152
We derive an optimal bound on the sum of entropic uncertainties of two or more observables when they are sequentially measured
on the same ensemble of systems. This optimal bound is shown to be greater than or equal to the bounds derived in the literature
on the sum of entropie uncertainties of two observables which are measured on distinct but identically prepared ensembles
of systems. In the case of a two-dimensional Hilbert space, the optimum bound for successive measurements of two-spin components,
is seen to be strictly greater than the optimal bound for the case when they are measured on distinct ensembles, except when
the spin components are mutually parallel or perpendicular 相似文献
102.
V. Balek T. Mitsuhashi I.M. Bountseva H. Haneda Z. Malek J. Šubrt 《Journal of Sol-Gel Science and Technology》2003,26(1-3):185-189
The diffusion structural analysis (DSA) was used to characterize microstructure changes of hydrous titania gel films under in situ conditions of heating. TG and DTA were used in order to elucidate the processes controlling the formation of anatase film during heating of hydrous titania gel film. The annealing of porosity and near surface structure defects of the dehydrated titania films was indicated by DSA in the temperature range 255–700°C as the decrease of radon release rate. It was demonstrated that the annealing was enhanced on heating in oxygen in comparison with heating in argon. The DSA experimental results were compared with model curves describing the radon diffusion mobility and the annealing of radon diffusion paths. 相似文献
103.
Karl Gustafson 《Numerical Linear Algebra with Applications》2004,11(7):649-659
Given the operator product BA in which both A and B are symmetric positive‐definite operators, for which symmetric positive‐definite operators C is BA symmetric positive‐definite in the C inner product 〈x, y〉C? This question arises naturally in preconditioned iterative solution methods, and will be answered completely here. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
104.
105.
106.
The melting mechanism of polymer crystals is proposed. It is assumed that the melting happens due to forming supervacancies. This mechanism leads the appearance of anisotropic phase of a melt. It is shown that two phases—anisotropic and isotropic—can exist in polymer melts. 相似文献
107.
Summary The meaning of linear absorbing boundary conditions for periodic water waves in elliptical approaches is discussed. It is
found that the direction of propagation of the waves must be known for reliable boundary conditions and that the energy dissipation
of waves running parallel to a boundary in general cannot be modelled in the framework of a linear theory.
Work presented at the Euromech Colloquium 240 on ?Dispersive waves in dissipative fluids?, Bologna, August 30–September 2,
1988. 相似文献
108.
Summary We have estimated and measured the daily thermal expansion of an oceanographic platform. This has been found negligible as
far as the calibration of a satellite altimeter is concerned. 相似文献
109.
Zhengmao Zhu 《Applied Surface Science》2005,252(2):303-310
The reactivity of the surface of poly(ethylene terephthalate) (PET) film under 172 nm UV irradiation (xenon excimer lamp) towards nitrogen-borne 1-octene, n-nonane and heptafluorodecene vapor was investigated. Materials receiving from 0 to 24 J/cm2 of UV were examined by X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectroscopy (ToF/SIMS), water and mineral oil contact angle measurement and atomic force microscopy (AFM). A uniform nanoscale layer developed on PET surface attributed to the grafting reaction between photolytically-produced polymer radicals and vapor phase molecules. 相似文献
110.
Kayll Lake 《General Relativity and Gravitation》2004,36(5):1159-1169
The norms associated with the gradients of the two non-differential invariants of the Kerr vacuum are examined. Whereas both locally single out the horizons, their global behavior is more interesting. Both reflect the background angular momentum as the volume of space allowing a timelike gradient decreases with increasing angular momentum becoming zero in the degenerate and naked cases. These results extend directly to the Kerr-Newman geometry. 相似文献