全文获取类型
收费全文 | 313303篇 |
免费 | 2995篇 |
国内免费 | 1346篇 |
专业分类
化学 | 152451篇 |
晶体学 | 4505篇 |
力学 | 15616篇 |
综合类 | 61篇 |
数学 | 48055篇 |
物理学 | 96956篇 |
出版年
2019年 | 1899篇 |
2018年 | 10884篇 |
2017年 | 11743篇 |
2016年 | 7526篇 |
2015年 | 3225篇 |
2014年 | 3652篇 |
2013年 | 8995篇 |
2012年 | 11725篇 |
2011年 | 21134篇 |
2010年 | 13308篇 |
2009年 | 13230篇 |
2008年 | 18793篇 |
2007年 | 22185篇 |
2006年 | 8561篇 |
2005年 | 13927篇 |
2004年 | 10109篇 |
2003年 | 9331篇 |
2002年 | 7326篇 |
2001年 | 6861篇 |
2000年 | 5371篇 |
1999年 | 3708篇 |
1998年 | 3086篇 |
1997年 | 3029篇 |
1996年 | 3189篇 |
1995年 | 2722篇 |
1994年 | 2809篇 |
1993年 | 2658篇 |
1992年 | 2895篇 |
1991年 | 2967篇 |
1990年 | 2776篇 |
1989年 | 2695篇 |
1988年 | 2648篇 |
1987年 | 2586篇 |
1986年 | 2596篇 |
1985年 | 3391篇 |
1984年 | 3466篇 |
1983年 | 2900篇 |
1982年 | 3136篇 |
1981年 | 2904篇 |
1980年 | 2699篇 |
1979年 | 2896篇 |
1978年 | 3112篇 |
1977年 | 3063篇 |
1976年 | 3124篇 |
1975年 | 2847篇 |
1974年 | 2957篇 |
1973年 | 3047篇 |
1972年 | 2357篇 |
1971年 | 1871篇 |
1968年 | 1761篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
N. I. Golovina G. N. Nechiporenko G. G. Nemtsev G. P. Dolganova V. P. Roshchupkin D. B. Lempert G. B. Manelis 《Russian Journal of Applied Chemistry》2007,80(1):24-30
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined. 相似文献
92.
Yu. V. Pokonova 《Russian Journal of Applied Chemistry》2007,80(12):2163-2164
Kinetic, sorption and selectivity properties of commercial adsorbents are improved by adding petroleum residues (tar asphaltene concentrates) 13% of whole mass. Obtained adsorbents can be used for selective extraction of nobel metals from multicomponent polymetallic solutions of heavy metals and fro sewages purification for removing arsenic. 相似文献
93.
G. Panina 《Central European Journal of Mathematics》2003,1(2):157-168
All 3-dimensional convex polytopes are known to be rigid. Still their Minkowski differences (virtual polytopes) can be flexible
with any finite freedom degree. We derive some sufficient rigidity conditions for virtual polytopes and present some examples
of flexible ones. For example, Bricard's first and second flexible octahedra can be supplied by the structure of a virtual
polytope. 相似文献
94.
95.
96.
W. L. Liang B. K. A. Ngoi L. E. N. Lim K. Venkatakrishnan C. W. Hee 《Optics & Laser Technology》2003,35(4):285-290
In this paper, integration of interference phenomenon into femtosecond laser micromachining was reported as the femtosecond laser pulses were reshaped spatially to perform ablation. The generation of circular interference pattern was demonstrated by overlapping infrared femtosecond laser pulses. The interference pattern was subsequently focused on a copper substrate to ablate microstructures of concentric circular rings. The present technique is expected to open up new applications in the areas of rapid fabrication of micro-Fresnel lenses, hybrid microlenses and lens arrays. 相似文献
97.
98.
The paper discusses the applicability of quasi-crystalline approximation to describing the thermal motion of water molecules in their normal and supercooled states. The problem is subjected to the critical analysis of experimental data on incoherent scattering of slow neutrons based on theories developed by Singwi-Sjolander [1] and Oskotsky [2] modified to duly take into account the limited applicability range of diffusion approximation. The applicability conditions of quasi-crystalline approximation are shown to be consistently satisfied only when water is in supercooled state and within a narrow temperature range above the melting temperature. 相似文献
99.
G. Montero L. Gonzlez E. Flrez M. D. García A. Surez 《Numerical Linear Algebra with Applications》2002,9(3):239-247
Parallel preconditioners are presented for the solution of general linear systems of equations. The computation of these preconditioners is achieved by orthogonal projections related to the Frobenius inner product. So, minM∈??∥AM?I∥ F and matrix M0∈?? corresponding to this minimum (?? being any vectorial subspace of ??n(?)) are explicitly computed using accumulative formulae in order to reduce computational cost when subspace ?? is extended to another one containing it. Every step, the computation is carried out taking advantage of the previous one, what considerably reduces the amount of work. These general results are illustrated with the subspace of matrices M such that AM is symmetric. The main application is developed for the subspace of matrices with a given sparsity pattern which may be constructed iteratively by augmenting the set of non‐zero entries in each column. Finally, the effectiveness of the sparse preconditioners is illustrated with some numerical experiments. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
100.
Pulse radiolysis with kinetic spectroscopic detection was applied to study the kinetics of the first steps of radiation induced polymerization of cyclohexyl acrylate and cyclohexyl methacrylate in cyclohexane solvent. The reactions were initiated by cyclohexyl radicals produced in the radiolysis of the solvent. The transient absorption spectra of the -carboxyalkyl type radicals produced in addition reaction show maxima around 300 nm. This shifts to longer wavelength with time after the pulse. This phenomenon was explained by the oligomerization reaction. From the kinetic curves average rate coefficients of termination for the oligomer radicals (2kt) were determined as a function of time elapsed after the electron pulse. The values obtained were compared with those calculated for other (acrylate and methacrylate type) monomers. 相似文献