全文获取类型
收费全文 | 457380篇 |
免费 | 5930篇 |
国内免费 | 1600篇 |
专业分类
化学 | 252829篇 |
晶体学 | 6843篇 |
力学 | 19037篇 |
综合类 | 11篇 |
数学 | 51727篇 |
物理学 | 134463篇 |
出版年
2018年 | 2980篇 |
2016年 | 5692篇 |
2015年 | 4531篇 |
2014年 | 6265篇 |
2013年 | 19986篇 |
2012年 | 14413篇 |
2011年 | 18074篇 |
2010年 | 11498篇 |
2009年 | 11366篇 |
2008年 | 16571篇 |
2007年 | 16926篇 |
2006年 | 16254篇 |
2005年 | 14864篇 |
2004年 | 13434篇 |
2003年 | 11916篇 |
2002年 | 11722篇 |
2001年 | 13847篇 |
2000年 | 10638篇 |
1999年 | 8523篇 |
1998年 | 6803篇 |
1997年 | 6674篇 |
1996年 | 6707篇 |
1995年 | 6127篇 |
1994年 | 5878篇 |
1993年 | 5574篇 |
1992年 | 6433篇 |
1991年 | 6177篇 |
1990年 | 5876篇 |
1989年 | 5758篇 |
1988年 | 5952篇 |
1987年 | 5701篇 |
1986年 | 5452篇 |
1985年 | 7676篇 |
1984年 | 7782篇 |
1983年 | 6391篇 |
1982年 | 6824篇 |
1981年 | 6842篇 |
1980年 | 6493篇 |
1979年 | 6763篇 |
1978年 | 6943篇 |
1977年 | 6833篇 |
1976年 | 6720篇 |
1975年 | 6500篇 |
1974年 | 6296篇 |
1973年 | 6487篇 |
1972年 | 3922篇 |
1971年 | 3041篇 |
1968年 | 3381篇 |
1967年 | 3284篇 |
1966年 | 2991篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
H. Maekawa K. Tsubakihara A. Ohnishi 《The European Physical Journal A - Hadrons and Nuclei》2007,33(3):269-272
We study the hyperon-nucleus potential with distorted-wave impulse wave approximation (DWIA) using the Green's function method.
In order to include the nucleon and hyperon potential effects in Fermi averaging, we introduce the local optimal momentum
approximation of target nucleons. We can describe the quasi-free Λ , Σ and Ξ production spectra in a better way than in the
standard Fermi-averaged t -matrix treatments. 相似文献
962.
963.
964.
965.
Jan J. Slawianowski 《International Journal of Theoretical Physics》1998,37(1):411-420
We formulated some criticisms of the Diracequation and its Clifford-algebraic philosophy; inparticular, we show that, within a general-relativisticcontext, they seem to contain hidden action-at-distance concepts. We suggest a new model based on thefour-component Klein-Gordon equation locally invariantunder the U(2,2) gauge group. The usual Dirac equationis then obtained as a certain approximation. The geometrodynamical sector shows reasonablecorrespondence with general relativity. 相似文献
966.
A. J. Seeds 《Optical and Quantum Electronics》1993,25(4):219-229
The low-loss, wide-bandwidth capability of optoelectronic systems makes them attractive for the transmission and processing of microwave signals. This paper considers the technology required for generating, transmitting and detecting microwave modulated optical signals. It also reviews the developing research area of directly optically controlled microwave devices, and describes some typical microwave optoelectronic systems applications. 相似文献
967.
Sr incorporation in the molecules of amorphous calcium phosphate, apatitic tricalcium phosphate, hydroxyapatite, octacalcium phosphate and dicalcium phosphate dihydrate was investigated. The concentration of Sr ranged from 225 to 1010 μ g / g, i.e. it overlapped with the physiological range of Sr concentrations in human bone. The leading experimental technique was extended X-ray absorption fine structure (EXAFS) at the Sr K edge. Results of these studies demonstrated the following: (1) Sr incorporation in the calcium phosphates is compound-dependent, (2) the coordination of incorporated Sr atoms in the Ca-P molecules is similar to that of Ca atoms, but interatomic distances are ≈0.015 nm larger, (3) in apatitic tricalcium phosphate, hydroxyapatite and octacalcium phosphate lattices Sr atoms may occupy selected Ca sites, which was not the case for dicalcium phosphate dihydrate, (4) in the apatite lattice Sr atoms are coordinated by 6 PO4 tetrahedrals and (5) EXAFS spectra at the K edge of the incorporated Sr may be used to distinguish the structures of amorphous calcium phosphate, dicalcium phosphate dihydrate as well as apatite and its derivatives (apatitic tricalcium phosphate, octacalcium phosphate). 相似文献
968.
U. Weisbrod R. Gutschke J. Knoth H. Schwenke 《Fresenius' Journal of Analytical Chemistry》1991,341(1-2):83-86
Summary Single layers and layer systems on diverse substrates were measured by Total Reflection X-Ray Fluorescence (TXRF) spectrometry. The angular dependence of the fluorescence intensities at grazing incidence allows the elemental composition, density and thickness of the layers to be evaluated using model calculations. 相似文献
969.
970.
Isothermal vapor-liquid equilibrium (VLE) data, at 25° C were determined by a saturation method for each of the six methanol or methyl acetate binary systems with dichloromethane, chloroform, and 1,2-trans-dichloroethylene. The experimental data satisfy the Redlich-Kister consistency test, and were correlated with five Gibbs free energy models. All the binary mixtures of methanol with the chlorinated compounds exhibit strong positive deviations from ideality while the mixtures of methyl acetate with the chlorinated compounds present negative deviations from ideal behavior.Communicated at the Festsymposium celebrating Dr. Henry V. Kehiaian's 60th birthday, Clermont-Ferrand, France, 17–18 May 1990. 相似文献