全文获取类型
收费全文 | 514373篇 |
免费 | 21922篇 |
国内免费 | 2345篇 |
专业分类
化学 | 309490篇 |
晶体学 | 6955篇 |
力学 | 21084篇 |
综合类 | 68篇 |
数学 | 58533篇 |
物理学 | 142510篇 |
出版年
2023年 | 4695篇 |
2021年 | 5006篇 |
2020年 | 7407篇 |
2019年 | 5448篇 |
2018年 | 6147篇 |
2016年 | 11589篇 |
2015年 | 9822篇 |
2014年 | 11339篇 |
2013年 | 25177篇 |
2012年 | 19062篇 |
2011年 | 21181篇 |
2010年 | 16181篇 |
2009年 | 15930篇 |
2008年 | 19755篇 |
2007年 | 19820篇 |
2006年 | 18596篇 |
2005年 | 16841篇 |
2004年 | 15176篇 |
2003年 | 13399篇 |
2002年 | 13245篇 |
2001年 | 14666篇 |
2000年 | 11241篇 |
1999年 | 8779篇 |
1998年 | 7124篇 |
1997年 | 6991篇 |
1996年 | 7100篇 |
1995年 | 6406篇 |
1994年 | 6217篇 |
1993年 | 6053篇 |
1992年 | 6589篇 |
1991年 | 6514篇 |
1990年 | 6084篇 |
1989年 | 5893篇 |
1988年 | 6099篇 |
1987年 | 5809篇 |
1986年 | 5662篇 |
1985年 | 7888篇 |
1984年 | 8047篇 |
1983年 | 6641篇 |
1982年 | 7210篇 |
1981年 | 7025篇 |
1980年 | 6669篇 |
1979年 | 6939篇 |
1978年 | 7096篇 |
1977年 | 7204篇 |
1976年 | 7213篇 |
1975年 | 6883篇 |
1974年 | 6843篇 |
1973年 | 6959篇 |
1972年 | 4683篇 |
排序方式: 共有10000条查询结果,搜索用时 539 毫秒
961.
Aldehydes undergo smooth conjugate addition to α,β-unsaturated ketones in the presence of 5-(2-hydroxyethyl)-1,3-thiazolium halides and DBU adsorbed onto the surface of basic alumina under microwave irradiation and solvent-free conditions to afford 1,4-diketones in enhanced yields and reduced reaction times compared to conventional methods. 相似文献
962.
In this paper, we prove convergence rates for spherical spline Hermite interpolation on the sphere Sd−1 via an error estimate given in a technical report by Luo and Levesley. The functionals in the Hermite interpolation are either point evaluations of pseudodifferential operators or rotational differential operators, the desirable feature of these operators being that they map polynomials to polynomials. Convergence rates for certain derivatives are given in terms of maximum point separation. 相似文献
963.
In this paper, a generalized anti–maximum principle for the second order differential operator with potentials is proved. As an application, we will give a monotone iterative scheme for periodic solutions of nonlinear second order equations. Such a scheme involves the Lp norms of the growth, 1 ≤ p ≤ ∞, while the usual one is just the case p = ∞. 相似文献
964.
965.
966.
Parabolic Capacity and Soft Measures for Nonlinear Equations 总被引:2,自引:0,他引:2
We first introduce, using a functional approach, the notion of capacity related to the parabolic p-Laplace operator. Then we prove a decomposition theorem for measures (in space and time) that do not charge the sets of null capacity. We apply this result to prove existence and uniqueness of renormalized solutions for nonlinear parabolic initial boundary-value problems with such measures as right-hand side. 相似文献
967.
Until recently, simple and reliable high repetition-rate laser sources with nanosecond pulses much shorter than from conventional A-O Q-switch lasers were not available. However over the past 2 years we have developed such lasers based on proprietary fast E-O switching technology, which allows designs delivering 1 ns pulses and subnanosecond jitter for good synchronisation. The technology provides pulses with multi-kW peak power and repetition-rates to >100 kHz.Most recently, the performance of these short pulse lasers has been developed further by implementing oscillator/amplifier (master oscillator and power amplifier, MOPA) technology which increases the output to >1 W average power. Here we report on a simple model that has been used to predict the performance of the CW pumped Nd:YVO4 amplifier used in the MOPA laser. The model is based on the well-known expressions for the saturated gain applying to laser pulses, but more usually applied to pulse-excited amplifiers. The model is shown to allow a good interpretation of the amplifier behaviour for kHz pulses and to be a useful tool for predicting the performance of the MOPA laser. 相似文献
968.
The operating principles, design, and characteristics of an ion source with a cold magnetron cathode and magnetic plasma compression are described. The source is intended for the injector of a linear proton accelerator. 相似文献
969.
L. M. Vasilyak M. N. Vasil’ev S. P. Vetchinin D. N. Polyakov V. E. Fortov 《Journal of Experimental and Theoretical Physics》2003,96(3):440-443
The action of an electron beam on ordered dust structures in glow and low-pressure RF discharges was studied experimentally. The electron beam produces destruction and dynamic displacement of the dust structure. In the center of a dust structure, an electron beam with a low electron energy (tens of eV) at currents up to 1 mA caused structural disordering and “melting” in the region of its action but did not excite external crystal regions. Local action of an electron beam with a high electron energy (25 keV) and a beam current above 10 mA caused deformation of the whole dust structure and shifted it in the horizontal direction so that it was carried away from the RF discharge zone. The effect of dust structure displacements can be used to locally remove particles from a plasma. 相似文献
970.