全文获取类型
收费全文 | 30082篇 |
免费 | 5007篇 |
国内免费 | 4078篇 |
专业分类
化学 | 21542篇 |
晶体学 | 365篇 |
力学 | 2025篇 |
综合类 | 279篇 |
数学 | 3401篇 |
物理学 | 11555篇 |
出版年
2024年 | 105篇 |
2023年 | 548篇 |
2022年 | 1005篇 |
2021年 | 1058篇 |
2020年 | 1149篇 |
2019年 | 1081篇 |
2018年 | 971篇 |
2017年 | 891篇 |
2016年 | 1343篇 |
2015年 | 1369篇 |
2014年 | 1704篇 |
2013年 | 2092篇 |
2012年 | 2635篇 |
2011年 | 2803篇 |
2010年 | 1915篇 |
2009年 | 1877篇 |
2008年 | 2150篇 |
2007年 | 1854篇 |
2006年 | 1813篇 |
2005年 | 1445篇 |
2004年 | 1116篇 |
2003年 | 933篇 |
2002年 | 962篇 |
2001年 | 804篇 |
2000年 | 702篇 |
1999年 | 712篇 |
1998年 | 509篇 |
1997年 | 457篇 |
1996年 | 531篇 |
1995年 | 452篇 |
1994年 | 375篇 |
1993年 | 306篇 |
1992年 | 275篇 |
1991年 | 234篇 |
1990年 | 198篇 |
1989年 | 175篇 |
1988年 | 144篇 |
1987年 | 106篇 |
1986年 | 95篇 |
1985年 | 68篇 |
1984年 | 50篇 |
1983年 | 48篇 |
1982年 | 26篇 |
1981年 | 27篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1974年 | 4篇 |
1972年 | 4篇 |
1957年 | 8篇 |
1936年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Ji-Dong Lou Chun-Ling Gao Li Li Zhi-Gang Fang 《Monatshefte für Chemie / Chemical Monthly》2006,41(10):1071-1074
A new procedure for the selective oxidation of alcohols to the corresponding aldehydes and ketones with potassium permanganate
supported on aluminum silicate at room temperature under solvent-free conditions and shaking is reported. 相似文献
2.
Yuxi Zheng 《Communications in Mathematical Physics》1991,135(3):581-594
We show that the weak-L
2 limit of a sequence of solutions of the two dimensional incompressible Euler equation is still a solution, provided that a (strong) concentration set for the reduced defect measure has locally finite one dimensional Hausdorff measure in space and time. 相似文献
3.
4.
A design of diode-pumped high-efficiency Nd:YVO4/LBO red laser is reported. Using critical phase-matching (CPM) LBO, 671 nm red laser was obtained from 1342 nm light by intracavity frequency doubling. With an incident pump laser of 800 mW, using type-I and type-II CPM LBO, 97 and 52 mWTEM00 mode red laser outputs were obtained, with optical-to-optical conversion efficiencies of up to 12.1% and 6.5%, respectively. 相似文献
5.
The results of laser induced deposition of copper on polyimide substrate from copper electrolyte solution are reported. Unlike most work reported in the literatures where CW Ar+ lasers were used, a second harmonic (532 nm wavelength) Q-switch Nd:YAG laser was used for our experiments. The deposition process was conducted by laser-catalyzing of the polyimide surface and subsequent photothermal-accelerated reduction of copper-complex ions in an alkaline reducing environment. The characteristics of the deposited copper line were investigated in terms of laser beam scanning speed, and the number of scans. The surface morphology and chemical composition of the deposited copper were analyzed using field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDX). The optimum processing conditions have been identified. The copper deposit was found to adhere well to the substrate. 相似文献
6.
7.
This paper undertakes a systematic treatment of the low regularity local wellposedness and ill-posedness theory in Hs andHs for semilinear wave equations with polynomial nonlinearity in u and (e)u. This ill-posed result concerns the focusing type equations with nonlinearity on u and (e)tu. 相似文献
8.
Hong-Xing Zheng Dao-Yin Yu 《International Journal of Infrared and Millimeter Waves》2005,26(9):1343-1353
In this paper, a very useful numerical technique has been developed for analyzing the transient characteristics of a planar-spiral inductor on-chip. A locally conformal technique and an alternating-direction implicit scheme are applied to the finite-difference time-domain method. A formulation for solving three dimensional Maxwell’s equations is proposed. Using the proposed method, various parameters of the planar-spiral inductors have been analyzed and an equivalent circuit, which includes frequency-independent circuit elements, has been introduced. Highly computational efficiency is implemented. Numerical results show excellent agreement with the measured data over a wide frequency range. 相似文献
9.
A stochastic approximation algorithm for estimating multichannel coefficients is proposed, and the estimate is proved to converge to the true parameters a.s. up-to a constant scaling factor. The estimate is updated after receiving each new observation, so the output data need not be collected in advance. The input signal is allowed to be dependent and the observation is allowed to be corrupted by noise, but no noise statistics are used in the estimation algorithm. 相似文献
10.
Mattias Edn Jekabs Grins Zhijian Shen Zheng Weng 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,169(2):1
Using enhancement of the 27Al central-transition magnetization by applying RAPT prior to 27Al → 29Si cross-polarization, we demonstrate fast acquisition of 29Si one-dimensional MAS and two-dimensional 27Al–29Si HETCOR spectra on a new sialon phase Ba2Al3Si9N13O5. 相似文献