全文获取类型
收费全文 | 699篇 |
免费 | 21篇 |
专业分类
化学 | 408篇 |
晶体学 | 4篇 |
力学 | 38篇 |
数学 | 167篇 |
物理学 | 103篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 41篇 |
2021年 | 35篇 |
2020年 | 14篇 |
2019年 | 23篇 |
2018年 | 29篇 |
2017年 | 25篇 |
2016年 | 26篇 |
2015年 | 19篇 |
2014年 | 33篇 |
2013年 | 63篇 |
2012年 | 44篇 |
2011年 | 58篇 |
2010年 | 32篇 |
2009年 | 33篇 |
2008年 | 43篇 |
2007年 | 26篇 |
2006年 | 26篇 |
2005年 | 16篇 |
2004年 | 20篇 |
2003年 | 11篇 |
2002年 | 6篇 |
2001年 | 11篇 |
2000年 | 13篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1973年 | 1篇 |
1940年 | 2篇 |
排序方式: 共有720条查询结果,搜索用时 0 毫秒
101.
102.
In this paper a laboratory-scale model for prediction of the voltage–current characteristics of wire–plate electrostatic precipitators under clean air conditions is presented and experimentally validated. The model investigates the effect of electrode configurations, wire diameter, spacing between wire electrodes, number of discharge wires and distance between collecting plates that on voltage–current characteristic of wire–plate electrostatic precipitators. Also, this paper presents a simulation model, based on the Finite Difference Method (FDM), to simulate electric conditions of wire–plate electrostatic precipitators under clean air conditions. The experimental results of some models are compared with those obtained from the simulation models. 相似文献
103.
Khaled Omrani 《Numerical Methods for Partial Differential Equations》2005,21(5):961-975
Standard Galerkin approximations, using smooth splines to solutions of the Kuramoto‐Tsuzuki equation are analyzed. The existence, uniqueness, and convergence of the fully discrete Crank‐Nicolson scheme are discussed. Furthermore, a second‐order convergent linearized Galerkin approximation are derived. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 21, 2005 相似文献
104.
Khaled Tounsi 《Comptes Rendus Mathematique》2002,334(9):783-786
We describe a large class of natural star products on the cotangent bundle of a Lie group G and we characterize these star products by integral formulae. To cite this article: K. Tounsi, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 783–786. 相似文献
105.
Abdelhamid Khaled 《Mathematische Annalen》1993,295(1):685-701
Sans résumé
相似文献
相似文献
106.
A three-dimensional silicon based nanodevice mainly consisting of two conductive silicon cantilevers was fabricated out of silicon-on-insulator material by electron beam lithography, reactive ion etching, and fluoride based wet chemical etching. One of the cantilevers is bent and sticks to the silicon substrate while the other one is freely suspended. We observed electroluminescence in the visible range when a voltage of any polarity is dropped across both levers. The measured spectra covered the range 400–950 nm peaking at about 650 nm. The current applied to the device could tune the intensity of the electroluminescence spectrum. Light powers ranging from 160 fW to some pW were measured at frequencies up to 17 kHz. The origin of the electroluminescence is discussed in comparison to porous silicon and spark-processed silicon. 相似文献
107.
This paper presents a stochastic allocation model for a sequential financial problem involving the allocation of funds to uncertain future payments. It is shown that under certain conditions the optimal allocation policies are piece-wise linear with the budget available, and that there exists an intimate relationship between these policies and the myopic policies obtained from the solution of a sequence of single-payment problems. A numerical example is provided and, finally, certain technical and methodological issues associated with a chance constraint version of the problem are discussed. 相似文献
108.
Isolation, characterization, and biological evaluation of active components of Colchicum stevenii Kunth (Colchicaceae) are described. Colchicum stevenii is an unexplored Jordanian specie with toxic reputation. Directed by brine shrimp lethality test (BST), methanolic extraction, liquid-liquid partition, preparative TLC, and semi-preparative HPLC, it resulted in the isolation of six cytotoxic compounds. The compounds, reported for the first time from this specie, are: (-)-colchicine (1), 2-demethyl-(-)-colchicine (2), (-)-cornigerine (3), beta-lumicolchicine (4), (-)-isoandrocymbine (5) and (-)-O-methylandrocymbine (6). A new, in-house developed, acidic-based reverse-phase gradient semi-preparative HPLC method for the separation of colchisides is presented here. Structural elucidation was based on spectroscopic techniques principally; 1H-NMR and low resolution EIMS. Based on BST results, reported as LC50 values in microg mL(-1) (ppm) with 95% confidence intervals, (-)-colchicine (2.5 ppm) and (-)-cornigerine (2.7 ppm) were the most potent. 相似文献
109.
We consider a viscoelastic wave equation with power nonlinearity. First, we construct a local solution by the Faedo-Galerkin approximation scheme and contraction mapping theorem. Next, we continue the local solution to the global one by a priori estimates obtained from a decreasing energy. Finally, we discuss the decay rate of the global solution by assuming that the kernel function is convex. 相似文献
110.