全文获取类型
收费全文 | 270303篇 |
免费 | 3345篇 |
国内免费 | 945篇 |
专业分类
化学 | 147939篇 |
晶体学 | 4249篇 |
力学 | 10521篇 |
综合类 | 18篇 |
数学 | 28947篇 |
物理学 | 82919篇 |
出版年
2018年 | 2262篇 |
2017年 | 2149篇 |
2016年 | 3957篇 |
2015年 | 2843篇 |
2014年 | 3972篇 |
2013年 | 11309篇 |
2012年 | 8298篇 |
2011年 | 10087篇 |
2010年 | 6841篇 |
2009年 | 6655篇 |
2008年 | 9112篇 |
2007年 | 9164篇 |
2006年 | 8767篇 |
2005年 | 7899篇 |
2004年 | 7230篇 |
2003年 | 6364篇 |
2002年 | 6127篇 |
2001年 | 7815篇 |
2000年 | 5986篇 |
1999年 | 4779篇 |
1998年 | 3779篇 |
1997年 | 3761篇 |
1996年 | 3711篇 |
1995年 | 3532篇 |
1994年 | 3396篇 |
1993年 | 3251篇 |
1992年 | 3841篇 |
1991年 | 3593篇 |
1990年 | 3499篇 |
1989年 | 3509篇 |
1988年 | 3419篇 |
1987年 | 3434篇 |
1986年 | 3182篇 |
1985年 | 4298篇 |
1984年 | 4321篇 |
1983年 | 3535篇 |
1982年 | 3780篇 |
1981年 | 3699篇 |
1980年 | 3572篇 |
1979年 | 3804篇 |
1978年 | 3993篇 |
1977年 | 3813篇 |
1976年 | 3742篇 |
1975年 | 3487篇 |
1974年 | 3397篇 |
1973年 | 3435篇 |
1972年 | 2280篇 |
1968年 | 2481篇 |
1967年 | 2790篇 |
1966年 | 2457篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
Dr. H. Schmieg Prof. Dr. P. Vielsack 《Archive of Applied Mechanics (Ingenieur Archiv)》1987,57(6):446-458
Übersicht Betrachtet wird ein zwangserregtes Zweikörpersystem mit wechselnden Bindungen infolge trockener Reibung. Stationäre Bewegungen werden als Grenzfall instationärer Einschwingvorgänge berechnet. Abhängig von den Systemparametern ergeben sich drei typische Bewegungsformen. Ihnen entsprechen dauernde Haftzustände, wechselnde Haft-Gleitzustände oder dauernde Gleitzustände an der Berührfläche beider Körper.
Intermittant constraints in a two-body-system with dry friction
Summary An externally excited two-body-system with intermittant constraints due to dry friction is considered. Stationary motions are calculated as limit cases of instationary transients. Depending on the parameters of the system, three typical modes are of interest. These correspond to permanent sticking, slipstick behaviour, or to permanent slipping in the contact surface of the bodies, respectively.相似文献
33.
34.
We initiate a program to study certain recent problems in non-compact coset CFT by the BRST approach. We derive a reduction formula for the BRST cohomology by making use of a twisting by highest weight modules. As illustrations, we apply the formula to the bosonic string model and a rank one non-compact coset model [DPL]. Our formula provides a completely new approach to non-compact coset construction.Partially supported by NSF Grant DMS-8703581 相似文献
35.
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
36.
High-temperature series expansions of the susceptibility and second moment to 15th order are calculated for zero external field on the linear chain (LC), plane square (PSQ), simple cubic (SC), and body-centered cubic (BCC) lattices. Checks for specific models against pertinent work in the literature are detailed. 相似文献
37.
The effects of surface preparation and illumination on electric parameters of Au/InSb/InP(100) Schottky diode were investigated, in the later diode InSb forms a fine restructuration layer allowing to block In atoms migration to surface. In order to study the electric characteristics under illumination, we make use of an He-Ne laser of 1 mW power and 632.8 nm wavelength. The current-voltage I(VG), the capacitance-voltage C(VG) measurements were plotted and analysed. The saturation current Is, the serial resistance Rs and the mean ideality factor n are, respectively, equal to 2.03 × 10−5 A, 85 Ω, 1.7 under dark and to 3.97 × 10−5 A, 67 Ω, 1.59 under illumination. The analysis of I(VG) and C(VG) characteristics allows us to determine the mean interfacial state density Nss and the transmission coefficient θn equal, respectively, to 4.33 × 1012 eV−1 cm−2, 4.08 × 10−3 under dark and 3.79 × 1012 eV−1 cm−2 and 5.65 × 10−3 under illumination. The deep discrete donor levels presence in the semiconductor bulk under dark and under illumination are responsible for the non-linearity of the C−2(VG) characteristic. 相似文献
38.
Nonlinear Theory of Spectra of Thermally Stimulated Currents in Complex Crystals with Hydrogen Bonds
Tonkonogov M. P. Ismailov Zh. T. Timokhin V. M. Fazylov K. K. Kalitka V. A. Baimukhanov Z. K. 《Russian Physics Journal》2002,45(10):1008-1018
The nonlinear theory of thermally stimulated depolarization currents is developed. The theory explains the processes of hetero- and homocharge relaxation in complex crystals with hydrogen bonds and allows the relaxation oscillator parameters to be calculated using the quadratic approximation for the external electric field. 相似文献
39.
G. Tiana M.H. Jensen K. Sneppen 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,29(1):135-140
A feedback mechanism that involves the proteins p53 and mdm2, induces cell death as a controlled response to severe DNA damage.
A minimal model for this mechanism demonstrates that the response may be dynamic and connected with the time needed to translate
the mdm2 protein. The response takes place if the dissociation constant k between p53 and mdm2 varies from its normal value. Although it is widely believed that it is an increase in k that triggers the response, we show that the experimental behaviour is better described by a decrease in the dissociation
constant. The response is quite robust upon changes in the parameters of the system, as required by any control mechanism,
except for few weak points, which could be connected with the onset of cancer.
Received 8 May 2002 / Received in final form 9 July 2002 Published online 17 September 2002 相似文献
40.
Z. V. Golubenko A. S. Kamzin L. P. Ol’khovik M. M. Khvorov Z. I. Sizova V. P. Shabatin 《Physics of the Solid State》2002,44(9):1698-1702
Magnetization and remagnetization processes in a close-packed nanodispersed barium hexaferrite powder sample in the magnetically stable state were analyzed. Reversibility effects were discussed in terms of interparticle interaction. Judging from the magnetization curve and the parameters characterizing remagnetization irreversibility, the sample under study is a model system of small Stoner-Wohlfarth particles. 相似文献