全文获取类型
收费全文 | 472946篇 |
免费 | 2927篇 |
国内免费 | 725篇 |
专业分类
化学 | 216216篇 |
晶体学 | 7098篇 |
力学 | 27156篇 |
综合类 | 5篇 |
数学 | 72212篇 |
物理学 | 153911篇 |
出版年
2021年 | 3821篇 |
2020年 | 4222篇 |
2019年 | 5026篇 |
2018年 | 12365篇 |
2017年 | 12795篇 |
2016年 | 12127篇 |
2015年 | 5129篇 |
2014年 | 8579篇 |
2013年 | 16979篇 |
2012年 | 16598篇 |
2011年 | 24266篇 |
2010年 | 17407篇 |
2009年 | 17704篇 |
2008年 | 22366篇 |
2007年 | 24458篇 |
2006年 | 14271篇 |
2005年 | 15924篇 |
2004年 | 13571篇 |
2003年 | 13149篇 |
2002年 | 12108篇 |
2001年 | 12351篇 |
2000年 | 9651篇 |
1999年 | 7120篇 |
1998年 | 6020篇 |
1997年 | 5957篇 |
1996年 | 5577篇 |
1995年 | 4999篇 |
1994年 | 5004篇 |
1993年 | 4857篇 |
1992年 | 5339篇 |
1991年 | 5744篇 |
1990年 | 5587篇 |
1989年 | 5538篇 |
1988年 | 5316篇 |
1987年 | 5397篇 |
1986年 | 4897篇 |
1985年 | 5906篇 |
1984年 | 6166篇 |
1983年 | 5121篇 |
1982年 | 5299篇 |
1981年 | 4859篇 |
1980年 | 4645篇 |
1979年 | 5383篇 |
1978年 | 5537篇 |
1977年 | 5542篇 |
1976年 | 5608篇 |
1975年 | 5241篇 |
1974年 | 5076篇 |
1973年 | 5259篇 |
1972年 | 4170篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Switching kinetics of uniaxial ferroelastic ferroelectrics (FFs) in external electric and stress fields is studied using classical theory of nucleation and growth. The stage in which the polarization and deformation reversal involves the main body of the FF and the final stage (Ostwald ripening) of the FF switching are studied with allowance for the change in the repolarization and redeformation during the phase transition. The time dependences of the repolarization and redeformation are found, and equations are derived from which the polarization current and the deformation flux, as well as their time dependence, can be calculated. The calculated main characteristics of the FF switching are compared with the experimental data for switching of Rochelle salt single crystals. 相似文献
962.
This paper reports on the results of experimental investigations into the thermal conductivity of GaS and GaSe layered semiconductor crystals in directions parallel and perpendicular to the crystal layers in the temperature range 5–300 K. Specific features of the thermal conductivity of these crystals are analyzed. 相似文献
963.
V.I. Fernández A. Iucci C.M. Naón 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):53-56
We present an extension of the Tomonaga-Luttinger model in which left and right-moving particles have different Fermi velocities.
We derive expressions for one-particle Green's functions, momentum-distributions, density of states, charge compressibility
and conductivity as functions of both the velocity difference ε and the strength of the interaction β. This allows us to identify
a novel restricted region in the parameter space in which the system keeps the main features of a Luttinger liquid but with
an unusual behavior of the density of states and the static charge compressibility κ. In particular κ diverges on the boundary
of the restricted region, indicating the occurrence of a phase transition.
Received 20 May 2002 / Received in final form 23 August 2002 Published online 19 November 2002 相似文献
964.
965.
The energy characteristics of an XeCl exciplex lamp with planar construction pumped by a low-pressure gas discharge are investigated
experimentally. When a discharge gap of width 2 cm and a Xe-Cl2 mixture were used, average radiation powers up to 20 mW were obtained in the wavelength interval 200–380 nm at efficiencies
of ∼0.4%. In this case the total efficiency of radiation into an angle of 4π exceeded 4%. It is shown that increasing the working pressure and using low discharge currents can lead to “point” radiation
sources.
Zh. Tekh. Fiz. 67, 43–46 (December 1997) 相似文献
966.
We propose a way of modifying the mathematical model of the nondestructive theoretical-experimental method of determining the residual stresses for a specific collection of technological conditions for welding two cylindrical glass shells. The method is based on the general theory of boundary-value problems for ordinary differential equations.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 33, 1991, pp. 69–73. 相似文献
967.
Jati K. Sengupta 《The Journal of the Operational Research Society》1996,47(11):1387-1397
A method is developed here for characterizing the empirical distribution of the efficient units in data envelopment analysis. Two empirical applications illustrate the various uses of the distribution approach. One involves the cost frontier which exhibits increasing returns to scale and the other involves a dynamic production frontier, where technological change causes a shift of the production frontier over time. 相似文献
968.
J.-L. Hainaut V. Englebert J. Henrard J.-M. Hick D. Roland 《Applied Categorical Structures》1996,3(1-2):9-45
This paper analyzes the requirements that CASE tools should meet for effective database reverse engineering (DBRE), and proposes
a general architecture for data-centered applications reverse engineering CASE environments. First, the paper describes a
generic DBMS-independent DBRE methodology, then it analyzes the main characteristics of DBRE activities in order to collect
a set of desirable requirements. Finally, it describes DB-MAIN, an operational CASE tool developed according to these requirements.
The main features of this tool that are described in this paper are its unique generic specification model, its repository,
its transformation toolkit, its user interface, the text processors, the assistants, the methodological control and its functional
extensibility. Finally, the paper describes five real-world projects in which the methodology and the CASE tool were applied.
This is a heavily revised and extended version of “Requirements for Information System Reverse Engineering Support” by J.-L.
Hainaut, V. Englebert, J. Henrard, J.-M. Hick, D. Roland, which first appeared in the Proceedings of the Second Working Conference
on Reverse Engineering, IEEE Computer Society Press, pp. 136–145, July 1995. This paper presents some results of the DB-MAIN
project. This project is partially supported by the Région Wallonne, the European Union, and by a consortium comprising ACEC-OSI (Be), ARIANE-II (Be), Banque UCL (Lux), BBL (Be), Centre de recherche public H.
Tudor (Lux), CGER (Be), Cockerill-Sambre (Be), CONCIS (Fr), D'Ieteren (Be), DIGITAL, EDF (Fr), EPFL (CH), Groupe S (Be), IBM,
OBLOG Software (Port), ORIGIN (Be), Ville de Namur (Be), Winterthur (Be), 3 Suisses (Be). The DB-Process subproject is supported
by the Communauté Fran?aise de Belgique. 相似文献
969.
970.