全文获取类型
收费全文 | 208177篇 |
免费 | 47701篇 |
国内免费 | 45656篇 |
专业分类
化学 | 91369篇 |
晶体学 | 3913篇 |
力学 | 9802篇 |
综合类 | 2686篇 |
数学 | 20099篇 |
物理学 | 84422篇 |
无线电 | 89243篇 |
出版年
2024年 | 1323篇 |
2023年 | 3202篇 |
2022年 | 5665篇 |
2021年 | 5585篇 |
2020年 | 5513篇 |
2019年 | 5953篇 |
2018年 | 5864篇 |
2017年 | 7899篇 |
2016年 | 7396篇 |
2015年 | 9829篇 |
2014年 | 11075篇 |
2013年 | 13948篇 |
2012年 | 15990篇 |
2011年 | 17178篇 |
2010年 | 20007篇 |
2009年 | 20349篇 |
2008年 | 14959篇 |
2007年 | 14010篇 |
2006年 | 13005篇 |
2005年 | 11434篇 |
2004年 | 10353篇 |
2003年 | 7681篇 |
2002年 | 7169篇 |
2001年 | 7196篇 |
2000年 | 6513篇 |
1999年 | 4629篇 |
1998年 | 3256篇 |
1997年 | 2812篇 |
1996年 | 3129篇 |
1995年 | 3448篇 |
1994年 | 3445篇 |
1993年 | 3586篇 |
1992年 | 3142篇 |
1991年 | 2638篇 |
1990年 | 2215篇 |
1989年 | 2298篇 |
1988年 | 2178篇 |
1987年 | 1371篇 |
1986年 | 1388篇 |
1985年 | 978篇 |
1984年 | 1105篇 |
1983年 | 494篇 |
1982年 | 979篇 |
1981年 | 818篇 |
1980年 | 835篇 |
1979年 | 618篇 |
1978年 | 545篇 |
1977年 | 645篇 |
1976年 | 1046篇 |
1972年 | 541篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
301.
Based on the measured transverse mass spectra ofπr-, K-, and p at the RHIC energy s()NN = 130 GeV,di-omega productions from baryon-baryon reactions in hadronic matter are studied. Results about the (ΩΩ)0+ numbershow that the deeply bound state (ΩΩ)o+ can be observed at RHIC energies. 相似文献
302.
Dielectric effect on the rf characteristics of a helical groove travelling wave tube 总被引:1,自引:0,他引:1 下载免费PDF全文
A new type of partial-dielectric-loaded helical groove slow-wave structure (SWS) for millimetre wave travelling wave tube (TWT) is presented in this paper.The radio-frequency characteristics including the dispersion properties,the longitudinal electric field distribution and the beam-wave coupling impedance of this structure are analysed.The results show that the dispersion of the helical groove circuit is weakened,the phase velocity is reduced and the position of the maximum Ez is moved from the mouth to the inside of the groove after partially filling the dielectric materials in the helical groove SWS.Therefore,the dielectric-loaded helical groove SWS is suitable for a multi-beam TWT with broad band and high gain. 相似文献
304.
Tao Liu Zuxiong Xu Zhongtao Zhao Ruzhang Ma Tiandou Hu Yaning Xie Yinghuan Guo 《中国科学A辑(英文版)》1997,40(4):395-399
The role of magnetoelastic coupling effects in nanocrystalline ferromagnets is investigated by means of high-field magnetization and Doppler-broadening spectrum measurements. For the nanocrystalline Fe73 5Cu1Nb3Si13.5B9 alloy, the results show that the pinning effects resulting from the quasidislocation dipole intensely influence the movement of domain wall; by coupling with the magnetostriction the defects-induced stress fields determine the magnetic properties at the early stage of crystallization. In view of the effective anisotropy and magnetoelastic coupling energy the optimal annealing conditions of alloys are discussed. 相似文献
305.
基于可寻址分支分配器的CATV收费系统 总被引:2,自引:1,他引:1
给出了一种基于可寻址分支分配器的CATV收费管理系统设计方案,并着重介绍了系统的工作原理及可寻址分支分配器的设计。 相似文献
306.
The distortion theorem for biholomorphic convex mappings in bounded symmetric domains are considered. Especially the distortion theorem for biholomorphic convex mappings in classical domain of type IV and two exceptional domains are given. 相似文献
307.
D. Citterio Stefan Rásonyi Ursula E. Spichiger 《Fresenius' Journal of Analytical Chemistry》1996,354(7-8):836-840
New chromoionophores have been developed, focused on NIR applications so that optode membranes may be used in monolithically integrated optical sensors. The wavelength of maximum absorbance has been estimated for a new model compound by the Pariser-Parr-Pople (PPP) method. Several cyanine type dyes have been tested as membrane chromoionophores. Membrane composition has been altered to overcome solubility problems. In this way, simple pH-sensitive optode membranes have been produced. 相似文献
308.
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
309.
In this paper we describe a method for separating a combination of a chaotic time series and a discrete-valued signal. The method uses a feedback technique stabilised using knowledge of the chaotic system and the discrete nature of the signal. It is not based on a linearization of the dynamics, and therefore, unlike previously proposed separation methods, does not require that the signal be small. Nor does it make any assumptions about the relative timescales of the signal and the chaotic time series. 相似文献
310.