全文获取类型
收费全文 | 287598篇 |
免费 | 3067篇 |
国内免费 | 817篇 |
专业分类
电工技术 | 5030篇 |
综合类 | 162篇 |
化学工业 | 45411篇 |
金属工艺 | 11895篇 |
机械仪表 | 8607篇 |
建筑科学 | 6847篇 |
矿业工程 | 1835篇 |
能源动力 | 6734篇 |
轻工业 | 25905篇 |
水利工程 | 3190篇 |
石油天然气 | 7087篇 |
武器工业 | 16篇 |
无线电 | 31454篇 |
一般工业技术 | 56929篇 |
冶金工业 | 51363篇 |
原子能技术 | 7532篇 |
自动化技术 | 21485篇 |
出版年
2021年 | 2098篇 |
2018年 | 3673篇 |
2017年 | 3623篇 |
2016年 | 3905篇 |
2015年 | 2465篇 |
2014年 | 4230篇 |
2013年 | 12019篇 |
2012年 | 6828篇 |
2011年 | 9212篇 |
2010年 | 7566篇 |
2009年 | 8642篇 |
2008年 | 8929篇 |
2007年 | 8813篇 |
2006年 | 7826篇 |
2005年 | 7309篇 |
2004年 | 6801篇 |
2003年 | 6553篇 |
2002年 | 6627篇 |
2001年 | 6497篇 |
2000年 | 6176篇 |
1999年 | 6229篇 |
1998年 | 14752篇 |
1997年 | 11029篇 |
1996年 | 8567篇 |
1995年 | 6523篇 |
1994年 | 5915篇 |
1993年 | 5789篇 |
1992年 | 4479篇 |
1991年 | 4440篇 |
1990年 | 4284篇 |
1989年 | 4301篇 |
1988年 | 4256篇 |
1987年 | 3598篇 |
1986年 | 3595篇 |
1985年 | 4162篇 |
1984年 | 3965篇 |
1983年 | 3620篇 |
1982年 | 3422篇 |
1981年 | 3558篇 |
1980年 | 3422篇 |
1979年 | 3365篇 |
1978年 | 3445篇 |
1977年 | 3923篇 |
1976年 | 5037篇 |
1975年 | 3158篇 |
1974年 | 3007篇 |
1973年 | 3024篇 |
1972年 | 2651篇 |
1971年 | 2473篇 |
1970年 | 2104篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Relative neighborhood graphs and their relatives 总被引:12,自引:0,他引:12
Jaromczyk J.W. Toussaint G.T. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1992,80(9):1502-1517
Results of neighborhood graphs are surveyed. Properties, bounds on the size, algorithms, and variants of the neighborhood graphs are discussed. Numerous applications including computational morphology, spatial analysis, pattern classification, and databases for computer vision are described 相似文献
992.
Pursuing optimal solutions for large scale transmission network planning problems is a formidable task due to their combinatorial nature and also due to the nonconvexities involved. Successful approaches using hierarchical Benders decomposition incur in a high computational cost mainly due to the need to solve a large integer program (the investment sub-problem) for every Benders iteration. In this work the authors propose to use heuristics within the decomposition framework, therefore avoiding to solve to optimality each integer sub-problem. The global computational effort is substantially reduced, and allows coping with large problems that would be intractable using classical combinatorial techniques. Case studies with the 6 bus Garver test system and a reduced Southeastern Brazilian power network are presented and discussed 相似文献
993.
G Biscaldi G Vittadini R Fonte P Gabanelli R Maglio E Finozzi 《Canadian Metallurgical Quarterly》1995,17(1-6):77-82
The relationship between alcohol and work was studied in a group of 537 voluntary patients (393 male and 144 female) admitted to the department of Medicina del Lavoro, Pavia University for alcohol rehabilitation. The highest incidence of alcohol abuse was found in non-working subjects (pensioners, unemployed, housewives) although the start of excessive drinking takes place after beginning a working activity; a cause-effect relationship between these two factors can not be clearly determined, however. It is true that the stress provoked by this new condition (introduction to the work experience) can, in certain subjects, be a contributing factor in alcohol abuse. The increasingly lower age of initiation to alcohol reconfirms the need for prevention and instruction even at scholastic level. We can deduce how no working condition, low age and low education can constitute makers of risk for alcohol abuse. 相似文献
994.
G. Laguzzi R. Bisconti G. Macchi M. F. Stroosnijder 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1995,100(4):540-542
In view of the recent increased interest in chromium based materials, the thin layer activation of chromium has been studied. This paper considers relative activity as a function of depth for the deuteron induced reaction in natural chromium. The presented results are based on calculations using computer codes and experimental verification using the stacked foil technique and electropolishing of activated bulk samples. A very good agreement of the various methods was obtained. It is shown that using 10 MeV deuterons, a reasonable homogeneous activation over 120 μm can be obtained. 相似文献
995.
996.
997.
998.
G. M. Klyuchnikov I. G. Klyuchnikov 《Journal of Engineering Physics and Thermophysics》1994,67(1-2):795-799
The authors show the decisive role and special features of heat and mass transfer in the mechanism of abnormal plasticity and in formation of thermomechanical dissipative structures under large plastic strains by the examples of computer modeling of stretching of a specimen, high-pressure torsional shear in a Bridgeman chamber, and shearing strain of a material in the form of flow of a quasiviscous liquid in a channel with local heat removal via a stationary wall.Izhevsk Mechanical Institute. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 67, Nos. 1–2, pp. 127–131, July–August, 1994. 相似文献
999.
Ives J.T. Gesteland R.F. Stockham T.G. Jr. 《IEEE transactions on bio-medical engineering》1994,41(6):509-519
An automated reader for electrophoresis based DNA sequencing methods is described that provides fast and accurate sequence determination. Digitized sequencing lanes are processed with homomorphic blind deconvolution in preparation for peak detection, interlane alignment, peak refinement and base calling. Initial reads from direct blot sequencing films have error rates of about 1% at the rate of 5 nucleotides/s. Typical read lengths are 500-600 nucleotides. The described reader is a significant improvement over existing readers and could be an essential component in the sequencing efforts of the Human Genome Project 相似文献
1000.
VDD pacing follow-up is similar in pediatric and adult patients. Atrial and ventricular pacing parameters are stable during 2-year follow-up in children, and single-pass lead VDD pacing is recommended when the sinus node function is normal. 相似文献