全文获取类型
收费全文 | 453693篇 |
免费 | 7280篇 |
国内免费 | 1079篇 |
专业分类
电工技术 | 8174篇 |
综合类 | 414篇 |
化学工业 | 70506篇 |
金属工艺 | 16633篇 |
机械仪表 | 12938篇 |
建筑科学 | 10292篇 |
矿业工程 | 2145篇 |
能源动力 | 10153篇 |
轻工业 | 43183篇 |
水利工程 | 4365篇 |
石油天然气 | 7478篇 |
武器工业 | 47篇 |
无线电 | 50602篇 |
一般工业技术 | 83957篇 |
冶金工业 | 94731篇 |
原子能技术 | 9036篇 |
自动化技术 | 37398篇 |
出版年
2021年 | 4160篇 |
2020年 | 3158篇 |
2019年 | 4095篇 |
2018年 | 6932篇 |
2017年 | 6819篇 |
2016年 | 7264篇 |
2015年 | 4866篇 |
2014年 | 7680篇 |
2013年 | 20490篇 |
2012年 | 12426篇 |
2011年 | 15822篇 |
2010年 | 12724篇 |
2009年 | 13973篇 |
2008年 | 14540篇 |
2007年 | 14538篇 |
2006年 | 12758篇 |
2005年 | 11533篇 |
2004年 | 11200篇 |
2003年 | 10824篇 |
2002年 | 10638篇 |
2001年 | 10576篇 |
2000年 | 10066篇 |
1999年 | 10592篇 |
1998年 | 29085篇 |
1997年 | 19861篇 |
1996年 | 15054篇 |
1995年 | 11137篇 |
1994年 | 9723篇 |
1993年 | 9751篇 |
1992年 | 6848篇 |
1991年 | 6477篇 |
1990年 | 6543篇 |
1989年 | 6311篇 |
1988年 | 5911篇 |
1987年 | 4996篇 |
1986年 | 5067篇 |
1985年 | 5866篇 |
1984年 | 5363篇 |
1983年 | 4770篇 |
1982年 | 4527篇 |
1981年 | 4737篇 |
1980年 | 4426篇 |
1979年 | 4143篇 |
1978年 | 4189篇 |
1977年 | 4985篇 |
1976年 | 6872篇 |
1975年 | 3639篇 |
1974年 | 3461篇 |
1973年 | 3571篇 |
1972年 | 2947篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
The interfacial tension between the molten metal and the surrounding plasma environment affects the circulation of molten
metal in the weld pool, heat transfer, and the eventual structure and properties of the weld metal. Since the effect of plasma
on the interfacial tension of molten metals is not known, interfacial tension values between low pressure argon plasma and
pure copper and iron were measured. The variables studied were temperature and the intensity of plasma emission. 相似文献
993.
The study suggests improvements in the design of new houses to conserve energy and enhance indoor thermal comfort. Summer temperature records show that a new house has an average indoor temperature of 35°C with the ambient average 31°C. The traditional house in the old city recorded 28°C for the same period. Winter temperatures in both types of houses were similar (12°C) when not occupied. Architectural features of the two houses were compared to identify those responsible for difference in the thermal performance. Larger exposed surface and window areas, higher overall heat transfer coefficient and weaker thermal coupling with the ground for the new houses seems to contribute to their inferior thermal performance. 相似文献
994.
995.
Ion-beam sputter-deposited alloy films of Co/sub 74/Fe/sub 6/B/sub 15/Si/sub 5/ and Fe/sub 75/Ni/sub 5/B/sub 15/Si/sub 5/ were examined for their magnetic and structural properties. Films were characterized by ferromagnetic resonance, vibrating sample magnetometry, and extended X-ray absorption fine structure (EXAFS) analysis. Using atomic parameters deduced from EXAFS modeling and fitting procedures, magnetic properties were calculated with no adjustable parameters. Correlation between perpendicular FMR measurements and EXAFS first-shell modeling suggests a low-temperature formation of cobalt-borides in the Co/sub 74/Fe/sub 6/B/sub 15/Si/sub 5/ alloy. Annealed Fe/sub 75/Ni/sub 5/B/sub 15/Si/sub 5/ samples did not display evidence of structural and/or magnetic instabilities until the onset of long-range crystallization near T/sub ann/=400 degrees C.<> 相似文献
996.
E. I. Panov 《Metallurgist》2006,50(5-6):330-335
A mathematical model has been constructed to describe the kinematics of the movement of metal on the surface of semifinished
products made of hypereutectic silumin alloys as they undergo rotary rolling. The model is based on the dependence of the
pitch of the helical lines of metal flow on the deformation ε of the product and the feed angle α. The pitch is minimal when ε = 50–55%, regardless of the feed angle α. The degree of deformation ε = 50–55% is optimum for ensuring that the unit number of cycles in which the semifinished product is loaded by the work rolls
is such as to produce a fine-grained structure and maximize the ductility characteristics of hypereutectic silumins.
__________
Translated from Metallurg, No. 6, pp. 57–59, June, 2006. 相似文献
997.
Nucleation of solidification in liquid droplets 总被引:2,自引:0,他引:2
Analytical and numerical methods have been developed to analyze the solidification kinetics of a mass of liquid droplets dispersed
in a fluid or solid matrix using classical nucleation theory. The resulting analytical expressions and numerical calculations
can be compared directly with calorimetric measurements of the droplet solidification exotherms to obtain information about
the nucleation mechanism. With increasing contact angle at the solid-liquid-matrix triple point, the solidification onset,
peak, and end temperatures and exothermic peak height all decrease sharply and the droplet solidification exotherms become
broader. Decreasing either the droplet radius or the number of potential catalytic nucleation sites produces a similar but
smaller effect. Distributions in droplet radius, contact angle, and nucleation sites have no effect on the solidification
peak temperature, but the droplet solidification exotherms become broader and more symmetric. The solidification onset temperature
is independent of cooling rate in the calorimeter, but the solidification peak and end temperatures decrease and the exothermic
peak height increases with increasing cooling rate. Predicted droplet solidification exotherms are in excellent agreement
with detailed experimental measurements on 10-nm-radius Cd droplets embedded in a solid Al matrix. Analytical predictions
give best-fit values of 43 deg and 430 for the contact angle and the number of potential catalytic nucleation sites per droplet,
respectively; numerical predictions give best-fit values of 43 deg and 750 for the contact angle and the number of potential
catalytic nucleation sites per droplet, respectively. 相似文献
998.
Douglas E. Chandler 《Microscopy research and technique》1991,17(3):266-293
Fertilization of the sea urchin egg is accompanied by a sequence of structural changes in the egg cortex that include exocytosis, endocytosis, and microvillar growth. This architectural reorganization is coordinated by two intracellular signals: a rapid, transient rise in cyto-solic free calcium and a slower, longer lasting increase in cytoplasmic pH. In this report we provide ultrastructural views of these events in quick-frozen eggs and discuss their relationship to the calcium and pH signals. 相似文献
999.
Modern helicopter design depends on the successful combination of materials to fulfil a very wide range of critical functions. In the past few years demands from the aerospace industry have caused considerable enhancement in the favourable properties of both polymer based materials and metals. These are discussed in connection with the progressive technical evolution of helicopters and other advanced technological products from the Westland Group. 相似文献
1000.