全文获取类型
收费全文 | 368330篇 |
免费 | 3990篇 |
国内免费 | 1217篇 |
专业分类
电工技术 | 5761篇 |
综合类 | 2464篇 |
化学工业 | 56220篇 |
金属工艺 | 16497篇 |
机械仪表 | 11551篇 |
建筑科学 | 8955篇 |
矿业工程 | 2385篇 |
能源动力 | 7815篇 |
轻工业 | 29306篇 |
水利工程 | 4412篇 |
石油天然气 | 7416篇 |
武器工业 | 16篇 |
无线电 | 40435篇 |
一般工业技术 | 72438篇 |
冶金工业 | 53818篇 |
原子能技术 | 7774篇 |
自动化技术 | 46274篇 |
出版年
2021年 | 2098篇 |
2018年 | 17701篇 |
2017年 | 16610篇 |
2016年 | 13605篇 |
2015年 | 3046篇 |
2014年 | 4443篇 |
2013年 | 12189篇 |
2012年 | 9847篇 |
2011年 | 18289篇 |
2010年 | 15534篇 |
2009年 | 13982篇 |
2008年 | 15433篇 |
2007年 | 16306篇 |
2006年 | 7932篇 |
2005年 | 8455篇 |
2004年 | 7873篇 |
2003年 | 7656篇 |
2002年 | 7133篇 |
2001年 | 6586篇 |
2000年 | 6345篇 |
1999年 | 6279篇 |
1998年 | 14796篇 |
1997年 | 11050篇 |
1996年 | 8606篇 |
1995年 | 6530篇 |
1994年 | 5924篇 |
1993年 | 5796篇 |
1992年 | 4492篇 |
1991年 | 4462篇 |
1990年 | 4284篇 |
1989年 | 4302篇 |
1988年 | 4265篇 |
1987年 | 3598篇 |
1986年 | 3596篇 |
1985年 | 4164篇 |
1984年 | 3966篇 |
1983年 | 3620篇 |
1982年 | 3422篇 |
1981年 | 3558篇 |
1980年 | 3423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 13 毫秒
991.
Matrix metalloproteinases are thought to be key players in the remodelling activity of cells associated with both physiological and pathological processes. They share a relatively conserved structure with a number of identifiable modules linked to their specific functions. The structure of the individual domains of a number of matrix metalloproteinases have now been elucidated. Here we review these data in the light of complementary studies on the behaviour of these enzymes in biological systems. In particular we focus on the C-terminal hemopexin-like domain which has intriguingly specific roles in individual matrix metalloproteinases. 相似文献
992.
Capital cost correlations are given for oil-water separators, equalization basins, primary clarifiers, clarifiers and clarifier mechanisms, reverse osmosis unit, ultrafiltration units, gravity filters and miroscreens. Data are included for raw sewage, intermediate and recirculation pumping stations and for preliminary treatment (or bar screens, grit removal, overflow and bypass chamber and Parshall flume), for grit removal, comminution and gas stripping. The correlations are accurate to ± 30%, expressed in Canadian dollars and adjusted to a Marshall and Swift value of 1000. Details as to what components are included in the cost are given. Data are given for the labour and material costs to create a working process module. For inflation indices, a critique of the Engineering News Record, EPA small city, Marshall and Swift, Chemical Engineering and Southam inflation indices suggested that the Marshall and Swift index is most appropriate for the construction and process equipment studied here. Concerning the currency exchange, for the equipment and processes in this study, equipment costs the same whether expressed directly in US or Canadian dollars. To put the current data into perspective, several hundred sources of cost data were analyzed. The major correlations are compared, on a consistent basis, with current data. 相似文献
993.
G. Kleer E. Schffer M. Bodmann J. Kraft Y. Qiang H. Haberland 《Materialwissenschaft und Werkstofftechnik》1998,29(9):545-554
Hard and wear resistant coatings for the moulding and embossing of glasses at elevated temperatures Hard and wear resistant coatings of Titanium Aluminium Nitride TiAlN were deposited on various substrates by the application of different reactive deposition processes: RF-magnetron-sputtering, ion beam-sputtering and by the energetic cluster impact (ECI) process. The deposition of the coatings was performed under variation of biasing conditions and of process parameters such as pressures and flow rates of the process gases argon and nitrogen as well as of energies of species hitting the substrate surfaces. The microstructure particularly the growth morphology of several films was investigated by pictures of film cross sections recorded by transmission electron microscopy. Residual intrinsic film stresses were analyzed by measuring deflections of substrates in an interference optical microscope before and after the deposition of the coatings. By heating coated substrates and in-situ observation of deflections at elevated temperatures dependencies of thermally induced stresses on temperatures and variations of intrinsic stresses due to changes within the films could be analyzed and related to microstructure and growth conditions. In the paper specific characteristics of the deposition processes occuring on the scale both of atoms and of clusters which may contain several thousand of atoms are described and related to microstructure, residual stress states and damaging conditions. Different contributions to residual film stresses are analyzed on the base of theoretical considerations taking into account deposition kinetics and thermomecanical properties. The significance of achieved film properties for application, i. e. for the coating of tools for the manufacturing of optical components by moulding and embossing of glasses is discussed. 相似文献
994.
We report the first case of primitive breast fibromatosis associated with a synchronous independent musculo-aponeurotic fibromatosis of the omolateral pectoralis major muscle in an otherwise healthy 29-year-old woman without clinical evidence of any genetic syndrome. The primary occurrence of the two lesions was supported by the absence of any macroscopic and microscopic connection. The present case suggests that a pre- or intraoperative frozen section diagnosis of breast fibromatosis should lead the surgeon and pathologist to exclude an independent fibromatosis of the underlying musculo-aponeurotic fascia. 相似文献
995.
996.
An unconditionally stable two-stage CMOS amplifier 总被引:1,自引:0,他引:1
This paper describes a two-stage CMOS amplifier that is stable for any capacitive load. This is achieved through the use of an optimized cascoded compensation topology. A new level shifting technique allows independent optimization of drive capability, noise and systematic offset voltage. The circuit is 0.1 mm2 in a 2 μm technology and has a quiescent current consumption of 110 μA 相似文献
997.
A memory-based processing approach to discourse comprehension emphasizes the rapid deployment of information in memory to facilitate understanding of the text that is currently being read. S. B. Greene, R. J. Gerrig, G. McKoon, and R. Ratcliff (1994) demonstrated that when a text described the reunion of 2 characters who had previously discussed a 3rd character, the accessibility of the 3rd character increased, and the use of an unheralded pronoun (R. J. Gerrig, 1986) to refer to that character was felicitous. In experiments in this article, the authors demonstrate that concepts related to the unheralded pronoun also increase in accessibility and that those concepts form associations in memory with concepts present in the discourse at the time the pronoun is used. The authors also show that the increase in accessibility for the referent of the pronoun, as well as the appropriate long-term memory associations, occurs even in the absence of the pronoun. 相似文献
998.
Concurrent engineering (CE) is a vital concept in the world of new product development, and up-to-date information about the extent of its adoption and the use of the enabling tools in the engineering industry is of great value. This article presents the data from an industry-wide survey of technical managers and analyses the significance of the information obtained. This reveals that CE is beginning to be widely applied, but there are significant differences between large and smaller companies, and between different industrial sectors 相似文献
999.
1000.
Summary We introduce a very simple model for thermally activated atomic migration on a lattice, and several techniques to handle it. For thermodynamical systems, the model can be used for simulating decomposition paths taking into account relevant metallurgical features. Close to equilibrium, the simplest mean-field approximation of the model can be linearized with respect to the departure from equilibrium; one then gets a microscopic interpretation of classical phenomenological coefficients, such as mobility, interfacial transfer coefficient, rate constants for the coupled relaxation of concentration and order fields. Further away from the equilibrium, the nonlinearities can be taken into account in a consistent way. For driven alloys, i.e. alloys submitted to external forcing, forced atomic migration is added to the model and new features emerge: the model is supported by several experimental results some of which confirmed its predictions a posteriori. 相似文献