全文获取类型
收费全文 | 500603篇 |
免费 | 7433篇 |
国内免费 | 1632篇 |
专业分类
电工技术 | 8620篇 |
综合类 | 357篇 |
化学工业 | 77102篇 |
金属工艺 | 18661篇 |
机械仪表 | 14711篇 |
建筑科学 | 12750篇 |
矿业工程 | 2318篇 |
能源动力 | 13014篇 |
轻工业 | 48749篇 |
水利工程 | 4988篇 |
石油天然气 | 8843篇 |
武器工业 | 21篇 |
无线电 | 59459篇 |
一般工业技术 | 95951篇 |
冶金工业 | 91253篇 |
原子能技术 | 10137篇 |
自动化技术 | 42734篇 |
出版年
2021年 | 3755篇 |
2019年 | 3458篇 |
2018年 | 5852篇 |
2017年 | 5885篇 |
2016年 | 6488篇 |
2015年 | 4420篇 |
2014年 | 7449篇 |
2013年 | 22460篇 |
2012年 | 12630篇 |
2011年 | 17646篇 |
2010年 | 14071篇 |
2009年 | 15856篇 |
2008年 | 16525篇 |
2007年 | 16405篇 |
2006年 | 14833篇 |
2005年 | 13691篇 |
2004年 | 12937篇 |
2003年 | 12677篇 |
2002年 | 12311篇 |
2001年 | 12397篇 |
2000年 | 11469篇 |
1999年 | 11983篇 |
1998年 | 28363篇 |
1997年 | 20346篇 |
1996年 | 15798篇 |
1995年 | 12014篇 |
1994年 | 10624篇 |
1993年 | 10467篇 |
1992年 | 7862篇 |
1991年 | 7553篇 |
1990年 | 7251篇 |
1989年 | 7130篇 |
1988年 | 6952篇 |
1987年 | 5792篇 |
1986年 | 5690篇 |
1985年 | 6854篇 |
1984年 | 6353篇 |
1983年 | 5769篇 |
1982年 | 5414篇 |
1981年 | 5578篇 |
1980年 | 5280篇 |
1979年 | 5093篇 |
1978年 | 5016篇 |
1977年 | 5772篇 |
1976年 | 7364篇 |
1975年 | 4490篇 |
1974年 | 4278篇 |
1973年 | 4322篇 |
1972年 | 3624篇 |
1971年 | 3347篇 |
排序方式: 共有10000条查询结果,搜索用时 16 毫秒
51.
52.
53.
C. Doga Demirhan William W. Tso Joseph B. Powell Efstratios N. Pistikopoulos 《American Institute of Chemical Engineers》2019,65(7):e16498
Current ammonia production technologies have a significant carbon footprint. In this study, we present a process synthesis and global optimization framework to discover the efficient utilization of renewable resources in ammonia production. Competing technologies are incorporated in a process superstructure where biomass, wind, and solar routes are compared with the natural gas-based reference case. A deterministic global optimization-based branch-and-bound algorithm is used to solve the resulting large-scale nonconvex mixed-integer nonlinear programming problem (MINLP). Case studies for Texas, California, and Iowa are conducted to examine the effects of different feedstock prices and availabilities. Results indicate that profitability of ammonia production is highly sensitive to feedstock and electricity prices, as well as greenhouse gas (GHG) restrictions. Under strict 75% GHG reductions, biomass to ammonia route is found to be competitive with natural gas route, whereas wind and solar to ammonia routes require further improvement to compete with those two routes. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16498 2019 相似文献
54.
Loboda P. I. Minitsky A. V. Byba Ye. G. Sysoev M. O. Radchuk S. V. 《Powder Metallurgy and Metal Ceramics》2020,58(11-12):651-656
Powder Metallurgy and Metal Ceramics - The infiltration of aluminum melts into porous metal skeletons produced by powder metallurgy methods, including 3D printing, under a pressure gradient was... 相似文献
55.
56.
The Journal of Supercomputing - Infrastructure-as-a-service container-based virtualization is gaining interest as a platform for running distributed applications. With increasing scale of cloud... 相似文献
57.
Theoretical Foundations of Chemical Engineering - A set of measures to establish the technology for manufacturing highly active sources of γ radiation with an active part from... 相似文献
58.
Gökelma Mertol Einarsrud Kristian Etienne Tranell Gabriella Friedrich Bernd 《Metallurgical and Materials Transactions B》2020,51(2):850-860
Metallurgical and Materials Transactions B - The quality requirements of aluminum products are steadily increasing, and the presence of non-metallic inclusions have a large impact on the quality of... 相似文献
59.
J. Cochard P. Léonide J. Borgomano Y. Guglielmi G. Massonnat J-P. Rolando L. Marié A. Pasquier 《Journal of Petroleum Geology》2020,43(1):75-94
Upper Barremian – Lower Aptian inner platform “Urgonian” limestones in the Mont de Vaucluse region, SE France, consist of alternating metre-scale microporous and tight intervals. This paper focuses on the influence of structural deformation on the reservoir properties of the Urgonian limestone succession in a study area near the town of Rustrel. Petrographic, petrophysical and structural data were recovered from five fully-cored boreholes, from the walls of a 100 m long underground tunnel, and from a 50 m long transect at a nearby outcrop. The data allowed reservoir property variations in the Urgonian limestones to be studied from core to reservoir scale. Eleven Reservoir Rock Types (RRTs) were identified based on petrographic features (texture, grain size), reservoir properties (porosity, permeability), and the frequency of structural discontinuities such as fractures, faults and stylolites. Tight and microporous reservoir rock types were distinguished. Tight reservoir rock types were characterised by early cementation of intergranular pore spaces and by the presence of frequent structural discontinuities. By contrast microporous reservoir rock types contained preserved intragranular microporosity and matrix permeability, but had very few structural discontinuities. Observed vertical alternations of microporous and tight rock types are interpreted to have been controlled by the early diagenesis of the Urgonian carbonates. Deformation associated with regional-scale tectonic phases, including Albian – Cenomanian “Durancian” uplift (∼105 to 96 Ma) and Pyrenean compression (∼55 to 25 Ma), resulted in the modification of the initial petrophysical properties of the Urgonian limestones. An early diagenetic imprint conditioned both the intensity of structural deformations and the associated circulations of diagenetic and meteoric fluids. Evolution of the Reservoir Rock Types is therefore linked both to the depositional conditions and to subsequent phases of structural deformation. 相似文献
60.