全文获取类型
收费全文 | 25618篇 |
免费 | 2122篇 |
国内免费 | 1178篇 |
专业分类
电工技术 | 3021篇 |
技术理论 | 1篇 |
综合类 | 2454篇 |
化学工业 | 2290篇 |
金属工艺 | 514篇 |
机械仪表 | 864篇 |
建筑科学 | 5549篇 |
矿业工程 | 805篇 |
能源动力 | 1376篇 |
轻工业 | 2953篇 |
水利工程 | 866篇 |
石油天然气 | 799篇 |
武器工业 | 140篇 |
无线电 | 1414篇 |
一般工业技术 | 1625篇 |
冶金工业 | 1386篇 |
原子能技术 | 228篇 |
自动化技术 | 2633篇 |
出版年
2024年 | 49篇 |
2023年 | 249篇 |
2022年 | 501篇 |
2021年 | 621篇 |
2020年 | 726篇 |
2019年 | 601篇 |
2018年 | 595篇 |
2017年 | 660篇 |
2016年 | 785篇 |
2015年 | 844篇 |
2014年 | 2125篇 |
2013年 | 1858篇 |
2012年 | 2025篇 |
2011年 | 2071篇 |
2010年 | 1534篇 |
2009年 | 1804篇 |
2008年 | 1546篇 |
2007年 | 2037篇 |
2006年 | 1549篇 |
2005年 | 1144篇 |
2004年 | 993篇 |
2003年 | 960篇 |
2002年 | 747篇 |
2001年 | 588篇 |
2000年 | 487篇 |
1999年 | 390篇 |
1998年 | 262篇 |
1997年 | 210篇 |
1996年 | 207篇 |
1995年 | 163篇 |
1994年 | 117篇 |
1993年 | 82篇 |
1992年 | 68篇 |
1991年 | 60篇 |
1990年 | 61篇 |
1989年 | 43篇 |
1988年 | 35篇 |
1987年 | 22篇 |
1986年 | 15篇 |
1985年 | 16篇 |
1984年 | 16篇 |
1983年 | 14篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1975年 | 2篇 |
1959年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
42.
43.
44.
A. K. Srivastava Ram M. Shrestha S. C. Srivastava Rabin Shrestha Dharam Paul 《国际能源研究杂志》2003,27(7):671-685
The power sector in India at present comprises of five separate regional electricity grids having practically no integrated operation in between them. This study analyses the utility planning, environmental and economical effects of integrated power sector development at the national level in which the regional electric grids are developed and operated as one integrated system. It also examines the effects of selected CO2 emission reduction targets in the power sector and the role of renewable power generation technologies in India. The study shows that the integrated development and operation of the power system at the national level would reduce the total cost including fuel cost by 4912 million $, total capacity addition by 2784 MW, while the emission of CO2, SO2 and NOx would be reduced by 231.6 (1.9%), 0.8 (0.9%), 0.4 (1.2%) million tons, respectively, during the planning horizon. Furthermore, the study shows that the expected unserved energy, one of the indices of generation system reliability, would decrease to 26 GWh under integrated national power system from 5158 GWh. As different levels of CO2 emission reduction targets were imposed, there is a switching of generation from conventional coal plants to gas fired plants, clean coal technologies and nuclear based plants. As a result the capacity expansion cost has increased. It was found that wind power plant is most attractive and economical in the Indian perspective among the renewable options considered (Solar, wind and biomass). Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
45.
C. Athanassiou G. Pekridis N. Kaklidis K. Kalimeri S. Vartzoka G. Marnellos 《International Journal of Hydrogen Energy》2007
In the present work, the prospects and trends of solid electrolyte membrane reactors (SEMRs) towards hydrogen production, are discussed. Initially, an overview of the principles, the properties and the techniques related to the usage of the SEMRs, are presented. In the following, a literature survey covering earlier and recent developments of the various methods (e.g. reforming or partial oxidation or dehydrogenation of hydrocarbons, steam electrolysis) employed in the SEMRs for the production of hydrogen, is performed. Finally, the current status of this research field is analyzed and future research topics are proposed. 相似文献
46.
浅谈建筑企业施工项目部的成本控制 总被引:1,自引:0,他引:1
指出控制工程项目的直接费用要从“四算对比”入手,介绍了施工项目的成本分析方法,阐述了施工项目内部控制的主要措施,以确保施工成本控制在计划成本范围内。 相似文献
47.
M. C. ADAMS A. MATOV D. YARAR S. L. GUPTON G. DANUSER & C. M. WATERMAN-STORER 《Journal of microscopy》2004,216(2):138-152
Fluorescent speckle microscopy (FSM) uses low levels of fluorescent proteins to create fluorescent speckles on cytoskeletal polymers in high‐resolution fluorescence images of living cells. The dynamics of speckles over time encode subunit turnover and motion of the cytoskeletal polymers. We sought to improve on current FSM technology by first expanding it to study the dynamics of a non‐polymeric macromolecular assembly, using focal adhesions as a test case, and second, to exploit for FSM the high contrast afforded by total internal reflection fluorescence microscopy (TIR‐FM). Here, we first demonstrate that low levels of expression of a green fluorescent protein (GFP) conjugate of the focal adhesion protein, vinculin, results in clusters of fluorescent vinculin speckles on the ventral cell surface, which by immunofluorescence labelling of total vinculin correspond to sparse labelling of dense focal adhesion structures. This demonstrates that the FSM principle can be applied to study focal adhesions. We then use both GFP‐vinculin expression and microinjected fluorescently labelled purified actin to compare quantitatively the speckle signal in FSM images of focal adhesions and the actin cytoskeleton in living cells by TIR‐FM and wide‐field epifluorescence microscopy. We use quantitative FSM image analysis software to define two new parameters for analysing FSM signal features that we can extract automatically: speckle modulation and speckle detectability. Our analysis shows that TIR‐FSM affords major improvements in these parameters compared with wide‐field epifluorescence FSM. Finally, we find that use of a crippled eukaryotic expression promoter for driving low‐level GFP‐fusion protein expression is a useful tool for FSM imaging. When used in time‐lapse mode, TIR‐FSM of actin and GFP‐conjugated focal adhesion proteins will allow quantification of molecular dynamics within interesting macromolecular assemblies at the ventral surface of living cells. 相似文献
48.
High crude oil prices and pollution problems have drawn attention to alternative vehicle technologies and fuels for the transportation sector. The question is: What are the benefits/costs of these technologies for society? To answer this question in a quantitative way, a web-based model (http://vehiclesandfuels.memebot.com) has been developed to calculate the societal life cycle costs, the consumer life cycle costs and the tax for different vehicle technologies. By comparing these costs it is possible to draw conclusions about the social benefit and the related tax structure. The model should help to guide decisions toward optimality, which refers to maximum social benefit. The model was applied to the case of Thailand. The life cycle cost of 13 different alternative vehicle technologies in Thailand have been calculated and the tax structure analyzed. 相似文献
49.
50.