全文获取类型
收费全文 | 94336篇 |
免费 | 9973篇 |
国内免费 | 5392篇 |
专业分类
电工技术 | 20626篇 |
技术理论 | 14篇 |
综合类 | 7305篇 |
化学工业 | 9946篇 |
金属工艺 | 3489篇 |
机械仪表 | 4528篇 |
建筑科学 | 10790篇 |
矿业工程 | 2949篇 |
能源动力 | 13590篇 |
轻工业 | 2851篇 |
水利工程 | 1707篇 |
石油天然气 | 2919篇 |
武器工业 | 866篇 |
无线电 | 6700篇 |
一般工业技术 | 8751篇 |
冶金工业 | 4819篇 |
原子能技术 | 1500篇 |
自动化技术 | 6351篇 |
出版年
2024年 | 605篇 |
2023年 | 1947篇 |
2022年 | 3171篇 |
2021年 | 3507篇 |
2020年 | 3818篇 |
2019年 | 3285篇 |
2018年 | 2829篇 |
2017年 | 3429篇 |
2016年 | 3753篇 |
2015年 | 3735篇 |
2014年 | 6510篇 |
2013年 | 5973篇 |
2012年 | 6959篇 |
2011年 | 7559篇 |
2010年 | 5650篇 |
2009年 | 5781篇 |
2008年 | 5355篇 |
2007年 | 6061篇 |
2006年 | 4994篇 |
2005年 | 4015篇 |
2004年 | 3392篇 |
2003年 | 3013篇 |
2002年 | 2508篇 |
2001年 | 2192篇 |
2000年 | 1824篇 |
1999年 | 1474篇 |
1998年 | 1134篇 |
1997年 | 889篇 |
1996年 | 814篇 |
1995年 | 627篇 |
1994年 | 546篇 |
1993年 | 393篇 |
1992年 | 335篇 |
1991年 | 270篇 |
1990年 | 226篇 |
1989年 | 197篇 |
1988年 | 161篇 |
1987年 | 121篇 |
1986年 | 82篇 |
1985年 | 102篇 |
1984年 | 107篇 |
1983年 | 86篇 |
1982年 | 87篇 |
1981年 | 37篇 |
1980年 | 43篇 |
1979年 | 25篇 |
1978年 | 14篇 |
1977年 | 12篇 |
1959年 | 9篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
本文通过对中州分公司正在考虑建设的信息网建设实际情况,结合山东分公司、广西分公司取得的经验,对计量管理信息网的应用进行了探讨。 相似文献
63.
VD炉是冶金行业冶炼过程中的一种钢液脱气设备。该设备工艺复杂,运行于高温、高压状态下,对设备本身质量和施工安装质量要求严格,是我国近年来推广的冶炼工艺的重要设备系统。 相似文献
66.
67.
68.
X-ray photoelectron spectroscopy (XPS) applied to the study of fluorinated polymer surfaces presents several problems related both to peak assignment and to degradation. In this work, we analyse extensively the question of XPS peak assignments in this kind of surfaces. We conclude that in this kind of surfaces using binding energy differences between fluorine and carbon is better than using absolute binding energies. Also a useful relation between fluorine photoelectron energy vs. polymer composition expressed through the atomic ratio fluorine/carbon (F/C) was found. A protocol for data treatment is proposed and applied to a XPS study of the degradation induced by X-ray on high-density polyethylene surfaces modified by direct fluorination. Results obtained for the degradation, namely the atomic ratio F/C obtained by two different methods, combined with angle resolved X-ray photoelectron spectroscopy (ARXPS) were used to study the fluorine concentration profile in depth, producing self-consistent results. 相似文献
69.
P. S. Lawson 《Biomass & bioenergy》1992,2(1-6):319-330
In recent years it has been recognised by an increasing number of nations that there is considerable energy potential within MSW. As a result many countries have established R,D& D programmes to examine methods of exploiting this potential. The IEA's MSW Conversion Activity was set up in 1986 to provide an infrastructure for sharing information and co-ordinating work in this area internationally. This Activity was extended in 1989 and currently a total of 9 nations participate in it.
To cope with the wide scope of the area (encompassing both biological and thermal processing of MSW) the Activity was divided into three subgroups or Expert Working Groups (EWGs). Each of these dealt with a distinct area of expertise:
- 1. •Downstream effects of source separation and screening of MSW
- 2. •Sampling and analytical protocols
- 3. •Landfill gas
In addition to these groups a central secretariat based at Harwell (UK) has provided guidance, established and administered databases of contacts and produced a series of national reports.
This paper describes the achievements of the Activity and discusses work proposed for the future. 相似文献
70.
This research focuses on the spatial economics of geothermal district energy (DE) systems that distribute hot fluids through a pipeline network to multiple thermal customers. We argue here that DE is held back by uncertainty about its economic feasibility when implemented in real places. DE works best with high urban densities, but in the US the best geothermal resources are in the less-populated west. Economic geography theory suggests that the optimal size of a DE firm's service area should depend on the trade-off between the economies of scale inherent in a large service area and the greater network development costs and heat loss involved in serving a large area. The HEATMAP© software program developed by Washington State University was used to study the feasibility of numerous scenarios for a proposed DE system in Mammoth Lakes, California. Results indicate that the core area of the town is large enough, dense enough, and in close enough proximity to the resource for profitable DE development. Proposed ski village developments would increase the thermal load density and significantly enhance its ability to remain competitive with other fuels, even in pessimistic sensitivity analyses regarding geothermal heat input costs, public participation, and retro-fitting costs. 相似文献