全文获取类型
收费全文 | 16317篇 |
免费 | 361篇 |
国内免费 | 231篇 |
专业分类
电工技术 | 862篇 |
技术理论 | 1篇 |
综合类 | 342篇 |
化学工业 | 1881篇 |
金属工艺 | 449篇 |
机械仪表 | 660篇 |
建筑科学 | 1831篇 |
矿业工程 | 290篇 |
能源动力 | 4947篇 |
轻工业 | 223篇 |
水利工程 | 84篇 |
石油天然气 | 219篇 |
武器工业 | 36篇 |
无线电 | 1071篇 |
一般工业技术 | 1378篇 |
冶金工业 | 636篇 |
原子能技术 | 417篇 |
自动化技术 | 1582篇 |
出版年
2024年 | 21篇 |
2023年 | 285篇 |
2022年 | 422篇 |
2021年 | 530篇 |
2020年 | 451篇 |
2019年 | 404篇 |
2018年 | 389篇 |
2017年 | 422篇 |
2016年 | 582篇 |
2015年 | 542篇 |
2014年 | 905篇 |
2013年 | 913篇 |
2012年 | 799篇 |
2011年 | 1784篇 |
2010年 | 1253篇 |
2009年 | 1061篇 |
2008年 | 939篇 |
2007年 | 939篇 |
2006年 | 704篇 |
2005年 | 479篇 |
2004年 | 375篇 |
2003年 | 362篇 |
2002年 | 276篇 |
2001年 | 217篇 |
2000年 | 202篇 |
1999年 | 185篇 |
1998年 | 199篇 |
1997年 | 142篇 |
1996年 | 152篇 |
1995年 | 120篇 |
1994年 | 121篇 |
1993年 | 89篇 |
1992年 | 74篇 |
1991年 | 62篇 |
1990年 | 59篇 |
1989年 | 52篇 |
1988年 | 38篇 |
1987年 | 34篇 |
1986年 | 30篇 |
1985年 | 71篇 |
1984年 | 55篇 |
1983年 | 42篇 |
1982年 | 56篇 |
1981年 | 16篇 |
1980年 | 24篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
61.
随着电炉炼钢技术的发展,电炉已成为一种高效的废钢熔化设备,本文从利用初级燃料及电炉废气能的观点出发,对强化电炉冶炼的措施进行了讨论. 相似文献
62.
Quasi-static and dynamic crushing behaviors of aluminum and steel tubes with a cutout 总被引:3,自引:0,他引:3
Tubular members are commonly used as an energy absorber in engineering structures and many such members have a cutout. In this study, the crushing behaviors of tubes with a cutout are characterized and the effects of cutout on the energy absorption capabilities of these tubes are quantified. Systematic parametric studies were carried out to study the effect of material properties, including yield and ultimate strength of material, strain rate effect, location of cutout, tube length and impact speed on the crushing behaviors and energy absorption capacity of aluminum and steel tubes. First, a numerical model was constructed with a commercial explicit finite element code. It will be first proven that the numerical simulation can produce sufficiently accurate results in an economic manner. Subsequently, the crushing behavior of aluminum and steel tubes with a cutout was experimentally characterized and their energy absorption capacity was evaluated in terms of mean crushing force, peak crushing force and specific energy absorption (SEA). Tubes of various lengths with a cutout located at different locations, subject to both quasi-static and dynamic impact loadings were considered. For steel tubes, the numerical simulation investigated the influence of the strain rate effect and variation in strain hardening ratio of the material. Empirical equations describing the mean and peak crushing forces of aluminum and steel tubes with a cutout were developed using linear and nonlinear regression methods applied to the results obtained from the numerical and experimental studies. 相似文献
63.
夏季住宅空调能耗已成为目前广州地区电力过荷的一个主要原因,而目前建筑师对住宅设计中的空调能耗因素并未有深入的考虑。本文就广州地区中高层住宅标准层平面设计中的朝向、形状、大小及层高与空调能耗关系进行了相关的分析,适用于夏热冬暖地区。 相似文献
64.
This paper attempts to shed light on the determinants of energy demand in Turkey. Energy demand model is first proposed using the ant colony optimization (ACO) approach. It is multi-agent systems in which the behavior of each ant is inspired by the foraging behavior of real ants to solve optimization problem. ACO energy demand estimation (ACOEDE) model is developed using population, gross domestic product (GDP), import and export. All equations proposed here are linear and quadratic. Quadratic_ACOEDE provided better-fit solution due to fluctuations of the economic indicators. The ACOEDE model plans the energy demand of Turkey until 2025 according to three scenarios. The relative estimation errors of the ACOEDE model are the lowest when they are compared with the Ministry of Energy and Natural Resources (MENR) projection. 相似文献
65.
Due to the fact that human activities and most sustainability issues are closely related to energy use, the energy system is a sound framework for providing lead indicators for sustainable development. Common energy-economic models enable the estimation of future states of the energy system. An energy system-based lead indicator set can be used to develop consistent and coherent future indicator estimates and to track sustainability, a clear advantage over existing sets. 相似文献
66.
针对烧结机新老蒸汽系统各自独立,使用效率低,不能充分发挥效能的状态,提出了蒸汽系统新老余热管网并网改造,经过一年多的运行,取得了显著的效果。 相似文献
67.
68.
U. Amato G. Amodeo V. Brandi V. Cuomo D. Ruggi C. Serio V. Silvestrini G. C. Tosato 《国际能源研究杂志》1985,9(1):33-51
In Italy solar thermal energy and energy from biogas are two possible means of reducing dependence on energy imports. Using a multiperiod LP model (MARKAL) the authors assessed the likely potential of both technologies under various circumstances. The study covered the period 1980–2005, in five segments of five years. It focused only on the subsystem of the energy end-uses which can be substituted for by solar thermal and biogas technologies. The overall non-renewable sources which can be saved in 20 years by these technologies total 450 PJ (1 PJ = 101 5 J) if the fuel prices rise at 0 per cent average annual, 1450 PJ if the fuel prices rise at 4.2 per cent average annual, 1860 PJ if the fuel prices rise at 7.2 per cent average annual and 3780 PJ if the fuel prices rise at 15 per cent average annual. However the most competitive technologies appear to be solar water heaters used mainly in the private and commercial sectors and biogas systems used mainly in the agricultural sector. The study was carried out by APRE under ENEA (formerly CNEN) contract and was intended to serve as an analytical basis for establishing an overall development and demonstration strategy for end-use renewable technologies in Italy. 相似文献
69.
Colin Hines 《Energy Policy》1985,13(2):188-189
This communication illustrates the work of the London Energy and Employment Network. LEEN has the twin aims of promoting a rational energy policy for London and, in the process, generating much needed employment. In cooperation with Hackney, one of Britain's poorest boroughs, LEEN organized Hackney's Cold War — a series of initiatives showing the practical measures, informational back-up and funding sources necessary for a local energy policy. LEEN intends to repeat this project in other London Boroughs, with the eventual aim of helping to persuade central government to adopt a more comprehensive approach to energy conservation nationally. 相似文献
70.
This paper examines the dynamic causal relationships between pollutant emissions, energy consumption, and output for France using cointegration and vector error-correction modelling techniques. We argue that these variables are strongly inter-related and therefore their relationship must be examined using an integrated framework. The results provide evidence for the existence of a fairly robust long-run relationship between these variables for the period 1960–2000. The causality results support the argument that economic growth exerts a causal influence on growth of energy use and growth of pollution in the long run. The results also point to a uni-directional causality running from growth of energy use to output growth in the short run. 相似文献