全文获取类型
收费全文 | 19523篇 |
免费 | 466篇 |
国内免费 | 353篇 |
学科分类
工业技术 | 20342篇 |
出版年
2024年 | 21篇 |
2023年 | 310篇 |
2022年 | 454篇 |
2021年 | 585篇 |
2020年 | 509篇 |
2019年 | 463篇 |
2018年 | 426篇 |
2017年 | 491篇 |
2016年 | 647篇 |
2015年 | 619篇 |
2014年 | 1066篇 |
2013年 | 1097篇 |
2012年 | 941篇 |
2011年 | 2001篇 |
2010年 | 1433篇 |
2009年 | 1217篇 |
2008年 | 1061篇 |
2007年 | 1151篇 |
2006年 | 895篇 |
2005年 | 650篇 |
2004年 | 565篇 |
2003年 | 532篇 |
2002年 | 416篇 |
2001年 | 327篇 |
2000年 | 293篇 |
1999年 | 309篇 |
1998年 | 260篇 |
1997年 | 212篇 |
1996年 | 225篇 |
1995年 | 185篇 |
1994年 | 160篇 |
1993年 | 122篇 |
1992年 | 84篇 |
1991年 | 74篇 |
1990年 | 69篇 |
1989年 | 59篇 |
1988年 | 49篇 |
1987年 | 40篇 |
1986年 | 29篇 |
1985年 | 70篇 |
1984年 | 60篇 |
1983年 | 42篇 |
1982年 | 57篇 |
1981年 | 15篇 |
1980年 | 23篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Global competition, commitment to the Kyoto Protocol and a deregulated, integrated European electricity market will in all probability increase the demand for energy efficiency on the part of companies in Sweden. Investment decisions are an important part of meeting the new demands, because they decide the future efficiency of industrial energy systems. The objective of this study is to investigate, from a managerial perspective, the need to improve decision support in some industries, which can help to facilitate and improve investment decisions concerning energy efficiency. This work has been conducted through in-depth interviews with representatives for a number of energy-intensive companies and non-energy-intensive companies from different sectors. One need that was identified was the improvement of working methods in order to support the decision-making process. Here, external players seem to be playing an increasingly important role. Access to correct information, better follow-up activities, and transparent, understandable calculations are also considered to be important. The study will form the foundation for subsequent work on decision support and energy efficiency in industry. 相似文献
92.
本文介绍了南钢中板厂将系统工程最优化技术中的随机服务系统理论和可靠性设计方法引入到电气设备的维护和管理工作中,并结合现场实际情况摸索出一套电气设备可靠性保障方法。 相似文献
93.
介绍空分制氮装置采用膨胀机循环与液氮循环的两种工艺流程及能量平衡 ,示出了两种循环的实例比较。指出外供液氮可以作为冷源替代膨胀机 ,且单耗低、操作更方便 ,设备维护量更小、氮气提取率更高 相似文献
94.
In Part I of this paper, a theoretical basis is presented using a two-degrees-of-freedom model. In this second part of the study, the passive control and the two types of semiactive controls introduced in Part I are examined numerically for a taut cable experiencing wind-induced galloping motion. The passive and the semiactive control schemes for taut cables show a good similarity with the results obtained for the two-degrees-of-freedom model. The potential of using these control schemes in practical applications to flexible structures is demonstrated. 相似文献
95.
96.
Location and calculation-free node-scheduling schemes in large wireless sensor networks 总被引:1,自引:0,他引:1
In wireless sensor networks that consist of a large number of low-power, short-lived, unreliable sensors, one of the main design challenges is to obtain long system lifetime without sacrificing system original performance (sensing coverage and sensing reliability). To solve this problem, one of the potential approaches is to identify redundant nodes at the sensing interface and then assign them an off-duty operation mode that has lower energy consumption than the normal on-duty mode. In our previous work [J. Wireless Commun. Mobile Comput. 3 (2003) 271; Processing of ACM Wireless Sensor Network and Application Workshop 2002, September 2002], we proposed a node-scheduling scheme, which can provide a 100% sensing coverage preservation capability. This, however, requires each node to be aware of its own and its neighbors’ location information. Also, in that scheme, each node has to do accurate geometrical calculation to determine whether to take an off-duty status. In this paper, we propose and study several alternative node-scheduling schemes, which cannot completely preserve the original system coverage, but are nonetheless light-weighted and flexible compared with the previous one. Our simulation results compare these schemes with the previous one and demonstrate their effectiveness. 相似文献
97.
Venezuela's vast natural resource base has largely shaped the nation's economic and energy-use patterns. Major opportunities exist for improving the efficiency of energy use in Venezuela and, consequently, restraining the growth of energy-related carbon emissions. This paper presents a detailed report of one potential development path for Venezuela and estimates the ensuing levels of energy demand and CO2 emissions associated with pursuing this path through the year 2025. The results indicate that by adopting a development strategy that incorporates structural changes in the economy, fuel-switching measures and improved end-use efficiencies, Venezuela can introduce energy efficiency and carbon restraints as part of its economic development process. 相似文献
98.
Gerald Leach 《Energy Policy》1991,19(10):918-925
The UK differs from may other industrialized nations in that its carbon dioxide (CO2) emissions from energy use have declined in recent years despite relatively rapid economic growth. In all sectors but transport, substantial reductions have already occurred in the level of carbon emissions per unit of GDP output. At the same time, a number of official and unofficial studies have pointed out that the UK has one of the largest remaining potentials amongst comparable industrialized countries for achieving further CO2 reductions through the implementation of cost-effective energy efficiency and fuel switching measures. This paper discusses past and present patterns of energy use and carbons emissions in the UK. The analysis then examines historical trends in UK energy policy and presents policy options for further reducing the UK's energy-use and carbon emissions in the future. 相似文献
99.
100.
Mi Thxi 《计算机科学技术学报》1997,12(5):425-440
The original interpretation of the constructive set theory CZF in Martin-Loef‘s type theory uses the‘extensional identity types’.It is generally believed that these‘types’do not belong to type theory.In this paper it will be shown that the interpretation goes through without identity types.This paper will also show that the interpretation can be given in an intensional type theory.This reflects the computational nature of the interpretation.This computational aspect is reinforced by an ω-Set moel of CZF. 相似文献