全文获取类型
收费全文 | 278012篇 |
免费 | 24311篇 |
国内免费 | 13510篇 |
专业分类
电工技术 | 17767篇 |
技术理论 | 31篇 |
综合类 | 26326篇 |
化学工业 | 34727篇 |
金属工艺 | 13804篇 |
机械仪表 | 14611篇 |
建筑科学 | 36903篇 |
矿业工程 | 14577篇 |
能源动力 | 12389篇 |
轻工业 | 20183篇 |
水利工程 | 11290篇 |
石油天然气 | 13814篇 |
武器工业 | 4100篇 |
无线电 | 22074篇 |
一般工业技术 | 23050篇 |
冶金工业 | 16865篇 |
原子能技术 | 3967篇 |
自动化技术 | 29355篇 |
出版年
2024年 | 1280篇 |
2023年 | 3684篇 |
2022年 | 6965篇 |
2021年 | 9130篇 |
2020年 | 8955篇 |
2019年 | 6814篇 |
2018年 | 6380篇 |
2017年 | 8246篇 |
2016年 | 9671篇 |
2015年 | 10272篇 |
2014年 | 18544篇 |
2013年 | 17008篇 |
2012年 | 19934篇 |
2011年 | 21958篇 |
2010年 | 16011篇 |
2009年 | 16475篇 |
2008年 | 14824篇 |
2007年 | 18386篇 |
2006年 | 16929篇 |
2005年 | 14623篇 |
2004年 | 12275篇 |
2003年 | 10757篇 |
2002年 | 8918篇 |
2001年 | 7250篇 |
2000年 | 6210篇 |
1999年 | 4899篇 |
1998年 | 3570篇 |
1997年 | 3088篇 |
1996年 | 2532篇 |
1995年 | 2118篇 |
1994年 | 1759篇 |
1993年 | 1287篇 |
1992年 | 1061篇 |
1991年 | 780篇 |
1990年 | 635篇 |
1989年 | 587篇 |
1988年 | 339篇 |
1987年 | 269篇 |
1986年 | 224篇 |
1985年 | 235篇 |
1984年 | 198篇 |
1983年 | 149篇 |
1982年 | 98篇 |
1981年 | 98篇 |
1980年 | 93篇 |
1979年 | 45篇 |
1978年 | 29篇 |
1977年 | 23篇 |
1975年 | 24篇 |
1959年 | 42篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Huai Wen-xin Wuhan University of Hydraulic & Electric Engineering Wuhan Hubei P.R.China Prof.Li Wei 《水动力学研究与进展(B辑)》1993,(3)
Turbulence represents an essential aspect in atmospheric and oceanic circulations.In particu-lar,it is a preponderant factor in the dispersion of pollutants of artificial or natural origin.Thevertical turbulent jets,plumes and buoyant jets discharging into static environment is one of themost important and basic flow patterns related with the environment pollution.These flows havenumerous important applications,for example,thrust augmentors,waste disposal plumes fromstacks and combustion systems,and significant problems of turbulent diffusion. 相似文献
52.
ETRⅠ-30调速器是瑞士爱舍维斯工厂生产的具有PID调节规律的电液调速器。本文对其液压控制系统作了较详细的介绍,供有关人员参考。 相似文献
53.
This paper formulates the pickup and delivery problem, also known as the dial-a-ride problem, as an integer program. Its polyhedral structure is explored and four classes of valid inequalities developed. The results of a branch-and-cut algorithm based on these constraints are presented. 相似文献
54.
WC对Cu/WC_P复合材料性能及组织的影响 总被引:8,自引:0,他引:8
通过WC含量对WC/Cu复合材料性能的影响,确定了冷压-烧结法制备Cu/WC材料的适宜WC含量为10vol%左右。并就WC对该材料组织和再结晶行为的影响进行了有益的探讨。 相似文献
56.
阐述了小电炉采用投资少,见较快,简单易行的炉外处理措施,提高了钢质量和生产率,生产实践和应用结果表明,本措施可为同类型企业的炼钢工艺完善和技术进步提供参考。 相似文献
57.
The aim of this paper is to assess the state-of-the-art in the Decision Support Systems (DSS) field from both a research and a practice perspective. Three main dimensions of DSS research and practice are addressed: 1) supporting human decision-making processes, 2) integrating DSS into the organizational context, and 3) identifying new application domains. The related analysis and discussion provides a better understanding of past developments in the DSS field and insights into future evolution patterns. 相似文献
58.
V. P. Naumenko 《Strength of Materials》1996,28(1):10-18
The adoption of unified fracture mechanics terminology (UFMT) will promote efficient communication between specialists in different fields of fracture research, harmonization of national and international standards relating to fracture mechanics, and last but not least improvement of the existing methodology for teaching and education in fatigue and fracture. In this paper the definitions of some basic and related terms included in different standards on fracture mechanics terminology are confronted with one another. Alternative definitions of the same terms are offered. By this strategy the author tries to show that the definitions of basic and related terms appropriate for the UFMT should emerge as a consequence of harmonizing a crack model with an actual crack and then both taken together with a fracture model, laboratory test methods, and failure assessment codes.Published in Problemy Prochonsti, No. 1, pp. 17–29, January, 1996.This paper is published as a matter of discussion. 相似文献
59.
Packaging engineers need to be able to accurately determine the forces present in the shipping environment in order to protect packaged goods. The purpose of this study was to determine the vertical vibration levels measured in three separate truck-trailer suspension systems; conventional leaf-spring, conventional air-ride and damaged air-ride. The main conclusion reached in this study is that the air-ride suspension when maintained gives lower power density (PD) levels on all road surfaces studied. A damaged air-ride suspension and leaf-spring suspension are very similar in response frequencies, although the damaged air-ride produces higher vibration levels at lower frequencies. 相似文献
60.
Since electronic switching systems usually require very strict reliability requirements as well as good performance objectives, we need to jointly analyse the performance and reliability of switching systems. In this paper, we compare conventional time–space–time switches with single space switches with those with multiple separated space switches, from the viewpoints of reliability and performance. We consider time–space–time switching networks which consist of N incoming time switches, i.e. one NxN space switch, two (N/2)x(N/2) space switches, and four (N/4)x(N/4) space switches. We introduce a Markov reliability model to study the effect of failures and analyse the reliability and performance of three different types of switching networks in terms of average blocking probability and the mean time to unreliable operation, as we vary the offered traffic. As a result, T–S–T switching networks with multiple separated space switches exhibit better performance and reliability than those with single space switches. 相似文献