全文获取类型
收费全文 | 101670篇 |
免费 | 13398篇 |
国内免费 | 5314篇 |
专业分类
电工技术 | 52120篇 |
技术理论 | 5篇 |
综合类 | 8167篇 |
化学工业 | 2843篇 |
金属工艺 | 1921篇 |
机械仪表 | 4130篇 |
建筑科学 | 3725篇 |
矿业工程 | 2119篇 |
能源动力 | 8416篇 |
轻工业 | 1148篇 |
水利工程 | 2849篇 |
石油天然气 | 951篇 |
武器工业 | 683篇 |
无线电 | 13398篇 |
一般工业技术 | 3360篇 |
冶金工业 | 1806篇 |
原子能技术 | 2225篇 |
自动化技术 | 10516篇 |
出版年
2024年 | 481篇 |
2023年 | 1331篇 |
2022年 | 2549篇 |
2021年 | 3012篇 |
2020年 | 3474篇 |
2019年 | 2778篇 |
2018年 | 2532篇 |
2017年 | 3602篇 |
2016年 | 3862篇 |
2015年 | 4419篇 |
2014年 | 7621篇 |
2013年 | 5988篇 |
2012年 | 8439篇 |
2011年 | 9108篇 |
2010年 | 6713篇 |
2009年 | 6780篇 |
2008年 | 6699篇 |
2007年 | 7834篇 |
2006年 | 6831篇 |
2005年 | 5451篇 |
2004年 | 4394篇 |
2003年 | 3507篇 |
2002年 | 2628篇 |
2001年 | 2275篇 |
2000年 | 1898篇 |
1999年 | 1372篇 |
1998年 | 912篇 |
1997年 | 730篇 |
1996年 | 697篇 |
1995年 | 538篇 |
1994年 | 480篇 |
1993年 | 287篇 |
1992年 | 254篇 |
1991年 | 156篇 |
1990年 | 129篇 |
1989年 | 108篇 |
1988年 | 94篇 |
1987年 | 67篇 |
1986年 | 37篇 |
1985年 | 37篇 |
1984年 | 61篇 |
1983年 | 50篇 |
1982年 | 51篇 |
1981年 | 23篇 |
1980年 | 12篇 |
1979年 | 12篇 |
1978年 | 13篇 |
1977年 | 8篇 |
1959年 | 16篇 |
1956年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
A. Blazevic H. G. Bohlen W. von Oertzen 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2002,190(1-4):64-68
We report on measurements of charge changing cross-sections and energy losses in dependence on the initial and final charge state of Ne ions at an incident energy of 2 MeV/u penetrating thin carbon foils. Different initial charge states could be separated in energy by applying a high voltage in front of the carbon foils; the final charges and their energy loss were measured with a high-resolution magnetic spectrometer. We derived a consistent evolution of the charge state distribution solving the corresponding rate equations for the measured cross-sections. Including the charge state dependent energy losses, ΔE(qi,qf), stopping power values for frozen charge states, S(q), could be extracted. The experimental data are compared with different theoretical predictions. 相似文献
112.
本文从理论上分析了在不同功率因数下不同供电距离的能耗对比及近年来进行无功补偿的情况,从而说明了无功补偿对远距离供电节能降耗的重要意义。 相似文献
113.
114.
115.
电站锅炉制粉系统的爆炸原因与防范对策 总被引:1,自引:0,他引:1
火力发电厂制粉系统爆炸事故时有发生 ,重大设备损坏 ,造成了严重的经济损失。本文通过分析研究 ,找出制粉系统爆炸的原因 ,从措施上、煤的质量控制上及制粉系统结构改造上提出了防范的对策。 相似文献
116.
Transmission of signals, whether on-chip or off-chip, places severe constraints on timing and extracts a large price in energy. New silicon device technologies, such as back-plane CMOS, provide a programmable and adaptable threshold voltage as an additional tool that can be used for low power design. We show that one particularly desirable use of this freedom is energy-efficient high-speed transmission across long interconnects using multi-valued encoding. Our multi-valued CMOS circuits take advantage of the threshold voltage control of the transistors, by using the signal-voltage-to-threshold-voltage span, in order to make area-efficient implementations of 4-PAM (pulse amplitude modulation) transceivers operating at high speed. In a comparison of a variety of published technologies, for signal transmission with interconnects of 10-15 mm length, we show up to 50% improvement in energy for on-chip signal transmission over binary encoding together with higher limits for operating speeds without a penalty in circuit noise margin. 相似文献
117.
PMM8731是日本三洋电机公司生产的步进电机脉冲分配器。而SI-7300则是日本三青公司生产的高性能步进电机集成功率放大器。它们和单片机一起可构成一种高效电机控制驱动电路。文中介绍了PMM8713与SI-7300的功能 ,给出了由它们组成的功率驱动电路及其在步进电机上的应用方法 相似文献
118.
D.H.R. Price J.A. Sharp 《International Journal of Electrical Power & Energy Systems》1985,7(3):131-137
Peak demand forecasts obtained from six different univariate forecasting methods, under a range of conditions, were used to drive a capacity acquisition model of a large electrical supply system; and the resulting physical and financial performance of the model was observed for each set of forecasts. The results obtained are discussed in the context of their implications for the choice of load forecasting method used in capacity acquisition planning by a power supply undertaking. 相似文献
119.
分析了电石法PVC生产链中电石炉烟气及电厂烟气二氧化硫的排放情况,指出利用电石炉烟气中的CO合成氨、再将合成氨用于燃煤电厂烟气的"氨法"脱硫是具有较大应用潜力的循环经济产业链。 相似文献
120.
Sirisha Nerella Debendra K. Das Godwin A. Chukwu Abhijit Y. Dandekar Santanu Khataniar Shirish L. Patil 《Petroleum Science and Technology》2003,21(7):1275-1294
Gas-to-liquids (GTL) technology involves the conversion of natural gas to liquid hydrocarbons. In this article, theoretical studies have been presented to determine the feasibility of transporting GTL products through the Trans-Alaska Pipeline System (TAPS). To successfully transport GTL through TAPS, heat loss along the route must be carefully determined. This study presents heat transfer and fluid dynamic calculations to evaluate this feasibility. Because of heat loss, the fluid temperature decreases in the direction of flow and this affects the fluid properties, which in turn influence convection coefficient and pumping power requirements. The temperature and heat loss distribution along the pipeline at different locations have been calculated. Fairly good agreement with measured oil temperatures is observed. The powers required to pump crude oil and GTL individually, against various losses have been calculated. Two GTL transportation modes have been considered; one as a pure stream of GTL and the second as a commingled mixture with crude oil. These results show that the pumping power and heat loss for GTL are less than that of the crude oil for the same volumetric flow rate. Therefore, GTL can be transported through TAPS using existing equipment at pump stations. 相似文献