全文获取类型
收费全文 | 80192篇 |
免费 | 8465篇 |
国内免费 | 5085篇 |
专业分类
电工技术 | 6011篇 |
技术理论 | 4篇 |
综合类 | 6271篇 |
化学工业 | 11598篇 |
金属工艺 | 4956篇 |
机械仪表 | 5701篇 |
建筑科学 | 6518篇 |
矿业工程 | 2604篇 |
能源动力 | 2275篇 |
轻工业 | 6705篇 |
水利工程 | 2010篇 |
石油天然气 | 3383篇 |
武器工业 | 902篇 |
无线电 | 9152篇 |
一般工业技术 | 8897篇 |
冶金工业 | 3529篇 |
原子能技术 | 1456篇 |
自动化技术 | 11770篇 |
出版年
2024年 | 440篇 |
2023年 | 1375篇 |
2022年 | 2735篇 |
2021年 | 3617篇 |
2020年 | 2689篇 |
2019年 | 2190篇 |
2018年 | 2400篇 |
2017年 | 2728篇 |
2016年 | 2475篇 |
2015年 | 3484篇 |
2014年 | 4409篇 |
2013年 | 5065篇 |
2012年 | 5934篇 |
2011年 | 6292篇 |
2010年 | 5676篇 |
2009年 | 5585篇 |
2008年 | 5407篇 |
2007年 | 5133篇 |
2006年 | 4649篇 |
2005年 | 4000篇 |
2004年 | 2847篇 |
2003年 | 2333篇 |
2002年 | 2383篇 |
2001年 | 2134篇 |
2000年 | 1761篇 |
1999年 | 1353篇 |
1998年 | 860篇 |
1997年 | 702篇 |
1996年 | 639篇 |
1995年 | 557篇 |
1994年 | 405篇 |
1993年 | 345篇 |
1992年 | 261篇 |
1991年 | 187篇 |
1990年 | 158篇 |
1989年 | 101篇 |
1988年 | 114篇 |
1987年 | 60篇 |
1986年 | 68篇 |
1985年 | 34篇 |
1984年 | 29篇 |
1983年 | 19篇 |
1982年 | 17篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1977年 | 7篇 |
1970年 | 7篇 |
1959年 | 11篇 |
1951年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
MIMO (Multiple-Input Multiple-Output)的显著优点就是在不增加带宽的情况下,能够成倍地提高通信系统容量和频谱利用率,是未来移动通信与个人通信系统实现高速率数据传输,提高高传输质量的重要途径,也是未来移动通信系统广泛采用的关键技术.文中简要介绍了MIMO系统及其一种新的MIMO系统中的应用技术,即PARC(Per-antenna Rate Control)技术. 相似文献
73.
Min Chan Kim Dong Won Lee Chang Kyun Choi 《Korean Journal of Chemical Engineering》2008,25(6):1239-1244
When a horizontal homogeneous solid is melted from below, convection can be induced in a thermally unstable melt layer. In
this study the onset of buoyancy-driven convection during time-dependent melting is investigated by using similarly transformed
disturbance equations. The critical Rayleigh numbers based on the melt-layer thickness are found numerically for various conditions.
For small superheats, the present predictions approach the well known results of classical Rayleigh-Bénard problems, that
is, critical Rayleigh numbers are located between 1,296 and 1,708, regardless of the Prandtl number. However, for high superheats
the critical Rayleigh number increases with an increase in phase change rate but with decrease in Prandtl number. 相似文献
74.
Skim and whole milk powders were manufactured at lab scale by spray freeze drying (SFD), using liquid nitrogen as the cryogen. The polydispersity of droplet/particle sizes was limited using an encapsulator nozzle to atomize the feed. Particle morphology was examined using a scanning electron microscope. Samples were compared with equivalent spray-dried powders in tests of wettability and dissolution in water. The spray freeze-dried powders were found to be highly porous, with a uniform structure of pores throughout the entire particles. When tested in water, SFD skim milk powders wetted roughly three times as fast as industrially spray-dried agglomerated skim milk powders and were observed to dissolve rapidly by breaking down into smaller particles. 相似文献
75.
Lei Liu Ying Kong Hong Xu Jin P. Li Jin X. Dong Zhi Lin 《Microporous and mesoporous materials》2008,115(3):624-628
A three-dimensional zinc phosphate compound with DFT topology, designated as ZnPO4-EU1, has been synthesized by an ionothermal approach from the system HF-ZnO–P2O5-choline chloride-imidazolidone. Ethylenediamine, derived from decomposition of the imidazolidone component of the deep-eutectic solvent (DES) itself, is delivered to the synthesis and serves as an appropriate template for ZnPO4-EU1. Experiments in which the synthesis conditions were varied showed that ZnPO4-EU1 may be prepared over a wide molar ratio of P/Zn = 0.55–13.0. Powder X-ray diffraction patterns have been obtained at intervals to track the crystallization process of this material. The experimental data show that Zn3(PO4)2 · 4H2O (a dense phase) was first isolated from the DES after reaction for 1 h. Subsequently, the pure phase of ZnPO4-EU1 was obtained with increasing crystallization time from 12 h to 72 h. The experimental results show that the nucleation and crystallization take place with relatively low levels of solvent degradation, demonstrating that zinc phosphate with a three-dimensional framework can be synthesized by in situ generation of an appropriate template using an unstable DES at high temperatures (150–200 °C). 相似文献
76.
基于FPGA乘法器架构的RNS与有符号二进制量转换 总被引:1,自引:1,他引:0
RNS(余数数制系统)是一种整数运算系统,在粒度精确性,能源损耗和响应速度上有很大的优势.从RNS到二进制数的输入输出转换是基于余数算法的专用架构实现的关键.本文提出了一个基于N类模的RNS与有符号二进制量的通用转换算法在FPGAs的乘法器上的实现过程.该算法能更有效地进行有符号数与RNS的转换.基于该算法类型乘法器在同类型乘法器中显示出了速度优势.文章中该架构被映射到Altera的10K系列的FPGA上. 相似文献
77.
Dong Zhang 《Korean Journal of Chemical Engineering》2008,25(5):1205-1207
Ceria-zirconia solid particles have been recognized as a key material of the automotive exhaust catalysts since they can release
and uptake oxygen owing to the rapid reversible oxidation states of cerium between Ce3+ and Ce4+. Several methods have recently been described to prepare the CeO2-ZrO2 solid particles used in the catalysts. In this paper, a new coprecipitation method is used to prepare the CeO2-ZrO2 solid particles. The Ce-Zr alcogel is dried and calcined in flowing N2 not in flowing air under atmospheric pressure. The results show that the ceria-zirconia sample calcined at 650 °C has high
surface area over 90 m2g−1, which drops to 40 m2g−1 following treatment at 900°C. 相似文献
78.
后遥感应用技术的提出与思考 总被引:4,自引:3,他引:1
本文在总结遥感技术应用于铀矿地质领域的实践和遥感技术最新进展的基础上。提出后遥感应用技术,并对其技术内涵、研究内容、建立试验样区、研究意义等进行了探讨。 相似文献
79.
80.
就我公司动力厂给水车间155kW水泵电机无功就地补偿的可行性及经济效益进行了分析和研究,对工厂用电如何节能降耗有一定的参考价值。 相似文献