全文获取类型
收费全文 | 73746篇 |
免费 | 7773篇 |
国内免费 | 4522篇 |
专业分类
电工技术 | 5687篇 |
技术理论 | 2篇 |
综合类 | 6552篇 |
化学工业 | 10795篇 |
金属工艺 | 4231篇 |
机械仪表 | 4934篇 |
建筑科学 | 5917篇 |
矿业工程 | 2276篇 |
能源动力 | 1915篇 |
轻工业 | 7371篇 |
水利工程 | 1887篇 |
石油天然气 | 2846篇 |
武器工业 | 847篇 |
无线电 | 8213篇 |
一般工业技术 | 7368篇 |
冶金工业 | 3004篇 |
原子能技术 | 1038篇 |
自动化技术 | 11158篇 |
出版年
2024年 | 457篇 |
2023年 | 1402篇 |
2022年 | 2786篇 |
2021年 | 3668篇 |
2020年 | 2786篇 |
2019年 | 2088篇 |
2018年 | 2351篇 |
2017年 | 2667篇 |
2016年 | 2306篇 |
2015年 | 3348篇 |
2014年 | 4393篇 |
2013年 | 5062篇 |
2012年 | 5842篇 |
2011年 | 5989篇 |
2010年 | 5617篇 |
2009年 | 5167篇 |
2008年 | 5054篇 |
2007年 | 4786篇 |
2006年 | 4188篇 |
2005年 | 3379篇 |
2004年 | 2449篇 |
2003年 | 1886篇 |
2002年 | 1775篇 |
2001年 | 1443篇 |
2000年 | 1229篇 |
1999年 | 991篇 |
1998年 | 536篇 |
1997年 | 492篇 |
1996年 | 440篇 |
1995年 | 349篇 |
1994年 | 269篇 |
1993年 | 199篇 |
1992年 | 154篇 |
1991年 | 118篇 |
1990年 | 77篇 |
1989年 | 79篇 |
1988年 | 60篇 |
1987年 | 26篇 |
1986年 | 24篇 |
1985年 | 13篇 |
1984年 | 20篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 16篇 |
1980年 | 21篇 |
1979年 | 8篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1959年 | 9篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Removal of gold from basic solutions containing [Au(CN)2]? has been demonstrated using the inherently conducting polymer polypyrrole. Polymers containing sulfonated aromatic dopants have been found to display a significant ability to remove gold from such solutions. Experiments performed in solutions containing both gold and copper cyanide complexes indicate that the recovery process is not highly selective. However, the polypyrroles used display significantly faster rates of gold recovery than activated carbon. © 2003 Society of Chemical Industry 相似文献
2.
3.
研究了用黄磷渣代替部分粘土作陶瓷原料,既可以解决磷渣对环境的污染和堆放占用耕地问题,使该固体废弃物资源化,又能缓解陶瓷原料的短缺。 相似文献
4.
Yu‐Qing Cao Zhan Zhang Yan‐Xin Guo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(10):1441-1444
A new efficient method for synthesising nitriles, important organic reagents, is reported in this paper. In an environmentally benign solvent‐free system, aryl carboxylic acids were converted into the corresponding nitriles via one‐pot reactions, by amidation with ethyl carbamate followed by dehydration with thionyl chloride, in excellent yields. The results showed that the method has the advantages of lower cost, higher yield, less pollution and greater ease of work‐up. Copyright © 2008 Society of Chemical Industry 相似文献
5.
6.
Charalambous C.D. Bultitude R.J.C. Li X. Zhan J. 《Wireless Communications, IEEE Transactions on》2008,7(2):434-439
This paper is concerned with modeling and identification of wireless channels using noisy measurements. The models employed are governed by stochastic differential equations (SDEs) in state space form, while the identification method is based on the expectation-maximization (EM) algorithm and Kalman filtering. The algorithm is tested against real channel measurements. The results presented include state space models for the channels, estimates of inphase and quadrature components, and estimates of the corresponding Doppler power spectral densities (DPSDs), from sample noisy measurements. Based on the available measurements, it is concluded that state space models of order two are sufficient for wireless flat fading channel characterization. 相似文献
7.
8.
清代皇家园林规划设计控制的量化研究——以圆明三园、清漪园为例 总被引:1,自引:0,他引:1
本文通过量化分析探索了清代皇家园林规划设计的控制规律及相关理论。 相似文献
9.
Vacuum treatment and ion-beam bombardment are two major processes in the low energy ion-beam implantation. To accurately study the contributions of these two major factors to the bioeffects separately, the M1 generation variation of Arabidopsis thaliana with ion-beam implantation and vacuum treatment were compared through a series of key plant development parameters including morphological observation, biochemical assay and RAPD (random amplified polymorphic DNA) analysis. The results showed that ion-beam implantation had obvious effect on almost all of these parameters, and the vacuum treatment had some impacts on several morphological parameters such as the bolting time and the length of the primary stem. Taking the results together, the indication is that vacuum treatment has some slight contributions to the bioeffects of ion-beam implantation while ion-beam bombardment itself is the major creator of the bioeffects. 相似文献
10.
应用色谱—质谱(GC-MS)及裂解色谱-质谱(PGC-MS)测定了乙烯基三甲基硅烷等离子体聚合反应中的气体冷凝物及聚合物,研究推导了等离子体聚合反应历程。单体在气相中被电子撞击,然后扩散到基底,在基底发生链增长和链终止反应。 相似文献