全文获取类型
收费全文 | 7047篇 |
免费 | 468篇 |
国内免费 | 208篇 |
专业分类
电工技术 | 383篇 |
综合类 | 341篇 |
化学工业 | 1091篇 |
金属工艺 | 277篇 |
机械仪表 | 307篇 |
建筑科学 | 554篇 |
矿业工程 | 245篇 |
能源动力 | 202篇 |
轻工业 | 391篇 |
水利工程 | 132篇 |
石油天然气 | 273篇 |
武器工业 | 17篇 |
无线电 | 1025篇 |
一般工业技术 | 954篇 |
冶金工业 | 611篇 |
原子能技术 | 72篇 |
自动化技术 | 848篇 |
出版年
2024年 | 19篇 |
2023年 | 83篇 |
2022年 | 144篇 |
2021年 | 206篇 |
2020年 | 145篇 |
2019年 | 154篇 |
2018年 | 161篇 |
2017年 | 158篇 |
2016年 | 180篇 |
2015年 | 240篇 |
2014年 | 315篇 |
2013年 | 394篇 |
2012年 | 347篇 |
2011年 | 419篇 |
2010年 | 352篇 |
2009年 | 346篇 |
2008年 | 357篇 |
2007年 | 362篇 |
2006年 | 356篇 |
2005年 | 332篇 |
2004年 | 225篇 |
2003年 | 193篇 |
2002年 | 207篇 |
2001年 | 186篇 |
2000年 | 195篇 |
1999年 | 206篇 |
1998年 | 233篇 |
1997年 | 187篇 |
1996年 | 166篇 |
1995年 | 131篇 |
1994年 | 115篇 |
1993年 | 89篇 |
1992年 | 88篇 |
1991年 | 68篇 |
1990年 | 51篇 |
1989年 | 40篇 |
1988年 | 37篇 |
1987年 | 18篇 |
1986年 | 26篇 |
1985年 | 20篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 11篇 |
1980年 | 20篇 |
1979年 | 14篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 17篇 |
1973年 | 9篇 |
1972年 | 7篇 |
排序方式: 共有7723条查询结果,搜索用时 654 毫秒
1.
2.
3.
Functional expression and synergistic cooperation of xylan‐degrading enzymes from Hypocrea orientalis and Aspergillus niger
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
4.
Shouguang Wang Mengdi Gan Mengchu Zhou Dan You 《IEEE/CAA Journal of Automatica Sinica》2015,2(4):345-352
As a powerful analysis tool of Petri nets, reachability trees are fundamental for systematically investigating many characteristics such as boundedness, liveness and reversibility. This work proposes a method to generate a reachability tree, called ωRT for short, for a class of unbounded generalized nets called ω-independent nets based on new modified reachability trees (NMRTs). ωRT can effectively decrease the number of nodes by removing duplicate and ω-duplicate nodes in the tree, and verify properties such as reachability, liveness and deadlocks. Two examples are provided to show its superiority over NMRTs in terms of tree size. 相似文献
5.
6.
<正>第十一章离子液体在分离过程中的应用(上接第2006年第5期) 5.2有机/生物/生物燃料分子的离子液体萃取由于带电有机物在离子液体中的高溶解性,促进了离子液体回收有机物的发展。如表11-7所示,在IL-H_2O两相体系中进行了一些取代苯衍生物的相分配研究。 相似文献
7.
A new method based on the differential evolution (DE) algorithm is proposed for antenna-array pattern synthesis with prescribed nulls. The array excitation amplitudes are the only controlling parameters, and the objectives are to synthesize array patterns with nulls imposed on directions of interferences while keeping the sidelobe levels (SLLs) below prescribed levels. Many factors such as the excitation dynamic range ratio, null depth level, null width, and SLLs are taken into account in the synthesis. Simulation results of several typical problems are compared with published results to illustrate the effectiveness of the proposed method. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 14: 57–63, 2004. 相似文献
8.
9.
Development of a recurrent Sigma-Pi neural network rainfall forecasting system in Hong Kong 总被引:1,自引:1,他引:0
At the moment, weather forecasting is still an art — the experience and intuition of forecasters play a significant role in determining the quality of forecasting. This paper describes the development of a new approach to rainfall forecasting using neural networks. It deals with the extraction of information from radar images and an evaluation of past rain gauge records to provide shortterm rainfall forecasting. All of the meteorological data were provided by the Royal Observatory of Hong Kong (ROHK). Preprocessing procedures were essential for this neural network rainfall forecasting. The forecast of the rainfall was performed every half an hour so that a storm warning signal can be delivered to the public in advance. The network architecture is based on a recurrent Sigma-Pi network. The results are very promising, and this neural-based rainfall forecasting system is capable of providing a rain storm warning signal to the Hong Kong public one hour ahead. 相似文献
10.
To determine whether there is any correlation between sudden decrease in barometric pressure and onset of labor, a non-experimental, retrospective study at a 948-bed tertiary care hospital was done. Pregnant patients of 36 weeks gestation or more who presented with spontaneous onset of labor during the 48 hours surrounding the 12 occurrences of significant drop in barometric pressure in 1992 were included in the study. Significantly more occurrences of onset of labor were identified in the 24 hours after a drop in barometric pressure than were identified in the 24 hours prior to the drop in barometric pressure (P < 0.05). Therefore, the overall number of labor onsets increased in the 24 hours following a significant drop in barometric pressure. 相似文献