全文获取类型
收费全文 | 3901篇 |
免费 | 72篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 28篇 |
化学工业 | 422篇 |
金属工艺 | 114篇 |
机械仪表 | 69篇 |
建筑科学 | 100篇 |
矿业工程 | 4篇 |
能源动力 | 67篇 |
轻工业 | 277篇 |
水利工程 | 18篇 |
石油天然气 | 7篇 |
无线电 | 238篇 |
一般工业技术 | 433篇 |
冶金工业 | 1847篇 |
原子能技术 | 36篇 |
自动化技术 | 319篇 |
出版年
2021年 | 18篇 |
2019年 | 26篇 |
2018年 | 28篇 |
2017年 | 24篇 |
2016年 | 27篇 |
2015年 | 25篇 |
2014年 | 36篇 |
2013年 | 140篇 |
2012年 | 49篇 |
2011年 | 92篇 |
2010年 | 76篇 |
2009年 | 76篇 |
2008年 | 86篇 |
2007年 | 79篇 |
2006年 | 66篇 |
2005年 | 49篇 |
2004年 | 67篇 |
2003年 | 65篇 |
2002年 | 57篇 |
2001年 | 55篇 |
2000年 | 54篇 |
1999年 | 89篇 |
1998年 | 522篇 |
1997年 | 314篇 |
1996年 | 218篇 |
1995年 | 144篇 |
1994年 | 132篇 |
1993年 | 155篇 |
1992年 | 47篇 |
1991年 | 51篇 |
1990年 | 52篇 |
1989年 | 32篇 |
1988年 | 38篇 |
1987年 | 41篇 |
1986年 | 49篇 |
1985年 | 56篇 |
1984年 | 46篇 |
1983年 | 46篇 |
1982年 | 51篇 |
1981年 | 56篇 |
1980年 | 77篇 |
1979年 | 58篇 |
1978年 | 50篇 |
1977年 | 89篇 |
1976年 | 129篇 |
1975年 | 44篇 |
1974年 | 27篇 |
1973年 | 22篇 |
1972年 | 18篇 |
1970年 | 17篇 |
排序方式: 共有3979条查询结果,搜索用时 15 毫秒
21.
22.
Obtaining shorter regular expressions from finite-state automata 总被引:1,自引:0,他引:1
We consider the use of state elimination to construct shorter regular expressions from finite-state automata (FAs). Although state elimination is an intuitive method for computing regular expressions from FAs, the resulting regular expressions are often very long and complicated. We examine the minimization of FAs to obtain shorter expressions first. Then, we introduce vertical chopping based on bridge states and horizontal chopping based on the structural properties of given FAs. We prove that we should not eliminate bridge states until we eliminate all non-bridge states to obtain shorter regular expressions. In addition, we suggest heuristics for state elimination that leads to shorter regular expressions based on vertical chopping and horizontal chopping. 相似文献
23.
Saksenaea vasiformis, a zygomycete belonging to the order Mucorales, is a rare cause of zygomycosis with 17 cases documented world-wide. It usually infects the immunocompromised or traumatized and has a high mortality rate. Because of its failure to sporulate under normal laboratory conditions it may be difficult to identify. We describe here an unusual case report of Saksenaea vasiformis with sporulation and identification within a week using a modified sporulation technique. 相似文献
24.
25.
FY Ghauri JK Nicholson BC Sweatman J Wood CR Beddell JC Lindon NJ Cairns 《Canadian Metallurgical Quarterly》1993,6(2):163-167
Mutations of ras oncogenes in 37 human stomach cancers and 13 adenomas were investigated with regard to the histological phenotypes using polymerase chain reaction (PCR), allele-specific oligonucleotide hybridization and/or direct sequencing of the PCR products. The ras mutation was found only in one case (2.7%), the histology of which was poorly differentiated adenocarcinoma. We found no mutation in stomach adenomas. The mutation consisted of a guanine-to-adenine transition in the first base of codon 13 of c-Ki-ras which replaced wild-type glycine with serine, indicating that a putative glycine-to-aspartic acid change is not necessarily the critical event for c-Ki-ras gene activation in codon 13. These results further confirm the infrequency of ras mutation in stomach tumors and also suggest that ras mutations are not specific to the differentiated type of stomach cancer. 相似文献
26.
27.
We present a new approach to analyse the deformation of the left ventricle of the heart based on a parametric model that gives a compact representation of a set of points in a 3-D image. We present a strategy for tracking surfaces in a sequence of 3-D cardiac images. Following tracking, we then infer quantitative parameters which characterize: left ventricle motion, volume of left ventricle, ejection fraction, amplitude and twist component of cardiac motion. We explain the computation of these parameters using our model. Experimental results are shown in time sequences of two modalities of medical images, nuclear medicine and X-ray computed tomography (CT). Video sequences presenting these results are on the CD-ROM. 相似文献
28.
29.
30.
Jackson T.J. Engman E.T. Le Vine D. Schmugge T.J. Lang R. Wood E. Teng W. 《Geoscience and Remote Sensing, IEEE Transactions on》1994,32(1):201-206
MACHYDR0'90 was an experiment conducted in Pennsylvania in 1990 to study the synergistic use of remote sensors in multitemporal hydrologic studies. As part of this mission the pushbroom microwave radiometer was flown and used to produce brightness temperature maps. Verification studies and vegetation algorithms for mixed land cover areas are described 相似文献