全文获取类型
收费全文 | 441277篇 |
免费 | 42928篇 |
国内免费 | 16076篇 |
专业分类
电工技术 | 23150篇 |
技术理论 | 41篇 |
综合类 | 25370篇 |
化学工业 | 83780篇 |
金属工艺 | 23153篇 |
机械仪表 | 26459篇 |
建筑科学 | 34429篇 |
矿业工程 | 12888篇 |
能源动力 | 12002篇 |
轻工业 | 30527篇 |
水利工程 | 7194篇 |
石油天然气 | 26482篇 |
武器工业 | 3137篇 |
无线电 | 52017篇 |
一般工业技术 | 57472篇 |
冶金工业 | 22002篇 |
原子能技术 | 4163篇 |
自动化技术 | 56015篇 |
出版年
2024年 | 1671篇 |
2023年 | 6248篇 |
2022年 | 10928篇 |
2021年 | 15801篇 |
2020年 | 12788篇 |
2019年 | 12309篇 |
2018年 | 13697篇 |
2017年 | 15500篇 |
2016年 | 14276篇 |
2015年 | 18650篇 |
2014年 | 22564篇 |
2013年 | 27561篇 |
2012年 | 27333篇 |
2011年 | 29359篇 |
2010年 | 26285篇 |
2009年 | 25065篇 |
2008年 | 24101篇 |
2007年 | 23243篇 |
2006年 | 24039篇 |
2005年 | 21222篇 |
2004年 | 14347篇 |
2003年 | 12849篇 |
2002年 | 12003篇 |
2001年 | 10859篇 |
2000年 | 11249篇 |
1999年 | 12337篇 |
1998年 | 9730篇 |
1997年 | 8350篇 |
1996年 | 7647篇 |
1995年 | 6395篇 |
1994年 | 5242篇 |
1993年 | 3870篇 |
1992年 | 3081篇 |
1991年 | 2315篇 |
1990年 | 1746篇 |
1989年 | 1432篇 |
1988年 | 1151篇 |
1987年 | 803篇 |
1986年 | 589篇 |
1985年 | 437篇 |
1984年 | 286篇 |
1983年 | 203篇 |
1982年 | 214篇 |
1981年 | 146篇 |
1980年 | 115篇 |
1979年 | 59篇 |
1978年 | 28篇 |
1977年 | 26篇 |
1976年 | 40篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Shanshan Li Bing Zhang Xuxiang Feng Yewei Wu 《International journal of remote sensing》2019,40(14):5635-5650
Feature-based methods have been developed in the past decades for the registration of optical satellite images. However, it is still a challenging problem to handle well the registration between medium and high spatial resolution images due to the large difference of the spatial structural features and local details for the same objects. In this study, an automated co-registration technique is proposed that integrates an improved SIFT (I-SIFT) and a novel matching strategy called spatial consistency constraints (SCC) to cope with the large difference in spatial resolutions between the image pair. Three constraints on angle, distance, and ratio are introduced to re the initial matching features obtained by I-SIFT. Three groups of experiments were conducted to validate the effectiveness of the proposed method. The experiments used high resolution multispectral and panoramic SPOT 5/6 images and Landsat 5/8 orthorectification images. Experimental results show that the registration error lies in about 1 pixel of high-resolution images and demonstrate that the proposed I-SIFT-SCC approach is suitable for fine registration of optical satellite images from medium spatial resolution to high spatial resolution with resolution ratio up to 6. 相似文献
2.
3.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018) 下载免费PDF全文
4.
5.
6.
根据柴油机机体裂纹产生的原因,对机体裂纹缺陷进行分析,找到了机体裂纹产生的主要原因。其主要原因可概括为铸件结构、化学成分、铸件补缩条件及开箱温度等,针对裂纹的主要原因采取相应的措施后,裂纹缺陷得到了根本的控制。 相似文献
7.
8.
Efficacy of Crude and Purified Chitinases (SsChi50) Extracted from Offal Red Scorpion Fish in Biological Control of Chickpea Weevil (Callosobruchus maculatus L.) 下载免费PDF全文
9.
Quality enhancement of the abundant under‐valued crustacean,lobster krill (Munida spp.), during its chilled storage 下载免费PDF全文
Bibiana García‐Soto José M. Miranda Jorge Barros‐Velázquez Santiago P. Aubourg 《International Journal of Food Science & Technology》2015,50(3):708-716
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product. 相似文献
10.