全文获取类型
收费全文 | 88472篇 |
免费 | 1115篇 |
国内免费 | 432篇 |
专业分类
电工技术 | 1179篇 |
综合类 | 2333篇 |
化学工业 | 12820篇 |
金属工艺 | 4911篇 |
机械仪表 | 3143篇 |
建筑科学 | 2336篇 |
矿业工程 | 562篇 |
能源动力 | 1336篇 |
轻工业 | 4074篇 |
水利工程 | 1285篇 |
石油天然气 | 348篇 |
无线电 | 9483篇 |
一般工业技术 | 17125篇 |
冶金工业 | 2809篇 |
原子能技术 | 466篇 |
自动化技术 | 25809篇 |
出版年
2022年 | 60篇 |
2021年 | 97篇 |
2020年 | 54篇 |
2019年 | 66篇 |
2018年 | 14500篇 |
2017年 | 13423篇 |
2016年 | 10040篇 |
2015年 | 676篇 |
2014年 | 370篇 |
2013年 | 503篇 |
2012年 | 3305篇 |
2011年 | 9668篇 |
2010年 | 8495篇 |
2009年 | 5796篇 |
2008年 | 7051篇 |
2007年 | 8000篇 |
2006年 | 310篇 |
2005年 | 1418篇 |
2004年 | 1294篇 |
2003年 | 1322篇 |
2002年 | 694篇 |
2001年 | 200篇 |
2000年 | 271篇 |
1999年 | 153篇 |
1998年 | 161篇 |
1997年 | 105篇 |
1996年 | 115篇 |
1995年 | 63篇 |
1994年 | 92篇 |
1993年 | 77篇 |
1992年 | 67篇 |
1991年 | 98篇 |
1990年 | 54篇 |
1989年 | 77篇 |
1988年 | 74篇 |
1986年 | 73篇 |
1985年 | 56篇 |
1984年 | 53篇 |
1983年 | 57篇 |
1982年 | 61篇 |
1981年 | 47篇 |
1980年 | 43篇 |
1979年 | 41篇 |
1978年 | 41篇 |
1968年 | 46篇 |
1967年 | 40篇 |
1966年 | 43篇 |
1965年 | 44篇 |
1955年 | 63篇 |
1954年 | 68篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
Shouko Nishida Masaya Shibano Hiroshi Kamitakahara Toshiyuki Takano 《International journal of molecular sciences》2015,16(12):29093-29102
We recently observed that the decanoylation of N-phenylthiocarbamoyl chitosan (2) with a mixture of decanoic anhydride and pyridine at 60 °C for 24 h afforded N,N-(decanoyl)phenythiocarbamoyl-/2-isothiocynato chitosan decanoate (3b) rather than the expected product N,N-(decanoyl)phenylthiocarbamoyl chitosan decanoate (3a). This result suggested that some of the N,N-(decanoyl)phenylthiocarmbamoyl groups had been converted to isothiocyanate groups during the decanoylation process. The subsequent reaction of compound 3b with aniline gave N,N-(decanoyl)phenylthiocarbamoyl/N-phenylthiocarbamoyl chitosan decanoate (4) in high yield. A solution of compound 4 in CHCl3 was then added to a solution of copper decanoate (5) in the same solvent, and the resulting mixture was cast onto a glass plate to give a cast film. The film was annealed at 200 °C in an oven to give a greenish film, which showed good near-infrared absorption characteristic in the range of 800–2200 nm. 相似文献
2.
3.
Mobile software applications have to cope with a particular environment that involves small size, limited resources, high autonomy requirements, competitive business models and many other challenges. To provide development guidelines that respond to these needs, several practices have been introduced; however, it is not clear how these guidelines may contribute to solve the issues present in the mobile domain. Furthermore, the rapid evolution of the mobile ecosystem challenges many of the premises upon which the proposed practices were designed. In this paper, we present a survey of the literature on software assurance practices for mobile applications, with the objective of describing them and assessing their contribution and success. We identified, organized and reviewed a body of research that spans in three levels: software development processes, software product assurance practices, and software implementation practices. By carrying out this literature survey, we reviewed the different approaches that researchers on Software Engineering have provided to address the needs that raise in the mobile software development arena. Moreover, we review the evolution of these practices, identifying how the constant changes and modernization of the mobile execution environment has impacted the methods proposed in the literature. Finally, we introduced discussion on the application of these practices in a real productive setting, opening an area for further research that may determine if practitioners have followed the proposed assurance paradigms. 相似文献
4.
A Synthetic Transcriptional Activator of Genes Associated with the Retina in Human Dermal Fibroblasts
下载免费PDF全文
![点击此处可从《Chembiochem : a European journal of chemical biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
5.
This paper presents an integrated passive damping approach in hybrid metal-CFRP parts for structural applications. In this concept a viscoelastic material is embedded in the joint zone of the hybrid component. To examine the connection strength single-lap-joint specimens were produced and tested and the influence of the used material combinations, different surface structures, and different process parameters i.e. the moment of cross-linking were evaluated. Afterwards, the metal-CFRP hybrids were tested in quasi-static tests to assess their connection strength and failure behaviour. Dynamic cyclic tensile tests with step-wise increased loading conditions were performed to determine the specimens damping behaviour and to estimate their fatigue performance. Finally, these results are compared to a state of the art metal-CFRP hybrid with rivets connecting both materials. 相似文献
6.
In this paper, we consider the classical finite mixture model, which is an effective tool for modeling lifetime distributions for random samples from heterogeneous populations. We discuss new results on stochastic comparison for two finite mixtures when each of them is drawn from one of the following semiparametric families, i.e., proportional hazards, accelerated lifetime and proportional reversed hazards. 相似文献
7.
8.
9.
Variations of Incomplete Open Cubes is the major project by the twentieth-century conceptual artist Sol LeWitt. In this paper we interpret the enumerative component of the project as embeddings of graphs. This formulation permits use of an algorithm to check the completeness of the list of the structures produced by the artist. Our conclusion is that the artist found the correct number of structures (that is, 122), but that his list contains a mistake in the presentation of a pair of incomplete cubes, a discovery that appears not to have been noted before. 相似文献
10.