全文获取类型
收费全文 | 98166篇 |
免费 | 1791篇 |
国内免费 | 434篇 |
专业分类
电工技术 | 915篇 |
综合类 | 2357篇 |
化学工业 | 14599篇 |
金属工艺 | 5035篇 |
机械仪表 | 3313篇 |
建筑科学 | 2815篇 |
矿业工程 | 604篇 |
能源动力 | 1596篇 |
轻工业 | 4754篇 |
水利工程 | 1381篇 |
石油天然气 | 392篇 |
无线电 | 10281篇 |
一般工业技术 | 19050篇 |
冶金工业 | 4831篇 |
原子能技术 | 370篇 |
自动化技术 | 28098篇 |
出版年
2023年 | 165篇 |
2022年 | 359篇 |
2021年 | 574篇 |
2020年 | 376篇 |
2019年 | 383篇 |
2018年 | 14804篇 |
2017年 | 13695篇 |
2016年 | 10378篇 |
2015年 | 1056篇 |
2014年 | 808篇 |
2013年 | 1237篇 |
2012年 | 4065篇 |
2011年 | 10453篇 |
2010年 | 9004篇 |
2009年 | 6223篇 |
2008年 | 7495篇 |
2007年 | 8465篇 |
2006年 | 687篇 |
2005年 | 1689篇 |
2004年 | 1482篇 |
2003年 | 1537篇 |
2002年 | 865篇 |
2001年 | 306篇 |
2000年 | 361篇 |
1999年 | 259篇 |
1998年 | 262篇 |
1997年 | 211篇 |
1996年 | 225篇 |
1995年 | 185篇 |
1994年 | 164篇 |
1993年 | 155篇 |
1992年 | 130篇 |
1991年 | 96篇 |
1990年 | 122篇 |
1989年 | 116篇 |
1988年 | 89篇 |
1987年 | 93篇 |
1986年 | 100篇 |
1985年 | 100篇 |
1984年 | 88篇 |
1983年 | 76篇 |
1982年 | 96篇 |
1981年 | 90篇 |
1980年 | 71篇 |
1979年 | 70篇 |
1978年 | 62篇 |
1977年 | 74篇 |
1976年 | 61篇 |
1955年 | 71篇 |
1954年 | 79篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Alexandra Kodadová Zuzana Vitková Petra Herdová Anton Ťažký Jarmila Oremusová Daniel Grančai 《Drug development and industrial pharmacy》2015,41(7):1080-1088
This study deals with the formulation of natural drugs into hydrogels. For the first time, compounds from the sage essential oil were formulated into chitosan hydrogels. A sample preparation procedure for hydrophobic volatile analytes present in a hydrophilic water matrix along with an analytical method based on the gas chromatography coupled with the mass spectrometry (GC-MS) was developed and applied for the evaluation of the identity and quantity of essential oil components in the hydrogels and saline samples. The experimental results revealed that the chitosan hydrogels are suitable for the formulation of sage essential oil. The monoterpene release can be effectively controlled by both chitosan and caffeine concentration in the hydrogels. Permeation experiment, based on a hydrogel with the optimized composition [3.5% (w/w) sage essential oil, 2.0% (w/w) caffeine, 2.5% (w/w) chitosan and 0.1% (w/w) Tween-80] in donor compartment, saline solution in acceptor compartment, and semi-permeable cellophane membrane, demonstrated the useful permeation selectivity. Here, (according to lipophilicity) an enhanced permeation of the bicyclic monoterpenes with antiflogistic and antiseptic properties (eucalyptol, camphor and borneol) and, at the same time, suppressed permeation of toxic thujone (not exceeding its permitted applicable concentration) was observed. These properties highlight the pharmaceutical importance of the developed chitosan hydrogel formulating sage essential oil in the dermal applications. 相似文献
3.
4.
5.
6.
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
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.
Evaluation of the effect of processing on cocoa polyphenols: antiradical activity,anthocyanins and procyanidins profiling from raw beans to chocolate 下载免费PDF全文
Matteo Bordiga Monica Locatelli Fabiano Travaglia Jean Daniel Coïsson Giuseppe Mazza Marco Arlorio 《International Journal of Food Science & Technology》2015,50(3):840-848
The content and composition of anthocyanins and procyanidins in fermented cocoa beans (from different geographic origins: Ecuador, Cameroon, Ivory Coast, Ghana and Nigeria), roasted nibs, cocoa mass and chocolate were determined, beside the determination of the total antiradical capacity. Concerning geographic origin, cocoa beans and processed products from Ecuador showed the highest levels of anthocyanins, followed by Nigeria and Cameroon. Generally, as cocoa beans were further processed, the levels of anthocyanins and flavan‐3‐ols decreased. The largest observed losses of phenolics occurred during roasting. A progressive decreasing trend in polyphenol concentration was observed in the other processed samples as well. Despite the original content of polyphenols in raw cocoa beans, technological processes imply a significant impact on cocoa quality, confirming the need of specific optimisation to obtain high value chocolate. 相似文献