全文获取类型
收费全文 | 521901篇 |
免费 | 9028篇 |
国内免费 | 1793篇 |
专业分类
电工技术 | 8583篇 |
综合类 | 2646篇 |
化学工业 | 78780篇 |
金属工艺 | 21612篇 |
机械仪表 | 17234篇 |
建筑科学 | 11684篇 |
矿业工程 | 2783篇 |
能源动力 | 13484篇 |
轻工业 | 38944篇 |
水利工程 | 5832篇 |
石油天然气 | 8401篇 |
武器工业 | 23篇 |
无线电 | 59470篇 |
一般工业技术 | 104351篇 |
冶金工业 | 86441篇 |
原子能技术 | 9542篇 |
自动化技术 | 62912篇 |
出版年
2022年 | 3108篇 |
2021年 | 4991篇 |
2020年 | 3872篇 |
2019年 | 4838篇 |
2018年 | 21502篇 |
2017年 | 20432篇 |
2016年 | 17945篇 |
2015年 | 6206篇 |
2014年 | 8923篇 |
2013年 | 23619篇 |
2012年 | 16747篇 |
2011年 | 26161篇 |
2010年 | 21710篇 |
2009年 | 20545篇 |
2008年 | 22044篇 |
2007年 | 22570篇 |
2006年 | 13585篇 |
2005年 | 13139篇 |
2004年 | 12370篇 |
2003年 | 12259篇 |
2002年 | 11037篇 |
2001年 | 10355篇 |
2000年 | 9784篇 |
1999年 | 10087篇 |
1998年 | 27134篇 |
1997年 | 18625篇 |
1996年 | 14056篇 |
1995年 | 10250篇 |
1994年 | 8944篇 |
1993年 | 9010篇 |
1992年 | 6283篇 |
1991年 | 5932篇 |
1990年 | 5841篇 |
1989年 | 5492篇 |
1988年 | 5235篇 |
1987年 | 4587篇 |
1986年 | 4450篇 |
1985年 | 4980篇 |
1984年 | 4567篇 |
1983年 | 4094篇 |
1982年 | 3789篇 |
1981年 | 3893篇 |
1980年 | 3596篇 |
1979年 | 3407篇 |
1978年 | 3415篇 |
1977年 | 4056篇 |
1976年 | 5496篇 |
1975年 | 2916篇 |
1974年 | 2723篇 |
1973年 | 2810篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Lihua Lou Weijie Yu Ronald J. Kendall Ernest Smith Seshadri S. Ramkumar 《应用聚合物科学杂志》2020,137(30):49213
A tensile properties testing study was conducted to understand the influence of thickness, cross-head speed (speed of testing), gauge length (GL; specimen test length), and sample shape on important tensile properties of polyvinyl alcohol (PVA) nanofiber webs. The effects of each testing parameter on load at break, extension at break, Young's modulus, and tensile stress–strain curve of PVA nanofiber webs are analyzed. The Welch two sample t-tests show the significant difference among tested data. Using interaction plots, two-way analysis of variance, and margin mean plots, the interaction effects among testing parameters have been analyzed. Of all the factors, cross-head speed, the interaction among GL, and sample thickness (GL: Thickness) and the interaction among GL, testing speed and sample thickness (GL: Speed: Thickness) have significant influence on the tensile properties of PVA nanofiber webs. Moreover, the hypothesized model of mechanism of tensile strain–stress curve of PVA nanofiber webs has been proposed. Based on the model, the tensile strain–stress curve can be split into three stages: linear elastic, partial break up, and complete breakage. This study will provide a better understanding of tensile testing parameters' effects and their interaction effects on the tensile properties of nanowebs. 相似文献
102.
L. S. Belevskii M. A. Levantsevich R. R. Dema L. V. Deryabina T. V. Usataya O. R. Latypov 《Russian Engineering Research》2020,40(5):390-395
The machining of metal surfaces and the application of functional coatings by means of a flexible tool (a rotating wire brush) is considered. Frictional cladding may be applied on metal-cutting machines by means of simple attachments or manual angle grinders. 相似文献
103.
104.
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
105.
106.
107.
108.
High Temperature - The influence of heating from 260 to 400 K on the structure and mechanism of the formation of a molecular water film adsorbed on the walls of a plane fracture with the width of... 相似文献
109.
110.