全文获取类型
收费全文 | 102879篇 |
免费 | 2098篇 |
国内免费 | 554篇 |
专业分类
电工技术 | 1162篇 |
综合类 | 2391篇 |
化学工业 | 16157篇 |
金属工艺 | 5218篇 |
机械仪表 | 3625篇 |
建筑科学 | 2873篇 |
矿业工程 | 586篇 |
能源动力 | 2496篇 |
轻工业 | 5478篇 |
水利工程 | 1474篇 |
石油天然气 | 700篇 |
武器工业 | 8篇 |
无线电 | 11282篇 |
一般工业技术 | 19748篇 |
冶金工业 | 3544篇 |
原子能技术 | 413篇 |
自动化技术 | 28376篇 |
出版年
2024年 | 85篇 |
2023年 | 433篇 |
2022年 | 958篇 |
2021年 | 1347篇 |
2020年 | 1092篇 |
2019年 | 1144篇 |
2018年 | 15410篇 |
2017年 | 14154篇 |
2016年 | 10874篇 |
2015年 | 1283篇 |
2014年 | 1308篇 |
2013年 | 2101篇 |
2012年 | 4328篇 |
2011年 | 10607篇 |
2010年 | 9068篇 |
2009年 | 6317篇 |
2008年 | 7339篇 |
2007年 | 8258篇 |
2006年 | 576篇 |
2005年 | 1538篇 |
2004年 | 1412篇 |
2003年 | 1412篇 |
2002年 | 768篇 |
2001年 | 246篇 |
2000年 | 329篇 |
1999年 | 210篇 |
1998年 | 307篇 |
1997年 | 249篇 |
1996年 | 211篇 |
1995年 | 157篇 |
1994年 | 115篇 |
1993年 | 117篇 |
1992年 | 97篇 |
1991年 | 83篇 |
1990年 | 69篇 |
1989年 | 74篇 |
1988年 | 78篇 |
1987年 | 51篇 |
1986年 | 60篇 |
1985年 | 70篇 |
1984年 | 75篇 |
1983年 | 68篇 |
1982年 | 47篇 |
1980年 | 47篇 |
1976年 | 57篇 |
1968年 | 52篇 |
1966年 | 44篇 |
1965年 | 44篇 |
1955年 | 64篇 |
1954年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Do individual factors matter? A survey of scientists’ patenting in Portuguese public research organisations 总被引:1,自引:0,他引:1
Paula Susana Figueiredo Moutinho Margarida Fontes Manuel Mira Godinho 《Scientometrics》2007,70(2):355-377
This paper addresses scientists’ behaviour regarding the patenting of knowledge produced in universities and other public
sector research organisations (PSROs). Recent years have witnessed a rapid growth in patenting and licensing activities by
PSROs. We argue that the whole process depends to a certain extent on scientists’ willingness to disclose their inventions.
Given this assumption, we conduct research into individual behaviour in order to understand scientists’ views concerning the
patenting of their research results. Data from a questionnaire survey of Portuguese researchers from nine PSROs in life sciences
and biotechnology is presented and analysed and complemented with in-depth interviews. The results reveal that overall the
scientists surveyed show a low propensity to become involved in patenting and licensing activities, despite the fact that
the majority had no “ethical” objections to the disclosure of their inventions and the commercial exploitation of these. Perceptions
about the impacts of these activities on certain fundamental aspects of knowledge production and dissemination are however
divergent. This may account for the low participation levels. Furthermore, most scientists perceived the personal benefits
deriving from this type of activity to be low. Similarly, the majority also believed that there are many difficulties associated
with the patenting process and that they receive limited support from their organisations, which lack the proper competences
and structures to assist with patenting and licensing. 相似文献
142.
143.
144.
145.
146.
147.
148.
149.
Titanium oxides were reduced to metallic titanium using the liquid calcium floating on the molten CaCl2. A part of Ca dissolved into CaCl2 and reacted with TiO2 settled below CaCl2. The by-product CaO also dissolved by about 20 mol pct into CaCl2, which was effective in reducing the oxygen concentration in the obtained Ti particles. The compositional region in the Ca-CaCl2-CaO system was examined for the less oxygen contamination in Ti and the better handling in leaching. A large amount of the
residual calcium oxidized the titanium powder in leaching. The metallic Ti powder less than 1000 mass ppm oxygen could be
obtained only for 3.6 ks using 5 to 7 mol pct Ca-CaCl2 at 1173 K. The powder was slightly sintered like sponge, and contained approximately 1500 ppm Ca. The anatase phae, the intermediate
product in the refining process of TiO2, could be also supplied as raw material as well as rutile. 相似文献
150.
The corrosion behaviour of nitrogen-containing austenitic stainless steel in methanol containing different concentrations
of H2SO4, HCl, LiCl and H2SO4 + HCl has been investigated using a potentiostatic polarization method. The cathodic reaction in the H2SO4, HCl and H2SO4 + HCl solutions was proton reduction whereas in the neutral LiCl solution, oxygen reduction was the predominant cathodic
reaction. Active, passive and transpassive behaviours were observed only for higher concentrations of H2SO4 (0.01–2.0 M) due to the inherent water content. A cathodic loop, characterized by measured negative current in the anodic
region, was also observed in solutions, in which the concentration of H2SO4 was 1.0 M or higher. The relative stability of the passive films decreased as the H2SO4 concentration increased, and thus the steel suffered from mild pitting corrosion. In the chloride environment, the rate of
corrosion increased as the Cl− ion concentration increased. The presence of acid along with Cl− ions enhanced corrosion, and the corrosion rate increased significantly. The steel suffered from mild intergranular corrosion
in acidic chloride solutions of methanol. In the H2SO4 + HCl solutions, passive films were only formed when the H2SO4 to HCl concentration ratio was greater than ∼10:1. 相似文献