全文获取类型
收费全文 | 2865篇 |
免费 | 86篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 58篇 |
综合类 | 4篇 |
化学工业 | 991篇 |
金属工艺 | 52篇 |
机械仪表 | 32篇 |
建筑科学 | 189篇 |
矿业工程 | 30篇 |
能源动力 | 32篇 |
轻工业 | 356篇 |
水利工程 | 10篇 |
石油天然气 | 1篇 |
无线电 | 148篇 |
一般工业技术 | 396篇 |
冶金工业 | 221篇 |
原子能技术 | 36篇 |
自动化技术 | 396篇 |
出版年
2022年 | 30篇 |
2021年 | 38篇 |
2020年 | 30篇 |
2019年 | 29篇 |
2018年 | 41篇 |
2017年 | 41篇 |
2016年 | 65篇 |
2015年 | 84篇 |
2014年 | 72篇 |
2013年 | 118篇 |
2012年 | 113篇 |
2011年 | 152篇 |
2010年 | 107篇 |
2009年 | 106篇 |
2008年 | 109篇 |
2007年 | 134篇 |
2006年 | 113篇 |
2005年 | 106篇 |
2004年 | 101篇 |
2003年 | 70篇 |
2002年 | 66篇 |
2001年 | 50篇 |
2000年 | 50篇 |
1999年 | 50篇 |
1998年 | 67篇 |
1997年 | 54篇 |
1996年 | 55篇 |
1995年 | 52篇 |
1994年 | 66篇 |
1993年 | 37篇 |
1992年 | 42篇 |
1991年 | 40篇 |
1990年 | 26篇 |
1989年 | 36篇 |
1988年 | 22篇 |
1987年 | 28篇 |
1986年 | 30篇 |
1985年 | 36篇 |
1984年 | 36篇 |
1983年 | 31篇 |
1982年 | 31篇 |
1981年 | 26篇 |
1980年 | 27篇 |
1978年 | 24篇 |
1977年 | 27篇 |
1976年 | 25篇 |
1975年 | 37篇 |
1974年 | 20篇 |
1973年 | 23篇 |
1970年 | 30篇 |
排序方式: 共有2952条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
85.
Tunable Quantum Confinement in Ultrathin,Optically Active Semiconductor Nanowires Via Reverse‐Reaction Growth 下载免费PDF全文
86.
87.
Many empirical studies across various industry sectors show a high failure rate of mergers and acquisitions (M&A), suggesting that this instrument of corporate development is rather risky. Since engineering consulting firms usually have a low tangible asset base as well as good educated and highly mobile professionals, carrying out an M&A transaction in this particular service sector creates an even higher risk. It is evident from the relevant construction and engineering literature that a large number of engineering consulting firms engage in M&A for their corporate development. Owing to the uniqueness of that service sector combined with the high failure rate of M&A, a survey among the top 100 engineering consulting firms in Europe was conducted to investigate the motives behind M&A transactions. Findings suggest that diversification into new service/client markets as well as the penetration into new geographic markets were the most important motives. Further, increasing the firm's market share and the acceleration of growth were the next most popularly rated motives, while tax reasons or spending the firm's excess cash were both seen as relatively unimportant motives. The results show that - compared to other industry sectors - engineering consulting firms had some very different motives or another emphasis was placed on those motives when conducting an M&A transaction. Results also show that some motives were just as important for engineering consulting firms as for firms of other industry sectors, for example the increase of market share or the acceleration of firm growth. 相似文献
88.
Private investment subsidies are a key instrument for regional policy making to foster the economic development in lagging regions. In this paper, we analyze their effect on labor productivity growth for German labor market regions for the period from 1994 to 2006. A spatially augmented multiplicative interaction model based on neoclassical growth theory is used, which allows us to assess the marginal effect of regional policy proxied by overall payments of the main German regional development program on the region’s convergence speed conditional on its initial income position as well as policy-related spillovers from its spatial neighborhood. Our results show a statistically significant positive effect of regional policy on labor productivity growth, which increases, the further away the supported region is from its steady-state income level, and the more grants are provided to its geographical neighborhood. The latter effect highlights the existence of positive spatial spillover effects from regional policy in Germany, which enhance the attractiveness of the whole macro region for private sector investments. The additional growth stimulus provided by a 1 % increase in the region’s funding volume is thereby related to an up to 0.3 % gain in terms of labor productivity growth. For regions with the highest initial gaps to steady-state income in the sample distribution, the regional policy stimulus accounts for almost 8 % of the regions’ productivity growth performance. 相似文献
89.
Chalissery Jaime M. Gries Regine Alamsetti Santosh K. Ardiel Madison J. Gries Gerhard 《Journal of chemical ecology》2022,48(3):302-311
Journal of Chemical Ecology - Four species of Tetramorium pavement ants are known to guide foraging activities of nestmates via trail pheromones secreted from the poison gland of worker ants, but... 相似文献
90.
Amna Youssef Ramzy Ahmed Mohammed Moneeb El‐Sabbagh Leif Steuernagel Gerhard Ziegmann Dieter Meiners 《应用聚合物科学杂志》2014,131(3)
The presented study investigates the flow length and the corresponding fiber content distribution in the injection‐moulded natural fiber reinforced thermoplastics and its relation to fiber type and processing parameters such as injection pressure, temperature, injection rate and mould tempering by increasing die temperature. In this research, polypropylene compounds with nominally 30 wt % hemp and sisal fibers are investigated. The influence of the injection pressure (500 and 1000 bar), melt temperature (180°C, 200°C, and 220°C), and die temperature (23°C and 80°C) on the fiber content distribution all over the sample is investigated. An increasing linear trend of fiber content along the spiral length is observed as an evidence of a fiber/polymer multiflow system. A pattern for fiber content distribution with respect to the fiber length along the injected spiral can be distinguished, where the longer fibers are usually found at the end of the injected part and the shorter fibers remain near mould entrance point. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39861. 相似文献