全文获取类型
收费全文 | 3693篇 |
免费 | 71篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 36篇 |
综合类 | 1篇 |
化学工业 | 488篇 |
金属工艺 | 28篇 |
机械仪表 | 43篇 |
建筑科学 | 141篇 |
矿业工程 | 4篇 |
能源动力 | 68篇 |
轻工业 | 269篇 |
水利工程 | 18篇 |
石油天然气 | 8篇 |
无线电 | 352篇 |
一般工业技术 | 428篇 |
冶金工业 | 1560篇 |
原子能技术 | 41篇 |
自动化技术 | 280篇 |
出版年
2021年 | 30篇 |
2019年 | 27篇 |
2018年 | 30篇 |
2017年 | 36篇 |
2016年 | 34篇 |
2015年 | 29篇 |
2014年 | 48篇 |
2013年 | 104篇 |
2012年 | 60篇 |
2011年 | 103篇 |
2010年 | 72篇 |
2009年 | 82篇 |
2008年 | 84篇 |
2007年 | 95篇 |
2006年 | 95篇 |
2005年 | 77篇 |
2004年 | 58篇 |
2003年 | 55篇 |
2002年 | 49篇 |
2001年 | 56篇 |
2000年 | 56篇 |
1999年 | 74篇 |
1998年 | 430篇 |
1997年 | 279篇 |
1996年 | 187篇 |
1995年 | 137篇 |
1994年 | 112篇 |
1993年 | 114篇 |
1992年 | 50篇 |
1991年 | 55篇 |
1990年 | 57篇 |
1989年 | 56篇 |
1988年 | 49篇 |
1987年 | 44篇 |
1986年 | 46篇 |
1985年 | 57篇 |
1984年 | 42篇 |
1983年 | 43篇 |
1982年 | 26篇 |
1981年 | 31篇 |
1980年 | 39篇 |
1979年 | 31篇 |
1978年 | 34篇 |
1977年 | 63篇 |
1976年 | 129篇 |
1975年 | 35篇 |
1974年 | 35篇 |
1973年 | 29篇 |
1971年 | 32篇 |
1970年 | 24篇 |
排序方式: 共有3765条查询结果,搜索用时 31 毫秒
111.
Alexander W. Richter Nathaniel A. Throckmorton Todd B. Walker 《Computational Economics》2014,44(4):445-476
Policy function iteration methods for solving and analyzing dynamic stochastic general equilibrium models are powerful from a theoretical and computational perspective. Despite obvious theoretical appeal, significant startup costs and a reliance on grid-based methods have limited the use of policy function iteration as a solution algorithm. We reduce these costs by providing a user-friendly suite of MATLAB functions that introduce multi-core processing and Fortran via MATLAB’s executable function. Within the class of policy function iteration methods, we advocate using time iteration with linear interpolation. We examine a canonical real business cycle model and a new Keynesian model that features regime switching in policy parameters, Epstein–Zin preferences, and monetary policy that occasionally hits the zero-lower bound on the nominal interest rate to highlight the attractiveness of our methodology. We compare our advocated approach to other familiar iteration and approximation methods, highlighting the tradeoffs between accuracy, speed and robustness. 相似文献
112.
113.
114.
115.
Energy audits can provide businesses with valuable information and advice about their current energy use and costs and where changes can be made to improve both the environmental performance of the business and their triple bottom line. There is literature on the use of energy audits outside Australia, but little provision of empirical data that would help a business decide whether engagement is economically viable. This paper reports on 49 SME energy audits in Australia, and the results verify that economic returns can vary significantly and alone are not a reason for most SMEs to act. Thus, more will need to be done to engage them as their collective impact on the environment should be a catalyst for action and support from stakeholders. 相似文献
116.
Juri Matinheikki Kirsi Aaltonen Derek Walker 《International Journal of Project Management》2019,37(2):298-317
Public infrastructure projects must comply with the divergent and even conflicting demands of multiple institutional logics causing institutional complexity. Despite the increasing interest in different forms of complexities in projects, we lack empirical illustrations and rigorous theorizing of mechanisms for responding to institutional complexity. This paper demonstrates how public buyers of a tunnel construction project formed a hybrid organization of a multi-party project alliance to respond to institutional complexity. We delineate a process of temporary hybridization through which the competing logics of a bureaucratic state, corporate market, and multiple professions were combined within the temporary project alliance organization. Such temporary hybridization not only focused on selective coupling with external demands but also mitigated internal tensions. Our findings emphasize a blended organizational structure, jointly formed governance and incentive systems, and the facilitation of social interaction to build a temporary yet sustainable hybrid organization capable of combining conflicting institutional logics. 相似文献
117.
118.
Clay Hunt Marley Zachariasen David Driscoll Stephen Sofie Robert Walker 《International Journal of Hydrogen Energy》2018,43(32):15531-15536
Degradation rates of electrical current during constant voltage operation of SOFCs with anodes made using NiO precursor powders from two different manufacturers with and without the addition of aluminum titanate (ALT) added by either mechanical mixing or anode infiltration have been quantified using a novel MATLAB algorithm. Because the algorithm has been used to quantify degradation rates for many different SOFC tests, it is thought that the method can be applied to most measured SOFC data to quantify the instantaneous cell degradation rate as a function of time for the entire SOFC performance measurement. Degradation rates determined at different times have been plotted against varying concentrations of ALT addition, facilitating the estimation of optimum ALT concentration for SOFC anodes made with NiO from a specific manufacturer. The algorithm used to determine degradation rates is available upon request to the corresponding author. 相似文献
119.
The core of Frobury Farmhouse, Kingsclere, Hampshire, is an aisled base cruck open hall built in c.1334/5d (Bridge and Miles, “Tree-Ring Dates from Oxford” (2015), 107) with a crown-post roof and passing braces in the closed trusses. Above all this is a full set of rafters from a mid-thirteenth-century aisled hall that had passing braces on all the trusses, tree-ring dated to 1263–8d, probably the predecessor to the base cruck hall. The 1334/5d arcade plates have edged halved and bridled scarf joints, the earliest tree-ring-dated example of these so far. These joints also show that all the arcade posts and the base cruck were erected first, before the arcade plates were laid from west to east on the north front arcade posts and from east to west on the rear posts. 相似文献
120.
Claire Fortenberry Michael Walker Audrey Dang Arun Loka Gauri Date Karolina Cysneiros de Carvalho Glenn Morrison Brent Williams 《Indoor air》2019,29(5):761-779
The air composition and reactivity from outdoor and indoor mixing field campaign was conducted to investigate the impacts of natural ventilation (ie, window opening and closing) on indoor air quality. In this study, a thermal desorption aerosol gas chromatograph (TAG) obtained measurements of indoor particle‐ and gas‐phase semi‐ and intermediately volatile organic compounds both inside and outside a single‐family test home. Together with measurements from a suite of instruments, we use TAG data to evaluate changes in indoor particles and gases at three natural ventilation periods. Positive matrix factorization was performed on TAG and adsorbent tube data to explore five distinct chemical and physical processes occurring in the indoor environment. Outdoor‐to‐indoor transport is observed for sulfate, isoprene epoxydiols, polycyclic aromatic hydrocarbons, and heavy alkanes. Dilution of indoor species is observed for volatile, non‐reactive species including methylcyclohexane and decamethylcyclopentasiloxane. Window opening drives enhanced emissions of semi‐ and intermediately volatile species including TXIB, DEET, diethyl phthalate, and carvone from indoor surfaces. Formation via enhanced oxidation was observed for nonanal and 2‐decanone when outdoor oxidants entered the home. Finally, oxidative depletion of gas‐phase terpenes (eg, limonene and α‐pinene) was anticipated but not observed due to limited measurement resolution and dynamically changing conditions. 相似文献