首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2024篇
  免费   47篇
  国内免费   2篇
电工技术   6篇
综合类   1篇
化学工业   304篇
金属工艺   24篇
机械仪表   41篇
建筑科学   121篇
矿业工程   12篇
能源动力   30篇
轻工业   277篇
水利工程   28篇
石油天然气   4篇
无线电   56篇
一般工业技术   203篇
冶金工业   759篇
原子能技术   17篇
自动化技术   190篇
  2022年   10篇
  2021年   27篇
  2020年   19篇
  2019年   22篇
  2018年   21篇
  2017年   29篇
  2016年   37篇
  2015年   19篇
  2014年   28篇
  2013年   122篇
  2012年   59篇
  2011年   95篇
  2010年   73篇
  2009年   56篇
  2008年   75篇
  2007年   83篇
  2006年   82篇
  2005年   74篇
  2004年   68篇
  2003年   62篇
  2002年   54篇
  2001年   39篇
  2000年   44篇
  1999年   48篇
  1998年   56篇
  1997年   60篇
  1996年   46篇
  1995年   37篇
  1994年   34篇
  1993年   48篇
  1992年   37篇
  1991年   18篇
  1990年   36篇
  1989年   28篇
  1988年   24篇
  1987年   30篇
  1986年   25篇
  1985年   26篇
  1984年   28篇
  1983年   24篇
  1982年   23篇
  1981年   20篇
  1980年   19篇
  1979年   13篇
  1978年   13篇
  1977年   22篇
  1976年   27篇
  1975年   23篇
  1974年   16篇
  1973年   11篇
排序方式: 共有2073条查询结果,搜索用时 46 毫秒
61.
While computable general equilibrium (CGE) models are a well-established tool in economic analyses, it is often difficult to disentangle the effects of policies of interest from that of the assumptions made regarding the underlying calibration data and model parameters. To characterize the behavior of a CGE model of carbon output with respect to two of these assumptions, we perform a large-scale Monte Carlo experiment to examine its sensitivity to base year calibration data and elasticity of substitution parameters in the absence of a policy change. By examining a variety of output variables at different levels of economic and geographic aggregation, we assess how these forms of uncertainty impact the conclusions that can be drawn from the model simulations. We find greater sensitivity to uncertainty in the elasticity of substitution parameters than to uncertainty in the base-year data as the projection period increases. While many model simulations were conducted to generate large output samples, we find that few are required to capture the mean model response of the variables tested. However, characterizing standard errors and empirical probability distribution functions is not possible without a large number of simulations.  相似文献   
62.
63.
64.
Sun‐drying is a low‐cost, low‐technology fish preservation method frequently employed in developing areas. However, the process promotes lipid oxidation and its associated undesired flavours and odours. This study investigated low‐technology solutions for impact on lipid oxidation and sensory attributes of oven‐dried omena fish (Rastrineobola argentea). Two oven‐drying conditions and four doses of clove water extract ‘dip’ pretreatments were studied in a complete factorial design. Lipid oxidation in dried fish was assessed by TBARS, peroxide value and fatty acid analysis by GC‐FID. Results showed that soaking in 10 g L?1 clove water extract for 1 h and oven‐drying at 150 °C × 30 min significantly reduced TBARS and peroxide values in omena fish by 77% and 79%, respectively, and polyene index showed improved retention of long‐chain polyunsaturated fats, compared to original drying condition. Lastly, panellists of a triangle test were able to discriminate between biscuits made with the modified and original dried fish.  相似文献   
65.
66.
67.
68.
The continued increase in the demand for energy, growing recognition of climate change impacts, high oil and gas prices and the rapid depletion of fossil fuel reserves have led to an increased interest in the mass generation of electricity from renewable sources. Traditionally, this has been pursed through riverine hydropower plants, with onshore wind systems growing steadily in popularity and importance over the years. Other renewable energy resources, which were previously not economically attractive or technically feasible for large scale exploitation, are now being considered to form a significant part of the energy mix. Amongst these, marine and in particular, tidal energy resource has become a serious candidate for undergoing mass exploitation in the near future, particularly in places with a tidal range of 4 m or more. Tidal renewable energy systems are designed to extract the kinetic or potential energy flow and convert it into electricity. This can be achieved by placing tidal stream turbines in the path of high speed tidal currents or through tidal range schemes, where low head turbines are encapsulated in impoundment structures, much like in low head riverine hydropower schemes. It is thought that these systems, when implemented at scales required to generate substantial amounts of electricity, have the potential to significantly alter the tidal flow characteristics, which could have knock-on impacts on the hydro-environment. This review gathers together knowledge from different research areas to facilitate an evaluation of the potential hydro-environmental impacts of tidal renewable energy systems, with a particular focus on water quality. It highlights the relevance of hydro-environmental modelling in assessing potential impacts of proposed schemes and identifies areas where further research is needed. A case study is presented of recent modelling studies undertaken for the Severn Estuary.  相似文献   
69.
Healthcare authorities make difficult decisions about how to spend limited budgets for interventions that guarantee the best cost-efficacy ratio. We propose a novel approach for treatment decision-making, OMES—in French: Objectif thérapeutique Modèle Effet Seuil (in English: Therapeutic Objective–Threshold–Effect Model; TOTEM). This approach takes into consideration results from clinical trials, adjusted for the patients'' characteristics in treatment decision-making. We compared OMES with the French clinical practice guidelines (CPGs) for the management of dyslipidemia with statin in a computer-generated realistic virtual population, representing the adult French population, in terms of the number of all-cause deaths avoided (number of avoided events: NAEs) under treatment and the individual absolute benefit. The total budget was fixed at the annual amount reimbursed by the French social security for statins. With the CPGs, the NAEs was 292 for an annual cost of 122.54 M€ compared with 443 with OMES. For a fixed NAEs, OMES reduced costs by 50% (60.53 M€ yr−1). The results demonstrate that OMES is at least as good as, and even better than, the standard CPGs when applied to the same population. Hence the OMES approach is a practical, useful alternative which will help to overcome the limitations of treatment decision-making based uniquely on CPGs.  相似文献   
70.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号