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   14209篇
  免费   1232篇
  国内免费   762篇
电工技术   3925篇
技术理论   8篇
综合类   1439篇
化学工业   503篇
金属工艺   85篇
机械仪表   255篇
建筑科学   2014篇
矿业工程   429篇
能源动力   1709篇
轻工业   306篇
水利工程   545篇
石油天然气   378篇
武器工业   24篇
无线电   827篇
一般工业技术   733篇
冶金工业   627篇
原子能技术   29篇
自动化技术   2367篇
  2024年   30篇
  2023年   165篇
  2022年   328篇
  2021年   411篇
  2020年   482篇
  2019年   390篇
  2018年   402篇
  2017年   396篇
  2016年   494篇
  2015年   442篇
  2014年   853篇
  2013年   922篇
  2012年   834篇
  2011年   994篇
  2010年   881篇
  2009年   932篇
  2008年   978篇
  2007年   1185篇
  2006年   969篇
  2005年   806篇
  2004年   693篇
  2003年   633篇
  2002年   428篇
  2001年   381篇
  2000年   282篇
  1999年   190篇
  1998年   107篇
  1997年   89篇
  1996年   90篇
  1995年   61篇
  1994年   56篇
  1993年   32篇
  1992年   29篇
  1991年   25篇
  1990年   20篇
  1989年   19篇
  1988年   15篇
  1987年   11篇
  1986年   11篇
  1985年   25篇
  1984年   17篇
  1983年   10篇
  1982年   8篇
  1981年   10篇
  1979年   6篇
  1975年   7篇
  1972年   4篇
  1966年   6篇
  1956年   4篇
  1954年   3篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
1.
分析了静电产生的原因,阐述了粉体含能材料生产中的静电起电现象、静电的危害、静电安全性评估标准以及建立在此标准基础上的静电放电危险的评价办法,提出了粉体含能材料在生产、运输中所需要采取的静电防护措施。  相似文献   
2.
Our empirical analysis focuses on the effect of regional policies on migration attraction factors in Europe. We employ a regression discontinuity design to assess the causal relationship between the reception of large amounts of public funds and migration flows in the EU-15 regions. In highly-subsidised regions, we find a large increase in the share of foreign citizens from less-developed countries when compared to low-subsidised regions with similar pre-treatment characteristics. The analysis shows that such an increase is due to the positive impact of the European regional policy on job market opportunities as well as the improvement of public goods supply.  相似文献   
3.
Metropolitan strategic plans often focus on strengthening local employment opportunities to address the congestion and commuting issues threatening city sustainability. The success of such strategies relies on a more equitable distribution of jobs between sub-regions and can be comparatively benchmarked through one of the three related measures of employment self-sufficiency, self-containment or jobs-housing balance. However, in practice, planning policy implementation to meet these targets seldom reduces automobile commuting. This paper investigates self-containment across a range of occupation and industry types to highlight large differences in commuting and employment patterns through a case study of Perth’s Northwest sub-region, Western Australia. Its findings suggest the application of current sub-regional policy and targets within Perth may reinforce the wage and skill disadvantage of outer metropolitan sub-regions over the inner core. It recommends a more nuanced understanding of these measures taking into account the complex dynamics of both employment opportunities and commuting patterns across sub-regions of a city.  相似文献   
4.
Jatropha curcas L. has emerged in recent times as a leading energy crop in sub-Saharan Africa with over 32 countries in the region involved in its cultivation. By 2008, five countries in the region (Senegal, Nigeria, Mali, Ethiopia, and Zimbabwe) had policies promoting Jatropha cultivation. These policies were not informed by empirical evidence arising from the performance of Jatropha in the region. This paper analyses performance data of Jatropha in the region with a view to synthesizing information that is useful for evidence-based policy formulation. Production data in terms of agronomic issues and seed yields are analyzed. The results show that most of the attributes generically associated with Jatropha have not been achieved in the region and there has been inadequate research to support Jatropha cultivation. Policies supporting cultivation of Jatropha need to be informed by these observations in order to promote viable cultivation of the crop.  相似文献   
5.
The marked increase in the awareness of earthquake risk following the Canterbury earthquakes in New Zealand offered a unique opportunity to investigate the economic effect of disaster-mitigation regulations on the commercial building stock. A difference-in-differences (DD) framework was used to determine whether earthquake risk has been capitalized into the property prices of buildings constructed prior to 1976, as a response to the national policy requiring assessment and strengthening (or demolition) of the existing earthquake-prone building stock. A negative externality is found in the policy announcement on affected (pre-1970s) office and retail buildings which caused office buildings to suffer a 12.5% stigma discount. However, retail properties were less impacted suffering a 2.3% stigma loss. The value of the commercial building stock has been affected by the policy. These findings provide policy-makers with timely evidence as to the economic effects of New Zealand’s earthquake-prone buildings policy. Facing losses in property value and financial responsibility for retrofitting their assets, building owners will be looking for a workable set of regulatory and non-regulatory incentives to encourage disaster risk management and protect the built environment.  相似文献   
6.
《Oil and Energy Trends》2020,45(6):23-24
Current data on net electricity production, as well as a breakdown of production by country. Updated on a monthly basis.  相似文献   
7.
Carbon tax policy is widely adopted by many countries to curb carbon emissions. In the context of carbon tax policy, firms have more incentive to improve carbon reduction levels by reducing their carbon tax costs. However, firms need to bear carbon reduction costs that may cause shortage of capital. Thus, firms may face problems of financial constraints, which may demotivate firms to produce greener products. To address the decision‐making challenges of firms in the contexts of carbon tax policy and financial constraints, we consider a supply chain with a manufacturer who produces green products and a retailer who sells these products. Our study develops five models to investigate the two firms’ optimal wholesale price, carbon reduction level and ordering quantity, according to the manufacturer and retailer with or without financial constraints. Our goal in this study is to explore how carbon tax policy and banks’ interest rates affect the profits of the two firms, supply chain and consumer surplus. Certain managerial insights are obtained as follows. We demonstrate that carbon tax policy and banks’ interest rates demotivate the manufacturer to produce greener products and demotivate the retailer to order more products. If the interest rate to the manufacturer (retailer) is relatively low, then the manufacturer with financial constraint benefits (harms) the consumers compared with the retailer with financial constraint. Importantly, our analysis suggests that carbon tax policy harms the firms but benefits consumers, and the government in some conditions should reduce unit carbon tax.  相似文献   
8.
《Oil and Energy Trends》2020,45(12):23-24
Current data on net electricity production, as well as a breakdown of production by country. Updated on a monthly basis.  相似文献   
9.
Drawing on and developing Kingdon’s multiple streams analysis, this article examines the development of one aspect of the UK’s low cost home ownership programme: shared ownership. We demonstrate how key human and non-human policy entrepreneurs were able to set the agenda from 1973–1983 in favour of shared ownership; they neutralized the alternatives, while retaining some of their instruments; and solved a number of early problems by bringing key players into the programme. Our data-sets include a range of archival material and elite interviews. The policy entrepreneurs included John Stanley (who was the housing minister in the First Thatcher government), the National Federation of Housing Associations, and the Building Societies Association. Our development of the multiple streams analysis is to argue that documents, including the lease, act as policy entrepreneurs in their own right. The lease was central to the development of shared ownership and its transformation into a model lease enrolled other organizations, most critically the building societies.  相似文献   
10.
Abstract

In this article, we presented a method for option pricing problem under regime-switching jump-diffusion models. We have proposed a numerical method for solving a partial integro-differential equation (PIDE) for pricing European option and for solving linear complementarity problem (LCP), to evaluate the price of American options. We use implicit explicit method for time semi discretization, followed by radial basis function based finite difference (RBF-FD) method for spatial discretization to solve PIDE. The proposed method is further extended to solve the LCP by coupling it with operator splitting method. Numerical simulation is done for European and American option to demonstrate efficiency and accuracy of the proposed method.  相似文献   
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