全文获取类型
收费全文 | 34230篇 |
免费 | 3655篇 |
国内免费 | 1323篇 |
专业分类
电工技术 | 10521篇 |
技术理论 | 2篇 |
综合类 | 2268篇 |
化学工业 | 2858篇 |
金属工艺 | 1459篇 |
机械仪表 | 760篇 |
建筑科学 | 5511篇 |
矿业工程 | 1602篇 |
能源动力 | 958篇 |
轻工业 | 1247篇 |
水利工程 | 1874篇 |
石油天然气 | 1633篇 |
武器工业 | 136篇 |
无线电 | 2193篇 |
一般工业技术 | 1526篇 |
冶金工业 | 1325篇 |
原子能技术 | 376篇 |
自动化技术 | 2959篇 |
出版年
2024年 | 114篇 |
2023年 | 307篇 |
2022年 | 768篇 |
2021年 | 945篇 |
2020年 | 901篇 |
2019年 | 674篇 |
2018年 | 608篇 |
2017年 | 827篇 |
2016年 | 946篇 |
2015年 | 1135篇 |
2014年 | 2613篇 |
2013年 | 1738篇 |
2012年 | 2651篇 |
2011年 | 3021篇 |
2010年 | 2332篇 |
2009年 | 2342篇 |
2008年 | 2042篇 |
2007年 | 2453篇 |
2006年 | 2360篇 |
2005年 | 1929篇 |
2004年 | 1576篇 |
2003年 | 1488篇 |
2002年 | 1190篇 |
2001年 | 1062篇 |
2000年 | 889篇 |
1999年 | 642篇 |
1998年 | 396篇 |
1997年 | 283篇 |
1996年 | 237篇 |
1995年 | 216篇 |
1994年 | 123篇 |
1993年 | 72篇 |
1992年 | 57篇 |
1991年 | 44篇 |
1990年 | 33篇 |
1989年 | 34篇 |
1988年 | 40篇 |
1987年 | 15篇 |
1986年 | 18篇 |
1985年 | 18篇 |
1984年 | 26篇 |
1983年 | 12篇 |
1982年 | 5篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1963年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
冯鹏一 《信息通信技术与政策》2020,(1):12-15
以电信用户入网协议为切入点,电信用户的携号转网行为应受到《合同法》《消费者权益保护法》等私法规范的保护与限制。该行为引起的格式条款解释、合同终止、违约责任、损失赔偿等问题,不能仅靠《电信条例》等公法规范来调整。应当积极引导广大消费者用户以私法领域相关规定为依据,转变争议解决思维,拓宽纠纷处理途径,合理选择维权手段,以保护自身合法民事权益,与行业监管部门共同推动电信行业有序发展。 相似文献
3.
4.
文章通过对黑龙江省高效节水现状,存在问题的分析,结合黑龙江省高效节水发展的支撑能力,阐述黑龙江省节水增粮目标、任务及总体布局,为黑龙江省2012—2015年节水增粮实施提供依据。 相似文献
5.
从电焊机自身电气特点及建筑工地工作环境入手,探讨电焊机安全技术的实施方法。分析电焊机安全隐患及事故的分类以及电焊机在使用过程中产生危险的原因。介绍电焊机在安装以及作业过程中的安全措施。 相似文献
6.
7.
8.
A double optimal projection method that involves projections for intra-cluster and inter-cluster dimensionality reduction are proposed for video fingerprinting. The video is initially set as a graph with frames as its vertices in a high-dimensional space. A similarity measure that can compute the weights of the edges is then proposed. Subsequently, the video frames are partitioned into different clusters based on the graph model. Double optimal projection is used to explore the optimal mapping points in a low-dimensional space to reduce the video dimensions. The statistics and geometrical fingerprints are generated to determine whether a query video is copied from one of the videos in the database. During matching, the video can be roughly matched by utilizing the statistics fingerprint. Further matching is thereafter performed in the corresponding group using geometrical fingerprints. Experimental results show the good performance of the proposed video fingerprinting method in robustness and discrimination. 相似文献
9.
In this paper, limiting factors for increased use of biomethane as a transportation fuel are studied. The aim of this research is to recognize and estimate the limiting factors for biomethane utilization in the transportation sector. The limiting factors are studied by using calculation models from Life cycle perspective and literature reviews. According to the results, the main limiting factors can be classified into the following categories: production potential, technology, economy or policy. For biomethane utilization in Finland, the main limiting factors seem to be the lack of distribution infrastructure in northern parts of the country and the uncertain economical feasibility for agricultural biomass producers and for vehicle owners. From the political perspective, the external costs for petrol operated vehicles are higher than for biomethane operated vehicles. Reductions from the external costs could be used by political decisions as a base to support the growth of biomethane in the transportation sector which could lead to GHG emission reductions. A similar systematic approach can also be used to study limiting factors for other transportation energy systems. 相似文献
10.
《Energy Policy》2015
Electric vehicles (EVs) are considered alternatives to internal combustion engines due to their energy efficiency and contribution to CO2 mitigation. The adoption of EVs depends on consumer preferences, including cost, social status and driving habits, although it is agreed that current and expected costs play a major role. We use a partial equilibrium model that minimizes total energy system costs to assess whether EVs can be a cost-effective option for the consumers of each EU27 member state up to 2050, focusing on the impact of different vehicle investment costs and CO2 mitigation targets. We found that for an EU-wide greenhouse gas emission reduction cap of 40% and 70% by 2050 vis-à-vis 1990 emissions, battery electric vehicles (BEVs) are cost-effective in the EU only by 2030 and only if their costs are 30% lower than currently expected. At the EU level, vehicle costs and the capability to deliver both short- and long-distance mobility are the main drivers of BEV deployment. Other drivers include each state’s national mobility patterns and the cost-effectiveness of alternative mitigation options, both in the transport sector, such as plug-in hybrid electric vehicles (PHEVs) or biofuels, and in other sectors, such as renewable electricity. 相似文献