全文获取类型
收费全文 | 83821篇 |
免费 | 7397篇 |
国内免费 | 4405篇 |
专业分类
电工技术 | 4864篇 |
技术理论 | 1篇 |
综合类 | 7362篇 |
化学工业 | 13240篇 |
金属工艺 | 4348篇 |
机械仪表 | 5017篇 |
建筑科学 | 5637篇 |
矿业工程 | 1770篇 |
能源动力 | 2310篇 |
轻工业 | 7616篇 |
水利工程 | 1665篇 |
石油天然气 | 3041篇 |
武器工业 | 620篇 |
无线电 | 10373篇 |
一般工业技术 | 9266篇 |
冶金工业 | 4596篇 |
原子能技术 | 1135篇 |
自动化技术 | 12762篇 |
出版年
2024年 | 280篇 |
2023年 | 993篇 |
2022年 | 1906篇 |
2021年 | 2738篇 |
2020年 | 2102篇 |
2019年 | 1865篇 |
2018年 | 2038篇 |
2017年 | 2242篇 |
2016年 | 2258篇 |
2015年 | 2985篇 |
2014年 | 3988篇 |
2013年 | 4851篇 |
2012年 | 5614篇 |
2011年 | 6084篇 |
2010年 | 5589篇 |
2009年 | 5450篇 |
2008年 | 5455篇 |
2007年 | 5184篇 |
2006年 | 4985篇 |
2005年 | 4173篇 |
2004年 | 3456篇 |
2003年 | 3084篇 |
2002年 | 3682篇 |
2001年 | 3176篇 |
2000年 | 2194篇 |
1999年 | 1659篇 |
1998年 | 1473篇 |
1997年 | 1124篇 |
1996年 | 972篇 |
1995年 | 760篇 |
1994年 | 606篇 |
1993年 | 474篇 |
1992年 | 348篇 |
1991年 | 287篇 |
1990年 | 242篇 |
1989年 | 187篇 |
1988年 | 150篇 |
1987年 | 117篇 |
1986年 | 75篇 |
1985年 | 99篇 |
1984年 | 82篇 |
1983年 | 71篇 |
1982年 | 59篇 |
1981年 | 54篇 |
1980年 | 53篇 |
1979年 | 37篇 |
1978年 | 24篇 |
1977年 | 58篇 |
1976年 | 86篇 |
1975年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
川西彭州地区三叠系雷口坡组雷四上亚段潮坪相薄储层识别难度极大。围绕如何从复合地震强反射中区分并识别上、下两套储层面临的地球物理难题,采用先“分”后“合”的研究思路,基于实际地层结构及不同储层叠加样式建立正演模型,利用全波场波动方程正演模拟技术,剖析了不同主频条件下薄储层的地震响应特征,通过波形差异化分析,从复合地震响应中“剥离”出了两套储层所引起的地震响应特征及变化规律,明确了两套储层在不同频带下的地震识别标志和识别方法,为该区强反射界面干扰下两套薄互层储层辨识机理分析及精准预测奠定了基础。基于不同频带下薄储层辨识机理的分析结果,定性预测了薄储层平面展布,提出了深层潮坪相薄储层识别和预测难题的解决方案,为该区地震资料品质评价、面向薄储层的地震采集技术设计、地震资料处理及薄储层预测提供了依据和指导。 相似文献
23.
There are many potential causes of corrosion in animal buildings. Animals exhale large quantities of moisture into the air creating high relative humidity in the building if the moisture is not properly vented. High humidity increases the potential for condensation. In addition, ammonia may be found in large quantities in animal buildings. Ammonia is released from manure and urine. In addition, ammonium chloride is used as a nitrogen source in fertilisers. In this study, the atmospheric corrosion of hot-dip-galvanised steel and zinc alloy-coated steel such as zinc–aluminium and zinc–aluminium–magnesium has been studied in atmospheres containing different levels of ammonia. Investigations have also been conducted at different levels of ammonium chloride. The results are discussed in view of the mechanisms of corrosion of zinc and zinc alloy-coated steel in ammonia and ammonium chloride-containing environments. 相似文献
24.
25.
Baofeng Hou Hong He Ruixiu Jia Meilong Fu Yanbin Cao Shaoqun He Liwen Luo Youqing Huang 《应用聚合物科学杂志》2019,136(10):47161
The synthesis and performance of a novel temperature-tolerant foamed resin for enhanced oil recovery were investigated using various methods, including infrared, NMR, scanning electron microscopy (SEM), and displacement experiments. Polycondensation of furfuryl alcohol prepolymers was confirmed by the infrared and NMR results. The poor temperature tolerance of furfuryl alcohol prepolymers after gelation at high temperatures is mainly due to the fracture of furan rings. The addition of ester additives is an effective method of increasing the temperature tolerance of the prepared foamed resins and can effectively reduce the weight-loss rate of the polycondensation products. The SEM results show that the skeleton structure of the foamed resin remains intact after high-temperature treatment. Thus, the novel plugging agent system has excellent thermal stability and still has a high strength (>0.8 MPa) after high-temperature aging treatment for 40 days, giving the prepared foamed resin a good plugging performance (plugging rate > 91%) at 250 °C. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47161. 相似文献
26.
27.
28.
Hoang V. Le Phuong T. Pham Ly T. Le Anh D. Nguyen Ngoc Quang Tran Phong D. Tran 《International Journal of Hydrogen Energy》2021,46(44):22852-22863
WO3 is a potential material candidate for construction of photoanode for solar driven water splitting. In this work, μm-thick porous WO3 photoanode is prepared by depositing a stable ink made of WO3 nanoparticles and Aristoflex velvet polymer in water using the doctor blade technique, followed by a sintering in air. The nature of WO3 nanoparticles, its loading mass on F-doped tin oxide electrode as well as sintering temperature are examined in order to optimize the photocatalytic activity of the resultant WO3 photoanode. The operation of WO3 photoanode is investigated by varying the light illumination direction and light incident intensity as well as changing the nature of the electrolyte. Dissolved tungsten in electrolyte is quantified by ICP-MS providing insights into the influences of electrolyte nature and operating conditions to the corrosion of WO3. It is proposed that the H2O2 and OH. radical generated as by-products of the photo-driven water oxidation on the photoanode surface are harmful species that accelerate the dissolution of WO3. 相似文献
29.
现阶段的语义解析方法大部分都基于组合语义,这类方法的核心就是词典。词典是词汇的集合,词汇定义了自然语言句子中词语到知识库本体中谓词的映射。语义解析一直面临着词典中词汇覆盖度不够的问题。针对此问题,该文在现有工作的基础上,提出了基于桥连接的词典学习方法,该方法能够在训练中自动引入新的词汇并加以学习,为了进一步提高新学习到的词汇的准确度,该文设计了新的词语—二元谓词的特征模板,并使用基于投票机制的核心词典获取方法。该文在两个公开数据集(WebQuestions和Free917)上进行了对比实验,实验结果表明,该文方法能够学习到新的词汇,提高词汇的覆盖度,进而提升语义解析系统的性能,特别是召回率。 相似文献
30.
Process object is the instance of process. Vertexes and edges are in the graph of process object. There are different types of the object itself and the associations between object. For the large-scale data, there are many changes reflected. Recently, how to find appropriate real-time data for process object becomes a hot research topic. Data sampling is a kind of finding c hanges o f p rocess o bjects. There i s r equirements f or s ampling to be adaptive to underlying distribution of data stream. In this paper, we have proposed a adaptive data sampling mechanism to find a ppropriate d ata t o m odeling. F irst o f all, we use concept drift to make the partition of the life cycle of process object. Then, entity community detection is proposed to find changes. Finally, we propose stream-based real-time optimization of data sampling. Contributions of this paper are concept drift, community detection, and stream-based real-time computing. Experiments show the effectiveness and feasibility of our proposed adaptive data sampling mechanism for process object. 相似文献