全文获取类型
收费全文 | 124394篇 |
免费 | 10890篇 |
国内免费 | 6061篇 |
专业分类
电工技术 | 7045篇 |
技术理论 | 8篇 |
综合类 | 10055篇 |
化学工业 | 20389篇 |
金属工艺 | 6941篇 |
机械仪表 | 8025篇 |
建筑科学 | 8457篇 |
矿业工程 | 3176篇 |
能源动力 | 3656篇 |
轻工业 | 9620篇 |
水利工程 | 2240篇 |
石油天然气 | 5792篇 |
武器工业 | 989篇 |
无线电 | 15190篇 |
一般工业技术 | 14902篇 |
冶金工业 | 5533篇 |
原子能技术 | 1711篇 |
自动化技术 | 17616篇 |
出版年
2024年 | 391篇 |
2023年 | 1631篇 |
2022年 | 2849篇 |
2021年 | 4344篇 |
2020年 | 3290篇 |
2019年 | 2876篇 |
2018年 | 3178篇 |
2017年 | 3642篇 |
2016年 | 3468篇 |
2015年 | 4637篇 |
2014年 | 6174篇 |
2013年 | 7516篇 |
2012年 | 8452篇 |
2011年 | 9140篇 |
2010年 | 8169篇 |
2009年 | 7990篇 |
2008年 | 7976篇 |
2007年 | 7511篇 |
2006年 | 7327篇 |
2005年 | 6178篇 |
2004年 | 4829篇 |
2003年 | 4309篇 |
2002年 | 4824篇 |
2001年 | 4198篇 |
2000年 | 3252篇 |
1999年 | 2675篇 |
1998年 | 2006篇 |
1997年 | 1672篇 |
1996年 | 1518篇 |
1995年 | 1221篇 |
1994年 | 952篇 |
1993年 | 671篇 |
1992年 | 553篇 |
1991年 | 411篇 |
1990年 | 362篇 |
1989年 | 266篇 |
1988年 | 219篇 |
1987年 | 143篇 |
1986年 | 93篇 |
1985年 | 88篇 |
1984年 | 69篇 |
1983年 | 55篇 |
1982年 | 43篇 |
1981年 | 36篇 |
1980年 | 25篇 |
1979年 | 21篇 |
1978年 | 9篇 |
1977年 | 14篇 |
1976年 | 21篇 |
1959年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
33.
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
34.
35.
Bing Yang Yu Zhou Wenjie Yu Song Zhang Hongxiang Chen Ju Ye 《Polymer International》2019,68(4):675-683
In order to improve the dispersity and stability of the nano‐SiO2 aqueous system with high solid content, a kind of polyacrylic acid dispersant with methoxysilicon end groups (KH590‐PAA) was synthesized by photopolymerization of acrylic acid (AA) initiated with (3‐mercaptopropyl)trimethoxysilane (KH590). After adding KH590‐PAA into the nano‐SiO2 aqueous dispersion system (20 wt% solid content), the viscosity and the curing time of the system were measured with a rotational viscometer and the inverted bottle method. Moreover, the dispersion mechanism of KH590‐PAA for the nano‐SiO2 aqueous system was researched by measuring the adsorption capacity, the particle size and the zeta potential of the nanoparticles with a conductivity meter, dynamic light scattering, SEM and TEM, respectively. The results showed that the methoxysilicon groups in KH590‐PAA could react with hydroxyl groups on the surface of nano‐SiO2 in the process of stirring, which enhanced the adsorption capacity of the dispersant and then increased the surface charge of the particles. Therefore, electrostatic repulsion and steric hindrance effects between the SiO2 nanoparticles could be further enhanced by adding the KH590‐PAA dispersant, and then the nano‐SiO2 aqueous system exhibited better dispersity and stability. Besides, the dispersion properties of SiO2 nanoparticles in water were closely related to the addition amount and the molecular weight of the KH590‐PAA dispersant. © 2018 Society of Chemical Industry 相似文献
36.
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
37.
38.
39.
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
40.
Wei-Fei Hu Shuo Chen Hong-Chao Hao Hong Jiang 《American Institute of Chemical Engineers》2022,68(11):e17879
Herein, we propose a novel method to enhance the photoreactivity of an MOF catalyst by grafting isocyanate bonds ( NCO) and sulfhydryl-complexed copper ( SCu) onto ZIF-8 (NIF-SCu). The grafting process intercalated interlayer bands between the conduction and valence bands of ZIF-8, thereby providing a “ladder” for facile electron transition. The extreme improvement in the photoreactivity of NIF-SCu could be attributed to the enhancement in light responses in the range of 350–450 nm by NCO groups and the widening of the visible light range of the MOF by SCu groups. The formation of staggered energy levels in NIF-SCu could also narrow the band gap, lower the resistance, and facilitate the transfer of photogenerated carriers, thereby generating electrons with strong reduction potential in the SCu conduction band. This study provides a new strategy for improving or even endowing the photoactivity of environmental functional materials with wide bandgaps. 相似文献