全文获取类型
收费全文 | 149707篇 |
免费 | 15748篇 |
国内免费 | 10676篇 |
专业分类
电工技术 | 8957篇 |
技术理论 | 10篇 |
综合类 | 15889篇 |
化学工业 | 23106篇 |
金属工艺 | 4295篇 |
机械仪表 | 6477篇 |
建筑科学 | 26947篇 |
矿业工程 | 7761篇 |
能源动力 | 6954篇 |
轻工业 | 8441篇 |
水利工程 | 22218篇 |
石油天然气 | 9976篇 |
武器工业 | 1226篇 |
无线电 | 4958篇 |
一般工业技术 | 9631篇 |
冶金工业 | 4972篇 |
原子能技术 | 1612篇 |
自动化技术 | 12701篇 |
出版年
2024年 | 438篇 |
2023年 | 1933篇 |
2022年 | 3686篇 |
2021年 | 4532篇 |
2020年 | 4745篇 |
2019年 | 4034篇 |
2018年 | 3905篇 |
2017年 | 4762篇 |
2016年 | 5475篇 |
2015年 | 5523篇 |
2014年 | 9405篇 |
2013年 | 9189篇 |
2012年 | 11790篇 |
2011年 | 11616篇 |
2010年 | 8865篇 |
2009年 | 9139篇 |
2008年 | 8229篇 |
2007年 | 10646篇 |
2006年 | 9666篇 |
2005年 | 8631篇 |
2004年 | 6899篇 |
2003年 | 6022篇 |
2002年 | 5087篇 |
2001年 | 4224篇 |
2000年 | 3605篇 |
1999年 | 2813篇 |
1998年 | 2167篇 |
1997年 | 1755篇 |
1996年 | 1413篇 |
1995年 | 1240篇 |
1994年 | 967篇 |
1993年 | 717篇 |
1992年 | 584篇 |
1991年 | 457篇 |
1990年 | 370篇 |
1989年 | 364篇 |
1988年 | 225篇 |
1987年 | 206篇 |
1986年 | 146篇 |
1985年 | 141篇 |
1984年 | 144篇 |
1983年 | 84篇 |
1982年 | 61篇 |
1981年 | 31篇 |
1980年 | 47篇 |
1979年 | 73篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1959年 | 10篇 |
1951年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
SPEEK/cSMM membrane for simultaneous electricity generation and wastewater treatment in microbial fuel cell 下载免费PDF全文
33.
Qingna Gong Songtao Cao Yu Zhou Ruixin Wang Weizhou Jiao 《International Journal of Hydrogen Energy》2021,46(41):21442-21453
Ni2P nanoparticles and CdS nanorods were grew together on a mesoporous g-C3N4 through a facile in-situ solvothermal approach. Under visible light (λ > 400 nm), the as-prepared ternary PCN–CdS-5% Ni2P composite displays a high H2 evolution rate with 2905.86 μmol g?1 h?1, which is about 14, 18 and 279 times that of PCN–CdS, PCN–Ni2P and PCN, respectively. The enhanced photocatalytic activity is mainly attributed to the improved separation efficiency of the photocarriers by the type II PCN–CdS heterojunction and the effective extraction of photogenerated electrons by Ni2P. Meanwhile, Ni2P acts as co-catalyst to provide the photocatalytic active site for hydrogen reduction. In addition, PCN–CdS-5% Ni2P composite exerts good stability in 12-h cycles. 相似文献
34.
Chengxiao Zhao Zupeng Chen Run Shi Xiaofei Yang Tierui Zhang 《Advanced materials (Deerfield Beach, Fla.)》2020,32(28):1907296
With the ambition of solving the challenges of the shortage of fossil fuels and their associated environmental pollution, visible-light-driven splitting of water into hydrogen and oxygen using semiconductor photocatalysts has emerged as a promising technology to provide environmentally friendly energy vectors. Among the current library of developed photocatalysts, organic conjugated polymers present unique advantages of sufficient light-absorption efficiency, excellent stability, tunable electronic properties, and economic applicability. As a class of rising photocatalysts, organic conjugated polymers offer high flexibility in tuning the framework of the backbone and porosity to fulfill the requirements for photocatalytic applications. In the past decade, significant progress has been made in visible-light-driven water splitting employing organic conjugated polymers. The recent development of the structural design principles of organic conjugated polymers (including linear, crosslinked, and supramolecular self-assembled polymers) toward efficient photocatalytic hydrogen evolution, oxygen evolution, and overall water splitting is described, thus providing a comprehensive reference for the field. Finally, current challenges and perspectives are also discussed. 相似文献
35.
本文以喷淋液滴在空气环境下运动特性为工程背景,建立单个液滴在常温、常压空气环境中的动量方程,分析液滴沉降特性、追赶特性及运动轨迹行为。计算结果表明,不同喷淋液滴初始条件下,短时间内存在重力大于曳力和重力小于曳力两种情况,但最终减速液滴均会达到受力平衡状态;液滴离开喷淋头后,垂向位移均迅速增大,液滴粒径越大、初始速度越大,垂向位移增长的速率也越大,达到相同位移的用时越短;液滴尺寸、初始速度相差越大,液滴追赶所用的时间越短,追赶位移越小,液滴尺寸、初始速度越接近,液滴追赶所用的时间越长,追赶位移越大;液滴初始速度越大、初始直径越大、喷射角度越大,横向速度消失越慢,达到的横向位移越大,喷射液滴覆盖的面积也越大。计算结果有助于优化工程实际中喷淋系统的设计与布置。 相似文献
36.
《Geotextiles and Geomembranes》2020,48(6):897-911
Dynamic responses of the geosynthetic-encased stone column (GESC) supported embankment under traffic loads have become a hot topic. This study investigates the responses of GESC improved ground under vertical cyclic loading. A series of laboratory tests in a designed model test tank have been carried out with different loading parameters (varied loading amplitudes and frequencies), different column dimensions (varied encasement lengths and column diameters). In the tests, the soil-column stress distribution, accumulated settlement of loading plate, excess pore water pressure in the surrounding soil and lateral bulging of the stone column are monitored. Experimental results indicate that the vertical stress on the stone column increases with the increment of encasement length, and decreases with the increment of column diameter, loading amplitude and loading frequency. The increasing stress on the surrounding soil leads to a greater accumulated settlement of the loading plate and excess pore water pressure, while the increasing stress on the column leads to larger lateral bulging of the column. Excess pore water pressure dissipates effectively through vertical and horizontal drainage channels provided by the stone column and the sand bed. The geosynthetic encasement prevents the clay from obstructing the drainage channel by filtration and guarantees the drainage effect. 相似文献
37.
为检查工程质量,查找输水系统可能存在的问题并消除隐患,保障电站安全运行,福建仙游抽水蓄能电站在投产发电前,要对输水发电系统进行充水试验与放空排水试验,在试验过程中监测输水系统的应力、应变与渗漏水情况。本文以尾水系统为例,介绍了试验所应具备的工程条件、工作程序及技术要求、试验成果分析和存在问题处理等。试验表明,仙游抽水蓄能电站尾水系统设计合理,施工质量优良,结构可靠,可供同类工程参考与借鉴。 相似文献
38.
In this paper, the dynamic behaviors on the basis of simulation for high-purity heat integrated air separation column (HIASC) are studied. A nonlinear generic model control (GMC) scheme is proposed based on the nonlinear behavior analyses of a HIASC process, and an adaptive generic model control (AGMC) scheme is further presented to correct the model parameters online. Related internal model control (IMC) scheme and multi-loop PID (M-PID) scheme are also developed as the comparative base. The comparative researches are carried out among these linear and nonlinear control schemes in detail. The simulation research results show that the proposed AGMC schemes present advantages in both servo control and regulatory control for the high-purity HIASC. 相似文献
39.
40.