全文获取类型
收费全文 | 70647篇 |
免费 | 6796篇 |
国内免费 | 3313篇 |
专业分类
电工技术 | 4214篇 |
技术理论 | 2篇 |
综合类 | 4572篇 |
化学工业 | 11706篇 |
金属工艺 | 4307篇 |
机械仪表 | 4553篇 |
建筑科学 | 5394篇 |
矿业工程 | 2556篇 |
能源动力 | 1900篇 |
轻工业 | 4454篇 |
水利工程 | 1268篇 |
石油天然气 | 4440篇 |
武器工业 | 595篇 |
无线电 | 8385篇 |
一般工业技术 | 8540篇 |
冶金工业 | 3411篇 |
原子能技术 | 725篇 |
自动化技术 | 9734篇 |
出版年
2024年 | 440篇 |
2023年 | 1361篇 |
2022年 | 2229篇 |
2021年 | 3126篇 |
2020年 | 2330篇 |
2019年 | 2015篇 |
2018年 | 2230篇 |
2017年 | 2398篇 |
2016年 | 2204篇 |
2015年 | 2840篇 |
2014年 | 3422篇 |
2013年 | 4048篇 |
2012年 | 4543篇 |
2011年 | 4993篇 |
2010年 | 4141篇 |
2009年 | 3898篇 |
2008年 | 3785篇 |
2007年 | 3626篇 |
2006年 | 4007篇 |
2005年 | 3283篇 |
2004年 | 2299篇 |
2003年 | 1959篇 |
2002年 | 1736篇 |
2001年 | 1557篇 |
2000年 | 1689篇 |
1999年 | 1900篇 |
1998年 | 1601篇 |
1997年 | 1364篇 |
1996年 | 1215篇 |
1995年 | 1021篇 |
1994年 | 877篇 |
1993年 | 594篇 |
1992年 | 451篇 |
1991年 | 387篇 |
1990年 | 275篇 |
1989年 | 226篇 |
1988年 | 195篇 |
1987年 | 127篇 |
1986年 | 99篇 |
1985年 | 65篇 |
1984年 | 33篇 |
1983年 | 20篇 |
1982年 | 32篇 |
1981年 | 16篇 |
1980年 | 24篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 14篇 |
1975年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
Yanlong Shi Xiaojuan Feng Haiyu Guan Jiahua Zhang Zhongai Hu 《International Journal of Hydrogen Energy》2021,46(12):8557-8566
Constructing high-efficient and nonprecious electrocatalysts is of primary importance for improving the efficiency of water splitting. Herein, a novel sunflower plate-like NiFe2O4/CoNi–S nanosheet heterostructure was fabricated via facile hydrothermal and electrodeposition methods. The as-fabricated NiFe2O4/CoNi–S heterostructure array exhibits remarkable bifunctional catalytic activity and stability toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in alkaline media. It presents a small overpotential of 219 mV and 149 mV for OER and HER, respectively, to produce a current density of 10 mA cm?2. More significantly, when the obtained electrodes are used as both the cathode and anode in an electrolyzer, a voltage of 1.57 V is gained at 10 mA cm?2, with superior stability for 72 h. Such outstanding properties are ascribed to: the 3D porous network structure, which exposes more active sites and accelerates mass transfer and gas bubble emission; the high conductivity of CoNi–S, which provides faster charge transport and thus promotes the electrocatalytic reaction of the composites; and the effective interface engineering between NiFe2O4 (excellent performance for OER) and CoNi–S (high activity for HER), which leads to a shorter transport pathway and thus expedites electron transfer. This work provides a new strategy for designing efficient and inexpensive electrocatalysts for water splitting. 相似文献
55.
Tingen Zhu Wenping Li Qiqing Wang Yanbo Hu Kaifang Fan Jiafa Du 《Mine Water and the Environment》2020,39(1):57-67
A method to calculate the height of a water-conducting fractured zone (HWCFZ) was developed based on the plate and shell theory, and the development of the HWCFZ in bedrock and Q2l loess strata is discussed in detail. First, the subsidence-deflection curve equation of the overlying stratum is theoretically derived, and then the ultimate deflection and free space height of rock strata are calculated. Moreover, the strata tensile strain is calculated by using integral calculus. In addition, the failure state of the rock is analyzed by comparing the theoretically calculated tensile strain with the experimentally measured yield tensile strain, allowing one to attain the maximum value of HWCFZ. This approach was tested at the Jinjitan coal mine; the theoretically predicted, experimentally measured, and numerically computed maximum HWCFZ values were 189.5, 187.3, and 188.5 m, respectively, demonstrating the accuracy of the proposed method. These results are highly significant for safe and environment-friendly coal mining in northwest Shaanxi, China. 相似文献
56.
Design and Fabrication of Concentration‐Gradient Generators with Two and Three Inlets in Microfluidic Chips
下载免费PDF全文
![点击此处可从《化学工程与技术》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A simple and low‐cost method for designing and fabricating concentration‐gradient generators with two and three inlets is proposed which can generate different concentration gradients at varying flow velocities. The microchannel structure was designed in S‐shape and left‐right symmetry. The concentration‐gradient generator was simulated based on the finite element method. The microchannels were processed on a computer numerical control (CNC) engraving and milling machine on poly(methylmethacrylate) substrate, and then two concentration‐gradient generators were fabricated by hot bonding technology. The results of experiment and simulation were compared to prove the feasibility of the method. Flow velocity was an important factor for generating different concentration gradients. The concentration‐gradient profiles of the generators with two and three inlets present approximately linear and quadratic curves. 相似文献
57.
为降低烟草中噁霉灵检测中的基质干扰,提高检测灵敏度和和稳定性,通过试验建立了以QuEChERS为样品前处理方法、液相色谱串联质谱仪为检测仪器的烟草中噁霉灵残留检测方法。样品加水浸润后,经丙酮提取、盐析试剂包除水、石墨化炭黑除杂后,采用Agilent ZORBAX 300SB-C8液相色谱柱(2.1 mm×100 mm,1.8 μm)分离,甲醇-水程序洗脱,ESI雾化,串联质谱MRM检测。结果发现,该方法在0.0025~0.0500 mg/L范围内线性良好,决定系数r2=0.9996,定量检测限1.06 μg/L,回收率在90.8%~92.0%之间,相对标准偏差为5.1%。运用该方法测定烟草中的噁霉灵,操作简单,检测精度高,满足CORESTA对烟草农残检测的要求。 相似文献
59.
60.
The in-situ fabrication of an electron-blocking layer between the Ba-containing anode and the ceria-based electrolyte is an effective approach in suppressing the internal electronic leakage in ceria-based solid oxide fuel cell (SOFC). To improve the thickness of the electron-blocking layer and to research the effect of the layer thickness on the improvement of SOFC, a Ba-containing compound (0.6NiO-0.4BaZr0.1Ce0.7Y0.2O3-δ) modified by Y stabilized zirconia (YSZ) was employed as a composite anode in this research. SEM analyses demonstrated that the thickness of the interlayer can be simply controlled by regulating the proportion of YSZ at anode. The in-situ formed interlayer in the cell with the anode modified by 20?mol% YSZ possesses a thickness of 0.9?µm which is more suitable for the cell achieving an enhanced performance. 相似文献