全文获取类型
收费全文 | 7524篇 |
免费 | 982篇 |
国内免费 | 496篇 |
专业分类
电工技术 | 642篇 |
综合类 | 926篇 |
化学工业 | 487篇 |
金属工艺 | 271篇 |
机械仪表 | 485篇 |
建筑科学 | 684篇 |
矿业工程 | 402篇 |
能源动力 | 249篇 |
轻工业 | 296篇 |
水利工程 | 196篇 |
石油天然气 | 482篇 |
武器工业 | 138篇 |
无线电 | 1263篇 |
一般工业技术 | 568篇 |
冶金工业 | 457篇 |
原子能技术 | 77篇 |
自动化技术 | 1379篇 |
出版年
2024年 | 8篇 |
2023年 | 109篇 |
2022年 | 165篇 |
2021年 | 251篇 |
2020年 | 236篇 |
2019年 | 220篇 |
2018年 | 208篇 |
2017年 | 251篇 |
2016年 | 309篇 |
2015年 | 275篇 |
2014年 | 442篇 |
2013年 | 472篇 |
2012年 | 530篇 |
2011年 | 565篇 |
2010年 | 467篇 |
2009年 | 499篇 |
2008年 | 447篇 |
2007年 | 546篇 |
2006年 | 477篇 |
2005年 | 401篇 |
2004年 | 383篇 |
2003年 | 323篇 |
2002年 | 260篇 |
2001年 | 227篇 |
2000年 | 194篇 |
1999年 | 137篇 |
1998年 | 92篇 |
1997年 | 88篇 |
1996年 | 74篇 |
1995年 | 49篇 |
1994年 | 70篇 |
1993年 | 39篇 |
1992年 | 32篇 |
1991年 | 38篇 |
1990年 | 26篇 |
1989年 | 28篇 |
1988年 | 11篇 |
1987年 | 12篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 7篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1959年 | 2篇 |
1957年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有9002条查询结果,搜索用时 15 毫秒
21.
石灰窑沟铁矿区位于赤峰市北西约80 km处,地处西拉木伦多金属成矿带的南侧,区域位于内蒙古地轴东段与内蒙海西褶皱带接触带,Ⅲ级构造单元为云雾山隆起的北东端和赤峰—铭山大断裂2条构造单元的分界线处,本矿床围岩蚀变具有分带性,是一个受断裂和褶皱复合控制的矽卡岩型矿床。为探讨该矿区的地质特征及找矿标志,通过近几年对本区地质勘查工作的总结分析,认为该矿床为矽卡岩型矿床,围绕构造发育部位,岩体与地层接触带及附近且与高精度磁测异常套合区是主要的找矿标志。 相似文献
22.
23.
《Measurement》2015
For the purpose of measuring free form surfaces of some key parts in the aviation field accurately and effectively, such as blades, a non-contact optical coordinate measuring system is set up in the paper. A laser displacement sensor is mounted on the Z axis of a CMM via a turntable and adjusted to the suitable orientation according to the shape of the target surface. The combination of optical sensor and CMM can reach the full potential of them both. To enable the laser sensor to perform measurement in every direction, a calibration method used to determine the laser beam direction based on a standard sphere is proposed, the principle of which is analyzed in detail in the paper. In the calibration procedure, the sensor moves at an equal step along X, Y and Z axes respectively and then equation sets are established to calculate the unit direction vector of the line which the laser beam is on. In the process of solving the unknown quantities, a new parameter substitution method is applied. Finally, a gauging block and a sphere with known size are used to verify the method. As the experimental results show, the measuring errors in several directions are all smaller than 0.05 mm, which manifests that the calibration method proposed can meet the requirements of reverse engineering. 相似文献
24.
测向误差的减小一直以来都是无线电测向精度提高的一个难点,对于不同的测向体制所采用的减小测向误差的方法都不尽相同。本文主要介绍的是相关干涉仪测向体制的基本原理以及通过内插法的应用来减小测向误差的方法。 相似文献
25.
《International Journal of Hydrogen Energy》2022,47(10):6799-6810
This study investigates the effect of non-uniform distribution of the air inlet flow rate and change of air flowing direction on the thermal stress of a solid oxide fuel cell stack with cross-flow configuration. This study considers three patterns of air inlet flow rate in the transverse direction of each stack, and five patterns of air inlet flow rate in the stacking direction. The software package for simulation is reliable through an accuracy comparison, and it analyzes the current density, temperature, and thermal stress distribution of a SOFC stack with 20 layers. The results show that the progressively increasing profile of the air inlet flow rate along the x direction drops the cell thermal stress of a SOFC unit. Moreover, the non-uniform profile of air inlet flow rate in the stacking direction affects the position of the region with high thermal stress of the SOFC stack, and changing flow direction of the air obviously drops down the thermal stress without affecting the power generation of the SOFC stack. 相似文献
26.
Ibdal Satar Mimi Hani Abu Bakar Wan Ramli Wan Daud Nazlina Haiza Mohd Yasin Mahendra Rao Somalu Byung Hong Kim 《国际能源研究杂志》2020,44(9):7464-7476
The low cost, low over-potential loss, good catalytic properties for hydrogen evolution reaction (HER), high corrosion stability, commercially available, and could be applied in pH-neutral solution and ambient temperature are important properties for the cathode materials when it is applied in microbial electrolysis cell (MEC) technology. This study has two-pronged objectives: the first is to investigate the feasibility of titanium (Ti) and graphite felt (GF) coated with nickel (Ni), and the second is to generate hydrogen from the fermentation effluent (FE). The electrodeposition (ED) method was used to deposit Ni catalyst onto Ti (Ni/Ti) and GF (Ni/GF) surfaces. The scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy were used to characterize the cathode morphology and element composition. The catalytic properties of Ni/Ti and Ni/GF could be evaluated using the linear sweep voltammetry tests. The maximum volumetric H2 production rates of MEC using Ni/Ti and Ni/GF cathodes were obtained at 0.39 ± 0.01 and 0.33 ± 0.03 m3 H2 m−3 d−1 respectively. The Ni/Ti and Ni/GF cathodes could be used as alternative cathodes while producing hydrogen from FE. 相似文献
27.
木里煤田是青海省重要的煤产地,其中聚乎更、哆嗦公马、雪霍立、外力哈达、热水等地含煤地层出露较好、煤系埋深较浅。受祁连山构造带以及阿尔金断裂走滑作用的控制,木里煤田构造类型多样。根据木里煤田的地质背景,从沉积聚煤规律、构造特征及其控煤作用等方面对木里煤田隐伏区及逆冲推覆构造下含煤地层进行分析,指出应在已知矿区外围逆冲推覆断层下盘找煤,同时被新生代覆盖的隐伏区为今后找煤的方向。 相似文献
28.
ABSTRACT Governing the rate of heat transport by condenser tubes in the passive containment cooling system (PCCS), the steam condensation over a vertical cylinder in the presence of air was investigated experimentally. The main objective of this study was to explore if the condensation heat transfer coefficient relies on the tube dimension, which has been a variable missed in most condensation models or has been embraced without experimental demonstration under phase change environments. The mean heat transfer coefficient was measured in the condensation test facility named JERICHO (JNU Experimental Rig for Investigation of Condensation Heat transfer On tube). The outer diameter of the condenser tube used in this study was set to 21.5 mm. The measured heat transfer coefficients were compared to those obtained from the 40-mm-O.D. tube, and a multiplier to correct the variation of the heat transfer coefficient with the tube diameter was proposed for its application to Lee correlation. The proposed correlation was further validated against another set of experimental data obtained from a separate test facility housing the 31.8-mm-O.D. tube. 相似文献
29.
30.