全文获取类型
收费全文 | 88120篇 |
免费 | 6606篇 |
国内免费 | 3918篇 |
专业分类
电工技术 | 5786篇 |
技术理论 | 5篇 |
综合类 | 7079篇 |
化学工业 | 4600篇 |
金属工艺 | 18605篇 |
机械仪表 | 4315篇 |
建筑科学 | 19973篇 |
矿业工程 | 1721篇 |
能源动力 | 4351篇 |
轻工业 | 1580篇 |
水利工程 | 1045篇 |
石油天然气 | 2365篇 |
武器工业 | 458篇 |
无线电 | 1351篇 |
一般工业技术 | 7754篇 |
冶金工业 | 15111篇 |
原子能技术 | 429篇 |
自动化技术 | 2116篇 |
出版年
2024年 | 192篇 |
2023年 | 764篇 |
2022年 | 1909篇 |
2021年 | 2146篇 |
2020年 | 2372篇 |
2019年 | 1758篇 |
2018年 | 1521篇 |
2017年 | 2411篇 |
2016年 | 2509篇 |
2015年 | 2923篇 |
2014年 | 5557篇 |
2013年 | 4620篇 |
2012年 | 6409篇 |
2011年 | 7449篇 |
2010年 | 5638篇 |
2009年 | 5828篇 |
2008年 | 4676篇 |
2007年 | 6178篇 |
2006年 | 5521篇 |
2005年 | 4710篇 |
2004年 | 3935篇 |
2003年 | 3487篇 |
2002年 | 2917篇 |
2001年 | 2571篇 |
2000年 | 2175篇 |
1999年 | 1726篇 |
1998年 | 1246篇 |
1997年 | 1210篇 |
1996年 | 984篇 |
1995年 | 719篇 |
1994年 | 645篇 |
1993年 | 439篇 |
1992年 | 380篇 |
1991年 | 269篇 |
1990年 | 220篇 |
1989年 | 189篇 |
1988年 | 145篇 |
1987年 | 67篇 |
1986年 | 42篇 |
1985年 | 28篇 |
1984年 | 22篇 |
1983年 | 23篇 |
1982年 | 24篇 |
1981年 | 17篇 |
1980年 | 47篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1975年 | 4篇 |
1959年 | 10篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
We present a technique for approximating isotropic BRDFs and precomputed self-occlusion that enables accurate and efficient prefiltered environment map rendering. Our approach uses a nonlinear approximation of the BRDF as a weighted sum of isotropic Gaussian functions. Our representation requires a minimal amount of storage, can accurately represent BRDFs of arbitrary sharpness, and is above all, efficient to render. We precompute visibility due to self-occlusion and store a low-frequency approximation suitable for glossy reflections. We demonstrate our method by fitting our representation to measured BRDF data, yielding high visual quality at real-time frame rates. 相似文献
33.
The evolution of surface defects during shape rolling of high‐speed steel billets is studied using longitudinal surface defects prepared by machining and welding. The reduction of the defects during rolling in a production mill is compared to the total area reduction of the billets. Samples are collected after pass 4, 6, 8, 14, 19 and the final pass, 28, representing the finished 5.5mm wire. By inspecting the cross sections, the rotation of the billets from pass to pass is evaluated. Results from FE simulations on solid billets are compared to the experimental results. Generally, simulations predict less reduction than observed experimentally. In most cases cracks reduce most effectively followed by carbon steel welds and stainless steel welds. 相似文献
34.
简单分析了高炉煤气中Cl元素的存在对不锈钢膨胀节的应力腐蚀问题和防止途径,作为一种临时性的防范措施,简要介绍了煤气膨胀节包焊实施步骤和措施。 相似文献
35.
介绍了城市轨道交通直流牵引供电系统的构成,详细叙述了直流牵引供电系统的主要电气设备及其连接方法,以及系统的运行方式.另外,还简单介绍了系统配置的直流保护以及保护原理和保护作用. 相似文献
36.
37.
本文介绍涟钢第一炼钢厂1号小方坯连铸机浇铸优质钢的生产实践,并探索连铸优质钢的途径。指出为保证质量,必须严格保证钢水质量,控制合适的浇铸温度,拉坯速度和冷却强度;钢水必须吹氩;采用大容量中间包和伸入式水口保护渣浇涛,确保连铸机的状况良好。 相似文献
38.
The feasibility of a new alloy design concept utilizing the principle of ‘tungsten bronze effect’ is critically evaluated for the development of metallic bipolar plates for proton exchange membrane fuel cell (PEMFC). An austenitic stainless steel (ASS) is modified with W and La to improve the stability of the passive film in an acidic environment as well as to reduce the contact resistance by the tungsten bronze effect. The experimental ASS containing W and La was evaluated in a simulated PEMFC environment of H3PO4 and H2SO4 solutions at 80 °C, and the electrical property was evaluated by performing a contact resistance test. The test results show that the ASS modified with W and La has good passive film stability for corrosion resistance and low contact resistance. The X-ray photoelectron spectroscopy (XPS) analysis clearly suggests the possibility of the tungsten bronze effect from the change in valency state of W6+ to W5+ in the passive film formed on the modified ASS. The feasibility of a new alloy design concept utilizing the ‘tungsten bronze effect’ is well demonstrated; however, more study is highly required for the development of metallic bipolar plates of PEMFC. 相似文献
39.
研究了添加高速钢粉对烧结钢组织与性能的影响。实验结果表明,含20%高速钢的烧结钢综合力学性能最好;添加高速钢粉能导致烧结钢密度减小的冲击韧性降低,当高速钢含量增中时,硬度随之增加,烧结钢中残余奥氏体和马氏体的含量与高速钢的含量呈线性关系。烧结钢中的马氏体显微硬度很高,它主要原高速钢粒子和原铁粒子的连接区域形成。 相似文献
40.
W. Fischer 《Progress in Organic Coatings》1993,22(1-4):181-193
Corrosion protection of organic coated steel is determined by free corrosion potential measurements and impedance spectroscopy. The results are classified by means of very basic considerations and evaluation figures are developed. These electrochemical data are correlated with the extent of the corrosion for each coating system. The evaluation figures are used for ranking coating systems and this ranking is correlated with the ranking with reference to the results of standardized and exposure tests. 相似文献