全文获取类型
收费全文 | 102763篇 |
免费 | 10272篇 |
国内免费 | 5725篇 |
专业分类
电工技术 | 9437篇 |
技术理论 | 4篇 |
综合类 | 7824篇 |
化学工业 | 15573篇 |
金属工艺 | 9914篇 |
机械仪表 | 5499篇 |
建筑科学 | 8161篇 |
矿业工程 | 2940篇 |
能源动力 | 5491篇 |
轻工业 | 8289篇 |
水利工程 | 2210篇 |
石油天然气 | 7282篇 |
武器工业 | 888篇 |
无线电 | 9998篇 |
一般工业技术 | 10840篇 |
冶金工业 | 7427篇 |
原子能技术 | 1736篇 |
自动化技术 | 5247篇 |
出版年
2024年 | 496篇 |
2023年 | 1469篇 |
2022年 | 2788篇 |
2021年 | 3266篇 |
2020年 | 3520篇 |
2019年 | 2909篇 |
2018年 | 2798篇 |
2017年 | 3515篇 |
2016年 | 3847篇 |
2015年 | 4013篇 |
2014年 | 6293篇 |
2013年 | 6366篇 |
2012年 | 7799篇 |
2011年 | 8311篇 |
2010年 | 5775篇 |
2009年 | 5754篇 |
2008年 | 5141篇 |
2007年 | 6721篇 |
2006年 | 6188篇 |
2005年 | 5124篇 |
2004年 | 4445篇 |
2003年 | 3968篇 |
2002年 | 3203篇 |
2001年 | 2919篇 |
2000年 | 2357篇 |
1999年 | 1867篇 |
1998年 | 1395篇 |
1997年 | 1246篇 |
1996年 | 1058篇 |
1995年 | 822篇 |
1994年 | 708篇 |
1993年 | 520篇 |
1992年 | 458篇 |
1991年 | 394篇 |
1990年 | 308篇 |
1989年 | 218篇 |
1988年 | 160篇 |
1987年 | 107篇 |
1986年 | 97篇 |
1985年 | 88篇 |
1984年 | 81篇 |
1983年 | 59篇 |
1982年 | 39篇 |
1981年 | 23篇 |
1980年 | 38篇 |
1979年 | 18篇 |
1977年 | 10篇 |
1975年 | 6篇 |
1959年 | 18篇 |
1951年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
191.
The wettability of the lithium surface by liquid alkali metals Na, K and Rb is investigated for the first time by the sessile drop method in an all-soldered instrument under conditions of a high vacuum. The presence of the temperature threshold of wetting is found in Li–Na and Li–K systems at temperatures of 325°C and 160°C, respectively. A conclusion is drawn that an abrupt decrease in wetting angles in the investigated systems is associated with a marked decrease in the interfacial tension at lithium-lithium, lithium-potassium, and lithium--rubidium interfaces owing to the beginning of a noticeable mutual solubility of the components at relatively high temperatures. 相似文献
192.
193.
Ferdinando Auricchio Lorenza Petrini 《International journal for numerical methods in engineering》2004,61(6):807-836
An always increasing knowledge on material properties as well as a progressively more sophisticated production technology make shape memory alloys (SMA) extremely interesting for the industrial world. At the same time, SMA devices are typically characterized by complex multi‐axial stress states as well as non‐homogeneous and non‐isothermal conditions both in space and time. This aspect suggests the finite element method as a useful tool to help and improve application design and realization. With this aim, we focus on a three‐dimensional macroscopic thermo‐mechanical model able to reproduce the most significant SMA features (Int. J. Numer. Methods Eng. 2002; 55 : 1255–1264), proposing a simple modification of such a model. However, the suggested modification allows the development of a time‐discrete solution algorithm, which is more effective and robust than the one previously discussed in the literature. We verify the computational tool ability to simulate realistic mechanical boundary value problems with prescribed temperature dependence, studying three SMA applications: a spring actuator, a self‐expanding stent, a coupling device for vacuum tightness. The effectiveness of the model to solve thermo‐mechanical coupled problems will be discussed in a forthcoming work. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
194.
Yun‐Hwei Shen 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(5):581-586
A novel strategy of sweep coagulation to treat low turbidity water is presented herein. Study findings demonstrated that an Na+‐saturated bentonite with medium cation exchange capacity (CEC) resulted in significant turbidity removal at a bentonite dosage of 30 mg dm?3. Bentonite dispersion with fully delaminated platelets tended to undergo a more porous type of coagulation with intense face‐to‐face interactions of platelets and effectively entrapped TiO2 particles in band‐type structures. This type of coagulation usually results in a large volume of settled flocs with a fluffy structure and excellent turbidity removal efficiency for sweep coagulation. The sign and magnitude of electrical charge on TiO2 particles has a minor effect on the efficiency of sweep coagulation. Copyright © 2005 Society of Chemical Industry 相似文献
195.
196.
朝阳沟裂缝性低渗透油田井网适应性研究 总被引:23,自引:13,他引:10
通过对比分析朝阳沟裂缝性低渗透油藏与裂缝主方向分别成11.5°和22.5°的两种不同井网的开发效果,表明与裂缝成11.5°的井网与裂缝匹配性较差,开发效果相对较差。并从油藏的水驱控制程度、压力传导情况、采收率及经济效益等方面研究评价了朝1.55区井网的适应性,为指导油田的加密调整,在技术和经济两方面综合评价确定了合理的井距和井网密度,并针对朝1-55区的地质特征,提出了井网和注水方式调整办法,在朝55区块实施后,取得了较好的现场试验效果。 相似文献
197.
198.
ISIS全局优化多道反演技术在墩2块岩性油藏描述中的应用 总被引:2,自引:0,他引:2
为进一步落实墩2块戴一段岩性油藏成藏规模及分布规律,针对该储层薄、横向变化快的特点,利用ISIS全局优化多道反演技术,对该构造区岩性储层进行了精细描述,较好的预测出戴一段储层平面分布规律。 相似文献
199.
200.
LIUZhi-qiang MAWei ZHOUGuo-qing NIUFu-jun WANGJian-zhou CHANGLi-wu ZHOUJin-sheng 《中国矿业大学学报(英文版)》2005,15(1):21-25
The main factors that influence the temperature field of frozen subgrade were analyzed.The experimental equipment for simulating frozen subgrade was built up,and the declining regulating tubes were placed at the foot of the embankment. By means of this equipment two simulating experiments of controlling temperature filed of frozen subgrade were carried out in the laboratory. One method is to collect natural cold energy, and the other one is to collect natural cold energy ccompanied by artificial refrigeration simultaneously. The result indicates that the latter is an effective method for maintaining the stability of the frozen subgrade. 相似文献