全文获取类型
收费全文 | 4612篇 |
免费 | 152篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 84篇 |
综合类 | 16篇 |
化学工业 | 969篇 |
金属工艺 | 159篇 |
机械仪表 | 109篇 |
建筑科学 | 227篇 |
矿业工程 | 6篇 |
能源动力 | 82篇 |
轻工业 | 369篇 |
水利工程 | 15篇 |
石油天然气 | 7篇 |
无线电 | 423篇 |
一般工业技术 | 741篇 |
冶金工业 | 953篇 |
原子能技术 | 77篇 |
自动化技术 | 530篇 |
出版年
2023年 | 41篇 |
2022年 | 49篇 |
2021年 | 74篇 |
2020年 | 48篇 |
2019年 | 67篇 |
2018年 | 84篇 |
2017年 | 64篇 |
2016年 | 93篇 |
2015年 | 84篇 |
2014年 | 110篇 |
2013年 | 185篇 |
2012年 | 160篇 |
2011年 | 200篇 |
2010年 | 162篇 |
2009年 | 147篇 |
2008年 | 152篇 |
2007年 | 159篇 |
2006年 | 166篇 |
2005年 | 121篇 |
2004年 | 123篇 |
2003年 | 105篇 |
2002年 | 112篇 |
2001年 | 76篇 |
2000年 | 112篇 |
1999年 | 118篇 |
1998年 | 249篇 |
1997年 | 182篇 |
1996年 | 154篇 |
1995年 | 103篇 |
1994年 | 87篇 |
1993年 | 88篇 |
1992年 | 52篇 |
1991年 | 54篇 |
1990年 | 42篇 |
1989年 | 54篇 |
1988年 | 46篇 |
1987年 | 52篇 |
1986年 | 34篇 |
1985年 | 36篇 |
1984年 | 39篇 |
1983年 | 41篇 |
1982年 | 32篇 |
1981年 | 30篇 |
1980年 | 40篇 |
1979年 | 35篇 |
1978年 | 38篇 |
1977年 | 63篇 |
1976年 | 88篇 |
1975年 | 30篇 |
1974年 | 38篇 |
排序方式: 共有4767条查询结果,搜索用时 15 毫秒
1.
Ohne Zusammenfassung 相似文献
2.
Claudia Popien Axel Kuepper Bernd Meyer 《Journal of Network and Systems Management》1994,2(4):383-400
New requirements of growing computer networks and information systems have an influence on extended client/server models with increased functionality. This forms the basis for service management in distributed systems which is realized by a service trading concept. This paper studies the requirements derived from the Open Distributed Processing (ODP) Reference Model in order to consider an open service market. Furthermore, it examines management possibilities for describing the service trading scenario. Because of similar architectures and properties ODP services, service offers, types, exporters and traders are mapped onto management components and modeled as managed objects. Therefore, the Guidelines for the Definition of Managed Objects (GDMO) are used. The final concept allows a precise and unambiguous study of the service trading scenario and provides means for exporting and importing of service offers in a distributed environment. 相似文献
3.
4.
5.
J Abart K Eberhardt H Fischer W Huk E Richter F Schmitt T Storch B Tomandl E Zeitler 《Canadian Metallurgical Quarterly》1997,21(4):532-538
PURPOSE: A study was performed to assess the stimulation threshold for healthy adults using sinusoidally oscillating gradients. METHOD: One hundred thirteen healthy adults were examined in the study. ECG and physiological parameters were measured. All measurements were performed of both the head and the abdomen. The subjects were measured in the supine position with the region of interest positioned in the center of the gradient coils. The measurement was performed for three orthogonal, four oblique, and double oblique orientations. RESULTS: No volunteer reported painful, severe stimulation. The mean thresholds for peripheral stimulation in head and body measurement were similar: 85.5% of stimulation during examination of the head and 87.6% during measurements of the abdomen were reported when the y-gradient was used. CONCLUSION: The greatest frequency of reported stimulations occurs when the y-gradient is used. This was confirmed by the results and supports the hypothesis that orthogonal to the y-axis the body has its largest conductive loop, resulting in the strongest peripheral stimulation. 相似文献
6.
45 patients with occlusive peripheral vascular disease were examined by MR angiography in a retrospective study. A FISP 3D sequence was used by acquiring a rephased and a dephased data set. The individual slices were post-processed by using a maximum-intensity-projection algorithm. The MRA results of the popliteal and tibioperoneal arteries were compared to conventional or digital angiography. In comparing these techniques MR angiography cannot be accepted for pre- and postoperative staging of patients with occlusive peripheral vascular disease. In future new MRA techniques may be useful in postoperative staging of patients with peripheral vascular stenosis. 相似文献
7.
8.
For an assessment of the risk potential of existing structures, where in the case of prestressing steel damage the load-bearing capacity could be significantly affected, non-destructive testing techniques which enable reliable evaluation of the condition of the prestressing steels are of utmost importance. During the demolition of a post-tensioned concrete bridge in Berlin where damage of prestressing wires due to hydrogen-induced stress corrosion cracking were found in former investigations, parts of the girders of the bridge superstructure could be taken out. After non-destructive investigations by means of two testing techniques based on magnetic leakage flux measurement and one technique based on electromagnetic resonance measurement, subsequent removal of the concrete cover up to the ducts, opening the ducts and evaluation of the prestressing steels allowed a verification of the results obtained by the NDT methods. From the results it can be concluded that areas with fractures of several wires can be detected by the two techniques based on magnetic leakage flux measurement. 相似文献
9.
In this paper, we summarize our recent efforts to analyze transmission probabilities of extremely thin SiO2 gate oxides using microscopic models of Si[100]-SiO2-Si[100] heterojunctions. We predict energy-dependent tunneling masses and their influence on transmission coefficients, discuss tunneling probabilities and analyze effects arising from the violation of parallel momentum conservation. As an application of the present method, gate currents in short bulk MOSFETs are calculated, including elastic defect-assisted contributions. 相似文献
10.