全文获取类型
收费全文 | 2673篇 |
免费 | 162篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 49篇 |
综合类 | 6篇 |
化学工业 | 700篇 |
金属工艺 | 72篇 |
机械仪表 | 74篇 |
建筑科学 | 152篇 |
矿业工程 | 2篇 |
能源动力 | 54篇 |
轻工业 | 286篇 |
水利工程 | 6篇 |
石油天然气 | 2篇 |
无线电 | 215篇 |
一般工业技术 | 552篇 |
冶金工业 | 202篇 |
原子能技术 | 14篇 |
自动化技术 | 451篇 |
出版年
2023年 | 15篇 |
2022年 | 29篇 |
2021年 | 51篇 |
2020年 | 40篇 |
2019年 | 54篇 |
2018年 | 54篇 |
2017年 | 70篇 |
2016年 | 74篇 |
2015年 | 80篇 |
2014年 | 94篇 |
2013年 | 146篇 |
2012年 | 120篇 |
2011年 | 177篇 |
2010年 | 127篇 |
2009年 | 121篇 |
2008年 | 138篇 |
2007年 | 124篇 |
2006年 | 115篇 |
2005年 | 91篇 |
2004年 | 72篇 |
2003年 | 76篇 |
2002年 | 52篇 |
2001年 | 49篇 |
2000年 | 50篇 |
1999年 | 48篇 |
1998年 | 62篇 |
1997年 | 50篇 |
1996年 | 49篇 |
1995年 | 36篇 |
1994年 | 23篇 |
1993年 | 33篇 |
1992年 | 29篇 |
1991年 | 30篇 |
1990年 | 28篇 |
1989年 | 26篇 |
1988年 | 24篇 |
1987年 | 20篇 |
1986年 | 27篇 |
1985年 | 22篇 |
1984年 | 23篇 |
1983年 | 19篇 |
1982年 | 22篇 |
1981年 | 21篇 |
1980年 | 22篇 |
1979年 | 26篇 |
1978年 | 26篇 |
1977年 | 21篇 |
1976年 | 20篇 |
1974年 | 21篇 |
1973年 | 14篇 |
排序方式: 共有2837条查询结果,搜索用时 15 毫秒
21.
Cure of Helicobacter pylori infection: role of duration of treatment with omeprazole and amoxicillin
A case of ankylosing spondylitis with pronounced osteolysis of the 12th thoracic vertebral body as part of posttraumatic pseudoarthrosis is described. The appearance of posttraumatic osteolysis simulates a malignant lesion, and it is important to consider the diagnosis in cases of osteolytic lesions of unknown origin. 相似文献
22.
An Extended Replication of an Experiment for Assessing Methods for Software Requirements Inspections 总被引:1,自引:1,他引:0
Kristian Sandahl Ola Blomkvist Joachim Karlsson Christian Krysander Mikael Lindvall Niclas Ohlsson 《Empirical Software Engineering》1998,3(4):327-354
We have performed an extended replication of the Porter-Votta-Basili experiment comparing the Scenario method and the Checklist method for inspecting requirements specifications using identical instruments. The experiment has been conducted in our educational context represented by a more general definition of a defect compared to the original defect list. Our study involving 24 undergraduate students manipulated three independent variables: detection method, requirements specification, and the order of the inspections. The dependent variable measured is the defect detection rate. We found the requirements specification inspected and not the detection method to be the most probable explanation for the variance in defect detection rate. This suggests that it is important to gather knowledge of how a requirements specification can convey an understandable view of the product and to adapt inspection methods accordingly. Contrary to the original experiment, we can not significantly support the superiority of the Scenario method. This is in accordance with a replication conducted by Fusaro, Lanubile and Visaggio, and might be explained by the lack of individual defect detection skill of our less experienced subjects. 相似文献
23.
Jantsch Simon Müller David Baier Christel Klein Joachim 《Formal Methods in System Design》2021,58(1-2):42-82
Formal Methods in System Design - Due to the high complexity of translating linear temporal logic (LTL) to deterministic automata, several forms of “restricted” nondeterminism have been... 相似文献
24.
25.
Glass melts of the metallic alloy system Pd10–70Ni10–70P14–26 were saturated with helium gas during the melt-spinning process. Some melts with platinum substituted for palladium; manganese, iron or cobalt for nickel; and boron for phosphorus could also be saturated. The helium could be extracted from the glasses and the amount of gas was quantitatively measured with a mass spectrometer. The helium solubilities, obtained between 750 and 1250° C, varied between about 2 and 45 (l He per mol glass) (T/273). These solubilities turned out to be strongly composition-dependent. This fact is discussed in terms of different short-range order structure units which are directly related to the free volume available for the gas solution process. 相似文献
26.
27.
Joachim Meissner 《Polymer Engineering and Science》1987,27(8):537-546
For film blowing of polyethylene it has been shown previously that melt elongation is very powerful for polymer characterization. With two types of rheometers, simple (also called “uniaxial”) elongational tests as well as creep tests can be performed homogeneously. In simple elongation, the melts of branched polyethylene show a remarkable strain hardening. With respect to their advantages and disadvantages, these rheometers complement each other. For multiaxial elongations the various modes of deformation can be performed by means of the rotary clamp technique. With the strain rate components ordered such that \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}11 ? \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}22 ≥ \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}33, the ratio m = \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}22/\documentclass{article}\pagestyle{empty}\begin{document}$ \dot \varepsilon $\end{document}11 characterizes the test mode. The Stephenson definition of the elongational viscosities makes use of the linear viscoelastic material equation and proves to be very efficient because the linear shear viscosity (t) (“stressing” viscosity) can act as the reference for the nonlinear behavior in elongation. Results are given for polyisobutylene measured not only in simple, equibiaxial, and planar elongations, but also in new test modes with a change of m during the deformation. This allows one to investigate the consequences of a deformation-induced anisotropy of the rheological behavior. 相似文献
28.
综述了聚乙烯、聚丙烯单组分复合材料的发展概况及最新研究动态。介绍了熔融膜压法、粉末浸渍法、溶液浸渍法三类制备聚乙烯单组分复合材料的传统方法。重点介绍了热压法、共挤出热压法两类制备单组分复合材料的创新方法。分析了各制备方法的优缺点:熔融法、粉末法与溶液法效率均较低且复合材料中纤维含量较少,力学性能不佳;热压法由于初始材料为100%纤维,从而综合效率较高,力学性能良好,缺点为加工温度过于苛刻;共挤出热压法效率较高,在具有高的增强相含量的同时拥有较宽的加工温度范围,缺点为增强相强度需进一步提高。最后介绍了单组分复合材料的应用并对其研究与应用前景作了展望。 相似文献
29.
We investigate a metric facility location problem in a distributed setting. In this problem, we assume that each point is a client as well as a potential location for a facility and that the opening costs for the facilities and the demands of the clients are uniform. The goal is to open a subset of the input points as facilities such that the accumulated cost for the whole point set, consisting of the opening costs for the facilities and the connection costs for the clients, is minimized. We present a randomized distributed algorithm that computes in expectation an ${\mathcal {O}}(1)$ -approximate solution to the metric facility location problem described above. Our algorithm works in a synchronous message passing model, where each point is an autonomous computational entity that has its own local memory and that communicates with the other entities by message passing. We assume that each entity knows the distance to all the other entities, but does not know any of the other pairwise distances. Our algorithm uses three rounds of all-to-all communication with message sizes bounded to $\mathcal{O}(\log(n))$ bits, where n is the number of input points. We extend our distributed algorithm to constant powers of metric spaces. For a metric exponent ?≥1, we obtain a randomized ${\mathcal {O}}(1)$ -approximation algorithm that uses three rounds of all-to-all communication with message sizes bounded to $\mathcal{O}(\log(n))$ bits. 相似文献
30.
Leonard Stoloff John Dantzman John Wegener 《Journal of the American Oil Chemists' Society》1972,49(4):264-266
A procedure has been devised for preparing lot samples of mycotoxin-contaminated nut meats so that a representative analytical
sample may be removed. The sample is rapidly reduced to coarse size. A relatively large portion (about 1/10 of total sample)
of subsample is then split out and further comminuted to a fine particle size with the aid of a fat solvent (meat-solvent,
w/v, 3:2). The analytical sample is removed from this mixture. The procedure was tested with shelled almonds and shelled walnuts
using radioactive nuts to simulate the mycotoxin contamination and provide a simple, precise measure of the contaminated nut
meat distribution. The pooled coefficient of variation was 18% for the subsamples and 4.4% for the analytical samples. Considering
the dilution factors used (1.50 and 2.14 contaminated nuts/104 nuts) and the low degree of reliability of the lot sample, the sample preparation methods tested appear to be practical and
reliable. 相似文献