全文获取类型
收费全文 | 2763篇 |
免费 | 46篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 42篇 |
综合类 | 3篇 |
化学工业 | 552篇 |
金属工艺 | 162篇 |
机械仪表 | 70篇 |
建筑科学 | 148篇 |
矿业工程 | 10篇 |
能源动力 | 98篇 |
轻工业 | 225篇 |
水利工程 | 26篇 |
石油天然气 | 62篇 |
武器工业 | 1篇 |
无线电 | 205篇 |
一般工业技术 | 687篇 |
冶金工业 | 200篇 |
原子能技术 | 80篇 |
自动化技术 | 250篇 |
出版年
2021年 | 30篇 |
2020年 | 21篇 |
2019年 | 23篇 |
2018年 | 66篇 |
2017年 | 53篇 |
2016年 | 55篇 |
2015年 | 41篇 |
2014年 | 45篇 |
2013年 | 105篇 |
2012年 | 102篇 |
2011年 | 158篇 |
2010年 | 130篇 |
2009年 | 130篇 |
2008年 | 93篇 |
2007年 | 111篇 |
2006年 | 113篇 |
2005年 | 63篇 |
2004年 | 64篇 |
2003年 | 84篇 |
2002年 | 79篇 |
2001年 | 90篇 |
2000年 | 60篇 |
1999年 | 49篇 |
1998年 | 90篇 |
1997年 | 88篇 |
1996年 | 58篇 |
1995年 | 48篇 |
1994年 | 50篇 |
1993年 | 54篇 |
1992年 | 38篇 |
1991年 | 41篇 |
1990年 | 30篇 |
1989年 | 35篇 |
1988年 | 34篇 |
1987年 | 38篇 |
1986年 | 44篇 |
1985年 | 31篇 |
1984年 | 35篇 |
1983年 | 14篇 |
1982年 | 18篇 |
1981年 | 26篇 |
1980年 | 15篇 |
1979年 | 21篇 |
1978年 | 14篇 |
1977年 | 21篇 |
1976年 | 31篇 |
1975年 | 14篇 |
1974年 | 18篇 |
1973年 | 16篇 |
1971年 | 13篇 |
排序方式: 共有2821条查询结果,搜索用时 15 毫秒
51.
Ch. R. V. S. Nagesh Ch. Sridhar Rao N. B. Ballal P. Krishna Rao 《Metallurgical and Materials Transactions B》2004,35(1):65-74
The Kroll process of magnesium reduction of titanium tetrachloride is used the world over the production of titanium metal
in the form of sponge. Although the process has been in practice for the last five decades, there is no clear understanding
of the reaction mechanism and sponge formation. The present study involved reduction experiments in a 2000 kg titanium sponge-capacity
prototype reactor to develop a better understanding of TiCl4 reduction of magnesium with respect to the process parameters. Experiments were also conducted in two smaller experimental
reactors to study the temperature evolution during the process as a function of the TiCl4 feed rate. Based on the results of all these experiments, a model has been proposed for the mechanism of sponge formation
in the Kroll process. 相似文献
52.
Ordered binary decision diagrams (OBDDs) are a very popular graph representation for Boolean functions. They can be viewed as finite automata recognizing sets of strings of a fixed length, where the letters of the input strings are read at most once in a predefined ordering. The string matching problem with string w as pattern, consists of determining, given an input string, whether or not it contains w as substring. We show that for a fraction of orderings tending to 1 when n increases arbitrarily, the minimal size of an OBDD solving the string matching problem for strings of length n has a growth which is an exponential in n. 相似文献
53.
J. Michutta A. Yawny M. C. Carroll Ch. Somsen G. Eggeler 《Materialwissenschaft und Werkstofftechnik》2004,35(5):289-293
The present paper considers the phase transition behavior of a single crystal Ni‐rich NiTi alloy which was compression aged to produce one single family of Ni4Ti3 precipitates. The single crystal material was produced in a two stage process. Polycrystalline material was first melted under an inert atmosphere and remelted when single crystals were produced. Compression aging treatments in <111>‐orientation were carried out in order to suppress all but one family of Ni4Ti3‐precipitates which nucleate and grow on {111}‐planes of the B2 matrix. The objective of this study is to investigate the influence of Ni4Ti3‐precipitates on the martensitic transformation behavior. It was previously shown that grain boundaries provide heterogeneous nucleation sites for the formation of Ni4Ti3; this results in heterogeneous microstructures which undergo multiple step martensitic transformations. Single crystals avoid grain boundaries and the present study aims at clarifying how homogeneously precipitated particles affect martensitic transformations. 相似文献
54.
Cuny Caroline; Chéry-Croze Sylviane; Bougeant Jean-Claude; Koenig Olivier 《Canadian Metallurgical Quarterly》2004,18(2):384
The authors tested functional hemispheric asymmetry through word dichotic listening and lateralized lexical decision tasks in tinnitus patients and controls stimulated by a continuous tinnitus-like noise to test the influence of a tinnitus-like external stimulation. A classic right-ear advantage was shown in the auditory task for all but right-ear tinnitus patients, who performed as equally badly when the stimuli were presented to the right and left ears. Concerning the visual task, all participants demonstrated the expected right visual field advantage for word stimuli. Moreover, those who submitted to external stimulation demonstrated normal asymmetric patterns. These data suggest a specific effect of tinnitus on central processing and provide evidence for a functional reorganization induced by this auditory phantom perception. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
55.
A practical implementation of stochastic programming: an application to the evaluation of option contracts in supply chains 总被引:1,自引:0,他引:1
Ch. van Delft Author Vitae 《Automatica》2004,40(5):743-756
Stochastic programming is a powerful analytical method in order to solve sequential decision-making problems under uncertainty. We describe an approach to build such stochastic linear programming models. We show that algebraic modeling languages make it possible for non-specialist users to formulate complex problems and have solved them by powerful commercial solvers. We illustrate our point in the case of option contracts in supply chain management and propose a numerical analysis of performance. We propose easy-to-implement discretization procedures of the stochastic process in order to limit the size of the event tree in a multi-period environment. 相似文献
56.
A dedicated cryopreparation system, the SCU 020 (Balzers), is introduced and described in detail for use in low-temperature scanning electron microscopy (LTSEM). The basic unit consists of two parts: (i) a high-vacuum preparation chamber equipped with a cold-stage, motor-driven fracturing microtome, planar magnetron (PM) sputter source, quartz-crystal thin-film monitor, Meissner cold trap, and turbo molecular pump stand; and (ii) a second part (separated from the first by a sliding, high-vacuum valve) residing in the SEM chamber. This is equipped with an anti-contamination cold trap, a fully movable goniometer cold stage (having motor drives for x, y, and rotation) and replaces the SEM's original stage (Raith). The SCU 020 is entirely self contained allowing independence from, and synchroneity with, the SEM of choice. LTSEM micrographs of specimen (that are fully frozen hydrated or partially freeze-dried) surfaces or fracture faces, without or with various metal coatings, can be examined over a broad temperature range (-150 to +50°C). This is made possible by the combined application of the two, independently controlled, cold stages and the on-line, high-vacuum, specimen cryo transfer between them. In-situ etching is simple and straightforward. Intramembranous particles and membrane fracture steps, typically imaged in transmission electron microscopy (TEM), are resolved by PM sputtering with platinum at low specimen temperature and high-resolution LTSEM in a field emission microscope. 相似文献
57.
Ch.?Venkata ReddyEmail author S.?V.?Prabhakar Vattikuti Jaesool?ShimEmail author 《Journal of Materials Science: Materials in Electronics》2016,27(8):7799-7808
CdS nanoparticles (NPs) were synthesized using co-precipitation method. X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to confirm the structures and morphologies of CdS NPs. X-ray diffraction data confirmed the crystal structure of the CdS NPs. Raman spectrum exhibited the Raman modes of LO and 2LO of CdS at 290 and 595 cm?1 respectively. The evaluated band gap was 3.15 eV, this value was shifted compared with the bulk value and this could be a significance of a size quantization effect in the sample. The CdS nanoparticles showed higher photocatalytic activity for the discoloration of methyl orange (MO) under UV light irradiation for 90 min. The highest photocatalytic activity was obtained with the sample containing 0.3 wt % CdS nanoparticles, in which more than 98 % of the MO was discolored within 90 min. 相似文献
58.
59.
60.