全文获取类型
收费全文 | 5639篇 |
免费 | 277篇 |
国内免费 | 31篇 |
专业分类
电工技术 | 49篇 |
综合类 | 33篇 |
化学工业 | 1079篇 |
金属工艺 | 100篇 |
机械仪表 | 128篇 |
建筑科学 | 239篇 |
矿业工程 | 35篇 |
能源动力 | 95篇 |
轻工业 | 578篇 |
水利工程 | 39篇 |
石油天然气 | 5篇 |
武器工业 | 1篇 |
无线电 | 360篇 |
一般工业技术 | 935篇 |
冶金工业 | 1554篇 |
原子能技术 | 27篇 |
自动化技术 | 690篇 |
出版年
2023年 | 35篇 |
2022年 | 48篇 |
2021年 | 107篇 |
2020年 | 88篇 |
2019年 | 71篇 |
2018年 | 178篇 |
2017年 | 161篇 |
2016年 | 172篇 |
2015年 | 148篇 |
2014年 | 145篇 |
2013年 | 362篇 |
2012年 | 310篇 |
2011年 | 298篇 |
2010年 | 225篇 |
2009年 | 187篇 |
2008年 | 261篇 |
2007年 | 201篇 |
2006年 | 180篇 |
2005年 | 160篇 |
2004年 | 126篇 |
2003年 | 152篇 |
2002年 | 132篇 |
2001年 | 99篇 |
2000年 | 99篇 |
1999年 | 92篇 |
1998年 | 511篇 |
1997年 | 286篇 |
1996年 | 189篇 |
1995年 | 115篇 |
1994年 | 96篇 |
1993年 | 105篇 |
1992年 | 23篇 |
1991年 | 40篇 |
1990年 | 25篇 |
1989年 | 32篇 |
1988年 | 28篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 37篇 |
1984年 | 25篇 |
1983年 | 24篇 |
1982年 | 36篇 |
1981年 | 36篇 |
1980年 | 20篇 |
1979年 | 20篇 |
1978年 | 24篇 |
1977年 | 46篇 |
1976年 | 45篇 |
1975年 | 18篇 |
1973年 | 16篇 |
排序方式: 共有5947条查询结果,搜索用时 43 毫秒
61.
Yliès Falcone Jean-Claude Fernandez Laurent Mounier 《International Journal on Software Tools for Technology Transfer (STTT)》2012,14(3):349-382
The underlying property, its definition, and representation play a major role when monitoring a system. Having a suitable and convenient framework to express properties is thus a concern for runtime analysis. It is desirable to delineate in this framework the sets of properties for which runtime analysis approaches can be applied to. This paper presents a unified view of runtime verification and enforcement of properties in the Safety-Progress classification. First, we extend the Safety-Progress classification of properties in a runtime context. Second, we characterize the set of properties which can be verified (monitorable properties) and enforced (enforceable properties) at runtime. We propose in particular an alternative definition of ??property monitoring?? to the one classically used in this context. Finally, for the delineated sets of properties, we define specialized verification and enforcement monitors. 相似文献
62.
A new crystalline structure of poly 4-methylpentene-1 (P4MP1), modiification named modification V, is obtained from cyclopentane solutions and gels, for polymer volume fractions between 0.01 and 0.10. The effect of the thermal history imparted to the solution is analyzed. The relation between gelation, polymorphism and existence of helical conformations of P4MP1 in solution is discussed. Modification V is tentatively indexed on the basis of an hexagonal unit cell with dimensions a = 22.17 ± 0.14 Å and c = 6.69 ±0.02 Å. The crystal transforms into modification I at 130 ± 5°C, the heat of transition being + 15 ±2 J.g?1. 相似文献
63.
del del Valle M. A. Ugalde L. Díaz F. R. Bodini M. E. Bernède J. C. Chaillou A. 《Polymer Bulletin》2003,51(1):55-62
Summary The influence of electrolyte and monomer concentration on
properties and morphology of electrochemically obtained
polyselenophene films doped and undoped with hexafluorophosphate
and tetrafluoroborate anions was analyzed. The films were
deposited on SnO2-coated glass in a
classical three-electrode cell from the monomer and the
electrolyte in anhydrous acetonitrile.The electrochemical growth of polyselenophene thin films
was studied by X-ray photoelectron spectroscopy (XPS), electron
probe microanalysis (EPMA), and scanning electron microscopy
(SEM). The morphology study revealed different three-
dimensional (3D) and bidimensional (2D) growth, depending on
monomer and electrolyte concentration. 相似文献
64.
65.
Yves Denizot Laurence Michel Jacques Benveniste Alain Meybeck Yolène Thomas Louis Duberfret 《Lipids》1991,26(12):1093-1094
Paf is a phospholipid mediator present in human skin which induces inflammatory events such as neutrophil infiltration and
increased vascular permeability. Recent data suggest that cutaneous cells, such as fibroblasts and keratinocytes, produce
paf and that paf is released during allergic cutaneous reactions. It is tempting to speculate that paf may contribute to the
development of various skin disorders with acute and chronic skin inflammation. Paf antagonists may help in bringing answers
to this hypothesis and may offer new prospects for the treatment of cutaneous inflammatory diseases.
Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl
Ether Lipids, Tokyo, Japan, May 1989. 相似文献
66.
Data reconciliation consists in modifying noisy or unreliable data in order to make them consistent with a mathematical model (herein a material flow network). The conventional approach relies on least-squares minimization. Here, we use a fuzzy set-based approach, replacing Gaussian likelihood functions by fuzzy intervals, and a leximin criterion. We show that the setting of fuzzy sets provides a generalized approach to the choice of estimated values, that is more flexible and less dependent on oftentimes debatable probabilistic justifications. It potentially encompasses interval-based formulations and the least squares method, by choosing appropriate membership functions and aggregation operations. This paper also lays bare the fact that data reconciliation under the fuzzy set approach is viewed as an information fusion problem, as opposed to the statistical tradition which solves an estimation problem. 相似文献
67.
Stability of ruthenium catalysts supported on TiO2 or ZrO2 in catalytic wet air oxidation 总被引:1,自引:0,他引:1
The stability of ruthenium catalysts supported on TiO2 and ZrO2 were studied in the wet air oxidation of aqueous solution of succinic and p-hydroxybenzoic acids taken as model effluent and on real effluents from the paper-pulp industry. Catalyst recycling experiments were conducted in batch reactor and long-term stability tests were conducted in trickle-bed reactor. In all experiments, ruthenium and support materials were perfectly stable to leaching, sintering and fouling. Ruthenium catalysts experienced a weak deactivation as they were exposed to air, e.g., in recycling experiments however the loss of activity occurred only after the first exposure and was completely reversible upon catalyst reduction. The deactivation was attributed to an over-oxidation of the catalyst surface particularly noticeable in the case of very small Ru-clusters (1 nm). 相似文献
68.
The intact preen wax esters of the red knot Calidris canutus were studied with gas chromatography/mass spectrometry (GC/MS) and GC/MS/MS. In this latter technique, transitions from the
molecular ion to fragment ions representing the fatty acid moiety of the wax esters were measured, providing additional resolution
to the analysis of wax esters. The C21−C32 wax esters are composed of complex mixtures of hundreds of individual isomers. The odd carbon-numbered wax esters are predominantly
composed of even carbon-numbered n-alcohols (C14, C16, and C18) esterified predominantly with odd carbon-numbered 2-methyl fatty acids (C7, C9, C11, and C13), resulting in relatively simple distributions. The even carbon-numbered wax esters show a far more complex distribution
due to a number of factors: (i) Their n-alcohol moieties are not dominated by even carbon-numbered n-alcohol moieties are not dominated by even carbon-numbered n-alcohols esterified with odd carbon-numbered 2-methyl fatty acids, but odd and even carbon-numbered n-alcohols participate in approximately equal amounts; (ii) odd carbon-numbered methyl-branched alcohols participate abundantly
in these wax ester clusters; and (iii) with increasing molecular weight, various isomers of the 2,6-, 2,8-, and 2,10-dimethyl
branched fatty acids also participate in the even carbon-numbered wax esters. The data demonstrate that there is a clear biosynthetic
control on the wax ester composition although the reasons for the complex chemistry of the waxes are not yet understood. 相似文献
69.
Alain A Vertès Masayuki Inui Hideaki Yukawa 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2007,82(8):693-697
The challenges of implementing biorefineries on a global scale include socioeconomic, financial, and technological constraints. In particular, the development of biorefineries is tightly linked to the continued availability of fermentation raw materials. These constraints can be relaxed by the use of diverse raw materials, while advances that confer higher flexibility would enable biotechnological plant managers to swiftly react to volatile markets. In conventional processes, Saccharomyces cerevisiae grows on a relatively limited range of substrates, and produces only a single product—ethanol. Given the observed maturity of the S. cerevisiae fermentation technology, alternatives to baker's yeast may be needed to tip the economic balance in favour of biotechnological ethanol. These alternative fermentation technologies may allow a greater diversity of substrates to be used to produce an individually tailored mix of ethanol and other chemicals. Copyright © 2007 Society of Chemical Industry 相似文献
70.
Gilles Barnathan Joseph Mirallès Emile M. Gaydou Nicole Boury-Esnault Jean-Michel Kornprobst 《Lipids》1992,27(10):779-784
The fatty acid composition of phospholipids from the Senegalese spongeCinachyrella alloclada was examined. Two new fatty acids not hitherto found in nature, namely 10,13-octadecadienoic acid and 16-tricosenoic acid,
were identified. 8-Hexadecenoic, 13-nonadecenoic and 5,9,13-trimethyltretradecanoic fatty acids were also found for the first
time in sponges. The latter compound (1.4% of the total fatty acid mixture), an isoprenoid fatty acid, accompanies the major
fatty acid 4,8,12-trimethyltridecanoic acid (19.7%). The monomethyl branched fatty acids (22%) identified include 23-methylpentacosanoic
acid (anteiso-26∶0), not previously observed in sponged. The major long-chain fatty acids encountered were the known 17-tetracosenoic
19-heptacosadienoic and 5,9,23-tricontatrienoic acid. Some sixty fatty acids were identified as methyl esters andN-acyl pyrrolidides by gas chromatography and gas chromatography/mass spectrometry. 相似文献