全文获取类型
收费全文 | 1460篇 |
免费 | 127篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 23篇 |
综合类 | 1篇 |
化学工业 | 464篇 |
金属工艺 | 13篇 |
机械仪表 | 30篇 |
建筑科学 | 61篇 |
矿业工程 | 3篇 |
能源动力 | 44篇 |
轻工业 | 207篇 |
水利工程 | 12篇 |
石油天然气 | 1篇 |
无线电 | 119篇 |
一般工业技术 | 234篇 |
冶金工业 | 109篇 |
原子能技术 | 8篇 |
自动化技术 | 260篇 |
出版年
2024年 | 2篇 |
2023年 | 32篇 |
2022年 | 93篇 |
2021年 | 109篇 |
2020年 | 56篇 |
2019年 | 63篇 |
2018年 | 71篇 |
2017年 | 58篇 |
2016年 | 79篇 |
2015年 | 57篇 |
2014年 | 89篇 |
2013年 | 117篇 |
2012年 | 109篇 |
2011年 | 114篇 |
2010年 | 84篇 |
2009年 | 41篇 |
2008年 | 64篇 |
2007年 | 53篇 |
2006年 | 48篇 |
2005年 | 43篇 |
2004年 | 22篇 |
2003年 | 21篇 |
2002年 | 19篇 |
2001年 | 9篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 31篇 |
1997年 | 21篇 |
1996年 | 12篇 |
1995年 | 10篇 |
1994年 | 5篇 |
1993年 | 10篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1968年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有1589条查询结果,搜索用时 0 毫秒
1.
Luigi Lazzeri Maria Grazia Cascone Simone Quiriconi Letterio Morabito Paolo Giusti 《Polymer International》2005,54(1):101-107
Biodegradable hollow microfibres containing particles loaded with specific active agents can be potentially employed to produce a special kind of substrate for tissue engineering, able to function as a scaffold and at the same time to act as a drug‐releasing system. Biodegradable hollow microfibres based on poly(lactic acid) were produced by a dry–wet spinning procedure. Drug‐loaded microparticles were prepared by a simple oil‐in‐water emulsion and entrapped inside the fibres. The morphology of both fibres and particles was investigated by scanning electron microscopy. The mechanical and thermal properties of the fibres were investigated by tensile tests and differential scanning calorimetry. In vitro tests were performed to evaluate the release of the drug from the fibres loaded with the particles Copyright © 2004 Society of Chemical Industry 相似文献
2.
R Santinelli C Tolone R Toraldo G Canino A De Simone M D'Avanzo 《Canadian Metallurgical Quarterly》1998,55(6):854-856
OBJECTIVE: To describe a mother and her 2 sons affected by idiopathic intracranial hypertension (IIH), associated in the sons with root irritation symptom. Unlike the other 4 families reported previously, obesity was not present in our patients. DESIGN: Case reports. SETTING: Department of pediatrics in a university school of Medicine, Naples, Italy. PATIENTS: A mother (aged 36 years) and her 2 sons (aged 14 and 9 years) developed IIH at different times. Neuroimaging showed an empty sella in the mother, while IIH was associated with spinal and radicular pain in her 2 sons. The mother and the younger son developed permanent visual loss. CONCLUSIONS: Ophthalmologic follow-up in our patients indicates that IIH is a chronic disease. Surgical treatment should be considered an option. 相似文献
3.
Alberto Carpinteri Bernardino Chiaia Simone Puzzi 《Engineering Fracture Mechanics》2007,74(17):2892-2896
Aim of this letter to the Editor is at replying to the criticisms raised by Ba?ant and Yavari [Ba?ant ZP, Yavari A. Is the cause of size effect on structural strength fractal or energetic - statistical? Engng Fract Mech 2005;72:1-31] against the fractal approach to the size-scale effects on the mechanical properties of materials and the concept of the Multi-Fractal Scaling Law presented by Carpinteri [Carpinteri A. Scaling laws and renormalization groups for strength and toughness of disordered materials. Int J Solids Struct 1994;31:291-302]. These criticisms will be analysed thoroughly, showing how they also contain some mistakes and misunderstandings. The presented elucidations should redirect the discussion to a more correct scientific debate. 相似文献
4.
To clarify whether motion information per se has a separable influence on action control, the authors investigated whether irrelevant direction of motion of stimuli whose overall position was constant over time would affect manual left-right responses (i.e., reveal a motion-based Simon effect). In Experiments 1 and 2, significant Simon effects were obtained for sine-wave gratings moving in a stationary Gaussian window. In Experiment 3, a direction-based Simon effect with random-dot patterns was replicated, except that the perceived direction of motion was based on the displacement of single elements. Experiments 4 and 5 studied motion-based Simon effects to point-light figures that walked in place--displays requiring high-level analysis of global shape and local motion. Motion-based Simon effects occurred when the displays could be interpreted as an upright human walker, showing that a high-level representation of motion direction mediated the effects. Thus, the present study establishes links between high-level motion perception and action. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
Tungsten oxide and molybdenum doped tungsten oxide electrochromic films have been electrochemically prepared from a metal peroxide bath and experimentally tested. They were characterized by electrical and optical methods, using cyclic voltammograms and calculating the charge capacity as a function of the number of deposition cycles.The color of the electrochromic WO3 film is strongly altered by doping it with molybdenum. Electrochromic W---Mo oxide films were fabricated by adding different percentages of molybdenum to tungsten oxide, ranging from 0.5% to 7% weight of deposition solution. Normal optical transmittance was also measured and evidence is given of different behavior if the switching for oxidation and reduction cycle, so that coloration occurs in a shorter time than the bleaching. The time constant of the process tends to increase as a function of the molybdenum oxide doping concentration. 相似文献
6.
Leonardo Badia Andrea Baiocchi Alfredo Todini Simone Merlin Silvano Pupolin Andrea Zanella Michele Zorzi 《Wireless Communications, IEEE》2007,14(1):36-43
Multicellular networks based on the IEEE 802.16 standard appear to be very promising candidates to provide end users with broadband wireless access. However, they also pose interesting challenges in terms of radio resource management, where several design choices are not specified in the standard, intentionally left open to implementors. For this reason, we focus in this article on scheduling and resource allocation, and investigate how they could operate in a cross-layer fashion. In particular, we describe the principles of joint scheduling and resource allocation for IEEE 802.16 operating in AMC mode, and discuss the critical role played by physical layer considerations, especially intercell interference estimation and channel state awareness, in the obtained performance. This leads to identifying key open issues and possible general solutions 相似文献
7.
Electrostatic destabilization of water-in-crude oil emulsions: Application to a real case and evaluation of the Aibel VIEC technology 总被引:1,自引:0,他引:1
In the current study, the Aibel Vessel Internal Electrostatic Coalescer (VIEC) technology was tested for a real case scenario encountered in the production train of a UK oil field. Depressurized samples were collected both upstream and downstream of the first stage separator. The separation performance was discussed with respect to water cut and droplet size distribution of the emulsions, and the effect of chemical treatment. Issues with respect to representative sampling and testing have been discussed. The application of an external AC electrical field has been shown to significantly enhance the separation of the aqueous phase from tight emulsions, both when it was used alone and in combination with a commercial demulsifier. By using the VIEC technology, the time for separation could be reduced from 8 min to 2 min and the overall BS&W in the emulsions was improved from 45% or 60% to a residual water content of 5-20%. Destabilization of a 45% water-in-oil emulsion by electrical and chemical treatment (20/40 ppm) produced oil in the 2-7% BS&W range whereas the corresponding tests without applying an electrostatic field led to a BS&W greater than 25%. The achieved results strongly suggest that the VIEC technology can resolve the stable emulsion bands encountered in the Schiehallion train and add flexibility or increased production rate to the process. The results also suggest the importance of further studies on the destabilization performances achieved by electrostatic means. 相似文献
8.
Clifford E Felder Simone A Botti Shneior Lifson Israel Silman Joel L Sussman 《Journal of molecular graphics & modelling》1997,15(5):318-327
The electrostatic potentials for the three-dimensional structures of cholinesterases from various species were calculated, using the Delphi algorithm, on the basis of the Poisson–Boltzmann equation. We used structures for Torpedo californica and mouse acetylcholinesterase, and built homology models of the human, Bungarus fasciatus, and Drosophila melanogaster acetylcholinesterases and human butyrylcholinesterase. All these structures reveal a negative external surface potential, in the area around the entrance to the active-site gorge, that becomes more negative as the rim of the gorge is approached. Moreover, in all cases, the potential becomes increasingly more negative along the central axis running down the gorge, and is largest at the base of the gorge, near the active site. Ten key acidic residues conserved in the sequence alignments of AChE from various species, both in the surface area near the entrance of the active-site gorge and at its base, appear to be primarily responsible for these potentials. The potentials are highly correlated among the structures examined, down to sequence identities as low as 35%. This indicates that they are a conserved property of the cholinesterase family, could serve to attract the positively charged substrate into and down the gorge to the active site, and may play other roles important for cholinesterase function. 相似文献
9.
Boussinot F. de Simone R. 《IEEE transactions on pattern analysis and machine intelligence》1996,22(4):256-266
We present SL, a new programming language of the synchronous reactive family in which hypotheses about signal presence/absence are disallowed. One can decide that a signal is absent during an instant only at the end of this instant, and so reaction to this absence is delayed to the next instant. Sources of causal circularities are avoided, while only weak preemption remains. A structural operational semantics is provided through rewrite rules, and an implementation is described. In addition to directly executing programs, this implementation can also be used to produce automata by symbolic evaluation 相似文献
10.
Simone Fulvio Rollini Roberto Bruttomesso Natasha Sharygina Aliaksei Tsitovich 《Formal Methods in System Design》2014,45(1):1-41
Verification methods based on SAT, SMT, and theorem proving often rely on proofs of unsatisfiability as a powerful tool to extract information in order to reduce the overall effort. For example a proof may be traversed to identify a minimal reason that led to unsatisfiability, for computing abstractions, or for deriving Craig interpolants. In this paper we focus on two important aspects that concern efficient handling of proofs of unsatisfiability: compression and manipulation. First of all, since the proof size can be very large in general (exponential in the size of the input problem), it is indeed beneficial to adopt techniques to compress it for further processing. Secondly, proofs can be manipulated as a flexible preprocessing step in preparation for interpolant computation. Both these techniques are implemented in a framework that makes use of local rewriting rules to transform the proofs. We show that a careful use of the rules, combined with existing algorithms, can result in an effective simplification of the original proofs. We have evaluated several heuristics on a wide range of unsatisfiable problems deriving from SAT and SMT test cases. 相似文献