全文获取类型
收费全文 | 1460篇 |
免费 | 106篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 421篇 |
金属工艺 | 39篇 |
机械仪表 | 35篇 |
建筑科学 | 59篇 |
矿业工程 | 3篇 |
能源动力 | 32篇 |
轻工业 | 379篇 |
水利工程 | 12篇 |
石油天然气 | 5篇 |
无线电 | 80篇 |
一般工业技术 | 183篇 |
冶金工业 | 63篇 |
原子能技术 | 8篇 |
自动化技术 | 241篇 |
出版年
2024年 | 9篇 |
2023年 | 13篇 |
2022年 | 32篇 |
2021年 | 85篇 |
2020年 | 52篇 |
2019年 | 54篇 |
2018年 | 54篇 |
2017年 | 51篇 |
2016年 | 76篇 |
2015年 | 44篇 |
2014年 | 70篇 |
2013年 | 116篇 |
2012年 | 102篇 |
2011年 | 102篇 |
2010年 | 91篇 |
2009年 | 76篇 |
2008年 | 64篇 |
2007年 | 50篇 |
2006年 | 51篇 |
2005年 | 50篇 |
2004年 | 37篇 |
2003年 | 45篇 |
2002年 | 29篇 |
2001年 | 13篇 |
2000年 | 22篇 |
1999年 | 22篇 |
1998年 | 12篇 |
1997年 | 15篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 7篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 7篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1978年 | 6篇 |
1977年 | 9篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1970年 | 5篇 |
排序方式: 共有1569条查询结果,搜索用时 15 毫秒
11.
Hans-Joachim Kleebe Gabriela Hilz Günter Ziegler 《Journal of the American Ceramic Society》1996,79(10):2592-2600
Sol-gel-derived mullite ceramics were processed by pressureless sintering at 1600°, 1650°, and 1700°C for 4 h. Microstructural and microchemical characterization of the mullite materials was performed using transmission electron microscopy, in conjunction with energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy (EELS). Apart from mullite grain diameter and triplepocket size, no major microstructural changes were observed with increasing sintering temperature. Residual glass was present at triple pockets and along two-grain junctions. Not all grain boundaries revealed the presence of a continuous amorphous intergranular film. Clean interfaces were observed only at boundaries with one grain parallel to the [001] orientation (low-energy configuration). Quantitative EELS analysis of mullite grains and glass pockets revealed only small changes in composition with increasing sintering temperature; i.e., the alumina:silica ratio slightly increased for mullite and glass. The analysis implied that mullite with this relatively high aluminum content would not be stable adjacent to residual glass. However, a stable glass-mullite system has been proposed, because impurity cations were detected within glass pockets, which suggested a slight shift of the subsolidus line (glass-mullite/ mullite) to a higher amount of alumina. Energy-loss nearedge structure studies of the Si- L 2,3 edge revealed a similar near-edge structure for the mullite, residual glass, and quartz. Thus, SiO4 tetrahedra were thought to be the main building units of the glass contained in sintered mullite. 相似文献
12.
Guy-Bart Stan Rodolphe Sepulchre 《Automatic Control, IEEE Transactions on》2007,52(2):256-270
This paper employs dissipativity theory for the global analysis of limit cycles in particular dynamical systems of possibly high dimension. Oscillators are regarded as open systems that satisfy a particular dissipation inequality. It is shown that this characterization has implications for the global stability analysis of limit cycle oscillations: i) in isolated oscillators, ii) in interconnections of oscillators, and iii) for the global synchrony analysis in interconnections of identical oscillators 相似文献
13.
Wei Huang Ghosh S. Velusamy S. Sankaranarayanan K. Skadron K. Stan M.R. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2006,14(5):501-513
This paper presents HotSpot-a modeling methodology for developing compact thermal models based on the popular stacked-layer packaging scheme in modern very large-scale integration systems. In addition to modeling silicon and packaging layers, HotSpot includes a high-level on-chip interconnect self-heating power and thermal model such that the thermal impacts on interconnects can also be considered during early design stages. The HotSpot compact thermal modeling approach is especially well suited for preregister transfer level (RTL) and presynthesis thermal analysis and is able to provide detailed static and transient temperature information across the die and the package, as it is also computationally efficient. 相似文献
14.
15.
Unni Olsbye Anastasia Virnovskaia Øystein Prytz Stan J. Tinnemans Bert M. Weckhuysen 《Catalysis Letters》2005,103(1-2):143-148
A Cr/Al2O3 alkane dehydrogenation catalyst exhibits a maximum in ethylene yield during an ethane dehydrogenation cycle. Isotopic labelling experiments with monolabelled 13C-ethane and deuterium were used to elucidate whether the initial activity increase could be due to formation of an active, larger hydrocarbon intermediate on the surface. The results strongly indicate that this is not the case, and instead point to a traditional reaction cycle involving adsorption of ethane to form an ethyl species, followed by desorption of ethene and hydrogen. Transient kinetic data suggest that ethane adsorption is the rate-determining step of reaction. 相似文献
16.
Despite the successes in the last two decades, the state-of-the-art face detectors still have problems in dealing with images in the wild due to large appearance variations. Instead of leaving appearance variations directly to statistical learning algorithms, we propose a hierarchical part based structural model to explicitly capture them. The model enables part subtype option to handle local appearance variations such as closed and open month, and part deformation to capture the global appearance variations such as pose and expression. In detection, candidate window is fitted to the structural model to infer the part location and part subtype, and detection score is then computed based on the fitted configuration. In this way, the influence of appearance variation is reduced. Besides the face model, we exploit the co-occurrence between face and body, which helps to handle large variations, such as heavy occlusions, to further boost the face detection performance. We present a phrase based representation for body detection, and propose a structural context model to jointly encode the outputs of face detector and body detector. Benefit from the rich structural face and body information, as well as the discriminative structural learning algorithm, our method achieves state-of-the-art performance on FDDB, AFW and a self-annotated dataset, under wide comparisons with commercial and academic methods. 相似文献
17.
Gina‐Gabriela Bumbu Cornelia Vasile Maria Cristina Popescu Hristea Darie Gabrielle Charlotte Chianu Gheorghe Singurel Adrian Carpov 《应用聚合物科学杂志》2003,88(11):2585-2597
The compatibility of the hydroxypropyl cellulose (HPC) with maleic acid–vinyl acetate copolymer in the solid state was studied by thermogravimetry, thermo‐optical analysis, differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and optical microscopy. It was established that physical interactions are prevalent in blends with a high content of HPC, whereas chemical interactions predominate in blends with a medium and low content of HPC. By increasing the temperature, the thermochemical reactions are favored. Thermal properties are dependent on the mixing ratio of the components. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2585–2597, 2003 相似文献
18.
Michael?J.?HaasEmail author Paul?J.?Michalski Stan?Runyon Alberto?Nunez Karen?M.?Scott 《Journal of the American Oil Chemists' Society》2003,80(1):97-102
Simple alkyl FA esters have numerous uses, including serving as biodiesel, a fuel for compression ignition (diesel) engines.
The use of acid-catalyzed esterification for the synthesis of FAME from acid oil, a by-product of edible vegetable oil refining
that is produced from soapstock, was investigated. Soybean acid oil contained 59.3 wt% FFA, 28.0 wt% TAG, 4.4 wt% DAG, and
less than 1% MAG. Maximum esterification occurred at 65°C and 26 h reaction at a molar ratio of total FA/methanol/sulfuric
acid of 1∶15∶1.5. Residual unreacted species under these conditions, as a fraction of their content in unesterified acid oil,
were FFA, 6.6%; TAG, 5.8%; and DAG, 2.6%. This corresponds to estimated concentrations of FFA, 3.2%; TAG, 1.3%; and DAG, 0.2%,
on a mass basis, in the ester product. In an alternative approach, the acylglycerol species in soapstock were saponified prior
to acidulation. High-acid (HA) acid oil made from this saponified soapstock had an FFA content of 96.2 wt% and no detectable
TAG, DAG, or MAG. Optimal esterification conditions for HA acid oil at 65°C were a mole ratio of FFA/methanol/acid of 1∶1.8∶0.17,
and 14 h incubation. FAME recovery under these conditions was 89% of theoretical, and the residual unesterified FFA content
was approximately 20 mg/g. This was reduced to 3.5 mg/g, below the maximum FFA level allowed for biodiesel, by washing with
NaCl, NaHCO3, and Ca(OH)2 solutions. Alternatively, by subjecting the unwashed ester layer to a second esterification, the FFA level was reduced to
less than 2 mg/g. The acid value of this material exceeded the maximum allowed for biodiesel, but was reduced to an acceptable
value by a brief wash with 0.5 N NaOH. 相似文献
19.
20.
Rafael Prikladnicki Alexander Boden Gabriela Avram Cleidson R. B. de Souza Volker Wulf 《Empirical Software Engineering》2014,19(4):822-856
Global Software Engineering has become a standard in today’s software industry. Research in distributed software development poses severe challenges that are due to the spatial and temporal distribution of the actors, as well as to language, intercultural and organizational aspects. These challenges occur in addition to “traditional” challenges of the domain itself in large-scale software projects, like coordination and communication issues, requirements volatily, lack of domain knowledge, among others. While several authors have reported empirical studies of global software development projects, the methodological difficulties and challenges of this type of studies have not been sufficiently discussed. In this paper, we share our experiences of collecting and analysing qualitative data in the context of Global Software Engineering projects. We discuss strategies for gaining access to field sites, building trust and documenting distributed and complex work practices in the context of several research projects we have conducted in the past 9 years. The experiences described in this paper illustrate the need to deal with fundamental problems, such as understanding local languages and different cultures, observing synchronous interaction, or dealing with barriers imposed by political conflicts between the sites. Based on our findings, we discuss some practical implications and strategies that can be used by other researchers and provide some recommendations for future research in methodological aspects of Global Software Engineering. 相似文献