全文获取类型
收费全文 | 15088篇 |
免费 | 407篇 |
国内免费 | 39篇 |
专业分类
电工技术 | 220篇 |
综合类 | 28篇 |
化学工业 | 2294篇 |
金属工艺 | 321篇 |
机械仪表 | 339篇 |
建筑科学 | 678篇 |
矿业工程 | 30篇 |
能源动力 | 313篇 |
轻工业 | 1802篇 |
水利工程 | 133篇 |
石油天然气 | 42篇 |
无线电 | 1549篇 |
一般工业技术 | 2220篇 |
冶金工业 | 3303篇 |
原子能技术 | 170篇 |
自动化技术 | 2092篇 |
出版年
2023年 | 70篇 |
2022年 | 150篇 |
2021年 | 254篇 |
2020年 | 164篇 |
2019年 | 232篇 |
2018年 | 276篇 |
2017年 | 258篇 |
2016年 | 329篇 |
2015年 | 212篇 |
2014年 | 374篇 |
2013年 | 761篇 |
2012年 | 575篇 |
2011年 | 733篇 |
2010年 | 592篇 |
2009年 | 541篇 |
2008年 | 626篇 |
2007年 | 607篇 |
2006年 | 522篇 |
2005年 | 503篇 |
2004年 | 391篇 |
2003年 | 391篇 |
2002年 | 342篇 |
2001年 | 336篇 |
2000年 | 314篇 |
1999年 | 348篇 |
1998年 | 1029篇 |
1997年 | 637篇 |
1996年 | 494篇 |
1995年 | 365篇 |
1994年 | 295篇 |
1993年 | 302篇 |
1992年 | 171篇 |
1991年 | 153篇 |
1990年 | 154篇 |
1989年 | 159篇 |
1988年 | 147篇 |
1987年 | 111篇 |
1986年 | 120篇 |
1985年 | 160篇 |
1984年 | 111篇 |
1983年 | 98篇 |
1982年 | 76篇 |
1981年 | 98篇 |
1980年 | 97篇 |
1979年 | 91篇 |
1978年 | 50篇 |
1977年 | 113篇 |
1976年 | 159篇 |
1975年 | 55篇 |
1973年 | 61篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
992.
David Y. Z. Chang Jon H. Van Gerpen Inmok Lee Lawrence A. Johnson Earl G. Hammond Stephen J. Marley 《Journal of the American Oil Chemists' Society》1996,73(11):1549-1555
The effects of using blends of methyl and isopropyl esters of soybean oil with No. 2 diesel fuel were studied at several steady-state
operating conditions in a four-cylinder turbocharged diesel engine. Fuel blends that contained 20, 50, and 70% methyl soyate
and 20 and 50% isopropyl soyate were tested. Fuel properties, such as cetane number, also were investigated. Both methyl and
isopropyl esters provided significant reductions in particulate emissions compared with No. 2 diesel fuel. A blend of 50%
methyl ester and 50% No. 2 diesel fuel provided a reduction of 37% in the carbon portion of the particulates and 25% in the
total particulates. The 50% blend of isopropyl ester and 50% No. 2 diesel fuel gave a 55% reduction in carbon and a 28% reduction
in total particulate emissions. Emissions of carbon monoxide and unburned hydrocarbons also were reduced significantly. Oxides
of nitrogen increased by 12%. 相似文献
993.
The effect of moisture on the fibre/matrix interaction in epoxy/anhydride composites is investigated and explained through the characterisation of the matrix cure in the interphase. The fibre/matrix interaction is inferred from ILSS measurements on the composite, which are compared with a recently-introduced DSC interaction parameter. The matrix cure in the bulk as well as in the interphase is characterised through FT-IR microspectroscopy. Complementary information is gained by measuring the overall Tg value. Moisture is shown to lower the fibre/matrix interaction if the prepreg (= composite precursor) is stored at room temperature or lower prior to final cure. This is due to the reduced crosslink density of the matrix. For PE prepreg stored in ordinary atmospheric conditions, moisture from the surroundings lowers the fibre/matrix interaction sharply. If the prepreg is stored in a dry environment, nearly no effect of the storage is detected on the fibre matrix interaction in PE (polyethylene) fibre composites, while for PVAL (polyvinylalcohol) fibre composites a strong decrease is still found, caused by water adsorbed at the more hydrophilic fibre surface. 相似文献
994.
Resonance is an interesting phenomenon that may be observed for reactions on catalytic surfaces during periodic forcing of operating variables. Forcing of the variables for non-linear systems may result in substantially changed time averaged behaviour. These resonance phenomena have been observed experimentally by coincidence rather than by systematic analysis. It is not clear for what type of reaction kinetics such behaviour may be expected and predictions are therefore impossible. Clearly, this forms a serious obstacle for any practical application. In this work we set out to analyse the nature of resonance behaviour in heterogeneously catalysed reactions. A Langmuir Hinshelwood microkinetic model is analysed. It is demonstrated that for weakly non-linear forcing variables — as inlet concentrations — forcing leads to resonance phenomena in terms of the reaction rate only in case high total surface occupancies exist in the steady state. In contrast, forcing of strongly non-linear variables — like temperature — may give rise to resonance phenomena for both low and high surface occupancies. Necessary conditions for resonance to occur are derived. The analysis of resonance phenomena is greatly simplified by the availability of explicit analytical expressions as can be derived from Carleman linearization. We will demonstrate the merits of Carleman linearization as compared to numerical integration. 相似文献
995.
This paper describes the use of an extruder for the plastification process of potato starch with glycerol and water as plasticizers. The influence of both plasticizers is expressed in the water absorption index (WAI) and water solubility index (WSI). The amount of water added prior to extrusion is a tool to protect the starch polymers from degradation and to improve the extruder performance. 相似文献
996.
Piezoelectric ceramics are widely used in sensors, actuators, and ultrasonic transducers due to their ability to achieve efficient conversion between electric and mechanical energy. There is a current drive toward lead‐free material systems capable of achieving comparable piezoelectric performance to environmentally hazardous, but commonly used, lead‐based materials such as lead zirconate titanate. This work constructs an accurate phase diagram for barium calcium titanate (Ba1‐xCaxTiO3 or BCTO). The substitution of Ca2+ on the Ba‐site of BCTO is of much interest due to electric property improvements compared to BaTiO3. In this work, Ba1‐xCaxTiO3 (x = 0‐0.30) samples have been made by solid‐state methods and, following initial characterization by X‐ray diffraction (XRD), evaluation of changes in the Raman spectra has allowed accurate determination of the phase transition temperatures and the construction of a phase diagram. 相似文献
997.
Prof. Aaron R. Van Dyke Lily S. Etemad Michael J. Vessicchio George A. Naclerio Victoria Jedson 《Chembiochem : a European journal of chemical biology》2016,17(17):1602-1605
A strategy for labeling native enzymes in a manner that preserves their activity is reported: capture–tag–release (CTR). Key to this approach is the small molecule CTR probe that contains an enzyme inhibitor, benzophenone crosslinker, and aryl phosphine ester. After UV‐derived capture of the enzyme, addition of an azide‐containing tag triggers a Staudinger ligation that labels the enzyme. A further consequence of the Staudinger ligation is fragmentation of the CTR probe, thus releasing the inhibitor and restoring enzymatic activity. As a proof‐of‐principle, the CTR strategy was applied to the hydrolase β‐galactosidase. The enzyme was efficiently labeled with biotin, and the kinetic data for the biotinylated enzyme were comparable to those for unlabeled β‐galactosidase. The CTR probe exhibits excellent targeting specificity, as it selectively labeled β‐galactosidase in a complex protein mixture. 相似文献
998.
999.
Rafaela Gladysz Prof. Dr. Anne‐Marie Lambeir Dr. Jurgen Joossens Prof. Dr. Koen Augustyns Prof. Dr. Pieter Van der Veken 《ChemMedChem》2016,11(5):467-476
Substrate activity screening (SAS) was presented a decade ago by Ellman and co‐workers as a straightforward methodology for the identification of fragment‐sized building blocks for enzyme inhibitors. Ever since, SAS and variations derived from it have been successfully applied to the discovery of inhibitors of various families of enzymatically active drug targets. This review covers key achievements and challenges of SAS and related methodologies, including the modified substrate activity screening (MSAS) approach. Special attention is given to the kinetic and thermodynamic aspects of these methodologies, as a thorough understanding thereof is crucial for successfully transforming the identified fragment‐sized hits into potent inhibitors. 相似文献
1000.
Tamara Tomašegović David Beynon Tim Claypole Sanja Mahović Poljaček 《Journal of Coatings Technology and Research》2016,13(5):815-828
Printed functional materials are a rapidly growing area of interest for low-cost high-speed device manufacture with flexographic printing seen as a route to achieving this. The relationship between surface tension of the ink and surface free energy (SFE) of the photopolymer plate is a key for optimum performance. However, traditional methods of surface tension modification of the ink/coating often cannot be employed for functional inks. In this research, rapid, permanent modification of flexographic printing plate’s SFE is achieved through controlled UV-ozone treatment, and the effects of the treatment on the polar and dispersive component of SFE are analyzed by Fourier transform infrared attenuated total reflectance spectroscopy, swelling experiments, and roughness measurements. Printing trials using the modified printing plates reveal improved print uniformity and control of deposited ink layer thickness, as well as improved print features—particularly track and pad junctions which can be problematic for printed electronic applications. The ability to rapidly tailor printing plate SFE is of benefit to all volume printing applications. Furthermore, it is of critical importance for functional printing and printed electronics where surface tension of the ink is determined by the functional material and chemical modification is not possible or desirable. 相似文献