全文获取类型
收费全文 | 24971篇 |
免费 | 921篇 |
国内免费 | 33篇 |
专业分类
电工技术 | 340篇 |
综合类 | 38篇 |
化学工业 | 5724篇 |
金属工艺 | 405篇 |
机械仪表 | 486篇 |
建筑科学 | 1311篇 |
矿业工程 | 100篇 |
能源动力 | 625篇 |
轻工业 | 1898篇 |
水利工程 | 234篇 |
石油天然气 | 74篇 |
无线电 | 1827篇 |
一般工业技术 | 4530篇 |
冶金工业 | 4579篇 |
原子能技术 | 203篇 |
自动化技术 | 3551篇 |
出版年
2023年 | 215篇 |
2022年 | 363篇 |
2021年 | 570篇 |
2020年 | 340篇 |
2019年 | 435篇 |
2018年 | 538篇 |
2017年 | 467篇 |
2016年 | 635篇 |
2015年 | 559篇 |
2014年 | 753篇 |
2013年 | 1438篇 |
2012年 | 1170篇 |
2011年 | 1518篇 |
2010年 | 1087篇 |
2009年 | 1023篇 |
2008年 | 1157篇 |
2007年 | 1093篇 |
2006年 | 954篇 |
2005年 | 763篇 |
2004年 | 747篇 |
2003年 | 661篇 |
2002年 | 571篇 |
2001年 | 432篇 |
2000年 | 365篇 |
1999年 | 404篇 |
1998年 | 762篇 |
1997年 | 564篇 |
1996年 | 447篇 |
1995年 | 415篇 |
1994年 | 386篇 |
1993年 | 364篇 |
1992年 | 270篇 |
1991年 | 197篇 |
1990年 | 271篇 |
1989年 | 262篇 |
1988年 | 216篇 |
1987年 | 226篇 |
1986年 | 230篇 |
1985年 | 269篇 |
1984年 | 227篇 |
1983年 | 226篇 |
1982年 | 209篇 |
1981年 | 195篇 |
1980年 | 172篇 |
1979年 | 194篇 |
1978年 | 167篇 |
1977年 | 190篇 |
1976年 | 234篇 |
1975年 | 163篇 |
1974年 | 126篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Mcmullen Thomas B. Salamida Dominic P. 《Industry Applications, IEEE Transactions on》1976,(5):527-529
Operation of an elastomeric blade requires the use of a boundary lubricant to remove residual xerographic toner from the photoreceptor efficiently. A radioactive tracer technique was used to study the behaviour of a number of lubricants used in the xerographic process. Both filming and nonfilming type lubricants were investigated using this technique. The results indicated that the lubricant film deposited on the photoreceptor must be in the thickness range of from 1 to 3 molecular layers for acceptable xerographic development and cleaning. Film thickness was shown to be dependent on the class of lubricant, the concentration of lubricant in toner, and the inclusion of a silica compound in the toner. Films are dynamic in nature, continuously being formed and removed during the xerographic process. Parameters affecting the filming mechanism are discussed. 相似文献
992.
McFadyen Iain J.; Metzger Thomas G.; Paterlini M.Germana; Ferguson David M. 《Protein engineering, design & selection : PEDS》2001,14(12):953-960
Previous studies have probed the structural basis of ligandselectivity in the mu, delta and kappa opioid receptors throughthe application of molecular modeling techniques in concertwith the `messageaddress' concept. Here, this approachwas used in an attempt to rationalize the unique pharmacologicalprofile of a recently cloned novel opioid receptor, ZFOR1 (ZebraFishOpioid Receptor 1). Specifically, a model of the transmembranedomains of ZFOR1 was constructed and used to explore the bindingmodes of various prototypical opioid ligands. The results showthat the `message' portion of the binding pocket of ZFOR1 ishighly conserved; hence, the binding modes of non-selectiveopioid ligands are well preserved. In contrast, a small numberof variant residues at the extracellular end of the bindingpocket, particularly Lys288 (VI:26) and Trp304 (VII:03), areshown to create adverse steric interactions with all delta andkappa selective ligands examined, thereby disrupting their bindingmodes. These results are consistent with, and serve as an explanationfor, the observed pharmacology of this receptor, lending supportto both the validity of the `messageaddress' conceptitself and to the use of molecular modeling approaches in itsapplication. 相似文献
993.
Nanosized zeolite films for vapor-sensing applications 总被引:2,自引:0,他引:2
Colloidal zeolites LTA and BEA sized below 100 nm were synthesized as building blocks for the controlled growth of thin microporous films on piezoelectric sensor devices (quartz crystal microbalance, QCM). The zeolite films were prepared on pre-seeded gold substrates on QCM devices. Initially, a layer of colloidal particles was deposited on the support through chemical bonding with a silane coupling agent, followed by hydrothermal growth. BEA- and LTA-type zeolite films with thicknesses of 250 and 450 nm, respectively, were prepared by optimizing the synthesis conditions. The application of these zeolite films in microsensors for water and organic compounds is presented. The importance of the zeolite structure type with respect to the sensitivity towards different organic and water vapors at various concentrations is discussed. Both zeolites are thermally stable and show reproducible responses during long-term experiments. Based on these results, it was concluded that both zeolite films could be used effectively as humidity sensor materials for water vapor sensing purposes. High sensitivity, good reversibility and long life were demonstrated for this type of zeolite film at low water concentrations. In comparison to LTA, the BEA films show a higher sorption capacity towards water vapor and no rejection of pentane, hexane and cyclohexane, due to the larger pore size of the BEA structure. 相似文献
994.
This paper describes the role of pressurized electroosmotic dewatering (EOD) in a filter cycle. A laboratory-scale filter-press was used to filter a highly conductive silica suspension under constant pressure, followed by washing and mechanical precompression of the filter cake and finally by pressurized EOD at constant electric current. The influence of filter cycle parameters (filtration and washing pressure and duration, mechanical pressure, and electric field intensity) on the final cake dryness and energy consumption was studied. Electrodes of different materials, forms, and surfaces were used.
The optimal conditions of each filter cycle operation were found to minimize the energy consumption during EOD and maximize the cake dryness. With mechanical pressure and electric field intensity increasing, the total energy consumption increased, but the specific energy consumption (per kg of expressed water) decreased, and the final filter cake was dryer. The pressurized EOD also used less energy than thermal drying. 相似文献
The optimal conditions of each filter cycle operation were found to minimize the energy consumption during EOD and maximize the cake dryness. With mechanical pressure and electric field intensity increasing, the total energy consumption increased, but the specific energy consumption (per kg of expressed water) decreased, and the final filter cake was dryer. The pressurized EOD also used less energy than thermal drying. 相似文献
995.
Fabrication of Long Lengths of Epitaxial Buffer Layers on Biaxially Textured Nickel Substrates Using a Continuous Reel-to-Reel Dip-Coating Unit 总被引:2,自引:0,他引:2
M. Parans Paranthaman Thomas G. Chirayil Fred A. List Xingtian Cui Amit Goyal Dominic F. Lee Eliot D. Specht Patrick M. Martin Robert K. Williams Donald M. Kroeger Jonathan S. Morrell David B. Beach Ron Feenstra David K. Christen 《Journal of the American Ceramic Society》2001,84(2):273-78
A low-cost, nonvacuum, solution precursor route has been developed to produce epitaxial oxide buffer layers of Eu2 O3 or La2 Zr2 O7 on biaxially textured Ni (100) tapes. A reel-to-reel continuous dip-coating unit consisting of a constant-tension tape transport system attached to a controlled atmosphere furnace was fabricated. Nickel tapes were pulled through a 2-methoxyethanol solution of europium methoxyethoxide/acetate or lanthanum zirconium methoxyethoxide. The double-sided dip-coated tapes were then annealed in a preheated furnace at 1000°–1100°C with a high flow rate of Ar/H2 (4%) gas. The dip-coated buffers were dense, continuous, crack-free, and epitaxial with a single cube texture. A critical current ( J c ) of >1 MA/cm2 at 77 K and self-field was obtained for YBa2 Cu3 O7-δ (YBCO) films with a layer sequence of YBCO ( ex situ BaF2 process)/CeO2 (sputtered)/YSZ (sputtered)/Eu2 O3 (dip-coated)/nickel. We have produced 1–2 m lengths of epitaxial buffer layers on textured nickel substrates using a nonvacuum process for the first time. 相似文献
996.
Peter Biedenkopf Thomas Karwath Dietmar Kobertz Manisha Rane Egbert Wessel Klaus Hilpert Lorenz Singheiser 《Journal of the American Ceramic Society》2001,84(7):1445-1452
The corrosion and vaporization behavior of eight commercial refractories containing Cr2 O3 were investigated under simulated pressurized pulverized coal combustion (PPCC) conditions at 1723 K in the presence of liquid slag. The corrosion resistance of the refractory materials decreased with increased content of free Cr2 O3 , because bursting (reaction of Fe3 O4 with Cr2 O3 ) occurred. Refractories containing MgCr2 O4 with dissolved Al2 O3 showed the highest corrosion resistance. Thermodynamic calculations showed that CrO3 and CrO2 (OH)2 were the most volatile species in air and in PPCC flue gas, whereas additions of A2 O (A = Na and K, minor slag component) increased the chromium vaporization significantly because of A2 CrO4 formation. Knudsen effusion mass spectrometry measurements showed that the chromium vaporization of refractories was directly correlated to the Cr2 O3 content of the material. In contrast, refractories containing MgCr2 O4 showed a significant decrease in chromium vaporization. 相似文献
997.
Robert Günther Thomas Klassen Birte Dickau Frank Gärtner Arno Bartels Rüdiger Bormann 《Journal of the American Ceramic Society》2001,84(7):1509-1513
New (inter)metallic-ceramic composites for high-temperature structural and functional applications are prepared via high-energy ball milling. During compaction by pressureless sintering, dense Al2 O3 /Ti-based alloy composites are formed that consist of inter-connected networks of the ceramic and the (inter)metallic phases. Ti-Al-V/Al2 O3 and Ti-Al-Nb/Al2 O3 composites show enhanced damage tolerance over monolithic Al2 O3 , i.e ., fracture toughnesses up to 5.6 MPa·m0.5 and bending strengths up to 527 MPa. The resistance against abrasive wear is almost doubled with respect to monolithic Al2 O3 ceramic. Electrical resistivity scales with the ceramic volume fraction and ranges between 0.3 mΩ·cm and 55.1 mΩ·cm, with only a weak temperature dependence ≤700°C. 相似文献
998.
Runcy Wilson Tomás S. Plivelic Abi Santhosh Aprem C. Ranganathaiagh S. Anil Kumar Sabu Thomas 《应用聚合物科学杂志》2012,123(6):3806-3818
Poly (ethylene‐co‐vinyl acetate) (EVA)/clay nanocomposites containing two different organoclays with different clay loadings were prepared. The transport of gases (oxygen and nitrogen) through the composite membranes was investigated and the results were compared. These studies revealed that the incorporation of nanoclays in the polymer increased the efficiency of the membranes toward barrier properties. It was also found that the barrier properties of the membranes decreased with clay loadings. This is mainly due to the aggregation of clay at higher loadings. The morphology of the nanocomposites was studied by scanning electron microscopy, transmission electron microscopy and X‐ray scattering. Small angle X‐ray scattering results showed significant intercalation of the polymer chains between the organo‐modified silicate layers in all cases. Better dispersed silicate layer stacking and more homogeneous membranes were obtained for Cloisite® 25A based nanocomposites compared with Cloisite® 20A samples. Microscopic observations (SEM and TEM) were coherent with those results. The dispersion of clay platelets seemed to be maximized for 3 wt % of clay and agglomeration increased with higher clay loading. Wide angle X‐ray scattering results showed no significant modifications in the crystalline structure of the EVA matrix because of the presence of the clays. The effect of free volume on the transport behavior was studied using positron annihilation spectroscopy. The permeability results have been correlated with various permeation models. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
999.
Stella Georgiadou Lili Jin Noreen. L. Thomas Marianne. Gilbert Brian W. Brooks 《应用聚合物科学杂志》2012,124(3):1824-1830
Inorganic nanoparticles such as calcium carbonate, silica, or hydrotalcite were dispersed in vinyl chloride prior to suspension polymerization. That led to the production of poly(vinyl chloride) (PVC) composite grains with higher porosity and different internal morphology from those of commercial PVC. The PVC/composite grain sizes and their distribution were also influenced by the presence of nanofillers. The distribution of filler nanoparticles (either calcium carbonate or silica) was not uniform throughout the PVC grains. Regions of high and low filler concentration were observed. Regions of pure polymer were also observed. Reasons for that are suggested. Hydrotalcite did not remain in the PVC grains. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
1000.
A. Manuel Stephan T. Prem Kumar Sabu Thomas P. Selvin Thomas Roberta Bongiovanni Jijeesh R. Nair N. Angulakshmi 《应用聚合物科学杂志》2012,124(4):3245-3254
Nanocomposite polymer electrolytes (NCPEs) composed of poly(ethylene oxide), calcium phosphate [Ca3(PO4)2], and lithium perchlorate (LiClO4)/lithium bis(trifluoromethane sulfonyl)imide [LiN(CF3SO2)2 or LiTFSI] in various proportions were prepared by a hot‐press method. The membranes were characterized by scanning electron microscopy, differential scanning calorimetry, thermogravimetry–differential thermal analysis, ionic conductivity testing, and transference number studies. The free volume of the membranes was probed by positron annihilation lifetime spectroscopy at 30°C, and the results supported the ionic conductivity data. The NCPEs with LiClO4 exhibited higher ionic conductivities than the NCPE with LiTFSI as a salt. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献