全文获取类型
收费全文 | 695篇 |
免费 | 27篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 16篇 |
综合类 | 2篇 |
化学工业 | 222篇 |
金属工艺 | 10篇 |
机械仪表 | 8篇 |
建筑科学 | 18篇 |
能源动力 | 21篇 |
轻工业 | 140篇 |
石油天然气 | 1篇 |
无线电 | 40篇 |
一般工业技术 | 166篇 |
冶金工业 | 42篇 |
原子能技术 | 8篇 |
自动化技术 | 29篇 |
出版年
2023年 | 4篇 |
2022年 | 11篇 |
2021年 | 17篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 12篇 |
2017年 | 12篇 |
2016年 | 14篇 |
2015年 | 11篇 |
2014年 | 17篇 |
2013年 | 38篇 |
2012年 | 28篇 |
2011年 | 41篇 |
2010年 | 29篇 |
2009年 | 29篇 |
2008年 | 21篇 |
2007年 | 37篇 |
2006年 | 25篇 |
2005年 | 24篇 |
2004年 | 16篇 |
2003年 | 30篇 |
2002年 | 37篇 |
2001年 | 20篇 |
2000年 | 8篇 |
1999年 | 9篇 |
1998年 | 26篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 17篇 |
1994年 | 13篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 15篇 |
1990年 | 15篇 |
1989年 | 12篇 |
1988年 | 4篇 |
1987年 | 12篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1973年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有723条查询结果,搜索用时 21 毫秒
81.
The authors present a method by which to construct a fast N*N self-routing space switch network with identical 2*2 switch elements. This network is nonblocking and employs O(N log/sup 3/ N) switch elements; each element uses just two bits of the output port address for switching control.<> 相似文献
82.
Density measurements in the compressed liquid phase for ethanol were performed with a metal-bellows variable volumometer for temperatures between 310 and 363 K at pressures from the vapor pressure to 200 MPa. The results cover the high-density region from 737 to 882 kg m–3. The experimental uncertainties (total errors) of temperature, pressure, and density were estimated to be no greater than 3 mK, 0.1 %, and 0.1 %, respectively. Measurements of saturated liquid density at temperatures of 310, 340, and 360 K are also reported.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A. 相似文献
83.
To study the effect of binder distribution in a powder granule on the internal structure of the compacts, the internal structure of green bodies with various PVA contents was examined by a liquid immersion technique and SEM. By the liquid immersion technique, a dark three-dimensional network was found in the as-compacted green bodies, but disappeared after binder removal. This result shows that the structure corresponds to binder-rich surface layer of the spray-dried granule. Detailed examination on green bodies after the binder removal showed that the low density region was present at the boundaries of granules and was related to the binder-rich region. The voids between granules increase with increasing the PVA content. 相似文献
84.
Keizo Uematsu Masaki Takagi Tsunehiro Honda Nozomu Uchida Katsuichi Saito 《Journal of the American Ceramic Society》1989,72(8):1476-1478
Hydroxyapatite powder was synthesized and formed into a compact in an aqueous medium using a filter-cake method. The compact was hot isostatically pressed at 700° to 1000°C and 100 MPa for 2 h. Fully dense, transparent materials were obtained above 800°C. Both forming and densification methods were found to be important in obtaining transparent materials. 相似文献
85.
The densities for mixtures of R 22 and R 114 have been measured with the variable-volume method using a metal bellows as a function of temperature and pressure. The results for three different compositions (75, 50, and 25 mol% R 22) cover the high-density region along seven isotherms between 310 and 370 K at 15 pressures from 1.0 to 10 MPa. Based on the present density measurements, the values of the excess molar volume, the volume expansion coefficient, and the isothermal compressibility have been calculated. The excess molar volumes for each mixture below 340 K are positive, whereas those above 350 K decrease with decreasing pressure and become negative at low pressures. The behavior of the volume expansion coefficient and the isothermal compressibility for the equimolar mixture are closer to that for R 114 than the average of those for both pure components. 相似文献
86.
Hiroshi Numakura Tatsuru Watanabe Makoto Uchida Yoko Yamabe-Mitarai Eisuke Bannai 《Journal of Phase Equilibria and Diffusion》2006,27(6):638-643
The diffusion in iridium-rich Ir-Nb alloys has been studied by single-phase interdiffusion experiments. The chemical diffusion
coefficient has been measured for the primary fcc solid-solution and theL12 ordered compound Ir3Nb in the temperature range between 1650 and 1950 °C, using Ir/Ir-8Nb and Ir-26Nb/Ir-28Nb diffusion couples, respectively
(numbers indicate mol%). While the chemical diffusion coefficient in the solid-solution phase is close to the tracer self-diffusion
coefficient of pure iridium, the diffusion in the compound phase is extremely slow: the chemical diffusion coefficient is
1/40 to 1/50 of that in the solid solution. The low diffusion rate in the compound must be beneficial for high-temperature
performance of refractory superalloys based on the Ir-Nb system.
This article was presented at the Multicomponent-Multiphase Diffusion Symposium in Honor of Mysore A. Dayananda, which was
held during TMS 2006, 135th Annual Meeting and Exhibition, March 12–16, 2006, in San Antonio, TX. The symposium was organized
by Yongho Sohn of University of Central Florida, Carelyn E. Campbell of National Institute of Standards and Technology, Richard
D. Sisson, Jr., of Worcester Polytechnic Institute, and John E. Morral of Ohio State University. 相似文献
87.
M. Akita M. Nakajima Y. Uematsu K. Tokaji T. Kojima 《Fatigue & Fracture of Engineering Materials & Structures》2014,37(11):1223-1231
This paper describes the fatigue properties of the beta titanium alloy 55Ti–30Nb–10Ta–5Zr, generally referred to as ‘Gum Metal’. Rotating bending fatigue tests have been performed in laboratory air and in a 3% NaCl aqueous solution. The results obtained were compared with those of a conventional beta titanium alloy, Ti–22V–4Al. In tensile tests, 55Ti–30Nb–10Ta–5Zr indicated elasticity and microplasticity in the elastic region. Thus, the elastic modulus slightly decreased with an increasing strain, and the work hardening was minimal during plastic deformation. The mechanical properties of both of the alloys were comparable. The fatigue strength of 55Ti–30Nb–10Ta–5Zr in laboratory air was higher than that of Ti–22V–4Al, which could be attributed to the higher fatigue crack initiation resistance of 55Ti–30Nb–10Ta–5Zr than Ti–22V–4Al, while the resistance to small fatigue crack growth was similar. The fatigue strength of 55Ti–30Nb–10Ta–5Zr in laboratory air and in the 3% NaCl aqueous solution was analogous. In addition, corrosion pits were not observed in the run‐out specimen in the 3% NaCl aqueous solution, indicating a high resistance of 55Ti–30Nb–10Ta–5Zr against corrosion fatigue. 相似文献
88.
Yoko Akutsu Kosuke Tanaka Masahiko Osaka 《Journal of Nuclear Science and Technology》2015,52(10):1281-1284
The effects of impurity Zr on dissolution behavior into nitric acid of sintered Mo pellets were investigated using simulated fuels to accumulate basic data and knowledge concerning the matrix of Mo-cermet fuels. Mo pellets containing 1– 10 mol% Zr were prepared by conventional powder metallurgical route. After characterization tests using optical microscopy (OM), X-ray diffraction and secondary electron microscopy-energy dispersive X-ray spectrometry (EDX), the sintered pellets were subjected to dissolution tests by nitric acid. The apparent dissolution rate of Mo pellets containing impurity Zr was found to be followed by the first-order chemical reaction form, which is generally known as a simple chemical reaction. The rate of dissolution of sintered Mo-cermet fuels by nitric acid was found to decrease with the increase of the amount of impurity Zr. 相似文献
89.
T. Uematsu K. Tsutsui Y. Yazawa T. Warabisako I. Araki Y. Eguchi T. Joge 《Solar Energy Materials & Solar Cells》2003,75(3-4):557-566
Bifacial cells have been developed for use in flat-plate static-concentrator modules and bifacial photovoltaic modules. All but one of the fabrication processes are conventional mass production processes, making it possible to produce these cells at low cost. By using 12.5×12.5 cm SOG wafers, bifacial cells with about 15% front- and 10.5% rear-illumination efficiencies have already been developed, and cells achieving higher efficiencies for both surfaces are being developed now. By applying these cells, a bifacial-cell-type flat-plate static-concentrator module showed 82% optical-collection efficiency for normal-incident light with a 2.0 concentration ratio. We have also applied bifacial cells for non-concentrating bifacial modules and developed a new application that reduces the limitations on PV module installation. 相似文献
90.
Zhuang Y Ahn S Seyfferth AL Masue-Slowey Y Fendorf S Luthy RG 《Environmental science & technology》2011,45(11):4896-4903
Nanoscale zerovalent iron particles (nZVI), bimetallic nanoparticles (nZVI/Pd), and nZVI/Pd impregnated activated carbon (nZVI/Pd-AC) composite particles were synthesized and investigated for their effectiveness to remove polybrominated diphenyl ethers (PBDEs) and/or polychlorinated biphenyls (PCBs). Palladization of nZVI promoted the dehalogenation kinetics for mono- to tri-BDEs and 2,3,4-trichlorobiphenyl (PCB 21). Compared to nZVI, the iron-normalized rate constants for nZVI/Pd were about 2-, 3-, and 4-orders of magnitude greater for tri-, di-, and mono-BDEs, respectively, with diphenyl ether as a main reaction product. The reaction kinetics and pathways suggest an H-atom transfer mechanism. The reaction pathways with nZVI/Pd favor preferential removal of para-halogens on PBDEs and PCBs. X-ray fluorescence mapping of nZVI/Pd-AC showed that Pd mainly deposits on the outer part of particles, while Fe was present throughout the activated carbon particles. While BDE 21 was sorbed onto activated carbon composites quickly, debromination was slower compared to reaction with freely dispersed nZVI/Pd. Our XPS and chemical data suggest about 7% of the total iron within the activated carbon was zerovalent, which shows the difficulty with in-situ synthesis of a significant fraction of zerovalent iron in the microporous material. Related factors that likely hinder the reaction with nZVI/Pd-AC are the heterogeneous distribution of nZVI and Pd on activated carbon and/or immobilization of hydrophobic organic contaminants at the adsorption sites thereby inhibiting contact with nZVI. 相似文献