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991.
The structural stability and Young's modulus of single crystalline ZnO nanotubes are investigated using atomistic simulations. Unlike the case for conventional layered nanotubes, the energetic stability of single crystalline ZnO nanotubes is related to the wall thickness. The potential energy of ZnO nanotubes with fixed outer and inner diameters decreases with increasing wall thickness, while the nanotubes with the same wall thickness are independent of the outer and inner diameters. The transformation of single crystalline ZnO nanotubes with a double layer from wurtzite phase to graphitic phase suggests the possibility of wall-typed ZnO nanotubes. The size-dependent Young's modulus of ZnO nanotubes is also investigated. The wall thickness plays a significant role in the Young's modulus of single crystalline ZnO nanotubes, whereas the variation of outer and inner diameters slightly affects the Young's modulus of nanotubes with same wall thickness. 相似文献
992.
Lee TS Park KK Cho HS Choo YA Hwang M 《Journal of materials science. Materials in medicine》2008,19(3):1425-1431
Vascular smooth muscle cells (VSMCs) play a pivotal role in vascular injury through proliferation and migration. Pro-inflammatory
cytokines and cyclooxygenase (COX)-2 and nitric oxide synthase (NOS) are highly associated with the pathogenesis of VSMCs.
We investigated the effect of bioactive ceramics on the expression of inflammatory cytokines, COX-2, and inducible NOS (iNOS)
induced by phorbol 12-myristate 13-acetate (PMA) in rat VSMCs. The ceramics inhibited mRNA expression of IL-1β, TNF-α, IL-6,
COX-2, and iNOS. Prostaglandin release was also diminished by the ceramics. The bioactive ceramics effect on cytokines, COX-2,
and iNOS expression was achieved by inhibition of NF-κB activity. Interestingly, the ceramics-induced up-regulation of expression
of endothelial NOS resulted in an increase of nitric oxide production. Thus, bioactive ceramics may have dual effects on the
pathogenesis of VSMCs by regulation of NF-κB activity and NO production. 相似文献
993.
Baerlocher C Xie D McCusker LB Hwang SJ Chan IY Ong K Burton AW Zones SI 《Nature materials》2008,7(8):631-635
Physico-chemical characterization of the high-silica zeolite catalyst SSZ-74 (ref. 1) suggested that it, like the related materials TNU-9 (ref. 2) and IM-5 (ref. 3), has a multidimensional 10-ring channel system. Such pore systems are ideal for many petrochemical applications, and indeed SSZ-74 has been shown to be a good catalyst for a wide variety of reactions. The elucidation of its framework structure, however, proved to be difficult. Comparable problems were encountered with TNU-9 and IM-5, which were synthesized with related structure-directing agents. Their framework structures, which are the two most complex ones known, both have 24 Si atoms in the asymmetric unit, and were finally solved by combining high-resolution powder diffraction data with information derived from high-resolution electron microscopy images. Therefore, a similar approach, using the powder charge-flipping algorithm to combine the two types of data and molecular modelling to help to locate the structure-directing agent, was applied to SSZ-74. This procedure eventually revealed a most unusual 23-Si-atom framework structure (|(C(16)H(34)N(2))(4)&Si(92)(4)O(184)(OH)(8)]) with ordered Si vacancies. 相似文献
994.
Wood Jeffrey J.; Chiu Angela W.; Hwang Wei-Chin; Jacobs Jeffrey; Ifekwunigwe Muriel 《Canadian Metallurgical Quarterly》2008,23(4):515
Mexican American students are the fastest growing group in U.S. public schools. There is a growing body of research indicating that Mexican American families underutilize mental health services and are more likely to drop out of care prematurely when they do seek help. These findings may indicate that our health care system is not providing ethnic minorities with culturally competent care. Although cognitive?behavioral interventions are considered to be evidence-based treatments for child anxiety disorders, previous protocols have not taken cultural factors into account. This article discusses how to adapt cognitive?behavioral therapy (CBT) for Mexican American students with anxiety disorders. Working within the Psychotherapy Adaptation and Modification Framework (PAMF), this article offers adaptation principles that may guide school psychologists in implementing CBT strategies when working with Mexican American youth and their families. A case study is provided illustrating how cultural modifications of CBT can lead to positive outcomes for Mexican American students. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
995.
A novel curved computational integral imaging reconstruction (C-CIIR) technique for the virtually curved integral imaging (VCII) system is proposed, and its performances are analyzed. In the C-CIIR model, an additional virtual large-aperture lens is included to provide a multidirectional curving effect in the reconstruction process, and its effect is analyzed in detail by using the ABCD matrix. With this method, resolution-enhanced 3D object images can be computationally reconstructed from the picked-up elemental images of the VCII system. To confirm the feasibility of the proposed model, some experiments are carried out. Experiments revealed that the sampling rate in the VCII system could be kept at a maximum value within some range of the distance z, whereas in the conventional integral imaging system it linearly decreased as the distance z increased. It is also shown that resolutions of the object images reconstructed by the C-CIIR method have been significantly improved compared with those of the conventional CIIR method. 相似文献
996.
Sung Chul Kim Min Soo Kim In Chul Hwang Tae Won Lim 《International Journal of Refrigeration》2007,30(7):1215-1226
A CO2 heat pump system using recovered heat from the stack coolant was provided for use in fuel cell vehicles, where the high temperature heat source like in internal combustion engine vehicles is not available. The refrigerant loop consists of an electric drive compressor, a cabin heater, an outdoor evaporator, an internal heat exchanger, an expansion valve and an accumulator. The performance characteristics of the heat pump system were investigated and analyzed by experiments. The results of heating experiments were discussed for the purpose of the development and efficiency improvement of a CO2 heat pump system, when recovering stack exhaust heat in fuel cell vehicles. A heater core using stack coolant was placed upstream of a cabin heater to preheat incoming air to the cabin heater. The performance of the heat pump system with heater core was compared with that of the conventional heating system with heater core and that of the heat pump system without heater core, and the heat pump system with heater core showed the best performance of the selected heating systems. Furthermore, the coolant to air heat pump system with heater core showed a significantly better performance than the air to air heat pump system with heater core. 相似文献
997.
Yunho Hwang Dae-Hyun Jin Reinhard Radermacher 《International Journal of Refrigeration》2007,30(4):633-641
To help provide a clear understanding of the relative performance potential of HFCs (R-404A and R-410A) as compared to R-290 for walk-in refrigeration systems representing direct expansion commercial refrigeration systems with small charge, an experimental evaluation of the three refrigerants was investigated. To compare the environmental impact of refrigerants over the entire life cycle of fluid and equipment, including power consumption, the life cycle climate performance (LCCP) of the three refrigerants were evaluated based on measured data. The estimated LCCPs at various emission rates indicate that the LCCP of R-290 is always lower than that of R-404A. The LCCP of R-410A is lower than that of R-290 as long as the annual emission is kept below 10%. It was concluded that R-410A has less or equivalent environmental impact as compared to R-290 when safety (toxicity and flammability), environmental impact (climate change), cost and performance (capacity and COP) are considered. 相似文献
998.
Novel SnO(2)-In(2)O(3) heterostructured nanowires were produced via a thermal evaporation method, and their possible nucleation/growth mechanism is proposed. We found that the electronic conductivity of the individual SnO(2)-In(2)O(3) nanowires was 2 orders of magnitude better than that of the pure SnO(2) nanowires, due to the formation of Sn-doped In(2)O(3) caused by the incorporation of Sn into the In(2)O(3) lattice during the nucleation and growth of the In(2)O(3) shell nanostructures. This provides the SnO(2)-In(2)O(3) nanowires with an outstanding lithium storage capacity, making them suitable for promising Li ion battery electrodes. 相似文献
999.
Park C Lee S Choi M Kang M Jung Y Hwang S Ahn D Lee J Song C 《Journal of nanoscience and nanotechnology》2007,7(11):4150-4153
We report the fabrication and characterization of poly-Si nanowire transistors on flexible substrates. The nanowire transistors are fabricated on a SiO2/Si substrate using conventional CMOS processes, and then they are transferred onto polyimide substrates. The transfer process is performed by spin-coating of polyimide, curing (annealing) of the polyimide layer, and removal of the SiO2 sacrificial layer. The optimized curing condition results in the maximum bending of 150 degrees with full recovery. The nanowire transistors exhibit transistor characteristics as a function of the backgate bias. Our new process can be applied to the fabrication of Si-nanowire transistors with larger mobilities. 相似文献
1000.
Kim TW Lee SH Hwang SJ Hyun SH Choy JH 《Journal of nanoscience and nanotechnology》2007,7(11):3857-3861
Nanostructured Mn(1-x-y)Co(x)Ni(y)O2 metal oxides are synthesized by one-pot hydrothermal reaction at low temperature. From powder X-ray diffraction and field emission-scanning electron microscopic analyses, it is found that the crystal structure and crystal morphology of the present materials are tunable by the control of the composition of precursor. 1D nanowires with alpha-MnO2-type structure are prepared with low substitution rate of Co and Ni, while the increase of substituent contents leads to the formation of delta-MnO2-structured 3D nanospheres consisting of 2D nanoplates. According to X-ray absorption near edge spectroscopy and chemical analyses, mixed valent Co(III)/Co(IV) and divalent Ni(II) ions are stabilized in the octahedral Mn sites of alpha-MnO2- and delta-MnO2-structures. The electrochemical measurements clearly demonstrate that the present nanostructured materials show promising electrode performances for lithium secondary batteries. 相似文献