全文获取类型
收费全文 | 6264篇 |
免费 | 322篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 86篇 |
综合类 | 10篇 |
化学工业 | 1291篇 |
金属工艺 | 184篇 |
机械仪表 | 316篇 |
建筑科学 | 123篇 |
矿业工程 | 2篇 |
能源动力 | 309篇 |
轻工业 | 576篇 |
水利工程 | 20篇 |
石油天然气 | 7篇 |
武器工业 | 1篇 |
无线电 | 1070篇 |
一般工业技术 | 1277篇 |
冶金工业 | 462篇 |
原子能技术 | 57篇 |
自动化技术 | 807篇 |
出版年
2024年 | 10篇 |
2023年 | 83篇 |
2022年 | 117篇 |
2021年 | 207篇 |
2020年 | 157篇 |
2019年 | 150篇 |
2018年 | 180篇 |
2017年 | 179篇 |
2016年 | 211篇 |
2015年 | 189篇 |
2014年 | 295篇 |
2013年 | 411篇 |
2012年 | 433篇 |
2011年 | 465篇 |
2010年 | 346篇 |
2009年 | 335篇 |
2008年 | 367篇 |
2007年 | 277篇 |
2006年 | 221篇 |
2005年 | 218篇 |
2004年 | 183篇 |
2003年 | 158篇 |
2002年 | 147篇 |
2001年 | 116篇 |
2000年 | 111篇 |
1999年 | 110篇 |
1998年 | 201篇 |
1997年 | 136篇 |
1996年 | 120篇 |
1995年 | 76篇 |
1994年 | 54篇 |
1993年 | 59篇 |
1992年 | 32篇 |
1991年 | 25篇 |
1990年 | 21篇 |
1989年 | 21篇 |
1988年 | 23篇 |
1987年 | 23篇 |
1986年 | 7篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 11篇 |
1978年 | 11篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1974年 | 7篇 |
1972年 | 6篇 |
排序方式: 共有6598条查询结果,搜索用时 0 毫秒
991.
Facile synthesis of highly faceted multioctahedral Pt nanocrystals through controlled overgrowth 总被引:1,自引:0,他引:1
Highly faceted Pt nanocrystals with a large number of interconnected arms in a quasi-octahedral shape were synthesized simply by reducing H2PtCl6 precursor with poly(vinyl pyrrolidone) in aqueous solutions containing a trace amount of FeCl3. The iron species (Fe(3+) or Fe(2+)) play a key role in inducing the formation of the multioctahedral structure by decreasing the concentration of Pt atoms and keeping a low concentration for the Pt seeds during the reaction. This condition favors the overgrowth of Pt seeds along their corners and thus the formation of multiarmed nanocrystals. Electron microscopy studies revealed that the multioctahedral Pt nanocrystals exhibit a large number of edge, corner, and surface step atoms. The size of the multioctahedral Pt nanocrystals can be controlled by varying the concentration of FeCl3 added to the reaction and/or the reaction temperature. These multioctahedral Pt nanocrystals were tested as electrocatalysts for the oxygen reduction reaction in a proton exchange membrane fuel cell and exhibited improved specific activity and durability compared to commercial Pt/C catalyst. 相似文献
992.
Pd-Pt core-shell nanoplates with hexagonal and triangular shapes were synthesized through the heterogeneous, epitaxial growth of Pt on Pd nanoplates. The Pd nanoplates were synthesized by reducing Na2PdCl4 precursor with PVP as a reducing agent, which then served as seeds for the nucleation of Pt atoms formed by reducing H2PtCl6 with citric acid. Characterization of the as-prepared Pd-Pt nanoplates by scanning transmission electron microscopy and high-resolution transmission electron microscopy reveals that a thin, uniform Pt shell was formed around the Pd nanoplate, demonstrating the layer-by-layer epitaxial growth of Pt on Pd surface in this approach. The close lattice match between Pd and Pt (lattice mismatch of only 0.77%) and the slow reduction rate associated with the mild reducing power of citric acid play key roles in achieving the epitaxial growth of Pt shells on Pd nanoplates. 相似文献
993.
How does the affective significance of emotional faces affect perceptual decisions? We manipulated affective significance by pairing 100% fearful faces with aversive electrical stimulation and hypothesized that increasing the significance of a stimulus via its prior history would lead to enhanced processing. After fear conditioning, participants viewed graded emotional faces that ranged from neutral to fearful. Faces were shown either in a color that was previously paired with shock or a color not paired with shock during conditioning. Increases in the frequency of "fearful" responses for faces shown in the shock-paired color were most robust for faces at intermediate intensity levels (40-60% fearful). Psychometric fits to the data revealed significant increased sensitivity for shock-paired relative to unpaired faces. Thus, despite identical physical features for shock-paired and unpaired stimuli (aside from the color, which was counterbalanced), more frequent (and faster) "fearful" responses were made when participants viewed affectively significant stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
994.
Zhang Yuxuan Tao Youkun Yu Zhouyang Lu Jiamei Lim Sung Yul Shao Jing 《Journal of Electroceramics》2020,45(1):29-38
Journal of Electroceramics - In this work, the structure and electrochemical properties of titanate ceramics with in situ Ni exsolution are investigated to identify the structure-performance... 相似文献
995.
Light Harvesting: Enhanced Light Harvesting in Mesoscopic Solar Cells by Multilevel Multiscale Patterned Photoelectrodes with Superpositioned Optical Properties (Adv. Funct. Mater. 36/2016) 下载免费PDF全文
996.
Understanding Origin of Voltage Hysteresis in Conversion Reaction for Na Rechargeable Batteries: The Case of Cobalt Oxides 下载免费PDF全文
Hyunchul Kim Hyungsub Kim Jinsoo Kim Gabin Yoon Kyungmi Lim Won‐Sub Yoon Kisuk Kang 《Advanced functional materials》2016,26(28):5042-5050
Conversion reaction electrodes offer a high specific capacity in rechargeable batteries by utilizing wider valence states of transition metals than conventional intercalation‐based electrodes and have thus been intensively studied in recent years as potential electrode materials for high‐energy‐density rechargeable batteries. However, several issues related to conversion reactions remain poorly understood, including the polarization or hysteresis during charge/discharge processes. Herein, Co3O4 in Na cells is taken as an example to understand the aforementioned properties. The large hysteresis in charge/discharge profiles is revealed to be due to different electrochemical reaction paths associated with respective charge and discharge processes, which is attributed to the mobility gap among inter‐diffusing species in a metal oxide compound during de/sodiation. Furthermore, a Co3O4–graphene nanoplatelet hybrid material is demonstrated to be a promising anode for Na rechargeable batteries, delivering a capacity of 756 mAh g?1 with a good reversibility and an energy density of 96 Wh kg?1 (based on the total electrode weight) when combined with a recently reported Na4Fe3(PO4)2(P2O7) cathode. 相似文献
997.
998.
In our earlier work, a multipoint diffraction strain sensor using a microlens array was developed for measurement of whole-field strains. The method is extended to a system with variable sensitivity and measurement range. In the present system, two collimated laser beams, 3 mm in diameter, symmetrically strike the grating attached to the specimen surface at prescribed angles. The diffracted wavefronts, magnified by a microscope objective, are sampled by a lenslet array with each microlens acting as an individual strain sensor. In-plane strain components over the full field can be measured by what is to our knowledge a new sensor with variable sensitivity by changing the distance from the microscope objective to the microlens array. Both a theoretical explanation and experimental verification are provided. 相似文献
999.
Small peptides with less than 1000 in molecular weight are not considered amenable to sandwich immunoassays due to their difficulty of simultaneous recognition by two antibodies. As an alternative, we attempted noncompetitive detection of small peptides by open sandwich enzyme-linked immunosorbent assay (OS-ELISA) utilizing the antigen-induced enhancement of antibody VH/VL interaction. Taking fragments of human osteocalcin (BGP), a major non-collagen peptide produced in bone, as model peptides, OS immunoassay was performed using the cloned VH and VL cDNAs from two anti-BGP monoclonal antibodies either recognizing the N- or C-terminal fragment, respectively. When the clones were used for OS-ELISA with immobilized VL fragment and phage-displayed VH fragment, enhanced VH/VL interaction upon BGP addition was observed. Especially the clone for the C-terminal fragment showed a superior detection limit as well as a wider working range than those of competitive assay. The result was reproduced with purified VH-alkaline phosphatase and MBP-VL fusion proteins, where the latter was directly immobilized onto the microplate wells. The minimum detectable fragment was the hexamer including the C-terminus. This simple approach with a single monoclonal antibody with a short measurement time may prove a useful tool in immunodiagnostics as well as in proteomics research. 相似文献
1000.
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