全文获取类型
收费全文 | 1460篇 |
免费 | 25篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 87篇 |
综合类 | 6篇 |
化学工业 | 240篇 |
金属工艺 | 53篇 |
机械仪表 | 22篇 |
建筑科学 | 52篇 |
能源动力 | 48篇 |
轻工业 | 63篇 |
水利工程 | 27篇 |
石油天然气 | 3篇 |
无线电 | 150篇 |
一般工业技术 | 217篇 |
冶金工业 | 408篇 |
原子能技术 | 26篇 |
自动化技术 | 96篇 |
出版年
2022年 | 12篇 |
2021年 | 14篇 |
2020年 | 9篇 |
2019年 | 15篇 |
2018年 | 15篇 |
2017年 | 12篇 |
2016年 | 15篇 |
2015年 | 19篇 |
2014年 | 16篇 |
2013年 | 48篇 |
2012年 | 39篇 |
2011年 | 68篇 |
2010年 | 27篇 |
2009年 | 71篇 |
2008年 | 67篇 |
2007年 | 43篇 |
2006年 | 41篇 |
2005年 | 48篇 |
2004年 | 43篇 |
2003年 | 44篇 |
2002年 | 32篇 |
2001年 | 44篇 |
2000年 | 40篇 |
1999年 | 35篇 |
1998年 | 126篇 |
1997年 | 102篇 |
1996年 | 53篇 |
1995年 | 41篇 |
1994年 | 31篇 |
1993年 | 32篇 |
1992年 | 16篇 |
1991年 | 21篇 |
1990年 | 10篇 |
1989年 | 18篇 |
1988年 | 21篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 16篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 11篇 |
1981年 | 18篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 23篇 |
1973年 | 5篇 |
1972年 | 11篇 |
1971年 | 4篇 |
排序方式: 共有1498条查询结果,搜索用时 31 毫秒
71.
A coterie is a set of subsets (called quorums) of the processes in a distributed system such that any two quorums intersect with each other and is mainly used to solve the mutual exclusion problem in a quorum-based algorithm. The choice of a coterie sensitively affects the performance of the algorithm and it is known that nondominated (ND) coteries achieve good performance in terms of criteria such as availability and load. On the other hand, grid coteries have some other attractive features: 1) a quorum size is small, which implies a low message complexity, and 2) a quorum is constructible on the fly, which benefits a low space complexity. However, they are not ND coteries unfortunately. To construct ND coteries having the favorite features of grid coteries, we introduce the transversal merge operation that transforms a dominated coterie into an ND coterie and apply it to grid coteries. We call the constructed ND coteries ND grid coteries. These ND grid coteries have availability higher than the original ones, inheriting the above desirable features from them. To demonstrate this fact, we then investigate their quorum size, load, and availability, and propose a dynamic quorum construction algorithm for an ND grid coterie. 相似文献
72.
Shigeki Harada Akihiko Iwata Heiju Uchiike 《Journal of the Society for Information Display》2005,13(6):537-543
Abstract— In order to lower development costs and to shorten development time, small panels, under 10‐in on the diagonal, are used for the experiments to improve the luminous efficiency of plasma‐display panels. However, it is difficult to show the same results as those of large panels, over 40 in. on the diagonal. In this paper, first, we show that the luminous efficiency and the voltage margin of mini‐panels are not obtained with large panels by using an actual 46‐in. PDP. The reason is that the resistance in the large panels is larger than that in the mini panels and the voltage drop in the large panels are larger than in mini‐panels. Therefore, we conclude that the bus electrode width and the transparent electrode width are important factors in the design of large PDPs. Next, we show the technique of designing large panels by using a database obtained from mini‐panels. The estimated cell‐design results show good agreement with an actual 46‐in. PDP in luminous efficiency and minimum sustain voltage. We show that a desired large PDP can be obtained by using the cell design proposed in the present paper. 相似文献
73.
Ryosuke Ueyama Masahiro Harada Tamotu Ueyama Takashi Yamamoto Tadashi Shiosaki Kiyoshi Kuribayashi Kunihito Koumoto Won Son Seo 《Journal of Materials Science: Materials in Electronics》2000,11(2):139-143
Ultrafine BaTiO3 particles were prepared by a micro-emulsion charring (MEC) method. The MEC method consisted of two steps. The first step is the preparation of a water/oil micro-emulsion with BaTiO3 elements, and the second is a low temperature firing process in N2 atmosphere, which includes charring of oil in an emulsion and powdering BaTiO3 particles with the char. The char formed around BaTiO3 particles prevents an agglomeration of BaTiO3 particles during firing. In the present experiment, the W/O ratio and the amount of emulsifier greatly influenced the size of droplets of the emulsion. The charring temperature was another important experimental factor in order to obtain the desired BaTiO3 particles. The finally obtained BaTiO3 charring powders were monodispersed spherical particles and the particle size was 0.1 m to 0.5 m. 相似文献
74.
A chromatographic determination method was developed for the absolute configuration of an acyclic secondary alcohol using the characteristic functions of 1,5-difluoro-2,4-dinitrobenzene (FFDNB). This method relies on the formation of the fixed favorable conformation of a secondary alcohol-DLA (2,4-dinitrophenyl-5-leucinamide) derivative and its recognition by ODS silica gel. The secondary alcohol reacted first with FFDNB under mild basic conditions, and L-leucinamide or DL-leucinamide was then introduced into the secondary alcohol-FDNB derivative. Because the conformations of the resulting alcohol-DLA derivatives were rigidly fixed by the dinitrobenzene plane, the absolute configuration at the asymmetric carbon of the secondary alcohol tested can be definitely deduced by the elution behavior of both of the diastereomers in the HPLC and/or LC/MS. One of the diastereomers has the cis (Z)-type arrangement of two more hydrophobic substituents of the alcohol and leucinamide moieties, the more hydrophobic side chain and isobutyl groups, to the plane of the dinitrobenzene, whereas another diastereomer has the opposite arrangement (trans (E)-type). Therefore, the cis arrangement interacts more strongly with the ODS silica gel and has a longer retention time than that of the trans-type arrangement. This established method was successfully applied to various chiral acyclic secondary alcohols including chloramphenicol and 4-hydroxyphenyllactic acid. Finally, the limitations of this method were also examined. 相似文献
75.
Optimum design of a grazing-incidence flat-field spectrograph with a spherical varied-line-space grating 总被引:1,自引:0,他引:1
A grazing-incidence spectrograph is designed by use of the flat-field image-focusing property of a spherical varied-line-space grating. Optimum grating parameters for mechanical ruling are selected by application of genetic algorithms. Two gratings, one for 2-5-nm and the other for 5-20-nm spectral regions, are designed, and their fabrication tolerances are analyzed. 相似文献
76.
Masayuki Fujii Kazuyuki Tohyama Tetsuro Tokoro Masamitsu Kosaki Yuji Muramoto Naohiro Hozumi Masayuki Nagao 《Electrical Engineering in Japan》2002,141(2):8-16
Polymer materials have excellent dielectric and insulation properties; however, those properties in AC high field region have not been known well. Recently we established an evaluation method of high‐field AC dissipation current waveform of polymer materials 1 . AC dissipation current waveforms of polyethylene and polypropylene films show nonlinear distortion in AC high‐field region. This nonlinearity was thought to be related to the behavior of AC space charge formation in the sample near electrodes. The properties of space charge formed under AC high field at power frequency seem to differ from those formed under DC high field. The measurement of AC space charge distribution is not so easy due to the resolution limit of the space charge measurement. We studied the dielectric properties of biaxially oriented polypropylene (BOPP) film under AC high field up to 120 °C. It was found that tan δ, AC dissipation current (Ixr), and unbalanced component of capacitive current (ΔIxc) increased when the temperature became higher. In particular, ΔIxc increased above some threshold field and was considered to be due to the AC space charge formation. This AC space charge layer near electrode is thought to be formed due to carrier injection under AC high‐field application. Usually, the carrier mobility becomes smaller on lowering the temperature. Most of the carriers injected from the electrode are trapped near the electrode in the sample film. But in the high‐temperature region, the carrier mobility becomes larger and the carrier injection starts to increase from lower field. Many more carriers are injected from the electrode. It is thought that some of the injected carriers are trapped inside the sample film; the others go through the sample to the opposite side. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 8–16, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10018 相似文献
77.
H Harada T Hirata J Utoh R Kunitomo M Hara N Kitamura 《Canadian Metallurgical Quarterly》1998,46(7):629-633
OBJECTIVE: The prevalence of obesity and thinness is unknown among Iranian high-school age girls. We determined the prevalence of overweight and underweight among Iranian high-school girls from Kerman (south-east province of Iran). DESIGN: A cross-sectional study of indicative cluster sample. MEASUREMENTS: Weight, height, body mass index (BMI), chest, waist, abdomen, hip and thigh circumference of 1000 Iranian high-school girls aged 14-21 y (mean (standard deviation, s.d.) 16.2 (1.3)) were measured. The criteria for very underweight, underweight, desirable weight, grade 1, 2 and 3 overweight used in the present study were: BMI in kg/m2 < 15, 15-19.9, 20-24.9, 25-29.9, 30-39.9 and > or = 40, respectively. RESULTS: 4.6% (95% confidence interval (CI): 3.4%-6.1%) were grade 1 overweight (BMI = 25.0-29.9), 0.7% (95% CI: 0.3%-1.4%) were grade 2 overweight (BMI = 30-39.9), and none were grade 3 overweight (BMI > or = 40), while 54.6% (95% CI: 51.5%-57.7%) were underweight (BMI = 15-19.9) and 1.6% (95% CI: 0.9%-2.6%) were very underweight (BMI < 15). The mean (s.d.) BMI was 19.8 (2.9) (95% CI: 19.6-20.0). The mean (s.d.) waist-to-hip ratio (WHR), abdomen-to-hip ratio and chest-to-hip ratio values were 0.8 (0.06) (95% CI: 0.8-0.81), 0.8 (0.07) (95% CI: 0.8-0.81) and 0.9 (0.07) (95% CI: 0.9-0.91), respectively, in this sample. CONCLUSION: The results suggest a low prevalence of overweight among Iranian young women. 相似文献
78.
The purpose of this study is to develop an approach for unified constitutive modeling based on experimentally determined back stress and overstress. Back stress and overstress were experimentally determined for Type 316 stainless steel at 600°C, by analyzing the unloading curve for the stress-strain response of cyclic strain tests. The result has indicated that the cyclic strain hardening behavior is mainly caused by hardening in the back stress. A phenomenological unified constitutive model in which the back stress and drag stress are taken as the internal state variables is proposed, and has been shown that this model is able to simulate the cyclic inelastic behavior. 相似文献
79.
80.
Using photomasks with the same resolution as for conventional transducers, it is shown that a 2-layer interdigital transducer doubles the operating frequency of acoustic-surface-wave devices, at the sacrifice of some increase in conversion loss. The origin of the increased loss is attributed to a geometrical factor and a dielectric loss in the insulating layer. 相似文献