全文获取类型
收费全文 | 857篇 |
免费 | 22篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 39篇 |
综合类 | 1篇 |
化学工业 | 287篇 |
金属工艺 | 23篇 |
机械仪表 | 20篇 |
建筑科学 | 15篇 |
能源动力 | 38篇 |
轻工业 | 106篇 |
石油天然气 | 3篇 |
无线电 | 55篇 |
一般工业技术 | 177篇 |
冶金工业 | 30篇 |
原子能技术 | 22篇 |
自动化技术 | 65篇 |
出版年
2023年 | 4篇 |
2022年 | 14篇 |
2021年 | 19篇 |
2020年 | 13篇 |
2019年 | 10篇 |
2018年 | 13篇 |
2017年 | 11篇 |
2016年 | 20篇 |
2015年 | 20篇 |
2014年 | 22篇 |
2013年 | 50篇 |
2012年 | 40篇 |
2011年 | 53篇 |
2010年 | 38篇 |
2009年 | 36篇 |
2008年 | 55篇 |
2007年 | 48篇 |
2006年 | 38篇 |
2005年 | 32篇 |
2004年 | 25篇 |
2003年 | 30篇 |
2002年 | 20篇 |
2001年 | 15篇 |
2000年 | 10篇 |
1999年 | 21篇 |
1998年 | 15篇 |
1997年 | 17篇 |
1996年 | 13篇 |
1995年 | 14篇 |
1994年 | 9篇 |
1993年 | 23篇 |
1992年 | 9篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 12篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有881条查询结果,搜索用时 15 毫秒
31.
32.
Qiang Dong Nobuhiro Kumada Yoshinori Yonesaki Takahiro Takei Nobukazu Kinomura Dan Wang 《Journal of Materials Science》2010,45(20):5685-5691
Hollow hematite (α-Fe2O3) microspheres with an average diameter of 3-4 μm and a shell thickness of approximate 150 nm was synthesized by a simple
hydrothermal route using FeCl3·6H2O solution and acetic acid without using any templates. The hollow microspheres were composed of α-Fe2O3 nanoparticles with the diameter range from 20 to 40 nm. The effects of reaction parameters such as reaction time, temperature,
concentration of FeCl3·6H2O solution, and initial pH on the morphology of the final products were investigated. A possible formation mechanism of hollow
α-Fe2O3 microspheres was also proposed, where the acetic acid played a role of etching in the formation of hollow structure. 相似文献
33.
Sato S Miyoki S Ohashi M Fujimoto MK Yamazaki T Fukushima M Ueda A Ueda K Watanabe K Nakamura K Etoh K Kitajima N Ito K Kataoka I 《Applied optics》1999,38(13):2880-2885
Low-loss mirrors fabricated by ion-beam-sputtering machines for possible application in an interferometric gravitational wave antenna were evaluated by use of Nd:YAG laser light (lambda = 1064 nm) with two distinct measurements: a tabletop experiment that used a short cavity with a small beam with a beam waist of approximately 2w(0) = 0.82 mm, and an optical test that used a 20-m prototypical gravitational-wave detector with a large beam with a beam waist of approximately 2w(0) = 4.4 mm. A multilayer coating comprised 29 layers of SiO(2)/Ta(2)O(5) and one protective coating of SiO(2). The best values obtained as a result of these measurements were 16 ppm (parts in 10(6)) and 30 ppm in total loss, respectively. Also, a two-dimensional loss map generated by use of a small beam successfully revealed the existence of a loss structure within the coating surface. These results imply that a high-reflectance multilayer coating has some inhomogeneities and a loss distribution with a typical scale of a few millimeters and that the total measured losses depend on the beam spot size. 相似文献
34.
Yoshinori Suzuki Takashi Uchida Masataka Wakihara Masao Taniguchi 《Materials Research Bulletin》1981,16(9):1085-1090
Changing the partial pressure of sulfur Ps2 at temperatures of 750° and 950°C, phase equilibria on the Mo-S system by solid-gas reaction were investigated. Hexagonal 2H-MoS2 and monoclinic Mo2S3 phases were identified from the x-ray powder diffraction pattern. The 2H-MoS2 had a slight homogeneity range, i.e. MoS1.978 to MoS2.0 at 950°C, MoS1.983 to MoS2.0 at 750°C. No remarkable variation of lattice parameters for the MoS2 was observed. The composition of the Mo2S3 phase was not stoichiometric MoS1.5 but MoS1.457 at 950°C. At 750°C the composition of the Mo2S3 phase could not be determined since it was quite difficult to establish the equilibrium state between the gas and the condensed phases. This finding agreed well with the result of Morimoto and Kullerud. 相似文献
35.
DNA-DNA hybridization is known as the superior method in the elucidation of relationships between closely related taxa, such as species and strain. For species determination we propose a new DNA-DNA hybridization method: the DNA microarray-based comparative genomic hybridization (CGH) method, using a yeast DNA microarray with approximately 6000 genes. The genome from a yeast strain as a sample strain (Sample) was labelled with Cy3-dye and hybridized to a single DNA microarray, together with the Cy5-labelled genome of S. cerevisiae S288C as a reference strain (Reference). The log2 ratio values [log2[Cy3(Sample)/Cy5(Reference)]: Ratio] of signal intensities of all the gene spots were estimated and divided into the following groups: Ratio < or = -1; -1 < Ratio < 1; 1 < or = Ratio. The hybridization profiles of the genomes of type strains belonging to the genus Saccharomyces were significantly different from that of S. cerevisiae S288C. The Ratio-based grouping allowed us to discriminate between some species from S. cerevisiae more clearly. Furthermore, cluster analysis discriminated between closely related species and strains. Using this method, we were able to not only perform species determination but also to obtain information on alternation in gene copy number of such gene amplifications and deletions with single-gene resolution. These observations indicated that DNA microarray-based CGH is a powerful system for species determination and comparative genome analysis. 相似文献
36.
A new beta-agarase was purified from an agarolytic bacterium, Bacillus sp. MK03. The enzyme was purified 129-fold from the culture supernatant by ammonium sulfate precipitation, anion exchange and gel filtration column chromatographic methods. The purified enzyme appeared as a single band on sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Estimation of the molecular mass by SDS-PAGE and gel filtration gave values of 92 kDa and 113 kDa, respectively. The N-terminal amino acid sequence of the enzyme showed no homology to those of other known agarases. The optimum pH and temperature for this enzyme were 7.6 and 40 degrees C, respectively. The predominant hydrolysis product of agarose by this enzyme was neoagarotetraose, indicating the cleavage of beta-1,4 linkage. This enzyme could hydrolyze neoagarohexaose to produce neoagarotetraose and neoagarobiose; it could not hydrolyze these products. The enzyme digested agarose by endo-type hydrolysis. 相似文献
37.
高灰熔点煤高温下煤焦CO2/水蒸汽气化反应特性的实验研究 总被引:1,自引:2,他引:1
我国煤炭年产量中,1400℃以上的高灰熔点煤约占50%以上。为探索固态排渣方式的高灰熔点煤气流床气化,本文选出具有代表性的三种高灰熔点煤种和一种低灰熔点煤种,在TGA-51H型高温热天平上进行了煤焦-CO2和煤焦-水蒸汽气化反应特性的实验研究,并利用SEM考察了气化条件下煤焦及灰的微观结构。实验结果表明:在煤焦-CO2、H2O反应过程中,反应速度明显表现出高温区域的扩散反应和低温区域的化学反应;无论在1273K~1573K的低温区域,还是在高于1573K的高温区域,反应速率随燃料比(FC/V)的增加而减小。 相似文献
38.
Shuang Bai Tetsuya Matsumoto Yoshinori Takeuchi Hiroaki Kudo Noboru Ohnishi 《Machine Vision and Applications》2013,24(5):959-970
In image classification based on bag of visual words framework, image patches used for creating image representations affect the classification performance significantly. However, currently, patches are sampled mainly based on processing low-level image information or just extracted regularly or randomly. These methods are not effective, because patches extracted through these approaches are not necessarily discriminative for image categorization. In this paper, we propose to utilize both bottom-up information through processing low-level image information and top-down information through exploring statistical properties of training image grids to extract image patches. In the proposed work, an input image is divided into regular grids, each of which is evaluated based on its bottom-up information and/or top-down information. Subsequently, every grid is assigned a saliency value based on its evaluation result, so that a saliency map can be created for the image. Finally, patch sampling from the input image is performed on the basis of the obtained saliency map. Furthermore, we propose a method to fuse these two kinds of information. The proposed methods are evaluated on both object categories and scene categories. Experiment results demonstrate their effectiveness. 相似文献
39.
The effect of nine transition elements on the morphology, distribution and composition of MC carbides (MCs) in a nickel-base
superalloy, IN-100, was investigated by differential thermal analysis (DTA), microstructural observation and X-ray microanalysis.
The doping with tantalum, tungsten and molybdenum caused a significant change in the morphology and distribution of MCs as
well as the profile of DTA curve of IN-100. The compositions of the MC in IN-100 were TiC and (Ti0.80Mo0.17V0.03) C, and the doping with niobium, tantalum and tungsten changed significantly the composition of MC. On the other hand, the
doping with chromium, vanadium, hafnium and zirconium scarcely changed the composition. In addition to TiC and (Ti, Mo, V)
C, zirconium- and hafnium-rich MCs were found in the zirconium- and hafnium-doped alloys, respectively. The effect of the
dopants on the composition of MCs could be explained by a relationship between the metallic radius and the free energy of
formation for the MC. 相似文献
40.
Mikio Enoeda Hisashi Tanigawa Takanori Hirose Satoshi Suzuki Kentaro Ochiai Chikara Konno Yoshinori Kawamura Toshihiko Yamanishi Tsuyoshi Hoshino Masaru Nakamichi Hiroyasu Tanigawa Koichiro Ezato Yohji Seki Akira Yoshikawa Daigo Tsuru Masato Akiba 《Fusion Engineering and Design》2012,87(7-8):1363-1369
The development of a Water Cooled Ceramic Breeder (WCCB) Test Blanket Module (TBM) is being performed as one of the most important steps toward DEMO blanket in Japan. For the TBM testing and evaluation toward DEMO blanket, the module fabrication technology development by a candidate structural material, reduced activation martensitic/ferritic steel, F82H, is one of the most critical items from the viewpoint of realization of TBM testing in ITER. In Japan, fabrication of a real scale first wall, side walls, a breeder pebble bed box and assembling of the first wall and side walls have succeeded. Recently, the real scale partial mockup of the back wall was fabricated. The fabrication procedure of the back wall, whose thickness is up to 90 mm, was confirmed toward the fabrication of the real scale back wall by F82H. Important key technologies are almost clarified for the fabrication of the real scale TBM module mockup. From the view point of testing and evaluation, development of the technology of the blanket tritium recovery, development of advanced breeder and multiplier pebbles and the development of the blanket neutronics measurement technology are also performed. Also, tritium production and recovery test using D-T neutron in the Fusion Neutronics Source (FNS) facility has been started as the verification test of tritium production performance. This paper overviews the recent achievements of the development of the WCCB TBM in Japan. 相似文献