全文获取类型
收费全文 | 932篇 |
免费 | 55篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 80篇 |
综合类 | 4篇 |
化学工业 | 251篇 |
金属工艺 | 23篇 |
机械仪表 | 27篇 |
建筑科学 | 21篇 |
能源动力 | 62篇 |
轻工业 | 76篇 |
水利工程 | 3篇 |
无线电 | 77篇 |
一般工业技术 | 208篇 |
冶金工业 | 25篇 |
原子能技术 | 52篇 |
自动化技术 | 80篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 16篇 |
2021年 | 23篇 |
2020年 | 13篇 |
2019年 | 9篇 |
2018年 | 27篇 |
2017年 | 30篇 |
2016年 | 25篇 |
2015年 | 23篇 |
2014年 | 25篇 |
2013年 | 64篇 |
2012年 | 63篇 |
2011年 | 82篇 |
2010年 | 62篇 |
2009年 | 38篇 |
2008年 | 58篇 |
2007年 | 50篇 |
2006年 | 35篇 |
2005年 | 36篇 |
2004年 | 31篇 |
2003年 | 33篇 |
2002年 | 25篇 |
2001年 | 13篇 |
2000年 | 13篇 |
1999年 | 18篇 |
1998年 | 11篇 |
1997年 | 18篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 13篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1974年 | 1篇 |
排序方式: 共有989条查询结果,搜索用时 15 毫秒
51.
Katsumi Yoshino Tsuyoshi Demura Masaki Kawahigashi Yoshitsugu Miyashita Kiyoshi Kurahashi Yoshiji Matsuda 《Electrical Engineering in Japan》2004,146(1):18-26
Cross‐linked polyethylene (XLPE) has been widely adopted as insulating material for high‐voltage power cables up to 500 kV. Further improvement of electrical and thermal properties on insulating material is required in order to increase cable operation efficiency. Therefore, the development of novel insulating material possessing high thermal properties will be necessary. Recent progress of catalysis technology contributes to obtain new polymeric materials which may be applied to electrical insulation. The authors investigated the basic properties of newly developed stereoregular syndiotactic polypropylene (s‐PP) which is synthesized with homogeneous metallocene catalyst. Though recycling of cross‐linked polymers such as conventionally used XLPE may be difficult because of their poor heat deformation, the s‐PP which is not cross‐linked must be suitable for recycling. A series of experiments on its physical and electrical properties gave the following results.
- (1) s‐PP has sufficient flexibility compared with isotactic polypropylene (i‐PP ).
- (2) Both AC and lightning impulse breakdown strength of s‐PP in spite of no cross‐linking are superior to those of XLPE in the temperature range from 25 to 90 °C.
- (3) Degradation by copper of s‐PP is less than that of i‐PP.
- (4) s‐PP/VLDPE blend shows sufficient brittleness temperature for use.
52.
Sugio T Inoue T Kitano Y Takeuchi F Kamimura K 《Journal of Bioscience and Bioengineering》2004,98(2):85-91
A mesophilic, mixotrophic iron-oxidizing bacterium strain OKM-9 uses ferrous iron as a sole source of energy and L-glutamate as a sole source of cellular carbon. Uptake of L-glutamate into OKM-9 cells is absolutely dependent on ferrous iron oxidation. Thus, the Fe(2+)-dependent L-glutamate uptake system of strain OKM-9 is crucial for the bacterium to grow mixotrophically in iron medium with L-glutamate. The relationship between iron oxidation and L-glutamate transport activities was studied. Iron oxidase containing cytochrome a was purified 9-fold from the plasma membrane of OKM-9. A purified iron oxidase showed one rust-colored band following disc gel electrophoresis after incubation with Fe(2+). The Fe(2+)-dependent L-glutamate transport system was also purified 14.5-fold from the plasma membrane using the same purification steps as for iron oxidase. Fe(2+)-dependent L-glutamate and L-cysteine uptake activities of OKM-9 were 0.36 and 0.24 nmol/mg/min, respectively, when a concentration of 18 mM of these amino acids was used as a substrate. Both uptake activities were completely inhibited by potassium cyanide (KCN), suggesting that cytochrome a in the iron oxidase is involved in the transport process. The iron-oxidizing activity of strain OKM-9 was activated 1.7-fold by 80 mM L-glutamate. In contrast, the activity was noncompetitively inhibited by L-cysteine. The Michaelis constant of iron oxidase for Fe(2+) was 12.6 mM and the inhibition constant for L-cysteine was 41.6 mM. A marked inhibition of iron oxidase by 50 mM L-cysteine was completely reversed by the addition of 60 mM L-glutamate. The results suggest the possibility that iron oxidase has a binding site for L-cysteine and the cysteine first bound to the iron oxidase was replaced by the added L-glutamate. 相似文献
53.
Kamino T Yaguchi T Kuroda Y Ohnishi T Ishitani T Miyahara Y Horita Z 《Journal of electron microscopy》2004,53(5):459-463
Transmission electron microscopy (TEM) samples of an Mg-Al alloy has been prepared using a Ga-focused ion beam (FIB) milling at two different operating voltages of 10 kV and 40 kV to investigate the influence of the FIB energy on the sample quality. The fine structures of the samples have been studied using a high resolution TEM, and the concentration of the implanted Ga was analysed using an energy dispersive X-ray (EDX) analysis. The result of the TEM observation revealed that point defects were introduced to the sample finally milled at 40 kV but not at 10 kV. However, crystal lattice images and electron diffraction patterns were clearly observed on both the samples. The typical influence of the FIB energy was indicated in the elemental analysis. The relative Ga concentration in the thin sample finally milled at 10 kV was 1.0-2.0 at% that is less than half of 4.0-6.0 at% of the Ga concentration in the sample finally milled at 40 kV. A comparison between the experimental results of the Ga concentration measurement with simulation was also discussed. 相似文献
54.
Takeuchi F Negishi A Maeda T Kamimura K Sugio T 《Journal of Bioscience and Bioengineering》2003,95(3):239-244
The iron-oxidizing bacterium Acidithiobacillus ferrooxidans SUG 2-2 is markedly resistant to mercuric chloride and can volatilize mercury (Hg0) from mercuric ion (Hg2+) under acidic conditions. To develop a microbial technique to volatilize and recover mercury from acidic and organic compound-containing mercury wastewater, which is usually produced in the course of everyday laboratory work in Okayama University, the effects of organic and inorganic chemicals on the mercury volatilization activity of A. ferrooxidans cells were studied. Among 55 chemicals tested, the mercury volatilization from a reaction mixture (pH 2.5) containing resting cells of SUG 2-2 (1 mg of protein) and mercury chloride (14 nmol) was strongly inhibited by AgNO3 (0.05 mM), K2CrO7 (1.0 mM), cysteine (1.0 mM), trichloroethylene (1 microM), and commercially produced detergents (0.05%). However, the strong inhibition by trichloroethylene and detergents was not observed when these organic compounds were chemically decomposed using Fenton's method before the treatment of the wastewater with SUG 2-2 cells. When 20 ml of water acidified with sulfuric acid (pH 2.5) containing ferrous sulfate (3%), diluted mercury wastewater (17.5 nmol of Hg2+) and SUG 2-2 cells (0.05 mg of protein) were incubated for 10 d at 30 degrees C, 47% of the total mercury in the wastewater was volatilized and recovered into a trapping reagent for metal mercury. However, when the organic compounds in the mercury wastewater were decomposed using Fenton's method and then treated with A. ferrooxidans cells, approximately 100% of the total mercury in the wastewater was volatilized and recovered. 相似文献
55.
Koizumi H Yamamoto T Maki A Yamashita Y Sato H Kawaguchi H Ichikawa N 《Applied optics》2003,42(16):3054-3062
We will briefly review the present status of optical topography and then discuss the method of improving practicality, i.e., the signal-to-noise (S/N) ratio and the spatial resolution in observations of higher-order brain functions. The optimum wavelength pair improved the S/N ratio sixfold for deoxyhemoglobin, and new configurations of light irradiation and detection positions doubled the spatial resolution. We also report on developing application fields of optical topography. This modality will bridge the gap between natural sciences, neuroscience, and pedagogy, and show actual real-time brain activity. 相似文献
56.
Yanjiang Huang Lounell B. Gueta Ryosuke Chiba Tamio Arai Tsuyoshi Ueyama Jun Ota 《Advanced Robotics》2013,27(4):233-245
The focus of this study is on the problem of manipulator system selection for a multiple-goal task by evaluating task completion time and cost with computational time constraints. An approach integrating system selection, structural configuration design, layout design, motion planning, and relative cost calculation is proposed to solve this problem within a reasonable computational time. In the proposed approach, multiple-objective particle swarm optimization (MOPSO) is utilized to search for the appropriate manipulator system with appropriate structural configuration from a set of candidate systems. Particle swarm optimization (PSO) and the nearest neighborhood algorithm are employed in layout design and motion planning due to their high convergence speed. Three methods involving a random search algorithm are compared to the proposed approach through a simulation. The simulation is done with a set of tasks and the result shows the effectiveness of the proposed approach. 相似文献
57.
Web caching is one of the fundamental techniques for reducing bandwidth usage and download time while browsing the World Wide Web. In this research, we provide an improvement in web caching by combining the result of web usage mining with traditional web caching techniques. Web cache replacement policy is used to select which object should be removed from the cache when the cache is full and which new object should be put into the cache. There are several attributes used for selecting the object to be removed, such as the size of the object, the number of times the object was used, and the time when the object was added into the cache. However, the flaw in these previous approaches is that each object is treated separately without considering the relation among those objects. We have developed a system that can record users’ browsing behavior at the resources level. By using information gathered from this system, we can improve web cache replacement policy so that the number of cache hits will increase, resulting in a faster web browsing experience and less data bandwidth, especially at lower cache storage environments such as on smart phones. 相似文献
58.
Myat Su Mon Nobuya Mizoue Naing Zaw Htun Tsuyoshi Kajisa Shigejiro Yoshida 《International journal of remote sensing》2013,34(4):1042-1057
Although a number of image classification approaches are available to estimate forest canopy density (FCD) using satellite data, assessment of their relative performances with tropical mixed deciduous vegetation is lacking. This study compared three image classification approaches – maximum likelihood classification (MLC), multiple linear regression (MLR) and FCD Mapper – in estimating the FCD of mixed deciduous forest in Myanmar. The application of MLC and MLR was based on spectral reflectance of vegetation, whereas FCD Mapper was operated on integrating the biophysical indices derived from the reflectance of the vegetation. The FCD was classified into four categories: closed canopy forest (CCF; FCD ≥ 70%), medium canopy forest (MCF; 40% ≥ FCD < 70%), open canopy forest (OCF; 10% ≥ FCD < 40%) and non-forest (NF; FCD < 10%). In the three classification approaches, producer's and user's accuracies were higher for more homogeneous vegetation such as NF and CCF than for heterogeneous vegetation density (VD) such as OCF and MCF. FCD Mapper produced the best overall accuracy and kappa coefficient. This study revealed that only spectral reflectance is not enough to get good results in estimating FCD in tropical mixed deciduous vegetation. This study indicates that FCD Mapper, an inexpensive approach because it requires only validation data and thus saves time, can be applied to monitor tropical mixed deciduous vegetation over time at lower cost than alternative methods. 相似文献
59.
Takahiro Kawashima Tsuyoshi Kimura Takayuki Shibata Akio Kishida Takashi Mineta Eiji Makino 《Microelectronic Engineering》2010,87(5-8):704-707
In order to realize cellular network analysis on a chip-based system, our group has been developing a patterned cell culture microdevice with pillars in an array for tapping cells into space surrounded by the pillars. The pillar structures has advantages to trap both adhesive and non-adhesive cells and to precisely control positions of cells and distances between cells for understanding effects of various cell patterns on functions of a cellular network such as cell proliferation, differentiation, and network formation. In this paper, HeLa cell cultivation with the patterned cell culture microdevice having a pillar array fabricated by dry film of thick negative photoresist SU-8 on a glass substrate was executed as a feasibility study on a cellular network analysis. The results revealed that the device performance was found to be enough to culture HeLa cells for more than 48 h. In addition, relative extensibility of blocks of multiple cells compared with single cells tapped on the device was observed. Thus, the patterned cell culture microdevice proposed here could be applicable to analysis of cellular functions. 相似文献
60.
Satoshi Miyaguchi Shinichi Ishizuka Takeo Wakimoto Jun Funaki Yoshinori Fukuda Hirofumi Kubota Kenji Yoshida Teruichi Watanabe Hideo Ochi Tsuyoshi Sakamoto Masami Tsuchida Isamu Ohshita Teruo Tohma 《Journal of the Society for Information Display》1999,7(3):221-226
Abstract— A full-color 5.2-inch 1/4-VGA passive-matrix organic LED display has been developed, adopting selective deposition for the different emitting materials. The display features 320 (×3) × 240 pixels with an equivalent pixel size of 0.33 × 0.33 mm, white peak luminance of over 150 cd/m2, and power consumption of 6 W. 相似文献