全文获取类型
收费全文 | 1869篇 |
免费 | 79篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 97篇 |
综合类 | 12篇 |
化学工业 | 477篇 |
金属工艺 | 48篇 |
机械仪表 | 56篇 |
建筑科学 | 62篇 |
矿业工程 | 1篇 |
能源动力 | 59篇 |
轻工业 | 152篇 |
水利工程 | 7篇 |
石油天然气 | 15篇 |
武器工业 | 1篇 |
无线电 | 128篇 |
一般工业技术 | 348篇 |
冶金工业 | 242篇 |
原子能技术 | 93篇 |
自动化技术 | 157篇 |
出版年
2023年 | 8篇 |
2022年 | 28篇 |
2021年 | 48篇 |
2020年 | 33篇 |
2019年 | 37篇 |
2018年 | 31篇 |
2017年 | 43篇 |
2016年 | 43篇 |
2015年 | 41篇 |
2014年 | 57篇 |
2013年 | 106篇 |
2012年 | 76篇 |
2011年 | 101篇 |
2010年 | 87篇 |
2009年 | 90篇 |
2008年 | 111篇 |
2007年 | 89篇 |
2006年 | 63篇 |
2005年 | 57篇 |
2004年 | 57篇 |
2003年 | 56篇 |
2002年 | 54篇 |
2001年 | 40篇 |
2000年 | 41篇 |
1999年 | 47篇 |
1998年 | 112篇 |
1997年 | 67篇 |
1996年 | 45篇 |
1995年 | 44篇 |
1994年 | 26篇 |
1993年 | 31篇 |
1992年 | 16篇 |
1991年 | 9篇 |
1990年 | 14篇 |
1989年 | 13篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 13篇 |
1984年 | 14篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 13篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 4篇 |
1969年 | 4篇 |
排序方式: 共有1955条查询结果,搜索用时 796 毫秒
21.
A solid oxide fuel cell constructed from Ni-SDC anode and LSGM electrolyte was applied to the partial oxidation of methane to syngas (CO+H2) at 700-800 °C with the merits of co-generation of electricity and controllable O2 supply. It was found that the co-generated syngas at H2/CO ratio of 1.4-2.0 varied with applied current densities, CH4 flow rates and operating temperatures. The cell voltage at 100 mA cm−2 and 800 °C was 0.90 V, i.e. about 90 mW cm−2 power density could be obtained. The cell operating at 50 mA cm−2 for 24 h almost showed no degradation of the cell performance. The observed carbon deposition seemed mainly taking place by CH4 cracking reaction. 相似文献
22.
Ki Soo ParkMyung Hun Cho Sang Ho ParkKee Suk Nahm Yang Kook SunYun Sung Lee Masaki Yoshio 《Electrochimica acta》2002,47(18):2937-2942
Layered Li0.7[M1/6Mn5/6]O2 (M=Li, Ni) was synthesized using a sol-gel method. P2-Na0.7[M1/6Mn5/6]O2 precursor was first synthesized by a sol-gel method, and then O2-Li0.7[M1/6Mn5/6]O2 was prepared by an ion exchange of Li for Na in P2-Na0.7[M1/6Mn5/6]O2 precursor. From charge/discharge curves, it was seen that Li0.7[Li1/6Mn5/6]O2 has two plateaus similar to those observed from a spinel structure, but Li0.7[Ni1/6Mn5/6]O2 holds a single plateau as observed from a typical layered structure. It was considered that Li0.7[Li1/6Mn5/6]O2 undergoes a phase transformation from layered to spinel structure during the charge/discharge cycle, but Li0.7[Ni1/6Mn5/6]O2 maintains O2-layered structure after the cycles. Li0.7[Ni1/6Mn5/6]O2 was higher in discharge capacity and retention rate than Li0.7[Li1/6Mn5/6]O2. 相似文献
23.
Uniaxially oriented thin films of poly(ethylene terephthalate) (PET), poly(ethylene 2,6-naphthalene dicarboxylate) (PEN) and their blends were prepared by applying shear strain to their respective melts, and the resulting morphologies were studied by transmission electron microscopy. Selected-area electron diffraction of each film revealed well-defined uniaxial orientation of polymer chains in the shearing direction. In the uniaxially oriented thin film of PEN, stacked-lamellar structure with the average long period of 27 nm consisting of a crystalline region about 15 nm thick and an amorphous one about 12 nm thick was found here and there in the dark-field image: PEN-type. On the other hand, stacked-lamellar structure was rarely observed in the case of PET: PET-type. In PET/PEN blends, the morphologies changed from the PET-type to the PEN-type with increasing content of PEN. 相似文献
24.
Toshiaki Enoki Yousuke Kobayashi Chika Katsuyama Vladimir Yu. Osipov Marina V. Baidakova Kazuyuki Takai Ken-ichi Fukui Alexander Ya. Vul'' 《Diamond and Related Materials》2007,16(12):2029-2034
The structure, electronic and magnetic properties of nanodiamond and nanographite/nanographene are investigated. Detonation nanodiamond particles that are covered with amorphous graphitic composites are hydrothermally treated to remove the graphitic surface composites and to terminate the surface carbon atoms with hydrogen. The number of localized spins of dangling bonds and the hydrogen concentration increase upon the increase in the hydrothermal treatment time up to 40 h. Above 40 h, both drop discontinuously, a surface structural reconstruction was suggested. The creation of dangling bonds and an incomplete hydrogenation of the surface carbon atoms destabilize the surface, resulting in the structural reconstruction. Nanodiamond particles are thermally converted to nanographite/nanographene. A single nanographene sheet is successfully prepared by heat-treating nanodiamond particles. The edge of graphene sheet with its edge carbon atoms being hydrogen-terminated is investigated by UHV-STM/STS. Zigzag edges are found to have non-bonding π-state of edge origin, in good agreement with theoretical prediction. 相似文献
25.
Kosuke Aiuchi Ryo Moriyama Shohei Takeda Shunji Kitada Masaki Onozaki Yukuo Katayama 《Fuel Processing Technology》2007
A pre-heating vaporization technology of coal water slurry, CWS, was developed to increase the efficiency of coal gasification with the reduction of oxygen consumption. A CWS pre-heating experimental unit having a capacity of 2.0 tons-coal/day was manufactured. After the CWS was heated to 573 K at about 10 MPa, water in CWS was continuously vaporized in a tube of which the diameter increased gradually (2–10 mm I.D.), and dry coal particles with steam were atomized and fed to a vessel. No aggregation of coal particles was observed in the atomized samples. The temperature and the pressure distributions of the fluid were calculated with empirical heat transfer and pressure drop correlations. The calculated results well corresponded to the experimental data measured in some test points. Using the calculation model, a large scale apparatus of 100 tons-coal/day was designed using KNO3 + NaNO2 + NaNO3 molten salt as a heating medium. 相似文献
26.
Yamauchi Toshihiro Akao Yohei Yoshitani Ryota Nakamura Yuichi Hashimoto Masaki 《International Journal of Information Security》2021,20(4):461-473
International Journal of Information Security - Cyberattacks, especially attacks that exploit operating system vulnerabilities, have been increasing in recent years. In particular, if administrator... 相似文献
27.
Functionally graded materials (FGMs) belong to a relatively new class of inhomogeneous composite materials, in which the composition
and/or microstructure undergo a gradual change along some directions. In this review article, the microstructures and composition
gradients in Al/SiC, Al/Shirasu (volcanic eruptions commonly found in south Kyushu in Japan), Al/Al3Ti, Al/Al3Ni, Al/Al2Cu FGMs have been investigated. The Al/SiC, Al/Shirasu and Al/Al3Ti FGMs are fabricated by the centrifugal solid particle method where the distribution particles of SiC, Shirasu and Al3Ti are solids in the melts. On the other hand, Al/Al3Ni and Al/Al2Cu FGMs are fabricated by the centrifugalin-situ method where Al/Al3Ni and Al/Al2Cu systems have lower liquidus temperatures than the processing temperatures. The feature of Al/(Al3Ti−Al3Ni) hydrid FGM, which is fabricated by a method combining both the centrifugal solid-particle andin-situ methods, is also shown. 相似文献
28.
Hand gestures are potentially useful for communications between humans and between a human and a machine. However, existing methods entail several problems for practical use. We have proposed an approach to hand shape recognition based on wrist contour measurement. Especially in this paper, two assignments are addressed. First is the development of a new sensing device in which all elements are installed in a wrist-watch-type device. Second is the development of a new hand shape classifier that can accommodate pronation angle changes. The developed sensing device enables wrist contour data collection under conditions in which the pronation angle varies. The classifier recognizes the hand shape based on statistics produced through data forming and statistics conversion processes. The most important result is that no large difference exists between classification rates that include or those that exclude the independent (preliminary) pronation estimation process using inertia measurement units. This result shows two possible insights: (1) the wrist contour has some features that depend on the hand shape but which do not depend on the pronation angle, or (2) the wrist contour potentially includes pronation angle variation information. These insights indicate the possibility that hand shape can be recognized solely from the wrist contour, even while changing the pronation angle. 相似文献
29.
Truyen Van Phan Kha Cong Nguyen Masaki Nakagawa 《International Journal on Document Analysis and Recognition》2016,19(1):49-64
A Nom historical document recognition system is being developed for digital archiving that uses image binarization, character segmentation, and character recognition. It incorporates two versions of off-line character recognition: one for automatic recognition of scanned and segmented character patterns (7660 categories) and the other for user handwritten input (32,695 categories). This separation is used since including less frequently appearing categories in automatic recognition increases the misrecognition rate without reliable statistics on the Nom language. Moreover, a user must be able to check the results and identify the correct categories from an extended set of categories, and a user can input characters by hand. Both versions use the same recognition method, but they are trained using different sets of training patterns. Recursive X–Y cut and Voronoi diagrams are used for segmentation; k–d tree and generalized learning vector quantization are used for coarse classification; and the modified quadratic discriminant function is used for fine classification. The system provides an interface through which a user can check the results, change binarization methods, rectify segmentation, and input correct character categories by hand. Evaluation done using a limited number of Nom historical documents after providing ground truths for them showed that the two stages of recognition along with user checking and correction improved the recognition results significantly. 相似文献
30.
Wang P Behan G Kirkland AI Nellist PD Cosgriff EC D'Alfonso AJ Morgan AJ Allen LJ Hashimoto A Takeguchi M Mitsuishi K Shimojo M 《Ultramicroscopy》2011,111(7):877-886
Scanning confocal electron microscopy (SCEM) offers a mechanism for three-dimensional imaging of materials, which makes use of the reduced depth of field in an aberration-corrected transmission electron microscope. The simplest configuration of SCEM is the bright-field mode. In this paper we present experimental data and simulations showing the form of bright-field SCEM images. We show that the depth dependence of the three-dimensional image can be explained in terms of two-dimensional images formed in the detector plane. For a crystalline sample, this so-called probe image is shown to be similar to a conventional diffraction pattern. Experimental results and simulations show how the diffracted probes in this image are elongated in thicker crystals and the use of this elongation to estimate sample thickness is explored. 相似文献