全文获取类型
收费全文 | 22282篇 |
免费 | 2956篇 |
国内免费 | 1671篇 |
专业分类
电工技术 | 2022篇 |
技术理论 | 3篇 |
综合类 | 2187篇 |
化学工业 | 3667篇 |
金属工艺 | 784篇 |
机械仪表 | 1359篇 |
建筑科学 | 1119篇 |
矿业工程 | 1248篇 |
能源动力 | 4309篇 |
轻工业 | 262篇 |
水利工程 | 191篇 |
石油天然气 | 637篇 |
武器工业 | 618篇 |
无线电 | 1394篇 |
一般工业技术 | 1393篇 |
冶金工业 | 1214篇 |
原子能技术 | 84篇 |
自动化技术 | 4418篇 |
出版年
2024年 | 84篇 |
2023年 | 374篇 |
2022年 | 784篇 |
2021年 | 808篇 |
2020年 | 904篇 |
2019年 | 626篇 |
2018年 | 624篇 |
2017年 | 711篇 |
2016年 | 764篇 |
2015年 | 835篇 |
2014年 | 1296篇 |
2013年 | 1232篇 |
2012年 | 1597篇 |
2011年 | 1774篇 |
2010年 | 1336篇 |
2009年 | 1427篇 |
2008年 | 1288篇 |
2007年 | 1625篇 |
2006年 | 1396篇 |
2005年 | 1273篇 |
2004年 | 1047篇 |
2003年 | 957篇 |
2002年 | 766篇 |
2001年 | 623篇 |
2000年 | 541篇 |
1999年 | 418篇 |
1998年 | 306篇 |
1997年 | 286篇 |
1996年 | 260篇 |
1995年 | 211篇 |
1994年 | 156篇 |
1993年 | 117篇 |
1992年 | 104篇 |
1991年 | 69篇 |
1990年 | 73篇 |
1989年 | 53篇 |
1988年 | 20篇 |
1987年 | 25篇 |
1986年 | 14篇 |
1985年 | 30篇 |
1984年 | 26篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1957年 | 1篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
In this paper we propose a new protocol called time-space label switching protocol (TSL-SP) in optical burst switching (OBS), and define the terms time-space label (TSL) and time-space routing (TSR). An important concept of response time is introduced in the time label mechanism. The TSL-SP is a new technology that can quickly and efficiently forward data with a label on the optical networks. A two-dimension label switched path (TD-LSP) can be set up, that is maintained and deleted by the TSL-SP. For clearly illuminating the operation principles of the TSL-SP, we propose a new approach of orthogonal time-space coordinates in which the vertical coordinate is the space label and the horizontal coordinate is the time label. The proposed TD-LSP can dramatically reduce the routing failure probability and greatly improve the link network efficiency compared with other signaling protocols. Moreover, we define the time-space label control plane that can achieve the higher efficiency. When the TSL-SP is applied to networks, switching performance can be improved by two orders compared to the switching performance with the conventional OBS signaling protocols. The fundamental goal of TSL-SP is to band the signaling and routing functions together closely. Also, the TSL-SP can reduce the complexity of the network, support automatic service offering, and provide traffic engineering. 相似文献
102.
洁净型煤技术开发研制 总被引:4,自引:0,他引:4
通过对洁净型煤技术的介绍,并对型煤质量及燃烧测试分析,认为洁净型煤技术是一种煤的高效洁净燃烧、改善环境空气质量及节约能源的有效技术。 相似文献
103.
A model of economic dynamics under stable ecological balance conditions is proposed. A methodology of construction of an optimal growth path is constructed for this model. 相似文献
104.
H. -C. Chiao H. -L. Lin X. -T. Li C. -X. Ding 《Journal of Thermal Spray Technology》1992,1(2):111-115
Diamond growth with rates up to 100 to 140 μm/hr was achieved using an oxygen-acetylene combustion spraying technique in an
atmospheric environment. Investigations on the processing indicated that the gas flow ratio, substrate position, substrate
temperature, temperature distribution, and substrate pretreatment were the most important factors affecting the growth of
diamond crystals. Evaluation by means of X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and electron
probe microanalysis showed that the synthesized diamond was nearly perfect in morphology, structure, and purity. 相似文献
105.
Ln2B2O7 (Ln=Sm, Eu, Gd and Tb; B=Zr or Ti) with pyrochlore structure was prepared by sol–gel method for the high-temperature catalytic combustion. The crystal structure of Ln2B2O7 was identified by XRD and their surface area was about 4 m2/g after calcinations at 1200 °C. Catalytic activity of methane combustion was observed for Ln2Zr2O7 series and the best catalyst was Sm2Zr2O7. Its relative reaction rate per unit surface area at 600 °C was 2 cm3/m2 min, which was twice higher than that of Mn-substituted Sr hexaaluminate. From surface analysis by XPS, the low binding energy of each Ln element of Ln2Zr2O7 compared to that of Ln2Ti2O7, gave the catalytic activity of methane combustion. 相似文献
106.
对于某些槽数和极数比的多星形移相变极电机,提出与前人不同的是在两种极数下均不甩去线圈的绕组方案,使绕组利用率高,且线圈及其联接都较简单.这种绕组方案在一种极数下并联支路略有不平衡,其所引起的电机定子铜耗的增加是极其有限的,不致影响电机的正常运行. 相似文献
107.
Influence of Pt particle size on catalytic combustion of xylenes on carbon aerogel-supported Pt catalysts 总被引:3,自引:0,他引:3
M.N. Padilla-Serrano F.J. Maldonado-Hdar C. Moreno-Castilla 《Applied catalysis. B, Environmental》2005,61(3-4):253-258
Pt catalysts supported on a carbon aerogel with different Pt particle sizes were studied in the combustion of o-xylene and m-xylene. Results found show that the activity of the catalysts increased with larger Pt particle size. In addition, the catalysts were activated during consecutive combustion runs and during time on stream. This activation depends on the Pt particle size and type of xylene isomer. Activation was due to the increase in Pt particle size during reaction. The lower activity of catalysts with smaller Pt particle size was due to the stronger PtO bonds formed during xylene combustion by the smaller Pt particles. 相似文献
108.
I.Z. Ismagilov R.P. Ekatpure L.T. Tsykoza E.V. Matus E.V. Rebrov M.H.J.M. de Croon M.A. Kerzhentsev J.C. Schouten 《Catalysis Today》2005,105(3-4):516-2
This paper describes the optimization of three processes applied in fabrication of a microstructured reactor for complete oxidation of volatile organic compounds. The first process involves the optimization of the electro discharge machining (EDM) method to produce a set of microchannels with a high length to diameter ratio of 100, with a standard deviation from the average diameter below 0.2%, and with a surface roughness not higher than 2.0 μm. To satisfy these criteria, fabrication of microchannels must be carried out with two machining passes in the Al51st alloy. Then, the effect of several parameters on the anodization current efficiency with respect to oxide formation was studied. The best process conditions to get a 30 μm porous alumina layer in a 0.4 M oxalic acid electrolyte, were found to be a temperature of 1 °C, an anodic current density of 5 mA/cm2, and 23 h oxidation time. At last, the resulting coatings were impregnated with an aqueous solution of copper dichromate followed by drying and calcination at 450 °C to produce active catalysts. The effect of a copper dichromate concentration, number of impregnation cycles (1 or 2), and different after-treatments on catalytic activity and stability in complete oxidation of n-butane were studied. The catalytic activity of the obtained coatings is superior to that of alumina supported pelletized catalysts even at much lower loadings of active metals. 相似文献
109.
低NOx燃烧技术及应用 总被引:2,自引:0,他引:2
阐述了燃料燃烧过程中NOx的生成机里和抑制方法,介绍了降低NOx的燃烧技术及应用效果. 相似文献
110.
B. Basil Beamish 《Fuel》2008,87(1):125-130
Adiabatic self-heating tests have been conducted on subbituminous coal cores from the same seam profile, which cover a mineral matter content range of 11.2-71.1%. In all cases the heat release rate does not conform to an Arrhenius kinetic model, but can best be described by a third order polynomial. Assessment of the theoretical heat sink effect of the mineral matter in each of the tests reveals that the coal is less reactive than predicted using a simple energy conservation equation. There is an additional effect of the mineral matter in these cases that cannot be explained by heat sink alone. The disseminated mineral matter in the coal is therefore inhibiting the oxidation reaction due to physicochemical effects. 相似文献