全文获取类型
收费全文 | 1090篇 |
免费 | 31篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 175篇 |
金属工艺 | 8篇 |
机械仪表 | 15篇 |
建筑科学 | 35篇 |
矿业工程 | 2篇 |
能源动力 | 18篇 |
轻工业 | 80篇 |
水利工程 | 9篇 |
石油天然气 | 6篇 |
无线电 | 77篇 |
一般工业技术 | 187篇 |
冶金工业 | 399篇 |
原子能技术 | 4篇 |
自动化技术 | 100篇 |
出版年
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 18篇 |
2017年 | 17篇 |
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 14篇 |
2013年 | 34篇 |
2012年 | 27篇 |
2011年 | 49篇 |
2010年 | 34篇 |
2009年 | 20篇 |
2008年 | 53篇 |
2007年 | 40篇 |
2006年 | 35篇 |
2005年 | 39篇 |
2004年 | 22篇 |
2003年 | 33篇 |
2002年 | 22篇 |
2001年 | 35篇 |
2000年 | 21篇 |
1999年 | 31篇 |
1998年 | 96篇 |
1997年 | 59篇 |
1996年 | 45篇 |
1995年 | 37篇 |
1994年 | 21篇 |
1993年 | 18篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 20篇 |
1989年 | 9篇 |
1988年 | 23篇 |
1987年 | 13篇 |
1986年 | 16篇 |
1985年 | 7篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1977年 | 10篇 |
1976年 | 17篇 |
1974年 | 4篇 |
1971年 | 7篇 |
1970年 | 8篇 |
1969年 | 5篇 |
1961年 | 4篇 |
排序方式: 共有1123条查询结果,搜索用时 15 毫秒
81.
Styrene undergoes efficient epoxidation to styrene epoxide on the Cu{111} surface. At the optimum condition (Θo = 0.03 ML) ∼20% of the styrene is converted to the epoxide with almost 100% selectivity. Comparison with Ag{111} shows that the epoxidation activity and selectivity of Cu greatly exceed those of Ag. Incipient oxidation of the Cu{111} surface does not suppress the adsorption of styrene, but the oxidised metal is catalytically inert. Submonolayer amounts of Cs enhance styrene uptake and increase conversion to the epoxide without adversely affecting epoxidation selectivity. This effect is due to inhibition of Cu oxidation by Cs. Our findings are discussed in the light of current understanding of Ag‐catalysed alkene epoxidation. This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
82.
H Thomas MM Nasim CE Sarraf MR Alison S Love HE Lambert P Price 《Canadian Metallurgical Quarterly》1995,71(2):357-362
The measurement of tumour cell proliferation is becoming increasingly recognised in defining prognostic groups. Proliferating cell nuclear antigen (PCNA) immunolocalisation can be used as an index of cell proliferation and may define the extent of departure from normal growth control. The monoclonal antibody PC10 stains PCNA in archival paraffin-embedded tissue. This study investigates its potential as a prognostic marker in early and advanced ovarian cancer. A three-stage immunoperoxidase technique was developed to detect the monoclonal antibody PC10. Archival paraffin-embedded tissue from 19 stage I ovarian tumours (13 malignant and six borderline) and 79 advanced (stage IIb-IV) ovarian tumours (patients entered into the Third North-West Thames Ovarian Cancer Trial) was immunostained with PC10. PC10 immunostaining was performed successfully in 91.8% of cases. The PC10 labelling index (PC10 LI) ranged from 1.5% to 88% with a mean value of 47.4%. Stage I borderline tumours had significantly lower PCNA labelling indexes than stage I malignant tumours (P < 0.048). In advanced disease there was an inverse correlation between PC10 and overall survival, and in those patients who underwent good debulking surgery (37 patients with disease < 2 cm diameter) a low PC10 value (< 36.5%) correlated with improved survival (log-rank trend test for survival, chi 2 = 5.75, P = 0.017). PCNA immunostaining defines a good prognostic subgroup in adequately debulked patients with ovarian cancer. 相似文献
83.
A ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ membrane supported on a macroporous $\alpha {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ tube was prepared by sol–gel processing and used in the partial hydrogenation of acetylene and 1,3-butadiene. The average pore diameter of the ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ membrane was 3.6 nm. The gases were separated by Knudsen diffusion. The activity and selectivity of the ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ membrane was compared to that of ${\text{Pd/}}\gamma {\text{ - Al}}_{\text{2}} {\text{O}}_{\text{3}}$ catalysts used in a conventional packed bed reactor. The highest selectivity to the partially hydrogenated products occurred when the reactant was premixed with H2 and was passed through the membrane wall. 相似文献
84.
A new ballistic limit equation has been developed for the case of a Whipple shield configuration or a sandwich panel with honeycomb core placed in front of a backwall. This “triple plate” ballistic limit equation considers explicitly the thicknesses, materials and spacings of each of the three plates. The third plate, i.e., the backwall, represents the cover plate or external wall of the equipment that is placed behind the satellite structure wall. The ballistic limit equation has been calibrated with experimental results obtained from hypervelocity impact tests on satellite equipment that was placed behind typical satellite structure walls. The equipment considered were fuel and heat pipes, pressure vessels, electronic boxes, harness, and batteries, all representative of real satellite equipment. The new equation was applied to prove that if the inherent protection capability of satellite equipment against hypervelocity impacts is explicitly considered in a ballistic limit equation, the critical projectile diameters for failure of such equipment are raised considerably compared to the case where equipment is assumed to fail as soon as the structure wall that protects it is perforated. 相似文献
85.
D. M. Lewis M. F. Lambert M. D. Burch J. D. Brookes 《Canadian Metallurgical Quarterly》2010,136(9):642-650
Full-scale field acoustic Doppler velocimeter measurements of the radial, axial, and tangential flow components were undertaken in a large-diameter turbulent swirling jet generated by a raft-mounted axial flow-mixing propeller discharging through a draft tube during isothermal and stratified conditions. The results were compared with classical jet theory and showed significant differences in the zone of flow establishment though similar behavior in the zone where established flow was found. It was concluded that the efflux from the axial flow-mixing propeller could not be described adequately by conventional jet theory due to the jet size and swirling characteristics. 相似文献
86.
David Lambert Director 《Landscape Research》2013,38(1):43-62
The origins of the Country Park are examined and the implications of those origins are analysed. Country Parks are followed through to the present, including their enthusiastic sponsorship by the Countryside Commission, their role in local authority policy and practice, and the decline noted in the 1999 House of Commons Select Committee inquiry into Town and Country Parks. In the last two years, the Country Parks Network, administered by Green Space and funded by the government, has shown the tenacity of the Country Park, and there are encouraging signs from the Countryside Agency of renewed interest, and its hopes for a ‘Renaissance in Country Parks’. A summary of this period is also included, but an assessment of the effectiveness of its initiatives must wait for more time to pass. 相似文献
87.
Lee T.-H. Rudduck R.C. Lambert K.M. 《Antennas and Propagation, IEEE Transactions on》1990,38(6):889-895
The measurements were performed at the University's compact range facility. They demonstrated: (1) the excellent dynamic range that can be achieved with antenna pattern measurements in a compact range facility; and (2) the excellent validation achieved for the calculated patterns of two 8-ft diameter reflector antennas. The compact range has a rolled edge modification to its reflector and uses a pulsed radar system to eliminate the clutter interference such that a dynamic range of more than 80 dB can be obtained. The measured far field patterns of two 8-ft reflector antennas, a prime focus fed antenna and a Cassegrain antenna, at 11 GHz were compared with those calculated by Ohio State University's Reflector Antenna Code. The computer code simulation's approach is also briefly described 相似文献
88.
89.
90.
Studied selective attention, using data from 63 adult Ss collected in 4 experiments in which stimuli varied in both spatial location and visual form. In Exp I, the likely location and likely form of targets were both precued. An advantage was found for cued over uncued forms at both cued and uncued locations. In Exps II, III, and IV, different forms tended to occur at different locations. Regardless of whether a location was cued or uncued, form selective effects were found in accordance with form probability for that location. It was not the case that selective attention simply favored certain locations or certain stimulus forms in preference to others. Rather, selective attention was sensitive to precise combinations of form and location. It is concluded that these results can not be reconciled with mental spotlight notions of spatial selectivity. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献