全文获取类型
收费全文 | 743036篇 |
免费 | 9592篇 |
国内免费 | 2719篇 |
专业分类
电工技术 | 14370篇 |
技术理论 | 5篇 |
综合类 | 1611篇 |
化学工业 | 117865篇 |
金属工艺 | 30476篇 |
机械仪表 | 23533篇 |
建筑科学 | 17490篇 |
矿业工程 | 5370篇 |
能源动力 | 18550篇 |
轻工业 | 63087篇 |
水利工程 | 8744篇 |
石油天然气 | 17989篇 |
武器工业 | 278篇 |
无线电 | 79111篇 |
一般工业技术 | 148081篇 |
冶金工业 | 129637篇 |
原子能技术 | 17554篇 |
自动化技术 | 61596篇 |
出版年
2021年 | 7181篇 |
2020年 | 5194篇 |
2019年 | 6612篇 |
2018年 | 11228篇 |
2017年 | 11354篇 |
2016年 | 12007篇 |
2015年 | 8069篇 |
2014年 | 13190篇 |
2013年 | 34209篇 |
2012年 | 20972篇 |
2011年 | 28079篇 |
2010年 | 22547篇 |
2009年 | 24772篇 |
2008年 | 25514篇 |
2007年 | 25445篇 |
2006年 | 22212篇 |
2005年 | 19833篇 |
2004年 | 18428篇 |
2003年 | 17872篇 |
2002年 | 17391篇 |
2001年 | 17045篇 |
2000年 | 16256篇 |
1999年 | 16032篇 |
1998年 | 36874篇 |
1997年 | 26791篇 |
1996年 | 20807篇 |
1995年 | 15881篇 |
1994年 | 14493篇 |
1993年 | 14070篇 |
1992年 | 10986篇 |
1991年 | 10598篇 |
1990年 | 10510篇 |
1989年 | 10282篇 |
1988年 | 9743篇 |
1987年 | 8742篇 |
1986年 | 8557篇 |
1985年 | 9681篇 |
1984年 | 8955篇 |
1983年 | 8478篇 |
1982年 | 7615篇 |
1981年 | 7862篇 |
1980年 | 7376篇 |
1979年 | 7598篇 |
1978年 | 7432篇 |
1977年 | 8102篇 |
1976年 | 10282篇 |
1975年 | 6712篇 |
1974年 | 6412篇 |
1973年 | 6476篇 |
1972年 | 5511篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
The effects of α and β phase interactions on the room-temperature tensile and creep deformation behavior of α + β titanium
alloys with Widmanst?tten microstructures were studied using Ti-6.0 wt pct Mn and Ti-8.1 wt pct V as the model two-phase alloy
systems. This article, Part I, deals with tensile deformation. It was found that when the α phase is present as thin (<10-μm)
plates in the α + β alloys, significant twinning occurs. No significant twinning was observed in single-phase alloys with
the same chemistry and similar grain size. Additionally, the β phase of Ti-8.1 V deforms by stress-induced hexagonal martensite
(α′), while only twinning occurs in the single-phase β alloy with the same chemistry. Twinning in the α phase in association
with stress-induced martensite (SIM) in the β phase was observed for the first time in a two-phase titanium alloy. This behavior
is explained in terms of a number of factors including elastic interaction stresses between the α and β phases, coherency
between the α phase and hexagonal martensite, and β phase stability. 相似文献
23.
Stormwater quality simulation models are useful tools for the design and management of sewer systems. Modelling results are highly sensitive to experimental data used for calibration. This sensitivity is examined for three modelling approaches of various complexities (site mean concentration approach, event mean concentration approach and build-up, washoff and transport modelling approach) applied to a typical case study (design of a dry detention tank), accounting for the variability of calibration data and their effect on simulation results. Calibrated models with different calibration data sets were used to simulate 3 years of rainfall with different retention tank specific volumes. Annual pollutant load interception efficiencies were determined. Simulations results revealed (i) that there is no advantage in using the EMC model compared to the SMC model and (ii) that the BWT model resulted in higher design ratios than those given by the SMC/hydraulic approach. For both EMC and BWT models, using an increasing number n of events for calibration leads to narrower confidence intervals for the design ratios. It is crucial for design ratios to account for successive storm events in chronological order and to account for the maximum allowable flow to be transferred to the downstream WWTP. 相似文献
24.
The Magnitogorsk Metallurgical Combine has conducted a study of the effect of technological factors on the hydrogen content
of chromium-nickel-molybdenum steel after vacuum degassing. It was established that the most important factor is the hydrogen
content of the steel before the degassing operation. The study also determined the effects of the circulation coefficient,
the duration of the degassing operation, and the vacuum used in the treatment.
__________
Translated from Metallurg, No. 7, pp. 68–69, July, 2006. 相似文献
25.
Note on B-splines, wavelet scaling functions, and Gabor frames 总被引:3,自引:0,他引:3
Grochenig K. Janssen A.J.E.M. Kaiblinger N. Pfander G.E. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2003,49(12):3318-3320
Let g be a continuous, compactly supported function on such that the integer translates of g constitute a partition of unity. We show that the Gabor system (g,a,b), with window g and time-shift and frequency-shift parameters a,b>0 has no lower frame bound larger than 0 if b=2,3,... and a>0. In particular, (g,a,b) is not a Gabor frame if g is a continuous, compactly supported wavelet scaling function and if b=2,3,... and a>0. We give an example for our result for the case that g=B/sub 1/, the triangle function supported by [-1,1], by showing pictures of the canonical dual corresponding to (g,a,b) where ab=1/4 and b crosses the lines N=2,3,. 相似文献
26.
Supported metal catalysts, particularly noble metals supported on SiO2, have attracted considerable attention due to the importance of the silica–metal interface in heterogeneous catalysis and in electronic device fabrication. Several important issues, e.g., the stability of the metal–oxide interface at working temperatures and pressures, are not well-understood. In this review, the present status of our understanding of the metal–silica interface is reviewed. Recent results of model studies in our laboratories on Pd/SiO2/Mo(1 1 2) using LEED, AES and STM are reported. In this work, epitaxial, ultrathin, well-ordered SiO2 films were grown on a Mo(1 1 2) substrate to circumvent complications that frequently arise from the silica–silicon interface present in silica thin films grown on silicon. 相似文献
27.
This study was undertaken to develop a modified atmosphere package to control microbial growth in ready‐to‐eat (RTE) products stored at ambient temperature. Ethanol and/or limonene associated with modified atmosphere (CO2 : O2 : N2 = 30% : 5% : 65%) was used to inhibit the growth of total air‐borne microorganisms and Escherichia coli in RTE products stored at 25°C. The results indicated that 0.05% ethanol vapour in the headspace was effective to inhibit the growth of air‐borne microorganisms and E. coli at 25°C for 72 h in a model study, and the effectiveness was related to ethanol content. Both 73 ppm limonene and 0.05% ethanol vapour enhanced the bacteriostatic effect of modified atmosphere in RTE sushi roll products, and no off‐flavour was detected using this formulated gas; however, no significant inhibitory effect was observed for RTE cold noodle products. This study concludes that combinations of carbon dioxide, ethanol or limonene vapours are effective to inhibit microbial growth in RTE food at ambient temperature, and the outcome may be due to the hurdle effect. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
28.
The basic methods of verifying continuous automatic belt weighers are described. A comparative analysis of these methods on the basis of experimental studies is made and ways of implementing the results in industry are recommended. 相似文献
29.
de Oliveira J.C. Hosseini M. Shirmohammadi S. Malric F. Nourian S. El Saddik A. Georganas N.D. 《Multimedia, IEEE》2003,10(3):18-29
Using Java-based tools in multimedia collaborative environments accessed over the Internet can increase an application's client base. Most operating systems support Java, and its "compile once-run everywhere" architecture is easy to maintain and update. The Java-based tools presented here let users share Internet resources, including resources originally designed for single use. 相似文献
30.
L. Gao P. Hrter Ch. Linsmeier J. Gstttner R. Emling D. Schmitt-Landsiedel 《Materials Science in Semiconductor Processing》2004,7(4-6):331
Deposition of Ag films by direct liquid injection-metal organic chemical vapor deposition (DLI-MOCVD) was chosen because this preparation method allows precise control of precursor flow and prevents early decomposition of the precursor as compared to the bubbler-delivery. Silver(I)-2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedionato-triethylphosphine [Ag(fod)(PEt3)] as the precursor for Ag CVD was studied, which is liquid at 30 °C. Ag films were grown on different substrates of SiO2/Si and TiN/Si. Argon and nitrogen/hydrogen carrier gas was used in a cold wall reactor at a pressure of 50–500 Pa with deposition temperature ranging between 220 °C and 350 °C. Ag films deposited on a TiN/Si diffusion barrier layer have favorable properties over films deposited on SiO2/Si substrate. At lower temperature (220 °C), film growth is essentially reaction-limited on SiO2 substrate. Significant dependence of the surface morphology on the deposition conditions exists in our experiments. According to XPS analysis pure Ag films are deposited by DLI-MOCVD at 250 °C by using argon as carrier gas. 相似文献