全文获取类型
收费全文 | 9317篇 |
免费 | 467篇 |
国内免费 | 176篇 |
专业分类
电工技术 | 317篇 |
综合类 | 260篇 |
化学工业 | 1799篇 |
金属工艺 | 312篇 |
机械仪表 | 300篇 |
建筑科学 | 618篇 |
矿业工程 | 159篇 |
能源动力 | 217篇 |
轻工业 | 718篇 |
水利工程 | 143篇 |
石油天然气 | 158篇 |
武器工业 | 46篇 |
无线电 | 996篇 |
一般工业技术 | 1273篇 |
冶金工业 | 1463篇 |
原子能技术 | 125篇 |
自动化技术 | 1056篇 |
出版年
2023年 | 107篇 |
2022年 | 193篇 |
2021年 | 267篇 |
2020年 | 157篇 |
2019年 | 178篇 |
2018年 | 187篇 |
2017年 | 207篇 |
2016年 | 185篇 |
2015年 | 251篇 |
2014年 | 280篇 |
2013年 | 415篇 |
2012年 | 366篇 |
2011年 | 491篇 |
2010年 | 383篇 |
2009年 | 377篇 |
2008年 | 448篇 |
2007年 | 357篇 |
2006年 | 344篇 |
2005年 | 267篇 |
2004年 | 206篇 |
2003年 | 196篇 |
2002年 | 198篇 |
2001年 | 172篇 |
2000年 | 181篇 |
1999年 | 216篇 |
1998年 | 376篇 |
1997年 | 274篇 |
1996年 | 198篇 |
1995年 | 157篇 |
1994年 | 141篇 |
1993年 | 125篇 |
1992年 | 84篇 |
1991年 | 79篇 |
1990年 | 86篇 |
1989年 | 87篇 |
1988年 | 79篇 |
1987年 | 81篇 |
1986年 | 79篇 |
1985年 | 79篇 |
1984年 | 88篇 |
1983年 | 80篇 |
1982年 | 69篇 |
1981年 | 52篇 |
1979年 | 57篇 |
1978年 | 73篇 |
1977年 | 69篇 |
1976年 | 103篇 |
1975年 | 62篇 |
1974年 | 59篇 |
1973年 | 61篇 |
排序方式: 共有9960条查询结果,搜索用时 296 毫秒
101.
102.
L. H. Lang D. C. Kang S. H. Zhang Z. R. Wang S. J. Yuan K. B. Nielsen J. Dancket ) Department of Materials Engineering Harbin Institute of Technology Harbin China ) Aalberg University Denmark 《金属学报(英文版)》2000,13(2):476-480
1.~nonHydridapawhcdeepdrawing(HDD)belongstothefieldofsheetmetalfoeingandcanbeaPPliedinthefieldofautomotive,aerospace,drilitaryindustryetc.Ithasbeenrecognizedwidelyintheworld["'j.Fig.Ishowsitsprinciple:TheliqUidthatisfilledinthe~ngdiecavitywillbepressedwhenthepunchgoesdownsothattheeffectoffrictionkeepingandoverflowlubricatingcanbeformed,astherestilt,thefoeinglicitofsheetmetalwillbeimprovedareailvandthegualitVofthefinishedpartswillbeup~ed.BecauseofmanyadvantagesofHDDprocees,ithasbeenwidelys… 相似文献
103.
微量稀土和硼在铜及其合金中的作用 总被引:28,自引:6,他引:28
介绍了近年来微量稀土和硼在其合金中的应用,稀土在铜和铜合金中去除杂质,净化晶界,细化组织,消除柱状晶的作用,从而改善铜和铜合金的导电性,力学性能,冷热加工性能和耐磨性性能,硼在铜和铜合金中有比稀土更显著的细化晶粒作用。 相似文献
104.
105.
Johanna Stenzel Schruben Walter Gregson Vaux 《Chemical Engineering Communications》1985,33(5):337-347
This paper describes the kinetics of attrition in the bubbling zone of a fluidized bed and focuses on the development of an equation for attrition in continuous fluidized beds operating at steady state.
Laboratory data describing batch attrition of a limestone sorbent are applied to the integrated equations to describe overall attrition rate in a full-scale continuous system. 相似文献
Laboratory data describing batch attrition of a limestone sorbent are applied to the integrated equations to describe overall attrition rate in a full-scale continuous system. 相似文献
106.
Jose Gerde Connie Hardy Walter Fehr Pamela J. White 《Journal of the American Oil Chemists' Society》2007,84(6):557-563
Two extruded-expelled physically refined soybean oils with reduced contents of linolenic acid, ultra-low- linolenic acid (ULL,
1.5%) and low-linolenic acid (LL, 2.6%), and a extruded-expelled physically refined control oil (control, 5.3% linolenic acid)
were evaluated by frying French fries in a commercial-like setting for 6 h day−1 during 23 days. The oils became darker, increased in yellow color at the beginning, and became redder and less green throughout
the process. Free fatty acids levels were not different among the oils until day 14, after which, ULL was different from the
control for the remainder of frying. The conjugated dienoic acid values were greatest in the control. Generally, ULL and LL
oils had lower percentages of polar compounds than did the control, providing a frying life 2 days longer than the control
and ~30% increase in frying time. A trained sensory panel evaluated the French fries on days 2, 5, and 6. Buttery and potato
flavors decreased, and rancid and painty flavors increased over frying time for all products. Rancid flavor was highest in
the fries from the control oil. Overall, the ULL and LL oils performed better than did the control oil and ULL tended to perform
better than the LL. 相似文献
107.
The decomposition of 1,2-dichloroethane on polycrystalline copper has been studied using a microreactor. The reaction is found to have an activation energy of 81±5 kJ mol–1 generating gaseous ethene and chemisorbed chlorine. The reaction terminates on completion of a monolayer of chemisorbed chlorine and is followed by a much slower reaction. The rate limiting step is thought to be C2H4Cl2(phys)C2H4Cl(ads)+Clads The reaction is compared with a UHV study of the same molecule on Cu(l 11) and the possibility of a negative ion transition state is discussed. 相似文献
108.
The secondary diamine 1,3,5,7-tetrahydro[1,2c:4,5c'] benzodipyrrole (3) and 1,2,4,5-tetrabromomethylbenzene (1) form a polymeric ionene with spirane structure through a repetitive alkylation reaction. The structure of the product could be proven by13C-NMR spectroscopy by comparison with suitable reference compounds. Solutions in aqueous methanol exhibit a typical polyelectrolyte effect. Variation of the counterions produces sufficient solubility in organic solvents. From the crystal structure of a similar model compound one can conclude that the synthesized polymer has a rod-like shape. 相似文献
109.
Walter J. Jakubas Bernard C. Wentworth William H. Karasov 《Journal of chemical ecology》1993,19(10):2353-2377
Various plant secondary metabolites related to cinnamic acid are of interest because of their repellency to birds and their occurrence in ecologically important food items. Coniferyl benzoate (CB), a phenylpropanoid ester that occurs in quaking aspen (Populus tremuloides) is of particular ecological interest because of its effect on ruffed grouse (Bonasa umbellus) feeding behavior and its possible influence on the population dynamics of this bird. During detoxification processes, CB and other analogous compounds are metabolized into by-products, such as ferulic acid (FA), that can cause anti-reproductive effects. We tested whether consumption of CB produces antire-productive effects similar to FA using male and female Japanese quail (Coturnix coturnix) as avian models for ruffed grouse. The parameters we investigated included: the production, morphology, and development of eggs; reproductive characteristics influenced by estrogen; serum prolactin levels; and male reproductive behavior. Dietary CB did not produce antireproductive effects similar to FA at intake levels that Japanese quail and ruffed grouse would freely consume. Consumption of CB by Japanese quail significantly reduced egg production and body mass but did not affect male reproductive performance. Coniferyl benzoate's effect on egg production may be explained by lower energy acquisition and retention rather than endocrine changes per se. Contrary to previous reports, it is unlikely that FA, or similar compounds act directly as estrogen mimics or antagonists. Although, CB did reduce egg production in quail, it is unlikely that it would affect egg production in wild ruffed grouse. Detoxification costs and the effects of CB on nutrient utilization may explain why ruffed grouse avoid high dietary levels of CB. 相似文献
110.
Binary and ternary experimental cloud‐point curves (CPCs) for systems formulated with a low molar mass synthesized divinylester (DVE) resin, styrene (St), and poly(methyl methacrylate) (PMMA) were determined. The CPCs results were analyzed with the Flory–Huggins (F‐H) thermodynamic model taking into account the polydispersity of the DVE and PMMA components, to calculate the different binary interaction parameters and their temperature dependences. The St‐DVE system is miscible in all the composition range and down to the crystallization temperature of the St; therefore, the interaction parameter expression reported for a higher molar mass DVE was adapted. The interaction parameters obtained were used to calculate the phase diagrams of the St‐PMMA and the DVE‐PMMA binary systems and that of the St‐DVE‐PMMA ternary system at three different temperatures. Quasiternary phase diagrams show liquid–liquid partial miscibility of the St‐PMMA and DVE‐PMMA pairs. At room temperature, the St‐DVE‐PMMA system is miscible at all compositions. Final morphologies of PMMA‐modified cured St‐DVE materials were generated by polymerization‐induced phase separation (PIPS) mechanism from initial homogeneous mixtures. SEM and TEM micrographs were obtained to analyze the generated final morphologies, which showed a direct correlation with the initial miscibility of the system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4539–4549, 2006 相似文献