全文获取类型
收费全文 | 5129篇 |
免费 | 360篇 |
国内免费 | 19篇 |
专业分类
电工技术 | 39篇 |
综合类 | 2篇 |
化学工业 | 1064篇 |
金属工艺 | 97篇 |
机械仪表 | 116篇 |
建筑科学 | 249篇 |
矿业工程 | 10篇 |
能源动力 | 160篇 |
轻工业 | 409篇 |
水利工程 | 68篇 |
石油天然气 | 17篇 |
无线电 | 407篇 |
一般工业技术 | 1252篇 |
冶金工业 | 721篇 |
原子能技术 | 9篇 |
自动化技术 | 888篇 |
出版年
2024年 | 9篇 |
2023年 | 58篇 |
2022年 | 97篇 |
2021年 | 171篇 |
2020年 | 144篇 |
2019年 | 147篇 |
2018年 | 170篇 |
2017年 | 160篇 |
2016年 | 199篇 |
2015年 | 156篇 |
2014年 | 252篇 |
2013年 | 336篇 |
2012年 | 396篇 |
2011年 | 490篇 |
2010年 | 310篇 |
2009年 | 260篇 |
2008年 | 343篇 |
2007年 | 301篇 |
2006年 | 255篇 |
2005年 | 209篇 |
2004年 | 165篇 |
2003年 | 133篇 |
2002年 | 144篇 |
2001年 | 87篇 |
2000年 | 64篇 |
1999年 | 42篇 |
1998年 | 46篇 |
1997年 | 42篇 |
1996年 | 39篇 |
1995年 | 27篇 |
1994年 | 35篇 |
1993年 | 29篇 |
1992年 | 22篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 17篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 11篇 |
1985年 | 15篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 6篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 13篇 |
1975年 | 4篇 |
1973年 | 3篇 |
排序方式: 共有5508条查询结果,搜索用时 15 毫秒
11.
Ahluwalia Jasjit S.; Nollen Nicole; Kaur Harsohena; James Aimee S.; Mayo Matthew S.; Resnicow Ken 《Canadian Metallurgical Quarterly》2007,26(2):214
Objectives: Examine the effectiveness of an intervention to increase fruits and vegetables (FV) consumption among smokers. Design: Cluster-randomized trial of 20 public housing developments; 10 randomly assigned to an FV intervention and 10 to a smoking cessation intervention. Main outcome measures: Usual (past 7 days) and past 30 days change in daily FV intake at 8 weeks and 6 months postbaseline. Results: Greater increases were seen in the FV group. At Week 8 and Month 6, the FV group had consumed 1.58 (p = .001) and 0.78 (p = .04), respectively, more daily FV servings in the past 7 days than the cessation group. At the same time points, the FV group had consumed 3.61 (p = .01) and 3.93 (p = .01), respectively, more FV servings in the past 30 days than the cessation group. Completing more motivational interviewing sessions (p = .02) and trying more recipes (p = .02) led to significantly greater increases at Month 6 among FV participants. Conclusions: Motivational interviewing counseling and lifestyle modification through trying out healthy recipes may be effective in helping a high-risk population increase their FV intake. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
12.
Matthew John M. Krane Frank P. Incropera 《Metallurgical and Materials Transactions A》1995,26(9):2329-2339
Numerical calculations based on a continuum model are used to examine the effects of solidification shrinkage on the redistribution
of solute in a Pb-19.2 pct Sn mixture which is convectively cooled at a sidewall. For each of three different cooling rates,
separate calculations are performed for shrinkage and buoyancy-induced flows, as well as for the combined influence of shrinkage
and buoyancy effects. The calculations reveal that flow and macrosegregation patterns are more strongly influenced by buoyancy
effects over a wide range of solidification rates. Although extremely large solidification rates yield small regions near
the chilled wall in which shrinkage-induced flows control the redis-tribution of solute, the overall effect on macrosegregation
is small relative to that associated with buoyancy. Scaling analysis of the governing equations produces reference shrinkage
and buoyancy velocities which can be used to extend the current numerical results to other binary systems. 相似文献
13.
Zhufang Liu Mohammad Shamsuzzoha Earl T. Ada W. Matthew Reichert David E. Nikles 《Journal of power sources》2007
Well-dispersed Pt nanoparticles with controlled size and narrow size distribution were prepared by polyalcohol reduction of platinum acetylacetonate, using oleylamine as a capping agent. The particle size was varied from 3.5 nm to 11.5 nm by decreasing the amount of oleylamine added in the synthesis. Size selection of the as-prepared particles by solvent fractionation yielded nearly monodispersed Pt particles. The as-prepared particles were loaded on a carbon support by physical deposition, but showed no electrocatalytic activity due to the oleylamine bound to the particle surface. The particles were activated for electrocatalysis after heating the particles in air at 185 °C for 5 h, conditions that gave no particle-sintering and no oxidation. Cyclic voltammetry showed that the particles after the heat treatment in air were electrocatalytically active for methanol oxidation. The smaller 3.5 nm and 4.0 nm Pt particles had a higher intrinsic activity for methanol oxidation, but a lower tolerance to CO poisoning, compared with 6.0 nm, 9.5 nm and 11.5 nm particles. CO-stripping results suggest that CO is more easily oxidized on larger Pt particles. 相似文献
14.
Tabletability of five types of maltodextrin, a filler/binder excipient, was studied by testing their loading potentials with acetaminophen. The formulations consisted of excipient and acetaminophen at five different ratios and magnesium stearate at a 0.5% concentration. These mixtures were compacted employing an Integrated Compaction Research System at a constant punch velocity of 100 mm/sec. under varying applied pressures from 50 to 450 MPa. Compaction data were evaluated using the total work of compaction vs applied pressure plots whilst the post-compaction tests included the measurements of crushing force, disintegration time, and friability of the resulting tablets. Both the energy involved during the compaction of a formulation and the crushing force values of the resulting tablets decreased as the amount of the maltodextrin in a formulation was reduced. Maltodextrins exhibited adequate binding potential at acetaminophen drug loading levels of only up to twenty-five percent. The disintegration times of the tablets containing maltodextrins were generally prolonged and this was found to be due to the formation of a “gel” layer around the tablet which formed on immersion into water. The tabletability of maltodextrins were also compared to that of Fast-Flo lactose, and the compactability of these excipients were found to be similar. 相似文献
15.
16.
Forster Jean L.; Jeffery Robert W.; Schmid Thomas L.; Kramer F. Matthew 《Canadian Metallurgical Quarterly》1988,7(6):515
Evaluated the feasibility and effectiveness of a program for weight gain prevention (WGP) in normal adults. 219 Ss were randomized to either WGP treatment or no treatment for 12 mo. The treatment group received monthly newsletters relating to weight management, participated in a financial incentive system, and were offered an optional 4-session education course in the 6th mo of the program. Results demonstrate high interest in WGP among Ss who were not objectively overweight. Participation, as measured by return of postcards sent with each newsletter, was approximately 75%. Results after 1 yr show a net weight loss of 1.8 lb in the group receiving the program compared with controls. 82% of participants maintained or lost weight, compared with 56% of controls. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
17.
Matthew N. Ashby Patrick R. Errada Victor L. Boyartchuk Jasper Rine 《Yeast (Chichester, England)》1993,9(8):907-913
We isolated a mutant defective in C-terminal farnesyl cysteine:carboxyl methyltransferase activity from a screen for mutations causing a -specific sterility. A genomic fragment was cloned from a yeast multi-copy library that restored mating. Both the cloned gene and the sterile mutation were allelic to the STE14 gene. A ste14-complementing 2·17 kb BamHI fragment subclone was sequenced and found to encode a 239 amino acid protein with a molecular weight of 27,887 Daltons. The hydrophobicity profile of the methyltransferase reveals the presence of at least five potential transmembrane domains. In comparisons of the C-terminal methyltransferase amino acid sequence with those in the PIR and Swiss protein databases, no significantly similar sequences were found nor were conserved regions from other methyltransferases present. 相似文献
18.
19.
Examined publishing practices of the American Psychological Association (APA) in the alcohol and drug area. Although the total number of articles published by APA increased only 7.6% between 1984 and 1990, the number of alcohol and drug articles more than doubled. Despite the disproportionate growth of alcohol and drug articles between 1984 and 1990, only 3.8% of 1,408 APA articles published in 1990 addressed alcohol and drug use issues. An earlier investigation by M. O. Howard and D. A. Howard (1992) reported that 541 articles published in 1984 in 12 alcohol and drug specialty journals received an average of 3.48 citations by the end of 1988. Alcohol and drug articles published by APA in 1984 received more than 4 times as many citations during this period. Also, alcohol and drug articles published by APA received significantly more citations between 1984 and 1988 than those published in specialty journals. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
20.