全文获取类型
收费全文 | 4439篇 |
免费 | 327篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 23篇 |
综合类 | 6篇 |
化学工业 | 1449篇 |
金属工艺 | 29篇 |
机械仪表 | 75篇 |
建筑科学 | 184篇 |
矿业工程 | 5篇 |
能源动力 | 92篇 |
轻工业 | 855篇 |
水利工程 | 43篇 |
石油天然气 | 16篇 |
无线电 | 218篇 |
一般工业技术 | 556篇 |
冶金工业 | 720篇 |
原子能技术 | 30篇 |
自动化技术 | 472篇 |
出版年
2024年 | 8篇 |
2023年 | 50篇 |
2022年 | 226篇 |
2021年 | 343篇 |
2020年 | 158篇 |
2019年 | 152篇 |
2018年 | 151篇 |
2017年 | 145篇 |
2016年 | 151篇 |
2015年 | 157篇 |
2014年 | 191篇 |
2013年 | 291篇 |
2012年 | 259篇 |
2011年 | 333篇 |
2010年 | 243篇 |
2009年 | 240篇 |
2008年 | 240篇 |
2007年 | 221篇 |
2006年 | 159篇 |
2005年 | 128篇 |
2004年 | 131篇 |
2003年 | 113篇 |
2002年 | 98篇 |
2001年 | 38篇 |
2000年 | 52篇 |
1999年 | 47篇 |
1998年 | 48篇 |
1997年 | 34篇 |
1996年 | 38篇 |
1995年 | 32篇 |
1994年 | 35篇 |
1993年 | 29篇 |
1992年 | 20篇 |
1991年 | 9篇 |
1990年 | 19篇 |
1989年 | 20篇 |
1988年 | 24篇 |
1987年 | 22篇 |
1986年 | 18篇 |
1985年 | 14篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 11篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1973年 | 4篇 |
1965年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有4773条查询结果,搜索用时 93 毫秒
21.
Stakeholder involvement is essential to the development of a total maximum daily load (TMDL) and its implementation plan. A tool, beyond a simulation model, is needed to support the decision making process that requires negotiation and compromise among stakeholders. The decision support system (DSS) described herein has a TMDL module to calculate various combinations of point and nonpoint loads that can meet the water quality criteria. Its Consensus module allows stakeholders to formulate, evaluate, modify, and vote for alternatives. The DSS displays bar charts for pollution loads from various subwatersheds and attributes the nonpoint loads to land uses. The water quality consequence of the pollution loads is output in maps, which shows sections meeting criteria in green and those not in red. The DSS requires a front end effort of site specific adaptation and model calibration. An Internet-based stakeholder process was developed to allow more concerned citizens to participate in management decisions. 相似文献
22.
Infinite dilution activity and diffusion coefficients of several solvents in polystyrene have been measured by inverse gas chromatographic on a capillary column for temperatures between 110 and 170°C. Chromatographic data have been treated according to Khan's model, evaluating the contribution to the peak broadening due to radial and axial molecular diffusion in the mobile phase, radial diffusion in the stationary phase, and interfacial mass transfer resistance. Four capillary columns have been prepared with coating thickness ranging from 0.5 to 3.3 microns in order to determine the minimum thickness necessary to obtain reliable measurements of the diffusion coefficient of the solvent in the polymer in every possible experimental condition. Our experimental data are in considerable agreement with the data already available in the literature, obtained by static and chromatographic methods. © 1994 John Wiley & Sons, Inc. 相似文献
23.
Waste combustion is an interesting alternative for waste management and energy recovery. Knowledge of the waste higher heating value (HHV) is important for judging it’s worth as fuel. This work introduces a new equation, based on thermochemical concepts, to calculate HHV from elemental composition. This equation is expressed in terms of mass percentages on a dry basis of carbon (%C), hydrogen (%H), oxygen (%O), nitrogen (%N), and sulfur (%S); the HHV is computed in MJ/kg. The equation is as follows: HHV=(1−(%H2O/100))(−0.3708(%C)−1.1124(%H)+0.1391(%O)−0.3178(%N)−0.1391(%S)). The thermochemical concept on which this expression is based involves a wide applicability. This equation neglects the inorganic carbon, hence it is not very adequate when there is a significant concentration of it. The predictions from this approach were contrasted against those proceeding from equations currently used in combustion technology, and also against bomb calorimeter data. The new equation is clearly competitive with respect to other formulations, and it can be very helpful for presenting a waste HHV value based on different derivation suppositions. 相似文献
24.
Laura Akers Herbert H Severson Judy A Andrews Edward Lichtenstein 《Nicotine & tobacco research》2007,9(9):907-914
This study assessed the cost-effectiveness of two low-intensity programs for quitting smokeless tobacco, based on results of a randomized trial with 1,069 volunteer participants. Cost data were collected for two levels of intervention: manual only (a self-help manual) and assisted self-help (the manual plus a videotape and two supportive phone calls from tobacco cessation counselors). Incremental cost-effectiveness ratios were calculated for assisted self-help vs. quitting on one's own, using the manual-only quit rate and data from another study as alternative proxies for no intervention. A threshold analysis was conducted to determine the spontaneous quit rate at which the manual-only intervention becomes more cost-effective than assisted self-help. The cost to provide and receive the assisted self-help intervention averaged US $56 per participant vs. $20 for the manual-only intervention (societal perspective, Year 2000 dollars). Estimates for incremental cost per quit for the assisted self-help intervention ranged from $922 to $1,758, depending on the proxy used for no intervention. The manual-only intervention was more cost-effective than assisted self-help if quitting among motivated chewers who do not receive treatment does not exceed 3.4%. Support from a wife or partner added little cost to a quit attempt for male chewers ($3-$4). Providing a manual, video, and brief phone counseling to smokeless tobacco users who want to quit is a reasonable use of health care resources. The self-help quitting guide also may be a cost-effective treatment, but it remains to be demonstrated whether it is more effective than quitting on one's own. 相似文献
25.
Self-help cessation programs for smokeless tobacco users: long-term follow-up of a randomized trial.
Hebert H Severson Judy A Andrews Edward Lichtenstein Brian G Danaher Laura Akers 《Nicotine & tobacco research》2007,9(2):281-289
This paper presents long-term outcomes of the largest clinical trial of smokeless tobacco (SLT) cessation reported to date. SLT users in five northwestern states were recruited to call a toll-free number, and 1,069 users were randomized to one of two self-help conditions: either a manual-only condition or an assisted self-help condition, which included the manual, a targeted video, and two support phone calls. Significant between-group differences were not found for either the 12- or 18-month point-prevalence measure of abstinence from either SLT only or all tobacco products using outcomes based on either the responder or intention-to-treat outcomes. However, using a repeated point-prevalence measure across all three assessment points, we found that significantly more assisted self-help participants reported abstinence, compared with manual-only participants. Compared with manual-only participants, those in the assisted self-help condition were significantly more likely to use recommended cessation techniques. Results demonstrate that low-cost, minimal interventions delivered by mail and phone can help a sizable proportion of individuals quit using SLT. 相似文献
26.
Effect of Particle Size on Monometallic and Bimetallic (Au,Pd)/C
on the Liquid Phase Oxidation of Glycerol 总被引:2,自引:0,他引:2
Nikolaos Dimitratos Jose Antonio Lopez-Sanchez David Lennon Francesca Porta Laura Prati Alberto Villa 《Catalysis Letters》2006,108(3-4):147-153
The influence of metal particle size of monometallic and bimetallic supported catalysts (Au, Pd, Au–Pd)/C was studied using
as a model reaction the liquid phase oxidation of glycerol. By tuning the metal particle size from 2 to 16 nm a progressive
decrease of activity and simultaneously an increase in the selectivity to sodium glycerate was observed. Moreover, the influence
of the temperature was studied and it was found that by increasing the temperature, only with a large particle size the formed
glycerate was retained and not over-oxidized to tartronate. 相似文献
27.
Kaarina Aarnisalo Kaija Tallavaara Gun Wirtanen Riitta Maijala Laura Raaska 《Food Control》2006,17(12):1001-1011
The hygienic working practices of the maintenance personnel as well as the hygiene of the equipment in the food industry were investigated with questionnaires and microbial surveys. The protective clothing, washing of hands and tools as well as avoiding foreign bodies left on the production lines should be targeted when the hygienic working practices are developed for maintenance personnel. Based on the questionnaire to food processors, packaging machines, conveyers, dispensers, slicing and cooling machines were considered the most problematic pieces of equipment hygienically mainly because of poor hygienic design. In order to improve food safety, both the training of maintenance personnel in food hygiene and equipment design should be more emphasised. 相似文献
28.
Detecting Deception in Children: Event Familiarity Affects Criterion-Based Content Analysis Ratings.
29.
This study investigated whether sex discrimination existed in recruiters' evaluations of applicants in real employment interviews and, if so, whether other variables could explain it. The variables examined were the perceived similarity of the applicant to the recruiter, the interpersonal attraction felt by the recruiter toward the applicant, and the applicant's objectively measured and subjectively measured qualifications. Applicant sex did not directly or indirectly affect recruiters' evaluations of applicants in campus interviews, providing no evidence of sex discrimination. Instead, subjective qualifications had a significant effect on evaluations and also mediated the effects of perceived similarity, interpersonal attraction, and objective qualifications on evaluations. Recruiters saw stronger subjective qualifications in applicants with high scholastic performance whom they viewed as similar to themselves and whom they liked. Perceptions of these qualifications, in turn, were the primary determinant of evaluations. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
30.
Castonguay Louis G.; Schut Alexander J.; Aikens Deane E.; Constantino Michael J.; Laurenceau Jean-Philippe; Bologh Laura; Burns David D. 《Canadian Metallurgical Quarterly》2004,14(1):4
This study is a preliminary investigation of an integrative treatment aimed at improving the efficacy of cognitive therapy (CT) for depression. The development of the treatment protocol was based on process findings, which suggested that strategies used in CT to resolve alliance ruptures may actually exacerbate problems in the therapeutic relationship. The protocol integrates, within the traditional CT treatment manual, procedures to repair alliance ruptures that are derived from or consistent with humanistic and interpersonal therapies. Although conducted by inexperienced therapists, the integrative treatment led to greater improvement than a waiting-list condition. The results also compare favorably to previous findings for CT. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献