全文获取类型
收费全文 | 13173篇 |
免费 | 564篇 |
国内免费 | 48篇 |
专业分类
电工技术 | 139篇 |
综合类 | 23篇 |
化学工业 | 2522篇 |
金属工艺 | 237篇 |
机械仪表 | 233篇 |
建筑科学 | 864篇 |
矿业工程 | 47篇 |
能源动力 | 351篇 |
轻工业 | 1028篇 |
水利工程 | 162篇 |
石油天然气 | 52篇 |
武器工业 | 1篇 |
无线电 | 896篇 |
一般工业技术 | 2384篇 |
冶金工业 | 2571篇 |
原子能技术 | 58篇 |
自动化技术 | 2217篇 |
出版年
2023年 | 70篇 |
2022年 | 141篇 |
2021年 | 233篇 |
2020年 | 167篇 |
2019年 | 185篇 |
2018年 | 263篇 |
2017年 | 216篇 |
2016年 | 328篇 |
2015年 | 252篇 |
2014年 | 402篇 |
2013年 | 839篇 |
2012年 | 665篇 |
2011年 | 903篇 |
2010年 | 691篇 |
2009年 | 640篇 |
2008年 | 757篇 |
2007年 | 751篇 |
2006年 | 615篇 |
2005年 | 584篇 |
2004年 | 503篇 |
2003年 | 396篇 |
2002年 | 472篇 |
2001年 | 287篇 |
2000年 | 275篇 |
1999年 | 236篇 |
1998年 | 246篇 |
1997年 | 219篇 |
1996年 | 184篇 |
1995年 | 231篇 |
1994年 | 189篇 |
1993年 | 196篇 |
1992年 | 162篇 |
1991年 | 78篇 |
1990年 | 138篇 |
1989年 | 122篇 |
1988年 | 112篇 |
1987年 | 116篇 |
1986年 | 84篇 |
1985年 | 139篇 |
1984年 | 130篇 |
1983年 | 83篇 |
1982年 | 67篇 |
1981年 | 64篇 |
1980年 | 46篇 |
1979年 | 55篇 |
1978年 | 42篇 |
1977年 | 27篇 |
1976年 | 35篇 |
1974年 | 25篇 |
1973年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
Erp Implementation Failure: A Case Study 总被引:5,自引:0,他引:5
While it is true that successful implementation of an enterprise resource planning (ERP) system is a task of Herculean proportions, it is not impossible. If your organization is to reap the benefits of ERP, it must first develop a plan for success. But “prepare to see your organization reengineered, your staff disrupted, and your productivity drop before the payoff is realized.” Implementing ERP must be viewed and undertaken as a new business endeavor and a team mission, not just a software installation. Companies must involve all employees, and unconditionally and completely sell them on the concept of ERP for it to be a success. A successful implementation means involving, supervising, recognizing, and retaining those who have worked or will work closely with the system. Without a team attitude and total backing by everyone involved, an ERP implementation will end in less than an ideal situation. This was the situation for a soft drink bottler that tried to cut corners and did not recognize the importance of the people so heavily involved and depended on. 相似文献
62.
Myers Mark G.; MacPherson Laura; McCarthy Denis M.; Brown Sandra A. 《Canadian Metallurgical Quarterly》2003,15(2):163
The goal of the present studies was to construct and validate a short form of the 50-item Smoking Consequences Questionnaire (SCQ; T. H. Brandon & T. B. Baker, 1991), a measure of smoking outcome expectancies. In Study 1, a 21-item short form (S-SCQ) was derived from a sample of 107 young adults previously treated for substance abuse. In Study 2, the measure was cross-validated on 125 adolescents in treatment for substance abuse. Confirmatory factor analyses revealed good model fit and factorial invariance for the 4 S-SCQ subscales across both samples. Validation analyses on each sample found that subscale scores generally correlated significantly with smoking-related variables. The present studies provide initial evidence for the utility of the S-SCQ when used with young adults and adolescents. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
63.
A wireless LAN service integration architecture based on current wireless LAN hot spots is proposed so that migration to a new service becomes easier and cost effective. The proposed architecture offers wireless LAN seamless roaming in wireless LAN/cellular mobile networks. In addition, a link-layer-assisted mobile IP handoff mechanism is introduced to improve the network/domain switching quality in terms of handoff delay and packet loss. An application layer end-to-end authentication and key negotiation scheme is proposed to overcome the open-air connection problem existing in wireless LAN deployment. The scheme provides a general solution for Internet applications running on a mobile station under various authentication scenarios and keeps the communications private to other wireless LAN users and foreign network. A functional demonstration of the scheme is given. The research results can contribute to rapid deployment of wireless LANs. 相似文献
64.
Gilden David L.; Schmuckler Mark A.; Clayton Keith 《Canadian Metallurgical Quarterly》1993,100(3):460
The observation that natural curves and surfaces are often fractal suggests that people may be sensitive to their statistical properties. The perceptual protocols that underlie discrimination between fractals and between other types of random contour and fractals are examined. Discrimination algorithms that have precisely the same sensitivities as human observers are constructed. These algorithms do not recognize the integrated scale hierarchy intrinsic to fractal form and operate by imposing a metatheory of structure that is based on a signal–noise distinction. The success of the algorithms implies that (1) self-affinity in random fractals is not perceptually recovered and (2) people have a natural disposition to view contour in terms of signal and noise. The authors propose that this disposition be understood as a principle of perceptual organization. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
65.
J Barrette R Bellwied P Braun-Munzinger WE Cleland T Cormier G Dadusc G David J Dee O Dietzsch M Fatyga SV Greene JV Germani JR Hall TK Hemmick N Herrmann RW Hogue B Hong K Jayananda D Kraus BS Kumar R Lacasse D Lissauer WJ Llope TW Ludlam R Majka SK Mark JT Mitchell M Muthuswamy E O'Brien C Pruneau FS Rotondo da Silva NC J Simon-Gillo U Sonnadara J Stachel H Takai EM Takagui TG Throwe L Waters C Winter D Wolfe CL Woody N Xu Y Zhang Z Zhang C Zou 《Canadian Metallurgical Quarterly》1995,52(5):2679-2683
66.
DC Sutton R Kluger SU Ahmed SC Reimold JB Mark 《Canadian Metallurgical Quarterly》1994,108(3):576-582
This study assessed the value of biplane transesophageal echocardiographic assessment of diastolic flow reversal in the descending aorta as an alternative to Doppler color flow imaging in determining severity of aortic regurgitation. In 45 patients undergoing cardiac operations, the severity of aortic regurgitation was assessed by semiquantitative grading of the width of the Doppler color flow regurgitant jet relative to the left ventricular outflow tract, and the presence of diastolic flow reversal was assessed with pulsed-wave Doppler measurements at three sites in the descending aorta. In four patients, the diastolic flow reversal method was the only available form of assessment because of inadequate visualization of the left ventricular outflow tract beneath a mitral valve prosthesis. Diastolic flow reversal in the descending aorta was not observed in patients without aortic regurgitation and was always present in patients with severe aortic regurgitation. Aortic valve replacement successfully eliminated descending aortic flow reversal in all 19 patients in whom it was present before valve replacement. Identification of diastolic flow reversal at multiple sites in the descending aorta with biplane transesophageal echocardiography helps to confirm the presence of severe aortic regurgitation and can serve as an alternative method of assessment when visualization of the left ventricular outflow tract is impaired. 相似文献
67.
68.
Roger Norman Rothon Christopher Mark Liauw Graham Clayton Lees Wayne Christopher Edward Schofield 《The Journal of Adhesion》2002,78(7):603-628
The interaction of ammonium stearate (AS) and γ-aminopropyltriethoxysilane (APS) treatments with a magnesium hydroxide flame retardant filler and their effects on its use in an ethylene vinyl acetate copolymer compound have been investigated. The work has shown clear evidence of changes in the structure of the surface layers formed on the filler as the amount of additive is increased and the levels at which these occur can be correlated with theoretical monolayer quantities. Infrared (IR) spectroscopy data suggest that the stearate coating changes from a half salt to a full salt as the coating level is increased and that the APS coating on the filler initially has a significant bicarbonate content, presumably due to reaction with atmospheric carbon dioxide. The effect of coating level on the melt flow rate, insoluble matrix content, crystallisation behaviour, tensile properties, limiting oxygen index, and ageing of the filled compound has been studied. Distinct trends have been observed, many of which can be correlated with the structure of the filler surface layers. Of particular importance is the observation that, unlike APS, excess stearate appears to promote detrimental ageing effects. 相似文献
69.
Examined the effect of lesions of the caudate nucleus or fimbria-fornix on the acquisition of 2 water maze tasks. In both tasks, 2 rubber balls with different visual patterns were used as cues. The correct cue was attached to a submerged rectangular platform and could be mounted by an animal to escape the water. The incorrect cue was attached to a thin round pedestal and could not be mounted. In a spatial version of the task, the correct cue was located in the same quadrant of the maze on all trials, whereas the visual pattern on the cue was varied from trial to trial. Lesions of the fornix, but not the caudate nucleus, impaired acquisition of this spatial task in relation to control animals. In a simultaneous visual discrimination version of the task, the correct cue on all trials was one with a specific visual pattern, and the spatial location of the correct cue was varied from trial to trial. Lesions of the caudate nucleus, but not the fornix, impaired acquisition of this visual discrimination task in relation to control animals. The double dissociation observed supports the hypothesis that the hippocampus and caudate nucleus are parts of systems that differ in the type of memory they mediate. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
70.