全文获取类型
收费全文 | 1354篇 |
免费 | 76篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 26篇 |
综合类 | 29篇 |
化学工业 | 345篇 |
金属工艺 | 32篇 |
机械仪表 | 26篇 |
建筑科学 | 81篇 |
矿业工程 | 14篇 |
能源动力 | 19篇 |
轻工业 | 260篇 |
水利工程 | 18篇 |
石油天然气 | 9篇 |
无线电 | 72篇 |
一般工业技术 | 218篇 |
冶金工业 | 104篇 |
原子能技术 | 12篇 |
自动化技术 | 170篇 |
出版年
2024年 | 3篇 |
2023年 | 19篇 |
2022年 | 48篇 |
2021年 | 65篇 |
2020年 | 32篇 |
2019年 | 27篇 |
2018年 | 47篇 |
2017年 | 41篇 |
2016年 | 53篇 |
2015年 | 47篇 |
2014年 | 51篇 |
2013年 | 84篇 |
2012年 | 68篇 |
2011年 | 114篇 |
2010年 | 63篇 |
2009年 | 65篇 |
2008年 | 89篇 |
2007年 | 68篇 |
2006年 | 45篇 |
2005年 | 54篇 |
2004年 | 37篇 |
2003年 | 37篇 |
2002年 | 23篇 |
2001年 | 23篇 |
2000年 | 14篇 |
1999年 | 21篇 |
1998年 | 30篇 |
1997年 | 15篇 |
1996年 | 21篇 |
1995年 | 14篇 |
1994年 | 9篇 |
1993年 | 13篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 7篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 8篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1932年 | 1篇 |
1922年 | 1篇 |
1914年 | 1篇 |
1912年 | 3篇 |
排序方式: 共有1435条查询结果,搜索用时 0 毫秒
71.
72.
U. Götze Th. Weber C. Linke A. Schmidt 《Materialwissenschaft und Werkstofftechnik》2009,40(7):566-572
Target Costing for Materials – Potentialities and Methodology Target Costing is a standard instrument of cost management in business administration, but hardly mentioned in the economic oriented literature on material sciences. Nevertheless there are high potentialities for developers, producers, or users of materials regarding the improvement of efficiency. Therefore, this article will present these potentialities of a material oriented Target Costing. Besides, the general methodology of Target Costing will be modified to meet the specifics of materials from the perspectives of users of materials on the one hand and developers respectively producers of materials on the other. 相似文献
73.
74.
75.
Preeti Mani Natthapon Nakpathomkun Heiner Linke 《Journal of Electronic Materials》2009,38(7):1163-1165
The Seebeck coefficient S is an important performance characteristic of thermoelectric materials. In this paper we establish the fact that quantum
dots and single-electron tunneling devices with narrow, well-spaced energy levels and sharp transmission resonances have a
Seebeck coefficient independent of material parameters. By employing a delta function for the transmission resonances we arrive
at an intrinsic expression for S in terms of the fundamental electronic charge e. We further confirm the validity of our result in the case of a transmission resonance with finite width. 相似文献
76.
Per Carlbring Sara Brunt Susanne Bohman David Austin Jeffrey Richards Lars-Göran Öst Gerhard Andersson 《Computers in human behavior》2007
The aim of this study was to investigate the psychometric properties of Internet administered questionnaires used in panic research. Included were 494 people who had registered for an Internet-based treatment program for panic disorder (PD). Participants were randomly assigned to fill in the questionnaires either on the Internet or the paper-and-pencil versions, and then to fill in the same questionnaires again the next day using the other format. The questionnaires were the body sensations questionnaire [BSQ; Chambless, D. L., Caputo, G. C., Bright, P., & Gallagher, R. (1984). Assessment of fear of fear in agoraphobics: the body sensations questionnaire and the agoraphobic cognitions questionnaire. Journal of Consulting and Clinical Psychology, 52, 1090–1097], agoraphobic cognitions questionnaire [ACQ; Chambless, D. L., Caputo, G. C., Bright, P., & Gallagher, R. (1984). Assessment of fear of fear in agoraphobics: the body sensations questionnaire and the agoraphobic cognitions questionnaire. Journal of Consulting and Clinical Psychology, 52, 1090–1097], mobility inventory [MI; Chambless, D. L., Caputo, G., Jasin, S., Gracely, E. J., & Williams, C. (1985). The mobility inventory for agoraphobia. Behaviour Research and Therapy, 23, 35–44], beck anxiety inventory [BAI; Beck, A. T., Epstein, N., Brown, G., & Steer, R. A. (1988). An inventory for measuring clinical anxiety: psychometric properties. Journal of Consulting and Clinical Psychology, 56, 893–897], beck depression inventory II [Beck, A. T., & Steer, R. A. (1996). Beck Depression Inventory. Manual, Svensk version (Swedish version). Fagernes, Norway: Psykologiförlaget, AB], quality of life inventory [QOLI; Frisch, M. B., Cornell, J., Villanueva, M., & Retzlaff, P. J. (1992). Clinical validation of the quality of life inventory. A measure of life satisfaction for use in treatment planning and outcome assessment. Psychological Assessment, 4, 92–101], and montgomery Åsberg depression rating scale [MADRS; Svanborg, P., & Åsberg, M. (1994). A new self-rating scale for depression and anxiety states based on the comprehensive psychopathological rating scale. ACTA Psychiatrica Scandinavica, 89, 21–28]. Results showed largely equivalent psychometric properties for the two administration formats (Cronbach’s α between 0.79 and 0.95). The results also showed high and significant correlations between the Internet and the paper-and-pencil versions. Analyses of order effects showed an interaction effect for the BSQ and the MI (subscale Accompanied), a main effect was identified for ACQ, MI-Alone, BAI and BDI II. However, in contrast to previous research, the Internet version did not consistently generate higher scores and effect sizes for the differences were generally low. Given the presence of an interaction effect, we recommend that the administration format should be stable in research across measurement points. Finally, the findings suggest that Internet versions of questionnaires used in PD research can be used with confidence. 相似文献
77.
Frese Michael; Krauss Stefanie I.; Keith Nina; Escher Susanne; Grabarkiewicz Rafal; Luneng Siv Tonje; Heers Constanze; Unger Jens; Friedrich Christian 《Canadian Metallurgical Quarterly》2007,92(6):1481
A model of business success was developed with motivational resources (locus of control, self-efficacy, achievement motivation, and self-reported personal initiative) and cognitive resources (cognitive ability and human capital) as independent variables, business owners' elaborate and proactive planning as a mediator, and business size and growth as dependent variables. Three studies with a total of 408 African micro and small-scale business owners were conducted in South Africa, Zimbabwe, and Namibia. Structural equation analyses partially supported the hypotheses on the importance of psychological planning by the business owners. Elaborate and proactive planning was substantially related to business size and to an external evaluation of business success and was a (partial) mediator for the relationship between cognitive resources and business success. The model carries important implications for selection, training, and coaching of business owners. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
78.
Kern S Singer H Hollender J Schwarzenbach RP Fenner K 《Environmental science & technology》2011,45(7):2833-2841
Transformation products (TPs) of chemicals released to soil, for example, pesticides, are regularly detected in surface and groundwater with some TPs even dominating observed pesticide levels. Given the large number of TPs potentially formed in the environment, straightforward prioritization methods based on available data and simple, evaluative models are required to identify TPs with a high aquatic exposure potential. While different such methods exist, none of them has so far been systematically evaluated against field data. Using a dynamic multimedia, multispecies model for TP prioritization, we compared the predicted relative surface water exposure potential of pesticides and their TPs with experimental data for 16 pesticides and 46 TPs measured in a small river draining a Swiss agricultural catchment. Twenty TPs were determined quantitatively using solid-phase extraction liquid chromatography mass spectrometry (SPE-LC-MS/MS), whereas the remaining 26 TPs could only be detected qualitatively because of the lack of analytical reference standards. Accordingly, the two sets of TPs were used for quantitative and qualitative model evaluation, respectively. Quantitative comparison of predicted with measured surface water exposure ratios for 20 pairs of TPs and parent pesticides indicated agreement within a factor of 10, except for chloridazon-desphenyl and chloridazon-methyl-desphenyl. The latter two TPs were found to be present in elevated concentrations during baseflow conditions and in groundwater samples across Switzerland, pointing toward high concentrations in exfiltrating groundwater. A simple leaching relationship was shown to qualitatively agree with the observed baseflow concentrations and to thus be useful in identifying TPs for which the simple prioritization model might underestimate actual surface water concentrations. Application of the model to the 26 qualitatively analyzed TPs showed that most of those TPs categorized as exhibiting a high aquatic exposure potential could be confirmed to be present in the majority of water samples investigated. On the basis of these results, we propose a generally applicable, model-based approach to identify those TPs of soil-applied organic contaminants that exhibit a high aquatic exposure potential to prioritize them for higher-tier, experimental investigations. 相似文献
79.
A method is presented that permits the determination of the cloud effective particle size from Raman- or Rayleigh-integration temperature measurements that exploits the dependence of the multiple-scattering contributions to the lidar signals from heights above the cloud on the particle size of the cloud. Independent temperature information is needed for the determination of size. By use of Raman-integration temperatures, the technique is applied to cirrus measurements. The magnitude of the multiple-scattering effect and the above-cloud lidar signal strength limit the method's range of applicability to cirrus optical depths from 0.1 to 0.5. Our work implies that records of stratosphere temperature obtained with lidar may be affected by multiple scattering in clouds up to heights of 30 km and beyond. 相似文献
80.
Carbon thermograms, which classify carbon aerosol according to its volatility, were obtained for fine-particle samples from an isolated highway vehicle source and a vehicle-dominated ambient site. The thermograms from the sites were compared after scaling by the carbon monoxide concentration. The high- and low-volatility carbon fractions in the ambient sample agreed to within 10% of the corresponding fractions in the highway vehicle sample. Excess carbon in the range of intermediate volatility comprised 15 to 19% of the ambient carbon mass and is attributed to aerosols from secondary processes and nonvehicular primary sources. When lead was used as a tracer to scale the thermograms, the high- and low-volatility ambient carbon fractions were underestimated by a factor of 2. The low volatility fraction (“black carbon”) present in the atmospheric sample was evolved at lower temperatures than the equivalent fraction in the isolated highway vehicle sample. This creates an ambiguity in defining the low-volatility fraction, which is a problem if black carbon is used as a tracer. The scaling technique described in this work avoids the problem because it does not require an estimation of the low-volatility carbon fraction. 相似文献