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排序方式: 共有8216条查询结果,搜索用时 15 毫秒
1.
Gérald Guérin 《Polymer》2003,44(24):7477-7484
The bonding of polystyrene (PS) surfaces below Tg was investigated by two different fracture tests: the lap-shear joint method and the cantilever beam method. Adhesion energy values obtained by the two methods are in agreement and develop with (time)1/2, at temperatures as low as Tg−16 °C. Even if the double cantilever method is the most common test found in the literature for adhesions above Tg, for low adhesion values, below Tg, the lap-shear joint geometry is more appropriate. Moreover, when the glass transition temperature is used as a reference temperature, polydisperse and monodisperse PS adhesion energy curves are superposable, suggesting that the auto-adhesion is not significantly favored by the presence of numerous chain ends at the surface (due to the low molecular weight chains provided by the polydisperse PS). 相似文献
2.
着重研究了马克思主义执政党建设如何应对当代世界政党政治的执政文化转型问题,认为应当正确认识和处理马克思主义执政党建设与当代世界政党政治的关系,深入研究世界上其他执政党治国理政的成功经验和有益做法,不断提高马克思主义执政党的执政能力和科学化水平。 相似文献
3.
Jason P. Petti 《Engineering Fracture Mechanics》2005,72(1):91-120
This work proposes that the Weibull stress scale parameter, σu, increases with temperature to reflect the increasing microscale toughness of ferritic steels caused by local events that include plastic shielding of microcracks, microcrack blunting, and microcrack arrest. The Weibull modulus, m, then characterizes the temperature invariant, random distribution of microcrack sizes in the material. Direct calibration of σu values at temperatures over the DBT region requires extensive sets of fracture toughness values. A more practical approach developed here utilizes the so-called Master Curve standardized in ASTM Test Method E1921-02 to provide the needed temperature vs. toughness dependence for a material using a minimum number of fracture tests conducted at one temperature. The calibration procedure then selects σu values that force the Weibull stress model to predict the Master Curve temperature dependence of KJc values for the material. At temperatures in mid-to-upper transition, the process becomes more complex as fracture test specimens undergo gradual constraint loss and the idealized conditions of high-constraint, small-scale yielding assumed in E1921-02 gradually degenerate. The paper develops the σu calibration process to incorporate these effects in addition to consideration of threshold toughness effects and the testing of fracture specimens with varying crack-front lengths. Initial illustrations of the calibration process for simpler conditions, i.e. 1T crack-front lengths, use the temperature dependent flow properties and a range of toughness levels for an A533B pressure vessel steel. Then using the extensive fracture toughness data sets for an A508 pressure vessel steel generated recently by Faleskog et al. [Engng. Fract. Mech., in press], the paper concludes with calibrations of both m and σu over the DBT region and assessments of the Master Curve calibration approach developed here. 相似文献
4.
文章讨论了美国杰出的马克思主义批评家詹明信在全球资本主义的历史背景中,如何阐述库哈斯的建筑,他的建筑与后现代主义建筑之间有何差异,这种差异如何形成并给出有意义的诠释。 相似文献
5.
Jane Clary Marcus Quigley Aaron Poresky Andrew Earles Eric Strecker Marc Leisenring Jonathan Jones 《Canadian Metallurgical Quarterly》2011,137(3):190-198
Low impact development (LID) strategies are being encouraged in many communities as an approach to reduce potential adverse impacts of development on receiving streams. Many questions exist regarding how well various LID strategies perform in different settings, just as similar questions have been raised regarding performance of traditional stormwater best management practices (BMPs). Whereas historical focus on BMP performance has been water quality concentrations or loads, characterization of volume reduction benefits for both conventional and LID practices is increasingly an objective of researchers and stormwater managers. More than a decade ago, Urban Water Resources Research Council (UWRRC) members worked to develop a set of standardized monitoring and reporting protocols for traditional BMPs and to establish a master database for the purpose of evaluating BMP performance and the factors affecting performance. This effort culminated in the International Stormwater BMP Database (www.bmpdatabase.org), which contains data for more than 360 BMPs and continues to operate as a clearinghouse for stormwater BMP data and performance analyses. During 2008–2009, the International Stormwater BMP Database project expanded to better integrate LID into the database and develop a set of metrics that can be used to characterize BMP performance with regard to surface runoff volume reduction. This paper provides a condensed overview and progress report on the LID-focused effort, including the following topics: (1)?monitoring guidance for LID at the overall site development level, (2)?an overview of recent changes to the International Stormwater BMP Database to better accommodate LID studies, (3)?a summary of LID studies currently included in the database, and (4)?a proposed approach for evaluating performance of LID studies with regard to reducing surface runoff volumes. 相似文献
6.
This paper presents the results of a comparative study aiming to investigate the effect of reflective coatings on lowering surface temperatures of buildings and other surfaces of the urban environment, and thus test their suitability to lower ambient temperatures and fight the heat island effect. In total, 14 types of reflective coatings, selected from the international market were studied, from August to October 2004, on a 24 h basis. These coatings are used in buildings and some of them are used or could be used in the future in other surfaces of the urban environment (sidewalks, parking lots, etc.). In order to investigate the thermal performance of the reflective coatings, surface temperature sensors and a data logging system as well as infrared thermography procedures were used. The spectral reflectance and the infrared emittance of the samples were also measured. The collected data have been extensively analyzed. It was demonstrated that the use of reflective coatings can reduce a white concrete tile’s surface temperature under hot summer conditions by 4 °C and during the night by 2 °C. It can be warmer, than the ambient air by only 2 °C during the day and cooler than the ambient air by 5.9 °C during the night. “Cool” coatings present superior thermal performance even compared to other “cool” materials. This study can assist in choosing more appropriate coatings for building envelopes and other surfaces of the urban environment, and thus contribute to the mitigation of the heat island effect as well as the reduction of cooling loads and electricity consumption of buildings. 相似文献
7.
Observations of high temperature impinging-jet boiling phenomena 总被引:1,自引:0,他引:1
Peter Lloyd Woodfield Masanori Monde Aloke Kumar Mozumder 《International Journal of Heat and Mass Transfer》2005,48(10):2032-2041
A high-speed video camera and microphone were used to capture the flow behavior and boiling sound of a free-surface water jet impinging on a high temperature surface during quench cooling. It was found that depending on the superheat of the surface considerably different flow patterns appeared. For cases where the initial surface temperature was above about 300 °C an almost explosive pattern appeared. This was in contrast to slightly lower temperatures where a liquid sheet flow structure was apparent. The change in phenomena was accompanied by a sudden change in the boiling sound and an increase in the heat transfer rate. 相似文献
8.
随着城市经济建设和市政功能日臻完善的发展趋势,提出了以网格化概念,规范城市(公用)配电网络的建设和发展,并由此化解目前配电生产组织、营业收费管理以及市政改造发展中的诸多矛盾,为逐步实现城市配电供电高可靠性目标打好基础。 相似文献
9.
A new approach using input-output techniques is proposed for the analysis of urban stormwater pollution caused by urban land development. The input-output model provides projections of sectoral outputs within an urban region. By defining land as an input to production, these output projections may be translated into projections of commercial and industrial land development. Furthermore, the closed version of the input-output model is used to project residential land development as a function of projected wage income. The pollutant generation in urban stormwater is related to the quantity of each category of land development by a pollutant coefficient matrix. Thus, the model can be used to predict the impact of various economic growth scenarios on pollution loadings in runoff water. This will help planners in assessing the environmental costs of various scenarios, and in preparing for remedial actions. A numerical example is provided to illustrate the applications of the model. 相似文献
10.
"城市家具"是城市中的重要组成部分,是城市文明与形象的具体体现,是城市人性化设计的展示平台。城市家具无障碍设计是一个复杂而系统的工程,是所有人平等参与城市活动的平台,是城市公共环境发展的方向。文章深入分析我国现有"城市家具"设计中存在的问题,总结无障碍设计的价值,影响因素和基本原则,为无障碍城市家具设计指明了发展趋势。 相似文献