全文获取类型
收费全文 | 276819篇 |
免费 | 20976篇 |
国内免费 | 13449篇 |
专业分类
电工技术 | 17241篇 |
技术理论 | 51篇 |
综合类 | 36911篇 |
化学工业 | 29524篇 |
金属工艺 | 10343篇 |
机械仪表 | 16151篇 |
建筑科学 | 41039篇 |
矿业工程 | 15175篇 |
能源动力 | 8431篇 |
轻工业 | 15362篇 |
水利工程 | 14167篇 |
石油天然气 | 11502篇 |
武器工业 | 2586篇 |
无线电 | 17703篇 |
一般工业技术 | 19508篇 |
冶金工业 | 15871篇 |
原子能技术 | 2780篇 |
自动化技术 | 36899篇 |
出版年
2024年 | 819篇 |
2023年 | 2578篇 |
2022年 | 4894篇 |
2021年 | 5936篇 |
2020年 | 6356篇 |
2019年 | 5276篇 |
2018年 | 5017篇 |
2017年 | 5989篇 |
2016年 | 7296篇 |
2015年 | 8184篇 |
2014年 | 15295篇 |
2013年 | 13981篇 |
2012年 | 18224篇 |
2011年 | 19444篇 |
2010年 | 15399篇 |
2009年 | 16053篇 |
2008年 | 14932篇 |
2007年 | 19707篇 |
2006年 | 18825篇 |
2005年 | 16515篇 |
2004年 | 14100篇 |
2003年 | 12802篇 |
2002年 | 10559篇 |
2001年 | 8844篇 |
2000年 | 7528篇 |
1999年 | 6202篇 |
1998年 | 4705篇 |
1997年 | 4093篇 |
1996年 | 3778篇 |
1995年 | 3193篇 |
1994年 | 2816篇 |
1993年 | 2122篇 |
1992年 | 1873篇 |
1991年 | 1404篇 |
1990年 | 1204篇 |
1989年 | 1055篇 |
1988年 | 848篇 |
1987年 | 587篇 |
1986年 | 437篇 |
1985年 | 373篇 |
1984年 | 351篇 |
1983年 | 252篇 |
1982年 | 218篇 |
1981年 | 168篇 |
1980年 | 135篇 |
1979年 | 112篇 |
1978年 | 64篇 |
1977年 | 72篇 |
1976年 | 56篇 |
1975年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 72 毫秒
12.
Jean-Claude Malela-Majika Sandile Charles Shongwe Olatunde Adebayo Adeoti 《Quality and Reliability Engineering International》2021,37(8):3314-3322
The sensitivity of a monitoring scheme depends on many factors including the variance of the charting statistic which is very important in the computation of the control limits. This paper discusses the computation of the variance of the recently proposed hybrid homogeneously weighted moving average (HHWMA) scheme which was based on an incorrect assumption. The correct variance is used to evaluate the run-length characteristics of the HHWMA scheme. It is observed that the incorrect variance has a significant impact on the sensitivity (or performance) of the HHWMA scheme. 相似文献
13.
Thomas RAINER 《景观设计学(英文)》2021,9(1):112
The ability of landscape architectural projects to mitigate the worst effects of climate change will depend upon designed ecological systems. These systems will be built with plants. Despite the recognition of ecology as an essential driver of landscapes, the professionals of landscape architecture too often lack the knowledge and practical skills to create robust vegetative systems. New approaches and tools are required. This article outlines principles and methods for designing biodiverse plant systems for urban sites. Planting methods that increase species richness, functional diversity, and spatial complexity are emphasized as a way of developing more resilient plantings. Selecting species with similar evolutionary adaptions to stress, disturbance, and competition—as well as creating multi-layered compositions of diverse plant morphologies—allows designers to create compatible, long-lived plant mixes. To balance the increased visual complexity of diverse plant mixes, the article explores design techniques to make plantings more appealing to the public. The strategies explored here are based on the projects, experience, and research of Phyto Studio, a Washington, D.C. based studio. The methods build on work described in the author’s book, Planting in a Post-Wild World, an exploration of how to create designed plant communities. 相似文献
14.
Elli Ntakou Ralph Masiello Farnaz Farzan Shay Bahramirad Aleksi Paaso M.A. Nayeem Maigha Maigha Daniel Kushner 《The Electricity Journal》2019,32(4):45-49
This paper presents part of the work ComEd and Quanta Technology have performed to quantify the locational and temporal value of DER to avoid distribution grid upgrade investments. It focuses on the formulation of a robust and efficient algorithm for DER optimal dispatch on a distribution feeder to mitigate the violation of current and voltage limits using the allocated cost of capacity and locational marginal value of real and reactive DER injection/withdrawal. 相似文献
15.
16.
An electrolyte Equation of State is presented by combining the Cubic Plus Association Equation of State,Mean Spherical Approximation and the Born equation.This new model uses experimental relative static permittivity,intend to predict well the activity coefficients of individual ions (ACI) and liquid densities of aqueous solutions.This new model is applied to model water + NaCl binary system and water + gas +NaCl ternary systems.The cation/anion-water interaction parameters of are obtained by fitting the exper-imental data of ACI,mean ionic activity coefficients (MIAC) and liquid densities of water + NaCl binary system.The cation/anion-gas interaction parameters are obtained by fitting the experimental data of gas solubilities in aqueous NaCl solutions.The modeling results show that this new model can correlate well with the phase equilibrium and volumetric properties.Without gas,predictions for ACI,MIAC,and liquid densities present relative average deviations of 1.3%,3.6% and 1.4% compared to experimental ref-erence values.For most gas-containing systems,predictions for gas solubilities present relative average deviations lower than 7.0%.Further,the contributions of ACI,and salting effects of NaCl on gases are ana-lyzed and discussed. 相似文献
17.
The effect of the emergency perception of bystanders of cyberbullying victims on helping behaviors is often neglected in research on cyberbullying. In this study, we explored the influence of this cognitive factor on cyber-bystanders’ helping tendencies as well as elucidated possible underlying processes. The results of two studies were reported. In Study 1, 150 undergraduates read a true case of a girl experiencing cyberbullying. The results indicated that when the participants perceived the victim’s situation to be more critical (i.e., higher emergency perception), their helping tendencies were stronger, partly through increased state empathy followed by feelings of responsibility to help. In Study 2, we randomly assigned 300 undergraduates to two groups. The low emergency group read the same cyberbullying case as Study 1, whereas the cyberbullying case read by the high emergency group contained additional emergency information of the victim. The results indicated that the high emergency group expressed stronger helping tendencies than did the low emergency group. This effect was caused by a stronger perception that the victim was in an emergency situation, which not only strengthened the participants’ helping tendencies directly but also indirectly through increasing their state empathy and feelings of responsibility to help. 相似文献
18.
19.
Zachary Zander Deirdre Newton Heather Scaglione Averie Reiber Parminder Agarwal 《Polymer Engineering and Science》2021,61(12):3029-3036
The incursion of microbial growth on polymeric products can deteriorate their performance and lead to the development of undesirable staining and odors. A growing trend in the industry has aimed to reduce microbial populations on high-touch surfaces via the use of antimicrobials to protect material aesthetics and durability or to prevent the spread of pathogenic microorganisms. In this study, a variety of plastic substrates (30 unique polymer compounds), including poly(acrylonitrile-co-butadiene-co-styrene), poly(butylene terephthalate), poly(etherimide), various thermoplastic elastomers (TPEs), poly(carbonates), and poly(amides), were screened for susceptibility to microbial attack using American Society for Testing and Materials (ASTM) G21 (fungi susceptibility), Japanese Industrial Standard (JIS) Z2801, and modified ASTM E1428-15a (bacterial susceptibility) test standards. TPEs were determined to be most susceptible to microbial attack under the appropriate environmental conditions. Subsequent studies assessed the use of an antimicrobial additive, zinc pyrithione (ZPT), for potential efficacy in a variety of TPE blends for diverse target market applications. ZPT proved to be very effective in protecting TPEs, reducing Staphylococcus aureus and Escherichia coli populations by 99.9% or more in JIS Z2801 testing and inhibiting fungal growth (rating = 0) according to the ASTM G21 standard. 相似文献