全文获取类型
收费全文 | 22243篇 |
免费 | 904篇 |
国内免费 | 26篇 |
专业分类
电工技术 | 333篇 |
综合类 | 26篇 |
化学工业 | 4616篇 |
金属工艺 | 409篇 |
机械仪表 | 496篇 |
建筑科学 | 1281篇 |
矿业工程 | 68篇 |
能源动力 | 605篇 |
轻工业 | 2130篇 |
水利工程 | 176篇 |
石油天然气 | 64篇 |
武器工业 | 1篇 |
无线电 | 1891篇 |
一般工业技术 | 3618篇 |
冶金工业 | 3861篇 |
原子能技术 | 261篇 |
自动化技术 | 3337篇 |
出版年
2023年 | 161篇 |
2022年 | 192篇 |
2021年 | 522篇 |
2020年 | 384篇 |
2019年 | 423篇 |
2018年 | 469篇 |
2017年 | 440篇 |
2016年 | 550篇 |
2015年 | 489篇 |
2014年 | 617篇 |
2013年 | 1258篇 |
2012年 | 989篇 |
2011年 | 1315篇 |
2010年 | 894篇 |
2009年 | 953篇 |
2008年 | 1025篇 |
2007年 | 896篇 |
2006年 | 845篇 |
2005年 | 704篇 |
2004年 | 587篇 |
2003年 | 533篇 |
2002年 | 519篇 |
2001年 | 363篇 |
2000年 | 383篇 |
1999年 | 428篇 |
1998年 | 874篇 |
1997年 | 593篇 |
1996年 | 476篇 |
1995年 | 370篇 |
1994年 | 339篇 |
1993年 | 327篇 |
1992年 | 232篇 |
1991年 | 204篇 |
1990年 | 198篇 |
1989年 | 194篇 |
1988年 | 175篇 |
1987年 | 172篇 |
1986年 | 164篇 |
1985年 | 203篇 |
1984年 | 192篇 |
1983年 | 178篇 |
1982年 | 142篇 |
1981年 | 145篇 |
1980年 | 126篇 |
1979年 | 141篇 |
1978年 | 142篇 |
1977年 | 169篇 |
1976年 | 203篇 |
1975年 | 130篇 |
1974年 | 121篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Eoin Devereux Amanda Haynes Martin J. Power 《Journal of Housing and the Built Environment》2011,26(2):123-142
By triangulating analyses of content and reception with a focus on production, this article attempts to understand the dynamics
of and underlying reasons for the media stigmatisation of place. The research described contributes to a body of work examining
how mass media and other social forces factor in the creation of negative stereotypes that damage the reputations of the places
in which the poor reside. The overarching framework of understanding, provided by Goffman’s theory of stigma, is complemented
by two further inter-related theoretical approaches, namely Social Exclusion and Political Economy. Combining analyses of
media production (practices), media content (discourses) and audience reception (beliefs, attitudes), we analyse the representation
of one of Ireland’s most deprived public housing estates in the print and broadcast media. Having established the stigmatising
character and impact of national and local media content via this tripartite methodology, we focus on identifying and explaining
the media practices that serve to (re)produce the estate’s ‘spoiled identity’. Our analysis of journalists’ explanations for
these practices identifies the commercial realities, which progressively influence media production, as directly impacting
media producers’ relationships with, and depictions of, poor places. We conclude by examining debates regarding the potential
for rehabilitating a spoiled identity. 相似文献
992.
Akram El Hasni Stefan Pfirrmann Anett Kolander Erwin Yacoub-George Martin König Christof Landesberger Anja Voigt Gabi Grützner Uwe Schnakenberg 《Microfluidics and nanofluidics》2017,21(3):41
We present a new epoxy-based negative-tone dry film photoresist (DFR) for fabricating multilayer microfluidic devices using a lamination process combined with a standard photolithography technology. As proof-of-concept, a complex 3D-hydrodynamic focusing device was produced via a six-layer lamination process of 33 µm-thick DFR layers. The bonding strength of the new DFR was tested on silicon, glass, and titanium substrates, respectively. A maximum bonding strength of 37 MPa was obtained for the dry film photoresist laminated on glass. No leakage was found, and burst tests proved excellent robustness and sealing reliability of the microchannels. 相似文献
993.
A. Santiago L. Martin J.J. Iruin M.J. Fernández-Berridi A. González L. Irusta 《Progress in Organic Coatings》2014
Polyurethane–siloxane thermoset copolymers were obtained from Isophorone diisocyanate trimer, Polycaprolactone triol and 10% of hydroxy terminated Polydimethyl siloxane. The copolymers showed a phase separated structure that depended on the conversion of the reaction and casting temperature. The different samples obtained had water contact angles higher than 90°. Moreover the contact angle values presented a maximum at intermediate reaction conversion. Although FTIR measurements showed that siloxane concentration at the surface increased with reaction time, the maximum contact angle value was related to the higher roughness calculated from AFM images. DMTA results confirmed that the phase separation was higher at intermediate conversions. 相似文献
994.
Donggeon Han Yasser Khan Jonathan Ting Simon M. King Nir Yaacobi‐Gross Martin J. Humphries Christopher J. Newsome Ana C. Arias 《Advanced materials (Deerfield Beach, Fla.)》2017,29(22)
A method to print two materials of different functionality during the same printing step is presented. In printed electronics, devices are built layer by layer and conventionally only one type of material is deposited in one pass. Here, the challenges involving printing of two emissive materials to form polymer light‐emitting diodes (PLEDs) that emit light of different wavelengths without any significant changes in the device characteristics are described. The surface‐energy‐patterning technique is utilized to print materials in regions of interest. This technique proves beneficial in reducing the amount of ink used during blade coating and improving the reproducibility of printed films. A variety of colors (green, red, and near‐infrared) are demonstrated and characterized. This is the first known attempt to print multiple materials by blade coating. These devices are further used in conjunction with a commercially available photodiode to perform blood oxygenation measurements on the wrist, where common accessories are worn. Prior to actual application, the threshold conditions for each color are discussed, in order to acquire a stable and reproducible photoplethysmogram (PPG) signal. Finally, based on the conditions, PPG and oxygenation measurements are successfully performed on the wrist with green and red PLEDs. 相似文献
995.
The wireless industry is currently undergoing a major transition from second generation (2G) to third generation (3G) wireless technologies. The paper attempts to assess wireless technology migration options using the real options approach (ROA) to support the wireless network operators’ strategic decisions: to migrate or not, if so, which migration path to take. The preliminary result shows that the evolution of wireless network technologies between generations is desirable, but not within generations. Finally, from a strategic perspective, we should consider the possible challenges that may hinder migration. By identifying these challenges, we can be more watchful of transition pitfalls and can choose a better alternative. 相似文献
996.
The fire-safe design of concrete structures, which incorporate post-tensioned prestressing tendons, has recently been the subject of debate within the structural engineering community, particularly when unbonded post-tensioned (UPT) prestressing tendons are used. Despite several studies aimed at furthering our understanding of the response of UPT concrete structures in fire, many aspects of their response in real fires remain poorly understood. An exhaustive summary of available test data, which have been used over the past five decades to generate fire design guidance for UPT concrete structures is given. Case studies showing the response of real UPT structures in severe building fires are also discussed. In both cases, the intent is to highlight inadequacies in the current state of knowledge for UPT buildings in fire and to prioritize areas for future research. 相似文献
997.
Electrochemical characterization of electrolytes for lithium-ion batteries based on lithium difluoromono(oxalato)borate 总被引:1,自引:0,他引:1
Sandra ZugmannDominik Moosbauer Marius AmerellerChristian Schreiner Franz WudyRené Schmitz Raphael SchmitzPhilipp Isken Christian DippelRomek Müller Miriam KunzeAlexandra Lex-Balducci Martin WinterHeiner Jakob Gores 《Journal of power sources》2011,196(3):1417-1424
The salt lithium difluoromono(oxalato)borate (LiDFOB) showed some promising results for lithium-ion-cells. It was synthesized via a new synthetic route that avoids chloride impurities. Here we report the properties of its solutions (solvent blend ethylene carbonate/diethyl carbonate (3:7, mass ratio), including its conductivity, cationic transference number, hydrolysis, Al-current collector corrosion-protection ability and its cycling performance with some electrode materials. Some Al-corrosion studies were also performed with the help of our recently developed computer controlled impedance scanning electrochemical quartz crystal microbalance (EQCM) that proofed to be a useful tool for battery material investigations. 相似文献
998.
Construction projects can involve a diverse range of stakeholders and the success of the project depends very much on fulfilling their needs and expectations. It is important, therefore, to identify and recognize project stakeholders and develop a rigorous stakeholder management process. However, limited research has investigated the impact of stakeholders on construction projects in developing countries. A stakeholder impact analysis (SIA), based on an approach developed by Olander (2007), was adopted to investigate the stakeholders’ impact on state‐owned civil engineering projects in Vietnam. This involved the analysis of a questionnaire survey of 57 project managers to determine the relative importance of different stakeholders. The results show the client to have the highest level of impact on the projects, followed by project managers and the senior management of state‐owned engineering firms. The SIA also provides suggestions to project managers in developing and evaluating the stakeholder management process. 相似文献
999.
Amrita Kundu Claire Davis Martin Strangwood 《Metallurgical and Materials Transactions A》2011,42(9):2794-2806
The present investigation examines the applicability of the Dutta–Sellars equations in predicting the recrystallized grain
sizes following deformation for a 0.046 wt pct Nb-bearing, commercially produced steel with a segregated solute content (from
continuous casting). The investigation considered initial unimodal and bimodal grain size distributions before deformation
that were generated by reheating the steel to 1498 K and 1423 K (1225 °C and 1150 °C), respectively. It was found that the
reheated grain size distribution (separated into grain size classes) could be related to the solute-rich (smaller grain size
classes) and solute-depleted (larger grain size classes) regions. The use of these relationships and a simple halving of the
grain size within the distribution on recrystallization (used previously for homogenized samples of this steel) were found
to be appropriate in the grain size class-based use of the Dutta–Sellars equations with respect to mode and maximum grain
sizes after hot deformation and holding. This approach successfully predicted (confirmed by experiment) the grain size distribution
after deformation in the presence of Nb segregation from continuous casting. 相似文献
1000.
Quantification of Margins and Uncertainties 总被引:1,自引:0,他引:1