全文获取类型
收费全文 | 18934篇 |
免费 | 793篇 |
国内免费 | 20篇 |
专业分类
电工技术 | 213篇 |
综合类 | 18篇 |
化学工业 | 3681篇 |
金属工艺 | 321篇 |
机械仪表 | 403篇 |
建筑科学 | 1004篇 |
矿业工程 | 49篇 |
能源动力 | 502篇 |
轻工业 | 1677篇 |
水利工程 | 120篇 |
石油天然气 | 56篇 |
武器工业 | 1篇 |
无线电 | 1579篇 |
一般工业技术 | 3053篇 |
冶金工业 | 4041篇 |
原子能技术 | 188篇 |
自动化技术 | 2841篇 |
出版年
2023年 | 140篇 |
2022年 | 225篇 |
2021年 | 457篇 |
2020年 | 341篇 |
2019年 | 367篇 |
2018年 | 424篇 |
2017年 | 388篇 |
2016年 | 491篇 |
2015年 | 423篇 |
2014年 | 520篇 |
2013年 | 1072篇 |
2012年 | 856篇 |
2011年 | 1115篇 |
2010年 | 766篇 |
2009年 | 822篇 |
2008年 | 862篇 |
2007年 | 756篇 |
2006年 | 701篇 |
2005年 | 592篇 |
2004年 | 484篇 |
2003年 | 436篇 |
2002年 | 420篇 |
2001年 | 295篇 |
2000年 | 317篇 |
1999年 | 365篇 |
1998年 | 1037篇 |
1997年 | 675篇 |
1996年 | 506篇 |
1995年 | 353篇 |
1994年 | 326篇 |
1993年 | 319篇 |
1992年 | 189篇 |
1991年 | 169篇 |
1990年 | 143篇 |
1989年 | 144篇 |
1988年 | 142篇 |
1987年 | 128篇 |
1986年 | 121篇 |
1985年 | 146篇 |
1984年 | 132篇 |
1983年 | 117篇 |
1982年 | 95篇 |
1981年 | 108篇 |
1980年 | 92篇 |
1979年 | 96篇 |
1978年 | 94篇 |
1977年 | 143篇 |
1976年 | 196篇 |
1975年 | 80篇 |
1974年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
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
962.
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
963.
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
964.
Quantification of Margins and Uncertainties 总被引:1,自引:0,他引:1
966.
Andi K. Winterboer Martin I. Tietze Maria K. Wolters Johanna D. Moore 《Computer Speech and Language》2011,25(2):175-191
A common task for spoken dialog systems (SDS) is to help users select a suitable option (e.g., flight, hotel, and restaurant) from the set of options available. As the number of options increases, the system must have strategies for generating summaries that enable the user to browse the option space efficiently and successfully. In the user-model based summarize and refine approach (UMSR, Demberg and Moore, 2006), options are clustered to maximize utility with respect to a user model, and linguistic devices such as discourse cues and adverbials are used to highlight the trade-offs among the presented items. In a Wizard-of-Oz experiment, we show that the UMSR approach leads to improvements in task success, efficiency, and user satisfaction compared to an approach that clusters the available options to maximize coverage of the domain (Polifroni et al., 2003). In both a laboratory experiment and a web-based experimental paradigm employing the Amazon Mechanical Turk platform, we show that the discourse cues in UMSR summaries help users compare different options and choose between options, even though they do not improve verbatim recall. This effect was observed for both written and spoken stimuli. 相似文献
967.
There is currently an international drive to build new nuclear power plants, bringing about what is being termed a “nuclear renaissance”. However, the public perception of nuclear energy has historically been, and continues to be, a key issue, particularly in light of the Fukushima nuclear incident. This paper discusses the disparity between perceived and calculated risks based on the last four decades of research into risk perception. The leading psychological and sociological theories, Psychometric Paradigm and Cultural Theory, respectively, are critically reviewed. The authors then argue that a new nuclear-build policy that promotes a broader approach to design incorporating a wider range of stakeholder inputs, including that of the lay public, may provide a means for reducing the perceived risk of a nuclear plant. Further research towards such a new approach to design is proposed, based on integrating expert and lay stakeholder inputs and taking into account broader socio-cultural factors whilst maintaining the necessary emphasis on safety, technological development, economics and environmental sustainability. 相似文献
968.
Marisa Di Sabatino Mari Juel Lars Arnberg Martin Syvertsen Gabriella Tranell 《Transactions of the Indian Institute of Metals》2009,62(4-5):511-513
Two different cooling rates have been imposed during the early solidification of two multi-crystalline silicon ingots with 250mm diameter and 100mm height in a pilot scale directional solidification furnace. This has been done by opening a variable heat leak system below the crucible in order to achieve a high initial cooling rate in one of the ingots. The grain-structure and -orientation of these two ingots have been investigated by light microscopy (LM) and electron backscattered diffraction (EBSD), and their electrical properties by quasi-steady state photo-conductance (QSSPC) and surface photovoltage (SPV) method. The ingot with the high initial cooling rate shows predominantly grains which are significantly larger than what is usually found in mc-Si. The minority carrier diffusion lengths measured on the large grains in the ingot with high cooling rate show higher values than those measured on the ingot with smaller grains. These results indicate that principles of grain size and -orientation control in mc-Si ingots can be applied to a pilot scale furnace, and the potential for up-scaling to industrial ingots with improved electrical properties and, thus, higher solar cell conversion efficiency. 相似文献
969.
Joamin Gonzalez-Gutierrez Martin G. Scanlon 《Journal of the American Oil Chemists' Society》2013,90(9):1319-1326
Many soft food materials, including vegetable shortening, exhibit complex rheological behavior. For shortening, a precise determination of rheological behavior is necessary to understand its functionality as a food ingredient. Commercial vegetable shortening was subjected to monotonic and cyclic uniaxial compression tests at a wide range of loading rates. The elastic modulus determined from unloading was a function of strain, varying between 740 kPa in the shortening’s strain hardening region to 220 kPa at large strain where perfect plasticity had developed. Visual analysis of shortening specimens during the compression process showed that a rate-dependent stress overshoot was attributable to the development of a shear band following strain hardening. An elastoviscoplastic constitutive model was developed to define the complex rate-dependent compression response of vegetable shortening. Using the fundamental parameters obtained from the different types of compression tests, the proposed model accurately predicted the uniaxial compression response of vegetable shortening over a wide range (three decades) of compression rates. A model with predictive capabilities of large strain properties is desirable because shortening is subject to large strain in essentially all applications. 相似文献
970.