全文获取类型
收费全文 | 6305篇 |
免费 | 845篇 |
国内免费 | 23篇 |
专业分类
电工技术 | 58篇 |
综合类 | 117篇 |
化学工业 | 1780篇 |
金属工艺 | 96篇 |
机械仪表 | 114篇 |
建筑科学 | 254篇 |
矿业工程 | 16篇 |
能源动力 | 751篇 |
轻工业 | 658篇 |
水利工程 | 42篇 |
石油天然气 | 16篇 |
无线电 | 631篇 |
一般工业技术 | 1053篇 |
冶金工业 | 711篇 |
原子能技术 | 56篇 |
自动化技术 | 820篇 |
出版年
2022年 | 55篇 |
2021年 | 65篇 |
2020年 | 73篇 |
2019年 | 113篇 |
2018年 | 135篇 |
2017年 | 147篇 |
2016年 | 184篇 |
2015年 | 238篇 |
2014年 | 253篇 |
2013年 | 398篇 |
2012年 | 270篇 |
2011年 | 337篇 |
2010年 | 486篇 |
2009年 | 421篇 |
2008年 | 577篇 |
2007年 | 239篇 |
2006年 | 247篇 |
2005年 | 196篇 |
2004年 | 198篇 |
2003年 | 182篇 |
2002年 | 190篇 |
2001年 | 121篇 |
2000年 | 133篇 |
1999年 | 105篇 |
1998年 | 121篇 |
1997年 | 91篇 |
1996年 | 103篇 |
1995年 | 85篇 |
1994年 | 96篇 |
1993年 | 81篇 |
1992年 | 72篇 |
1991年 | 51篇 |
1990年 | 71篇 |
1989年 | 71篇 |
1988年 | 49篇 |
1987年 | 50篇 |
1986年 | 47篇 |
1985年 | 72篇 |
1984年 | 61篇 |
1983年 | 63篇 |
1982年 | 52篇 |
1981年 | 49篇 |
1980年 | 49篇 |
1979年 | 59篇 |
1978年 | 31篇 |
1977年 | 45篇 |
1976年 | 40篇 |
1975年 | 41篇 |
1974年 | 31篇 |
1973年 | 27篇 |
排序方式: 共有7173条查询结果,搜索用时 500 毫秒
201.
Wei Chen Jian Liu Flore Brue Frédéric Skoczylas C.A. Davy Xavier Bourbon Jean Talandier 《Cement and Concrete Research》2012,42(7):1001-1013
This experimental study aims at identifying the water retention properties of two industrial concretes to be used for long term underground nuclear waste storage structures. Together with water retention, gas transfer properties are identified at varying water saturation level, i.e. relative gas permeability is assessed directly as a function of water saturation level Sw. The influence of the initial de-sorption path and of the subsequent re-saturation are analysed both in terms of water retention and gas transfer properties. Also, the influence of concrete microstructure upon water retention and relative gas permeability is assessed, using porosity measurements, analysis of the BET theory from water retention properties, and MIP. Finally, a single relative gas permeability curve is proposed for each concrete, based on Van Genuchten–Mualem's statistical model, to be used for continuous modelling approaches of concrete structures, both during drying and imbibition. 相似文献
202.
In this paper, we illustrate specific power savings obtained from exploiting a reconfigurable mobile terminal under the 3GPP LTE standard. Building on traditional link adaptation towards maximum throughput and extended towards minimal power consumption, we add two flexible baseband components: the turbo decoder and the multiple input multiple output (MIMO) detector. Optimizing their configuration leads to larger power savings when compared to non-flexible systems only performing link adaptation. The gain observed strongly depends on the scenario. For low-activity set-ups with a few minutes of voice per day, the idle power dominates and the active data rate is relatively low. This makes analog front-end and time-domain processing dominant given their constant power consumption while MIMO detection and turbo decoding that scale with data rate play a smaller role. Still, because of its ability to improve the system spectral efficiency and hence reduce its duty cycle, an advanced MIMO detector can save 10% in power consumption, on the condition that the network requires to use MIMO. Otherwise single input single output is more power-efficient in downlink. In high-throughput scenarios, larger gains are obtained. The flexible MIMO detector can save up to 35% of average power consumption. The turbo decoding also brings some gain, saving up to 12% of power when the full bandwidth is allocated to a single user. 相似文献
203.
Jean‐Pierre Guyot 《International Journal of Food Science & Technology》2012,47(6):1109-1114
Cereal‐based fermented foods are major contributors to energy intake in developing countries (DC). Their microbiota is dominated by lactic acid bacteria and has been extensively investigated. Diversity studies have been facilitated by molecular methods enabling genotyping of isolates; the rapid development of ‘omics’ approaches should facilitate more comprehensive studies to describe the relation between microbial diversity, cell physiology and product characteristics. Also, the link between the food microbiota and health benefits, in particular in nutrition, should be investigated. There is a need to encourage researches in the field of DC cereal‐based foods in direction of more mechanistic approaches. 相似文献
204.
205.
A highly nonlinear increase in electrical conductivity and concomitant photoemission occurs not only during “flash sintering” but also in presintered, dense specimens. We report results from experiments with dense specimens that show a strong correspondence between the intensity of photoemission and electrical conductivity of specimens under a variety of conditions of the electrical parameters. It is proposed that both properties are related to the concentration of electron–hole pairs generated in such experiments. 相似文献
206.
207.
Jerzy Jedlinski Jean Luc Grosseau Poussard Jarosław Dabek Kazimierz Kowalski Marek Nocun Grzegorz Smola Zbigniew Żurek 《Oxidation of Metals》2017,88(3-4):371-382
The very early stages of the oxidation of an Fe20Cr2Al alloy, unmodified and ion-implanted by aluminium, yttrium and a combination of both elements, Al and Y, were studied at 1100 °C in oxygen using two-stage-oxidation exposures with 18O2 as a tracer and subsequent characterisation of the scales using SIMS analyses of distribution of oxygen isotopes and oxide-related negative ion clusters, SEM observations of the surface morphology and photoluminescence spectroscopy analysis of the phase composition. The scales formed in all cases, except for the Al-implanted alloy, exhibited layered structures, with the outer part comprising Fe- and Cr-rich oxide, and the inner part being Al2O3, which grew due to a mixed outward–inward mechanism . The alumina sub-layers contained the transient oxides and α-Al2O3. Implanted Al significantly affected the mechanism of the scale growth, providing that the scale consisted essentially of α-Al2O3, and grew via a mixed inward-outward mechanism typical for scales on alumina formers. 相似文献
208.
209.
210.
Bert J. Campo David Bevk Jurgen Kesters Jan Gilot Henk J. Bolink Jun Zhao Jean-Christophe Bolsée Wibren D. Oosterbaan Sabine Bertho Jan D’Haen Jean Manca Laurence Lutsen Guy Van Assche Wouter Maes René A.J. Janssen Dirk Vanderzande 《Organic Electronics》2013,14(2):523-534
The introduction of functional moieties in the donor polymer (side chains) offers a potential pathway toward selective modification of the nanomorphology of conjugated polymer:fullerene active layer blends applied in bulk heterojunction organic photovoltaics, pursuing morphology control and solar cell stability. For this purpose, two types of poly(3-alkylthiophene) random copolymers, incorporating different amounts (10/30/50%) of ester-functionalized side chains, were efficiently synthesized using the Rieke method. The solar cell performance of the functionalized copolymers was evaluated and compared to the pristine P3HT:PCBM system. It was observed that the physicochemical and opto-electronic characteristics of the polythiophene donor material can be modified to a certain extent via copolymerization without (too much) jeopardizing the OPV efficiency, as far as the functionalized side chains are introduced in a moderate ratio (<30%) and that preference is given to side chains with a small molar volume. A range of complementary techniques – UV–Vis spectroscopy, (modulated temperature) differential scanning calorimetry, transmission electron microscopy and X-ray diffraction analysis – indicated that variations in polymer crystallinity, while maintaining a high level of regioregularity, are probably the main factor responsible for the observed differences. 相似文献