全文获取类型
收费全文 | 1730056篇 |
免费 | 44493篇 |
国内免费 | 15659篇 |
专业分类
电工技术 | 46454篇 |
技术理论 | 24篇 |
综合类 | 20139篇 |
化学工业 | 308268篇 |
金属工艺 | 76439篇 |
机械仪表 | 57250篇 |
建筑科学 | 63207篇 |
矿业工程 | 18937篇 |
能源动力 | 56264篇 |
轻工业 | 124560篇 |
水利工程 | 18962篇 |
石油天然气 | 53246篇 |
武器工业 | 1772篇 |
无线电 | 219485篇 |
一般工业技术 | 310173篇 |
冶金工业 | 182607篇 |
原子能技术 | 36309篇 |
自动化技术 | 196112篇 |
出版年
2022年 | 16456篇 |
2021年 | 24238篇 |
2020年 | 18584篇 |
2019年 | 20233篇 |
2018年 | 23114篇 |
2017年 | 23486篇 |
2016年 | 28073篇 |
2015年 | 25894篇 |
2014年 | 39348篇 |
2013年 | 100025篇 |
2012年 | 49457篇 |
2011年 | 63520篇 |
2010年 | 56043篇 |
2009年 | 63496篇 |
2008年 | 56902篇 |
2007年 | 53797篇 |
2006年 | 56123篇 |
2005年 | 49780篇 |
2004年 | 48129篇 |
2003年 | 47112篇 |
2002年 | 45297篇 |
2001年 | 41736篇 |
2000年 | 40766篇 |
1999年 | 41071篇 |
1998年 | 52899篇 |
1997年 | 44730篇 |
1996年 | 40025篇 |
1995年 | 34333篇 |
1994年 | 31713篇 |
1993年 | 30759篇 |
1992年 | 27474篇 |
1991年 | 24334篇 |
1990年 | 24463篇 |
1989年 | 23345篇 |
1988年 | 21679篇 |
1987年 | 19774篇 |
1986年 | 19086篇 |
1985年 | 22302篇 |
1984年 | 22440篇 |
1983年 | 20320篇 |
1982年 | 19337篇 |
1981年 | 19448篇 |
1980年 | 17998篇 |
1979年 | 18465篇 |
1978年 | 17711篇 |
1977年 | 17474篇 |
1976年 | 18399篇 |
1975年 | 15975篇 |
1974年 | 15465篇 |
1973年 | 15573篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
The dynamic interaction between the mechanical and electrical drive parameters when damage suddenly appears in the mechanical part of a conveyer belt is investigated. The possibility of using the change in the motor’s electrical parameters as a diagnostic signal is assessed. A model for investigating the dynamic processes in the system consisting of the grid, the induction motor, and the conveyer belt is proposed. The grid and induction motor are described by a model of fourth-order state space, whose output is the torque at the motor shaft. The moments of inertia and pliability of the links between the elements in the mechanical part of the conveyer belt are determined. By gradually identifying the elements with the minimum moment of inertia and distributing their moments of inertia and pliabilities among the adjacent elements, we obtain a three-mass system simulating the mechanical part of the conveyer belt. This dynamic model is solved by means of Matlab Simulink software. The energy characteristics of the drive are determined in dynamic processes following a mechanical accident. 相似文献
994.
Zhimei Zheng Taixiu Liu Qibin Liu Jing Lei Juan Fang 《International Journal of Hydrogen Energy》2021,46(38):19846-19860
Solar thermochemical hydrogen production with energy level upgraded from solar thermal to chemical energy shows great potential. By integrating mid-and-low temperature solar thermochemistry and solid oxide fuel cells, in this paper, a new distributed energy system combining power, cooling, and heating is proposed and analyzed from thermodynamic, energy and exergy viewpoints. Different from the high temperature solar thermochemistry (above 1073.15 K), the mid-and-low temperature solar thermochemistry utilizes concentrated solar thermal (473.15–573.15 K) to drive methanol decomposition reaction, reducing irreversible heat collection loss. The produced hydrogen-rich fuel is converted into power through solid oxide fuel cells and micro gas turbines successively, realizing the cascaded utilization of fuel and solar energy. Numerical simulation is conducted to investigate the system thermodynamic performances under design and off-design conditions. Promising results reveal that solar-to-hydrogen and net solar-to-electricity efficiencies reach 66.26% and 40.93%, respectively. With the solar thermochemical conversion and hydrogen-rich fuel cascade utilization, the system exergy and overall energy efficiencies reach 59.76% and 80.74%, respectively. This research may provide a pathway for efficient hydrogen-rich fuel production and power generation. 相似文献
995.
Pedro Lavrador Marco R. Esteves Vítor M. Gaspar João F. Mano 《Advanced functional materials》2021,31(8):2005941
The complex tissue-specific physiology that is orchestrated from the nano- to the macroscale, in conjugation with the dynamic biophysical/biochemical stimuli underlying biological processes, has inspired the design of sophisticated hydrogels and nanoparticle systems exhibiting stimuli-responsive features. Recently, hydrogels and nanoparticles have been combined in advanced nanocomposite hybrid platforms expanding their range of biomedical applications. The ease and flexibility of attaining modular nanocomposite hydrogel constructs by selecting different classes of nanomaterials/hydrogels, or tuning nanoparticle-hydrogel physicochemical interactions widely expands the range of attainable properties to levels beyond those of traditional platforms. This review showcases the intrinsic ability of hybrid constructs to react to external or internal/physiological stimuli in the scope of developing sophisticated and intelligent systems with application-oriented features. Moreover, nanoparticle-hydrogel platforms are overviewed in the context of encoding stimuli-responsive cascades that recapitulate signaling interplays present in native biosystems. Collectively, recent breakthroughs in the design of stimuli-responsive nanocomposite hydrogels improve their potential for operating as advanced systems in different biomedical applications that benefit from tailored single or multi-responsiveness. 相似文献
996.
The Journal of Supercomputing - The Clairvoyant algorithm proposed in “A novel MPI reduction algorithm resilient to imbalances in process arrival times” was analyzed, commented and... 相似文献
997.
James E. Tyrrell Martyn G. Boutelle Alasdair J. Campbell 《Advanced functional materials》2021,31(1):2007086
Biological environments use ions in charge transport for information transmission. The properties of mixed electronic and ionic conductivity in organic materials make them ideal candidates to transduce physiological information into electronically processable signals. A device proven to be highly successful in measuring such information is the organic electrochemical transistor (OECT). Previous electrophysiological measurements performed using OECTs show superior signal-to-noise ratios than electrodes at low frequencies. Subsequent development has significantly improved critical performance parameters such as transconductance and response time. Here, interdigitated-electrode OECTs are fabricated on flexible substrates, with one such state-of-the-art device achieving a peak transconductance of 139 mS with a 138 µs response time. The devices are implemented into an array with interconnects suitable for micro-electrocorticographic application and eight architecture variations are compared. The two best-performing arrays are subject to the full electrophysiological spectrum using prerecorded signals. With frequency filtering, kHz-scale frequencies with 10 µV-scale voltages are resolved. This is supported by a novel quantification of the noise, which compares the gate voltage input and drain current output. These results demonstrate that high-performance OECTs can resolve the full electrophysiological spectrum and suggest that superior signal-to-noise ratios could be achieved in high frequency measurements of multiunit activity. 相似文献
998.
Lisichkin S. E. Rubin O. D. Pashchenko F. A. 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2021,55(3):373-379
Power Technology and Engineering - The experimental results on retaining reinforced-concrete walls reinforced with anchor ties and carbon composite materials on the face side of hydraulic... 相似文献
999.
Karolina M. Wójciak Dariusz M. Stasiak Joanna Stadnik Karolina Ferysiuk Anna Kononiuk 《International Journal of Food Science & Technology》2019,54(1):75-83
In this study, the influence of sonication time on the biogenic amines formation as a critical point in uncured dry-fermented beef manufacturing was studied. Samples of musculus semimembranosus were sonicated at different times (5 and 10 min) using ultrasound cold bath (4 °C) in acid whey (US 40 kHz and acoustic power 480 W). The effect of sonication on biogenic amine (BA) formation was investigated during 93 days of ripening period. Other parameters (pH value, water activity, microbial counts) that might provide further information on the product under study were also determined. The use of ultrasound during beef marinating in acid whey has a positive effect on retarding histamine (HIS), cadaverine (CAD), tyramine (TYR) and putrescine (PUT) formation. Moreover, the sonication treatment did not inhibit the growth of lactic acid bacteria (LAB) in dry-fermented beef during the whole ripening period. The pathogen bacteria (Staphylococcus aureus, Clostridium sp., Listeria monocytogenes) were not detected in all samples neither after 31 nor after 93 days of ripening period. 相似文献
1000.
The reported point centromeres of Scheffersomyces stipitis are retrotransposon long terminal repeats
Point centromeres, found in some ascomycete yeasts such Saccharomyces cerevisiae, are very different in structure from the centromeres of other eukaryotes. They are tiny and nonrepetitive and contain only two short conserved sequence motifs. Until recently, point centromeres were thought to have a single evolutionary origin, in the budding yeast family Saccharomycetaceae. Most yeasts outside this family have centromeres that are many kilobases in size. Some have centromeres consisting of a large inverted repeat sequence, others have centromeric clusters of retrotransposons, and a third group including Candida albicans has centromeres with no conserved sequence features. It was recently reported that Scheffersomyces stipitis has point centromeres with a strongly conserved 125-bp core sequence, which is unexpected because S. stipitis is only distantly related to the known point-centromere species. We show here that the 125-bp core sequence is actually part of the long terminal repeat (LTR) of the Ty5-like retrotransposon Tps5, which forms a cluster in the centromeric region of each S. stipitis chromosome. Thus, the LTR of a centromere-associated retrotransposon confers centromere-like mitotic stability when cloned into a plasmid. The centromeric regions of S. stipitis contain three types of Tps5 element (Tps5a, Tps5b, and Tps5c) and a noncoding nonautonomous large retrotransposon derivative. 相似文献