全文获取类型
收费全文 | 552217篇 |
免费 | 7456篇 |
国内免费 | 3010篇 |
专业分类
电工技术 | 10768篇 |
技术理论 | 5篇 |
综合类 | 1746篇 |
化学工业 | 82361篇 |
金属工艺 | 25518篇 |
机械仪表 | 19150篇 |
建筑科学 | 13192篇 |
矿业工程 | 3567篇 |
能源动力 | 12201篇 |
轻工业 | 44634篇 |
水利工程 | 6290篇 |
石油天然气 | 11680篇 |
武器工业 | 286篇 |
无线电 | 61168篇 |
一般工业技术 | 111403篇 |
冶金工业 | 95245篇 |
原子能技术 | 12455篇 |
自动化技术 | 51014篇 |
出版年
2021年 | 4268篇 |
2019年 | 3835篇 |
2018年 | 13196篇 |
2017年 | 13550篇 |
2016年 | 10701篇 |
2015年 | 5326篇 |
2014年 | 8219篇 |
2013年 | 21665篇 |
2012年 | 15518篇 |
2011年 | 24810篇 |
2010年 | 20777篇 |
2009年 | 21251篇 |
2008年 | 22140篇 |
2007年 | 23896篇 |
2006年 | 14919篇 |
2005年 | 16192篇 |
2004年 | 14149篇 |
2003年 | 13402篇 |
2002年 | 12400篇 |
2001年 | 12023篇 |
2000年 | 11340篇 |
1999年 | 11603篇 |
1998年 | 26745篇 |
1997年 | 19305篇 |
1996年 | 14933篇 |
1995年 | 11416篇 |
1994年 | 10243篇 |
1993年 | 10160篇 |
1992年 | 7644篇 |
1991年 | 7310篇 |
1990年 | 7233篇 |
1989年 | 7199篇 |
1988年 | 6690篇 |
1987年 | 5915篇 |
1986年 | 5929篇 |
1985年 | 6596篇 |
1984年 | 6264篇 |
1983年 | 5793篇 |
1982年 | 5236篇 |
1981年 | 5490篇 |
1980年 | 5211篇 |
1979年 | 5166篇 |
1978年 | 5144篇 |
1977年 | 5515篇 |
1976年 | 7230篇 |
1975年 | 4474篇 |
1974年 | 4267篇 |
1973年 | 4294篇 |
1972年 | 3662篇 |
1971年 | 3265篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Zagidullin S. Kh. Dolganov V. L. Lozhkin I. G. 《Chemical and Petroleum Engineering》2022,57(9-10):765-769
Chemical and Petroleum Engineering - The hydrodynamics of oxidation towers used for bitumen production were studied using a model tower having transparent walls. Experiments were carried out in two... 相似文献
32.
Radchenko P. A. Batuev S. P. Radchenko A. V. 《Journal of Engineering Physics and Thermophysics》2022,95(1):90-96
Journal of Engineering Physics and Thermophysics - A numerical investigation has been made into the interaction of slender (5–20 calibers) steel cylinder strikers with orthotropic compost... 相似文献
33.
Rudenko A. I. Nishchik A. P. Otrokh E. A. Terekh A. M. 《Journal of Engineering Physics and Thermophysics》2022,95(1):206-212
Journal of Engineering Physics and Thermophysics - Results of investigation into the influence of a corrosion process on thermotechnical characteristics of heat pipes of low-temperature range are... 相似文献
34.
Radiochemistry - Magnetically modified waste bark of the Aegle marmelos tree was prepared by using green synthesis method and was used in a batch system for U(VI) removal from aqueous solution. The... 相似文献
35.
36.
Bilal Alashkar Alhamwe Daniel P. Potaczek Sarah Miethe Fahd Alhamdan Lukas Hintz Arslan Magomedov Holger Garn 《International journal of molecular sciences》2021,22(9)
Extracellular vesicles (EVs) are membranous structures, which are secreted by almost every cell type analyzed so far. In addition to their importance for cell-cell communication under physiological conditions, EVs are also released during pathogenesis and mechanistically contribute to this process. Here we summarize their functional relevance in asthma, one of the most common chronic non-communicable diseases. Asthma is a complex persistent inflammatory disorder of the airways characterized by reversible airflow obstruction and, from a long-term perspective, airway remodeling. Overall, mechanistic studies summarized here indicate the importance of different subtypes of EVs and their variable cargoes in the functioning of the pathways underlying asthma, and show some interesting potential for the development of future therapeutic interventions. Association studies in turn demonstrate a good diagnostic potential of EVs in asthma. 相似文献
37.
Liangtao Yang Liang-Yin Kuo Juan Miguel López del Amo Prasant Kumar Nayak Katherine A. Mazzio Sebastian Maletti Daria Mikhailova Lars Giebeler Payam Kaghazchi Teófilo Rojo Philipp Adelhelm 《Advanced functional materials》2021,31(38):2102939
A known strategy for improving the properties of layered oxide electrodes in sodium-ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2-Na0.67Mn0.6Ni0.2Li0.2O2 is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid-state NMR, operando XRD, and density functional theory (DFT). For the as-synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid-solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g-1 after 100 cycles. In contrast, the Li-free compositions Na0.67Mn0.6Ni0.4O2 and Na0.67Mn0.8Ni0.2O2 show phase transitions and a stair-case voltage profile. The capacity is found to originate from mainly Ni3+/Ni4+ and O2-/O2-δ redox processes by DFT, although a small contribution from Mn4+/Mn5+ to the capacity cannot be excluded. 相似文献
38.
Yang Hu Stephanie M. Sjoberg Chunpen Chen Amber L. Hauvermale Craig F. Morris Stephen R. Delwiche Ashley E. Cannon Camille M. Steber Zhiwu Zhang 《Comprehensive Reviews in Food Science and Food Safety》2022,21(3):2105-2117
This review examines the application, limitations, and potential alternatives to the Hagberg–Perten falling number (FN) method used in the global wheat industry for detecting the risk of poor end-product quality mainly due to starch degradation by the enzyme α-amylase. By viscometry, the FN test indirectly detects the presence of α-amylase, the primary enzyme that digests starch. Elevated α-amylase results in low FN and damages wheat product quality resulting in cakes that fall, and sticky bread and noodles. Low FN can occur from preharvest sprouting (PHS) and late maturity α-amylase (LMA). Moist or rainy conditions before harvest cause PHS on the mother plant. Continuously cool or fluctuating temperatures during the grain filling stage cause LMA. Due to the expression of additional hydrolytic enzymes, PHS has a stronger negative impact than LMA. Wheat grain with low FN/high α-amylase results in serious losses for farmers, traders, millers, and bakers worldwide. Although blending of low FN grain with sound wheat may be used as a means of moving affected grain through the marketplace, care must be taken to avoid grain lots from falling below contract-specified FN. A large amount of sound wheat can be ruined if mixed with a small amount of sprouted wheat. The FN method is widely employed to detect α-amylase after harvest. However, it has several limitations, including sampling variability, high cost, labor intensiveness, the destructive nature of the test, and an inability to differentiate between LMA and PHS. Faster, cheaper, and more accurate alternatives could improve breeding for resistance to PHS and LMA and could preserve the value of wheat grain by avoiding inadvertent mixing of high- and low-FN grain by enabling testing at more stages of the value stream including at harvest, delivery, transport, storage, and milling. Alternatives to the FN method explored here include the Rapid Visco Analyzer, enzyme assays, immunoassays, near-infrared spectroscopy, and hyperspectral imaging. 相似文献
39.
Mohammed Amin Salih Venkatachalam K. Hubálovský S. Trojovský P. Prabu P. 《Mobile Networks and Applications》2022,27(3):1050-1059
Mobile Networks and Applications - 5G/6G communication are first generation high speed wireless communication network which integrates the aerial data, terrestrial data and maritime data via... 相似文献
40.