全文获取类型
收费全文 | 986860篇 |
免费 | 14309篇 |
国内免费 | 3567篇 |
专业分类
电工技术 | 18735篇 |
技术理论 | 5篇 |
综合类 | 1842篇 |
化学工业 | 154140篇 |
金属工艺 | 39990篇 |
机械仪表 | 30254篇 |
建筑科学 | 23913篇 |
矿业工程 | 6939篇 |
能源动力 | 24995篇 |
轻工业 | 82768篇 |
水利工程 | 11416篇 |
石油天然气 | 22420篇 |
武器工业 | 300篇 |
无线电 | 106206篇 |
一般工业技术 | 195637篇 |
冶金工业 | 179008篇 |
原子能技术 | 22283篇 |
自动化技术 | 83885篇 |
出版年
2021年 | 9048篇 |
2019年 | 8295篇 |
2018年 | 14003篇 |
2017年 | 14054篇 |
2016年 | 15026篇 |
2015年 | 10238篇 |
2014年 | 16677篇 |
2013年 | 45151篇 |
2012年 | 26419篇 |
2011年 | 35708篇 |
2010年 | 28647篇 |
2009年 | 31897篇 |
2008年 | 32844篇 |
2007年 | 32641篇 |
2006年 | 28598篇 |
2005年 | 25782篇 |
2004年 | 24068篇 |
2003年 | 23332篇 |
2002年 | 22869篇 |
2001年 | 22431篇 |
2000年 | 21396篇 |
1999年 | 21485篇 |
1998年 | 51587篇 |
1997年 | 37348篇 |
1996年 | 28999篇 |
1995年 | 22026篇 |
1994年 | 19935篇 |
1993年 | 19494篇 |
1992年 | 14824篇 |
1991年 | 14286篇 |
1990年 | 14036篇 |
1989年 | 13865篇 |
1988年 | 13159篇 |
1987年 | 11745篇 |
1986年 | 11592篇 |
1985年 | 13228篇 |
1984年 | 12294篇 |
1983年 | 11660篇 |
1982年 | 10526篇 |
1981年 | 10806篇 |
1980年 | 10291篇 |
1979年 | 10459篇 |
1978年 | 10260篇 |
1977年 | 11573篇 |
1976年 | 14837篇 |
1975年 | 9170篇 |
1974年 | 8767篇 |
1973年 | 8895篇 |
1972年 | 7594篇 |
1971年 | 6986篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Romero-Garcés A. Salles De Freitas R. Marfil R. Vicente-Chicote C. Martínez J. Inglés-Romero J. F. Bandera A. 《Multimedia Tools and Applications》2022,81(3):3603-3628
Multimedia Tools and Applications - The design of robots capable of operating autonomously in changing and unstructured environments, requires using complex software architectures in which,... 相似文献
72.
Belov M. I. Anashin D. V. Kabdin N. E. Storchevoy V. F. Sudnik Yu. A. 《Russian Engineering Research》2022,42(11):1110-1116
Russian Engineering Research - The stability of robot-mower motion in a specific direction is considered. The direction is regulated by means of an angular sensor and a programmable controller... 相似文献
73.
Revin A. A. Mikhaylova A. M. Konakov A. A. Tsyplenkov V. V. Shastin V. N. 《Semiconductors》2021,55(12):879-884
Semiconductors - The wave functions of electrons localized at P, As, and Sb shallow donors in Ge are calculated in the envelope function approximation taking into account valley–orbit... 相似文献
74.
Precipitation of calcium deficient hydroxyapatite nanoparticles in an environmentally benign manner by using only dilute solutions of calcium hydroxide and phosphoric acid without pH adjustment and addition of other chemicals, and water, being the only by-product was investigated by using continuous flow Vortex Reactor (VR) and Semi-Batch Reactor (SBR). The effect of hydrodynamics by changing the Reynolds number of the jets providing residence times of 8.4 ms to 4.37 s for VR, and by changing the stirrer speed between 100 rpm (Re = 2656) and 1000 rpm (Re = 26560) for SBR, on the particle size, particle size distribution, and morphology of the particles was investigated for both systems. It has been shown that it is possible to produce pure phase hydroxyapatite nanoparticles in the desired morphology by changing production system, without resorting to additives. While VR produced rod-like particles with the crystallite size around 4 nm, SBR produced spherical particles with the crystallite size of around 5 nm. 相似文献
75.
Journal of Low Temperature Physics - This study modeled and investigated the magnetocaloric effect in Ni2MnGa Heusler alloy characterized by its magnetic entropy change (ΔSm) and its... 相似文献
76.
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
77.
Alawiya Reslan Juliano G. Haddad Liadrine Moukendza Koundi Philippe Desprs Jean-Loup Bascands Gilles Gadea 《International journal of molecular sciences》2021,22(5)
Mosquito-borne Zika virus (ZIKV) became a real threat to human health due to the lack of vaccine and effective antiviral treatment. The virus has recently been responsible for a global outbreak leading to millions of infected cases. ZIKV complications were highlighted in adults with Guillain–Barré syndrome and in newborns with increasing numbers of congenital disorders ranging from mild developmental delays to fatal conditions. The ability of ZIKV to establish a long-term infection in diverse organs including the kidneys has been recently documented but the consequences of such a viral infection are still debated. Our study aimed to determine whether the efficiency of ZIKV growth in kidney cells relates to glucose concentration. Human kidney HK-2 cells were infected with different ZIKV strains in presence of normal and high glucose concentrations. Virological assays showed a decrease in viral replication without modifying entry steps (viral binding, internalization, fusion) under high glucose conditions. This decrease replication was associated with a lower virus progeny and increased cell viability when compared to ZIKV-infected HK-2 cells in normal glucose concentration. In conclusion, we showed for the first time that an elevated glucose level influences ZIKV replication level with an effect on kidney cell survival. 相似文献
78.
Kruglikov S. S. Zagorskii D. L. Kolesnikov V. A. Doludenko I. M. Bedin S. A. 《Theoretical Foundations of Chemical Engineering》2021,55(5):942-951
Theoretical Foundations of Chemical Engineering - The effect of the electrolyte composition, mass-transfer conditions, pore diameter, interpore distance, and electric parameters on the formation of... 相似文献
79.
Vasanthapriya R. Neelakandeswari N. Uthayarani K. Chitra M. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(11):4272-4280
Journal of Inorganic and Organometallic Polymers and Materials - This paper reports the performance of alizarin based SnO2 dye-sensitized solar cells. A novel template assisted method has been... 相似文献
80.
Carolyn A. Grimley Stephen Funni Christopher Green Elizabeth C. Dickey 《Journal of the European Ceramic Society》2021,41(4):2807-2817
In flash sintering experiments, the thermal history of the sample is key to understanding the mechanisms underlying densification rate and final properties. By combining robust temperature measurements with current-ramp-rate control, this study examined the effects of the thermal profile on the flash sintering of yttria-stabilized zirconia, with experiments ranging from a few seconds to several hours. The final density was maximized at slower heating rates, although processes slower than a certain threshold led to grain growth. The amount of grain growth observed was comparable to a similar conventional thermal process. The bulk electrical conductivity correlated with the maximum temperature and cooling rate. The only property that exhibited behavior that could not be attributed to solely the thermal profile was the grain boundary conductivity, which was consistently higher than conventional in flash sintered samples. These results suggest that, during flash sintering, athermal electric field effects are relegated to the grain boundary. 相似文献