全文获取类型
收费全文 | 209541篇 |
免费 | 24522篇 |
国内免费 | 10514篇 |
专业分类
电工技术 | 23924篇 |
技术理论 | 25篇 |
综合类 | 14370篇 |
化学工业 | 27869篇 |
金属工艺 | 7760篇 |
机械仪表 | 10263篇 |
建筑科学 | 30344篇 |
矿业工程 | 6909篇 |
能源动力 | 20274篇 |
轻工业 | 16314篇 |
水利工程 | 8755篇 |
石油天然气 | 7728篇 |
武器工业 | 1756篇 |
无线电 | 15320篇 |
一般工业技术 | 18879篇 |
冶金工业 | 9125篇 |
原子能技术 | 2445篇 |
自动化技术 | 22517篇 |
出版年
2024年 | 1038篇 |
2023年 | 4218篇 |
2022年 | 8366篇 |
2021年 | 10187篇 |
2020年 | 8541篇 |
2019年 | 7382篇 |
2018年 | 6726篇 |
2017年 | 8228篇 |
2016年 | 9823篇 |
2015年 | 10519篇 |
2014年 | 15683篇 |
2013年 | 14625篇 |
2012年 | 14772篇 |
2011年 | 15203篇 |
2010年 | 11678篇 |
2009年 | 11640篇 |
2008年 | 10459篇 |
2007年 | 12742篇 |
2006年 | 11338篇 |
2005年 | 9295篇 |
2004年 | 7356篇 |
2003年 | 6380篇 |
2002年 | 5222篇 |
2001年 | 4207篇 |
2000年 | 3647篇 |
1999年 | 2782篇 |
1998年 | 2050篇 |
1997年 | 1620篇 |
1996年 | 1480篇 |
1995年 | 1216篇 |
1994年 | 1083篇 |
1993年 | 825篇 |
1992年 | 627篇 |
1991年 | 541篇 |
1990年 | 471篇 |
1989年 | 380篇 |
1988年 | 284篇 |
1987年 | 236篇 |
1986年 | 182篇 |
1985年 | 243篇 |
1984年 | 209篇 |
1983年 | 138篇 |
1982年 | 147篇 |
1981年 | 83篇 |
1980年 | 111篇 |
1979年 | 56篇 |
1966年 | 32篇 |
1964年 | 50篇 |
1962年 | 71篇 |
1959年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
31.
为研究金针菇多糖(polysaccharide from Flammulina velutipes,FVP)对微冻大黄鱼及鱼片在贮藏期间肌原纤维蛋白性质的变化及水分分布的影响,实验分别选用0.03、0.06、0.09 g/L FVP浸渍处理大黄鱼和鱼片,以无菌水处理为对照组,分析微冻贮藏期间样品的感官指标得分、总挥发性盐基氮含量、总巯基含量、Ca2+-ATPase活性、蛋白流变学性质以及水分迁移变化规律。结果表明:FVP可有效抑制整鱼总挥发性盐基氮含量上升和感官得分的下降;减缓整鱼及鱼片在微冻过程中总巯基含量、Ca2+-ATPase活性下降和水分流失;此外FVP还能够延缓大黄鱼因腐败而出现的蛋白凝胶能力减弱。在本实验选取的多糖浓度范围内,0.09 g/L FVP处理组保鲜效果较强。该研究结果可为FVP用于水产品贮运保鲜提供理论参考。 相似文献
32.
Ionela-Dorina Dumbrava Calin-Cristian Cormos 《International Journal of Hydrogen Energy》2021,46(45):23149-23163
Hydrogen production by biogas conversion represent a promising solution for reduction of fossil CO2 emissions. In this work, a detailed techno-economic analysis was performed for decarbonized hydrogen production based on biogas conversion using calcium and chemical looping cycles. All evaluated concepts generate 100,000 Nm3/h high purity hydrogen. As reference cases, the biogas steam reforming design without decarbonization and with CO2 capture by gas-liquid chemical absorption were also considered. The results show that iron-based chemical looping design has higher energy efficiency compared with the gas-liquid absorption case by 2.3 net percentage points as well as a superior carbon capture rate (99% vs. 65%). The calcium looping case shows a lower efficiency than chemical scrubbing, with about 2.5 net percentage points, but the carbon capture rate is higher (95% vs. 65%). The hydrogen production cost increases with decarbonization, the calcium looping shows the most favourable situation (37.14 €/MWh) compared to the non-capture steam reforming case (33 €/MWh) and MDEA and iron looping cases (about 42 €/MWh). The calcium looping case has the lowest CO2 avoidance cost (10 €/t) followed by iron looping (20 €/t) and MDEA (31 €/t) cases. 相似文献
33.
Ida-Marie Andersson Björn Bergenståhl Marcela Alexander Marie Paulsson Maria Glantz 《International Journal of Food Science & Technology》2021,56(1):480-492
During whey powder production, the feed is subjected to several heat treatments which can cause lactosylation of proteins. In this study, lactosylation of whey proteins was evaluated in spray-dried powders before and after storage by varying the native protein fraction as well as the serum protein/lactose ratio in the powders. The lactosylation of native α-lactalbumin and β-lactoglobulin in the powders before storage was not affected to a large extent by the protein denaturation or if the feed had been heat treated in a high or low lactose environment. After storage (relative humidity of 23.5%, 30 °C, 25 days), the kinetic of lactosylation tended to increase with increasing native protein fraction and bulk protein content in the powders. An explanation could be that proteins dissolved in the lactose glassy structure might have a lower reactivity, while proteins present in the protein glassy structure with dissolved lactose may display higher lactosylation reactivity. 相似文献
34.
35.
《Ceramics International》2021,47(23):33223-33231
The effects of pH of the reaction solution and the concentration of phosphoric acid on the crystal growth behavior of LaPO4 crystallites were investigated and the mechanical properties of rare-earth phosphates were compared. As a result, the concentration of phosphoric acid of 10% was beneficial to the crystal growth of LaPO4 nanocrystalline. When the pH value of the reaction solution was 2, the size of LaPO4 crystallites increased gradually with the increasing reaction temperature, and the smallest crystallite size of 43.27 nm was obtained after heat-treatment at 1000 °C. Simultaneously, the activation energy for crystal growth of LaPO4 nanocrystalline was relatively lower (26.82 kJ mol−1). With the decreasing radii of rare-earth ions, the hardness, Young's modulus and fracture toughness of the bulk rare-earth phosphates exhibited a reduced tendency, resulted from the increase of porosity under the same preparation process. 相似文献
36.
Cell surface and secreted proteins provide essential functions for multicellular life. They enter the endoplasmic reticulum (ER) lumen co-translationally, where they mature and fold into their complex three-dimensional structures. The ER is populated with a host of molecular chaperones, associated co-factors, and enzymes that assist and stabilize folded states. Together, they ensure that nascent proteins mature properly or, if this process fails, target them for degradation. BiP, the ER HSP70 chaperone, interacts with unfolded client proteins in a nucleotide-dependent manner, which is tightly regulated by eight DnaJ-type proteins and two nucleotide exchange factors (NEFs), SIL1 and GRP170. Loss of SIL1′s function is the leading cause of Marinesco-Sjögren syndrome (MSS), an autosomal recessive, multisystem disorder. The development of animal models has provided insights into SIL1′s functions and MSS-associated pathologies. This review provides an in-depth update on the current understanding of the molecular mechanisms underlying SIL1′s NEF activity and its role in maintaining ER homeostasis and normal physiology. A precise understanding of the underlying molecular mechanisms associated with the loss of SIL1 may allow for the development of new pharmacological approaches to treat MSS. 相似文献
37.
Chaozhong Sun Xiaoying Guo Rui Ji Changzheng Hu Laijun Liu Liang Fang Zhenxiang Cheng Nengneng Luo 《Ceramics International》2021,47(4):5038-5043
The triboelectric effect has recently demonstrated its great potential in environmental remediation and even new energy applications for triggering a number of catalytic reactions by utilizing trivial mechanical energy. In this study, Ba4Nd2Fe2Nb8O30 (BNFN) submicron powders were used to degrade organic dyes via the tribocatalytic effect. Under the frictional excitation of three PTFE stirring rods in a 5 mg/L RhB dye solution, BNFN demonstrates a high tribocatalytic degradation efficiency of 97% in 2 h. Hydroxyl radicals (?OH) and superoxide radicals (?O2-) were also detected during the catalysis process, which proves that triboelectric energy stimulates BNFN to generate electron-hole pairs. The tribocatalysis of tungsten bronze BNFN submicron powders provides a novel and efficient method for the degradation of wastewater dye by utilizing trivial mechanical energy. 相似文献
38.
39.
40.
Fernanda Monedeiro Viorica Railean-Plugaru Maciej Monedeiro-Milanowski Pawe Pomastowski Bogusaw Buszewski 《International journal of molecular sciences》2021,22(9)
Considering the advent of antibiotic resistance, the study of bacterial metabolic behavior stimulated by novel antimicrobial agents becomes a relevant tool to elucidate involved adaptive pathways. Profiling of volatile metabolites was performed to monitor alterations of bacterial metabolism induced by biosynthesized silver nanoparticles (bio-AgNPs). Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae and Proteus mirabilis were isolated from pressure ulcers, and their cultures were prepared in the presence/absence of bio-AgNPs at 12.5, 25 and 50 µg mL−1. Headspace solid phase microextraction associated to gas chromatography–mass spectrometry was the employed analytical platform. At the lower concentration level, the agent promoted positive modulation of products of fermentation routes and bioactive volatiles, indicating an attempt of bacteria to adapt to an ongoing suppression of cellular respiration. Augmented response of aldehydes and other possible products of lipid oxidative cleavage was noticed for increasing levels of bio-AgNPs. The greatest concentration of agent caused a reduction of 44 to 80% in the variety of compounds found in the control samples. Pathway analysis indicated overall inhibition of amino acids and fatty acids routes. The present assessment may provide a deeper understanding of molecular mechanisms of bio-AgNPs and how the metabolic response of bacteria is untangled. 相似文献