全文获取类型
收费全文 | 4738篇 |
免费 | 357篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 26篇 |
综合类 | 4篇 |
化学工业 | 1008篇 |
金属工艺 | 71篇 |
机械仪表 | 63篇 |
建筑科学 | 231篇 |
矿业工程 | 88篇 |
能源动力 | 76篇 |
轻工业 | 874篇 |
水利工程 | 29篇 |
石油天然气 | 10篇 |
无线电 | 266篇 |
一般工业技术 | 760篇 |
冶金工业 | 914篇 |
原子能技术 | 20篇 |
自动化技术 | 663篇 |
出版年
2023年 | 44篇 |
2022年 | 18篇 |
2021年 | 118篇 |
2020年 | 84篇 |
2019年 | 100篇 |
2018年 | 108篇 |
2017年 | 142篇 |
2016年 | 172篇 |
2015年 | 141篇 |
2014年 | 180篇 |
2013年 | 380篇 |
2012年 | 225篇 |
2011年 | 279篇 |
2010年 | 234篇 |
2009年 | 203篇 |
2008年 | 253篇 |
2007年 | 266篇 |
2006年 | 197篇 |
2005年 | 177篇 |
2004年 | 147篇 |
2003年 | 131篇 |
2002年 | 130篇 |
2001年 | 87篇 |
2000年 | 77篇 |
1999年 | 68篇 |
1998年 | 97篇 |
1997年 | 81篇 |
1996年 | 73篇 |
1995年 | 63篇 |
1994年 | 82篇 |
1993年 | 68篇 |
1992年 | 39篇 |
1991年 | 33篇 |
1990年 | 45篇 |
1989年 | 43篇 |
1988年 | 44篇 |
1987年 | 47篇 |
1986年 | 46篇 |
1985年 | 39篇 |
1984年 | 43篇 |
1983年 | 44篇 |
1982年 | 29篇 |
1981年 | 27篇 |
1980年 | 21篇 |
1979年 | 23篇 |
1978年 | 14篇 |
1977年 | 26篇 |
1976年 | 20篇 |
1975年 | 24篇 |
1974年 | 14篇 |
排序方式: 共有5103条查询结果,搜索用时 15 毫秒
1.
2.
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
3.
Max J. Cotler Erin B. Rousseau Khalil B. Ramadi Joshua Fang Ann M. Graybiel Robert Langer Michael J. Cima 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(37)
Enhanced understanding of neuropathologies has created a need for more advanced tools. Current neural implants result in extensive glial scarring and are not able to highly localize drug delivery due to their size. Smaller implants reduce surgical trauma and improve spatial resolution, but such a reduction requires improvements in device design to enable accurate and chronic implantation in subcortical structures. Flexible needle steering techniques offer improved control over implant placement, but often require complex closed‐loop control for accurate implantation. This study reports the development of steerable microinvasive neural implants (S‐MINIs) constructed from borosilicate capillaries (OD = 60 µm, ID = 20 µm) that do not require closed‐loop guidance or guide tubes. S‐MINIs reduce glial scarring 3.5‐fold compared to prior implants. Bevel steered needles are utilized for open‐loop targeting of deep‐brain structures. This study demonstrates a sinusoidal relationship between implant bevel angle and the trajectory radius of curvature both in vitro and ex vivo. This relationship allows for bevel‐tipped capillaries to be steered to a target with an average error of 0.23 mm ± 0.19 without closed‐loop control. Polished microcapillaries present a new microinvasive tool for chronic, predictable targeting of pathophysiological structures without the need for closed‐loop feedback and complex imaging. 相似文献
4.
5.
Nitsa Buaron Antonella Mangraviti Francesco Volpin Ann Liu Mariangela Pedone Eric Sankey Dina Aranovich Itay Adar Fausto J. Rodriguez Abraham Nyska Riki Goldbart Tamar Traitel Henry Brem Betty Tyler Joseph Kost 《Advanced functional materials》2021,31(44):2100643
Treating neuroinflammation-related injuries and disorders through manipulation of neuroinflammation functions is being heralded as a new therapeutic strategy. In this study, a novel pectic galactan (PG) polysaccharide based gene therapy approach is developed for targeting reactive gliosis in neuroinflammation. Galectin-3 (Gal-3) is a cell protein with a high affinity to β-galactoside sugars and is highly expressed in reactive gliosis. Since PG carries galactans, it can target reactive gliosis via specific carbohydrate interaction between galactan and Gal-3 on the cell membrane, and therefore can be utilized as a carrier for delivering genes to these cells. The carrier is synthesized by modifying quaternary ammonium groups on the PG. The resulting quaternized PG (QPG) is found to form complexes with plasmid DNA with a mean diameter of 100 nm and have the characteristics required for targeted gene therapy. The complexes efficiently condense large amounts of plasmid per particle and successfully bind to Gal-3. The in vivo study shows that the complexes are biocompatible and safe for administration and can selectively transfect reactive glial cells of an induced cortical lesion. The results confirm that this PG-based delivery system is a promising platform for targeting Gal-3 overexpressing neuroinflammation cells for treating neuroinflammation-related injuries and neurodegenerative diseases. 相似文献
6.
Altair B. Agmata Kathleen Izza Marie B. Nopre Vivien C. Sarmiento Rizalinda L. De Leon 《International Journal of Hydrogen Energy》2021,46(27):14063-14072
Cellulase-mimetic solid acid catalysts (CMSAC), having both cellulose-binding and catalytic sites, are known to have much lower activation energy and higher catalytic activity than traditional solid acid catalysts. It is an emerging greener and cost-friendly solution for producing biofuel, such as bio-hydrogen, from lignocellulose. However, in 2018 the widely used CMSAC, sulfonated chloromethyl polystyrene, was found to have its catalytic activity attributed to the in-situ release of HCl during catalytic hydrolysis, which is unexpected. An ab initio quantum calculation based on density functional theory (DFT) is performed to study its reaction mechanism. Results have shown that the most probable mechanism responsible for the in-situ release of HCl is through SN1 nucleophilic substitution. The simulation also predicted a surface reaction activation energy of 1.56 eV (35.97 kcal/mol), along the predicted minimum energy path (MEP). This is the first ab initio study to theoretically predict the HCl leaching mechanism from CMSAC before its industrial application. 相似文献
7.
Carmen Candel Eduardo Vidal-Abarca Raquel Cerdán Marie Lippmann Susanne Narciss 《Journal of Computer Assisted Learning》2020,36(5):718-728
This study examines the effects of timing of corrective formative feedback on processing text information on question-answering. Undergraduate students read an expository text and answered questions in two attempts. Students were randomly assigned to a no feedback, immediate feedback and delayed feedback conditions. Students in the feedback conditions received feedback on the correctness of their answer after the first attempt and were informed about the right answer after the second attempt. Students were prompted to restudy the text after failing in their first attempt. However, students in the no feedback condition were just prompted to search the text. All students were tested on question-answering, corrective probability and a post-test cued-recall test. Results showed that: (a) feedback reduced the initial time reading the text; (b) feedback increased performance on question answering and cued-recall; (c) delayed feedback produced no advantages over immediate feedback. Theoretical and practical implications of these results are discussed. 相似文献
8.
Eline Saenen Nele Horemans Nathalie Vanhoudt Hildegarde Vandenhove Geert Biermans May Van Hees Jean Wannijn Jaco Vangronsveld Ann Cuypers 《International journal of molecular sciences》2015,16(6):12405-12423
To evaluate the environmental impact of uranium (U) contamination, it is important to investigate the effects of U at ecologically relevant conditions. Since U speciation, and hence its toxicity, strongly depends on environmental pH, the present study aimed to investigate dose-dependent effects of U at pH 7.5. Arabidopsis thaliana plants (Mouse-ear Cress) were exposed for three days to different U concentrations at pH 7.5. In the roots, the increased capacities of ascorbate peroxidase and glutathione reductase indicate an important role for the ascorbate-glutathione cycle during U-induced stress. However, a significant decrease in the ascorbate redox state was observed after exposure to 75 and 100 µM U, indicating that those roots are severely stressed. In accordance with the roots, the ascorbate-glutathione cycle plays an important role in the antioxidative defence systems in A. thaliana leaves exposed to U at pH 7.5 as the ascorbate and glutathione biosynthesis were upregulated. In addition, small inductions of enzymes of the antioxidative defence system were observed at lower U concentrations to counteract the U-induced stress. However, at higher U concentrations it seems that the antioxidative defence system of the leaves collapses as reductions in enzyme activities and gene expression levels were observed. 相似文献
9.