首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   335篇
  免费   24篇
  国内免费   2篇
电工技术   6篇
化学工业   135篇
金属工艺   2篇
机械仪表   3篇
建筑科学   11篇
矿业工程   1篇
能源动力   6篇
轻工业   97篇
水利工程   1篇
无线电   16篇
一般工业技术   38篇
冶金工业   8篇
自动化技术   37篇
  2023年   7篇
  2022年   30篇
  2021年   42篇
  2020年   19篇
  2019年   18篇
  2018年   14篇
  2017年   9篇
  2016年   9篇
  2015年   17篇
  2014年   14篇
  2013年   23篇
  2012年   20篇
  2011年   27篇
  2010年   19篇
  2009年   12篇
  2008年   18篇
  2007年   15篇
  2006年   12篇
  2005年   6篇
  2004年   4篇
  2003年   1篇
  2002年   3篇
  1998年   2篇
  1997年   1篇
  1994年   3篇
  1993年   2篇
  1991年   2篇
  1989年   2篇
  1986年   1篇
  1985年   1篇
  1982年   1篇
  1978年   1篇
  1977年   2篇
  1973年   1篇
  1972年   1篇
  1970年   1篇
  1947年   1篇
排序方式: 共有361条查询结果,搜索用时 15 毫秒
351.
The exponential increase in data over the past few years, particularly in images, has led to more complex content since visual representation became the new norm. E-commerce and similar platforms maintain large image catalogues of their products. In image databases, searching and retrieving similar images is still a challenge, even though several image retrieval techniques have been proposed over the decade. Most of these techniques work well when querying general image databases. However, they often fail in domain-specific image databases, especially for datasets with low intraclass variance. This paper proposes a domain-specific image similarity search engine based on a fused deep learning network. The network is comprised of an improved object localization module, a classification module to narrow down search options and finally a feature extraction and similarity calculation module. The network features both an offline stage for indexing the dataset and an online stage for querying. The dataset used to evaluate the performance of the proposed network is a custom domain-specific dataset related to cosmetics packaging gathered from various online platforms. The proposed method addresses the intraclass variance problem with more precise object localization and the introduction of top result reranking based on object contours. Finally, quantitative and qualitative experiment results are presented, showing improved image similarity search performance.  相似文献   
352.
353.
Cyanidin-3-glucoside (C3G) and cyanidin-3-rutinoside (C3R) are 2 major anthocyanins found in Korean Rubus fruits (blackberries, raspberries, and black raspberries). The antioxidant and antiinflammatory effects of C3G and C3R in RAW264.7 murine macrophage cells were determined. Anthocyanins (5, 10, and 20 μg/mL) significantly (p<0.05) reduced H2O2-induced cytotoxicity in H2O2-stimulated RAW264.7 cells, compared with control cells. Incubation with C3G or C3R significantly (p<0.05) decreased intracellular reactive oxygen species and DNA damage (Hoechst and comet assay), and the cellular ferric reducing antioxidant power also increased, compared with control cells. Nitric oxide production in LPS-stimulated RAW264.7 cells treated with C3G and C3R was reduced by 41.9 and 34.4%, respectively. In addition, LPS-induced prostaglandin E2 production was significantly (p<0.05) inhibited by C3G (51.7%) and C3R (58.6%), compared with LPS-stimulated control cells. Protein expressions of iNOS and COX-2 decreased in cells treated with anthocyanins. Anthocyanins down-regulated NF-κB expression and up-regulated I-κB expression in LPS-treated macrophages.  相似文献   
354.
355.
356.
Breast cancer is the most commonly diagnosed cancer worldwide and ranks first in terms of both prevalence and cancer-related mortality in women. In this study, we aimed to evaluate the anticancer effect of mebendazole (MBZ) and radiotherapy (RT) concomitant use in triple-negative breast cancer (TNBC) cells and elucidate the underlying mechanisms of action. Breast cancer mouse models and several types of breast cancer cells, including TNBC-derived RT-resistant (RT-R) MDA-MB-231 cells, were treated with MBZ and/or RT. In mice, changes in body weight, renal and liver toxicity, tumor volume, and number of lung metastases were determined. In cells, cell viability, colony formation, scratch wound healing, Matrigel invasion, and protein expression using western blotting were determined. Our findings showed that MBZ and RT combined treatment increased the anticancer effect of RT without additional toxicity. In addition, we noted that cyclin B1, PH2AX, and natural killer (NK) cell-mediated cytotoxicity increased following MBZ + RT treatment compared to unaided RT. Our results suggest that MBZ + RT have an enhanced anticancer effect in TNBC which acquires radiation resistance through blocking cell cycle progression, initiating DNA double-strand breaks, and promoting NK cell-mediated cytotoxicity.  相似文献   
357.
Photoactivation of aspartic acid-based carbon dots (Asp-CDs) induces the generation of spin-separated species, including electron/hole (e/h+) polarons and spin-coupled triplet states, as uniquely confirmed by the light-induced electron paramagnetic resonance spectroscopy. The relative population of the e/h+ pairs and triplet species depends on the solvent polarity, featuring a substantial stabilization of the triplet state in a non-polar environment (benzene). The electronic properties of the photoexcited Asp-CDs emerge from their spatial organization being interpreted as multi-layer assemblies containing a hydrophobic carbonaceous core and a hydrophilic oxygen and nitrogen functionalized surface. The system properties are dissected theoretically by density functional theory in combination with molecular dynamics simulations on quasi-spherical assemblies of size-variant flakelike model systems, revealing the importance of size dependence and interlayer effects. The formation of the spin-separated states in Asp-CDs enables the photoproduction of hydrogen peroxide (H2O2) from water and water/2-propanol mixture via a water oxidation reaction.  相似文献   
358.
Magnetic Resonance Materials in Physics, Biology and Medicine - Exploring mouse brains by rapid 3D-Diffusion Tensor Imaging (3D-DTI) of high spatial resolution (HSR) is challenging in vivo. Here we...  相似文献   
359.
In the model yeast Saccharomyces cerevisiae, Trk1 is the main K+ importer. It is involved in many important physiological processes, such as the maintenance of ion homeostasis, cell volume, intracellular pH, and plasma-membrane potential. The ScTrk1 protein can be of great interest to industry, as it was shown that changes in its activity influence ethanol production and tolerance in S. cerevisiae and also cell performance in the presence of organic acids or high ammonium under low K+ conditions. Nonconventional yeast species are attracting attention due to their unique properties and as a potential source of genes that encode proteins with unusual characteristics. In this work, we aimed to study and compare Trk proteins from Debaryomyces hansenii, Hortaea werneckii, Kluyveromyces marxianus, and Yarrowia lipolytica, four biotechnologically relevant yeasts that tolerate various extreme environments. Heterologous expression in S. cerevisiae cells lacking the endogenous Trk importers revealed differences in the studied Trk proteins' abilities to support the growth of cells under various cultivation conditions such as low K+ or the presence of toxic cations, to reduce plasma-membrane potential or to take up Rb+. Examination of the potential of Trks to support the stress resistance of S. cerevisiae wild-type strains showed that Y. lipolytica Trk1 is a promising tool for improving cell tolerance to both low K+ and high salt and that the overproduction of S. cerevisiae's own Trk1 was the most efficient at improving the growth of cells in the presence of highly toxic Li+ ions.  相似文献   
360.
A series of 3‐substituted pyrazinium tetrafluoroborates was prepared as simple analogues of flavinium salts which are efficient organocatalysts for oxidations with hydrogen peroxide. It was shown that pyrazinium derivatives with an electron‐withdrawing substituent catalyze mild oxidations of sulfides to sulfoxides and Baeyer–Villiger oxidations in a similar way to flavinium catalysts. The most reactive catalyst, 3‐cyanopyrazinium tetrafluoroborate, was efficiently employed in preparative sulfoxidations of aromatic and aliphatic sulfides as well as in Baeyer–Villiger oxidations of cyclobutanones. A proposed mechanism for the catalysis is based on the formation of pyrazine hydroperoxide which is the agent oxidizing the substrate.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号