全文获取类型
收费全文 | 116698篇 |
免费 | 18324篇 |
国内免费 | 8068篇 |
专业分类
电工技术 | 13725篇 |
技术理论 | 1篇 |
综合类 | 8145篇 |
化学工业 | 21107篇 |
金属工艺 | 3570篇 |
机械仪表 | 7201篇 |
建筑科学 | 6172篇 |
矿业工程 | 4845篇 |
能源动力 | 2290篇 |
轻工业 | 17017篇 |
水利工程 | 1896篇 |
石油天然气 | 5462篇 |
武器工业 | 936篇 |
无线电 | 9994篇 |
一般工业技术 | 8775篇 |
冶金工业 | 4730篇 |
原子能技术 | 1157篇 |
自动化技术 | 26067篇 |
出版年
2024年 | 593篇 |
2023年 | 2337篇 |
2022年 | 4739篇 |
2021年 | 6733篇 |
2020年 | 4860篇 |
2019年 | 4213篇 |
2018年 | 4113篇 |
2017年 | 5014篇 |
2016年 | 6403篇 |
2015年 | 7260篇 |
2014年 | 8757篇 |
2013年 | 8514篇 |
2012年 | 9225篇 |
2011年 | 8133篇 |
2010年 | 6202篇 |
2009年 | 6166篇 |
2008年 | 5854篇 |
2007年 | 7689篇 |
2006年 | 7196篇 |
2005年 | 5946篇 |
2004年 | 4339篇 |
2003年 | 3955篇 |
2002年 | 2967篇 |
2001年 | 2312篇 |
2000年 | 2022篇 |
1999年 | 1475篇 |
1998年 | 1009篇 |
1997年 | 826篇 |
1996年 | 730篇 |
1995年 | 597篇 |
1994年 | 457篇 |
1993年 | 334篇 |
1992年 | 320篇 |
1991年 | 246篇 |
1990年 | 246篇 |
1989年 | 178篇 |
1988年 | 108篇 |
1987年 | 104篇 |
1986年 | 94篇 |
1985年 | 94篇 |
1984年 | 97篇 |
1983年 | 69篇 |
1982年 | 51篇 |
1981年 | 50篇 |
1980年 | 64篇 |
1979年 | 26篇 |
1966年 | 25篇 |
1964年 | 35篇 |
1962年 | 64篇 |
1959年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
11.
12.
Anna Stasiowicz Natalia Rosiak Ewa Tykarska Maciej Kozak Jacek Jenczyk Piotr Szulc Joanna Kobus-Cisowska Kornelia Lewandowska Anita Paziska Wojciech Paziski Judyta Cielecka-Piontek 《International journal of molecular sciences》2021,22(8)
Piperine is an alkaloid that has extensive pharmacological activity and impacts other active substances bioavailability due to inhibition of CYP450 enzymes, stimulation of amino acid transporters and P-glycoprotein inhibition. Low solubility and the associated low bioavailability of piperine limit its potential. The combination of piperine with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) causes a significant increase in its solubility and, consequently, an increase in permeability through gastrointestinal tract membranes and the blood–brain barrier. X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) were used to characterize interactions between piperine and HP-β-CD. The observed physicochemical changes should be combined with the process of piperine and CD system formation. Importantly, with an increase in solubility and permeability of piperine as a result of interaction with CD, it was proven to maintain its biological activity concerning the antioxidant potential (2,2-diphenyl-1-picryl-hydrazyl-hydrate assay), inhibition of enzymes essential for the inflammatory process and for neurodegenerative changes (hyaluronidase, acetylcholinesterase, butyrylcholinesterase). 相似文献
13.
14.
To save bandwidth and storage space as well as speed up data transmission, people usually perform lossy compression on images. Although the JPEG standard is a simple and effective compression method, it usually introduces various visually unpleasing artifacts, especially the notorious blocking artifacts. In recent years, deep convolutional neural networks (CNNs) have seen remarkable development in compression artifacts reduction. Despite the excellent performance, most deep CNNs suffer from heavy computation due to very deep and wide architectures. In this paper, we propose an enhanced wide-activated residual network (EWARN) for efficient and accurate image deblocking. Specifically, we propose an enhanced wide-activated residual block (EWARB) as basic construction module. Our EWARB gives rise to larger activation width, better use of interdependencies among channels, and more informative and discriminative non-linearity activation features without more parameters than residual block (RB) and wide-activated residual block (WARB). Furthermore, we introduce an overlapping patches extraction and combination (OPEC) strategy into our network in a full convolution way, leading to large receptive field, enforced compatibility among adjacent blocks, and efficient deblocking. Extensive experiments demonstrate that our EWARN outperforms several state-of-the-art methods quantitatively and qualitatively with relatively small model size and less running time, achieving a good trade-off between performance and complexity. 相似文献
15.
Alexander Detzner Martin Eigner 《Quality and Reliability Engineering International》2021,37(1):335-351
Manufacturing companies not only strive to deliver flawless products but also monitor product failures in the field to identify potential quality issues. When product failures occur, quality engineers must identify the root cause to improve any affected product and process. This root-cause analysis can be supported by feature selection methods that identify relevant product attributes, such as manufacturing dates with an increased number of product failures. In this paper, we present different methods for feature selection and evaluate their ability to identify relevant product attributes in a root-cause analysis. First, we compile a list of feature selection methods. Then, we summarize the properties of product attributes in warranty case data and discuss these properties regarding the challenges they pose for machine learning algorithms. Next, we simulate datasets of warranty cases, which emulate these product properties. Finally, we compare the feature selection methods based on these simulated datasets. In the end, the univariate filter information gain is determined to be a suitable method for a wide range of applications. The comparison based on simulated data provides a more general result than other publications, which only focus on a single use case. Due to the generic nature of the simulated datasets, the results can be applied to various root-cause analysis processes in different quality management applications and provide a guideline for readers who wish to explore machine learning methods for their analysis of quality data. 相似文献
16.
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
17.
18.
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
19.
目的 为了解决目前三维数据隐藏算法不能兼顾无失真和盲提取的问题,提出一种新的完全无失真的三维网格模型数据隐藏盲算法。方法 首先使用混沌逻辑映射选择嵌入与提取模式,保证数据的安全性。然后利用面元素重排,完全不会造成三维模型失真的性质,通过不同嵌入模式规则对三角面元素进行重排,以嵌入秘密数据。接收端则可根据相应的提取模式规则提取秘密数据。结果 仿真结果与分析表明,该算法不会对三维模型造成任何失真,嵌入容量为每顶点2比特,且能抵抗仿射变换攻击、噪声攻击和平滑攻击等。结论 这种三维数据隐藏盲算法无失真,容量大、安全性高、鲁棒性强,适用于三维载体不容修改的情形,如军事、医学、秘密通信和版权保护等。 相似文献
20.