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   7944篇
  免费   1630篇
  国内免费   670篇
电工技术   1029篇
综合类   744篇
化学工业   1113篇
金属工艺   320篇
机械仪表   386篇
建筑科学   275篇
矿业工程   134篇
能源动力   296篇
轻工业   381篇
水利工程   93篇
石油天然气   399篇
武器工业   91篇
无线电   1545篇
一般工业技术   836篇
冶金工业   353篇
原子能技术   43篇
自动化技术   2206篇
  2024年   40篇
  2023年   233篇
  2022年   329篇
  2021年   429篇
  2020年   458篇
  2019年   468篇
  2018年   339篇
  2017年   398篇
  2016年   429篇
  2015年   414篇
  2014年   587篇
  2013年   594篇
  2012年   624篇
  2011年   569篇
  2010年   460篇
  2009年   483篇
  2008年   453篇
  2007年   478篇
  2006年   400篇
  2005年   308篇
  2004年   245篇
  2003年   219篇
  2002年   196篇
  2001年   184篇
  2000年   153篇
  1999年   116篇
  1998年   90篇
  1997年   81篇
  1996年   61篇
  1995年   62篇
  1994年   77篇
  1993年   58篇
  1992年   45篇
  1991年   18篇
  1990年   20篇
  1989年   33篇
  1988年   17篇
  1987年   8篇
  1986年   5篇
  1985年   8篇
  1984年   14篇
  1983年   8篇
  1982年   7篇
  1981年   3篇
  1980年   7篇
  1979年   6篇
  1978年   2篇
  1977年   3篇
  1956年   1篇
  1951年   2篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Small object detection is challenging and far from satisfactory. Most general object detectors suffer from two critical issues with small objects: (1) Feature extractor based on classification network cannot express the characteristics of small objects reasonably due to insufficient appearance information of targets and a large amount of background interference around them. (2) The detector requires a much higher location accuracy for small objects than for general objects. This paper proposes an effective and efficient small object detector YOLSO to address the above problems. For feature representation, we analyze the drawbacks in previous backbones and present a Half-Space Shortcut(HSSC) module to build a background-aware backbone. Furthermore, a coarse-to-fine Feature Pyramid Enhancement(FPE) module is introduced for layer-wise aggregation at a granular level to enhance the semantic discriminability. For loss function, we propose an exponential L1 loss to promote the convergence of regression, and a focal IOU loss to focus on prime samples with high classification confidence and high IOU. Both of them significantly improves the location accuracy of small objects. The proposed YOLSO sets state-of-the-art results on two typical small object datasets, MOCOD and VeDAI, at a speed of over 200 FPS. In the meantime, it also outperforms the baseline YOLOv3 by a wide margin on the common COCO dataset.  相似文献   
2.
Tumor cell aggregation is critical for cell survival following the loss of extracellular matrix attachment and dissemination. However, the underlying mechanotransduction of clustering solitary tumor cells is poorly understood, especially in non-small cell lung cancers (NSCLC). Here, we examined whether cell surface protrusions played an important role in facilitating the physical contact between floating cells detached from a substrate. We employed poly-2-hydroxyethyl methacrylate-based 3D culture methods to mimic in vivo tumor cell cluster formation. The suprastructural analysis of human NSCLC A549 cell spheroids showed that finger-like protrusions clung together via the actin cytoskeleton. Time-lapse holotomography demonstrated that the finger-like protrusions of free-floating cells in 3D culture displayed exploratory coalescence. Global gene expression analysis demonstrated that the genes in the organic hydroxyl transport were particularly enriched in the A549 cell spheroids. Particularly, the knockdown of the water channel aquaporin 3 gene (AQP3) impaired multicellular aggregate formation in 3D culture through the rearrangement of the actomyosin cytoskeleton. Moreover, the cells with reduced levels of AQP3 decreased their transmigration. Overall, these data indicate that cell detachment-upregulated AQP3 contributes to cell surface protrusions through actomyosin cytoskeleton remodeling, causing the aggressive aggregation of free-floating cells dependent on the property of the substratum and collective metastasis.  相似文献   
3.
Thyromimetics, whose physicochemical characteristics are analog to thyroid hormones (THs) and their derivatives, are promising candidates as novel therapeutics for neurodegenerative and metabolic pathologies. In particular, sobetirome (GC-1), one of the initial halogen-free thyromimetics, and newly synthesized IS25 and TG68, with optimized ADME-Tox profile, have recently attracted attention owing to their superior therapeutic benefits, selectivity, and enhanced permeability. Here, we further explored the functional capabilities of these thyromimetics to inhibit transthyretin (TTR) amyloidosis. TTR is a homotetrameric transporter protein for THs, yet it is also responsible for severe amyloid fibril formation, which is facilitated by tetramer dissociation into non-native monomers. By combining nuclear magnetic resonance (NMR) spectroscopy, computational simulation, and biochemical assays, we found that GC-1 and newly designed diphenyl-methane-based thyromimetics, namely IS25 and TG68, are TTR stabilizers and efficient suppressors of TTR aggregation. Based on these observations, we propose the novel potential of thyromimetics as a multi-functional therapeutic molecule for TTR-related pathologies, including neurodegenerative diseases.  相似文献   
4.
In this paper, we extend the Bonferroni mean (BM) operator with the picture fuzzy numbers (PFNs) to propose novel picture fuzzy aggregation operators and demonstrate their application to multicriteria decision making (MCDM). On the basis of the algebraic operational rules of PFNs and BM, we introduce some aggregation operators: the picture fuzzy Bonferroni mean, the picture fuzzy normalized weighted Bonferroni mean, and the picture fuzzy ordered weighted Bonferroni mean. Then, a new picture fuzzy MCDM method is proposed with the help of the proposed operators. Lastly, a practical application of proposed model is given to verify the developed model and related results of the proposed model is compared with the results of the existing models to indicate its applicability.  相似文献   
5.
四川盆地大多数气藏属于裂缝孔隙型气藏,气藏非均质性强.经典的径向均质复合试井解释模型与气藏实际情况不相符,解释结果与实际地质情况出现抵触现象.针对这种情况,建立了多区双重孔隙介质复合地层模型,求得了该模型的拉氏空间解,分析了其典型的压力动态特征,并对影响因素可能对曲线产生的影响进行了分析.  相似文献   
6.
This letter presents a new polarizer which has a simple comb structure inside a circular waveguide. The electrical performance of the proposed comb polarizer is optimized by a circular waveguide radius and by the physical parameters of the comb plates. This polarizer is suitable for providing good performance in millimeter‐band application because of its simple structure and low fabrication cost. In our experiments the dual‐band comb polarizer designed in band 1(K) and band 2(Ka) showed good electrical performance without any tuning elements.  相似文献   
7.
Attribute Allocation and Retrieval Scheme for Large-Scale Sensor Networks   总被引:1,自引:0,他引:1  
Wireless sensor network is an emerging technology that enables remote monitoring of large geographical regions. In this paper, we address the problem of distributing attributes over such a large-scale sensor network so that the cost of data retrieval is minimized. The proposed scheme is a data-centric storage scheme where the attributes are distributed over the network depending on the correlations between them. The problem addressed here is similar to the Allocation Problem of distributed databases. In this paper, we have defined the Allocation Problem in the context of sensor networks and have proposed a scheme for finding a good distribution of attributes to the sensor network. We also propose an architecture for query processing given such a distribution of attributes. We analytically determine the conditions under which the proposed architecture is beneficial and present simulation results to demonstrate the same. To the best of our knowledge, this is the first attempt to determine an allocation of attributes over a sensor network based on the correlations between attributes.  相似文献   
8.
IEEE 802.11g性能分析及应用   总被引:1,自引:1,他引:0  
全面介绍IEEE802.11g标准的无线局域网,详细讲述IEEE802.11g草案标准的概念、产生背景、特点、构件及其体系结构和发展前景,探讨实现IEEE802.11gWLAN所需的关键技术及其双频多模应用方式,同时分析IEEE802.11g标准的网络性能。  相似文献   
9.
The feature scale planarization of the copper chemical mechanical planarization (CMP) process has been characterized for two copper processes using Hitachi 430-TU/Hitachi T605 and Cabot 5001/Arch Cu10K consumables. The first process is an example of an abrasive-free polish with a high-selectivity barrier slurry, while the second is an example of a conventional abrasive slurry with a low-selectivity barrier slurry. Copper fill planarization has been characterized for structures with conformal deposition as well as with bumps resulting from bottom-up fill. Dishing and erosion were characterized for several structures after clearing. The abrasive-free polish resulted in low sensitivity to overpolish and low saturation levels for dishing and erosion. Consequently, this demonstrated superior performance when compared to the International Technology Roadmap for Semiconductors (ITRS) 2000 roadmap targets for planarization. While the conventional slurry could achieve the 0.13-μm technology node requirements, the abrasive-free polish met the planarization requirements beyond the 0.10-μm technology node.  相似文献   
10.
本文报导一种新型的光纤氧、二氧化碳复合传感器.通过在同一敏感膜载体上固定两种不同的荧光试剂——芘丁酸及羟基芘三磺酸,制作了一种对氧和二氧化碳敏感的复合敏感膜.该传感器在医学临床检验范围内具有良好的线性,其测氧的分辩率是0.1%,测二氧化碳的分辩率是0.5%,响应时间短于1min.文中还讨论了三种敏感膜载体的比较及复合传感器测量进程中氧和二氧化碳的相互干扰问题.  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