全文获取类型
收费全文 | 375733篇 |
免费 | 30041篇 |
国内免费 | 16468篇 |
专业分类
电工技术 | 21927篇 |
技术理论 | 48篇 |
综合类 | 26610篇 |
化学工业 | 62769篇 |
金属工艺 | 21804篇 |
机械仪表 | 23743篇 |
建筑科学 | 29115篇 |
矿业工程 | 12476篇 |
能源动力 | 10306篇 |
轻工业 | 25282篇 |
水利工程 | 7137篇 |
石油天然气 | 24577篇 |
武器工业 | 2932篇 |
无线电 | 40760篇 |
一般工业技术 | 41598篇 |
冶金工业 | 19651篇 |
原子能技术 | 3816篇 |
自动化技术 | 47691篇 |
出版年
2024年 | 1529篇 |
2023年 | 5832篇 |
2022年 | 10316篇 |
2021年 | 14498篇 |
2020年 | 10962篇 |
2019年 | 9006篇 |
2018年 | 10400篇 |
2017年 | 11660篇 |
2016年 | 10659篇 |
2015年 | 14533篇 |
2014年 | 18362篇 |
2013年 | 22046篇 |
2012年 | 23876篇 |
2011年 | 26480篇 |
2010年 | 23397篇 |
2009年 | 22133篇 |
2008年 | 21725篇 |
2007年 | 20700篇 |
2006年 | 21051篇 |
2005年 | 18579篇 |
2004年 | 12584篇 |
2003年 | 11279篇 |
2002年 | 10502篇 |
2001年 | 9324篇 |
2000年 | 9218篇 |
1999年 | 9924篇 |
1998年 | 7597篇 |
1997年 | 6488篇 |
1996年 | 6144篇 |
1995年 | 5058篇 |
1994年 | 4153篇 |
1993年 | 2829篇 |
1992年 | 2220篇 |
1991年 | 1675篇 |
1990年 | 1291篇 |
1989年 | 1057篇 |
1988年 | 894篇 |
1987年 | 569篇 |
1986年 | 439篇 |
1985年 | 278篇 |
1984年 | 221篇 |
1983年 | 173篇 |
1982年 | 142篇 |
1981年 | 85篇 |
1980年 | 103篇 |
1979年 | 53篇 |
1978年 | 21篇 |
1977年 | 28篇 |
1976年 | 32篇 |
1973年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
In the field of images and imaging, super-resolution (SR) reconstruction of images is a technique that converts one or more low-resolution (LR) images into a highresolution (HR) image. The classical two types of SR methods are mainly based on applying a single image or multiple images captured by a single camera. Microarray camera has the characteristics of small size, multi views, and the possibility of applying to portable devices. It has become a research hotspot in image processing. In this paper, we propose a SR reconstruction of images based on a microarray camera for sharpening and registration processing of array images. The array images are interpolated to obtain a HR image initially followed by a convolution neural network (CNN) procedure for enhancement. The convolution layers of our convolution neural network are 3×3 or 1×1 layers, of which the 1×1 layers are used to improve the network performance particularly. A bottleneck structure is applied to reduce the parameter numbers of the nonlinear mapping and to improve the nonlinear capability of the whole network. Finally, we use a 3×3 deconvolution layer to significantly reduce the number of parameters compared to the deconvolution layer of FSRCNN-s. The experiments show that the proposed method can not only ameliorate effectively the texture quality of the target image based on the array images information, but also further enhance the quality of the initial high resolution image by the improved CNN. 相似文献
62.
A size-dependent governing equation is derived to investigate the torsional static behaviors of two-dimensionally functionally graded microtubes based on the modified couple stress theory. The shear modulus is assumed to vary along the tube’s length direction according to an exponential distribute function, and varies along the tube’s radius direction according to a power-law function. A generalized differential quadrature method is developed to determine the rotational angle and shear stresses. Some illustrative examples are given to investigate the effects of applied torques, the length scale parameter and various material compositions on the torsional angle and shear stresses. 相似文献
63.
In this paper, we first re-examine the previous protocol of controlled quantum secure direct communication of Zhang et al.’s scheme, which was found insecure under two kinds of attacks, fake entangled particles attack and disentanglement attack. Then, by changing the party of the preparation of cluster states and using unitary operations, we present an improved protocol which can avoid these two kinds of attacks. Moreover, the protocol is proposed using the three-qubit partially entangled set of states. It is more efficient by only using three particles rather than four or even more to transmit one bit secret information. Given our using state is much easier to prepare for multiqubit states and our protocol needs less measurement resource, it makes this protocol more convenient from an applied point of view. 相似文献
64.
Yue Gao Miao-miao Zhang Xiao-peng Guo Wen-jian Li Dong Lu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(5):1290-1297
Toxicity caused by the accumulation of butanol in fermentation media is an important factor limiting the concentration of butanol. There is currently no systematic research in place investigating the butanol tolerance mechanism of bacteria such as Clostridium acetobutylicum, which adapts to butanol stress and regulates its growth and metabolism. Here, research results related to the butanol tolerance of C. acetobutylicum are reviewed to understand the molecular basis of changes in butanol-tolerant strains. Organic solvent-tolerant bacteria play an important role in the fields of biofuel production, enzyme preparation and bioremediation. An analysis of limitations of the application of organic solvent-tolerant bacteria has revealed that future research should focus on combining the microbial tolerance phenotype with specific utilization to achieve an optimal balance between organic solvent tolerance and production. This review serves as a reference for the improvement and engineering of strains that tolerate organic solvents. © 2019 Society of Chemical Industry 相似文献
65.
66.
Xiao-Guang Yue Guang Zhang Qu Wu Fei Li Xian-Feng Chen Gao-Feng Ren Mei Li 《稀有金属(英文版)》2015,(2):125-132
In order to predict the wearing of stellite alloys,the related methods of rare metals data processing were discussed. The method of opposite degree(OD) algorithm was put forward to predict the wearing of stellite alloys.OD algorithm is based on prior numerical data, posterior numerical data and the opposite degree between numerical forecast data. To compare the performance of predicted results based on different algorithms, the back propagation(BP) and radial basis function(RBF) neural network methods were introduced. Predicted results show that the relative error of OD algorithm is smaller than those of BP and RBF neural network methods. OD algorithm is an effective method to predict the wearing of stellite alloys and it can be applied in practice. 相似文献
67.
综采工作面在推进过程中经常会受到断层的影响,严重制约了矿井的安全生产及经济效益。以寺河煤矿西井区W2303工作面采用留顶煤、割底矸等手段过逆断层群为工程实例,分析了综采工作面安全、快速过逆断层群技术的应用效果,对于类似矿山也有一定的借鉴价值。 相似文献
68.
69.
新汶矿业集团经过探索和实践,研究运用了差异互补式全掩护支护技术、掩护支架自牵引联动装置工艺、矿车运输、滑移运输多用轨道、自动找正装车平台、液控调整装置等新技术、新工艺,做到了液压支架综合流程快速回撤,实现了高效化、连贯化安全回撤,取得了良好的经济效益。 相似文献
70.
Zhang Huawei Yang Zhi Wu Zhaoyu Hong Xiaoyu Li Zhong Xu Yulai Li Jun Ni Gaojin Xiao Xueshan 《Oxidation of Metals》2019,92(1-2):49-65
Oxidation of Metals - The isothermal oxidation behavior and oxide-scale evolution on a newly developed Ni–Fe-based superalloy were investigated. Three oxidation stages were generally... 相似文献