全文获取类型
收费全文 | 130577篇 |
免费 | 11119篇 |
国内免费 | 6659篇 |
专业分类
电工技术 | 7388篇 |
技术理论 | 7篇 |
综合类 | 10895篇 |
化学工业 | 21191篇 |
金属工艺 | 7609篇 |
机械仪表 | 8172篇 |
建筑科学 | 9490篇 |
矿业工程 | 3801篇 |
能源动力 | 3803篇 |
轻工业 | 9742篇 |
水利工程 | 2493篇 |
石油天然气 | 7222篇 |
武器工业 | 994篇 |
无线电 | 14777篇 |
一般工业技术 | 14453篇 |
冶金工业 | 6280篇 |
原子能技术 | 1667篇 |
自动化技术 | 18371篇 |
出版年
2024年 | 452篇 |
2023年 | 1715篇 |
2022年 | 3123篇 |
2021年 | 4398篇 |
2020年 | 3405篇 |
2019年 | 3043篇 |
2018年 | 3334篇 |
2017年 | 3772篇 |
2016年 | 3535篇 |
2015年 | 4746篇 |
2014年 | 6265篇 |
2013年 | 7414篇 |
2012年 | 8379篇 |
2011年 | 9078篇 |
2010年 | 8466篇 |
2009年 | 8050篇 |
2008年 | 8020篇 |
2007年 | 7765篇 |
2006年 | 7648篇 |
2005年 | 6517篇 |
2004年 | 5117篇 |
2003年 | 4896篇 |
2002年 | 5774篇 |
2001年 | 4938篇 |
2000年 | 3580篇 |
1999年 | 3122篇 |
1998年 | 2164篇 |
1997年 | 1835篇 |
1996年 | 1786篇 |
1995年 | 1452篇 |
1994年 | 1065篇 |
1993年 | 795篇 |
1992年 | 623篇 |
1991年 | 474篇 |
1990年 | 375篇 |
1989年 | 273篇 |
1988年 | 259篇 |
1987年 | 162篇 |
1986年 | 99篇 |
1985年 | 89篇 |
1984年 | 79篇 |
1983年 | 57篇 |
1982年 | 44篇 |
1981年 | 33篇 |
1980年 | 40篇 |
1979年 | 18篇 |
1978年 | 10篇 |
1977年 | 14篇 |
1976年 | 15篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Energy transfer from photo-excited electrons in a metal thin film to the dielectric substrate is important for understanding the ultrafast heat transfer process across the two materials. Substantial research has been conducted to investigate heat transfer in a metal-dielectric structure. In this work, a two-temperature model in metal was used to analyze the interface electron and dielectric substrate coupling. An improved temperature and wavelength-dependent Drude–Lorentz model was implemented to interpret the signals obtained in optical measurements. Ultrafast pump-and-probe measurements on Au-Si samples were carried out, where the probe photon energy was chosen to be close to the interband transition threshold of gold to minimize the influence of non-equilibrium electrons on the optical response and maximize the thermal modulation to the optical reflectance. Electron-substrate interface thermal conductance at different pump laser fluences was obtained, and was found to increase with the interface temperature. 相似文献
52.
Process object is the instance of process. Vertexes and edges are in the graph of process object. There are different types of the object itself and the associations between object. For the large-scale data, there are many changes reflected. Recently, how to find appropriate real-time data for process object becomes a hot research topic. Data sampling is a kind of finding c hanges o f p rocess o bjects. There i s r equirements f or s ampling to be adaptive to underlying distribution of data stream. In this paper, we have proposed a adaptive data sampling mechanism to find a ppropriate d ata t o m odeling. F irst o f all, we use concept drift to make the partition of the life cycle of process object. Then, entity community detection is proposed to find changes. Finally, we propose stream-based real-time optimization of data sampling. Contributions of this paper are concept drift, community detection, and stream-based real-time computing. Experiments show the effectiveness and feasibility of our proposed adaptive data sampling mechanism for process object. 相似文献
53.
Yuxi Guo Xuefeng Chen Pin Gong Fuxin Chen Dandan Cui Mengrao Wang 《International Journal of Food Science & Technology》2021,56(10):4970-4982
In vitro digestion models are widely used to study the structural changes, digestion and release of food components under simulated gastrointestinal conditions. As compared to the in vivo digestion tests, the in vitro digestion reflects the digestion and utilisation of food after ingestion and has the advantages of being time consuming, inexpensive, reproducible and free from moral and ethical restrictions. This study reviewed the current research studies on the in vitro simulated digestion of polysaccharides conducted in the last 5 years and focused on the oral, gastric and intestinal digestion models, with the aim of providing a basis for the further testing of changes in the content, structure and active ingredients of polysaccharides before and after digestion. 相似文献
54.
Wei-Fei Hu Shuo Chen Hong-Chao Hao Hong Jiang 《American Institute of Chemical Engineers》2022,68(11):e17879
Herein, we propose a novel method to enhance the photoreactivity of an MOF catalyst by grafting isocyanate bonds ( NCO) and sulfhydryl-complexed copper ( SCu) onto ZIF-8 (NIF-SCu). The grafting process intercalated interlayer bands between the conduction and valence bands of ZIF-8, thereby providing a “ladder” for facile electron transition. The extreme improvement in the photoreactivity of NIF-SCu could be attributed to the enhancement in light responses in the range of 350–450 nm by NCO groups and the widening of the visible light range of the MOF by SCu groups. The formation of staggered energy levels in NIF-SCu could also narrow the band gap, lower the resistance, and facilitate the transfer of photogenerated carriers, thereby generating electrons with strong reduction potential in the SCu conduction band. This study provides a new strategy for improving or even endowing the photoactivity of environmental functional materials with wide bandgaps. 相似文献
55.
56.
57.
Gang Zheng Xiaoxuan Yu Haizuo Zhou Xinyu Yang Wei Guo Pengbo Yang 《Geotextiles and Geomembranes》2021,49(1):180-187
Incompressible dipping substrata are commonly encountered in engineering practice. Compared to horizontal underlying strata, the inclined underlying stratum increase the risk of collapse of embankments reinforced with columns because it weakens the restraint of the column base. The objective of this study is to investigate the effectiveness of geosynthetics on improving the embankment stability when the underlying stratum is inclined. The influence of geosynthetic tensile stiffness on the ultimate surcharge and failure mechanism is studied. A deep-seated failure with column tilting occurs when the geosynthetic tensile stiffness is low, whereas a lateral sliding occurs when the geosynthetic tensile stiffness is high. To illustrate the contribution of geosynthetics, the distribution of the lateral pressures acting on the columns is analyzed. 相似文献
58.
Junling Guo Huayu Pei Ying Dou Siyuan Zhao Guosheng Shao Jinping Liu 《Advanced functional materials》2021,31(18):2010499
Lithium-sulfur batteries (LSBs) are considered a promising next-generation energy storage device owing to their high theoretical energy density. However, their overall performance is limited by several critical issues such as lithium polysulfide (PS) shuttles, low sulfur utilization, and unstable Li metal anodes. Despite recent huge progress, the electrolyte/sulfur ratio (E/S) used is usually very high (≥20 µL mg−1), which greatly reduces the practical energy density of devices. To push forward LSBs from the lab to the industry, considerable attention is devoted to reducing E/S while ensuring the electrochemical performance. To date, however, few reviews have comprehensively elucidated the possible strategies to achieve that purpose. In this review, recent advances in low E/S cathodes and anodes based on the issues resulting from low E/S and the corresponding solutions are summarized. These will be beneficial for a systematic understanding of the rational design ideas and research trends of low E/S LSBs. In particular, three strategies are proposed for cathodes: preventing PS formation/aggregation to avoid inadequate dissolution, designing multifunctional macroporous networks to address incomplete infiltration, and utilizing an imprison strategy to relieve the adsorption dependence on specific surface area. Finally, the challenges and future prospects for low E/S LSBs are discussed. 相似文献
59.
Wu Ge Mu Yi Susilo Willy Guo Fuchun Zhang Futai 《International Journal of Information Security》2019,18(3):321-331
International Journal of Information Security - Data integrity is a critical security issue in cloud storage. The data integrity checking schemes by a third-party auditor (TPA) have attracted a lot... 相似文献
60.
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