全文获取类型
收费全文 | 60453篇 |
免费 | 6011篇 |
国内免费 | 3080篇 |
专业分类
电工技术 | 3520篇 |
技术理论 | 3篇 |
综合类 | 4313篇 |
化学工业 | 10107篇 |
金属工艺 | 3022篇 |
机械仪表 | 3679篇 |
建筑科学 | 4865篇 |
矿业工程 | 1551篇 |
能源动力 | 1795篇 |
轻工业 | 4815篇 |
水利工程 | 1160篇 |
石油天然气 | 3533篇 |
武器工业 | 482篇 |
无线电 | 7221篇 |
一般工业技术 | 7285篇 |
冶金工业 | 2601篇 |
原子能技术 | 722篇 |
自动化技术 | 8870篇 |
出版年
2024年 | 327篇 |
2023年 | 1072篇 |
2022年 | 1939篇 |
2021年 | 2746篇 |
2020年 | 2108篇 |
2019年 | 1755篇 |
2018年 | 1837篇 |
2017年 | 2162篇 |
2016年 | 1953篇 |
2015年 | 2537篇 |
2014年 | 3194篇 |
2013年 | 3790篇 |
2012年 | 3826篇 |
2011年 | 4227篇 |
2010年 | 3606篇 |
2009年 | 3275篇 |
2008年 | 3323篇 |
2007年 | 3078篇 |
2006年 | 3120篇 |
2005年 | 2510篇 |
2004年 | 1783篇 |
2003年 | 1941篇 |
2002年 | 2184篇 |
2001年 | 1929篇 |
2000年 | 1482篇 |
1999年 | 1515篇 |
1998年 | 1080篇 |
1997年 | 935篇 |
1996年 | 921篇 |
1995年 | 728篇 |
1994年 | 628篇 |
1993年 | 484篇 |
1992年 | 330篇 |
1991年 | 253篇 |
1990年 | 200篇 |
1989年 | 186篇 |
1988年 | 173篇 |
1987年 | 113篇 |
1986年 | 66篇 |
1985年 | 45篇 |
1984年 | 28篇 |
1983年 | 26篇 |
1982年 | 26篇 |
1981年 | 22篇 |
1980年 | 21篇 |
1979年 | 20篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1968年 | 4篇 |
1959年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
11.
Spinel LiSr0·1Cr0·1Mn1·8O4 was synthesised by high temperature solid state method in order to enhance the electrochemical performance. The LiSr0·1Cr0·1Mn1·8O4 (LSCMO) materials were characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. The XRD and SEM studies confirm that LSCMO had spinel crystal structure with a space group of Fd3m, and the particle of LSCMO shows irregular shape. The cyclic voltammetry data illustrated that the heavy current charge–discharge performance of LMO was improved by Sr2+ and Cr3+ doping. The galvanostatic charge–discharge of LSCMO cathode materials was measured at 1, 5, 10 and 20 C. The results indicated that LSCMO improved the capacity retention. 相似文献
12.
通过对普查区喜山期玄武岩喷发分布范围、形态的分析,对燕山晚期闪长玢岩分布范围、与构造关系、对煤层的影响等方面的分析,阐述了太平普查区岩浆活动特征。 相似文献
13.
This paper presents a spatio-temporal fusion method for remote sensing images by using a linear injection model and local neighbourhood information. In this method, the linear injection model is first introduced to generate an initial fused image, the spatial details are extracted from the fine-resolution image at the base date, and are weighted by a proper injection gains. Then, the spatial details and the relative spectral information from the coarse-resolution images are blended to generate the fusion result. To further enhance its robustness to the noise, the local neighbourhood information, derived from the fine-resolution image and the fused result simultaneously, is introduced to refine the initial fused image to obtain a more accurate prediction result. The algorithm can effectively capture phenology change or land-cover-type change with minimum input data. Simulated data and two types of real satellite images with seasonal changes and land-cover-type changes are employed to test the performance of the proposed method. Compared with a spatial and temporal adaptive reflectance fusion model (STARFM) and a flexible spatio-temporal fusion algorithm (FSDAF), results show that the proposed approach improves the accuracy of fused images in phenology change area and effectively captures land-cover-type reflectance changes. 相似文献
14.
Xiaopo Wu Yangming Shi Weibo Meng Xiaofei Ma Nian Fang 《International Journal of Satellite Communications and Networking》2019,37(3):283-291
Electromagnetic signal emitted by satellite communication (satcom) transmitters are used to identify specific individual uplink satcom terminals sharing the common transponder in real environment, which is known as specific emitter identification (SEI) that allows for early indications and warning (I&W) of the targets carrying satcom furnishment and furthermore the real time electromagnetic situation awareness in military operations. In this paper, the authors are the first to propose the identification of specific transmitters of satcom by using probabilistic neural networks (PNN) to reach the goal of target recognition. We have been devoted to the examination by exploring the feasibility of utilizing the Hilbert transform to signal preprocessing, applying the discrete wavelet transform to feature extraction, and employing the PNN to perform the classification of stationary signals. There are a total of 1000 sampling time series with binary phase shift keying (BPSK) modulation originated by five types of satcom transmitters in the test. The established PNNs classifier implements the data testing and finally yields satisfactory accuracy at 8 dB(±1 dB) carrier to noise ratio, which indicates the feasibility of our method, and even the keen insight of its application in military. 相似文献
15.
16.
Neural Computing and Applications - Traffic identification is currently an important challenge for network management and security. In this paper, we propose a novel application identification... 相似文献
17.
18.
To minimize the mass and increase the bearing failure load of composite doublelap bolted joints, a three-step optimization strategy including feasible region reduction,
optimization model decoupling and optimization was presented. In feasible region
reduction, the dimensions of the feasible design region were reduced by selecting dominant
design variables from numerous multilevel parameters by sensitivity analyses, and the
feasible regions of variables were reduced by influence mechanism analyses. In model
decoupling, the optimization model with a large number of variables was divided into
various sub-models with fewer variables by variance analysis. In the third step, the
optimization sub-models were solved one by one using a genetic algorithm, and the
modified characteristic curve method was adopted as the failure prediction method. Based
on the proposed optimization method, optimization of a double-lap single-bolt joint was
performed using the ANSYS® code. The results show that the bearing failure load increased
by 13.5% and that the mass decreased by 8.7% compared with those of the initial design of
the joint, which validated the effectiveness of the three-step optimization strategy. 相似文献
19.
20.
This study assessed the collection efficiency (CE) of two popularly used sampling devices (BioSampler and Coriolis sampler) for fungal aerosols. Phosphate‐buffered saline (PBS) supplemented with or without surfactant (Tween‐20, Tween‐80, or Triton X‐100) and antifoam agent was prepared and used as collection liquids. The agar impactor (BioStage) was simultaneously operated with liquid‐based samplers to collect fungi from seven sites located at a university building, public library, and animal farming. Fungal concentrations determined by liquid samplers were divided by those by BioStage, and the ratio values represented CE. Results indicate that the CE of BioSampler was superior to that of Coriolis (P = 0.0001) and the PBS containing surfactant collected fungi better than that without surfactant (P < 0.0001), whereas antifoam agent showed no influence (P = 0.8). Moreover, fungal concentrations determined by BioSampler with surfactant‐added PBS were statistically indifferent from those by BioStage (P > 0.05) with a Spearman correlation coefficient of 0.81‐0.83 (P < 0.01). In addition to sampler and collection liquid, sampling location was also identified as a significant CE factor (P = 0.006), implying potential influences by fungal genera in the studied fields. Overall, BioSampler with surfactant‐supplemented PBS (eg, Triton X‐100) is recommended considering the great CE and compatibility with a variety of analytical assays. 相似文献