全文获取类型
收费全文 | 133283篇 |
免费 | 11492篇 |
国内免费 | 6070篇 |
专业分类
电工技术 | 8042篇 |
技术理论 | 5篇 |
综合类 | 8771篇 |
化学工业 | 21199篇 |
金属工艺 | 7106篇 |
机械仪表 | 7974篇 |
建筑科学 | 10193篇 |
矿业工程 | 3030篇 |
能源动力 | 4013篇 |
轻工业 | 9480篇 |
水利工程 | 2564篇 |
石油天然气 | 6837篇 |
武器工业 | 1005篇 |
无线电 | 16926篇 |
一般工业技术 | 16797篇 |
冶金工业 | 6566篇 |
原子能技术 | 1556篇 |
自动化技术 | 18781篇 |
出版年
2024年 | 548篇 |
2023年 | 1999篇 |
2022年 | 3687篇 |
2021年 | 5118篇 |
2020年 | 3696篇 |
2019年 | 3151篇 |
2018年 | 3520篇 |
2017年 | 4128篇 |
2016年 | 3656篇 |
2015年 | 4893篇 |
2014年 | 6429篇 |
2013年 | 8044篇 |
2012年 | 8479篇 |
2011年 | 9451篇 |
2010年 | 8225篇 |
2009年 | 7913篇 |
2008年 | 7868篇 |
2007年 | 7510篇 |
2006年 | 7442篇 |
2005年 | 6107篇 |
2004年 | 4269篇 |
2003年 | 3974篇 |
2002年 | 4247篇 |
2001年 | 3665篇 |
2000年 | 3202篇 |
1999年 | 3284篇 |
1998年 | 2805篇 |
1997年 | 2413篇 |
1996年 | 2250篇 |
1995年 | 1844篇 |
1994年 | 1481篇 |
1993年 | 1188篇 |
1992年 | 901篇 |
1991年 | 677篇 |
1990年 | 554篇 |
1989年 | 446篇 |
1988年 | 406篇 |
1987年 | 275篇 |
1986年 | 205篇 |
1985年 | 175篇 |
1984年 | 123篇 |
1983年 | 92篇 |
1982年 | 88篇 |
1981年 | 72篇 |
1980年 | 61篇 |
1979年 | 45篇 |
1978年 | 32篇 |
1977年 | 32篇 |
1976年 | 55篇 |
1973年 | 21篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Kang Zhang Rong‐rong Wang Kai‐rui Zhang Fei Cheng Yu Tian Yi Lin Mi Zhou Pu‐xin Zhu 《Polymer International》2020,69(3):274-279
A series of hyperbranched poly(citric polyethylene glycol) (PCPEG) materials with varied polyethylene glycol (PEG) chain lengths as plasticizers were mixed with maize starch (MS) via cooking and film‐forming. The structure, pasting property, plasticization, aging property, moisture absorption and compatibility of plasticized starches were studied by means of Fourier transform infrared spectroscopy, X‐ray diffraction, rapid viscosity analysis, tension testing, moisture absorption measurements and scanning electron microscopy. Compared with PEG and citric acid, PCPEG was more effective in promoting starch chain movement and inhibiting the retrogradation of starch film. Also, PCPEG/MS had smaller moisture content. The longer the plasticizer chain, the better were the aging resistance and moisture resistance of starch. But with an increase of PEG chain length, mechanical properties of PCPEG/MS deteriorated and the compatibility between PCPEG and MS decreased. The hyperbranched derivative of PEG with longer chain exhibited improved plasticization and compatibility with starch. © 2019 Society of Chemical Industry 相似文献
22.
23.
24.
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
25.
26.
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
27.
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
28.
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
29.
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
30.