全文获取类型
收费全文 | 6057篇 |
免费 | 413篇 |
国内免费 | 47篇 |
专业分类
电工技术 | 82篇 |
综合类 | 32篇 |
化学工业 | 1598篇 |
金属工艺 | 184篇 |
机械仪表 | 282篇 |
建筑科学 | 265篇 |
矿业工程 | 12篇 |
能源动力 | 293篇 |
轻工业 | 507篇 |
水利工程 | 119篇 |
石油天然气 | 82篇 |
武器工业 | 3篇 |
无线电 | 620篇 |
一般工业技术 | 997篇 |
冶金工业 | 226篇 |
原子能技术 | 46篇 |
自动化技术 | 1169篇 |
出版年
2024年 | 21篇 |
2023年 | 79篇 |
2022年 | 150篇 |
2021年 | 306篇 |
2020年 | 332篇 |
2019年 | 390篇 |
2018年 | 490篇 |
2017年 | 417篇 |
2016年 | 392篇 |
2015年 | 247篇 |
2014年 | 448篇 |
2013年 | 678篇 |
2012年 | 470篇 |
2011年 | 487篇 |
2010年 | 311篇 |
2009年 | 294篇 |
2008年 | 188篇 |
2007年 | 141篇 |
2006年 | 107篇 |
2005年 | 67篇 |
2004年 | 51篇 |
2003年 | 41篇 |
2002年 | 27篇 |
2001年 | 28篇 |
2000年 | 24篇 |
1999年 | 28篇 |
1998年 | 33篇 |
1997年 | 29篇 |
1996年 | 29篇 |
1995年 | 30篇 |
1994年 | 15篇 |
1993年 | 18篇 |
1992年 | 12篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 12篇 |
1985年 | 6篇 |
1984年 | 11篇 |
1982年 | 8篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1975年 | 3篇 |
1973年 | 5篇 |
1971年 | 6篇 |
1970年 | 8篇 |
1969年 | 4篇 |
1967年 | 2篇 |
排序方式: 共有6517条查询结果,搜索用时 0 毫秒
31.
Reza Eghtedaei Mahdi Abdi-khanghah Behnoosh S.A. Najar 《Petroleum Science and Technology》2017,35(17):1731-1736
Diluting the bitumen and heavy oil with a liquid solvent such as tetradecane is one way to decrease the viscosity. The accurate estimation for the viscosity of the aforesaid mixture is serious due to the sensitivity of enhanced oil recovery method. The main aim of this study was to propose an impressive relation between the viscosity of heavy n-alkane and Athabasca bitumen mixtures based on pressure, temperature, and the weight percentage of n-tetradecane using radial basis function artificial neural network (RBF-ANN). Also, this model has been compared with previous equations and its major accuracy was evidenced to estimate the viscosity. The amounts of mean relative error (MRE %) and R-squared received 0.32 and 1.00, respectively. The endeavors confirmed amazing forecasting skill of RBF-ANN for the approximation of the viscosity as a function of temperature, pressure, and the weight percentage of n-tetradecane. 相似文献
32.
Mohammad Reza Zaeri Rohallah Hashemi Hamidreza Shahverdi Mehdi Sadeghi 《石油科学(英文版)》2018,15(3):564-576
An experimental study was performed to investigate the impact of low salinity water on wettability alteration in carbonate core samples from southern Iranian reservoirs by spontaneous imbibition. In this paper, the effect of temperature, salinity, permeability and connate water were investigated by comparing the produced hydrocarbon curves. Contact angle measurements were taken to confirm the alteration of surface wettability of porous media. Oil recovery was enhanced by increasing the dilution ratio of sea water, and there existed an optimum dilution ratio at which the highest oil recovery was achieved. In addition, temperature had a very significant impact on oil recovery from carbonate rocks. Furthermore, oil recovery from a spontaneous imbibition process was directly proportional to the permeability of the core samples. The presence of connate water saturation inside the porous media facilitated oil production significantly. Also, the oil recovery from porous media was highly dependent on ion repulsion/attraction activity of the rock surface which directly impacts on the wettability conditions. Finally, the highest ion attraction percentage was measured for sodium while there was no significant change in pH for all experiments. 相似文献
33.
Hamid Reza Shokouhfar Hamed Jooypa Daryoosh Dideban 《Analog Integrated Circuits and Signal Processing》2018,95(2):295-306
In this paper, the context of modeling of the impact of mismatch and statistical variations on analogue circuit building blocks is emphasized. The aim is to develop a new algorithm which predicts the statistical behavior of important parameters of an amplifier including output resistance, voltage gain and trans-conductance. The relative error of standard deviation of statistical parameters will remain less than 5% compared with the most accurate Monte-Carlo (MC) simulations using atomistic library model-cards. In comparison with other models which are based on the normal distribution of parameters, the proposed model does not need this limiting presumption. On the other hand, the proposed algorithm is more efficient compared with time consuming MC atomistic simulations. 相似文献
34.
Study of Physically Transient Insulating Materials as a Potential Platform for Transient Electronics and Bioelectronics 下载免费PDF全文
Handan Acar Simge Çınar Mahendra Thunga Michael R. Kessler Nastaran Hashemi Reza Montazami 《Advanced functional materials》2014,24(26):4135-4143
Controlled degradation and transiency of materials is of significant importance in the design and fabrication of degradable and transient biomedical and electronic devices and platforms. Here, the synthesis of programmable biodegradable and transient insulating polymer films is reported, which have sufficient physical and chemical properties to be used as substrates for the construction of transient electronics. The composite structure can be used as a means to control the dissolution and transiency rate of the polymer composite film. Experimental and computational studies demonstrate that the addition of gelatin or sucrose to a PVA polymer matrix can be used as a means to program and either slow or enhance the transiency of the composite. The dissolution of the polymer composites are fitted with inverse exponential functions of different time constants; the lower time constants are an indication of faster transiency of the polymer composite. The addition of gelatin results in larger time constants, whereas the addition of sucrose generally results in smaller time constants. 相似文献
35.
Jafri Syed Rehan Abbas Hamid Tehreem Mahmood Rabia Alam Muhammad Asjad Rafi Talha Ul Haque Muhammad Zeeshan Munir Muhammad Wasim 《Wireless Personal Communications》2019,106(4):2163-2177
Wireless Personal Communications - The number of aged and disabled people has been increasing worldwide. To look after these people is a big challenge in this era. However, scientists overcome the... 相似文献
36.
Moazzeni Shadi Khayyambashi Mohammad Reza Movahhedinia Naser 《Wireless Personal Communications》2019,109(1):645-656
Wireless Personal Communications - Software-Defined Networks (SDNs) are developed to compensate the complicated function of the controlling parts of the given network elements and making the... 相似文献
37.
Correction to: Cloud-based vehicular networks: a taxonomy,survey, and conceptual hybrid architecture
Jabbarpour Mohammad Reza Marefat Alireza Jalooli Ali Zarrabi Houman 《Wireless Networks》2019,25(2):913-913
Wireless Networks - The original version of this article unfortunately contained a mistake in the title. The correct title has been published with this erratum. 相似文献
38.
Shahram Derakhshan Mohammad Rezaee Hamid Sarrafha 《Nanoscale and Microscale Thermophysical Engineering》2015,19(3):206-220
Equilibrium molecular dynamics simulation was utilized to calculate the shear viscosity of monoatomic molecules liquid flow confined in a nanochannel in the pure state and their binary mixtures. The pure flow viscosity data of argon, krypton, and xenon were used to predict their binary mixture viscosities using prediction methods proposed in the literature. Each method was evaluated by comparison of its results with those obtained by validated molecular dynamics simulation at different temperatures. In addition, correlative methods for mixture viscosity estimation and temperature dependence models were evaluated and corresponding model parameters were obtained. Moreover, the relations representing mixture parameter values as a function of the pure ones were determined and evaluated according to their accuracy. 相似文献
39.
Rotation-invariant multiresolution texture analysis using radon and wavelet transforms. 总被引:1,自引:0,他引:1
Kourosh Jafari-Khouzani Hamid Soltanian-Zadeh 《IEEE transactions on image processing》2005,14(6):783-795
A new rotation-invariant texture-analysis technique using Radon and wavelet transforms is proposed. This technique utilizes the Radon transform to convert the rotation to translation and then applies a translation-invariant wavelet transform to the result to extract texture features. A kappa-nearest neighbors classifier is employed to classify texture patterns. A method to find the optimal number of projections for the Radon transform is proposed. It is shown that the extracted features generate an efficient orthogonal feature space. It is also shown that the proposed features extract both of the local and directional information of the texture patterns. The proposed method is robust to additive white noise as a result of summing pixel values to generate projections in the Radon transform step. To test and evaluate the method, we employed several sets of textures along with different wavelet bases. Experimental results show the superiority of the proposed method and its robustness to additive white noise in comparison with some recent texture-analysis methods. 相似文献
40.
An information fidelity criterion for image quality assessment using natural scene statistics. 总被引:11,自引:0,他引:11
Hamid Rahim Sheikh Alan Conrad Bovik Gustavo de Veciana 《IEEE transactions on image processing》2005,14(12):2117-2128
Measurement of visual quality is of fundamental importance to numerous image and video processing applications. The goal of quality assessment (QA) research is to design algorithms that can automatically assess the quality of images or videos in a perceptually consistent manner. Traditionally, image QA algorithms interpret image quality as fidelity or similarity with a "reference" or "perfecft" image in some perceptual space. Such "full-referenc" QA methods attempt to achieve consistency in quality prediction by modeling salient physiological and psychovisual features of the human visual system (HVS), or by arbitrary signal fidelity criteria. In this paper, we approach the problem of image QA by proposing a novel information fidelity criterion that is based on natural scene statistics. QA systems are invariably involved with judging the visual quality of images and videos that are meant for "human consumption." Researchers have developed sophisticated models to capture the statistics of natural signals, that is, pictures and videos of the visual environment. Using these statistical models in an information-theoretic setting, we derive a novel QA algorithm that provides clear advantages over the traditional approaches. In particular, it is parameterless and outperforms current methods in our testing. We validate the performance of our algorithm with an extensive subjective study involving 779 images. We also show that, although our approach distinctly departs from traditional HVS-based methods, it is functionally similar to them under certain conditions, yet it outperforms them due to improved modeling. The code and the data from the subjective study are available at. 相似文献