全文获取类型
收费全文 | 70643篇 |
免费 | 22756篇 |
国内免费 | 1373篇 |
专业分类
电工技术 | 4079篇 |
技术理论 | 2篇 |
综合类 | 1986篇 |
化学工业 | 22790篇 |
金属工艺 | 1178篇 |
机械仪表 | 3608篇 |
建筑科学 | 4595篇 |
矿业工程 | 847篇 |
能源动力 | 2189篇 |
轻工业 | 7795篇 |
水利工程 | 913篇 |
石油天然气 | 693篇 |
武器工业 | 154篇 |
无线电 | 11573篇 |
一般工业技术 | 18277篇 |
冶金工业 | 1395篇 |
原子能技术 | 242篇 |
自动化技术 | 12456篇 |
出版年
2024年 | 75篇 |
2023年 | 252篇 |
2022年 | 484篇 |
2021年 | 975篇 |
2020年 | 3390篇 |
2019年 | 5914篇 |
2018年 | 5405篇 |
2017年 | 6058篇 |
2016年 | 6000篇 |
2015年 | 5934篇 |
2014年 | 6323篇 |
2013年 | 6455篇 |
2012年 | 5837篇 |
2011年 | 5486篇 |
2010年 | 4449篇 |
2009年 | 4040篇 |
2008年 | 3867篇 |
2007年 | 3860篇 |
2006年 | 3502篇 |
2005年 | 2930篇 |
2004年 | 2559篇 |
2003年 | 2498篇 |
2002年 | 2353篇 |
2001年 | 1972篇 |
2000年 | 1744篇 |
1999年 | 1071篇 |
1998年 | 295篇 |
1997年 | 222篇 |
1996年 | 162篇 |
1995年 | 123篇 |
1994年 | 102篇 |
1993年 | 96篇 |
1992年 | 64篇 |
1991年 | 44篇 |
1990年 | 49篇 |
1989年 | 34篇 |
1988年 | 28篇 |
1987年 | 26篇 |
1986年 | 27篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1974年 | 1篇 |
1959年 | 2篇 |
1957年 | 1篇 |
1956年 | 2篇 |
1954年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
101.
In this study, the effect of pendant pyrene on the optical and electronic properties of poly(2,5‐dithienylpyrrole)s was studied. For this purpose a new pyrene coupled 2,5‐dithienylpyrrole derivative (SNS‐pyrene) was synthesized through click reaction. SNS‐pyrene was electrochemically polymerized and its electrochemical and optical properties were investigated by electrochemical and optical techniques. The polymer had a band gap of 3.36 eV and displayed light green to blue color variation upon oxidation in less than 2.48 s. Additionally, electrochemical copolymerization of SNS‐pyrene with 3,4‐ethylenedioxythiophene was achieved whilst a detailed investigation was performed on the effect of electrochemical polymerization conditions on the optoelectronic properties of the copolymers. Studies revealed that the copolymers exhibit multichromic reversible redox behavior with lower band gaps and shorter switching times than their parent polymer, P(SNS‐pyrene) © 2014 Society of Chemical Industry. 相似文献
102.
Shogo Mamada Naoyuki Yaguchi Masanori Hansaka Masafumi Yamato Hirohisa Yoshida 《应用聚合物科学杂志》2015,132(15)
This study was addressed to the influence of an electric field strength applied at fabrication process and matrix properties, such as the dielectric constant and the Young's modulus, on “pseudo‐1‐3 piezoelectric ceramic/polymer composite” in order to further enhance the piezoelectricity of that. The pseudo‐1‐3 piezoelectric ceramic/polymer composite consists of linearly ordered piezoelectric ceramic particles in polymer material. Silicone gel, silicone rubber, urethane rubber, and poly‐methyl‐methacrylate, which exhibit different dielectric constants and Young's modulus, were used as matrices to evaluate the matrix influence. The piezoelectricity of the pseudo‐1‐3 piezoelectric ceramic/polymer composite was evaluated using the piezoelectric strain constant d33. The d33 is one of the indices of the piezoelectric properties for piezoelectric materials. As a result, it was confirmed that d33 of the pseudo‐1‐3 piezoelectric ceramic/polymer composite increased with the increase of the electric filed strength applied at fabrication process, though, it reached a constant value at a certain strength value. Further it was confirmed that dielectric constant of the matrix had a small influence on d33 of the pseudo‐1‐3 piezoelectric ceramic/polymer composite, however, in case of matrix of lower Young's modulus, d33 was increase. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41817. 相似文献
103.
Mohamed Abdellatif 《Color research and application》2015,40(6):564-576
The spectral overlap of color‐sampling filters increases errors when using a diagonal matrix transform, for color correction and reduces color distinction. Spectral sharpening is a transformation of colors that was introduced to reduce color‐constancy errors when the colors are collected through spectrally overlapping filters. The earlier color‐constancy methods improved color precision when the illuminant color is changed, but they overlooked the color distinction. In this article, we introduce a new spectral sharpening technique that has a good compromise of color precision and distinction, based on real physical constraints. The spectral overlap is measured through observing a gray reference chart with a set of real and spectrally disjoint filters selected by the user. The new sharpening method enables to sharpen colors obtained by a sensor without knowing the camera response functions. Experiments with real images showed that the colors sharpened by the new method have good levels of color precision and distinction as well. The color‐constancy performance is compared with the data‐based sharpening method in terms of both precision and distinction. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 564–576, 2015 相似文献
104.
Suitability,efficiency and microbiological safety of novel physical technologies for the processing of ready‐to‐eat meals,meats and pumpable products 下载免费PDF全文
Alexandros Ch. Stratakos Anastasios Koidis 《International Journal of Food Science & Technology》2015,50(6):1283-1302
Consumer studies and market reports show an increase in consumption of ready‐to‐eat (RTE) foods. Although conventional processing technologies can in most cases produce safe products, they can also lead to the degradation of nutritional compounds and negatively affect quality characteristics. Consumers strongly prefer food that is minimally processed with the maximum amount of health‐promoting substances. Novel processing technologies as pre‐ or post‐treatment decontamination methods or as substitutes of conventional technologies have the potential to produce foods that are safe, rich in nutrient content and with superior organoleptic properties. Combining novel with conventional processes can eliminate potential drawbacks of novel technologies. This review examines available scientific information and critically evaluates the suitability and efficiency of various novel thermal and nonthermal technologies in terms of microbial safety, quality as well as nutrient content on the production of RTE meals, meats and pumpable products. 相似文献
105.
106.
Haibo Zhang Guohua Geng Kang Li Cheng Liu Yuqing Hou 《Journal of Modern Optics》2018,65(20):2278-2289
Cone-beam X-ray luminescence computed tomography (CB-XLCT) is an attractive hybrid imaging modality, and it has the potential of monitoring the metabolic processes of nanophosphors-based drugs in vivo. However, the XLCT imaging suffers from a severe ill-posed problem. In this work, a sparse nonconvex Lp (0?p?1) regularization was utilized for the efficient reconstruction for early detection of small tumour in CB-XLCT imaging. Specifically, we transformed the non-convex optimization problem into an iteratively reweighted scheme based on the L1 regularization. Further, an iteratively reweighted split augmented lagrangian shrinkage algorithm (IRW_SALSA-Lp) was proposed to efficiently solve the non-convex Lp (0?p?1) model. We studied eight different non-convex p-values (1/16, 1/8, 1/4, 3/8, 1/2, 5/8, 3/4, 7/8) in both 3D digital mouse experiments and in vivo experiments. The results demonstrate that the proposed non-convex methods outperform L2 and L1 regularization in accurately recovering sparse targets in CB-XLCT. And among all the non-convex p-values, our Lp(1/4?p?1/2) methods give the best performance. 相似文献
107.
108.
109.
Alfredo M. Gravagnuolo Eden Morales‐Narváez Charlene Regina Santos Matos Sara Longobardi Paola Giardina Arben Merkoçi 《Advanced functional materials》2015,25(38):6084-6092
Class I hydrophobin Vmh2, a peculiar surface active and versatile fungal protein, is known to self‐assemble into chemically stable amphiphilic films, to be able to change wettability of surfaces, and to strongly adsorb other proteins. Herein, a fast, highly homogeneous and efficient glass functionalization by spontaneous self‐assembling of Vmh2 at liquid–solid interfaces is achieved (in 2 min). The Vmh2‐coated glass slides are proven to immobilize not only proteins but also nanomaterials such as graphene oxide (GO) and quantum dots (QDs). As models, bovine serum albumin labeled with Alexa 555 fluorophore, anti‐immunoglobulin G antibodies, and cadmium telluride QDs are patterned in a microarray fashion in order to demonstrate functionality, reproducibility, and versatility of the proposed substrate. Additionally, a GO layer is effectively and homogeneously self‐assembled onto the studied functionalized surface. This approach offers a quick and simple alternative to immobilize nanomaterials and proteins, which is appealing for new bioanalytical and nanobioenabled applications. 相似文献
110.
Differences between oculomotor and perceptual artifacts for temporally limited head mounted displays
Alexander Goettker Kevin J. MacKenzie T. Scott Murdison 《Journal of the Society for Information Display》2020,28(6):509-519
We used perceptual and oculomotor measures to understand the negative impacts of low (phantom array) and high (motion blur) duty cycles with a high‐speed, AR‐likehead‐mounted display prototype. We observed large intersubject variability for the detection of phantom array artifacts but a highly consistent and systematic effect on saccadic eye movement targeting during low duty cycle presentations. This adverse effect on saccade endpoints was also related to an increased error rate in a perceptual discrimination task, showing a direct effect of display duty cycle on the perceptual quality. For high duty cycles, the probability of detecting motion blur increased during head movements, and this effect was elevated at lower refresh rates. We did not find an impact of the temporal display characteristics on compensatory eye movements during head motion (e.g., VOR). Together, our results allow us to quantify the tradeoff of different negative spatiotemporal impacts of user movements and make subsequent recommendations for optimized temporal HMD parameters. 相似文献