全文获取类型
收费全文 | 111342篇 |
免费 | 8465篇 |
国内免费 | 4174篇 |
专业分类
电工技术 | 5828篇 |
技术理论 | 11篇 |
综合类 | 6580篇 |
化学工业 | 18938篇 |
金属工艺 | 5792篇 |
机械仪表 | 6664篇 |
建筑科学 | 8624篇 |
矿业工程 | 3075篇 |
能源动力 | 3097篇 |
轻工业 | 6618篇 |
水利工程 | 1710篇 |
石油天然气 | 6209篇 |
武器工业 | 691篇 |
无线电 | 13958篇 |
一般工业技术 | 14221篇 |
冶金工业 | 5893篇 |
原子能技术 | 1237篇 |
自动化技术 | 14835篇 |
出版年
2024年 | 431篇 |
2023年 | 1748篇 |
2022年 | 2877篇 |
2021年 | 3959篇 |
2020年 | 3041篇 |
2019年 | 2581篇 |
2018年 | 2981篇 |
2017年 | 3365篇 |
2016年 | 2930篇 |
2015年 | 3850篇 |
2014年 | 4882篇 |
2013年 | 6247篇 |
2012年 | 6552篇 |
2011年 | 7173篇 |
2010年 | 6240篇 |
2009年 | 6162篇 |
2008年 | 6157篇 |
2007年 | 5745篇 |
2006年 | 6034篇 |
2005年 | 5408篇 |
2004年 | 3691篇 |
2003年 | 3194篇 |
2002年 | 2847篇 |
2001年 | 2753篇 |
2000年 | 2870篇 |
1999年 | 3379篇 |
1998年 | 2910篇 |
1997年 | 2546篇 |
1996年 | 2286篇 |
1995年 | 1921篇 |
1994年 | 1552篇 |
1993年 | 1219篇 |
1992年 | 964篇 |
1991年 | 738篇 |
1990年 | 600篇 |
1989年 | 500篇 |
1988年 | 390篇 |
1987年 | 294篇 |
1986年 | 206篇 |
1985年 | 176篇 |
1984年 | 108篇 |
1983年 | 81篇 |
1982年 | 87篇 |
1981年 | 57篇 |
1980年 | 46篇 |
1979年 | 32篇 |
1978年 | 25篇 |
1977年 | 25篇 |
1976年 | 40篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Nan Wu Xiaodong Li Mu Zhang Yi Ren Qi Zhu Haijun Peng Hongqiang Ru Xudong Sun 《Journal of the European Ceramic Society》2021,41(4):2898-2907
Refining ceramic microstructures to the nanometric range to minimize light scattering provides an interesting methodology for developing novel optical ceramic materials. In this work, we reported the fabrication and properties of a new nanocomposite optical ceramic of Gd2O3-MgO. The citric acid sol-gel combustion method was adopted to fabricate Gd2O3-MgO nanocomposites with fine-grain sizes, dense microstructures and homogeneous phase domains. Nanopowders with low agglomeration and improved sinterability can be obtained by elaborating Φ values. Further refining of the microstructure of the nanocomposites was achieved by elaborating the hot-pressing conditions. The sample sintered at 65 MPa and 1300 °C showed a quite high hardness value of 14.3 ± 0.2 GPa, a high transmittance of 80.3 %–84.7 % over the 3?6 μm wavelength range, due mainly to its extremely fine-grain size of Gd2O3 and MgO (93 and 78 nm, respectively) and high density. 相似文献
22.
Shanshan Li Bing Zhang Xuxiang Feng Yewei Wu 《International journal of remote sensing》2019,40(14):5635-5650
Feature-based methods have been developed in the past decades for the registration of optical satellite images. However, it is still a challenging problem to handle well the registration between medium and high spatial resolution images due to the large difference of the spatial structural features and local details for the same objects. In this study, an automated co-registration technique is proposed that integrates an improved SIFT (I-SIFT) and a novel matching strategy called spatial consistency constraints (SCC) to cope with the large difference in spatial resolutions between the image pair. Three constraints on angle, distance, and ratio are introduced to re the initial matching features obtained by I-SIFT. Three groups of experiments were conducted to validate the effectiveness of the proposed method. The experiments used high resolution multispectral and panoramic SPOT 5/6 images and Landsat 5/8 orthorectification images. Experimental results show that the registration error lies in about 1 pixel of high-resolution images and demonstrate that the proposed I-SIFT-SCC approach is suitable for fine registration of optical satellite images from medium spatial resolution to high spatial resolution with resolution ratio up to 6. 相似文献
23.
Fluorescence‐Activated Cell Sorters: Standing Surface Acoustic Wave (SSAW)‐Based Fluorescence‐Activated Cell Sorter (Small 40/2018)
下载免费PDF全文
![点击此处可从《Small (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
24.
25.
Malondialdehyde (MDA) was selected to represent a secondary by-product of lipid peroxidation during rice ageing. This study aimed to investigate the effects of MDA modification on the structural characteristics of rice protein. The results showed that as MDA concentration increased, rice protein carbonyl and disulphide groups increased, but sulphydryl content decreased. The blue shift of maximum fluorescence peak, the decrease of rice protein intrinsic fluorescence intensity and the reduction of surface hydrophobicity indicated the formation of protein aggregates caused by MDA oxidative modification. The results of molecular weight distribution and particle size distribution showed that MDA modification resulted in the formation of soluble protein aggregates, and the decrease of rice protein solubility indicated that insoluble protein aggregates were formed. Results of protein electrophoresis showed that MDA modification contributed to rice protein aggregation via non-disulphide covalent bonds. The results showed that rice protein gradually aggregated with increasing MDA concentration. 相似文献
26.
27.
Yan Jing Zhu Rongying Wu Fan Zhao Ziyin Ye Huan Hou Mengying Liu Yong Yin Lichen 《Nano Research》2020,13(10):2706-2715
Nano Research - Insufficient intratumoral penetration greatly hurdles the anticancer performance of nanomedicine. To realize highly efficient tumor penetration in a precisely and spatiotemporally... 相似文献
28.
29.
Xiaoyan Qiu Yongqiang Zhang Haitao Wu Rui Yang Jun Yang Rongjuan Liu Yong Liu Zhiping Zhou Tongfan Hao Yijing Nie 《Polymer International》2019,68(2):218-224
The crystallization of capped ultrathin polymer films is closely dependent on film thickness and interfacial interaction. Using dynamic Monte Carlo simulations, the crystallization behaviors of polymer films confined between two substrates were investigated. The crystallization rate of confined polymers is reduced with high interfacial interactions. Above a critical strength of interfacial interaction, polymer crystallization in the thin film is inhibited within the simulation time scales. An increase in film thickness leads to a rise in critical interfacial interaction. In thicker films, the chains have more space to change conformation to form crystal stems. In addition, there are fewer absorbed segments in confined chains for the thicker films, and thus the chains have stronger ability to adjust their conformation. Therefore an increase in film thickness can cause a reduction in the entropic barrier required for the formation of crystals and thus an increase in the critical interfacial interaction. © 2018 Society of Chemical Industry 相似文献
30.
Magnetic Resonance Materials in Physics, Biology and Medicine - To investigate the value of using diffusion-weighted imaging (DWI) and intravoxel incoherent motion DWI (IVIM-DWI) to assess the... 相似文献