全文获取类型
收费全文 | 53545篇 |
免费 | 5714篇 |
国内免费 | 3259篇 |
专业分类
电工技术 | 4308篇 |
技术理论 | 1篇 |
综合类 | 4428篇 |
化学工业 | 8098篇 |
金属工艺 | 3351篇 |
机械仪表 | 3413篇 |
建筑科学 | 4150篇 |
矿业工程 | 1957篇 |
能源动力 | 1461篇 |
轻工业 | 4933篇 |
水利工程 | 1303篇 |
石油天然气 | 2462篇 |
武器工业 | 621篇 |
无线电 | 6132篇 |
一般工业技术 | 5780篇 |
冶金工业 | 2375篇 |
原子能技术 | 747篇 |
自动化技术 | 6998篇 |
出版年
2024年 | 319篇 |
2023年 | 1013篇 |
2022年 | 2150篇 |
2021年 | 2628篇 |
2020年 | 1948篇 |
2019年 | 1505篇 |
2018年 | 1681篇 |
2017年 | 1914篇 |
2016年 | 1603篇 |
2015年 | 2433篇 |
2014年 | 2962篇 |
2013年 | 3295篇 |
2012年 | 3762篇 |
2011年 | 3958篇 |
2010年 | 3652篇 |
2009年 | 3516篇 |
2008年 | 3651篇 |
2007年 | 3262篇 |
2006年 | 3216篇 |
2005年 | 2479篇 |
2004年 | 1713篇 |
2003年 | 1443篇 |
2002年 | 1342篇 |
2001年 | 1206篇 |
2000年 | 1121篇 |
1999年 | 923篇 |
1998年 | 687篇 |
1997年 | 577篇 |
1996年 | 498篇 |
1995年 | 449篇 |
1994年 | 333篇 |
1993年 | 255篇 |
1992年 | 237篇 |
1991年 | 156篇 |
1990年 | 135篇 |
1989年 | 126篇 |
1988年 | 88篇 |
1987年 | 57篇 |
1986年 | 37篇 |
1985年 | 37篇 |
1984年 | 19篇 |
1983年 | 26篇 |
1982年 | 27篇 |
1981年 | 10篇 |
1980年 | 15篇 |
1979年 | 13篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1959年 | 7篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Zhang Man Zhou Yong Liu Bing Zhao Jiaqi Yao Rui Shao Zhiwen Zhu Hancheng Chen Hao 《Pattern Analysis & Applications》2023,26(2):669-677
Pattern Analysis and Applications - The designed method aims to perform image classification tasks efficiently and accurately. Different from the traditional CNN-based image classification methods,... 相似文献
52.
Yan-kun Tang Qian Yang Xiao-fei Si Jin-kang Han Wei-wei Cao Ya-fei Li Fang Liu Xiaoyan Yao Ya Zhai 《Journal of Superconductivity and Novel Magnetism》2017,30(6):1527-1531
In this study, we report the results of an investigation into the sintering temperature dependence of magnetic and transport properties for GdBaCo2 O 5 + δ synthesized through a sol-gel method. The lowering of sintering temperature leads to the increase of oxygen content and the reduction of grain size. The increase of oxygen content results in the enhancement of magnetic interactions and the weakening of Coulomb repulsion effect, while the reduction of grain size improves the magnetoresistance effect. Metal-insulator transition accompanied with spin-state transition is observed in all samples. 相似文献
53.
54.
Xiazhang Li Wei Zhu Yu Yin Xiaowang Lu Chao Yao Chaoying Ni 《Journal of Materials Science: Materials in Electronics》2016,27(5):4180-4185
La1?xAgxFeO3/halloysites nanotubes (HNTs) nanocomposite was synthesized by sol–gel method. It was characterized by X-ray diffraction, transmission electron microscope, Fourier transform infrared spectroscopy and UV–visible diffused reflectance spectroscopy measurements. The photo-activity of the La1?xAgxFeO3/HNTs nanocomposite was evaluated via degradation of methylene blue (MB) under visible-light irradiation. The results showed that the HNTs with unique pore structure favored the adsorption of organic molecules. Adequate Ag+ doping improved the absorption ability for visible light. The La0.95Ag0.05FeO3/HNTs demonstrated the best photocatalytic performance, which achieved as high as 99 % for MB degradation exposed 2 h irradiation. However,further increasing of Ag+ doping gradually reduced the photocatalytic activity. The nanocomposite catalyst showed outstanding recyclability after eight cycles which still remained up to 90 %. 相似文献
55.
56.
Yao Chen Wangjie Ye Pan Shi Ruoqi He Jinbing Liang Jian Feng Pooya Sareh 《Advanced Engineering Materials》2023,25(16):2201762
Origami-based metamaterials have widespread application prospects in various industries including aerospace, automotive, flexible electronics, and civil engineering structures. Among the wide range of origami patterns, the fourfold tessellation known as Miura-ori is of particular attraction to engineers and designers. More specifically, researchers have proposed different 3D structures and metamaterials based on the geometric characteristics of this classic origami pattern. Herein, a computational modeling approach for the design and evaluation of 3D cellular solids with the Miura-ori metamaterial geometry which can be of zero or nonzero thicknesses is presented. To this end, first, a range of design alternatives generated based on a numerical parametric model is designed. Next, their mechanical properties and failure behavior under quasistatic axial compressive loads along three perpendicular directions are analyzed. Then, the effects of various geometric parameters on their energy absorption behavior under compression in the most appropriate direction are investigated. The findings of this study provide a basis for future experimental investigations and the potential application of such cellular solids for energy-absorbing purposes. 相似文献
57.
X Jiang M Zhang Y Ding J Yao H Chen D Zhu M Muramatu 《Canadian Metallurgical Quarterly》1998,124(5):980-985
BACKGROUND AND PURPOSE: Mood disorders are common after stroke and may impede physical, functional, and cognitive recovery, making early identification and treatment of potential importance. We aimed to compare the accuracy of the General Health Questionnaire (GHQ-30) and the Hospital Anxiety and Depression (HAD) Scale in detecting psychiatric morbidity after stroke and to determine the most suitable cutoff points for different purposes. METHODS: One hundred five hospital-referred stroke patients completed both the GHQ-30 and HAD Scale 6 months after onset before a blinded psychiatric assessment in which the Schedule for Affective Disorders and Schizophrenia with some supplementary questions was used to determine a DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition) diagnosis. Measures were compared in terms of sensitivity, specificity, and receiver operating characteristic curves. RESULTS: No significant differences were found between the GHQ-30 and the HAD Scale in identifying those patients with any DSM-IV diagnosis (P=0.95), grouped depression (P=0.56), or anxiety (P=0.25) disorders. The previously recommended cutoff points for identifying "cases" for the GHQ (4/5) and for the HAD Scale (8/9 and 11/12) were found to be suboptimal in this population. CONCLUSIONS: The GHQ-30 and HAD scale exhibited similar levels of sensitivity and specificity. Data are presented, taking into account the "cost" of false-positives and negatives, to allow a choice of cutoff points suitable for differing situations. 相似文献
58.
Jian-You Guo Miao Yu Jing Wang Bao-Mei Yao Peng Jiao 《Computer Physics Communications》2010,181(3):550-556
We develop the complex scaling method within the relativistic framework by expanding the Dirac spinors in the complete set of eigensolutions of a harmonic oscillator potential, and present the theoretical formalism of describing the discrete bound and resonant states on the same footing. Based on a well established and frequently used model, we demonstrate the utility and applicability of the extended method and examine the stability of the results with respect to the variations of the parameters of the model. Satisfactory agreements are found for all the calculated results in comparison with some other calculations in references. Especially, the present calculation in the nonrelativistic limit gives a consistent result with that in the nonrelativistic calculation. 相似文献
59.
针对燃气行业人工抄表费时费力等问题,提出一种基于GPRS和无线多跳网络技术的燃气无线抄表系统,在分析传统抄表系统的结构以及传输方式优缺点的基础上介绍了系统的总体结构、工作原理以及各部分组成和功能。采用计算机网络和数据库等技术,使得该系统具有功能强大、使用方便、可扩展性好等特点,可实现对整个燃气输配系统的监控,有效提高燃气公司的管理水平和服务效率。 相似文献
60.