全文获取类型
收费全文 | 89146篇 |
免费 | 7673篇 |
国内免费 | 3982篇 |
专业分类
电工技术 | 4975篇 |
技术理论 | 5篇 |
综合类 | 5688篇 |
化学工业 | 14875篇 |
金属工艺 | 5408篇 |
机械仪表 | 5664篇 |
建筑科学 | 6956篇 |
矿业工程 | 2852篇 |
能源动力 | 2350篇 |
轻工业 | 5624篇 |
水利工程 | 1485篇 |
石油天然气 | 5344篇 |
武器工业 | 723篇 |
无线电 | 10634篇 |
一般工业技术 | 10923篇 |
冶金工业 | 4166篇 |
原子能技术 | 879篇 |
自动化技术 | 12250篇 |
出版年
2024年 | 471篇 |
2023年 | 1545篇 |
2022年 | 2555篇 |
2021年 | 3652篇 |
2020年 | 2802篇 |
2019年 | 2370篇 |
2018年 | 2655篇 |
2017年 | 2905篇 |
2016年 | 2623篇 |
2015年 | 3407篇 |
2014年 | 4176篇 |
2013年 | 5048篇 |
2012年 | 5603篇 |
2011年 | 6097篇 |
2010年 | 5206篇 |
2009年 | 4949篇 |
2008年 | 4738篇 |
2007年 | 4678篇 |
2006年 | 4998篇 |
2005年 | 4285篇 |
2004年 | 2982篇 |
2003年 | 2556篇 |
2002年 | 2368篇 |
2001年 | 2060篇 |
2000年 | 2253篇 |
1999年 | 2440篇 |
1998年 | 2102篇 |
1997年 | 1740篇 |
1996年 | 1633篇 |
1995年 | 1320篇 |
1994年 | 1144篇 |
1993年 | 815篇 |
1992年 | 630篇 |
1991年 | 494篇 |
1990年 | 347篇 |
1989年 | 297篇 |
1988年 | 253篇 |
1987年 | 162篇 |
1986年 | 130篇 |
1985年 | 74篇 |
1984年 | 46篇 |
1983年 | 31篇 |
1982年 | 38篇 |
1981年 | 23篇 |
1980年 | 28篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1976年 | 14篇 |
1975年 | 9篇 |
1970年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 24 毫秒
901.
902.
903.
904.
Yujiao Mai Jianping Hu Zheng Yan Shuangju Zhen Shujun Wang Wei Zhang 《Computers in human behavior》2012
This study empirically investigated the structure and function of maladaptive cognitions related to Pathological Internet Use (PIU) among Chinese adolescents. To explore the structure of maladaptive cognitions, this study validated a Chinese Adolescents’ Maladaptive Cognitions Scale (CAMCS) with two samples of adolescents (n1 = 293 and n2 = 609). The results of the exploratory factor analysis and confirmatory factor analysis revealed that CAMCS included three distinct factors, namely, “social comfort,” “distraction,” and “self-realization.” To examine the function of maladaptive cognitions, this study tested an updated cognitive-behavioral model in the third sample of 1059 adolescents. The results of structural equation model analyses verified both the direct effect of maladaptive cognitions on PIU and their mediating role in the relationships between distal factors (social anxiety and stressful life events) and PIU among Chinese adolescents. Theoretical and practical implications of these findings were discussed. 相似文献
905.
Hu XiongAuthor Vitae Zhong ChenAuthor VitaeFagen LiAuthor Vitae 《Computers & Electrical Engineering》2012,38(3):573-581
In this paper, we introduce an efficient and multi-level conditional privacy preservation authentication protocol in vehicular ad hoc networks (VANETs) based on ring signature. The proposed protocol has three appealing characteristics: First, it offers conditional privacy preservation authentication: while every receiver can verify that a message issuer is an authorized participant in the system only a trusted authority can reveal the true identity of a message sender. Second, it is equipped with multi-level countermeasure: each vehicle can select the degree of privacy according to its own requirements. Third, it is efficient: our system outperforms previous proposals in message authentication and verification, cost-effective identity tracking in case of a dispute, and low storage requirements. We demonstrate the merits gained by the proposed protocol through extensive analysis. 相似文献
906.
Liao SH Zou BJ Geng JP Wang JX Ding X 《Computer methods and programs in biomedicine》2012,108(2):536-547
Although it is well known that human bone tissues have obvious orthotropic material properties, most works in the physical modeling field adopted oversimplified isotropic or approximated transversely isotropic elasticity due to the simplicity. This paper presents a convenient methodology based on harmonic fields, to construct volumetric finite element mesh integrated with complete orthotropic material. The basic idea is taking advantage of the fact that the longitudinal axis direction indicated by the shape configuration of most bone tissues is compatible with the trajectory of the maximum material stiffness. First, surface harmonic fields of the longitudinal axis direction for individual bone models were generated, whose scalar distribution pattern tends to conform very well to the object shape. The scalar iso-contours were extracted and sampled adaptively to construct volumetric meshes of high quality. Following, the surface harmonic fields were expanded over the whole volumetric domain to create longitudinal and radial volumetric harmonic fields, from which the gradient vector fields were calculated and employed as the orthotropic principal axes vector fields. Contrastive finite element analyses demonstrated that elastic orthotropy has significant effect on simulating stresses and strains, including the value as well as distribution pattern, which underlines the relevance of our orthotropic modeling scheme. 相似文献
907.
Luan S Wang T Li W Liu Z Jiang L Hu L 《Computer methods and programs in biomedicine》2012,108(1):151-157
Milling operations in spinal surgery demand much experience and skill for the surgeon to perform the procedure safely. A 3D navigation method is introduced aiming at providing a monitoring system with enhanced safety and minimal intraoperative interaction. An automatic registration method is presented to establish the 3D-3D transformation between the preoperative CT images and a common reference system in the surgical space, and an intensity-based similarity metric adapted for the multi-planar configuration is introduced in the registration procedure. A critical region is defined for real-time monitoring in order to prevent penetration of the lamina and avoid violation of nerve structures. The contour of the spinal canal is reconstructed as the critical region, and different levels of warning limits are defined. During the milling procedure, the position of the surgical instrument relative to the critical region is provided with augmented display and audio warnings. Timely alarm is provided for surgeons to prevent surgical failure when the mill approaches the critical region. Our validation experiment shows that real-time 3D navigation and monitoring is advantageous for improving the safety of the milling operation. 相似文献
908.
Xiujian Li Wenhua Hu Hualiang Zhang Yongming Nie Jiankun Yang Junbo Yang 《The Journal of supercomputing》2012,62(2):689-697
With excellent photo-electric and electro-optical effects, the photorefractive spatial light modulators can work as optically addressed modulators in optical information processing systems and parallel optical computing systems. The photo-induced current pulses of the photorefractive spatial light modulator observed in the experiments are analyzed to conclude the characteristics, and to find the relationship between the properties of the current pulse and the structural parameters. Furthermore, the origin of the photo-induced current pulse is analyzed, and the methods to improve the operation speed of the spatial light modulators are proposed. The research results will be significant for extending the applications of the photorefractive spatial light modulators, and pushing ahead the research of all-optical modulation materials and devices for optical supercomputing. 相似文献
909.
This paper presents an integration technology for RF passives using benzocyclobutene (BCB)/metal multilayer interconnection
for system-in-package applications. This technology has been specially developed for RF subsystem packages in which a thick
polymer, BCB (more than 15 μm thick), is adopted as dielectric with lossy silicon as substrate for its excellent characteristics.
Both dry-etch BCB and photosensitive BCB are applied in this work, and their processes are briefly introduced and compared.
An RF power divider, an MIM capacitor, different types of RF inductors as well as a coupled microstrip based band-pass filter
are fabricated and measured at wafer level. The results show good electrical performances, and accordingly the passives are
well applicable in RF band. Moreover, the subsystem models including monolithic chips connected with passives are presented. 相似文献
910.