全文获取类型
收费全文 | 7093篇 |
免费 | 324篇 |
国内免费 | 53篇 |
专业分类
电工技术 | 133篇 |
综合类 | 26篇 |
化学工业 | 1786篇 |
金属工艺 | 118篇 |
机械仪表 | 211篇 |
建筑科学 | 277篇 |
矿业工程 | 6篇 |
能源动力 | 462篇 |
轻工业 | 725篇 |
水利工程 | 76篇 |
石油天然气 | 115篇 |
无线电 | 653篇 |
一般工业技术 | 1142篇 |
冶金工业 | 337篇 |
原子能技术 | 83篇 |
自动化技术 | 1320篇 |
出版年
2024年 | 24篇 |
2023年 | 151篇 |
2022年 | 317篇 |
2021年 | 405篇 |
2020年 | 295篇 |
2019年 | 335篇 |
2018年 | 416篇 |
2017年 | 358篇 |
2016年 | 355篇 |
2015年 | 236篇 |
2014年 | 319篇 |
2013年 | 641篇 |
2012年 | 356篇 |
2011年 | 505篇 |
2010年 | 350篇 |
2009年 | 326篇 |
2008年 | 288篇 |
2007年 | 217篇 |
2006年 | 201篇 |
2005年 | 140篇 |
2004年 | 111篇 |
2003年 | 117篇 |
2002年 | 90篇 |
2001年 | 64篇 |
2000年 | 73篇 |
1999年 | 50篇 |
1998年 | 77篇 |
1997年 | 41篇 |
1996年 | 49篇 |
1995年 | 40篇 |
1994年 | 36篇 |
1993年 | 44篇 |
1992年 | 36篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 20篇 |
1988年 | 35篇 |
1987年 | 30篇 |
1986年 | 20篇 |
1985年 | 15篇 |
1984年 | 27篇 |
1983年 | 22篇 |
1982年 | 22篇 |
1981年 | 16篇 |
1980年 | 20篇 |
1979年 | 16篇 |
1978年 | 17篇 |
1976年 | 18篇 |
1975年 | 19篇 |
1974年 | 12篇 |
排序方式: 共有7470条查询结果,搜索用时 0 毫秒
81.
Deneuville F Duquennoy M Ouaftouh M Jenot F Ourak M Desvaux S 《The Review of scientific instruments》2008,79(4):044901
An original inversion method specifically adapted to the estimation of Poisson coefficient of balls by using their resonance spectra is described. From the study of their elastic vibrations, it is possible to accurately characterize the balls. The proposed methodology can create both spheroidal modes in the balls and detect such vibrations over a large frequency range. Experimentally, by using both an ultrasonic probe for the emission (piezoelectric transducer) and a heterodyne optic probe for the reception (interferometer), it was possible to take spectroscopic measurements of spheroidal vibrations over a large frequency range (100 kHz-45 MHz) in a continuous regime. This method, which uses ratios between wave resonance frequencies, allows the Poisson coefficient to be determined independently of Young's modulus and the ball's radius and density. This has the advantage of providing highly accurate estimations of Poisson coefficient (+/-4.3 x 10(-4)) over a wide frequency range. 相似文献
82.
Houssein Essam H. Hosney Mosa E. Mohamed Waleed M. Ali Abdelmgeid A. Younis Eman M. G. 《Neural computing & applications》2023,35(7):5251-5275
Neural Computing and Applications - Feature selection (FS) is one of the basic data preprocessing steps in data mining and machine learning. It is used to reduce feature size and increase model... 相似文献
83.
The conventional hospital environment is transformed into digital transformation that focuses on patient centric remote approach through advanced technologies. Early diagnosis of many diseases will improve the patient life. The cost of health care systems is reduced due to the use of advanced technologies such as Internet of Things (IoT), Wireless Sensor Networks (WSN), Embedded systems, Deep learning approaches and Optimization and aggregation methods. The data generated through these technologies will demand the bandwidth, data rate, latency of the network. In this proposed work, efficient discrete grey wolf optimization (DGWO) based data aggregation scheme using Elliptic curve Elgamal with Message Authentication code (ECEMAC) has been used to aggregate the parameters generated from the wearable sensor devices of the patient. The nodes that are far away from edge node will forward the data to its neighbor cluster head using DGWO. Aggregation scheme will reduce the number of transmissions over the network. The aggregated data are preprocessed at edge node to remove the noise for better diagnosis. Edge node will reduce the overhead of cloud server. The aggregated data are forward to cloud server for central storage and diagnosis. This proposed smart diagnosis will reduce the transmission cost through aggregation scheme which will reduce the energy of the system. Energy cost for proposed system for 300 nodes is 0.34μJ. Various energy cost of existing approaches such as secure privacy preserving data aggregation scheme (SPPDA), concealed data aggregation scheme for multiple application (CDAMA) and secure aggregation scheme (ASAS) are 1.3 μJ, 0.81 μJ and 0.51 μJ respectively. The optimization approaches and encryption method will ensure the data privacy. 相似文献
84.
85.
Wireless Personal Communications - Software-defined networking (SDN) is widely perceived to simplify network management and monitoring. The introduction of the SDN model into wireless sensor... 相似文献
86.
Numerical simulation has been performed to improve the performance of Cu2ZnSnS4 (CZTS) solar cells by replacing CdS with Zn1–xSnxO buffer layer. The influences of thickness, donor concentration and defect density of buffer layers on the performance of CZTS solar cells were investigated. It has been found that Zn1–xSnxO buffer layer for Sn content of 0.20 is better for CZTS solar cell. A higher efficiency can be achieved with thinner buffer layer. The optimized solar cell demonstrated a maximum power conversion efficiency of 13%. 相似文献
87.
Identity management is based on the creation and management of user identities for granting access to the cloud resources based on the user attributes. The cloud identity and access management (IAM) grants the authorization to the end-users to perform different actions on the specified cloud resources. The authorizations in the IAM are grouped into roles instead of granting them directly to the end-users. Due to the multiplicity of cloud locations where data resides and due to the lack of a centralized user authority for granting or denying cloud user requests, there must be several security strategies and models to overcome these issues. Another major concern in IAM services is the excessive or the lack of access level to different users with previously granted authorizations. This paper proposes a comprehensive review of security services and threats. Based on the presented services and threats, advanced frameworks for IAM that provide authentication mechanisms in public and private cloud platforms. A threat model has been applied to validate the proposed authentication frameworks with different security threats. The proposed models proved high efficiency in protecting cloud platforms from insider attacks, single sign-on failure, brute force attacks, denial of service, user privacy threats, and data privacy threats. 相似文献
88.
Mohamed Mohamady Ghobashy Mervat Rabie Khafaga 《Journal of Superconductivity and Novel Magnetism》2017,30(2):401-406
In this work, acrylic acid (AAc) monomer was grafted onto low-density polyethylene (LDPE) films by the direct method to obtain acid (LDPE-grafted poly(acrylic acid) (LDPE-g-PAAc)) graft copolymers. The presence of the grafted PAAc with COOH groups allows coupling with Fe2+/3+ ions. The stabilization of Fe3O4 particles onto the graft copolymers was done by in situ reduction of LDPE-g-PAAc/Fe2+/3+ with sodium borohydride (NaBH4) in aqueous solution. The LDPE-g-PAAc graft copolymer and LDPE-g-PAAc/Fe3O4 composite films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and electron spin resonance (ESR). The synthesized composites exhibit excellent magnetic properties. The results indicated that the magnetic oxide (Fe3O4) was embedded and homogenously dispersed into the surfaces of the graft copolymer films as indicated by SEM. The FT-IR analysis clearly suggests that an AAc monomer was effectively grafted onto LDPE. The XRD studies elucidate the change in the crystallinity of the graft copolymers. 相似文献
89.
This article proposes to solve the problem of minimizing the total completion time in a two-machine permutation flowshop environment in which time delays between the machines are considered. For this purpose, an enumeration algorithm based on the branch-and-bound framework is developed, which includes new lower and upper bounds as well as dominance rules. The computational study shows that problems with up to 40 jobs can be solved in a reasonable amount of time. 相似文献
90.
Jun Pan Li Na Quan Yongbiao Zhao Wei Peng Banavoth Murali Smritakshi P. Sarmah Mingjian Yuan Lutfan Sinatra Noktan M. Alyami Jiakai Liu Emre Yassitepe Zhenyu Yang Oleksandr Voznyy Riccardo Comin Mohamed N. Hedhili Omar F. Mohammed Zheng Hong Lu Dong Ha Kim Edward H. Sargent Osman M. Bakr 《Advanced materials (Deerfield Beach, Fla.)》2016,28(39):8718-8725