全文获取类型
收费全文 | 41548篇 |
免费 | 2443篇 |
国内免费 | 925篇 |
专业分类
电工技术 | 1425篇 |
技术理论 | 5篇 |
综合类 | 1358篇 |
化学工业 | 7157篇 |
金属工艺 | 1979篇 |
机械仪表 | 1869篇 |
建筑科学 | 2428篇 |
矿业工程 | 707篇 |
能源动力 | 1180篇 |
轻工业 | 3455篇 |
水利工程 | 502篇 |
石油天然气 | 1694篇 |
武器工业 | 150篇 |
无线电 | 4685篇 |
一般工业技术 | 5711篇 |
冶金工业 | 4888篇 |
原子能技术 | 438篇 |
自动化技术 | 5285篇 |
出版年
2024年 | 139篇 |
2023年 | 595篇 |
2022年 | 974篇 |
2021年 | 1427篇 |
2020年 | 1121篇 |
2019年 | 1010篇 |
2018年 | 1195篇 |
2017年 | 1171篇 |
2016年 | 1172篇 |
2015年 | 1253篇 |
2014年 | 1597篇 |
2013年 | 2450篇 |
2012年 | 2178篇 |
2011年 | 2401篇 |
2010年 | 2032篇 |
2009年 | 1953篇 |
2008年 | 1957篇 |
2007年 | 1882篇 |
2006年 | 1824篇 |
2005年 | 1641篇 |
2004年 | 1098篇 |
2003年 | 1028篇 |
2002年 | 941篇 |
2001年 | 839篇 |
2000年 | 869篇 |
1999年 | 1029篇 |
1998年 | 1751篇 |
1997年 | 1126篇 |
1996年 | 940篇 |
1995年 | 751篇 |
1994年 | 599篇 |
1993年 | 550篇 |
1992年 | 348篇 |
1991年 | 285篇 |
1990年 | 254篇 |
1989年 | 228篇 |
1988年 | 224篇 |
1987年 | 167篇 |
1986年 | 165篇 |
1985年 | 206篇 |
1984年 | 161篇 |
1983年 | 126篇 |
1982年 | 96篇 |
1981年 | 116篇 |
1980年 | 115篇 |
1979年 | 110篇 |
1977年 | 123篇 |
1976年 | 167篇 |
1975年 | 63篇 |
1973年 | 67篇 |
排序方式: 共有10000条查询结果,搜索用时 69 毫秒
101.
Van Thanh Dau Thien Xuan Dinh Tanaka Katsuhiko Sugiyama Susumu 《Microsystem Technologies》2009,15(7):1039-1044
A gas-jet micro pump with novel cross-junction channel has been designed and fabricated using a Si micromachining process.
The valveless micro pump is composed of a piezoelectric lead zirconate titanate (PZT) diaphragm actuator and fluidic network.
The design of the valveless pump focuses on a cross-junction formed by the neck of the pump chamber and one outlet and two
opposite inlet channels. The structure of cross-junction allows differences in fluidic resistance and fluidic momentum inside
the channels during each PZT diaphragm vibration cycle, which leads to the gas flow being rectified without valves. The flow
channels were easily fabricated by using silicon etching process. To investigate the effects of the structure of the cross-junction
on the gas flow rate, two types of pump with different cross-junction were studied. The design and simulation were done using
ANSYS-Fluent software. The simulations and experimental data revealed that the step-nozzle structure is much more advantageous
than the planar structure. A flow rate of 5.2 ml/min was obtained for the pump with step structure when the pump was driven
at its resonant frequency of 7.9 kHz by a sinusoidal voltage of 50 Vp–p. 相似文献
102.
103.
Hu Changhui Lu Xiaobo Ye Mengjun Zeng Weili Du Yijun 《Multimedia Tools and Applications》2017,76(24):26523-26550
Multimedia Tools and Applications - The extended sparse representation classifier (ESRC) is one of the state-of-the-art solutions for single sample face recognition, but it performs... 相似文献
104.
We present a refined entanglement concentration protocol (ECP) for an arbitrary unknown less-entangled four-electron-spin cluster state by exploring the optical selection rules derived from the quantum-dot spins in one-sided optical microcavities. In our ECP, the parties obtain not only the four-electron-spin systems in the partial entanglement with two unknown parameters, but also the less-entangled two-electron-spin systems in the first step. Utilizing the above preserved systems as the resource for the second step of our ECP, the parties can obtain a standard cluster state by keeping the robust odd-parity instances with two parity-check gates. Meanwhile, the systems in the rest three instances can be used as the resource in the next round of our ECP. The success probability of our ECP is largely increased by iteration of the ECP process. Moreover, all the coefficients of our ECP are unknown for the parties without assistance of extra single electron-spin, so our ECP maybe has good applications in quantum communication network in the future. 相似文献
105.
Mei Kum Khaw Chin Hong Ooi Faisal Mohd-Yasin Anh V. Nguyen Geoffrey M. Evans Nam-Trung Nguyen 《Microfluidics and nanofluidics》2017,21(6):110
This paper reports the dynamic behaviour of a magnetically actuated floating liquid marble by analysing the oscillation of the marble. A liquid marble is a liquid droplet coated with hydrophobic powder. Magnetite particles inside the marble make it magnetic. The marble floats on a carrier liquid that contains aqueous glycerol of various concentrations. A permanent magnet located under the carrier liquid drives the floating marble with the initial velocity. Stopping the magnet abruptly causes the marble to oscillate around its final position for a few seconds. The oscillation was recorded and analysed using customised image processing and evaluation software. The damped harmonic motion model was then applied to the data and tested. Subsequently, critical parameters of the system such as the initial displacement, friction correction factor, the apparent frequency and the spring constant were determined and discussed. The simple experimental set-up and convenient theoretical approach allow us to characterise the marble motion under the influence of a magnet with good accuracy. 相似文献
106.
This paper deals with the stability radii of implicit dynamic equations on time scales when the structured perturbations act on both the coefficient of derivative and the right-hand side. Formulas of the stability radii are derived as a unification and generalization of some previous results. A special case where the real stability radius and the complex stability radius are equal is studied. Examples are derived to illustrate results. 相似文献
107.
Tich Phuoc Tran Thi Thanh Sang Nguyen Poshiang Tsai Xiaoying Kong 《Artificial Intelligence Review》2011,35(4):369-382
In the modern age of Internet connectivity, advanced information systems have accumulated huge volumes of data. Such fast
growing, tremendous amount of data, collected and stored in large databases has far exceeded our human ability to comprehend
without proper tools. There has been a great deal of research conducted to explore the potential applications of Machine Learning
technologies in Security Informatics. This article studies the Network Security Detection problems in which predictive models
are constructed to detect network security breaches such as spamming. Due to overwhelming volume of data, complexity and dynamics
of computer networks and evolving cyber threats, current security systems suffer limited performance with low detection accuracy
and high number of false alarms. To address such performance issues, a novel Machine Learning algorithm, namely Boosted Subspace
Probabilistic Neural Network (BSPNN), has been proposed which combines a Radial Basis Function Neural Network with an innovative
diversity-based ensemble learning framework. Extensive empirical analyses suggested that BSPNN achieved high detection accuracy
with relatively small computational complexity compared with other conventional detection methods. 相似文献
108.
Three-dimensional quantitative structure-activity relationship (3D-QSAR) models were developed using comparative molecular field analysis (CoMFA) and comparative molecular similarity analysis (CoMSIA) on a series of agonists of thyroid hormone receptor beta (TRbeta), which may lead to safe therapies for non-thyroid disorders while avoiding the cardiac side effects. The reasonable q(2) (cross-validated) values 0.600 and 0.616 and non-cross-validated r(2) values of 0.974 and 0.974 were obtained for CoMFA and CoMSIA models for the training set compounds, respectively. The predictive ability of two models was validated using a test set of 12 molecules which gave predictive correlation coefficients (r(pred)(2)) of 0.688 and 0.674, respectively. The Lamarckian Genetic Algorithm (LGA) of AutoDock 4.0 was employed to explore the binding mode of the compound at the active site of TRbeta. The results not only lead to a better understanding of interactions between these agonists and the thyroid hormone receptor beta but also can provide us some useful information about the influence of structures on the activity which will be very useful for designing some new agonist with desired activity. 相似文献
109.
Flerackers C. Earnshaw R. Vansichem G. Van Reeth F. Alsema F. 《Computer Graphics and Applications, IEEE》2001,21(1):56-60
By exploiting a networked virtual environment architecture, we produced the gaming part of an interactive television drama series, TypoToons. For decades TV show makers have been inventing tools and tricks to enhance the stories they tell. Equivalents of, and additions to these conventional tricks in interactive media can only mature an interactive television if multidisciplinary teams can obtain hands on experience of these newly emerging worlds. The production team for TypoToons and the interactively participating audience provided an excellent opportunity to develop such a team 相似文献
110.