全文获取类型
收费全文 | 9036篇 |
免费 | 569篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 125篇 |
综合类 | 18篇 |
化学工业 | 2339篇 |
金属工艺 | 170篇 |
机械仪表 | 207篇 |
建筑科学 | 321篇 |
矿业工程 | 36篇 |
能源动力 | 223篇 |
轻工业 | 402篇 |
水利工程 | 68篇 |
石油天然气 | 28篇 |
无线电 | 759篇 |
一般工业技术 | 2287篇 |
冶金工业 | 981篇 |
原子能技术 | 78篇 |
自动化技术 | 1584篇 |
出版年
2023年 | 153篇 |
2022年 | 374篇 |
2021年 | 419篇 |
2020年 | 285篇 |
2019年 | 246篇 |
2018年 | 301篇 |
2017年 | 255篇 |
2016年 | 349篇 |
2015年 | 297篇 |
2014年 | 438篇 |
2013年 | 550篇 |
2012年 | 547篇 |
2011年 | 623篇 |
2010年 | 423篇 |
2009年 | 412篇 |
2008年 | 433篇 |
2007年 | 417篇 |
2006年 | 324篇 |
2005年 | 253篇 |
2004年 | 222篇 |
2003年 | 201篇 |
2002年 | 191篇 |
2001年 | 122篇 |
2000年 | 113篇 |
1999年 | 119篇 |
1998年 | 193篇 |
1997年 | 154篇 |
1996年 | 105篇 |
1995年 | 83篇 |
1994年 | 73篇 |
1993年 | 90篇 |
1992年 | 53篇 |
1991年 | 50篇 |
1990年 | 50篇 |
1989年 | 37篇 |
1988年 | 44篇 |
1987年 | 40篇 |
1986年 | 34篇 |
1985年 | 42篇 |
1984年 | 37篇 |
1983年 | 32篇 |
1982年 | 27篇 |
1981年 | 27篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 28篇 |
1977年 | 24篇 |
1976年 | 60篇 |
1975年 | 27篇 |
1971年 | 17篇 |
排序方式: 共有9626条查询结果,搜索用时 15 毫秒
11.
12.
Joo H. Kang Eujin Um Alexander Diaz Harry Driscoll Melissa J. Rodas Karel Domansky Alexander L. Watters Michael Super Howard A. Stone Donald E. Ingber 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(42):5657-5666
Magnetic nanoparticles have been employed to capture pathogens for many biological applications; however, optimal particle sizes have been determined empirically in specific capturing protocols. Here, a theoretical model that simulates capture of bacteria is described and used to calculate bacterial collision frequencies and magnetophoretic properties for a range of particle sizes. The model predicts that particles with a diameter of 460 nm should produce optimal separation of bacteria in buffer flowing at 1 L h−1. Validating the predictive power of the model, Staphylococcus aureus is separated from buffer and blood flowing through magnetic capture devices using six different sizes of magnetic particles. Experimental magnetic separation in buffer conditions confirms that particles with a diameter closest to the predicted optimal particle size provide the most effective capture. Modeling the capturing process in plasma and blood by introducing empirical constants (ce), which integrate the interfering effects of biological components on the binding kinetics of magnetic beads to bacteria, smaller beads with 50 nm diameters are predicted that exhibit maximum magnetic separation of bacteria from blood and experimentally validated this trend. The predictive power of the model suggests its utility for the future design of magnetic separation for diagnostic and therapeutic applications. 相似文献
13.
Differences between oculomotor and perceptual artifacts for temporally limited head mounted displays
Alexander Goettker Kevin J. MacKenzie T. Scott Murdison 《Journal of the Society for Information Display》2020,28(6):509-519
We used perceptual and oculomotor measures to understand the negative impacts of low (phantom array) and high (motion blur) duty cycles with a high‐speed, AR‐likehead‐mounted display prototype. We observed large intersubject variability for the detection of phantom array artifacts but a highly consistent and systematic effect on saccadic eye movement targeting during low duty cycle presentations. This adverse effect on saccade endpoints was also related to an increased error rate in a perceptual discrimination task, showing a direct effect of display duty cycle on the perceptual quality. For high duty cycles, the probability of detecting motion blur increased during head movements, and this effect was elevated at lower refresh rates. We did not find an impact of the temporal display characteristics on compensatory eye movements during head motion (e.g., VOR). Together, our results allow us to quantify the tradeoff of different negative spatiotemporal impacts of user movements and make subsequent recommendations for optimized temporal HMD parameters. 相似文献
14.
Five studies examined whether spontaneous trait inferences uniquely reference the person who performed a trait-implying behavior. On each study trial in 5 studies, participants saw 2 faces and a behavioral sentence referring to one of them. Later, participants saw face-trait pairs and indicated whether they had seen the trait word in the sentence presented with the face. Participants falsely recognized implied traits more when these traits were paired with actors' faces than with control faces. This effect was replicated for a large set effaces (120), after a week delay between study and recognition test, when equal attention was paid to each face, and when the orientation of the face at recognition was different from the orientation at encoding. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
15.
A note on the Gauss-Jacobi quadrature formulae for singular integral equations of the second kind 总被引:1,自引:0,他引:1
A fast and efficient numerical method based on the Gauss-Jacobi quadrature is described that is suitable for solving Fredholm
singular integral equations of the second kind that are frequently encountered in fracture and contact mechanics. Here we
concentrate on the case when the unknown function is singular at both ends of the interval. Quadrature formulae involve fixed
nodal points and provide exact results for polynomials of degree 2n − 1, where n is the number of nodes. Finally, an application of the method to a plane problem involving complete contact is presented. 相似文献
16.
Vladimir Rozenshtein Alexander Berg Haim Levanon Uwe Krueger Dietmar Stehlik Yuri Kandrashkin Art Van Der Est 《Israel journal of chemistry》2003,43(3-4):373-381
Light-induced spin-polarized transient EPR spectra are reported for several water-soluble copper porphyrins. The spectra are assigned to the doublet ground state, with emissive spin polarization resulting from photoexcitation and subsequent electronic relaxation. In contrast to other systems for which polarization of a doublet ground state has been observed, the exchange interactions in the copper porphyrins are strong and the geometry is fixed. It is proposed that intersystem crossing from the photoexcited trip-doublet to the trip-quartet state can lead to net polarization of the spin system and that this polarization is maintained during electronic decay, possibly via charge-transfer and exciplex states. The intensity of the observed spin polarization is essentially independent of the molecular orientation in the external field, but is strongly dependent on the nature of the charged peripheral groups. Possible reasons for this behavior are discussed. 相似文献
17.
Peter V. Sushko Alexander L. ShlugerKatsuro Hayashi Masahiro HiranoHideo Hosono 《Thin solid films》2003,445(2):161-167
Recently it has been discovered that a nano-porous main group oxide 12CaO·7Al2O3 (C12A7) can be converted from a wide-gap insulator to a good transparent conductor. Using ab initio modelling we explain good conductivity of this material by very small barriers for hopping of localised electrons between neighbouring positive cages. We show that optical absorption of C12A7 in infrared region and at energies higher than 2.7 eV is due to inter-cage and intra-cage electron transitions, respectively. The proposed mechanisms can be useful in further search for conducting transparent media. 相似文献
18.
Decreasing carboxyl retention in deposits from the glow region of an acrylic acid plasma was measured by X-ray photoelectron spectroscopy and chemical derivatisation as the collection distance from the monomer vapour inlet was increased. Volatilisation of plasma polymerised acrylic acid was detected after trifluoroethanol derivatisation; this is correlated with evaporation of low molecular weight components observed previously. 相似文献
19.
The aim of this paper is to give a general quantitative requirement which the loop gain must satisfy in order to stabilize a given unstable (possibly nonlinear and time-varying) plant, namely that the gain must exceed one. 相似文献
20.