全文获取类型
收费全文 | 6901篇 |
免费 | 409篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 61篇 |
综合类 | 4篇 |
化学工业 | 1535篇 |
金属工艺 | 114篇 |
机械仪表 | 166篇 |
建筑科学 | 206篇 |
矿业工程 | 15篇 |
能源动力 | 233篇 |
轻工业 | 1068篇 |
水利工程 | 59篇 |
石油天然气 | 25篇 |
无线电 | 393篇 |
一般工业技术 | 1178篇 |
冶金工业 | 941篇 |
原子能技术 | 38篇 |
自动化技术 | 1287篇 |
出版年
2024年 | 10篇 |
2023年 | 80篇 |
2022年 | 182篇 |
2021年 | 244篇 |
2020年 | 185篇 |
2019年 | 177篇 |
2018年 | 243篇 |
2017年 | 251篇 |
2016年 | 279篇 |
2015年 | 210篇 |
2014年 | 296篇 |
2013年 | 519篇 |
2012年 | 441篇 |
2011年 | 499篇 |
2010年 | 356篇 |
2009年 | 343篇 |
2008年 | 330篇 |
2007年 | 309篇 |
2006年 | 205篇 |
2005年 | 192篇 |
2004年 | 152篇 |
2003年 | 127篇 |
2002年 | 130篇 |
2001年 | 91篇 |
2000年 | 76篇 |
1999年 | 75篇 |
1998年 | 334篇 |
1997年 | 202篇 |
1996年 | 163篇 |
1995年 | 106篇 |
1994年 | 71篇 |
1993年 | 65篇 |
1992年 | 35篇 |
1991年 | 45篇 |
1990年 | 31篇 |
1989年 | 21篇 |
1988年 | 25篇 |
1987年 | 18篇 |
1986年 | 19篇 |
1985年 | 21篇 |
1984年 | 19篇 |
1983年 | 21篇 |
1982年 | 20篇 |
1981年 | 12篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1977年 | 15篇 |
1976年 | 26篇 |
1975年 | 8篇 |
1973年 | 8篇 |
排序方式: 共有7323条查询结果,搜索用时 15 毫秒
31.
32.
Cesare Faldini Marco Manzetti Simona Neri Francesca Barile Giovanni Viroli Giuseppe Geraci Francesco Ursini Alberto Ruffilli 《International journal of molecular sciences》2022,23(11)
Adolescent idiopathic scoliosis (AIS) is a progressive deformity of the spine. Scoliotic curves progress until skeletal maturity leading, in rare cases, to a severe deformity. While the Cobb angle is a straightforward tool in initial curve magnitude measurement, assessing the risk of curve progression at the time of diagnosis may be more challenging. Epigenetic and genetic markers are potential prognostic tools to predict curve progression. The aim of this study is to review the available literature regarding the epigenetic and genetic factors associated with the risk of AIS curve progression. This review was carried out in accordance with Preferential Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. The search was carried out in January 2022. Only peer-reviewed articles were considered for inclusion. Forty studies were included; fifteen genes were reported as having SNPs with significant association with progressive AIS, but none showed sufficient power to sustain clinical applications. In contrast, nine studies reporting epigenetic modifications showed promising results in terms of reliable markers. Prognostic testing for AIS has the potential to significantly modify disease management. Most recent evidence suggests epigenetics as a more promising field for the identification of factors associated with AIS progression, offering a rationale for further investigation in this field. 相似文献
33.
Elisa Di Fabio Antonia Iazzetti Alessio Incocciati Valentina Caseli Giancarlo Fabrizi Alberto Boffi Alessandra Bonamore Alberto Macone 《International journal of molecular sciences》2022,23(12)
Amine oxidases are enzymes belonging to the class of oxidoreductases that are widespread, from bacteria to humans. The amine oxidase from Lathyrus cicera has recently appeared in the landscape of biocatalysis, showing good potential in the green synthesis of aldehydes. This enzyme catalyzes the oxidative deamination of a wide range of primary amines into the corresponding aldehydes but its use as a biocatalyst is challenging due to the possible inactivation that might occur at high product concentrations. Here, we show that the enzyme’s performance can be greatly improved by immobilization on solid supports. The best results are achieved using amino-functionalized magnetic microparticles: the immobilized enzyme retains its activity, greatly improves its thermostability (4 h at 75 °C), and can be recycled up to 8 times with a set of aromatic ethylamines. After the last reaction cycle, the overall conversion is about 90% for all tested substrates, with an aldehyde production ranging between 100 and 270 mg depending on the substrate used. As a proof concept, one of the aldehydes thus produced was successfully used for the biomimetic synthesis of a non-natural benzylisoquinoline alkaloid. 相似文献
34.
35.
Marcos J. López Fernández Jorge Guzón Fernández Sergio Ríos Aguilar Blanca Salazar Selvi Rubén González Crespo 《Expert systems with applications》2013,40(11):4478-4489
This paper presents an improved attendance control system, required for continuous evaluation which has become compulsory following the Bologna Process. It provides a solution based on NFC technology and is based on a real project developed and pilot tested at the “Universidad Pontificia de Salamanca, Campus Madrid”. 相似文献
36.
37.
Isabella Panfoli Daniela Calzia Silvia Ravera Paolo Bianchini Alberto Diaspro 《Microscopy research and technique》2010,73(12):1086-1090
We describe a procedure for the labeling of membranous vesicular purified subcellular fractions, to image them, typically by confocal laser scanning microscopy. Being intracellular organelles, these fractions, once purified cannot be attached to glass slides as for cells. Fractions are labeled “in batch” without prior embedding or freezing. Each labeling step performed by passages of resuspension/centrifugation is followed by washings. Then samples are dispersed on the glass slides. Mammalian retinal rod outer segment disks, intact brain stem myelin vesicles, and brain synaptosomes were chosen, as these subcellular fractions can be purified by well established procedures. These fractions were immunolabeled with specific antibodies. Moreover, by the earlier procedure, we show that the mitochondrial vital membrane potential probe MitoTracker Deep Red 633 stains myelin vesicles and rod disks before fixation, consistently with our previous reports of a respiring capacity of these membranes. Therefore, the technique seems adequate to become an instrument to study the structure and the function of these and other subcellular fractions. Microsc. Res. Tech. 73:1086–1090, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
38.
J. Fernández‐Berni R. Carmona‐Galán 《International Journal of Circuit Theory and Applications》2012,40(8):859-876
This paper addresses the design and VLSI implementation of MOS‐based RC networks capable of performing time‐controlled Gaussian filtering. In these networks, all the resistors are substituted one by one by a single MOS transistor biased in the ohmic region. The design of this elementary transistor is carefully realized according to the value of the ideal resistor to be emulated. For a prescribed signal range, the MOSFET in triode region delivers an interval of instantaneous resistance values. We demonstrate that, for the elementary 2‐node network, establishing the design equation at a particular point within this interval guarantees minimum error. This equation is then corroborated for networks of arbitrary size by analyzing them from a stochastic point of view. Following the design methodology proposed, the error committed by an MOS‐based grid when compared with its equivalent ideal RC network is, despite the intrinsic nonlinearities of the transistors, below 1% even under mismatch conditions of 10%. In terms of image processing, this error hardly affects the outcome, which is perceptually equivalent to that of the ideal network. These results, extracted from simulation, are verified in a prototype vision chip with QCIF resolution manufactured in the AMS 0.35µm CMOS‐OPTO process. This prototype incorporates a focal‐plane MOS‐based RC network that performs fully programmable Gaussian filtering. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
39.
Artifact removal in magnetoencephalogram background activity with independent component analysis 总被引:2,自引:0,他引:2
Escudero J Hornero R Abásolo D Fernández A López-Coronado M 《IEEE transactions on bio-medical engineering》2007,54(11):1965-1973
The aim of this study was to assess whether independent component analysis (ICA) could be valuable to remove power line noise, cardiac, and ocular artifacts from magnetoencephalogram (MEG) background activity. The MEGs were recorded from 11 subjects with a 148-channel whole-head magnetometer. We used a statistical criterion to estimate the number of independent components. Then, a robust ICA algorithm decomposed the MEG epochs and several methods were applied to detect those artifacts. The whole process had been previously tested on synthetic data. We found that the line noise components could be easily detected by their frequency spectrum. In addition, the ocular artifacts could be identified by their frequency characteristics and scalp topography. Moreover, the cardiac artifact was better recognized by its skewness value than by its kurtosis one. Finally, the MEG signals were compared before and after artifact rejection to evaluate our method. 相似文献
40.
Luis M. Contreras Alberto Solano Francisco Cano Jesus Folgueira 《International Journal of Network Management》2023,33(4):e2221
Video content consumption is currently dominating the mix of traffic observed in Internet service provider (ISP) networks. The distribution of that content is usually performed by means of content delivery network (CDN) caches storing and delivering multimedia. The advent of virtualization is calling attention to the CDN providers as a use case for virtualizing the cache function. In parallel, there is a trend for sharing network infrastructures as a way of reducing deployment costs by ISPs. Then, an interesting scenario emerges when considering the possibility of sharing virtualized cache functions among ISPs which are sharing a common physical infrastructure, mostly considering that those ISPs offer similar video content catalogs to end users. Furthermore, when deciding to share the caches among ISPs, it is interesting to understand the impacts due to limiting the storage capacity at the edge sites. This paper investigates through simulations the potential efficiencies that can be achieved when sharing a virtual cache function if compared with the classical approach of independent virtual caches operated per ISP, as well as the implications of limiting the storage capacity of the caches at the edge. 相似文献