全文获取类型
收费全文 | 3479篇 |
免费 | 191篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 48篇 |
综合类 | 1篇 |
化学工业 | 850篇 |
金属工艺 | 77篇 |
机械仪表 | 57篇 |
建筑科学 | 92篇 |
矿业工程 | 4篇 |
能源动力 | 116篇 |
轻工业 | 321篇 |
水利工程 | 24篇 |
石油天然气 | 2篇 |
无线电 | 324篇 |
一般工业技术 | 686篇 |
冶金工业 | 379篇 |
原子能技术 | 21篇 |
自动化技术 | 673篇 |
出版年
2023年 | 43篇 |
2022年 | 93篇 |
2021年 | 133篇 |
2020年 | 98篇 |
2019年 | 88篇 |
2018年 | 99篇 |
2017年 | 92篇 |
2016年 | 128篇 |
2015年 | 105篇 |
2014年 | 137篇 |
2013年 | 210篇 |
2012年 | 228篇 |
2011年 | 251篇 |
2010年 | 194篇 |
2009年 | 178篇 |
2008年 | 188篇 |
2007年 | 152篇 |
2006年 | 152篇 |
2005年 | 102篇 |
2004年 | 93篇 |
2003年 | 81篇 |
2002年 | 58篇 |
2001年 | 39篇 |
2000年 | 37篇 |
1999年 | 49篇 |
1998年 | 117篇 |
1997年 | 76篇 |
1996年 | 55篇 |
1995年 | 46篇 |
1994年 | 48篇 |
1993年 | 35篇 |
1992年 | 15篇 |
1991年 | 23篇 |
1990年 | 12篇 |
1989年 | 15篇 |
1988年 | 11篇 |
1987年 | 13篇 |
1986年 | 7篇 |
1985年 | 10篇 |
1984年 | 10篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 13篇 |
1979年 | 11篇 |
1977年 | 11篇 |
1976年 | 19篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1971年 | 9篇 |
排序方式: 共有3675条查询结果,搜索用时 9 毫秒
11.
This article is based on experiences with data and text mining to gain information for strategic business decisions, using host-based analysis and visualisation (A/V), primarily in the field of patents. The potential advantages of host-based A/V are pointed out and the features of the first such A/V software, STN®AnaVist™, are described in detail. Areas covered include the user interfaces, initial set of documents for A/V, data mining, text mining, reporting, and suggestions for further development. 相似文献
12.
13.
Peridynamic modeling of concrete structures 总被引:3,自引:0,他引:3
Walter Gerstle Nicolas Sau Stewart Silling 《Nuclear Engineering and Design》2007,237(12-13):1250-1258
The peridynamic model described in Silling (Silling, S.A., 1998. Reformation of Elasticity Theory for Discontinuous and Long-Range Forces, SAND98-2176. Sandia National Laboratories, Albuquerque, NM), being a central-force model, is limited to modeling materials with a Poisson's ratio of 1/4. In this paper, the peridynamic model is generalized by adding pairwise peridynamic moments to simulate linear elastic materials with varying Poisson's ratios. The new model is called the “micropolar peridynamic model”. The micropolar peridynamic model is placed within a finite element context to enable efficacious application of boundary conditions and efficient computational solutions using an implicit, rather than an explicit solution algorithm. The implicit solution algorithm is suitable for quasistatic simulation of damage and cracking in concrete structures. With this new model, very simple tensile damage mechanisms at the micro structural (peridynamic) level are sufficient to explain a great deal of the microcracking (damage) and fracture mechanics observed in concrete structures. The new implementation appears to be computationally efficient. 相似文献
14.
Guimond Serge; Dambrun Micha?l; Michinov Nicolas; Duarte Sandra 《Canadian Metallurgical Quarterly》2003,84(4):697
Social dominance orientation (SDO) has been proposed as an important variable in the explanation of prejudice. We distinguish between three conceptualizations of SDO: SDO as a personality trait (personality model), SDO as a moderator of the effects of situational variables (Person X Situation model), and SDO as a mediator of the effect of social position on prejudice (group socialization model [GSM]). Four studies (N = 1,657) looking at the relations between social positions, SDO, and prejudice in a natural setting and in a laboratory setting provide strong support for the GSM. In contrast to previous correlational findings, there is evidence of a cause (dominant social position), an effect (prejudice increases), and a mediator (SDO). These results suggest new perspectives on the integration of individual and contextual determinants of prejudice. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
15.
The electrolytical methanogenic/methanotrophic coupling (eMaMoC) process was tested in a laboratory-scale single-stage reactor for the treatment of tetrachloroethene (PCE)-contaminated waters. A water electrolysis cell was placed directly in the effluent recirculation loop for the supply of both O2 and H2 to the system: H2 serving as the electron donor for both carbonate reduction into CH4 and reductive dechlorination. The concurrent presence of O2 and CH4 could be used by the methanotrophs for co-metabolically oxidising the chlorinated intermediates left over by the anaerobic transformation of PCE. At a PCE inlet of 33-52 microM and a hydraulic residence time (HRT) of 5.6 days, PCE reductive dechlorination to dichloroethene (DCE) was over 95% with a maximum DCE mineralisation of 83%. Fluorescence in situ hybridisation with 16S rRNA probes related to type I and type II methanotrophic bacteria were utilised to localise the methanotrophic communities in the anaerobic/aerobic granules. It evidenced that with operational time, along with increasing oxygenation rate, methanotrophic communities were specifically colonising onto the outermost layer of the anaerobic/aerobic granule. 相似文献
16.
This paper analyses the technical efficiency in the hydroelectric generating plants of a main Portuguese electricity enterprise EDP (Electricity of Portugal) between 1994 and 2004, investigating the role played by increase in competition and regulation. A random cost frontier method is adopted. A translog frontier model is used and the maximum likelihood estimation technique is employed to estimate the empirical model. We estimate the efficiency scores and decompose the exogenous variables into homogeneous and heterogeneous. It is concluded that production and capacity are heterogeneous, signifying that the hydroelectric generating plants are very distinct and therefore any energy policy should take into account this heterogeneity. It is also concluded that competition, rather than regulation, plays the key role in increasing hydroelectric plant efficiency. 相似文献
17.
Ethidium was found to be efficiently cross-linked to DNA by glyoxal. Kinetic studies showed that the rate of the cross-linking reaction is strongly dependent on the glyoxal concentration. Comparative studies using a series of phenanthridines and acridines showed that NH2 groups at both the 2 and 7 positions on the phenanthridine ring are necessary for efficient cross-linking. Studies using synthetic polydeoxynucleotides showed that the 2-amino group of guanine is absolutely required for cross-linking. Fluorescence contact energy transfer and relative viscosity experiments showed that the cross-linked drug remains intercalated into DNA. DNA gel electrophoresis and melting studies demonstrated that cross-linked ethidium does not dissociate the DNA double helix to single strands. 相似文献
18.
Kuhn W.B. Stephenson F.W. Elshabini-Riad A. 《Solid-State Circuits, IEEE Journal of》1996,31(8):1112-1122
This paper presents design techniques and performance bounds for implementing Q-enhanced, LC bandpass filters in silicon IC technologies. These filters offer significant advantages over switched capacitor and Gm-C based designs, including higher frequency of operation and lower power consumption for a given dynamic range. A prototype 200 MHz, fourth-order filter implemented in a 2 μm n-well CMOS process is described, and measured performance is compared with theoretical predictions. The prototype filter operates at a selectivity Q of 100 and draws less than 8 mA when operating from 3 to 5 V supplies, making it potentially suitable for use as a first IF filter in modern cellular and PCS receivers 相似文献
19.
For oxygenation of polyenoic fatty acids by 12- and 15-lipoxygenases the methyl terminus of the substrate constitutes the signal for the initial hydrogen abstraction. In contrast, for 5-lipoxygenases an inverse head to tail substrate orientation has been proposed. However, recent structure-based sequence alignments suggested a conserved uniform substrate orientation for 5S- and 15S-lipoxygenation. Oxygenation of 15S-HETE derivatives by various wild-type and mutant lipoxygenases was investigated, and the evidence proved an inverse substrate orientation: (i) Substrate affinity and Vmax of 15S-HETE oxygenation by arachidonic acid 15-lipoxygenases are >1 order of magnitude lower than the corresponding data for polyenoic fatty acids. 5S,15S- and 14R, 15S-DiH(P)ETE were identified as major reaction products. (ii) Methylation of the carboxylate group of 15S-HETE augmented the reaction rate and shifted the reaction specificity strongly toward 5S-lipoxygenation. In contrast, methyl arachidonate was less effectively oxygenated than the free acid. Methylation of 15S-HETrE(8,11,14), which lacks the C5-C6 double bond, was without major impact on the oxygenation rate and on the product specificity. (iii) Introduction of a bulky glycerol moiety at the carboxylic group of 15S-HETE reversed the kinetic effects of methylation and led to a 14R-oxygenation of the substrate. (iv) When the product pattern of 15S-HETE oxygenation by the recombinant wild-type rabbit 15-lipoxygenase was compared with that formed by the Arg403Leu mutant, 5S- and 8S-lipoxygenations were augmented and 14R, 15S-DiH(P)ETE formation was impaired. (v) Phe353Leu or Ile418Ala mutation of the same enzyme, which favored 12S-HETE formation from arachidonic acid, strongly augmented 8S-lipoxygenation of 15S-HETE methyl ester. These kinetic data and the alterations in the product specificity are consistent with the concept of an inverse head to tail substrate orientation during the oxygenation of 15S-HETE methyl ester and/or of free 15S-HETE by 15-LOXs. For 5S- and 8S-lipoxygenation, 15-HETE may slide into the substrate binding pocket with its carboxy terminus approaching the doubly allylic methylenes C-7 or C-10 to the non-heme iron. 相似文献
20.
Ogier Maitre Frédéric Krüger Stéphane Querry Nicolas Lachiche Pierre Collet 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2012,16(2):261-279
EASEA is a framework designed to help non-expert programmers to optimize their problems by evolutionary computation. It allows
to generate code targeted for standard CPU architectures, GPGPU-equipped machines as well as distributed memory clusters.
In this paper, EASEA is presented by its underlying algorithms and by some example problems. Achievable speedups are also
shown onto different NVIDIA GPGPUs cards for different optimization algorithm families. 相似文献