全文获取类型
收费全文 | 1576篇 |
免费 | 94篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 21篇 |
化学工业 | 404篇 |
金属工艺 | 6篇 |
机械仪表 | 30篇 |
建筑科学 | 68篇 |
矿业工程 | 1篇 |
能源动力 | 40篇 |
轻工业 | 168篇 |
水利工程 | 26篇 |
石油天然气 | 1篇 |
无线电 | 145篇 |
一般工业技术 | 299篇 |
冶金工业 | 137篇 |
原子能技术 | 15篇 |
自动化技术 | 312篇 |
出版年
2024年 | 1篇 |
2023年 | 13篇 |
2022年 | 98篇 |
2021年 | 100篇 |
2020年 | 60篇 |
2019年 | 51篇 |
2018年 | 61篇 |
2017年 | 43篇 |
2016年 | 66篇 |
2015年 | 47篇 |
2014年 | 63篇 |
2013年 | 95篇 |
2012年 | 95篇 |
2011年 | 123篇 |
2010年 | 79篇 |
2009年 | 84篇 |
2008年 | 86篇 |
2007年 | 79篇 |
2006年 | 59篇 |
2005年 | 55篇 |
2004年 | 46篇 |
2003年 | 31篇 |
2002年 | 27篇 |
2001年 | 22篇 |
2000年 | 14篇 |
1999年 | 18篇 |
1998年 | 32篇 |
1997年 | 27篇 |
1996年 | 15篇 |
1995年 | 5篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1990年 | 2篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1970年 | 1篇 |
排序方式: 共有1673条查询结果,搜索用时 31 毫秒
31.
Some applications require autonomous robots to search an initially unknown environment for static targets, without any a priori information about environment structure and target locations. Targets can be human victims in search and rescue or materials
in foraging. In these scenarios, the environment is incrementally discovered by the robots exploiting exploration strategies
to move around in an autonomous and effective way. Most of the strategies proposed in literature are based on the idea of
evaluating a number of candidate locations on the frontier between the known and the unknown portions of the environment according
to ad hoc utility functions that combine different criteria. In this paper, we show some of the advantages of using a more theoretically-grounded
approach, based on Multi-Criteria Decision Making (MCDM), to define exploration strategies for robots employed in search and
rescue applications. We implemented some MCDM-based exploration strategies within an existing robot controller and we evaluated
their performance in a simulated environment. 相似文献
32.
Sergio Saponara Nicola E. L’Insalata Luca Fanucci 《Microprocessors and Microsystems》2009,33(3):191-200
The paper presents an automated environment for fast design space exploration and automatic generation of FFT/IFFT macrocells with minimum circuit and memory complexity within the numerical accuracy budget of the target application. The effectiveness of the tool is demonstrated through FPGA and CMOS implementations (90 nm, 65 nm and 45 nm technologies) of the baseband processing in embedded OFDM transceivers. Compared with state-of-art FFT/IFFT IP cores, the proposed work provides macrocells with lower circuit complexity while keeping the same system performance (throughput, transform size and accuracy) and is the first addressing the requirements of all OFDM standards including MIMO systems: 802.11 WLAN, 802.16 WMAN, Digital Audio and Video Broadcasting in terrestrial, handheld and hybrid satellite-scenarios, Ultra Wide Band, Broadband on Power Lines, xDSL. 相似文献
33.
Nicola M. Dring 《Computers in human behavior》2009,25(5):1089-1101
The body of empirical research on Internet sexuality has grown steadily since 1993. The following paper provides an overview of the current state of research in this field in its full thematic breadth, addressing six areas of online sexuality: Pornography, sex shops, sex work, sex education, sex contacts, and sexual subcultures. Key research results are presented concerning Internet sexuality’s forms of manifestation, participant groups, opportunities, and risks. This paper shows that sexually related online activities have become routine in recent years for large segments of the population in the Western world. Internet sexuality also takes somewhat different forms based on the age, gender, and sexual orientation of the individual. Academic studies to date have focused overwhelmingly on the possible negative effects of Internet sexuality. By contrast, little research has been conducted on potential benefits. Consequently, a surprising number of gaps are evident in the scholarship on Internet sexuality. 相似文献
34.
Enrico Giunchiglia Nicola Leone Marco Maratea 《Annals of Mathematics and Artificial Intelligence》2008,53(1-4):169-204
In this paper, we study the relation among Answer Set Programming (ASP) systems from a computational point of view. We consider smodels, dlv, and cmodels ASP systems based on stable model semantics, the first two being native ASP systems and the last being a SAT-based system. We first show that smodels, dlv, and cmodels explore search trees with the same branching nodes (assuming, of course, a same branching heuristic) on the class of tight logic programs. Leveraging on the fact that SAT-based systems rely on the deeply studied Davis–Logemann–Loveland (dll) algorithm, we derive new complexity results for the ASP procedures. We also show that on nontight programs the SAT-based systems are computationally different from native procedures, and the latter have computational advantages. Moreover, we show that native procedures can guarantee the “correctness” of a reported solution when reaching the leaves of the search trees (i.e., no stability check is needed), while this is not the case for SAT-based procedures on nontight programs. A similar advantage holds for dlv in comparison with smodels if the “well-founded” operator is disabled and only Fitting’s operator is used for negative inferences. We finally study the “cost” of achieving such advantages and comment on to what extent the results presented extend to other systems. 相似文献
35.
Enver Sangineto Nicola Capuano Matteo Gaeta Alessandro Micarelli 《Universal Access in the Information Society》2008,7(1-2):1-23
This paper presents an approach to automatic course generation and student modeling. The method has been developed during
the European funded projects Diogene and Intraserv, focused on the construction of an adaptive e-learning platform. The aim
of the platform is the automatic generation and personalization of courses, taking into account pedagogical knowledge on the
didactic domain as well as statistic information on both the student’s knowledge degree and learning preferences. Pedagogical
information is described by means of an innovative methodology suitable for effective and efficient course generation and
personalization. Moreover, statistic information can be collected and exploited by the system in order to better describe
the student’s preferences and learning performances. Learning material is chosen by the system matching the student’s learning
preferences with the learning material type, following a pedagogical approach suggested by Felder and Silverman. The paper
discusses how automatic learning material personalization makes it possible to facilitate distance learning access to both
able-bodied and disabled people. Results from the Diogene and Intraserv evaluation are reported and discussed. 相似文献
36.
Design optimization of an enzymatic assay in an electrokinetically-driven microfluidic device 总被引:1,自引:1,他引:0
Y. T. Atalay P. Verboven S. Vermeir N. Vergauwe F. Delport B. M. Nicolaï J. Lammertyn 《Microfluidics and nanofluidics》2008,5(6):837-849
Microfluidic systems are increasingly popular for rapid and cheap determinations of enzyme assays and other biochemical analysis.
In this study reduced order models (ROM) were developed for the optimization of enzymatic assays performed in a microchip.
The model enzyme assay used was β-galactosidase (β-Gal) that catalyzes the conversion of Resorufin β-d-galactopyranoside (RBG) to a fluorescent product as previously reported by Hadd et al. (Anal Chem 69(17): 3407–3412, 1997). The assay was implemented in a microfluidic device as a continuous flow system controlled electrokinetically and with a
fluorescence detection device. The results from ROM agreed well with both computational fluid dynamic (CFD) simulations and
experimental values. While the CFD model allowed for assessment of local transport phenomena, the CPU time was significantly
reduced by the ROM approach. The operational parameters of the assay were optimized using the validated ROM to significantly
reduce the amount of reagents consumed and the total biochip assay time. After optimization the analysis time would be reduced
from 20 to 5.25 min which would also resulted in 50% reduction in reagent consumption. 相似文献
37.
We give efficient algorithms for distributed computation on oriented, anonymous, asynchronous hypercubes with possible faulty
components (i.e. processors and links) and deterministic processors. Initially, the processors know only the size of the network
and that they are inter-connected in a hypercube topology. Faults may occur only before the start of the computation (and
that despite this the hypercube remains a connected network). However, the processors do not know where these faults are located.
As a measure of complexity we use the total number of bits transmitted during the execution of the algorithm and we concentrate
on giving algorithms that will minimize this number of bits. The main result of this paper is an algorithm for computing Boolean
functions on anonymous hypercubes with bit cost , where is the number of faulty components (i.e. links plus processors), is the number of links which are either faulty, or non-faulty but adjacent to faulty processors, and is the diameter of the hypercube with faulty components.
Received: October 1992 / Accepted: April 2001 相似文献
38.
JG Hurrell NA Nicola WJ Broughton MJ Dilworth E Minasian SJ Leach 《Canadian Metallurgical Quarterly》1976,66(2):389-399
Circular dichroism studies on leghaemoglobins from snake bean, lupin, serradella and other plants show that, in common with soybean (reported earlier) they have a similar overall polypeptide chain conformation and haem environment and orientation. Immunochemical studies, on the other hand, suggest that the antigenic determinants on the surface of the leghaemoglobins vary considerably. Thus, firstly the alpha-helix content of the leghaemoglobins as a class is very similar (60-65%) and approaches that of the myoglobins, secondly, the sign, magnitude and shape of their circular dichroism spectra in the near ultraviolet, Soret and visible regions suggest close similarities in the environment and orientation of a structurally important tryptophan residue and of the haem moiety, and thirdly, there is comparatively weak haem-protein interaction. The extent of immuno cross-reactivity was found to be best deomonstrated using the Farr radioimmunoassay procedure. The results were (a) 5 leghaemoglobins from one plant (soybean) crossreacted completely but with varying affinities. (b) The extent of cross reactivity between leghaemoglobins from different plants was compared to that within a single plant; the reaction of antiserum to a soybean leghaemoglobin with a serradella leghaemoglobin was weak, with a snake bean leghaemoglobin still weaker (and incomplete) while lupin leghaemoglobins showed no cross reactivity at all. (c) The "rapid" attenuation of cross reactivity among different plant leghaemoglobins is explicable in terms of the extensive amino acid substitutions which have been demonstrated in the literature and in the present studies. (d) In view of this rapid divergence it is not surprising that sperm whale and horse heart myoglobins showed no cross reactivity with soybean leghaemoglobins. In summary, amino acid substitutions in the leghaemoglobin family are conformationally but not immunochemically conservative. 相似文献
39.
Functionally graded materials (FGMs) are special composites in which the volume fractions of constituent materials vary gradually, giving continuously graded mechanical properties. The aim of this paper is the evaluation of the strength of structures composed by FGMs incorporating re-entrant corners - tending to the more common crack for vanishing corner angle. The end result is useful in engineering applications predicting the strength of the element corresponding to the unstable brittle crack propagation in such innovative materials. To show the general validity of the method, heterogeneous plates under tension and beam under bending containing re-entrant corners and by varying corner angle, depth and grading of the FGM are considered. Ad hoc performed numerical finite element simulations, by using the FRANC2D code, agree with the theoretical predictions. 相似文献
40.
Innovation in Industrial Districts: Evidence from Italy 总被引:1,自引:0,他引:1
The aim of this paper is to show that Italian manufacturing firms belonging to Marshallian industrial districts carry out a higher innovative effort than is usually acknowledged. The empirical analysis makes use of a panel of 1,218 district and non-district firms belonging to traditional sectors. Data refers to the years 1992 and 1995. We have estimated an augmented Cobb-Douglas production function. The estimates make it possible to empirically identify three different determinants of firms' productivity: (i) the intentional innovative activity; (ii) the “district effect”; and (iii) the joint district and innovation effect. The results show that firms' membership in industrial districts and product innovations are key factors in explaining the productivity of firms working in traditional Italian sectors. 相似文献