全文获取类型
收费全文 | 3341篇 |
免费 | 47篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 27篇 |
综合类 | 1篇 |
化学工业 | 280篇 |
金属工艺 | 35篇 |
机械仪表 | 30篇 |
建筑科学 | 19篇 |
矿业工程 | 5篇 |
能源动力 | 55篇 |
轻工业 | 102篇 |
水利工程 | 10篇 |
石油天然气 | 1篇 |
无线电 | 182篇 |
一般工业技术 | 292篇 |
冶金工业 | 2153篇 |
原子能技术 | 7篇 |
自动化技术 | 194篇 |
出版年
2023年 | 10篇 |
2022年 | 21篇 |
2021年 | 45篇 |
2020年 | 31篇 |
2019年 | 29篇 |
2018年 | 41篇 |
2017年 | 38篇 |
2016年 | 37篇 |
2015年 | 29篇 |
2014年 | 44篇 |
2013年 | 100篇 |
2012年 | 49篇 |
2011年 | 63篇 |
2010年 | 46篇 |
2009年 | 54篇 |
2008年 | 76篇 |
2007年 | 60篇 |
2006年 | 44篇 |
2005年 | 49篇 |
2004年 | 33篇 |
2003年 | 29篇 |
2002年 | 27篇 |
2001年 | 16篇 |
2000年 | 15篇 |
1999年 | 69篇 |
1998年 | 635篇 |
1997年 | 345篇 |
1996年 | 284篇 |
1995年 | 174篇 |
1994年 | 127篇 |
1993年 | 131篇 |
1992年 | 40篇 |
1991年 | 58篇 |
1990年 | 48篇 |
1989年 | 31篇 |
1988年 | 37篇 |
1987年 | 43篇 |
1986年 | 37篇 |
1985年 | 41篇 |
1984年 | 14篇 |
1983年 | 19篇 |
1982年 | 11篇 |
1981年 | 15篇 |
1980年 | 15篇 |
1978年 | 13篇 |
1977年 | 40篇 |
1976年 | 117篇 |
1975年 | 11篇 |
1974年 | 9篇 |
1973年 | 8篇 |
排序方式: 共有3393条查询结果,搜索用时 62 毫秒
91.
When a jet of soluble gas is directed on to liquid surface, the kinetic energy of the jet is transferred to the liquid giving rise to circulation, which in turn enhances mass transfer. Consequently, the mass transfer coefficient is related to the characteristics of the jet. 相似文献
92.
Krishnendu Chatterjee Monika Henzinger Sebastian Krinninger Danupon Nanongkai 《Algorithmica》2014,70(3):457-492
Energy games belong to a class of turn-based two-player infinite-duration games played on a weighted directed graph. It is one of the rare and intriguing combinatorial problems that lie in NP∩co-NP, but are not known to be in P. The existence of polynomial-time algorithms has been a major open problem for decades and apart from pseudopolynomial algorithms there is no algorithm that solves any non-trivial subclass in polynomial time. In this paper, we give several results based on the weight structures of the graph. First, we identify a notion of penalty and present a polynomial-time algorithm when the penalty is large. Our algorithm is the first polynomial-time algorithm on a large class of weighted graphs. It includes several worst-case instances on which previous algorithms, such as value iteration and random facet algorithms, require at least sub-exponential time. Our main technique is developing the first non-trivial approximation algorithm and showing how to convert it to an exact algorithm. Moreover, we show that in a practical case in verification where weights are clustered around a constant number of values, the energy game problem can be solved in polynomial time. We also show that the problem is still as hard as in general when the clique-width is bounded or the graph is strongly ergodic, suggesting that restricting the graph structure does not necessarily help. 相似文献
93.
Roderick Bloem Krishnendu Chatterjee Karin Greimel Thomas A. Henzinger Georg Hofferek Barbara Jobstmann Bettina Könighofer Robert Könighofer 《Acta Informatica》2014,51(3-4):193-220
Systems should not only be correct but also robust in the sense that they behave reasonably in unexpected situations. This article addresses synthesis of robust reactive systems from temporal specifications. Existing methods allow arbitrary behavior if assumptions in the specification are violated. To overcome this, we define two robustness notions, combine them, and show how to enforce them in synthesis. The first notion applies to safety properties: If safety assumptions are violated temporarily, we require that the system recovers to normal operation with as few errors as possible. The second notion requires that, if liveness assumptions are violated, as many guarantees as possible should be fulfilled nevertheless. We present a synthesis procedure achieving this for the important class of GR(1) specifications, and establish complexity bounds. We also present an implementation of a special case of robustness, and show experimental results. 相似文献
94.
NH3-NO/NO2 SCR for diesel exhausts after treatment: mechanism and modelling of a catalytic converter
Nova Isabella Ciardelli Cristian Tronconi Enrico Chatterjee Daniel Weibel Michel 《Topics in Catalysis》2007,42(1-4):43-46
We review herein the key mechanistic and kinetic features of the reactions involved in the NH3-NO/NO2 SCR system investigated by dynamic reactive experiments over a V-based commercial powdered catalyst, eventually leading to
the proposal of an original redox scheme which accounts for stoichiometry, selectivity and intrinsic kinetics of the global
SCR process. 相似文献
95.
Uma Chatterjee 《Polymer》2005,46(5):1575-1582
ATRP of several methacrylates viz. methyl methacrylate (MMA), ethyl methacrylate (EMA), n-butyl methacrylate (nBMA), t-butyl methacrylate (tBMA), benzyl methacrylate (BzMA) and (N,N-dimethylamino)ethyl methacrylate (DMAEMA) has been studied in neat as well as aqueous (up to 12 vol% water) acetone at 35 °C using CuCl/bipyridine (bpy) catalyst and ethyl 2-bromoisobutyrate as the initiator. Addition of water significantly enhances the rate of polymerization without losing control. Unlike CuCl/bpy the CuBr/bpy catalyst gives poor control which is attributed to the lower solubility and consequent heterogeneity in the latter case. Of the other ligands used with the CuCl catalyst viz. o-phenanthroline (o-phen), 1,1,4,7,7-pentamethyldiethylenetriamine (PMDETA), 1,1,4,7,10,10-hexamethyltriethylenetetramine (HMTETA), Me6TREN only o-phen offers reasonably good control. The CuCl/bpy catalyst system has been used also in preparing some di- and tri-block copolymers with reasonably low polydispersity index (PDI) at ambient temperature (35 °C) using aqueous acetone as the solvent. The following block copolymers have been prepared PMMA-tBMA, PMMA-b-tBMA-b-MMA, PMMA-DMAEMA, by this method. 相似文献
96.
Chatterjee Abhishek Ghaednia Hamid Bowling Alan Brake Matthew 《Multibody System Dynamics》2021,51(1):45-90
Multibody System Dynamics - Collision between hard objects causes abrupt changes in the velocities of the system, which are characterized by very large contact forces over very small time... 相似文献
97.
Machinability of a nickel aluminide intermetallic alloy 总被引:3,自引:0,他引:3
S. Chatterjee 《Journal of Materials Engineering and Performance》1993,2(1):101-105
This article reports the results of an experimental study on the machinability of a nickel aluminide intermetallic alloy.
Machining was conducted at various speeds, and results indicate low material removal rates. Chips collected for each test
run were measured for thickness for shear angle calculation and were subsequently observed microscopically. Chip segmentation
was observed microscopically, and a fluctuation in the shear angle was evidenced. A parameter characterizing the severity
of the machining process, the chip reduction coefficient (K), was calculated from chip thickness measurements. The calculated values ofK were found to be low, indicating a low severity of the metalcutting process. This, however, is in contract with the observed
low rates of metal removal and low tool life. Thus, conventional metalcutting characterization parameters require re- examination
in terms of machining high-strength materials. 相似文献
98.
The effects of silicon on the properties of tantalum 总被引:2,自引:0,他引:2
K. D. Moser B.S. T. K. Chatterjee M.S. P. Kumar Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1989,41(10):50-53
The microalloying of tantalum with silicon has been effectively used on a commercial scale. However, data on effects of microalloying on processibility, microstructure and mechanical properties are not readily available. To develop some data, tantalum powder with various levels of silicon (0–50 ppm) was processed under identical conditions. Sheet samples were then annealed at different temperatures and evaluated via microstructural, chemical and mechanical tests. The recrystallization temperature was found to increase with silicon content, most probably as a result of the presence of an intermetallic (Ta3Si) phase. The mechanical properties of unrecrystallized tantalum are, as expected, significantly different from those of recrystallized tantalum. 相似文献
99.
Subhashis Chatterjee Bappa Maji 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》2016,20(10):4023-4035
Estimation of reliability and the number of faults present in software in its early development phase, i.e., requirement analysis or design phase is very beneficial for developing reliable software with optimal cost. Software reliability prediction in early phase of development is highly desirable to the stake holders, software developers, managers and end users. Since, the failure data are unavailable in early phase of software development, different reliability relevant software metrics and similar project data are used to develop models for early software fault prediction. The proposed model uses the linguistic values of software metrics in fuzzy inference system to predict the total number of faults present in software in its requirement analysis phase. Considering specific target reliability, weightage of each input software metrics and size of software, an algorithm has been proposed here for developing general fuzzy rule base. For model validation of the proposed model, 20 real software project data have been used here. The linguistic values from four software metrics related to requirement analysis phase have been considered as model inputs. The performance of the proposed model has been compared with two existing early software fault prediction models. 相似文献
100.
Wenjing Wang Shameek Bhattacharjee Mainak Chatterjee Kevin Kwiat 《Pervasive and Mobile Computing》2013,9(4):572-587
In cognitive radio networks, cognitive nodes operate on a common pool of spectrum where they opportunistically access and use parts of the spectrum not being used by others. Though cooperation among nodes is desirable for efficient network operations and performance, there might be some malicious nodes whose objective could be to hinder communications and disrupt network operations. The absence of a central authority or any policy enforcement mechanism makes these kinds of open-access network more vulnerable and susceptible to attacks.In this paper, we analyze a common form of denial-of-service attack, i.e., collaborative jamming. We consider a network in which a group of jammers tries to jam the channels being used by legitimate users who in turn try to evade the jammed channels. First, we compute the distribution of the jamming signal that a node experiences by considering a random deployment of jammers. Then, we propose different jamming and defending schemes that are employed by the jammers and legitimate users, respectively. In particular, we model and analyze the channel availability when the legitimate users randomly choose available channels and the jammers jam different channels randomly. We propose a multi-tier proxy-based cooperative defense strategy to exploit the temporal and spatial diversity for the legitimate secondary users in an infrastructure-based centralized cognitive radio network. Illustrative results on spectrum availability rates show how to improve resiliency in cognitive radio networks in the presence of jammers. 相似文献