全文获取类型
收费全文 | 1707篇 |
免费 | 114篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 11篇 |
综合类 | 3篇 |
化学工业 | 586篇 |
金属工艺 | 18篇 |
机械仪表 | 27篇 |
建筑科学 | 62篇 |
矿业工程 | 5篇 |
能源动力 | 34篇 |
轻工业 | 261篇 |
水利工程 | 15篇 |
石油天然气 | 2篇 |
无线电 | 104篇 |
一般工业技术 | 264篇 |
冶金工业 | 220篇 |
原子能技术 | 6篇 |
自动化技术 | 204篇 |
出版年
2024年 | 4篇 |
2023年 | 30篇 |
2022年 | 99篇 |
2021年 | 125篇 |
2020年 | 68篇 |
2019年 | 58篇 |
2018年 | 57篇 |
2017年 | 77篇 |
2016年 | 63篇 |
2015年 | 39篇 |
2014年 | 56篇 |
2013年 | 114篇 |
2012年 | 105篇 |
2011年 | 122篇 |
2010年 | 92篇 |
2009年 | 79篇 |
2008年 | 83篇 |
2007年 | 77篇 |
2006年 | 77篇 |
2005年 | 47篇 |
2004年 | 44篇 |
2003年 | 22篇 |
2002年 | 25篇 |
2001年 | 8篇 |
2000年 | 19篇 |
1999年 | 14篇 |
1998年 | 20篇 |
1997年 | 18篇 |
1996年 | 18篇 |
1995年 | 20篇 |
1994年 | 10篇 |
1993年 | 17篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1987年 | 5篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1973年 | 4篇 |
排序方式: 共有1822条查询结果,搜索用时 31 毫秒
91.
Avelin Diana A. Sundarakantham K. Mercy Shalinie S. Rajendran L. 《International Journal of Network Management》2014,24(5):402-414
Home agent is a key component of MIPv6 functionality that comprises binding cache to hold the mobile nodes current point of attachment to the Internet. This paper is concerned with binding cache support for home agents within MIPv6 network. Existing binding cache of home agent supports weak cache consistency by using fixed contract length for Binding Refresh Request, which functions reasonably well in normal situations. However, maintaining a strong binding cache consistency in home agent as a crucial exceptional handling mechanism has become more demanding for the following objectives: (i) to adapt increasingly frequent change of care‐of address due to mobile nodes movement detection update; (ii) to provide fine‐grain controls to balance the binding cache load distributions for better delivery services; and (iii) to reduce the overhead allowances around the binding cache. In this paper, we have first verified the effectiveness of Binding Refresh Request contract length, and on the basis of that, two dynamic contract algorithms are suggested to reduce the storage and communication overhead allowances in binding cache. We have also compared our technique with the existing fixed Binding Refresh Request contract length, and our simulation results reveals that the proposed approach provides an effective performance to reduce overhead within the network. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
92.
Atmospheric DMSO degradation in the gas phase: Cl-DMSO reaction. Temperature dependence and products
Martínez E Aranda A de MY Rodríguez D López MR Albaladejo J 《Environmental science & technology》2002,36(6):1226-1230
The reactions of Cl atoms and ClO radicals with CH3-SOCH3 (DMSO) have been studied using the discharge flow method with direct detection of DMSO, CO, and products by mass spectrometry. The absolute rate constant at room temperature measured for reaction 1, (CH3)2SO + Cl --> products, was k(1) = (1.7 +/- 0.3) x 10(-11) cm3 molecule(-1) s(-1). For reaction 2, (CH3)2SO + ClO --> products, only an upper limit could be established, k(2) < or = 6 x 10(-14) cm3 molecule(-1) s(-1) Reaction 1 has been found to proceed through adduct formation and further decomposition involving the cleavage of the C-S bound. The pressure effect on the Cl-DMSO reaction from 0.5 to 3 Torr was negligible, and the temperature dependence in the range 273-335 K was also very slight. The results obtained are related to previous studies of sulfur compounds, and the atmospheric implications are also discussed in relation to the homogeneous sinks of DMSO. Tropospheric lifetimes of DMSO based on average Cl and ClO concentrations and the measured rate constants have been calculated showing that the contribution of reaction 1 must be of minor relevance in the marine boundary layer. Reaction 2 is so slow that it does not play any role within the atmospheric sulfur chemistry. 相似文献
93.
Application of the Tauc-Lorentz formulation to the interband absorption of optical coating materials
Recent progress in ellipsometry instrumentation permits precise measurement and characterization of optical coating materials in the deep-UV wavelength range. Dielectric coating materials exhibit their first electronic interband transition in this spectral range. The Tauc-Lorentz model is a powerful tool with which to parameterize interband absorption above the band edge. The application of this model for the parameterization of the optical absorption of TiO2, Ta2O5, HfO2, Al2O3, and LaF3 thin-film materials is described. 相似文献
94.
The authors devised a prestimulus-probe method to assess the allocation of attention as a function of participants' top-down expectancies concerning distractor and target locations. Participants performed the flanker task, and distractor locations remained fixed. On some trials, instead of the flanker display, either 2 simultaneous dots or a horizontal line appeared. The dot in the expected distractor location was perceived to occur before the dot in the expected empty location, and the line appeared to extend from the expected distractor location to the expected empty location, suggesting that attention is allocated to expected distractor locations prior to stimulus onset. The authors propose that a process-all mechanism guides attention to expected locations of all stimuli regardless of task demands and that this constitutes a major cause for failures of selective attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
95.
96.
A method is reported for fabricating complex 3D silver‐coated polymeric microstructures. The approach is based on the creation of a crosslinked polymeric microscaffold via patterned multiphoton‐initiated polymerization followed by surface‐nucleated electroless deposition of silver. The conductivity and reflectivity of the resulting silver–polymer composites and the nanoscale morphology of the deposited silver are characterized. Sub‐micrometer thick layers of silver can be controllably deposited onto surfaces, including those of 3D microporous forms without occluding the interior of the structure. The approach is general for silver coating crosslinked polymeric structures based on acrylate, methacrylate, and epoxide resins and provides a new path to complex 3D micrometer‐scale devices with electronic, photonic, and electromechanical function. 相似文献
97.
We present two methods for determining the sentiment expressed by a movie review. The semantic orientation of a review can be positive, negative, or neutral. We examine the effect of valence shifters on classifying the reviews. We examine three types of valence shifters: negations, intensifiers, and diminishers. Negations are used to reverse the semantic polarity of a particular term, while intensifiers and diminishers are used to increase and decrease, respectively, the degree to which a term is positive or negative. The first method classifies reviews based on the number of positive and negative terms they contain. We use the General Inquirer to identify positive and negative terms, as well as negation terms, intensifiers, and diminishers. We also use positive and negative terms from other sources, including a dictionary of synonym differences and a very large Web corpus. To compute corpus-based semantic orientation values of terms, we use their association scores with a small group of positive and negative terms. We show that extending the term-counting method with contextual valence shifters improves the accuracy of the classification. The second method uses a Machine Learning algorithm, Support Vector Machines. We start with unigram features and then add bigrams that consist of a valence shifter and another word. The accuracy of classification is very high, and the valence shifter bigrams slightly improve it. The features that contribute to the high accuracy are the words in the lists of positive and negative terms. Previous work focused on either the term-counting method or the Machine Learning method. We show that combining the two methods achieves better results than either method alone. 相似文献
98.
Six published methods of rotor slip estimation for sensorless speed control were evaluated using simulated data. Only two of these showed signs of being usable. Both are based on the steady-state machine model and produce a fair slip accuracy for a machine running under perfect field alignment conditions. It was not determined whether the other four techniques were unsuccessful because they require a closed-loop speed controller, were presented incorrectly in the literature, or contain fundamental deficiencies. On the basis of these evaluations, a new technique was developed, and both measured and predicted results are presented to show that it works well. Moreover, this new technique has many features that make it theoretically and practically more attractive than most existing techniques 相似文献
99.
100.
Diana M. R. Harvey 《Journal of microscopy》1982,127(2):209-221
Freeze-substitution is a technique suitable for the preparation of unicellular and multicellular plant and animal specimens for conventional light microscopy, TEM and SEM. It is also widely used as a means of preparing animal and plant tissues for the localization of water soluble substances by analytical electron microscopy, autoradiography or visual detection of precipitates. The technical requirements of preparation, together with an evaluation of the procedures, are presented for various applications. Careful selection and evaluation of freezing technique, substitution solvent and regime are required for meaningful results. 相似文献