全文获取类型
收费全文 | 782篇 |
免费 | 46篇 |
国内免费 | 18篇 |
专业分类
电工技术 | 13篇 |
综合类 | 2篇 |
化学工业 | 203篇 |
金属工艺 | 13篇 |
机械仪表 | 22篇 |
建筑科学 | 23篇 |
矿业工程 | 1篇 |
能源动力 | 42篇 |
轻工业 | 63篇 |
水利工程 | 7篇 |
石油天然气 | 9篇 |
无线电 | 78篇 |
一般工业技术 | 175篇 |
冶金工业 | 36篇 |
原子能技术 | 7篇 |
自动化技术 | 152篇 |
出版年
2024年 | 5篇 |
2023年 | 23篇 |
2022年 | 48篇 |
2021年 | 84篇 |
2020年 | 37篇 |
2019年 | 38篇 |
2018年 | 48篇 |
2017年 | 39篇 |
2016年 | 45篇 |
2015年 | 33篇 |
2014年 | 31篇 |
2013年 | 69篇 |
2012年 | 43篇 |
2011年 | 40篇 |
2010年 | 29篇 |
2009年 | 43篇 |
2008年 | 19篇 |
2007年 | 23篇 |
2006年 | 19篇 |
2005年 | 10篇 |
2004年 | 10篇 |
2003年 | 6篇 |
2002年 | 12篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 8篇 |
1998年 | 12篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1968年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有846条查询结果,搜索用时 15 毫秒
71.
A model set of equations for the low-frequency electromagnetic perturbations in a magnetized nonuniform plasma is presented. A more convenient and systematic procedure is suggested to treat the fluid equations in order to deduce electrostatic and electromagnetic limits. A general dispersion relation is derived for the waves propagating in 3D under local approximation in nonuniform plasmas, which includes almost all the known modes of cold ion magnetized plasmas in the limit <
i
(where
i
is the ion cyclotron frequency). Both the limits 1 and O(1) have been discussed briefly. The shear Alfvén waves and electromagnetic ion acoustic waves near ultra low frequency (ULF) range are found unstable in the high plasma of magnetopause. The results are in complete agreement with the satellite observations. 相似文献
72.
Ultrasonic irradiation applied either above the surface of a chromic acid plating bath or through the plating bath itself during the process of chromium electroplating reduces the emissions of hazardous chromic acid mist The use of ultrasound is particularly effective at high current densities. The results suggest that sonication during the electroplating of chromium may provide a useful method of controlling chrome mist emission without the need for a chemical additive (mist suppressant). In conjunction with lip extraction this could lead to a more efficient process since the use of ultrasound has been shown to be of benefit in the electroplating process itself. 相似文献
73.
Adil Karim Jason Devenport 《Photonics Technology Letters, IEEE》2007,19(5):312-314
An octave-bandwidth microwave photonic link with a third-order limited spurious-free dynamic range of 121 dB in a 1-Hz bandwidth has been demonstrated. The link noise figure of 9 dB at a modulation frequency of 2 GHz was achieved by using a bias-shifted Mach-Zehnder modulator with an optical input power of 500 mW. This level of performance was realized without electronic or optical linearization 相似文献
74.
75.
In complex product design environments, new product development (NPD) becomes all about trade-offs and therefore trade-off management gets an important responsibility for designers. Correspondingly, in these environments, customer co-creation in NPD requires multi-issue negotiation with issue trade-offs. However, there is no study researching customer co-creation in NPD through multi-issue negotiation with issue trade-offs according to our best knowledge. This study presents a framework for customer co-creation in NPD through a multi-issue negotiation mechanism, namely; Modified Even-Swaps, to fill this gap. This mechanism uses a modified version of Even-Swaps method, that finds differences among alternatives and utilizes the differences for assessing the value of multi-issue offers, and that includes a fuzzy-inference-system for bargaining on several issues simultaneously. In the proposed framework, customers are represented by “lead-user”. Thus, negotiation is performed between lead-user and designer. In order to show how the framework works, an illustrative example is also presented. 相似文献
76.
In this paper, a direct solution approach for solving fuzzy multiple objective generalized assignment problems is proposed. In the problem, the coefficients and right hand side values of the constraints and the objective function coefficients are defined as fuzzy numbers. The addressed problem also has a multiple objective structure where the goals are determined so as to minimize the total cost and the imbalance between the workload of the agents. The direct solution approach utilizes the fuzzy ranking methods to rank the objective function values and to determine the feasibility of the constraints within a metaheuristic search algorithm, known as bees algorithm. Different fuzzy ranking methods, namely signed distance, integral value and area based approach are used in bees algorithm. For the computational study, the effects of these fuzzy ranking methods on the quality of the solutions are also analyzed. 相似文献
77.
Mapping quality of the self-organising maps (SOMs) is sensitive to the map topology and initialisation of neurons. In this article, in order to improve the convergence of the SOM, an algorithm based on split and merge of clusters to initialise neurons is introduced. The initialisation algorithm speeds up the learning process in large high-dimensional data sets. We also develop a topology based on this initialisation to optimise the vector quantisation error and topology preservation of the SOMs. Such an approach allows to find more accurate data visualisation and consequently clustering problem. The numerical results on eight small-to-large real-world data sets are reported to demonstrate the performance of the proposed algorithm in the sense of vector quantisation, topology preservation and CPU time requirement. 相似文献
78.
The purpose of these studies was to investigate the ability of surface energy measurements and rates of mixing in dry powder inhaler (DPI) formulations to predict aerosol dispersion performance. Two lactose carrier systems comprising either spray-dried or milled particles were developed such that they had identical physical characteristics except for surface morphology and surface energies avoiding confounding variables common in other studies. Surface energy measurements confirmed significant differences between the powder systems. Spray-dried lactose had a higher surface entropy (0.20 vs. 0.13 mJ/m2K) and surface enthalpy (103.2 vs. 79.2 mJ/m2) compared with milled lactose. Mixing rates of budesonide or fluorescein were assessed dynamically, and significant differences in blending were observed between lactose systems for both drugs. Surface energies of the lactose carriers were inversely proportional to dispersion performance. In addition, the root mean square (RMS) of blending rates correlated positively with aerosol dispersion performance. Both techniques have potential utility in routine screening of DPI formulations. 相似文献
79.
The focus of this article is to develop a surface plasmon resonance (SPR) nanosensor to determine chloramphenicol (CAP) using the molecularly imprinted nanoparticles. The CAP imprinted nanoparticles were prepared by miniemulsion polymerization method. Then, the nanoparticles were attached onto the SPR nanosensor surface via temperature‐controlled evaporation. Surface characterization studies were performed with atomic force microscopy and contact angle measurements. Kinetic studies were performed with CAP solutions in the concentration range of 0.155–6.192 nM. Florphenicol (FLP) and thiamphenicol (TAP) having similar chemical structures to the template (i.e., CAP) were chosen as competitors to determine selectivity of the nanoparticles. Selectivity constants were observed as 8.86 for CAP/TAP and 8.36 for CAP/FLP. The detection limit was calculated as 40 ng/kg honey sample. In the light of these results, it was emphasized that the SPR nanosensor is able to recognize CAP selectively and has a potential for real‐time CAP detection in honey sample. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
80.
Divakar Rajamani Dr Gajendra Kumar Adil 《The International Journal of Advanced Manufacturing Technology》1998,14(4):298-305
Scheduling and sequencing compounds on banbury mixers is a daily production planning function in a tyre company. The current scheduling procedures are based on experience. A number of factors, such as, capacity, cost, time, speed, set-up of mixers, compound changeovers, density and demand of compound, have to be considered during planning. In this paper, we propose a two-stage approach to this problem. This approach can be easily computerised to aid the personnel in the planning function. An example, considering actual data obtained from the company, is used to illustrate the approach. The current scheduling practice by company personnel, as inferred from past record, is also reported. 相似文献