全文获取类型
收费全文 | 1425篇 |
免费 | 57篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 29篇 |
综合类 | 4篇 |
化学工业 | 411篇 |
金属工艺 | 31篇 |
机械仪表 | 29篇 |
建筑科学 | 70篇 |
矿业工程 | 5篇 |
能源动力 | 24篇 |
轻工业 | 215篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 98篇 |
一般工业技术 | 226篇 |
冶金工业 | 209篇 |
原子能技术 | 7篇 |
自动化技术 | 122篇 |
出版年
2022年 | 13篇 |
2021年 | 24篇 |
2020年 | 13篇 |
2019年 | 13篇 |
2018年 | 25篇 |
2017年 | 21篇 |
2016年 | 27篇 |
2015年 | 29篇 |
2014年 | 41篇 |
2013年 | 77篇 |
2012年 | 52篇 |
2011年 | 64篇 |
2010年 | 32篇 |
2009年 | 47篇 |
2008年 | 45篇 |
2007年 | 55篇 |
2006年 | 58篇 |
2005年 | 28篇 |
2004年 | 27篇 |
2003年 | 27篇 |
2002年 | 34篇 |
2001年 | 25篇 |
2000年 | 18篇 |
1999年 | 24篇 |
1998年 | 56篇 |
1997年 | 28篇 |
1996年 | 22篇 |
1995年 | 25篇 |
1994年 | 20篇 |
1993年 | 26篇 |
1992年 | 21篇 |
1991年 | 14篇 |
1990年 | 14篇 |
1989年 | 12篇 |
1988年 | 18篇 |
1987年 | 19篇 |
1986年 | 16篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 16篇 |
1981年 | 10篇 |
1980年 | 23篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 22篇 |
1975年 | 16篇 |
1974年 | 13篇 |
1972年 | 13篇 |
1934年 | 10篇 |
排序方式: 共有1483条查询结果,搜索用时 15 毫秒
91.
Dirk Heinrich Roland Wursche 《中国眼镜科技杂志》2007,(7):109-111
眼镜的发展史,在某种程度上说,也就是新材料、新技术的发展史,正是由于新材料、新技术的不断涌现和改进,才推动了眼镜制造工艺的不断提高。 相似文献
92.
Common lumped-element FET modelling is compared with the equivalent distributed-element formulation. The deviations are studied and the validity range of such lumped-element models is shown. 相似文献
93.
Examined the psychosocial and physical problems of 32 Ss with cancer by comparing them to Ss with cardiac disease with a similar functional performance status and to Ss without any illnesses. All Ss completed a cancer inventory of problem situations. Ss with cancer were found to have a larger number of problems and more severe problems than Ss with cardiac disease. Some of the problem subscales that were particularly notable for cancer patients were Functional Health Status, Body Image, Weight Maintenance, Worry, Sexual Dysfunction, Problems Associated with Treatment, and Job-Related. Ss with cancer and cardiac disease did not differ greatly from one another or from the healthy controls in subscales associated with the medical setting. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
94.
95.
Fault-tolerant communication and energy efficiency are important requirements for future-generation wireless ad hoc networks,
which are increasingly being considered also for critical application domains like embedded systems in automotive and aerospace.
Topology control, which enables multi-hop communication between any two network nodes via a suitably constructed overlay network,
is the primary target for increasing connectivity and saving energy here. In this paper, we present a fault-tolerant distributed
topology control algorithm that constructs and continuously maintains a k-regular and k-node-connected overlay for energy-efficient multi-hop communication. As a by-product, it also builds a hierarchy of clusters
that reflects the node density in the network, with guaranteed and localized fault-tolerant communication between any pair
of cluster members. The construction algorithm automatically adapts to a dynamically changing environment, is guaranteed to
converge, and exhibits good performance as well. 相似文献
96.
Nasir Mahmood Mohammad Sohail Khan Asad Ullah Khan Klaus Werner Stöckelhuber Gert Heinrich 《应用聚合物科学杂志》2010,117(3):1493-1501
This article reports the purification and surface modification of coal ash silica and afterwards its utilization as reinforcing filler in solution‐styrene‐butadiene rubber/butadiene rubber (S‐SBR/BR). The coal ash silica free of unwanted metal ions/mineral oxides was obtained using phosphoric acid. The chemical composition of the purified coal ash silica in comparison to impure coal ash indicates the presence of characteristic hydroxyl functional group at 3440 cm?1 and an increase in the oxygen content as determined with the help of Fourier Transform Infrared and x‐ray photoelectron spectroscopy, respectively. The contact angle analysis shows that after purification the polar part of the surface energy increased to 17.5 from 12 m Jm?2. While the surface area increased to an order of magnitude, i.e., 11.6 to 110.5 m2 g?1. The modification of purified silica particles with bis(3‐triethoxysilylpropyl) tetrasulfane reveal the functionalization of hydroxyl to ‐Si‐O‐R groups as detected at 1560 cm?1. As a consequence, the modified silica based S‐SBR/BR composite resulted in improved mechanical properties due to enhanced silica‐rubber interaction. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
97.
Nowadays, software tools for the flowsheet simulation of industrial processes are commonly used for design, simulation, balancing, troubleshooting and optimization purposes. Most of the tools are applicable to fluid processes only and cannot be effectively used for processes which involve solids.In this contribution we want to present the conceptual design of a new system applicable for the dynamic flowsheet simulation of complex solids processes. This system is developed as an enhancement to the existing simulation program.The novel software is able to simulate the unsteady behaviour of complex circuits of granulation processes. The transient behaviour during the start-up and changing of the process or material parameters can also be examined.As flowsheet examples, a typical spray granulation process with different schemes consisting of fluidized bed granulators, screens, mill and splitters was used. The mathematical model of the fluidized bed granulator is described by a one-dimensional population balance equation and coupled with heat and mass transfer and simple fluid dynamics.Received simulation results have shown that the proposed concept of the dynamic flowsheet simulation of granulation processes can be used effectively and has the potential to be generalized for other types of solids processes. 相似文献
98.
Birgit Palm Jürgen G. Heinrich Joachim Reuer 《International Journal of Applied Ceramic Technology》2010,7(2):226-234
The essential influences of 15 parameters on defects (cracks and bubbles) during production of tableware have been studied with 16 experimental progressions using a L16(215) experimental design by G. Taguchi. Evaluation (analysis of means and analysis of variance) indicated that in this production liter weight, drying time, moisture before biscuit firing, and position in the biscuit-firing kiln have a significant influence on cracks. Concerning bubbles, parameters with an influence are liter weight, gate system, mold material, and moisture content before glost firing. Rejects of the article used in the experiments were reduced from 2.44% to 2.27% with respect to cracks and from 6.22% to 0% with respect to bubbles. 相似文献
99.
Precipitated oxalates are often nanostructured and can be used as precursors for nanostructured oxides for different applications. The modification of the particle shape and nanostructures of both copper and cobalt oxalates has been demonstrated using polymeric additives or complexing counter-ions. In the case of cobalt oxalate the characteristic elongated rod particle shape (axial ratio of 10) can be modified by using polymethymethacrylate (PMMA) to produce particles with lower axial ratios of 2, through cubes all the way to platelets (axial ratio 0.2). The PMMA inhibits the growth of the particles along the [101] direction more and more strongly as the concentration of the polymer increases. The crystallite size from XRD line broadening is not modified by the PMMA indicating that the PMMA does not influence the nucleation and growth but modifies the aggregation kinetics. Copper oxalates precipitated in the presence of different cellulose derived polymers with different molecular weights and functional groups (methyl and propyl) showed sensitivity to both molecular weight and functional group. Higher molecular weights did not influence the copper oxalate particle shape, whereas methyl cellulose gave elongated particles and propyl celluloses gave platelet like particles. Copper oxalate precipitated in the presence of acetate counter ions gave platelets with an axial ratio of 0.15 compared to the cushion-like morphology (axial ratio 0.5). The primary crystallites were more elongated along the [001] direction in the presence of acetate, modifying the proportion of the hydrophobic and hydrophilic surfaces and hence influencing the aggregation kinetics and particle shape. The copper and cobalt oxalate particle formation seems to be dominated by the primary particle aggregation with the different additives interacting specifically with different crystallographic faces of the primary particles. By tuning this interaction particles with different shapes and substructures can be formed. 相似文献
100.
Rava M Verlato G Bono R Ponzio M Sartori S Blengio G Kuenzli N Heinrich J Götschi T de Marco R 《The Science of the total environment》2007,384(1-3):163-170
The aim of this study is to find and test a predictive model that could be suitable to estimate the outdoor NO(2) concentrations at individual level, by integrating ecological measurements recorded by local monitoring stations with individual information collected by a questionnaire. For this purpose, the data from the Italian centres of the European Community Respiratory Health Survey II (ECRHS II) has been used. Outdoor NO(2) concentrations were measured using NO(2) passive sampling tubes (PS-NO(2)), exposed outdoor for 14 days, between January 2001 and January 2003. Simultaneously, average NO(2) concentrations were collected from all the monitoring stations of the three centres (MS-NO(2)). Individual measurements carried out with passive samplers were compared with the corresponding NO(2) 2-week concentrations obtained as the average of all local (background and traffic) monitoring stations (MS-NO(2)). A multiple linear regression model was fitted to the data using the 2-week PS-NO(2) concentrations as the response variable and questionnaire information and MS-NO(2) concentrations as predictors. The model minimizing the root mean square error (RMSE), obtained from a ten-fold cross validation, was selected. The model with the best predictive ability included centre, season of the survey, MS-NO(2) concentrations, type and age of building, residential area and reported intensity of heavy-duty traffic and explained the 68.9% of the variance. The non-parametric correlation between PS-NO(2) and the concentrations estimated by the model is 0.81 (95% CI: 0.77-0.85). This study shows that over short periods (2 weeks) a good prediction of home outdoor exposure to NO(2) can be achieved by simply combining routinely collected ecological data with dwelling characteristics and self-reported intensity of heavy traffic. Further studies are needed to extend this prediction to long-term exposure. 相似文献