全文获取类型
收费全文 | 2722篇 |
免费 | 148篇 |
专业分类
电工技术 | 22篇 |
综合类 | 1篇 |
化学工业 | 636篇 |
金属工艺 | 48篇 |
机械仪表 | 38篇 |
建筑科学 | 84篇 |
矿业工程 | 3篇 |
能源动力 | 117篇 |
轻工业 | 480篇 |
水利工程 | 16篇 |
石油天然气 | 7篇 |
无线电 | 238篇 |
一般工业技术 | 311篇 |
冶金工业 | 574篇 |
原子能技术 | 19篇 |
自动化技术 | 276篇 |
出版年
2023年 | 17篇 |
2022年 | 46篇 |
2021年 | 75篇 |
2020年 | 51篇 |
2019年 | 59篇 |
2018年 | 63篇 |
2017年 | 50篇 |
2016年 | 78篇 |
2015年 | 66篇 |
2014年 | 102篇 |
2013年 | 155篇 |
2012年 | 118篇 |
2011年 | 173篇 |
2010年 | 149篇 |
2009年 | 134篇 |
2008年 | 149篇 |
2007年 | 112篇 |
2006年 | 82篇 |
2005年 | 67篇 |
2004年 | 62篇 |
2003年 | 61篇 |
2002年 | 52篇 |
2001年 | 48篇 |
2000年 | 36篇 |
1999年 | 59篇 |
1998年 | 201篇 |
1997年 | 127篇 |
1996年 | 72篇 |
1995年 | 44篇 |
1994年 | 43篇 |
1993年 | 46篇 |
1992年 | 17篇 |
1991年 | 31篇 |
1990年 | 15篇 |
1989年 | 15篇 |
1988年 | 16篇 |
1987年 | 23篇 |
1986年 | 16篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 12篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 15篇 |
1976年 | 21篇 |
1974年 | 7篇 |
1971年 | 5篇 |
排序方式: 共有2870条查询结果,搜索用时 31 毫秒
101.
102.
103.
Alberto Reyna Marco A. Panduro Carlos del Rio-Bocio 《Expert systems with applications》2012,39(8):6872-6878
The design of an aperiodic planar array is presented in this research. This design of aperiodic arrays considers the reduction of the side lobe level and the isoflux radiation requirements for GEO (Geostationary Earth Orbit) satellite applications. In this way, it is considered four different optimization cases. The first two cases are optimizations of amplitude and phase excitations for the antenna elements in a uniform antenna array and the last two cases are optimizations of positions of the antenna elements and certain number of levels of amplitude excitation in an aperiodic array. In this case, it is proposed a simple new approach combining the main idea of both thinned theory and random arrays approaches. For this optimization problem, the well-known method of Genetic Algorithms (GA) is utilized. The obtained results show the proper performance of the array factor to provide the isoflux radiation and low side lobe level. Depending on the performance requirements, the design of the aperiodic array could lead the satellite hardware to be reduced significantly even more that results presented previously in the literature. 相似文献
104.
In vitro digestibility of phenolic compounds from edible fruits: could it be explained by chemometrics?
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Francisco J. Olivas‐Aguirre Marcela Gaytán‐Martínez Sandra O. Mendoza‐Díaz Gustavo A. González‐Aguilar Joaquín Rodrigo‐García Nina del Rocío Martínez‐Ruiz Abraham Wall‐Medrano 《International Journal of Food Science & Technology》2017,52(9):2040-2048
The health benefits of phenolic compounds depend on the ingested amount, molecular diversity and gastrointestinal digestibility. The phenolic profile of eight fruits (blackberry, blueberry, strawberry, raspberry, mulberry, pomegranate, green and red globe grapes) was chemometrically associated with their in vitro digestibility (oral, gastric, intestinal). Extractable phenols, flavonoids and anthocyanins strongly correlated with each other (r ≥ 0.84), proanthocyanidins with anthocyanins (r = 0.62) and hydrolysable phenols with both extractable phenols (r = 0.45) and proanthocyanidins (r = ?0.54). Two principal components explained 93% of the variance [61% (free‐phenols), 32% (bounded‐phenols)], and four clusters were confirmed by hierarchical analysis, based in their phenolic richness (CLT 1‐4: low to high) and molecular diversity. In vitro digestibility of extractable phenols and flavonoids was blackberry (CLT‐4)> raspberry (CLT‐2)> red grape (CLT‐1) related to their phenolic richness (r ≥ 0.96; P < 0.001), but anthocyanins’ digestibility was pH‐dependent. Chemometrics is useful to predict the in vitro digestibility of phenolic compounds in the assayed fruits. 相似文献
105.
Ignacio G. del Amo David A. Pelta Juan R. González Antonio D. Masegosa 《Applied Soft Computing》2012,12(10):3176-3192
This work presents a study on the performance of several algorithms on different continuous dynamic optimization problems. Eight algorithms have been used: SORIGA (an Evolutionary Algorithm), an agents-based algorithm, the mQSO (a widely used multi-population PSO) as well as three heuristic-rule-based variations of it, and two trajectory-based cooperative strategies. The algorithms have been tested on the Moving Peaks Benchmark and the dynamic version of the Ackley, Griewank and Rastrigin functions. For each problem, a wide variety of configuration variations have been used, emphasizing the influence of dynamism, and using a full-factorial experimental design. The results give an interesting overview of the properties of the algorithms and their applicability, and provide useful hints to face new problems of this type with the best algorithmic approach. Additionally, a recently introduced methodology for comparing a high number of experimental results in a graphical way is used. 相似文献
106.
107.
A. Gonzalez del Campo P. Cañizares J. Lobato M.A. Rodrigo F.J. Fernandez 《International Journal of Hydrogen Energy》2012
In this work, the potential application of bio-hydrogen in a fuel cell was studied. To do that an activated sludge was acclimatized to an acidogenic culture producing bio-hydrogen. Once reached the steady state, several batch experiments were carried out by feeding a synthetic fruit juice industry wastewater to the acidogenic culture. The bio-hydrogen yield obtained when this synthetic fruit juice industry wastewater was fed was 1403 mol H2/mol hexose and the hydrogen percent in gas phase was 57%. In an average size fruit juice industry, this bio-hydrogen yield corresponds to a bio-hydrogen production of about 6000 mol H2/d. In the subsequent stage, a synthetic bio-hydrogen stream with the same composition of the cleaned bio-hydrogen obtained in the acidogenic fermentation was fed as fuel in a Fuel Cell, obtaining very similar power and polarization curves than that obtained when feeding pure hydrogen, differences lower than 10%. These results showed that the hydrogen stream obtained by the acidogenic fermentation could be used to produce electricity in a high temperature PEMFC. 相似文献
108.
María del Pilar Monge Alejandra Paola Magnoli Maria Virginia Bergesio Nestor Tancredi Carina E. Magnoli 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2016,33(6):1043-1052
Aflatoxin B1 (AFB1) and fumonisin B1 (FB1) are mycotoxins that often co-occur in feedstuffs. The ingestion of AFB1 causes aflatoxicosis in humans and animals. Sodium bentonite (NaB), a cheap non-nutritive unselective sequestering agent incorporated in animal diets, can effectively prevent aflatoxicosis. Fumonisins are responsible for equine leukoencephalomalacia and porcine pulmonary oedema, and often have subclinical toxic effects in poultries. Fumonisin B1 and aflatoxin B1 are both strongly adsorbed in vitro on sodium bentonite. Co-adsorption studies, carried out with a weight ratio of FB1 to AFB1 that mimics the natural occurrence (200:1), showed that FB1 greatly decreases the in vitro ability of NaB to adsorb AFB1. The ability of two activated carbons to adsorb FB1 was also investigated. Both carbons showed high affinity for FB1. A complex behaviour of the FB1 adsorption isotherms with pH was observed. In vitro results suggest that under natural contamination levels of AFB1 and FB1, a mixture of activated carbon and sodium bentonite might be potentially useful for prevention of sub-acute aflatoxicosis. 相似文献
109.
110.
H. Y. Zhang M. A. Ebadian A. Campo 《Numerical Heat Transfer, Part A: Applications》2013,63(2):231-248
This paper reports on connective heat transfer in irregular ducts maintained under a constant wall temperature. In particular, due to the complexity of the geometry, the paper investigates in detail the fluid flow and convective heat transfer in right-triangular and semicircular ducts. The hydrodynamically fully developed flow and the developing temperature in these geometries are obtained analytically/numerically from the solution of the energy equation employing the method of lines. The energy equation is reformulated by a system of a first-order differential equation controlling the temperature along each line. It was found that reliable closed-form solutions for the temperature distribution in the thermal entrance region can be obtained utilizing 21 lines, or less, displayed in the cross-stream direction of the duct. The grid pattern chosen provides: drastic savings in computing time. Results for the thermal entry region flow heat transfer are presented in tabular and graphical forms. The representative curves illustrating the variation of bulk temperature and Nusselt numbers with pertinent parameters in the entire thermal entry region are plotted. The computed results are compared against some analytical/numerical findings reported in the literature. In all cases, satisfactory comparison is obtained. The asymptotic Nusselt numbers are 1.90, 2.25, and 2.29 for 15°, 30°, and 45° right-triangular ducts, respectively, and 6.030 for semicircular ducts 相似文献