全文获取类型
收费全文 | 5277篇 |
免费 | 364篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 67篇 |
综合类 | 3篇 |
化学工业 | 1492篇 |
金属工艺 | 59篇 |
机械仪表 | 149篇 |
建筑科学 | 208篇 |
矿业工程 | 9篇 |
能源动力 | 228篇 |
轻工业 | 860篇 |
水利工程 | 67篇 |
石油天然气 | 25篇 |
无线电 | 360篇 |
一般工业技术 | 839篇 |
冶金工业 | 193篇 |
原子能技术 | 27篇 |
自动化技术 | 1064篇 |
出版年
2024年 | 13篇 |
2023年 | 57篇 |
2022年 | 193篇 |
2021年 | 248篇 |
2020年 | 161篇 |
2019年 | 187篇 |
2018年 | 225篇 |
2017年 | 195篇 |
2016年 | 248篇 |
2015年 | 187篇 |
2014年 | 255篇 |
2013年 | 456篇 |
2012年 | 364篇 |
2011年 | 434篇 |
2010年 | 284篇 |
2009年 | 321篇 |
2008年 | 292篇 |
2007年 | 250篇 |
2006年 | 202篇 |
2005年 | 164篇 |
2004年 | 144篇 |
2003年 | 110篇 |
2002年 | 112篇 |
2001年 | 51篇 |
2000年 | 44篇 |
1999年 | 38篇 |
1998年 | 60篇 |
1997年 | 37篇 |
1996年 | 37篇 |
1995年 | 33篇 |
1994年 | 32篇 |
1993年 | 27篇 |
1992年 | 19篇 |
1991年 | 20篇 |
1990年 | 19篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 16篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 18篇 |
1983年 | 8篇 |
1982年 | 10篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 4篇 |
排序方式: 共有5650条查询结果,搜索用时 15 毫秒
981.
Teodoro Carlón Allende Manuel E. Mendoza Erna Martha López Granados Luis Miguel Morales Manilla 《Water Resources Management》2009,23(12):2587-2603
Efficient natural resources management, including continental water at watershed level, requires understanding the arrangement
of landscape attributes in a region. The geographical analysis of landscape attributes is a useful approach to delineate relatively
homogeneous watersheds or regions. This research was carried out in order to evaluate the effect of land cover through time
on regionalisation modelling in the poorly-gauged Cuitzeo Lake Watershed, and to develop models to create two hydrogeographical
regionalisations for the years 1975 and 2000. The inputs required by the regionalisation methodology were integrated in a
GIS and validated before carrying out statistical regionalisation procedures (cluster analysis and PCA). GIS operations were
done in Arc View 3.2 and statistical analyses in PC-ORD. Median Euclidean distances with mean distance linkage methods were
used. A 75% of similarity was chosen as the threshold to generate regions. Importance rankings of regions were obtained using
multicriteria evaluation methods. Based on the analysis, 38 of the 52 subwatersheds belonging to the Cuitzeo Lake Watershed
were clustered; eight groups were defined in 1975 and nine in 2000. According to PCA, the strongest positive variables are
associated to morphometric, geologic, land cover and soil attributes. Fourteen subwatersheds were never clustered. Four subwatersheds
changed of cluster between 1975 and 2000. This change is explained because of rainfed agricultural parcel abandonment, and
subsequent shrubland growth. This means that the hydrogeographical regionalisation is sensitive to land cover change processes.
The methodological approach applied in this research is a low-cost and fast alternative for evaluating the impact of land
cover and land use change on hydrogeographical regionalisation; in consequence, data and information generated during the
analysis were made available to local authorities so that they can improve both water resources planning and their informational
baseline for decision making and for development of environmental policies in the Cuitzeo Lake Watershed. 相似文献
982.
Luis F. Alarcón Sergio Maturana Ignacio Schonherr 《Canadian Metallurgical Quarterly》2009,25(4):214-220
The procurement process is critical for construction companies. To improve it, many are resorting to e-marketplaces although they usually do not know exactly how much they can gain by doing so. This paper describes a study that measured the benefits of using an e-marketplace to support the procurement process of a construction company. The study included three marketplaces currently operating in Chile. However, in this paper, we focus on Iconstruye, the most important one. 70 executives and professionals from 25 construction companies randomly selected from the 89 that used this marketplace, were interviewed and asked to fill out a questionnaire. This data was validated using data from Iconstruye and from 33 suppliers. The results show that the adoption of an e-marketplace reduces turnaround time, errors, urgent orders, and irregular purchases. A more reliable procurement process directly contributes to a leaner construction process by reducing upstream variability, procurement cycle times, and the need for large inventories on site. Users also perceive an improvement in certain global indicators when using an e-marketplace. 相似文献
983.
This paper presents the results from Phase II of an experimental study on the behavior of reinforced concrete bridge columns in cold seismicly active regions. Six half-scale circular reinforced concrete columns, designed to be flexural dominated, were tested under reversed cyclic loading while subjected to temperatures ranging from ?36°C (?33°F) to 22°C (72°F). Four of the units tested were reinforced concrete filled steel tube (RCFST) columns and the other two were ordinary reinforced concrete columns. Results obtained reiterated the observations made in Phase I, which is that low temperatures cause an increase in the flexural strength and initial stiffness as well as a reduction in the spread of plasticity and displacement capacity of the column. Another important observation made was that the plastic hinge length is drastically reduced in the RCFST units compromising the displacement capacity of this type of column even at room temperature conditions. Current predictive models were revised and modified to account for the low-temperature effect. 相似文献
984.
Luis Juana Raúl Sánchez Leonor Rodríguez-Sinobas Francisco Laguna 《Canadian Metallurgical Quarterly》2009,135(2):186-199
This technical paper presents analytical expressions to estimate the probability function of head losses in any path of an on-demand branched irrigation network. They are developed for estimating the probability of pressure deficit of a given magnitude at any hydrant. They are also useful for examining the probability of a power deficit at a pumping station designed to guarantee service to a hydrant, as well as the head characteristic curve of the distribution system linked to a definite probability. All this quantified information is useful for decision making on network design and performance. The probabilities calculated with the developed expressions can be taken as complementary or alternative concepts to Clément’s classical design flow method, which is taken here as a benchmark for comparisons. Illustrative examples of network designs are presented to validate the proposed expressions. The least cost design solutions using Clément’s design flows are compared with design solutions here obtained to get the same probability of pressure deficit at the most unfavorable hydrants. The new solutions are less expensive because the flow constraint can be avoided. 相似文献
985.
Mata Jutta; Silva Marlene N.; Vieira Paulo N.; Carra?a Eliana V.; Andrade Ana M.; Coutinho Sílvia R.; Sardinha Luis B.; Teixeira Pedro J. 《Canadian Metallurgical Quarterly》2009,28(6):709
Objective: Successful weight management relies on at least two health behaviors, eating and exercise. However, little is known about their interaction on a motivational and behavioral level. Based on the Hierarchical Model of Motivation the authors examined whether exercise-specific motivation can transfer to eating regulation during a lifestyle weight control program. The authors further investigated whether general, treatment-related, and exercise motivation underlie the relation between increased exercise and improved eating regulation. Design: Overweight/obese women participated in a 1-year randomized controlled trial (N = 239). The intervention focused on promoting physical activity and internal motivation for exercise and weight loss, following Self-Determination Theory. The control group received general health education. Main Outcome Measures: General and exercise specific self-determination, eating self-regulation variables, and physical activity behavior. Results: General self-determination and more autonomous exercise motivation predicted eating self-regulation over 12 months. Additionally, general and exercise self-determination fully mediated the relation between physical activity and eating self-regulation. Conclusion: Increased general self-determination and exercise motivation seem to facilitate improvements in eating self-regulation during weight control in women. These motivational mechanisms also underlie the relationship between improvements in exercise behavior and eating regulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
986.
An oxadiazon-degrading bacterial, Pseudomonas strain CG5, was isolated from an agricultural contaminated soil. This strain CG5 was able to grow on 10mg of oxadiazon per l, yielding 5.18+/-0.2 mg of protein biomass mol(-1). GC-MS analyses of the metabolites from oxadiazon catabolism revealed its dehalogenation and degradation to form non-toxic end-products, cells were then immobilized by adsorption on a ceramic support to be used as biocatalysts in herbicide removal biofilm-reactor processes. Seventy-two per cent of the oxadiazon was removed, and the maximum specific substrate uptake rate was 10.63+/-0.5 microg h(-1) mg(-1) prot. A new mathematical model was developed to interpret and predict the behaviour of the bacteria and pollutants in a biofilm-reactor system, to consider biofilm structural and morphological properties. 相似文献
987.
Fernando Fungo Luis A. Otero Leonides Sereno Juana J. Silber Edgardo N. Durantini 《Dyes and Pigments》2001,50(3):163-170
A convenient procedure for the synthesis of a new porphyrin–C60 dyad via the reaction between 5-(4-aminophenyl)-10,15,20-tris(4-methoxyphenyl) porphyrin and a C60 carboxylic acid is described. The results of preliminary photoelectrochemical studies on nanostructured SnO2 electrodes coated with the new dyad suggest that the resultant substrate is suitable for solar energy conversion devices. 相似文献
988.
Luis Martínez Irene Cilla José Antonio Beltrán Pedro Roncalés 《Journal of food science》2006,71(1):S48-S53
ABSTRACT Capsicum annuum (red sweet and hot cayenne) and Piper nigrum (black and white) pepper powders were evaluated for inhibition of oxidative reactions and extension of the shelf life of fresh pork sausages packaged in a modified atmosphere. Sausages containing either red sweet pepper or cayenne pepper (0.1%, 0.5%, or 2%) or black or white pepper (0.1%, 0.5%, or 1%) were packaged in a modified atmosphere of 80% O2+ 20% CO2, stored for 16 d in the dark at 2 °C, and analyzed each 4 d for pH, CIE L*, a*, and b*, 2‐thiobarbituric acid‐reactive substances (TBARS), psychrotrophic aerobes, sensory discoloration, and off‐odor. Results demonstrated that Capsicum peppers (sweet red and hot cayenne) enhanced red color but failed to prevent discoloration, whereas they were very effective in inhibiting lipid oxidation, chiefly at the highest concentration used (2%), which resulted in a delay of off‐odor formation. Piper peppers (black and white) significantly delayed discoloration with small modification of sausage color; furthermore, they also inhibited lipid oxidation, which led to a delay of off‐odor formation, particularly in the form of black pepper. Besides this, all those spices inhibited microbial growth when added at the highest concentration (1%Piper and 2%Capsicum). 相似文献
989.
Carlos Rivas-Costa Luis Anido-Rifón Miguel A. Gómez-Carballa Sonia Valladares-Rodríguez Roberto Soto-Barreiros 《International journal of human-computer interaction》2014,30(6):480-494
This article discusses a modular, accessible platform that provides a computing environment for people with disabilities accessible through adapted control devices and the television set at users’ homes. Relying on a standard television set as the presentation device allows dependent individuals, especially people with disabilities, to introduce new technological advances in communication and information management in their everyday lives. As a proof-of-concept, the solution presented offers a collection of educational and training services related to teleworking and the search of employment targeted to people with disabilities. A smart job advisor included among these services, which was designed to help our target users to locate job offers that best suit the abilities and disabilities of a particular individual, is also discussed to illustrate how semantic technologies can be applied to increase the perceived accessibility and inclusion by reducing the dependence from other persons. The platform developed, the introduction of semantic technologies, and the way adapted interfacing and presentation devices were integrated may also serve as inspiration to provide services to people with disabilities. 相似文献
990.
Moreno R Garcia MA Puig D Pizarro L Burgeth B Weickert J 《IEEE transactions on pattern analysis and machine intelligence》2011,33(11):2215-2228
This paper proposes two alternative formulations to reduce the high computational complexity of tensor voting, a robust perceptual grouping technique used to extract salient information from noisy data. The first scheme consists of numerical approximations of the votes, which have been derived from an in-depth analysis of the plate and ball voting processes. The second scheme simplifies the formulation while keeping the same perceptual meaning of the original tensor voting: The stick tensor voting and the stick component of the plate tensor voting must reinforce surfaceness, the plate components of both the plate and ball tensor voting must boost curveness, whereas junctionness must be strengthened by the ball component of the ball tensor voting. Two new parameters have been proposed for the second formulation in order to control the potentially conflictive influence of the stick component of the plate vote and the ball component of the ball vote. Results show that the proposed formulations can be used in applications where efficiency is an issue since they have a complexity of order O(1). Moreover, the second proposed formulation has been shown to be more appropriate than the original tensor voting for estimating saliencies by appropriately setting the two new parameters. 相似文献