全文获取类型
收费全文 | 2341篇 |
免费 | 160篇 |
国内免费 | 2篇 |
学科分类
工业技术 | 2503篇 |
出版年
2024年 | 3篇 |
2023年 | 20篇 |
2022年 | 18篇 |
2021年 | 73篇 |
2020年 | 53篇 |
2019年 | 76篇 |
2018年 | 86篇 |
2017年 | 85篇 |
2016年 | 91篇 |
2015年 | 75篇 |
2014年 | 119篇 |
2013年 | 162篇 |
2012年 | 155篇 |
2011年 | 156篇 |
2010年 | 131篇 |
2009年 | 136篇 |
2008年 | 129篇 |
2007年 | 117篇 |
2006年 | 93篇 |
2005年 | 72篇 |
2004年 | 65篇 |
2003年 | 66篇 |
2002年 | 61篇 |
2001年 | 24篇 |
2000年 | 32篇 |
1999年 | 30篇 |
1998年 | 80篇 |
1997年 | 48篇 |
1996年 | 32篇 |
1995年 | 30篇 |
1994年 | 20篇 |
1993年 | 26篇 |
1992年 | 18篇 |
1991年 | 17篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 3篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 9篇 |
1978年 | 3篇 |
1976年 | 10篇 |
1975年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有2503条查询结果,搜索用时 109 毫秒
31.
Mortality due to lung, laryngeal and bladder cancer in towns lying in the vicinity of combustion installations 总被引:1,自引:0,他引:1
Javier García-Pérez Marina Pollán Elena Boldo Beatriz Pérez-Gómez Nuria Aragonés Virginia Lope Rebeca Ramis Enrique Vidal Gonzalo López-Abente 《The Science of the total environment》2009,407(8):2593-2602
Background
Installations that burn fossil fuels to generate power may represent a health problem due to the toxic substances which they release into the environment.Objectives
To investigate whether there might be excess mortality due to tumors of lung, larynx and bladder in the population residing near Spanish combustion installations included in the European Pollutant Emission Register.Methods
Ecologic study designed to model sex-specific standardized mortality ratios for the above three tumors in Spanish towns, over the period 1994-2003. Population exposure to pollution was estimated on the basis of distance from town of residence to pollution source. Using mixed Poisson regression models, we analyzed: risk of dying from cancer in a 5-kilometer zone around installations that commenced operations before 1990; effect of type of fuel used; and risk gradient within a 50-kilometer radius of such installations.Results
Excess mortality (relative risk, 95% confidence interval) was detected in the vicinity of pre-1990 installations for lung cancer (1.066, 1.041-1.091 in the overall population; 1.084, 1.057-1.111 in men), and laryngeal cancer among men (1.067, 0.992-1.148). Lung cancer displayed excess mortality for all types of fuel used, whereas in laryngeal and bladder cancer, the excess was associated with coal-fired industries. There was a risk gradient effect in the proximity of a number of installations.Conclusions
Our results could support the hypothesis of an association between risk of lung, laryngeal and bladder cancer mortality and proximity to Spanish combustion installations. 相似文献32.
Potential dermal exposure to deltamethrin and risk assessment for manual sprayers: influence of crop type 总被引:1,自引:0,他引:1
Hughes EA Flores AP Ramos LM Zalts A Richard Glass C Montserrat JM 《The Science of the total environment》2008,391(1):34-40
A comparison of the Potential Dermal Exposure (PDE) of workers to the insecticide deltamethrin was made as a function of crop type, in small agricultural production units in Argentina. Seven experiments were done with two different crops (maize and broccoli, treated area between 600 and 1000 m(2)) with three different operators under typical field conditions using a lever operated knapsack. The methodology is based on the whole body dosimetry technique, presenting separately the data for mixing/loading and application activities. These results indicate a higher concentration of pesticide in lower body sections for broccoli and a wider distribution for maize. The risk inherent in these agricultural procedures is estimated through Margin of Safety (MOS) values and was found to be generally safe. Preliminary results of a mass balance distribution of the pesticide between crop, soil and operator are also presented. 相似文献
33.
Jesús Enrique Sosa-Márquez Lorena Zamarrón-Montes Sion Federico Olive-Méndez Francisco Espinosa-Magaña 《Journal of the American Ceramic Society》2022,105(9):5956-5965
Pure and Mn-doped lithium tantalate nanofibers, with Mn concentrations of 1%, 2.5%, and 5%, were synthesized by the electrospinning method. The morphology, microstructure, and crystal structure of as-spun and annealed composite nanofibers were characterized by scanning electron microscopy, X-ray diffraction, and transmission electron microscopy. Raman spectroscopy has shown to be a powerful tool to detect either local variations or changes of the whole structure. Position and width of one Raman line can be used as markers of a structural change. Some vibrational modes are especially associated with the site of Li or Ta ions and so, they can be affected by the introduction of dopant ions. Any damages or local changes in the microstructure can be detected by a line broadening. With the use of Raman spectroscopy, the sites where Mn ions enter the doped structures were established by recording the shift and broadening of peaks in Mn-doped structures with respect to pure lithium tantalate. Thus it was proven that Mn ions enter the Li sites for low Mn concentration and, on the other hand, for higher concentrations, the dopant substitutes Li and Ta sites. First-principles calculations were performed within the density functional theory, including lattice-dynamic calculations of the phonon modes at the zone center (Γ point), for the pure structure, to find the irreducible representation of the modes. 相似文献
34.
Enrique Alvarez‐Guerra Angel Irabien Sónia P. M. Ventura João A. P. Coutinho 《American Institute of Chemical Engineers》2014,60(10):3577-3586
Ionic liquid‐based three‐phase partitioning (ILTPP) is a promising technique to recover high‐added value proteins at the liquid–liquid interface. Its economic and environmental performance highly depends on the net ionic liquid consumption. Alternatives to maximize the fraction of ionic liquid that can be recycled are studied. It is demonstrated that the addition of extra salt, previously proposed in literature, has a very limited effect on ionic liquid recovery for relatively high protein concentrations in the feed stream, and that it may even lead to an increase of the ionic liquid losses under certain conditions. However, small additions of salt are shown to be effective and profitable from an economic point of view. Vacuum evaporation is shown to allow for the complete ionic liquid and salt recovery, reinforcing the sustainability and viability of ILTPP processes. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3577–3586, 2014 相似文献
35.
36.
A. Ontiveros-Ortega F. Vidal E. Gimenez J. M. Ibáñez 《Journal of Materials Science》2014,49(9):3550-3559
We studied the surface properties of eruptive material from Deception Island (South Shetland Islands, Antarctica). The surface free energy and zeta potential were analyzed in obsidian and pumice stones immersed in different electrolytes (NaCl, BaCl2, AlCl3, VCl2, PbCl2, CdCl2, FeCl3, and CrCl3). The results show that obsidian has a monopolar character. The value of the obsidian electron-donor component increased in the presence of heavy metals, reaching 61.0 mJ/m2 in the case of CrCl3. This means that the heavy metals transform the surface of obsidian into a hydrophilic material in almost all cases, except in the case of FeCl3, which makes the obsidian surface hydrophobic. The pH variation of the liquid phase has a significant influence on the zeta potential, not only changing its value, but also the sign of the surface electric charge. A significant result is that a variation of two in pH (between 5 and 7) changes the sign of the charge from positive to negative or vice versa, depending on the electrolyte used. In general, the presence of electrolytes changes the surface properties of solid materials and consequently the adhesion and growth of microorganisms on coastal rocks. 相似文献
37.
38.
In November 2012 the Google Scholar Metrics (GSM) journal rankings were updated, making it possible to compare bibliometric indicators in the ten languages indexed—and their stability—with the April 2012 version. The h-index and h-5 median of 1,000 journals were analysed, comparing their averages, maximum and minimum values and the correlation coefficient within rankings. The bibliometric figures grew significantly. In just seven and a half months the h-index of the journals increased by 15 % and the median h-index by 17 %. This growth was observed for all the bibliometric indicators analysed and for practically every journal. However, we found significant differences in growth rates depending on the language in which the journal is published. Moreover, the journal rankings seem to be stable between April and November, reinforcing the credibility of the data held by Google Scholar and the reliability of the GSM journal rankings, despite the uncontrolled growth of Google Scholar. Based on the findings of this study we suggest, firstly, that Google should upgrade its rankings at least semi-annually and, secondly, that the results should be displayed in each ranking proportionally to the number of journals indexed by language. 相似文献
39.
Manuel Gómez‐López Maruxa García‐Quiroga Enrique Arbones‐Maciñeira Ma Lourdes Vázquez‐Odériz Ma Angeles Romero‐Rodríguez 《International Journal of Food Science & Technology》2014,49(1):107-113
Galicia (N.W. Spain) produces 60% of Spanish kiwifruit (Actinidia deliciosa) and 5–20% of these are ‘destrío’ fruits, which do not reach market size and the appropriate form. These rejected fruits can be processed into products, thus increasing their added value. The processing of kiwifruit always includes a peeling operation, which can be performed by different systems. The most suitable conditions for caustic peeling and thermal peeling were established. Then, the two peeling systems were compared with manual peeling with the aim of selecting the best system to remove the peel of the ‘destrío’ kiwifruit. The fruits, once harvested, were stored in a cold chamber at 0 °C. Before processing or marketing kiwifruits, it is necessary to remove them from storage in cold chamber and storage at room temperature. In this study, different storage times at room temperature before peeling kiwifruits were also tested. The best system for peeling the kiwifruit was thermal peeling as this system resulted in the lowest weight loss and preserved the green colour characteristic of the kiwifruit. The best time for peeling the kiwifruit was after 8 days of storage at room temperature, after being removed from the cold chamber. 相似文献
40.
António Abreu Álvaro Rocha João Vidal de Carvalho Manuel Pérez Cota 《Telematics and Informatics》2017,34(6):861-877
This article presents the first phase of a research project whose purpose is to introduce a new form of collaboration and communication between the school and the family through an Electronic Booklet (EB). The EB was developed due to the increasing necessity of collaboration between the school and the family, promoting the teaching-learning process and educational success, supported by information and communication technologies. These conclusions and justifications were derived from a survey based in a questionnaire applied to guardians and teachers of several private and public Portuguese schools of the primary and secondary education level. Both groups – guardians and teachers stressed the importance of communication between school and family and expressed interest in the EB as a communication tool. The analysis of the survey results made possible the construction of an Electronics Booklet prototype. 相似文献