全文获取类型
收费全文 | 4170篇 |
免费 | 307篇 |
国内免费 | 2篇 |
学科分类
工业技术 | 4479篇 |
出版年
2024年 | 7篇 |
2023年 | 45篇 |
2022年 | 53篇 |
2021年 | 177篇 |
2020年 | 125篇 |
2019年 | 147篇 |
2018年 | 189篇 |
2017年 | 176篇 |
2016年 | 179篇 |
2015年 | 154篇 |
2014年 | 195篇 |
2013年 | 339篇 |
2012年 | 332篇 |
2011年 | 363篇 |
2010年 | 286篇 |
2009年 | 242篇 |
2008年 | 256篇 |
2007年 | 211篇 |
2006年 | 163篇 |
2005年 | 148篇 |
2004年 | 106篇 |
2003年 | 93篇 |
2002年 | 92篇 |
2001年 | 41篇 |
2000年 | 29篇 |
1999年 | 28篇 |
1998年 | 35篇 |
1997年 | 24篇 |
1996年 | 17篇 |
1995年 | 42篇 |
1994年 | 18篇 |
1993年 | 18篇 |
1992年 | 12篇 |
1991年 | 17篇 |
1990年 | 13篇 |
1989年 | 13篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1975年 | 8篇 |
1974年 | 3篇 |
排序方式: 共有4479条查询结果,搜索用时 17 毫秒
61.
It was reported recently that cellobiose 2-epimerases (CE) from various aerobic microorganisms convert lactose to epilactose in defined buffer systems. In this study, we showed that CE from 2 mesophilic microorganisms, Flavobacterium johnsoniae and Pedobacter heparinus, were capable of converting lactose to prebiotic epilactose not only in buffer but also in a complex milk system. First, the 2 enzymes were separately cloned, recombinantly expressed in Escherichia coli, and purified by column chromatography. The production of F. johnsoniae CE was carried out in a stirred-tank reactor, indicating that future upscaling is possible. The bioconversions of milk lactose were carried out at an industrially relevant low temperature of 8°C to avoid undesired microbial contaminations or chemical side reactions. Both enzymes were reasonably active at this low temperature, because of their origin from mesophilic organisms. The enzymes showed different operational stabilities over a 24-h time-course. A conversion yield of about 30 to 33% epilactose was achieved with both enzymes. No side products were detected other than epilactose. Therefore, CE may introduce an added value for particular dairy products by in situ production of the prebiotic sugar epilactose. 相似文献
62.
Ozone was used as an alternative for replacing sodium hypochlorite in the disinfection of yam nodal segments during the establishment stage for in vitro mass plant propagation. The purpose of this work was to evaluate the effect of ozone on disinfection of yam nodal segments in gaseous and aqueous phase in comparison to sodium hypochlorite. The immersion of yam nodal segments in water containing dissolved ozone with an ozone concentration of 1.0, 1.5 and 2.0 ppm during for 5 to 10 min gave the best results; 100% of yam nodal segments were free of microbial contamination. In terms of sprouting initiation (7.5 days), sprouting percentage (88%), and sprouts growth (4.81 cm), all were improved in comparison to the conventionally used sodium hypochlorite. 相似文献
63.
64.
Manuel Portugal Ferreira Cláudia Frias Pinto Fernando Ribeiro Serra 《Scientometrics》2014,98(3):1899-1922
Transaction costs theory (TCT) has long been an important conceptual lens for examining International Business (IB) phenomena and perhaps especially relevant for the study of multinational corporations, entry mode choices and location selection. In this paper we examine the extent to which TCT been used and has impacted IB research. Methodologically, we conduct a bibliometric study of the articles published on nine top journals for publishing IB-related research. We use Jean-François Hennart’s research as the key marker for TCT in IB research given that Hennart’s work has been a hallmark in the discipline. On a sample of 377 articles published between 1982 and 2010, and using the works rather than the authors as the unit of analysis, we analyze citations, co-citations and a spatial visualization of the intellectual research themes delved into. Our analyses provide insights on the influence of Hennart but more broadly of TCT on IB research over the past three decades. We conclude that the TCT has a pervasive influence on a large array of IB research and that Hennart’s work is boundary-spanning, connecting several research themes. 相似文献
65.
The Celta pig is a native breed adapted to the north of Spain and extensive production system. The objective was to study the effects of sex and crossbreeding on carcass characteristics and meat quality. Samples were taken from longissimus dorsi muscle of 52 pigs of three different groups [Celta pure breed (C), Celta crossed with Landrace (C × L) and Celta crossed with Duroc (C × D)]. 相似文献
66.
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
67.
The interaction between molten gallium and the hydrocarbon medium induced by ultrasonic energy—can gallium carbide be formed? 下载免费PDF全文
Vijay Bhooshan Kumar Manuel Monte Olivier Mathon Sakura Pascarelli Ze'ev Porat Aharon Gedanken 《Journal of the American Ceramic Society》2017,100(7):3305-3315
Ultrasonic irradiation of molten gallium in organic liquids (decane, dodecane, etc.) results in dispersion of the gallium into nanometric spheres. These were examined by several analytical methods XRD, DSC, Raman and IR spectroscopy) as well as electron microscopy (SEM, TEM) and found to be composed of Ga and C. The DSC analysis indicates that the Ga has possibly reacted with carbon, while the Raman spectrum of the product demonstrates a strong additional peak that could not be identified. This work explores the possibility that the product is gallium carbide or another gallium‐carbon complex. To investigate the nature of the product, we performed detailed extended X‐ray absorption fine structure (EXAFS) and X‐ray absorption near‐edge structure (XANES) analyses. On the basis of DSC, IR, and Raman it appear to be formation of GaC, whereas the analysis by EXAFS and XANES demonstrated that the gallium is found to be in a higher reduced state (almost metallic), supported by carbon. The question that remains open in addition to the one related to the formation of galium carbide is whether a complex structure, including oxygen contamination is involved in the layers surrounding the Ga as indicated by the EXAFS results. 相似文献
68.
Silvia Curteanu Ciprian-George Piuleac Jose J. Linares Pablo Cañizares Manuel A. Rodrigo Justo Lobato 《International Journal of Hydrogen Energy》2014
A multi-objective optimization strategy, based on stacked neural network–genetic algorithm (SNN–GA) hybrid approach, was applied to study the C/PBI content on a high temperature PEMFC performance. The operating conditions of PEMFC were correlated with power density and electrochemical active surface area for electrodes. The structure of the stack was determined in an optimal form related to the contribution of individual neural networks, after applying an interpolation based procedure. Multi-objective optimization using SNN as model and GA as solving procedure provides optimal working conditions which lead to a high PEMFC performance. Simulation results were in agreement with experimental data, both for model validation and system optimization (the C/PBI content in the range of 17–21%). 相似文献
69.
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
70.