全文获取类型
收费全文 | 5952篇 |
免费 | 508篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 36篇 |
综合类 | 3篇 |
化学工业 | 1516篇 |
金属工艺 | 66篇 |
机械仪表 | 84篇 |
建筑科学 | 180篇 |
矿业工程 | 12篇 |
能源动力 | 114篇 |
轻工业 | 1351篇 |
水利工程 | 75篇 |
石油天然气 | 28篇 |
无线电 | 223篇 |
一般工业技术 | 812篇 |
冶金工业 | 1232篇 |
原子能技术 | 11篇 |
自动化技术 | 720篇 |
出版年
2024年 | 14篇 |
2023年 | 76篇 |
2022年 | 182篇 |
2021年 | 321篇 |
2020年 | 153篇 |
2019年 | 167篇 |
2018年 | 239篇 |
2017年 | 246篇 |
2016年 | 253篇 |
2015年 | 199篇 |
2014年 | 257篇 |
2013年 | 457篇 |
2012年 | 380篇 |
2011年 | 356篇 |
2010年 | 268篇 |
2009年 | 250篇 |
2008年 | 257篇 |
2007年 | 239篇 |
2006年 | 171篇 |
2005年 | 122篇 |
2004年 | 111篇 |
2003年 | 107篇 |
2002年 | 87篇 |
2001年 | 82篇 |
2000年 | 50篇 |
1999年 | 69篇 |
1998年 | 501篇 |
1997年 | 268篇 |
1996年 | 176篇 |
1995年 | 90篇 |
1994年 | 71篇 |
1993年 | 70篇 |
1992年 | 21篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 17篇 |
1986年 | 10篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 17篇 |
1973年 | 2篇 |
1960年 | 1篇 |
排序方式: 共有6463条查询结果,搜索用时 31 毫秒
91.
Maritza F. Díaz Gómez Goitybell Martínez Téllez Maikel Arteaga Cruz Rafael Garcés Mancheno 《Journal of the American Oil Chemists' Society》2006,83(11):943-946
Ozonized theobroma fat is used as raw material in the manufacture of pessaries and cosmetic creams. Ozonization of theobroma
fat with water was carried out at different applied ozone dosages, and the resultant PV, acid value, iodine value, total hydroperoxide
content, and FA content were determined. PV and total hydroperoxide content showed a notable increase with applied ozone dosage
up to 35.7 mg/g. Acid value varied slightly from 4.1 to 9.9 mg KOH/g, and the iodine value fell to zero. PV and total hydroperoxide
content increased slightly with a higher applied ozone dosage. The comparison of total hydroperoxide measurement using ferrous
oxidation in xylenol orange assay and traditional iodometric assay for PV determination showed a significant linear correlation.
Small amounts of oleic acid were found in ozonized theobroma fat samples with iodine value equaling zero, which demonstrated
that iodine value determination is an inexact assay. During ozonization of theobroma fat, an increase in acid value of 18.9-fold
with respect to the initial value was observed owing to decomposition of peroxide. 相似文献
92.
Software development is a fast-paced environment where developers need constant update to ever-changing technologies. Furthermore, process improvement initiatives have been proven useful in increasing the productivity of a software organization. As such, these organizations need to decide where to invest their training budget. As a result, training in technological update to their workforce or training in process conformance with its productive processes become conflicting alternatives. This paper presents a system dynamics simulation of a software factory product line. The objective of this simulation is to understand the changes in behavior when selecting either one of the above-training alternatives. The system dynamics model was validated with an expert panel, and the simulation results have been empirically validated—using statistical process control—against the performance baseline of a real software development organization. With the simulation under statistical control and performing like the baseline, the independent variables representing process conformance (process training) and technology skills (skills training) were modified to study their impact on product defects and process stability. Our results show that while both variables have positive impact on defects and process stability, investment in process training results in a process with less variation and with fewer defects. 相似文献
93.
Most Unified Modeling Language (UML) computer-aided software engineering tools have been insufficient in the development process because they provide little support for conceptual model testing. Model testing aims to ensure the correctness of a UML/OCL class diagram, or, in other words, that a given class diagram can perfectly meet the user’s requirements. This study proposes the validation of class diagrams with black-box testing, a technique used to test software without focusing on the software’s implementation or structure. An approach is proposed for the automatic transformation of the constraints of a UML/OCL class diagram into test cases. Following the creation of the test cases, they are executed with JUnit and the results produced are shown to the tester. To demonstrate the applicability of this approach, an effectiveness evaluation and an efficiency evaluation are performed here. Evaluation studies show that all faults included in a class diagram have been detected within an efficient time. 相似文献
94.
95.
Pedro Luis Mateo Navarro Gregorio Martínez Pérez Diego Sevilla Ruiz 《International journal of human-computer interaction》2014,30(12):946-964
This article describes a novel approach to model the quality of experience (QoE) of users in mobile environments. The context-aware and ratings interaction model (CARIM) addresses the open questions of how to quantify user experiences from the analysis of interaction in mobile scenarios, and how to compare different QoE records to each other. A set of parameters are used to dynamically describe the interaction between the user and the system, the context in which it is performed and the perceived quality of users. CARIM structures these parameters into a uniform representation, supporting the dynamic analysis of interaction to determine QoE of users and enabling the comparison between different interaction records. Its run-time nature allows applications to make context- and QoE-based decisions in real time to adapt themselves, and thus provide a better experience to users. As a result, CARIM provides unified criteria for the inference and analysis of QoE in mobile scenarios. Its design and implementation can be integrated (and easily extended if needed) into many different development environments. An experiment with real users comparing two different interaction designs and validating user behavior hypotheses proved the effectiveness of applying CARIM for the assessment of QoE in mobile applications. 相似文献
96.
This retrospective analysis was conducted between May 1997 and May 2000 at the Centro de Atención Nutricional Infantil de Antímano, CANIA, in Caracas, Venezuela to assess the efficacy of two treatments (ambulatory versus day-care) of mild and moderate malnourished children. Inclusion criteria were: children under 10 years old with mild and moderate malnourishment, who attended a minimum of 3 control visits during a period of 12 months. One hundred fourteen malnourished children were included: fifty seven in ambulatory treatment and fifty seven in day-care treatment paired per nutritional diagnosis, gender and age (thirty nine mild and eighteen moderate malnourished children). The nutritional recovery criterion was weight for height above tenth percentile. No relation was found between treatment approaches and nutritional recovery at 3 and 6 months of treatment. In the group of mild malnourished children, the percentage of recovered patients at 3 months of treatment, that kept their recovered condition at 6 months was 83% (15/18) in the ambulatory treatment and 82% (18/22) in the day-care treatment Age of children, associated disease, acute morbidity, dietetic risk and mother's education and age were not associated with nutritional recovery at 6 months of treatment (p > 0.05). The day-care approach resulted as effective as ambulatory in mild malnourished children. In moderate malnourished new studies will need to be conducted with greater number of patients. 相似文献
97.
Mejía-Centeno Isidro Martínez-Hernández Angel Fuentes Gustavo A. 《Topics in Catalysis》2007,42(1-4):381-385
The use of low-sulfur fuel is known to improve the performance of the three-way catalytic converter (TWC). However, in this
work we report how low-sulfur operation of commercial TWC also favors formation of N2O and NH3 as by products. We found that low-sulfur rich operation above 300 °C increases the production of NH3, inhibiting the formation of N2O characteristic of high-sulfur operation. During lean operation, the production of N2O near the stoichiometric point is not significantly affected by the sulfur level. The large production of N2O observed during light-off is not affected by SO2 when the operation is lean, but under rich conditions N2O is produced up to 575 °C. The increased production of NH3 and N2O in TWC as a result of the introduction of low-sulfur gasoline is an area that requires further analysis because of its implication
upon public health in large urban settings. 相似文献
98.
Witold Brostow Ligia Gargallo Andrea Hormazabal Magdalena Jaklewicz Kevin P Menard Alejandra Opazo Deodato Radic 《Polymer International》2004,53(4):460-464
We have studied blends of a polymer liquid crystal (PLC) with poly(cyclohexylethyl methacrylate) (PCHEMA) or poly(cyclohexylpropyl methacrylate) (PCHPMA). The PLC is PET/0.6PHB where PET = poly(ethylene terephthalate), PHB = p-hydroxybenzoic acid and 0.6 is the mole fraction of the latter in the copolymer. The microstructure was studied by scanning electron microscopy (SEM). PCHEMA + PLC (20 wt% of the latter, blend E) has a fine texture with LC islands evenly distributed in the matrix and good adhesion between the phases resulting from their partial miscibility. The PCHPMA + PLC (20 wt% of the latter, blend P) shows only limited compatibility. The SEM results are confirmed by values of the glass transition temperatures Tg determined via thermal mechanical analysis. The Tg value of the blend E is shifted towards the Tg of PLC; Tg of blend P is practically equal to that of PCHPMA. The linear isobaric expansivity αL values for both blends are lower than the respective values for pure PCHPMA and PCHEMA. Thermal stabilities of the blends determined by thermogravimetry are also better than those of pure polymethacrylates. The temperature of 50% weight degradation for blend E is higher than that for pure PCHEMA by more than 60 K Copyright © 2004 Society of Chemical Industry 相似文献
99.
Water Resources Management - This paper presents a case study conducted in the Upper Argos River, in southeast Spain, to verify the applicability of the SWAT model for prediction of the water... 相似文献
100.
Maximina Romero María Isabel Martín Luisa Barbieri Fernanda Andreola Isabella Lancellotti Aurora López-Delgado 《Journal of the American Ceramic Society》2021,104(2):776-784
This work reports the results of an investigation aimed at the development of sintered glass-ceramic tiles by the sinter-crystallization of mixtures composed of aluminum slag and reclaimed packaging glass. The thermal behaviors of mixtures incorporating 50 and 60 wt% Al slag were established by differential thermal analysis (DTA). Green compacts were sintered in a temperature range of 800°C-1050°C and then soaked for 10-60 minutes. The mineralogical characterizations of the sintered materials were obtained by X-ray diffraction (XRD). The achieved results indicated that the sintering of aluminum slag and packaging glass reclaimed led to a glass-ceramic material composed mainly of needle-like crystals of wollastonite (CaSiO3). The bloating of samples during firing was evaluated according to a Cougny predictive diagram. After initial observations and according to bending strength characterizations, sintered tiles prepared from aluminum slag and glassy sand are appropriate for floor pavement and wall covering. 相似文献