全文获取类型
收费全文 | 2304篇 |
免费 | 212篇 |
专业分类
电工技术 | 21篇 |
综合类 | 29篇 |
化学工业 | 915篇 |
金属工艺 | 25篇 |
机械仪表 | 43篇 |
建筑科学 | 98篇 |
矿业工程 | 6篇 |
能源动力 | 55篇 |
轻工业 | 388篇 |
水利工程 | 41篇 |
石油天然气 | 4篇 |
无线电 | 83篇 |
一般工业技术 | 374篇 |
冶金工业 | 126篇 |
原子能技术 | 7篇 |
自动化技术 | 301篇 |
出版年
2024年 | 15篇 |
2023年 | 22篇 |
2022年 | 124篇 |
2021年 | 177篇 |
2020年 | 96篇 |
2019年 | 85篇 |
2018年 | 91篇 |
2017年 | 96篇 |
2016年 | 112篇 |
2015年 | 94篇 |
2014年 | 126篇 |
2013年 | 177篇 |
2012年 | 140篇 |
2011年 | 203篇 |
2010年 | 119篇 |
2009年 | 119篇 |
2008年 | 127篇 |
2007年 | 98篇 |
2006年 | 70篇 |
2005年 | 50篇 |
2004年 | 46篇 |
2003年 | 49篇 |
2002年 | 43篇 |
2001年 | 25篇 |
2000年 | 29篇 |
1999年 | 28篇 |
1998年 | 29篇 |
1997年 | 14篇 |
1996年 | 10篇 |
1995年 | 15篇 |
1994年 | 16篇 |
1993年 | 13篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有2516条查询结果,搜索用时 15 毫秒
161.
Janaina I. S. Aguiar Jéssica S. G. Neto Sarah M. Almeida Claudia R. E. Mansur 《应用聚合物科学杂志》2013,128(3):1390-1397
During extraction of crude oil, water is generally present in the oil. This water‐in‐oil (w/o) mixture undergoes turbulent flow that promotes sheer forces, resulting in the appearance of emulsions. These emulsions can be highly stable due to the presence of compounds with polar characteristics such as asphaltenes, which act as natural emulsifiers and form resistant films at the oil–water interface. Nonionic surfactants based on polyoxides are widely used to prevent the formation or to break down w/o emulsions. To shed more light on the destabilization mechanism of w/o emulsions promoted by these surfactants, in this study the techniques of tensiometry and Fourier transform infrared spectroscopy with attenuated total reflectance (FTIR‐ATR) were applied to study the interface formed by poly(ethylene oxide)‐poly(propylene oxide) (PEO‐PPO) block copolymers and asphaltenic petroleum fractions. Initially, the critical micelle concentration of the copolymers in aqueous solution was determined. The results agreed with those found by tensiometry. The bottle test was used to evaluate the break‐down of the w/o emulsions in the presence of the PEO‐PPO block copolymers, and the results presented good agreement with those obtained by tensiometry and FTIR‐ATR. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
162.
Sebastian F. Fischer M.Sc. Marc Thielen Ruth R. Loprang M.Sc. Robin Seidel Claudia Fleck Thomas Speck Andreas Bührig‐Polaczek 《Advanced Engineering Materials》2010,12(12):B658-B663
Natural materials often exhibit excellent mechanical properties. An example of outstanding impact resistance is the pummelo fruit (Citrus maxima) which can drop from heights of 10 m and more without showing significant outer damage. Our data suggest that this impact resistance is due to the hierarchical organization of the fruit peel, called pericarp. The project presented in the current paper aims at transferring structural features from the pummelo pericarp to engineering materials, in our case metal foams, produced by the investment casting process. The transfer necessitates a detailed structural and mechanical analysis of the biological model on the one hand, and the identification and development of adequate materials and processes on the other hand. Based on this analysis, engineering composite foam structures are developed and processed which show enhanced damping and impact properties. The modified investment casting process and the model alloy Bi57Sn43 proved to be excellent candidates to make these bio‐inspired structures. Mechanical testing of both the natural and the engineering structures has to consider the necessity to evaluate the impact of the different hierarchical features. Therefore, specimens of largely varying sizes have to be tested and size effects cannot be ignored, especially as the engineering structures might be upscaled in comparison with the natural role model. All in all, the present results are very promising: the basis for a transfer of bio‐inspired structural hierarchical levels has been set. 相似文献
163.
In the paper, thermal use of solar energy as well as prospects and problems of its utilisation in Croatia have been given. The National Solar Energy Program, SUNEN, has been established to stimulate the usage of solar energy. The main goals of the program are the assessment of technical and economically viable solar potential in order to define real objectives and tasks to provide use of exploitable indigenous clean and renewable energy potential. The Program addresses benefits, the most promising solar applications and solar potential. Much attention has been given to identification of obstacles and barriers in the process of solar technology dissemination. SUNEN is an initiative to increase solar energy use and to become more compatible with the present renewable energy sources policy in EU and Mediterranean countries. The program proposes twelve different types of thermal solar energy systems, which could be multiplied up to 28 000 installations until the year 2010 with annual heat recovery of approximately 1,5 TWh (5,4 PJ). 相似文献
164.
165.
166.
The effects of instructional support and learner interests when learning using computer simulations 总被引:1,自引:0,他引:1
Within the scope of this study, the effectiveness of two kinds of instructional support was evaluated with regard to the learner’s interests. Two versions of a simulation program about the respiratory chain were developed, differing only in the kind of tasks provided for instructional support: One version contained problem-solving tasks, the other one contained worked-out examples. The focus was on the learner’s interest in the subject and in computers. The first goal of the study was to find to what extent computer simulations incorporating the different kinds of instructional support have positive effects on situational subject-interest. The second goal was to evaluate the interactions between the learner’s interests and the instructional support with regard to the learning results (subdivided into factual knowledge and understanding). Simulations with worked-out examples were shown to have positive effects on the learner’s situational interest in the subject. This was not found to be the case in simulations with problem-solving tasks. Regardless of the kind of instructional support, learners with little interest in the subject were able to achieve significant gains in factual knowledge. However, improvement in understanding was dependent on the kind of instructional support. 相似文献
167.
Isomerization is used in refining industry to upgrade gasoline. Since it is an important process, it is desirable to analyze the reactions that take place in the process. In this paper, the isomerization of a mixture of hydrocarbons was modeled by solving the chemical equilibrium of the system. A direct application of the chemical equilibrium solution cannot reproduce experimental results. However, when some of the system reactions are molar extent limited, the solution can reproduce published experimental data. 相似文献
168.
169.
Claudia F. Galinha Gilda Carvalho Carla A. M. Portugal Giuseppe Guglielmi Maria A. M. Reis João G. Crespo 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(7):985-992
BACKGROUND: The use of two‐dimensional (2D) fluorescence for monitoring complex biological systems requires careful assessment of the effect of chemical species present, which may be fluorescent and/or may interfere with the fluorescence response of target fluorophores. Given the complexity of fluorescence data (excitation emission matrices—EEMs), the challenge is how to recover the information embedded into those EEMs that can be related quantitatively with the observed performance of the biological processes under study. RESULTS: This work shows clearly that interference effects (such as quenching and inner filter effects) occur due to the presence of multiple species in complex biological media, such as natural water matrices, wastewaters and activated sludge. A statistical multivariate analysis is proposed to recover quantitative information from 2D fluorescence data, correlating EEMs with the observed performance. A selected case study is discussed, where 2D fluorescence spectra obtained from the effluent of a membrane bioreactor were compressed using PARAFAC and successfully correlated with the effluent chemical oxygen demand, using projection to latent structures modelling. CONCLUSION: This study demonstrates the potential of using 2D fluorescence spectroscopy as a status fingerprint. Additionally, it is shown how statistical multivariate data analysis can be used to correlate EEMs with selected performance parameters for monitoring of biological systems. Copyright © 2011 Society of Chemical Industry 相似文献
170.
Cleo Zanella Billa Jacques Wainer Claudia Barsottini 《Journal of Intelligent Information Systems》2011,36(1):49-72
This work presents the ST-Audit system that audits a patient record for conformance to a particular clinical guideline. The
system uses ST-Guide which models a guideline as a set of states and transitions. The audit system tries to find a path in
the state/transition diagram that corresponds to the actions taken by the physician, taking into consideration issues such
as the unavailability of all the data needed to evaluate the transitions. The system was used to audit an outpatient clinic
regarding their procedure for hypertension treatment (using the VI JNC guideline for hypertension), and the results of the
number of non-compliant actions were presented and discussed. A follow up auditing showed a small but statistically significant
reduction on the number of non-compliant actions for patients treated after the first audit. 相似文献