全文获取类型
收费全文 | 166篇 |
免费 | 4篇 |
国内免费 | 13篇 |
专业分类
化学 | 73篇 |
力学 | 6篇 |
数学 | 78篇 |
物理学 | 26篇 |
出版年
2023年 | 4篇 |
2022年 | 21篇 |
2021年 | 9篇 |
2020年 | 20篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 5篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 23篇 |
2012年 | 3篇 |
2011年 | 9篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 6篇 |
2007年 | 9篇 |
2006年 | 6篇 |
2005年 | 7篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1991年 | 1篇 |
排序方式: 共有183条查询结果,搜索用时 62 毫秒
71.
72.
Mariusz Mądrala Mirosław Wąsik Piotr Małoszewski 《Isotopes in environmental and health studies》2017,53(5):466-483
Environmental isotopes and hydrogeological data have been used for the construction of a conceptual model of fresh groundwater flow in the K?odzko Basin, Sudetes, Poland. The model has allowed the verification of a groundwater circulation scheme resulting from the general morphological assumptions and the recharge role to the surrounding mountains. Combined interpretation of the tritium ages and the isotopic altitude effect allowed determining the volume of water-bearing rock Vr and hydrogeological parameters of systems drained by springs and wells. Prior to the final determination of the recharge zone of individual objects, calculations were made for the thickness of the flow zone (h) and the distance from the recharge zone to the drainage point (L). The recharge areas for springs are located within a distance of 1–1.5 km and are characterized by a width of 0.75–1.65 km. The recharge area of wells is located in significantly longer distances of 2.1–12 km but yet definitely lower width. The recharge of groundwater from the Western direction seems to be obvious for all the wells and springs located westward from Nysa K?odzka River. The eastern component of the recharge appeared during the interpretation of the well in D?ugopole.Dedicated to Professor Peter Fritz on the occasion of his 80th birthday 相似文献
73.
试论“中学生理解科学探究”评价指标体系的构建 总被引:1,自引:0,他引:1
在综合国内外科学教育专家、学者对“理解科学探究”所持观点的基础上,提出了“理解科学探究”评价框架。以此为基础,结合中学生的特点,构建出中学生“理解科学探究”的评价指标体系。 相似文献
74.
Ömer Şahin Burçin Gökkurt Yasin Soylu 《International Journal of Mathematical Education in Science & Technology》2016,47(4):531-551
The aim of the study is to examine prospective mathematics teachers’ pedagogical content knowledge in terms of knowledge of understanding students and knowledge of instructional strategies which are the subcomponents of pedagogical content knowledge. The participants of this research consist of 98 prospective teachers who are studying in two universities in Turkey. The participants were selected with the purposive sampling method which is one of the non-random sampling methods. Case study method, which is based on the qualitative research approach, was used. The answers given by secondary school students to fraction-related open-ended questions in the study of Soylu and Soylu were used as the data collection tool. The obtained data were analyzed via the content analysis technique. The analyses showed that the prospective mathematics teachers’ pedagogical content knowledge on fractions was not at an adequate level in identifying and correcting students’ errors. However, it was observed that the prospective teachers experienced more difficulty in the knowledge of instructional strategies compared to the knowledge of understanding students. 相似文献
75.
Melike Yiǧit Koyunkaya 《International Journal of Mathematical Education in Science & Technology》2016,47(7):1028-1047
This study describes mathematics education graduate students’ understanding of relationships between sine and cosine of two base angles in a right triangle. To explore students’ understanding of these relationships, an elaboration of Skemp's views of instrumental and relational understanding using Tall and Vinner's concept image and concept definition was developed. Nine students volunteered to complete three paper and pencil tasks designed to elicit evidence of understanding and three students among these nine students volunteered for semi-structured interviews. As a result of fine-grained analysis of the students’ responses to the tasks, the evidence of concept image and concept definition as well as instrumental and relational understanding of trigonometric ratios was found. The unit circle and a right triangle were identified as students’ concept images, and the mnemonic was determined as their concept definition for trigonometry, specifically for trigonometric ratios. It is also suggested that students had instrumental understanding of trigonometric ratios while they were less flexible to act on trigonometric ratio tasks and had limited relational understanding. Additionally, the results indicate that graduate students’ understanding of the concept of angle mediated their understanding of trigonometry, specifically trigonometric ratios. 相似文献
76.
77.
VON SZENTPáLY László 《物理化学学报》2018,34(6):675-682
The addition of electrons to form gas-phase multiply charged anions (MCAs) normally requires sophisticated experiments or calculations.In this work, the factors stabilizing the MCAs, the maximum electron uptake of gas-phase molecules, X, and the electronic stability of MCAs XQ-, are discussed. The drawbacks encountered when applying computational and/or conceptual density functional theory (DFT) to MCAs are highlighted. We develop and test a different model based on the valence-state concept. As in DFT, the electronic energy, E(N, vex), is a continuous function of the average electron number, N, and the external potential, vex, of the nuclei. The valence-state-parabola is a second-order polynomial that allows extending E(N, vex) to dianions and higher MCAs. The model expresses the maximum electron acceptance, Qmax, and the higher electron affinities, AQ, as simple functions of the first electron affinity, A1, and the ionization energy, I, of the "ancestor" system. Thus, the maximum electron acceptance is Qmax, calc = 1 + 12A1/7(I -A1). The ground-state parabola model of the conceptual DFT yields approximately half of this value, and it is termed Qmax, GS = ${}^{1}\!\!\diagup\!\!{}_{2}\; $ + A1/(I -A1). A large variety of molecules are evaluated including fullerenes, metal clusters, super-pnictogens, super-halogens (OF3), super-alkali species (OLi3), and neutral or charged transition-metal complexes, ABmLn0/+/-. The calculated second electron affinity A2, calc = A1-(7/12)(I -A1) is linearly correlated to the literature references A2, lit with a correlation coefficient R = 0.998. A2 or A3 values are predicted for further 24 species. The appearance sizes, nap3-, of triply charged anionic clusters and fullerenes are calculated in agreement with the literature. 相似文献
78.
De La Rosa 《International Journal of Mathematical Education in Science & Technology》2013,44(2):223-228
The aim of this note is to improve the teaching of triple integrals. 相似文献
79.
An operational definition offered in this paper posits learning as a multi-dimensional and multi-phase phenomenon occurring when individuals attempt to solve what they view as a problem. To model someone's learning accordingly to the definition, it suffices to characterize a particular sequence of that person's disequilibrium-equilibrium phases in terms of products of a particular mental act, the characteristics of the mental act inferred from the products, and intellectual and psychological needs that instigate or result from these phases. The definition is illustrated by analysis of change occurring in three thinking-aloud interviews with one middle-school teacher. The interviews were about the same task: “Make up a word problem whose solution may be found by computing 4/5 divided by 2/3.” 相似文献
80.
The Process Analytical Technology initiative and multivariate process analysis, monitoring and control 总被引:1,自引:0,他引:1
Kourti T 《Analytical and bioanalytical chemistry》2006,384(5):1043-1048
Process analytical technology is an essential step forward in pharmaceutical industry. Real-time analyzers will provide timely
data on quality properties. This information combined with process data (temperatures, flow rates, pressure readings) collected
in real time can become a powerful tool for this industry, for process understanding, process and quality monitoring, abnormal
situation detection and for improving product quality and process reliability. A very important tool for this achievement
is the multivariate analysis.
Dr. Theodora Kourti is Research Manager in the McMaster Advanced Control Consortium (MACC) and Adjunct Professor in the Chemical Engineering
Department at McMaster University. She is the co-recipient of the 2003 University – Industry Synergy Award for Innovation,
given by the Natural Science & Engineering Research Council of Canada. Dr. Kourti has been working on Multivariate Statistical
Methods for Process and Product Improvement and Abnormal Situation Detection in Process Industries since 1992 and has been
involved in more than 80 major industrial applications in North America and Europe. These are either off-line or real-time
applications for batch and continuous processes, in diverse industries such as Chemicals, Pharmaceuticals, Semiconductor,
Mining, Pulp and Paper, Petrochemicals, Photographic and Steel Industry. She has published extensively in this area and has
provided training for numerous industrial practitioners. 相似文献