全文获取类型
收费全文 | 1099篇 |
免费 | 109篇 |
国内免费 | 68篇 |
专业分类
化学 | 332篇 |
晶体学 | 3篇 |
力学 | 128篇 |
综合类 | 85篇 |
数学 | 279篇 |
物理学 | 449篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 28篇 |
2021年 | 32篇 |
2020年 | 31篇 |
2019年 | 26篇 |
2018年 | 34篇 |
2017年 | 75篇 |
2016年 | 68篇 |
2015年 | 62篇 |
2014年 | 74篇 |
2013年 | 84篇 |
2012年 | 55篇 |
2011年 | 54篇 |
2010年 | 49篇 |
2009年 | 52篇 |
2008年 | 60篇 |
2007年 | 59篇 |
2006年 | 34篇 |
2005年 | 46篇 |
2004年 | 54篇 |
2003年 | 39篇 |
2002年 | 35篇 |
2001年 | 27篇 |
2000年 | 21篇 |
1999年 | 32篇 |
1998年 | 18篇 |
1997年 | 21篇 |
1996年 | 18篇 |
1995年 | 12篇 |
1994年 | 13篇 |
1993年 | 14篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有1276条查询结果,搜索用时 15 毫秒
151.
152.
153.
Leonie Tickle Tim Kyng Leigh N. Wood 《International Journal of Mathematical Education in Science & Technology》2013,44(2):200-213
The role of universities in preparing students to use spreadsheet and other technical software in the financial services workplace has been investigated through surveys of university graduates, university academics, and employers. It is found that graduates are less skilled users of software than employers would like, due at least in part to a lack of structured formal training opportunities in the workplace, and a lack of targeted, coherent learning opportunities at university. The widespread and heavy use of software in the workplace means that there is significant potential for productivity gains if universities and employers address these issues. 相似文献
154.
应用因子分析模型针对不同的污染区逐一分析其污染源,应用spss软件确定主要影响因子,给各污染源确定名称.结果表明,低污染区受人类活动影响较小,在中污染区和高污染区以混合污染源为主,其中主干道路区和工业区属于较重污染,交通污染和冶炼厂、化工厂工业废气影响较为突出,建议采取有效措施减少其对土壤重金属污染. 相似文献
155.
156.
Tymofii Y. Nikolaienko Leonid A. Bulavin 《International journal of quantum chemistry》2019,119(3):e25798
We present the procedure for transforming delocalized molecular orbitals into the localized property-optimized orbitals (LPOs) designed for building the most accurate, in the Frobenius norm sense, approximation to the first-order reduced density matrix in form of the sum of localized monoatomic and diatomic terms. In this way, a decomposition of molecular properties into contributions associated with individual atoms and the pairs of atoms is obtained with the a priori known upper bound for the decomposition accuracy. Additional algorithm is proposed for obtaining the set of “the Chemist's LPOs” (CLPOs) containing a single localized orbital, with nearly double occupancy, per a pair of electrons. CLPOs form an idealized Lewis structure optimized for the closest possible reproduction of one-electron properties derived from the original many-electron wavefunction. The computational algorithms for constructing LPOs and CLPOs from a general wavefunction are presented and their implementation within the open-source freeware program JANPA ( http://janpa.sourceforge.net /) is discussed. The performance of the proposed procedures is assessed using the test set of density matrices of 33 432 small molecules obtained at both Hartree-Fock and second-order Moller-Plesset theory levels and excellent agreement with the chemist's Lewis-structure picture is found. 相似文献
157.
Open source paradigm is becoming widely accepted in scientific communities and open source hardware is finding its steady place in chemistry research. In this review article, we provide the reader with the most up‐to‐date information on open source hardware and software resources enabling the construction and utilization of an “open source capillary electrophoresis instrument”. While CE is still underused as a separation technique, it offers unique flexibility, low‐cost, and high efficiency and is particularly suitable for open source instrumental development. We overview the major parts of CE instruments, such as high voltage power supplies, detectors, data acquisition systems, and CE software resources with emphasis on availability of the open source information on the web and in the scientific literature. This review is the first of its kind, revealing accessible blueprints of most parts from which a fully functional open source CE system can be built. By collecting the extensive information on open source capillary electrophoresis in this review article, the authors aim at facilitating the dissemination of knowledge on CE within and outside the scientific community, fosters innovation and inspire other researchers to improve the shared CE blueprints. 相似文献
158.
Ronald Hesse Carsten Bundesmann Reinhard Denecke 《Surface and interface analysis : SIA》2019,51(13):1342-1350
The improvement of the software UNIFIT 2020 from an analysis processing software for photoelectron spectroscopy (XPS) only to a powerful tool for XPS, Auger electron spectroscopy (AES), X-ray absorption spectroscopy (XAS), and Raman spectroscopy requires new additional programme routines. Particularly, the implementation of the analysis of Raman spectra needs a well-working automatic spike correction. The application of the modified discrete Laplace operator method allows for a perfect localization and correction of the spikes and finally a successful peak fit of the spectra. The theoretical basis is described. Test spectra allow for the evaluation of the presented method. A comparison of the original and spike-corrected real measurements demonstrates the high quality of the method used. 相似文献
159.
Omar S. Ahmed Michal Malý Yoann Ladner Laurent Philibert Pavel Dubský Catherine Perrin 《Electrophoresis》2019,40(21):2810-2819
A simple, sensitive, specific, and cost‐effective analytical methodology was developed for the analysis of human plasma samples spiked with imatinib by CZE with on‐line UV detection in the context of Therapeutic Drug Monitoring. Several analytical conditions such as the ionic strength (I) and the pH of the BGE composed of citric acid and ε‐amino caproic acid were studied in regards of the presence of sodium chloride (NaCl) in plasma samples (1% m/v). Computer simulations (Simul software) were used to confirm the experimental results and to understand imatinib electrophoretic behavior in the presence of NaCl. Furthermore, the advantages of adding ACN to the sample containing NaCl to combine efficient protein precipitation and on‐line CZE stacking of imatinib were demonstrated. LOD and LOQ values of 48 and 191 ng/mL were obtained from plasma sample supernatant after protein precipitation with ACN, which is much lower than mean imatinib plasma level observed for patients treated by imatinib mesylate (about 1000 ng/mL). Good linearity was obtained in the concentration range 191–5000 ng/mL (R2 > 0.997). RSD of less than 1.68% and 2.60% (n = 6) for migration times and corrected peak areas, respectively, were observed at the LOQ. 相似文献
160.
The distortion/interaction activation strain (DIAS) analysis is a powerful tool for the investigation of energy barriers. However, setup and data analysis of such a calculation can be cumbersome and requires lengthy intervention of the user. We present autoDIAS, a python tool for the automated setup, performance, and data extraction of the DIAS analysis, including automated detection of fragments and relevant geometric parameters. © 2019 Wiley Periodicals, Inc. 相似文献