全文获取类型
| 收费全文 | 1436篇 |
| 免费 | 16篇 |
| 国内免费 | 15篇 |
专业分类
| 化学 | 1064篇 |
| 晶体学 | 19篇 |
| 力学 | 26篇 |
| 数学 | 146篇 |
| 物理学 | 212篇 |
出版年
| 2024年 | 2篇 |
| 2023年 | 20篇 |
| 2022年 | 25篇 |
| 2021年 | 29篇 |
| 2020年 | 36篇 |
| 2019年 | 46篇 |
| 2018年 | 20篇 |
| 2017年 | 28篇 |
| 2016年 | 61篇 |
| 2015年 | 51篇 |
| 2014年 | 43篇 |
| 2013年 | 75篇 |
| 2012年 | 115篇 |
| 2011年 | 120篇 |
| 2010年 | 49篇 |
| 2009年 | 52篇 |
| 2008年 | 108篇 |
| 2007年 | 90篇 |
| 2006年 | 121篇 |
| 2005年 | 88篇 |
| 2004年 | 72篇 |
| 2003年 | 49篇 |
| 2002年 | 75篇 |
| 2001年 | 12篇 |
| 2000年 | 19篇 |
| 1999年 | 8篇 |
| 1998年 | 7篇 |
| 1997年 | 11篇 |
| 1996年 | 5篇 |
| 1994年 | 4篇 |
| 1993年 | 4篇 |
| 1992年 | 3篇 |
| 1991年 | 3篇 |
| 1990年 | 2篇 |
| 1989年 | 1篇 |
| 1988年 | 2篇 |
| 1986年 | 1篇 |
| 1984年 | 1篇 |
| 1982年 | 1篇 |
| 1981年 | 1篇 |
| 1979年 | 1篇 |
| 1978年 | 1篇 |
| 1976年 | 1篇 |
| 1975年 | 3篇 |
| 1973年 | 1篇 |
排序方式： 共有1467条查询结果，搜索用时 0 毫秒
81.
In this paper the technique of subtracting out singularities is used to derive explicit and implicit product Euler schemes with order one convergence and a product trapezoidal scheme with order two convergence for a system of Volterra integral equations with a weakly singular kernel. The convergence proofs of the numerical schemes are presented; these are nonstandard since the nonlinear function involved in the integral equation system does not satisfy a global Lipschitz condition. 相似文献
82.
Sean Timothy Paul 《Advances in Mathematics》2009,221(4):1345-1363
In this paper we give new elementary proofs of basic results due to Gelfand, Kapranov, and Zelevinsky which express discriminants and results in terms of determinants of direct images of stably twisted Cayley–Koszul complexes of sheaves. 相似文献
83.
Ritashree Pal Sean C. O'Brien Prof. Michael C. Willis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(51):11710-11714
We show that readily available α-amidoaldehydes are effective substrates for intermolecular Rh-catalyzed alkyne hydroacylation reactions. The catalyst [Rh(dppe)(C6H5F)][BArF4] provides good reactivity, and allows a broad range of aldehydes and alkynes to be used as substrates, delivering α-amidoketone products. High yields and high levels of regioselectivity are achieved. The use of α-amidoaldehydes as substrates establishes that 1,4-dicarbonyl motifs can be used as controlling groups in Rh-catalyzed hydroacylation reactions. 相似文献
84.
Dr. Shuyue Zhang Will C. Hartley Dr. Mark D. Greenhalgh Dr. Sean Ng Prof. Alexandra M. Z. Slawin Prof. Andrew D. Smith 《ChemCatChem》2020,12(18):4522-4525
The generation of pyrrole- and indole-functionalized tetrasubstituted pyridines in a one-pot process from 2-(pyrrol-1-yl)acetic acid or 2-(indol-1-yl)acetic acid and α,β-unsaturated N-sulfonyl-ketimines is described. The process is proposed to operate via an isothiourea-catalyzed Michael addition-lactamization, followed by elimination of sulfinic acid and O-acylation to provide the final pyridine product. 相似文献
85.
86.
Zeus A. De los Santos Sean MacAvaney Katina Russell Christian Wolf 《Angewandte Chemie (International ed. in English)》2020,59(6):2440-2448
We have developed an optical method for accurate concentration, er, and dr analysis of amino alcohols based on a simple mix‐and‐measure workflow that is fully adaptable to multiwell plate technology and microscale analysis. The conversion of the four aminoindanol stereoisomers with salicylaldehyde to the corresponding Schiff base allows analysis of the dr based on a change in the UV maximum at 420 nm that is very different for the homo‐ and heterochiral diastereomers and of the concentration of the sample using a hypsochromic shift of another absorption band around 340 nm that is independent of the analyte stereochemistry. Subsequent in situ formation of CuII assemblies in the absence and presence of base enables quantification of the er values for each diastereomeric pair by CD analysis. Applying a linear programming method and a parameter sweep algorithm, we determined the concentration and relative amounts of each of the four stereoisomers in 20 samples of vastly different stereoisomeric compositions with an averaged absolute percent error of 1.7 %. 相似文献
87.
88.
Jia Min Lee Sean Kang Qiang Suen Wei Long Ng Wai Cheung Ma Wai Yee Yeong 《Macromolecular bioscience》2021,21(1)
Collagen is the most abundant extracellular matrix protein that is widely used in tissue engineering (TE). There is little research done on printing pure collagen. To understand the bottlenecks in printing pure collagen, it is imperative to understand collagen from a bottom‐up approach. Here it is aimed to provide a comprehensive overview of collagen printing, where collagen assembly in vivo and the various sources of collagen available for TE application are first understood. Next, the current printing technologies and strategy for printing collagen‐based materials are highlighted. Considerations and key challenges faced in collagen printing are identified. Finally, the key research areas that would enhance the functionality of printed collagen are presented. 相似文献
89.
Timothy D. O&#x;Flynn Sean A. Hogan David F. M. Daly James A. O&#x;Mahony Noel A. McCarthy 《Molecules (Basel, Switzerland)》2021,26(10)
Soy protein isolate (SPI) powders often have poor water solubility, particularly at pH values close to neutral, which is an attribute that is an issue for its incorporation into complex nutritional systems. Therefore, the objective of this study was to improve SPI solubility while maintaining low viscosity. Thus, the intention was to examine the solubility and rheological properties of a commercial SPI powder at pH values of 2.0, 6.9, and 9.0, and determine if heat treatment at acidic or alkaline conditions might positively influence protein solubility, once re-adjusted back to pH 6.9. Adjusting the pH of SPI dispersions from pH 6.9 to 2.0 or 9.0 led to an increase in protein solubility with a concomitant increase in viscosity at 20 °C. Meanwhile, heat treatment at 90 °C significantly improved the solubility at all pH values and resulted in a decrease in viscosity in samples heated at pH 9.0. All SPI dispersions measured under low-amplitude rheological conditions showed elastic-like behaviour (i.e., G′ > G″), indicating a weak “gel-like” structure at frequencies less than 10 Hz. In summary, the physical properties of SPI can be manipulated through heat treatment under acidic or alkaline conditions when the protein subunits are dissociated, before re-adjusting to pH 6.9. 相似文献
90.
Sean McCarthy Alvin Lee Wei Jie D. Christopher Braddock Angela Serpe James D. E. T. Wilton-Ely 《Molecules (Basel, Switzerland)》2021,26(17)
The direct use in catalysis of precious metal recovery products from industrial and consumer waste is a very promising recent area of investigation. It represents a more sustainable, environmentally benign, and profitable way of managing the low abundance of precious metals, as well as encouraging new ways of exploiting their catalytic properties. This review demonstrates the feasibility and sustainability of this innovative approach, inspired by circular economy models, and aims to stimulate further research and industrial processes based on the valorisation of secondary resources of these raw materials. The overview of the use of recovered gold and palladium in catalytic processes will be complemented by critical appraisal of the recovery and reuse approaches that have been proposed. 相似文献