全文获取类型
收费全文 | 613篇 |
免费 | 9篇 |
国内免费 | 3篇 |
专业分类
化学 | 394篇 |
晶体学 | 2篇 |
力学 | 23篇 |
数学 | 56篇 |
物理学 | 150篇 |
出版年
2023年 | 2篇 |
2022年 | 20篇 |
2021年 | 21篇 |
2020年 | 10篇 |
2019年 | 18篇 |
2018年 | 12篇 |
2017年 | 9篇 |
2016年 | 32篇 |
2015年 | 20篇 |
2014年 | 24篇 |
2013年 | 33篇 |
2012年 | 51篇 |
2011年 | 53篇 |
2010年 | 31篇 |
2009年 | 24篇 |
2008年 | 29篇 |
2007年 | 34篇 |
2006年 | 20篇 |
2005年 | 28篇 |
2004年 | 22篇 |
2003年 | 17篇 |
2002年 | 17篇 |
2001年 | 12篇 |
2000年 | 12篇 |
1999年 | 9篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有625条查询结果,搜索用时 15 毫秒
131.
Lyane M. Moreira E. A. Carvalho M. J. V. Bell V. Anjos A. C. Sant’Ana Ana Paula P. Alves B. Fragneaud L. A. Sena B. S. Archanjo C. A. Achete 《Journal of Thermal Analysis and Calorimetry》2013,114(2):557-564
This work focuses on the study of thermal diffusivity and physical properties of nanofluids with very low concentrations of silver or gold nanoparticles. Thermal measurements were performed by means of thermal lens spectroscopy in the dual beam configuration. Improvements of 20 and 16 % in the thermal diffusivity were observed for silver and gold nanofluids, respectively, in comparison with pure water. The estimation of the size distribution of the metallic nanoparticles was obtained through the fitting of the extinction spectra via Mie theory and images of field emission gun scanning electron microscopy. 相似文献
132.
133.
134.
A new finite element formulation designed for both compressible and nearly incompressible viscous flows is presented. The formulation combines conservative and non‐conservative dependent variables, namely, the mass–velocity (density * velocity), internal energy and pressure. The central feature of the method is the derivation of a discretized equation for pressure, where pressure contributions arising from the mass, momentum and energy balances are taken implicitly in the time discretization. The method is applied to the analysis of laminar flows governed by the Navier–Stokes equations in both compressible and nearly incompressible regimes. Numerical examples, covering a wide range of Mach number, demonstrate the robustness and versatility of the new method. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
135.
136.
137.
A procedure for the determination of trace level of copper(II) and cadmium(II) by FAAS using an on-line preconcentration system has been proposed. In this system, copper and cadmium ions were adsorbed onto a minicolumn packed with silica gel modified with niobium(V) oxide (Nb2O5-SiO2), followed by nitric acid elution in reverse mode and determination on-line by flame atomic absorption spectrometry (AAS) without interference of the matrix. Chemical and flow variables as well as concomitant ions were studied in the developed procedure. The enrichment factor for copper(II) and cadmium(II) was 34.2 and 33.0, respectively, using a preconcentration time of 2 min. The limit of detection for copper(II) and cadmium(II) was 0.4, and 0.1 μg l−1, respectively. The precision of the method, evaluated as the relative standard deviation in solutions containing 15 μg l−1 of copper and 10 μg l−1 of cadmium, by analyzing a series of seven replicates, was 1.8 and 1.6%, respectively. The accuracy was assessed through recovery experiments of certified material and water samples. 相似文献
138.
Adina Borbély Dr. Eduard Figueras Ana Martins Dr. Lizeth Bodero Dr. André Raposo Moreira Dias Dr. Paula López Rivas Dr. Arianna Pina Dr. Daniela Arosio Dr. Paola Gallinari Dr. Marcel Frese Dr. Christian Steinkühler Prof. Dr. Cesare Gennari Prof. Dr. Umberto Piarulli Prof. Dr. Norbert Sewald 《ChemistryOpen》2019,8(6):737-742
RGD-cryptophycin and isoDGR-cryptophycin conjugates were synthetized by combining peptidomimetic integrin ligands and cryptophycin, a highly potent tubulin-binding antimitotic agent across lysosomally cleavable Val-Ala or uncleavable linkers. The conjugates were able to effectively inhibit binding of biotinylated vitronectin to integrin αvβ3, showing a binding affinity in the same range as that of the free ligands. The antiproliferative activity of the novel conjugates was evaluated on human melanoma cells M21 and M21-L with different expression levels of integrin αvβ3, showing nanomolar potency of all four compounds against both cell lines. Conjugates containing uncleavable linker show reduced activity compared to the corresponding cleavable conjugates, indicating efficient intracellular drug release in the case of cryptophycin-based SMDCs. However, no significant correlation between the in vitro biological activity of the conjugates and the integrin αvβ3 expression level was observed, which is presumably due to a non-integrin-mediated uptake. This reveals the complexity of effective and selective αvβ3 integrin-mediated drug delivery. 相似文献
139.
Marcelo Moreira Britto Tânia Mara Grigolli Almeida Andrei Leitão Míriam Tereza Paz Lopes Carlos Alberto Montanari 《合成通讯》2013,43(22):3359-3369
The synthesis of ten novel mesoionic 4‐[para‐substituted (H, CH3, OCH3, NO2, Cl, Br, OH, t‐C4H9, C6H5, C4H9) phenyl‐5‐2,4‐dichlorophenyl]‐1,3‐4‐thiadiazolium‐2‐aminides, as hydrochlorides, are described. The synthesis strategy utilized the corresponding para‐substituted isothiocyanates as starting materials to obtain the thiosemicarbazides through reaction with phenylhydrazine (61–98%), which were then submitted to acylation with 2,4‐dichloro benzoyl chloride and direct cyclization to generate the desired substituted mesoionic compounds in good yields (ca. 80%). 相似文献
140.
Nogueira FH Goulart Lde P César Ida C de Campos LM Pianetti GA 《Journal of AOAC International》2011,94(4):1089-1093
A simple HPLC method for determination of mefloquine hydrochloride in tablets was developed and validated. The separation was carried out on an Xterra RP18 (250 x 4.6 mm id, 5 pm particle size) analytical column. The mobile phase was 0.05 M monobasic potassium phosphate buffer (pH 3.5)-methanol (40 + 60, v/v). The flow rate and wavelength were set to 1 mL/min and 283 nm, respectively. The method was specific for mefloquine hydrochloride in the presence of hydrolytic, oxidative, and photolytic degradation products. It was also linear, precise, accurate, and robust, being suitable for routine QC analyses and stability studies. The developed HPLC method was compared to a previously described spectrophotometric method. 相似文献