全文获取类型
收费全文 | 1256篇 |
免费 | 51篇 |
国内免费 | 1篇 |
专业分类
化学 | 830篇 |
晶体学 | 21篇 |
力学 | 33篇 |
数学 | 156篇 |
物理学 | 268篇 |
出版年
2023年 | 14篇 |
2022年 | 14篇 |
2021年 | 15篇 |
2020年 | 20篇 |
2019年 | 37篇 |
2018年 | 40篇 |
2017年 | 45篇 |
2016年 | 95篇 |
2015年 | 55篇 |
2014年 | 79篇 |
2013年 | 103篇 |
2012年 | 68篇 |
2011年 | 91篇 |
2010年 | 66篇 |
2009年 | 62篇 |
2008年 | 56篇 |
2007年 | 47篇 |
2006年 | 43篇 |
2005年 | 20篇 |
2004年 | 41篇 |
2003年 | 32篇 |
2002年 | 12篇 |
2001年 | 15篇 |
2000年 | 16篇 |
1999年 | 16篇 |
1998年 | 15篇 |
1997年 | 16篇 |
1996年 | 8篇 |
1995年 | 19篇 |
1994年 | 6篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 13篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1976年 | 3篇 |
1975年 | 5篇 |
1974年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有1308条查询结果,搜索用时 62 毫秒
1.
Michnik Anna Kiełboń Agnieszka Duch Klaudia Sadowska-Krępa Ewa Pokora Ilona 《Journal of Thermal Analysis and Calorimetry》2022,147(12):6739-6743
Journal of Thermal Analysis and Calorimetry - The results of studies of physiological fluids by differential scanning calorimetry (DSC) for the purpose of diagnosis and monitoring of diseases are... 相似文献
2.
Scandium and its compounds are used in many modern industrial fields due to its unique chemical and physical properties. It is mainly recovered from residues and wastes in the production of other metals. The exploitation of the ores and wastes could contaminate water and soil creating environmental problems. This paper discusses recent developments and tendencies in scandium separation, purification and preconcentration from different wastes, residues, environmental samples as well as in the production of radiopharmaceuticals for nuclear medicine, both in the laboratory and on the industrial scale. The period reviewed here mainly includes publications that have appeared, since 2010. 相似文献
3.
Majchrzak-Kucęba Izabela Ściubidło Aleksandra 《Journal of Thermal Analysis and Calorimetry》2019,138(6):4139-4144
Journal of Thermal Analysis and Calorimetry - The paper presents the effect of the tabletting pressure and time on the chemical structure and crystallinity of the CuBTC and MIL-53(Al)... 相似文献
4.
Kiran Ramesh Kenneth Granlund Michael V. Ol Ashok Gopalarathnam Jack R. Edwards 《Theoretical and Computational Fluid Dynamics》2018,32(2):109-136
A leading-edge suction parameter (LESP) that is derived from potential flow theory as a measure of suction at the airfoil leading edge is used to study initiation of leading-edge vortex (LEV) formation in this article. The LESP hypothesis is presented, which states that LEV formation in unsteady flows for specified airfoil shape and Reynolds number occurs at a critical constant value of LESP, regardless of motion kinematics. This hypothesis is tested and validated against a large set of data from CFD and experimental studies of flows with LEV formation. The hypothesis is seen to hold except in cases with slow-rate kinematics which evince significant trailing-edge separation (which refers here to separation leading to reversed flow on the aft portion of the upper surface), thereby establishing the envelope of validity. The implication is that the critical LESP value for an airfoil–Reynolds number combination may be calibrated using CFD or experiment for just one motion and then employed to predict LEV initiation for any other (fast-rate) motion. It is also shown that the LESP concept may be used in an inverse mode to generate motion kinematics that would either prevent LEV formation or trigger the same as per aerodynamic requirements. 相似文献
5.
6.
Bis(N‐Confused Porphyrin) as a Semirigid Receptor with a Chirality Memory: A Two‐Way Host Enantiomerization through Point‐to‐Axial Chirality Transfer 下载免费PDF全文
Prof. Piotr J. Chmielewski Dr. Marta Siczek Prof. Marcin Stępień 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(6):2547-2559
The adduct formation of protonated bis(N‐confused porphyrin) (BNCP, 3,3′‐bis(meso‐tetratolyl‐2‐aza‐21‐carbaporphyrin) with chiral anions, carboxylic acids, and alcohols was studied in solution by means of 1H NMR and circular dichroism (CD) spectroscopic analysis and DFT methods. The addition of enantiopure guests to the acidified BNCP resulted in optical activity that vanished after neutralization. Pairs of the 1H NMR‐distinguishable diastereomers were formed when enantiopure guests were applied, although a single form was observed upon the addition of the racemic mixtures in each case. Unidirectional configuration change that led to diastereomeric excess was observed in several instances. Such an excess was memorized by metalation of the adducts with AgBF4, thus resulting in optically active silver(III) complexes of BNCP with some enantiomeric excess. Absolute configurations of BNCP cations and bis(zinc) and bis(silver(III)) complexes were determined on the basis of time‐dependent (TD)‐DFT calculations of their CD spectra. It was shown that some of the chiral carboxylates induced opposite directions of enantiomerization of di‐ and tetracations or di‐/tetracation and bis(zinc) complexes. The source of the optical activity of the equimolar diastereomeric mixture of adducts is discussed. 相似文献
7.
Exfoliated graphite (EG) was modified by a two-stage process consisting of electrochemical oxidation followed by the thermal treatment. Within the former one, the process of re-intercalation of H2SO4 into the EG by linear sweep voltammetry was carried out. Thus, obtained re-intercalated EG underwent heat treatment at 800 °C in order to synthesize re-exfoliated EG (re-EG). The electrochemical features of the re-EG were examined in the model process of phenol electrooxidation carried out by cyclic voltammetry technique in alkaline solution with and without phenol addition. Taking into account the anodic charges as a main criterion of electrochemical activity, it was found that the modification of EG caused over twofold improvement of its electrochemical activity. This behavior is related with the changes within the chemical composition of modified EG surface and on much smaller scale with the modification of its structure. The degree of electrochemical activity improvement depends on the conditions under which the processes of re-intercalation and re-exfoliation were performed. The results of Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis supported by the data of the Brunauer-Emmett-Teller (BET) surface area and scanning electron microscope (SEM) observations allow an understanding of the physicochemical properties of re-exfoliated EG and enhancement of its electrochemical activity. 相似文献
8.
Drożdż Ewa Stachura Małgorzata Wyrwa Jan Rękas Mieczysław 《Journal of Thermal Analysis and Calorimetry》2015,120(1):157-166
Journal of Thermal Analysis and Calorimetry - Tetragonal zirconia (3YSZ) and cermet nickel–tetragonal zirconia (Ni/3YSZ) were obtained by citric method. The porosity of samples was increased... 相似文献
9.