全文获取类型
收费全文 | 7584篇 |
免费 | 248篇 |
国内免费 | 6篇 |
专业分类
化学 | 5111篇 |
晶体学 | 37篇 |
力学 | 234篇 |
数学 | 921篇 |
物理学 | 1535篇 |
出版年
2023年 | 38篇 |
2022年 | 60篇 |
2021年 | 88篇 |
2020年 | 105篇 |
2019年 | 98篇 |
2018年 | 114篇 |
2017年 | 80篇 |
2016年 | 176篇 |
2015年 | 219篇 |
2014年 | 200篇 |
2013年 | 402篇 |
2012年 | 476篇 |
2011年 | 499篇 |
2010年 | 329篇 |
2009年 | 229篇 |
2008年 | 481篇 |
2007年 | 431篇 |
2006年 | 407篇 |
2005年 | 382篇 |
2004年 | 357篇 |
2003年 | 327篇 |
2002年 | 248篇 |
2001年 | 150篇 |
2000年 | 160篇 |
1999年 | 75篇 |
1998年 | 105篇 |
1997年 | 88篇 |
1996年 | 110篇 |
1995年 | 54篇 |
1994年 | 65篇 |
1993年 | 69篇 |
1992年 | 62篇 |
1991年 | 36篇 |
1990年 | 42篇 |
1989年 | 34篇 |
1988年 | 50篇 |
1986年 | 33篇 |
1985年 | 59篇 |
1984年 | 67篇 |
1983年 | 39篇 |
1982年 | 41篇 |
1981年 | 58篇 |
1980年 | 51篇 |
1979年 | 41篇 |
1978年 | 51篇 |
1977年 | 47篇 |
1976年 | 62篇 |
1975年 | 38篇 |
1974年 | 28篇 |
1973年 | 32篇 |
排序方式: 共有7838条查询结果,搜索用时 31 毫秒
1.
Mathieu Boiret Anna de Juan Nathalie Gorretta Yves-Michel Ginot Jean-Michel Roger 《Analytica chimica acta》2015
Raman chemical imaging provides chemical and spatial information about pharmaceutical drug product. By using resolution methods on acquired spectra, the objective is to calculate pure spectra and distribution maps of image compounds. With multivariate curve resolution-alternating least squares, constraints are used to improve the performance of the resolution and to decrease the ambiguity linked to the final solution. Non negativity and spatial local rank constraints have been identified as the most powerful constraints to be used. 相似文献
2.
This study compares the physicochemical properties of six electrolytes comprising of three salts: LiFTFSI, NaFTFSI and KFTFSI in two solvent mixtures, the binary (3EC/7EMC) and the ternary (EC/PC/3DMC). The transport properties (conductivity, viscosity) as a function of temperature and concentration were modeled using the extended Jones-Dole-Kaminsky equation, the Arrhenius model, and the Eyring theory of transition state for activated complexes. Results are discussed in terms of ionicity, solvation shell, and cross-interactions between electrolyte components. The application of the six formulated electrolytes in symmetrical activated carbon (AC)//AC supercapacitors (SCs) was characterized by cyclic voltammetry (CV), galvanostatic cycling with potential limitation (GCPL), electrochemical impedance spectroscopy (EIS) and accelerated aging. Results revealed that the geometrical flexibility of the FTFSI anion allows it to access and diffuse easily in AC whereas its counter ions (Li+, Na+ or K+) can remain trapped in porosity. However, this drawback was partially resolved by mixing LiFTFSI and KFTFSI salts in the electrolyte. 相似文献
3.
4.
5.
Photoisomerisation in Aminoazobenzene‐Substituted Ruthenium(II) Tris(bipyridine) Complexes: Influence of the Conjugation Pathway
下载免费PDF全文
![点击此处可从《Chemistry (Weinheim an der Bergstrasse, Germany)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Anissa Amar Dr. Paul Savel Dr. Huriye Akdas‐Kilig Dr. Claudine Katan Prof. Hacène Meghezzi Prof. Abdou Boucekkine Dr. Jean‐Pierre Malval Dr. Jean‐Luc Fillaut 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(22):8262-8270
Transition‐metal complexes containing stimuli‐responsive systems are attractive for applications in optical devices, photonic memory, photosensing, as well as luminescence imaging. Amongst them, photochromic metal complexes offer the possibility of combining the specific properties of the metal centre and the optical response of the photochromic group. The synthesis, the electrochemical properties and the photophysical characterisation of a series of donor–acceptor azobenzene derivatives that possess bipyridine groups connected to a 4‐dialkylaminoazobenzene moiety through various linkers are presented. DFT and TD‐DFT calculations were performed to complement the experimental findings and contribute to their interpretation. The position and nature of the linker (ethynyl, triazolyl, none) were engineered and shown to induce different electronic coupling between donor and acceptor in ligands and complexes. This in turn led to strong modulations in terms of photoisomerisation of the ligands and complexes. 相似文献
6.
Markus Bödenler Ludovic de Rochefort P. James Ross Nicolas Chanet Geneviève Guillot Gareth R. Davies 《Molecular physics》2019,117(7-8):832-848
ABSTRACTFast field-cycling (FFC) nuclear magnetic resonance relaxometry is a well-established method to determine the relaxation rates as a function of magnetic field strength. This so-called nuclear magnetic relaxation dispersion gives insight into the underlying molecular dynamics of a wide range of complex systems and has gained interest especially in the characterisation of biological tissues and diseases. The combination of FFC techniques with magnetic resonance imaging (MRI) offers a high potential for new types of image contrast more specific to pathological molecular dynamics. This article reviews the progress in FFC-MRI over the last decade and gives an overview of the hardware systems currently in operation. We discuss limitations and error correction strategies specific to FFC-MRI such as field stability and homogeneity, signal-to-noise ratio, eddy currents and acquisition time. We also report potential applications with impact in biology and medicine. Finally, we discuss the challenges and future applications in transferring the underlying molecular dynamics into novel types of image contrast by exploiting the dispersive properties of biological tissue or MRI contrast agents. 相似文献
7.
8.
9.
Tricyclic skeletons have been generated from acyclic enyne precursors by using an intramolecular Pauson-Khand reaction in combination with aldol, Michael and alkylation reactions. 相似文献
10.
Papert's (1978) appeal to reconsider the power and possibilities of the aesthetic in mathematics learning is often ignored in mathematics education research. This paper begins with the premise, put forth by Dewey (1934), that the aesthetic structures many dimensions of inquiry and experience. In the same way that using particular paintings, musical compositions, or even everyday experiences has been instrumental to attempts by philosophers to understand the aesthetic dimensions of meaning and experience in artistic domains, I propose that analysing a particular encounter with mathematics may help reveal the nature and role of the often nebulous responses of elegance, beauty, and `fit' to which mathematicians lay claim in their mathematical activity. To achieve this, I draw on and adapt the defining features of the aesthetic character of experience set forth by the aesthetician Beardsley (1982). This, in turn, sheds light on the role thataesthetics can play in mathematical inquiry and experience, and provides initial categories and conjectures that can be used to investigate the potential roles of aesthetics in mathematics learning contexts.This revised version was published online in September 2005 with corrections to the Cover Date. 相似文献