全文获取类型
收费全文 | 1170篇 |
免费 | 45篇 |
国内免费 | 8篇 |
专业分类
化学 | 928篇 |
晶体学 | 8篇 |
力学 | 12篇 |
数学 | 57篇 |
物理学 | 218篇 |
出版年
2023年 | 10篇 |
2022年 | 7篇 |
2021年 | 17篇 |
2020年 | 18篇 |
2019年 | 23篇 |
2018年 | 10篇 |
2017年 | 11篇 |
2016年 | 37篇 |
2015年 | 20篇 |
2014年 | 25篇 |
2013年 | 67篇 |
2012年 | 61篇 |
2011年 | 66篇 |
2010年 | 44篇 |
2009年 | 48篇 |
2008年 | 49篇 |
2007年 | 56篇 |
2006年 | 49篇 |
2005年 | 55篇 |
2004年 | 51篇 |
2003年 | 38篇 |
2002年 | 66篇 |
2001年 | 39篇 |
2000年 | 30篇 |
1999年 | 16篇 |
1998年 | 18篇 |
1997年 | 15篇 |
1996年 | 16篇 |
1995年 | 11篇 |
1994年 | 13篇 |
1993年 | 14篇 |
1992年 | 21篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 12篇 |
1988年 | 8篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 19篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 12篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1973年 | 7篇 |
排序方式: 共有1223条查询结果,搜索用时 843 毫秒
911.
Akira YamaguchiPeng Jin Hiroshi TsuchiyamaTakao Masuda Kai SunShigeki Matsuo Hiroaki Misawa 《Analytica chimica acta》2002,468(1):143-152
Applicability of polydimethylsiloxane (PDMS) for easy and rapid fabrication of enzyme sensor chips, based on electrochemical detection, is examined. The sensor chip consists of PDMS substrate with a microfluidic channel fabricated in it, and a glass substrate with enzyme-modified microelectrodes. The two substrates are clamped together between plastic plates. The sensor chip has shown no leakage around the microelectrodes under continuous solution flow (34 μl/min). Amperometric response of the sensor chips developed in this work suggest that various types of enzyme sensors can be designed by using PDMS microfluidic channels. 相似文献
912.
913.
914.
Aoki Nobuyuki Shimosaka Takuya Aoyagi Reiji Kaifuku Yuichiro 《Accreditation and quality assurance》2018,23(4):199-210
Accreditation and Quality Assurance - A reliable method for the quantification of formaldehyde (HCHO) amount fractions is required, because the results of comparisons between individual techniques... 相似文献
915.
Mono‐ and Bis(imidazolidinium ethynyl) Cations and Reduction of the Latter To Give an Extended Bis‐1,4‐([3]Cumulene)‐p‐carboquinoid System
下载免费PDF全文
![点击此处可从《Angewandte Chemie (International ed. in English)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Prof. Brian M. Barry R. Graeme Soper Juha Hurmalainen Akseli Mansikkamäki Dr. Katherine N. Robertson William L. McClennan Alex J. Veinot Dr. Tracey L. Roemmele Dr. Ulrike Werner‐Zwanziger Prof. René T. Boeré Prof. Heikki M. Tuononen Prof. Jason A. C. Clyburne Prof. Jason D. Masuda 《Angewandte Chemie (International ed. in English)》2018,57(3):749-754
An extended π‐system containing two [3]cumulene fragments separated by a p‐carboquinoid and stabilized by two capping N‐heterocyclic carbenes (NHCs) has been prepared. Mono‐ and bis(imidazolidinium ethynyl) cations have also been synthesized from the reaction of an NHC with phenylethynyl bromide or 1,4‐bis(bromoethynyl)benzene. Cyclic voltammetry coupled with synthetic and structural studies showed that the dication is readily reduced to a neutral, singlet bis‐1,4‐([3]cumulene)‐p‐carboquinoid as a result of the π‐accepting properties of the capping NHCs. 相似文献
916.
Yoshimichi Okano Toshio Masuda Toshinobu Higashimura 《Journal of polymer science. Part A, Polymer chemistry》1984,22(7):1603-1610
The polymerization of trimethylsilylacetylene was investigated by using W and Mo catalysts. Mixtures of WCl6 with appropriate organometallic cocatalysts such as n-Bu4Sn and Et3SiH at 1:1 molar ratio provided poly(trimethylsilylacetylene) in high yields. On the other hand, MoCI5 gave mainly methanol-soluble oligomers even in the presence of these cocatalysts. The polymer formed was a partly insoluble yellow powder, and the molecular weight of the soluble fraction was about 7000. The IR, 1H-NMR, and 13C-NMR spectra supported the polymer structure, (CH = CSiMe3)n. Protodesilylation of poly(trimethylsilylacetylene) afforded a new polymer containing both acetylene and trimethylsilylacetylene units. 相似文献
917.
Effects of Charge and Structure of Hyaluronic Acid on the Luminescence Quenching in Aqueous Solution
Thomas Kluge Akiko Masuda Koichi Yamashita Kiminori Ushida 《Photochemistry and photobiology》1998,68(5):771-775
The quenching of electronically excited Ru(bpy)32+ (bpy = Tris-2,2′-bipyridine) by methylviologen (MV) and ferricyanide (FC) in aqueous solutions of hyaluronic acid (HA) was studied. The structural and viscosity changes occuring with increasing HA concentration were found to influence the photophysical and photochemical properties of the sensitizer. Different kinetic models had to be used for the quenchers studied. The kinetics of the quenching of *Ru(bpy)32+ by MV can be described by the pseudophase model, which indicates that the rate for the exchange of the quencher between the microdroplets is higher than that for the excited state decay of the Ruthenium complex. In contrast, the quenching by the negatively charged quencher, FC, can be described by the Infelta-Tachiya equation, which indicates that the distribution of this quencher on the aqueous microdroplets is of the Poisson type and there is no exchange of quencher molecules during the lifetime of the sensitizer. The lifetimes of the excited Ruthenium complex, the unimolecular constants for its quenching by FC and the average concentration of the aqueous microdroplets increase with increasing HA concentration, reflecting the change in the solution structure during the transition from semidilute to concentrated regions. For MV no significant dependence of the quenching constant on the HA content of the solution was found. The reaction behavior of charged reactants in HA solution depends strongly on the sign of the charge. 相似文献
918.
S Uehara Y Kuwabara Y Ichiya M Otsuka Y Ayabe Y Miyake K Masuda A Yoshimura 《Radioisotopes》1987,36(12):653-656
The analysis of kinetic rate constants in the compartment model for [18F]fluorodeoxyglucose (FDG) was undertaken. Four kinetic rate constants were determined with a least square fitting package SALS (Statistical Analysis with Least Squares), using the measured data of 18F activity as a function of time. SALS calculations were found to be easy and quick with high precision. The rate constants and the curves fitted by the k3 and the k4 models were compared in situations with various degree of cerebral glucose metabolism during positron emission tomography (PET) studies. The k4 model in the determination of cerebral metabolic rate for glucose (CMRglu) was much superior than the k3 model in any given situation as it always underestimates the metabolic rate. However, the k3 model produces less variation when the cerebral radioactivity curve shows steady rising pattern. 相似文献
919.
Photosensors (PS) and membrane photosensors (MPS), which can be immersed in the test solution and facilitate the measurement of concentration, have been developed by miniaturizing an optical system consisting of a light source and a photocell. For use in acid-base or complexometric titrations a poly(vinyl chloride) membrane containing an acid-base or metallochromic indicator can be applied as a coating to the photocell. Spectrophotometric determination of copper(II), and photometric acid-base and chelatometric titrations have been performed with the PS and MPS systems. 相似文献
920.
Yamanoi Y Shirahata N Yonezawa T Terasaki N Yamamoto N Matsui Y Nishio K Masuda H Ikuhara Y Nishihara H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,12(1):314-323
The modification of flat semiconductor surfaces with nanoscale materials has been the subject of considerable interest. This paper provides detailed structural examinations of gold nanoparticles covalently immobilized onto hydrogen-terminated silicon surfaces by a convenient thermal hydrosilylation to form Si-C bonds. Gold nanoparticles stabilized by omega-alkene-1-thiols with different alkyl chain lengths (C3, C6, and C11), with average diameters of 2-3 nm and a narrow size distribution were used. The thermal hydrosilylation reactions of these nanoparticles with hydrogen-terminated Si(111) surfaces were carried out in toluene at various conditions under N2. The obtained modified surfaces were observed by high-resolution scanning electron microscopy (HR-SEM). The obtained images indicate considerable changes in morphology with reaction time, reaction temperature, as well as the length of the stabilizing omega-alkene-1-thiol molecules. These surfaces are stable and can be stored under ambient conditions for several weeks without measurable decomposition. It was also found that the aggregation of immobilized particles on a silicon surface occurred at high temperature (> 100 degrees C). Precise XPS measurements of modified surfaces were carried out by using a Au-S ligand-exchange technique. The spectrum clearly showed the existence of Si-C bonds. Cross-sectional HR-TEM images also directly indicate that the particles were covalently attached to the silicon surface through Si-C bonds. 相似文献