全文获取类型
收费全文 | 1538篇 |
免费 | 82篇 |
国内免费 | 3篇 |
专业分类
化学 | 1378篇 |
晶体学 | 7篇 |
力学 | 8篇 |
数学 | 93篇 |
物理学 | 137篇 |
出版年
2023年 | 10篇 |
2022年 | 17篇 |
2021年 | 63篇 |
2020年 | 48篇 |
2019年 | 51篇 |
2018年 | 38篇 |
2017年 | 44篇 |
2016年 | 77篇 |
2015年 | 71篇 |
2014年 | 65篇 |
2013年 | 109篇 |
2012年 | 99篇 |
2011年 | 134篇 |
2010年 | 87篇 |
2009年 | 72篇 |
2008年 | 112篇 |
2007年 | 89篇 |
2006年 | 63篇 |
2005年 | 80篇 |
2004年 | 59篇 |
2003年 | 38篇 |
2002年 | 27篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 4篇 |
1998年 | 9篇 |
1997年 | 14篇 |
1996年 | 7篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1973年 | 3篇 |
1956年 | 1篇 |
排序方式: 共有1623条查询结果,搜索用时 31 毫秒
61.
Monika Szulc Justyna Samaszko-Fiertek Rafał Ślusarz Kornelia Kowalska Artur Sikorski 《Journal of carbohydrate chemistry》2016,35(3):161-171
Solid phase peptide synthesis (SPPS) of two selected muramyl pentapeptide derivatives is described. The simplicity of removing the protecting groups via one-step deprotection and cleavage from the resin is the biggest advantage of SPPS. Using this method, two muramyl pentapeptide derivatives, D-MurN3-L-Ala-D-iGlu-L-Lys-D-Ala-D-Ser (5) and D-MurN3-L-Ala-D-iGlu-L-Lys-D-Ala-D-Ala (6), were obtained. Their chemical structures were confirmed by high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) spectroscopy. To determine the absolute configuration of the carbon atom in the side chain of the muramic acid derivative, single-crystal X-ray diffraction measurements were recorded. 相似文献
62.
A new class of stereoregular vinylene‐arylene copolymers with double‐decker silsesquioxane in the main chain 下载免费PDF全文
Michał Dutkiewicz Monika Ludwiczak Bogdan Marciniec Marek Nowicki 《Journal of polymer science. Part A, Polymer chemistry》2016,54(8):1044-1055
A synthesis of a new macromolecular class of vinylene‐arylene copolymers with double‐decker silsesquioxane in the main chain is presented. Two transition‐metal‐catalyzed processes, which is silylative‐coupling copolycondensation (SCC) and ADMET copolymerization of divinyl‐substituted double‐decker silsesquioxanes (DDSQ‐2SiVi) with selected diolefins, are reported to be highly efficient tools for the formation of stereoregular copolymers containing DDSQ‐silylene‐vinylene‐arylene units. The copolymeric products are studied in terms of their structural, thermal, and mechanical properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1044–1055 相似文献
63.
64.
65.
Sourav Adak Luke L. Daemen Monika Hartl Darrick Williams Jennifer Summerhill Heinz Nakotte 《Journal of solid state chemistry》2011,184(11):2854-2861
We present a comprehensive study of the structural properties and the thermal expansion behavior of 17 different Prussian Blue Analogs (PBAs) with compositions MII3[(M′)III(CN)6]2·nH2O and MII2[FeII(CN)6]·nH2O, where MII=Mn, Fe, Co, Ni, Cu and Zn, (M′)III=Co, Fe and n is the number of water molecules, which range from 5 to 18 for these compounds. The PBAs were synthesized via standard chemical precipitation methods, and temperature-dependent X-ray diffraction studies were performed in the temperature range between −150 °C (123 K) and room-temperature. The vast majority of the studied PBAs were found to crystallize in cubic structures of space groups Fm3?m, F4?3m and Pm3?m. The temperature dependence of the lattice parameters was taken to compute an average coefficient of linear thermal expansion in the studied temperature range. Of the 17 compounds, 9 display negative values for the average coefficient of linear thermal expansion, which can be as large as 39.7×10−6 K−1 for Co3[Co(CN)6]2·12H2O. All of the MII3[CoIII(CN)6]2·nH2O compounds show negative thermal expansion behavior, which correlates with the Irving–Williams series for metal complex stability. The thermal expansion behavior for the PBAs of the MII3[FeIII(CN)6]2·nH2O family are found to switch between positive (for M=Mn, Co, Ni) and negative (M=Cu, Zn) behavior, depending on the choice of the metal cation (M). On the other hand, all of the MII2[FeII(CN)6]·nH2O compounds show positive thermal expansion behavior. 相似文献
66.
Senthilkumar Sivaprakasam Moira Monika Schuler Adel Hama Katie-Marie Hughes Ian W. Marison 《Journal of Thermal Analysis and Calorimetry》2011,104(1):75-85
Control of bioprocesses requires reliable and robust on- or in-line monitoring tools providing real-time information on process
dynamics. Heat generation related to metabolic activity of living systems is currently gaining importance in bioprocess industry
due to its non-invasive and essentially instantaneous characteristics. This study deals with monitoring and control of pure
aerobic fed-batch cultures of three Crabtree-negative yeast strains, Kluyveromyces marxianus, Candida utilis and Pichia pastoris, based on in-line measured, metabolic heat flow signals. A high resolution biocalorimeter (BioRC1) was developed from a standard
bench-scale heat flow calorimeter (RC1). The BioRC1 was equipped with in-line (dielectric spectroscopy, pH probe and dissolved
oxygen probe) and at-line (exit gas analyser) sensors to characterise the growth behaviour of the yeast cells. Both metabolic
heat flow and biomass profiles exhibited similar behaviour proving the significance of employing heat flow signal as a key-parameter
for the system under investigation. A simple estimator for biomass concentration and specific growth rate was formulated based
on heat flow values. In order to evaluate the potential of calorimetry as a reliable and powerful process monitoring tool,
the robustness, reliability as well as the broad applicability of the developed estimators was assessed through comparison
with off-line measurement techniques and showed promising results for general applicability with a wide range of bioprocesses. 相似文献
67.
The paper deals with continuous-time nonlinear adaptive control of a continuous stirred tank reactor (CSTR). Control strategy
is based on the application of a controller consisting of a linear and a nonlinear part. The static nonlinear part is derived
as an inversion and exponential approximation of measured or simulated input-output data. Design of the dynamic linear part
is based on an approximation of nonlinear elements in the control loop by a continuous-time external linear model with directly
estimated parameters. In the control design procedure, polynomial approach with the pole assignment method was used. The nonlinear
adaptive control was tested by simulations on a nonlinear model of a CSTR with a consecutive exothermic reaction. 相似文献
68.
ABSTRACT The Langmuir monolayer is a special class of lyotropic liquid crystalline system wherein phase transition essentially depends on surface density, temperature and ion-content in the aqueous medium. The variety of surface phases can be transferred onto devices by the Langmuir–Blodgett (LB) technique. The Langmuir monolayer of pristine single-walled carbon nanotubes (SWCNTs) exhibited gas and liquid-like phases. The LB film of SWCNTs shows target surface pressure dependent interesting morphologies. The methane gas sensing using parallel alignment of SWCNTs was found to be better than that of randomly oriented SWCNTs. The SWCNTs can be functionalised chemically to enhance the ease of film processability and affinity towards analytes. These are essential parameters for the development of a sensor. In this article, we present our work on Langmuir monolayer and LB films of octadecylamine functionalised SWCNTs (ODACNTs) and its sensing application towards bio-analytes, e.g. L-aspartic acid and bovine serum albumin. The sensing performance of LB film of ODACNTs was compared with that of spin-coated films of ODACNTs. The sensing performance of LB films of ODACNTs indicated a potential platform for bio-sensing application. 相似文献
69.
Laura Köttner Dr. Monika Schildhauer Dr. Sandra Wiedbrauk Dr. Peter Mayer Prof. Dr. Henry Dube 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(47):10712-10718
The photophysical and photochemical properties of sulfoxide and sulfone derivatives of hemithioindigo photoswitches are scrutinized and compared to the unoxidized parent chromophores. Oxidation results in significantly blue-shifted absorptions and mostly reduction of photochromism while thermal stabilities of individual isomers remain largely unaltered. Effective photoswitching takes place at shorter wavelengths compared to parent hemithioindigos and high isomeric yields can be obtained reversibly in the respective photostationary states. Reversible solid-state photoswitching is observed for a twisted sulfone derivative accompanied by visible color changes. These results establish oxidized hemithioindigo photoswitches as promising and versatile tools for robust light-control of molecular behavior for a wide range of applications. 相似文献
70.
Paola Aline Amarante Borba Debora Dalla Vecchia Manoela Klüppel Riekes Rafael Nicolay Pereira Monika Piazzon Tagliari Marcos Antonio Segatto Silva Silvia Lucia Cuffini Carlos Eduardo Maduro de Campos Hellen Karine Stulzer 《Journal of Thermal Analysis and Calorimetry》2014,115(3):2507-2515
This study was performed to investigate the physical–chemical characteristics of carvedilol (CRV), complemented by compatibility studies with a great variety of pharmaceutical excipients. Thermogravimetry and differential scanning calorimetry, supported by diffuse reflectance infrared fourier transform spectroscopy (DRIFT), X-ray powder diffraction, and scanning electron microscopy (SEM) were selected as the solid-state techniques for the intended analyses. In addition, non-isothermal methods were employed to investigate kinetic data of CRV decomposition process under nitrogen and air atmospheres. CRV is characterized by an endothermic sharp event (T peak = 389.81 K and ΔH fusion of ?176.28 J g?1) and a thermal decomposition behavior in two stages, totalizing 98 % of mass loss. The CRV pattern diffraction presents prominent peaks at 2θ: 5.92°, 14.90°, 18.62°, 24.47°, and 26.30°, and the DRIFT spectrum showed the main characteristics bands for CRV chemical functional groups. The SEM photomicrographs demonstrate that CRV is characterized by irregular blocky shaped crystals. Zero order kinetics was determined by Ozawa method in both nitrogen and air atmospheres. The compatibility results showed no evidence of any incompatibility among CRV and all the excipients analyzed. 相似文献