全文获取类型
收费全文 | 392699篇 |
免费 | 20606篇 |
国内免费 | 1605篇 |
专业分类
化学 | 239021篇 |
晶体学 | 4807篇 |
力学 | 15692篇 |
综合类 | 20篇 |
数学 | 50469篇 |
物理学 | 104901篇 |
出版年
2023年 | 4556篇 |
2021年 | 4014篇 |
2020年 | 6309篇 |
2019年 | 4136篇 |
2018年 | 5383篇 |
2017年 | 3998篇 |
2016年 | 9791篇 |
2015年 | 8953篇 |
2014年 | 9550篇 |
2013年 | 19972篇 |
2012年 | 17044篇 |
2011年 | 17470篇 |
2010年 | 13174篇 |
2009年 | 12813篇 |
2008年 | 14783篇 |
2007年 | 14793篇 |
2006年 | 13960篇 |
2005年 | 16263篇 |
2004年 | 14608篇 |
2003年 | 11794篇 |
2002年 | 9946篇 |
2001年 | 10692篇 |
2000年 | 8153篇 |
1999年 | 6570篇 |
1998年 | 5294篇 |
1997年 | 5169篇 |
1996年 | 5162篇 |
1995年 | 4784篇 |
1994年 | 4523篇 |
1993年 | 4399篇 |
1992年 | 4864篇 |
1991年 | 4687篇 |
1990年 | 4383篇 |
1989年 | 4179篇 |
1988年 | 4473篇 |
1987年 | 4064篇 |
1986年 | 3956篇 |
1985年 | 5683篇 |
1984年 | 5783篇 |
1983年 | 4726篇 |
1982年 | 5129篇 |
1981年 | 5144篇 |
1980年 | 4938篇 |
1979年 | 4996篇 |
1978年 | 5016篇 |
1977年 | 5039篇 |
1976年 | 4988篇 |
1975年 | 4856篇 |
1974年 | 4721篇 |
1973年 | 4798篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Transport in Porous Media - The theme of coupling problems for adsorption, absorption and thermochemical transport in porous media is very important for engineering applications. Based on the... 相似文献
142.
143.
144.
145.
Monodisperse aqueous upconverting nanoparticles (UCNPs) were covalently immobilized on aldehyde modified cellulose paper via reduction amination to develop a luminescence resonance energy transfer (LRET)-based nucleic acid hybridization assay. This first account of covalent immobilization of UCNPs on paper for a bioassay reports an optically responsive method that is sensitive, reproducible and robust. The immobilized UCNPs were decorated with oligonucleotide probes to capture HPRT1 housekeeping gene fragments, which in turn brought reporter conjugated quantum dots (QDs) in close proximity to the UCNPs for LRET. This sandwich assay could detect unlabeled oligonucleotide target, and had a limit of detection of 13 fmol and a dynamic range spanning nearly 3 orders of magnitude. The use of QDs, which are excellent LRET acceptors, demonstrated improved sensitivity, limit of detection, dynamic range and selectivity compared to similar assays that have used molecular fluorophores as acceptors. The selectivity of the assay was attributed to the decoration of the QDs with polyethylene glycol to eliminate non-specific adsorption. The kinetics of hybridization were determined to be diffusion limited and full signal development occurred within 3 min. 相似文献
146.
Corina Andronescu Justus Masa Richard D. Tilley John J. Gooding Wolfgang Schuhmann 《Current Opinion in Electrochemistry》2021
The complex interplay of restricted mass transport leading to local accumulation or depletion of educts, intermediates, products, counterions and co-ions influences the reactions at the active sites of electrocatalysts when electrodes are rough, three-dimensionally mesoporous or nanoporous. This influence is important with regard to activity, and even more to selectivity, of electrocatalytic reactions. The underlying principles are discussed based on the growing awareness of these considerations over recent years. 相似文献
147.
Prof. Dr. Francisco Melo Leonardo Caballero Esteban Zamorano Natalia Ventura Camilo Navarro Irving Doll Prof. Dr. Pedro Zamorano Prof. Dr. Alberto Cornejo 《Chemphyschem》2021,22(6):526-532
Parkinson's disease is a neurodegenerative disorder involving a functional protein, α-synuclein, whose primary function is related to vesicle trafficking. However, α-synuclein is prone to form aggregates, and these inclusions, known as Lewy bodies, are the hallmark of Parkinson's disease. α-synuclein can alter its conformation and acquire aggregating capacity, forming aggregates containing β-sheets. This protein's pathogenic importance is based on its ability to form oligomers that impair synaptic transmission and neuronal function by increasing membrane permeability and altering homeostasis, generating a deleterious effect over cells. First, we establish that oligomers interfere with the mechanical properties of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) membrane, as demonstrated by nanoindentation curves. In contrast, nanoindentation revealed that the α-synuclein monomer's presence leads to a much more resistant lipid bilayer. Moreover, the oligomers’ interaction with cell membranes can promote lactate dehydrogenase (LDH) release, suggesting the activation of cytotoxic events. 相似文献
148.
Dr. Carla Carrera Dr. Eleonora Cavallari Dr. Giuseppe Digilio Dr. Oksana Bondar Prof. Silvio Aime Dr. Francesca Reineri 《Chemphyschem》2021,22(11):1042-1048
An efficient synthesis of vinyl-[1-13C]pyruvate has been reported, from which 13C hyperpolarized (HP) ethyl-[1-13C]pyruvate has been obtained by means of ParaHydrogen Induced Polarization (PHIP). Due to the intrinsic lability of pyruvate, which leads quickly to degradation of the reaction mixture even under mild reaction conditions, the vinyl-ester has been synthesized through the intermediacy of a more stable ketal derivative. 13C and 1H hyperpolarizations of ethyl-[1-13C]pyruvate, hydrogenated using ParaHydrogen, have been compared to those observed on the more widely used allyl-derivative. It has been demonstrated that the spin order transfer from ParaHydrogen protons to 13C, is more efficient on the ethyl than on the allyl-esterdue to the larger J-couplings involved. The main requirements needed for the biological application of this HP product have been met, i. e. an aqueous solution of the product at high concentration (40 mM) with a good 13C polarization level (4.8 %) has been obtained. The in vitro metabolic transformation of the HP ethyl-[1-13C]pyruvate, catalyzed by an esterase, has been observed. This substrate appears to be a good candidate for in vivo metabolic investigations using PHIP hyperpolarized probes. 相似文献
149.
Renny Mathew Karolina A. Uchman Lydia Gkoura Chris J. Pickard Maria Baias 《Magnetic resonance in chemistry : MRC》2020,58(11):1018-1025
A combined experimental and computational approach was used to distinguish between different polymorphs of the pharmaceutical drug aspirin. This method involves the use of ab initio random structure searching (AIRSS), a density functional theory (DFT)-based crystal structure prediction method for the high-accuracy prediction of polymorphic structures, with DFT calculations of nuclear magnetic resonance (NMR) parameters and solid-state NMR experiments at natural abundance. AIRSS was used to predict the crystal structures of form-I and form-II of aspirin. The root-mean-square deviation between experimental and calculated 1H chemical shifts was used to identify form-I as the polymorph present in the experimental sample, the selection being successful despite the large similarities between the molecular environments in the crystals of the two polymorphs. 相似文献
150.
Prof. Dr. Yoshio Teki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(5):980-996
Recently, the potential use of organic π-radicals and related spin systems has been expanded to modern technological applications. The unique excited-state dynamics of organic π-radicals can be useful to improve the stability of photochemically unstable organic compounds, make the polarization transfer applicable to information technology, and achieve effective up-conversion of interest for luminescence bioimaging, among others. Furthermore, highly luminescent stable π-radicals have been recently reported, which are especially interesting for application in organic light-emitting devices owing to their potential to provide an internal quantum efficiency of 100 %. Thus, the excited-state nature of stable π-radicals as well as the control of their excited-state spin dynamics are emerging topics both in terms of fundamental science and related technological applications. In this minireview, we focus on the excited-state dynamics of both photostable non(weakly)-luminescent and luminescent π-radicals, which are opposites of each other. In particular, we cover the following topics: 1) effective generation of high-spin photoexcited states and control of the excited-state dynamics by using non-luminescent π-radicals, 2) unique excited-state dynamics of luminescent π-radicals and radical excimers, and 3) applications utilizing excited-state dynamics of π-radicals. 相似文献