全文获取类型
收费全文 | 359457篇 |
免费 | 12749篇 |
国内免费 | 6657篇 |
专业分类
化学 | 203758篇 |
晶体学 | 4220篇 |
力学 | 15840篇 |
综合类 | 335篇 |
数学 | 42057篇 |
物理学 | 112653篇 |
出版年
2021年 | 3537篇 |
2020年 | 4154篇 |
2019年 | 3987篇 |
2018年 | 3680篇 |
2017年 | 3561篇 |
2016年 | 6296篇 |
2015年 | 5681篇 |
2014年 | 7327篇 |
2013年 | 17677篇 |
2012年 | 15276篇 |
2011年 | 17898篇 |
2010年 | 11429篇 |
2009年 | 11214篇 |
2008年 | 15498篇 |
2007年 | 15327篇 |
2006年 | 14691篇 |
2005年 | 13287篇 |
2004年 | 11637篇 |
2003年 | 10142篇 |
2002年 | 9890篇 |
2001年 | 10981篇 |
2000年 | 8541篇 |
1999年 | 7103篇 |
1998年 | 5681篇 |
1997年 | 5502篇 |
1996年 | 5527篇 |
1995年 | 4908篇 |
1994年 | 4575篇 |
1993年 | 4325篇 |
1992年 | 4706篇 |
1991年 | 4561篇 |
1990年 | 4197篇 |
1989年 | 3944篇 |
1988年 | 4188篇 |
1987年 | 3828篇 |
1986年 | 3743篇 |
1985年 | 5375篇 |
1984年 | 5406篇 |
1983年 | 4382篇 |
1982年 | 4721篇 |
1981年 | 4766篇 |
1980年 | 4493篇 |
1979年 | 4627篇 |
1978年 | 4620篇 |
1977年 | 4602篇 |
1976年 | 4577篇 |
1975年 | 4467篇 |
1974年 | 4324篇 |
1973年 | 4497篇 |
1972年 | 2546篇 |
排序方式: 共有10000条查询结果,搜索用时 600 毫秒
111.
112.
113.
114.
115.
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
116.
Zheng Yuanzhou Yang Haoran Mazaheri Hossein Aghaei Alireza Mokhtari Namjoo Afrand Masoud 《Journal of Thermal Analysis and Calorimetry》2021,143(2):1425-1438
Journal of Thermal Analysis and Calorimetry - The purpose of this study is to numerically investigate flow field and turbulent heat transfer of hybrid nanofluid, water–DWCNT–TiO2 in a... 相似文献
117.
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
118.
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
119.
Jia Yang Xingang Li Wenjun Li Xin Xi Qian Du Feng Pan Songqing Liu 《Biomedical chromatography : BMC》2020,34(8):e4857
Because of its unpredictable side effects and efficacy, the anticancer drug docetaxel (DTX) requires improved characterisation of its pharmacokinetic profiles through population pharmacokinetic studies. A sensitive and rugged LC–MS/MS method for the detection of DTX in human plasma was developed and optimised using paclitaxel as an internal standard (IS). The plasma samples underwent rapid extraction using hybrid solid-phase extraction-protein precipitation. The analyte and IS were separated with an isocratic system on a Zorbax Eclipse Plus C18 column using water containing 0.05% acetic acid along with 20 μM of sodium acetate and methanol (30/70, v/v) as the mobile phase. Quantification was performed using a triple quadrupole mass spectrometer through multiple reaction monitoring in positive mode, using the m/z 830.3 → 548.8 and m/z 876.3 → 307.7 transitions for DTX and paclitaxel, respectively. The range of the calibration curve was 1–500 ng/mL for DTX, and the linear correlation coefficient was >0.99. The accuracies ranged from −4.6 to 4.2%, and the precision was no higher than 7.0% for the analytes. No significant matrix effect was observed. Both DTX and the IS showed considerable recovery. This method was finally applied to the establishment of a population pharmacokinetic model to optimise the clinical use of DTX. 相似文献
120.
Yalda Liaghati Mobarhan Ronald Soong Daniel Lane Andre J. Simpson 《Magnetic resonance in chemistry : MRC》2020,58(5):427-444
Traditionally, due to different hardware requirements, nuclear magnetic resonance (NMR) has developed as two separate fields: one dealing with solids, and one with solutions. Comprehensive multiphase (CMP) NMR combines all electronics and hardware (magic angle spinning [MAS], gradients, high power Radio Frequency (RF) handling, lock, susceptibility matching) into a universal probe that permits a comprehensive study of all phases (i.e., liquid, gel-like, semisolid, and solid), in intact samples. When applied in vivo, it provides unique insight into the wide array of bonds in a living system from the most mobile liquids (blood, fluids) through gels (muscle, tissues) to the most rigid (exoskeleton, shell). In this tutorial, the practical aspects of in vivo CMP NMR are discussed including: handling the organisms, rotor preparation, sample spinning, water suppression, editing experiments, and finishes with a brief look at the potential of other heteronuclei (2H, 15N, 19F, 31P) for in vivo research. The tutorial is aimed as a general resource for researchers interested in developing and applying MAS-based approaches to living organisms. Although the focus here is CMP NMR, many of the approaches can be adapted (or directly applied) using conventional high-resolution magic angle spinning, and in some cases, even standard solid-state NMR probes. 相似文献