全文获取类型
收费全文 | 663695篇 |
免费 | 6454篇 |
国内免费 | 1674篇 |
专业分类
化学 | 344507篇 |
晶体学 | 10058篇 |
力学 | 31756篇 |
综合类 | 26篇 |
数学 | 83217篇 |
物理学 | 202259篇 |
出版年
2021年 | 5849篇 |
2020年 | 6486篇 |
2019年 | 7312篇 |
2018年 | 9552篇 |
2017年 | 9749篇 |
2016年 | 13635篇 |
2015年 | 7598篇 |
2014年 | 12659篇 |
2013年 | 29769篇 |
2012年 | 22575篇 |
2011年 | 26967篇 |
2010年 | 20013篇 |
2009年 | 19880篇 |
2008年 | 25256篇 |
2007年 | 24984篇 |
2006年 | 22882篇 |
2005年 | 20538篇 |
2004年 | 18988篇 |
2003年 | 17225篇 |
2002年 | 16957篇 |
2001年 | 18603篇 |
2000年 | 14397篇 |
1999年 | 11138篇 |
1998年 | 9448篇 |
1997年 | 9303篇 |
1996年 | 8719篇 |
1995年 | 7971篇 |
1994年 | 7878篇 |
1993年 | 7512篇 |
1992年 | 8416篇 |
1991年 | 8737篇 |
1990年 | 8437篇 |
1989年 | 8348篇 |
1988年 | 8214篇 |
1987年 | 8062篇 |
1986年 | 7691篇 |
1985年 | 9807篇 |
1984年 | 10143篇 |
1983年 | 8370篇 |
1982年 | 8710篇 |
1981年 | 8301篇 |
1980年 | 7842篇 |
1979年 | 8567篇 |
1978年 | 8825篇 |
1977年 | 8789篇 |
1976年 | 8592篇 |
1975年 | 8147篇 |
1974年 | 7957篇 |
1973年 | 8118篇 |
1972年 | 5852篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
JETP Letters - The leading role of the bremsstrahlung at resonant Compton scattering of a hard X-ray photon by a multielectron atom has been theoretically predicted. This result can be important in... 相似文献
102.
JETP Letters - At the resonant passage of a plane elastic shear wave through an acoustically continuous heterostructure consisting of magnetic and nonmagnetic layers in a symmetric nonmagnetic... 相似文献
103.
104.
Development and validation of a reversed‐phase HPLC method for CYP1A2 phenotyping by use of a caffeine metabolite ratio in saliva 下载免费PDF全文
Elias Begas Evangelos Kouvaras Andreas K. Tsakalof Maria Bounitsi Eftihia Konstadinos Asprodini 《Biomedical chromatography : BMC》2015,29(11):1657-1663
CYP1A2 is important for metabolizing various clinically used drugs. Phenotyping of CYP1A2 may prove helpful for drug individualization therapy. Several HPLC methods have been developed for quantification of caffeine metabolites in plasma and urine. Aim of the present study was to develop a valid and simple HPLC method for evaluating CYP1A2 activity during exposure in xenobiotics by the use of human saliva. Caffeine and paraxanthine were isolated from saliva by liquid‐liquid extraction (chlorophorm/isopropanol 85/15v/v). Extracts were analyzed by reversed‐phase HPLC on a C18 column with mobile phase 0.1% acetic acid/methanol/acetonitrile (80/20/2 v/v) and detected at 273nm. Caffeine and paraxanthine elution times were <13min with no interferences from impurities or caffeine metabolites. Detector response was linear (0.10–8.00µg/ml, R2>0.99), recovery was >93% and bias <4.47%. Intra‐ and inter‐day precision was <5.14% (n=6). The limit of quantitation was 0.10µg/ml and the limit of detection was 0.018±0.002µg/mL for paraxanthine and 0.032±0.002µg/ml for caffeine. Paraxanthine/caffeine ratio of 34 healthy volunteers was significantly higher in smokers (p<0.001). Saliva paraxanthine/caffeine ratios and urine metabolite ratios were highly correlated (r=0.85, p<0.001). The method can be used for the monitoring of CYP1A2 activity in clinical practice and in studies relevant to exposure to environmental and pharmacological xenobiotics. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
105.
106.
Ivanov K. A. Gubaidullin A. R. Morozov K. M. Sasin M. E. Kaliteevskii M. A. 《Optics and Spectroscopy》2019,126(6):787-787
Optics and Spectroscopy - 10.1134/S0030400X17050095 相似文献
107.
Kaplunov I. A. Kolesnikov A. I. Kropotov G. I. Rogalin V. E. 《Optics and Spectroscopy》2019,126(3):191-194
Optics and Spectroscopy - The transmission of intrinsic, antimony-doped, and gallium-doped Ge single crystals in the THz spectral range have been experimentally investigated. It is shown that the... 相似文献
108.
Dr. Liat Avram Dr. Václav Havel Ronit Shusterman-Krush Dr. Mark A. Iron Dr. Moritz Zaiss Prof. Vladimír Šindelář Dr. Amnon Bar-Shir 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(7):1687-1690
The accumulated knowledge regarding molecular architectures is based on established, reliable, and accessible analytical tools that provide robust structural and functional information on assemblies. However, both the dynamicity and low population of noncovalently interacting moieties within studied molecular systems limit the efficiency and accuracy of traditional methods. Herein, the use of a saturation transfer-based NMR approach to study the dynamic binding characteristics of an anion to a series of synthetic receptors derived from bambusuril macrocycles is demonstrated. The exchange rates of BF4− are mediated by the side chains on the receptor (100 s−1<kex<5000 s−1), which play a critical role in receptor-anion binding dynamics. The signal amplification obtained with this approach allows for the identification of different types of intermolecular interactions between the receptor and the anion, something that could not have been detected by techniques hitherto used to study molecular assemblies. These findings, which are supported by a computational molecular dynamic study, demonstrate the uniqueness and added value of this NMR method. 相似文献
109.
K. Volkan
zdokur 《Electroanalysis》2020,32(3):489-495
Copper oxide decorated multi‐walled carbon nanotube (MWCNT) modified glassy carbon electrode (GCE) was prepared for determination of isoniazid (INZ) in various matrices. The electrochemical behavior of INZ was tested with the aid of Cyclic Voltammetry (CV) and quantitative experiments were performed by using Linear Sweep Voltammetry (LSV). Morphological and structural characterization of the modified electrode was performed by utilizing Scanning Electron Microscopy (SEM), X‐Ray Photoelectron Spectroscopy (XPS) while electrochemical characterization was performed by using CV and Electrochemical Impedance spectroscopy (EIS). The proposed sensor exhibited well defined anodic peak at 0.30 V for INZ at pH 6.0 medium. Under the optimum conditions, a linear relation between INZ concentration and peak current was observed in the range of 2.0×10?7 to 5.0×10?5 M. Limit of detection was calculated as 1.0×10?8 M and repeatability and accuracy was found as 5.60 % and 91.0 % for 5.0 10?7 M INZ by using 3 successive measurement, respectively. Then, the analytic performance of the electrode developed was tested by analyzing commercial tablets, artificial human serum and urine samples. The results indicated that satisfactory recoveries was observed for all issue. 相似文献
110.