全文获取类型
收费全文 | 14213篇 |
免费 | 1438篇 |
国内免费 | 379篇 |
专业分类
化学 | 1234篇 |
晶体学 | 12篇 |
力学 | 268篇 |
综合类 | 202篇 |
数学 | 2529篇 |
物理学 | 1813篇 |
无线电 | 9972篇 |
出版年
2024年 | 37篇 |
2023年 | 142篇 |
2022年 | 363篇 |
2021年 | 534篇 |
2020年 | 489篇 |
2019年 | 352篇 |
2018年 | 339篇 |
2017年 | 547篇 |
2016年 | 637篇 |
2015年 | 673篇 |
2014年 | 1130篇 |
2013年 | 1085篇 |
2012年 | 1047篇 |
2011年 | 1044篇 |
2010年 | 657篇 |
2009年 | 662篇 |
2008年 | 834篇 |
2007年 | 874篇 |
2006年 | 721篇 |
2005年 | 666篇 |
2004年 | 600篇 |
2003年 | 517篇 |
2002年 | 349篇 |
2001年 | 302篇 |
2000年 | 263篇 |
1999年 | 194篇 |
1998年 | 145篇 |
1997年 | 127篇 |
1996年 | 121篇 |
1995年 | 115篇 |
1994年 | 78篇 |
1993年 | 64篇 |
1992年 | 51篇 |
1991年 | 45篇 |
1990年 | 28篇 |
1989年 | 22篇 |
1988年 | 29篇 |
1987年 | 20篇 |
1986年 | 18篇 |
1985年 | 19篇 |
1984年 | 26篇 |
1983年 | 10篇 |
1982年 | 13篇 |
1981年 | 9篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
861.
Yusuke Shiraki Kazuhiro Tsuruta Junpei Morimoto Chihiro Ohba Akifumi Kawamura Ryo Yoshida Ryuji Kawano Tadashi Uragami Takashi Miyata 《Macromolecular rapid communications》2015,36(6):515-519
Microdevices designed for practical environmental pollution monitoring need to detect specific pollutants such as dioxins. Bisphenol A (BPA) has been widely used as a monomer for the synthesis of polycarbonate and epoxy resins. However, the recent discovery of its high potential ability to disrupt human endocrine systems has made the development of smart systems and microdevices for its detection and removal necessary. Molecule‐responsive microsized hydrogels with β‐cycrodextrin (β‐CD) as ligands are prepared by photopolymerization using a fluorescence microscope. The molecule‐responsive micro‐hydrogels show ultra‐quick shrinkage in response to target BPA. Furthermore, the flow rate of a microchannel is autonomously regulated by the molecule‐responsive shrinking of their hydrogels as smart microvalves.
862.
Serum pharmacochemistry combined with multiple data processing approach to screen the bioactive components and their metabolites in Mutan Cortex by ultra‐performance liquid chromatography tandem mass spectrometry 下载免费PDF全文
Jian‐hua Liu Hui Sun Ai‐hua Zhang Guang‐li Yan Ying Han Chang‐song Xue Xiao‐hang Zhou Hui Shi Xi‐jun Wang 《Biomedical chromatography : BMC》2014,28(4):500-510
Root cortex of Paeonia suffruticosa Andrews (Paeoniaceae), known as Moutan Cortex (MC), is known to have anti‐allergic and anti‐inflammatory properties. However, the constituents absorbed into blood after oral administration of MC remain unknown. A sensitive and rapid method by ultra‐high‐pressure liquid chromatography–electrospray ionization–quadrupole‐time‐of‐flight mass spectrometry (UPLC‐ESI‐Q‐TOF‐MS) technology and the MetaboLynxTM software combined with multiple data processing approach (Mdpa) was established to investigate the absorbed constituents in rats after oral administration of MC, providing unique high‐throughput capabilities for drug metabolism study. A hyphenated electrospray ionization and quadrupole‐time‐of‐flight analyzer was used for the determination of accurate mass of the fragment ion in negative mode, with excellent MS mass accuracy and enhanced data acquisition. This rapid automated analysis method was successfully applied for screening and identification of the constituents absorbed and metabolized studies of MC after oral administration to rats. A total of 46 peaks were obtained from MC, 41 of which were tentatively characterized. In the VIP‐plot of orthogonal partial least‐squares discriminant analysis, 23 interesting ions in serum samples were extracted, and 16 parent components and seven metabolites were detected in vivo. The integrative serum pharmacochemistry technique, UPLC‐ESI‐Q‐TOF‐MS, and Mdpa method were successfully applied for rapid discovery of multiple components from MC. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
863.
Manuel Urbano Cuadrado Gonzalo Cerruela García Irene Luque Ruiz Miguel Ángel Gómez-Nieto 《Journal of mathematical chemistry》2006,40(1):15-27
A method for the treatment of long-dimensional chemical data arrays is presented in this work with the aim of maximising classification models. The method is based on the construction of fingerprints and the subsequent generation of a similarity matrix. The similarity calculation has been modified through a scaling process to take into account different significance shown by the variables. The method was applied to spectral measurements of wines and several aspects were studied, namely: threshold considered in the construction of fingerprints and patterns, weighting factor used for scaling, normalisation method, etc. The application of both Principal Components Analysis and Soft-Independent Modelling of Class Analogies to the similarity matrices gave better classifications of the information than those obtained using original data. 相似文献
864.
The analysis
of the calorimetric continuous titration experiment is presented. The proposed
method is basing on the collection of larger number of experimental data points
than could be obtained from the classical isothermal titration calorimetry
experiment. After the deconvolution procedure resulting in the correction
for the calorimeter time response the pure power effect signal could be obtained.
The collected data enable the detailed analysis of the closely populated 2:1
and 1:1 weak complexes. 相似文献
865.
Methods for the removal of small symmetric matrix elements based on the Euclidean norm of the error matrix are presented in this article. In large scale Hartree-Fock and Kohn-Sham calculations it is important to be able to enforce matrix sparsity while keeping errors under control. Truncation based on some unitary-invariant norm allows for control of errors in the occupied subspace as described in (Rubensson et al. J Math Phys 49, 032103). The Euclidean norm is unitary-invariant and does not grow intrinsically with system size and is thus suitable for error control in large scale calculations. The presented truncation schemes repetitively use the Lanczos method to compute the Euclidean norms of the error matrix candidates. Ritz value convergence patterns are utilized to reduce the total number of Lanczos iterations. 相似文献
866.
867.
High‐performance liquid chromatography coupled with photodiode array detection has been extensively applied in many fields and the peaks among the analyzed samples can be shifted due to the variations of instrumental and experimental conditions. In multivariate analysis, retention time alignment is an important pretreatment step. Hence, the shifted peaks in high‐performance liquid chromatography coupled with photodiode array detection three‐dimensional spectra should be aligned for further analysis. Being motivated by this purpose, the interval correlated shifting method combined with the proposed data arrangement methods are recommended and employed on high‐performance liquid chromatography coupled with photodiode array detection data as a demonstration. We validate the alignment performance of the proposed method through comparison the consistency of the retention time before and after alignment. The obtained results demonstrated that the proposed method is capable of successful aligning the employed data. Additionally, the interval correlated shifting method combined with the data arrangement modes is implemented in an easy‐to‐use graphical user interface environment and so can be operated easily by users not familiar with programming languages. 相似文献
868.
Culzoni MJ Goicoechea HC Ibañez GA Lozano VA Marsili NR Olivieri AC Pagani AP 《Analytica chimica acta》2008,614(1):46-57
Multivariate curve resolution coupled to alternating least-squares (MCR-ALS) has been employed to model kinetic-spectroscopic second-order data, with focus on the achievement of the important second-order advantage, under conditions of extreme spectral overlapping among sample components. A series of simulated examples shows that MCR-ALS can conveniently handle the studied analytical problem unlike other second-order multivariate calibration algorithms, provided matrix augmentation is implemented in the spectral mode instead of in the usual kinetic mode. The approach has also been applied to three experimental examples, which involve the determination of: (1) the antiparkinsonian carbidopa (analyte) in the presence of levodopa as a potential interferent, both reacting with cerium (IV) to produce the fluorescent species cerium (III) with different kinetics; (2) Fe(II) (analyte) in the presence of the interferent Zn(II), both catalyzing the oxidation of methyl orange with potassium bromate; and (3) tartrazine (analyte) in the presence of the interferent brilliant blue, both oxidized with potassium bromate, with the interferent leading to a product with an absorption spectrum very similar to tartrazine. The results indicate good analytical performance towards the analytes, despite the intense spectral overlapping and the presence of unexpected constituents in the test samples. 相似文献
869.
Vakhid A. Mamedov Dina F. Saifina Aidar T. Gubaidullin Alina F. Saifina Il’dar Kh. Rizvanov 《Tetrahedron letters》2008,49(43):6231-6233
A highly efficient one-step and versatile method for the synthesis of 2-(indolizin-2-yl)benzimidazoles has been developed on the basis of the novel ring contraction of 3-arylchloromethyl- and alkylchloromethylquinoxalin-2-ones with α-picoline. 相似文献
870.