全文获取类型
收费全文 | 280篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
化学 | 178篇 |
晶体学 | 1篇 |
力学 | 6篇 |
数学 | 29篇 |
物理学 | 75篇 |
出版年
2023年 | 6篇 |
2022年 | 11篇 |
2021年 | 28篇 |
2020年 | 13篇 |
2019年 | 21篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 24篇 |
2012年 | 15篇 |
2011年 | 20篇 |
2010年 | 12篇 |
2009年 | 11篇 |
2008年 | 13篇 |
2007年 | 8篇 |
2006年 | 6篇 |
2005年 | 12篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1970年 | 2篇 |
1938年 | 1篇 |
排序方式: 共有289条查询结果,搜索用时 234 毫秒
111.
112.
In this report, the effects of conductive polymer oxidation states and structures on the design and development of ionic liquid (IL)/conductive polymer (CP) composite films for gas sensing are systematically characterized. Four different polyvinyl ferrocene (PVF) films synthesized by varying the conditioning potential (0.7 vs 0.0 V) and the electrolyte are tested for their gas-sensing properties (e.g., sensitivity, selectivity, response time, linearity, and dynamic range against various gas analytes such as dichloromethane, ethanol, natural gas, methane, formaldehyde (37%), and benzene) utilizing the quartz crystal microbalance (QCM) and ATR-FT-IR. The best available film is further studied as a substrate for the immobilization of various ILs that enhanced both the sensitivity and selectivity. Finally, two arrays, each comprising four sensors with the following scheme are developed and characterized for their ability to classify the four target analytes by using linear discriminant analysis: (1) the highest sensitivity PVF film immobilized with four different ILs and (2) the highest sensitivity IL immobilized in four different PVF films. Array 2 is proven to be much better than array 1 in discriminating the analytes, which is very significant in establishing the fact that a diverse set of PVF redox states allow the rational development of a PVF/IL composite-based sensor array in order to analyze complex mixtures utilizing structural differences and the extent of intermolecular interactions. 相似文献
113.
Fazal-ur Rehman Shahid Adeel Summia Qaiser Ijaz Ahmad Bhatti Muhammad Shahid Mohammad Zuber 《Radiation Physics and Chemistry》2012,81(11):1752-1756
Dyeing behavior of gamma irradiated cotton fabric using Lawson dye extracted from henna leaves has been investigated. Cotton and dye powder are irradiated to different absorbed doses of 2, 4, 6, 8 and 10 kGy using Cs-137 gamma irradiator. The dyeing parameters such as dyeing time, electrolyte (salt) concentration and mordant concentrations using copper and iron as mordants are optimized. Dyeing is performed using un-irradiated and irradiated cotton with dye solutions and their color strength values are evaluated in CIE Lab system using Spectraflash –SF650. Methods suggested by International Standard Organization (ISO) have been employed to investigate the colourfastness properties such as colourfastness to light, washing and rubbing of irradiated dyed fabric. It is found that gamma ray treatment of cotton dyed with extracts of henna leaves has significantly improved the color strength as well as enhanced the rating of fastness properties. 相似文献
114.
Zia‐ur‐Rehman Niaz Muhammad Afzal Shah Saqib Ali Ezzat Khan 《Heteroatom Chemistry》2012,23(6):560-567
Four triorganotin derivatives of general formula C10H10NS2SnR3,, where R = CH3 ( 1 ), C4H9 ( 2 ), C6H11 ( 3 ), and C6H5 ( 4 ), have been synthesized by the metathesis reaction of 1,2,3,4‐tetrahydroisoquinolnium salt of ligand with triorganotin(IV) chloride in the 1:1 ratio. These complexes were characterized by elemental analysis, Raman, IR, multinuclear NMR (1H, 13C, and 119Sn), and mass spectrometry. The crystal structure confirmed a supramolecular zig‐zag chain structure mediated by S–H (2.968 Å) for complex 4 with the central Sn atom exists in a distorted trigonal bipyramidal geometry. A subsequent antibacterial study indicates that the compounds are biologically active. 相似文献
115.
Ather Farooq Khan Muhammad Awais Abdul Samad Khan Sobia Tabassum Aqif Anwar Chaudhry Ihtesham Ur Rehman 《应用光谱学评论》2013,48(4):329-355
Abstract Raman spectroscopy of natural bones and hydroxyapatites is described. In addition, how Raman spectroscopy has proved crucial in providing baseline data for the modification of synthetic apatite powders that are routinely used now as bone replacement materials is explained. It is important to understand the chemical structural properties of natural bone. Bone consists of two primary components: an inorganic or mineral phase, which is mainly a carbonated form of a nanoscale crystalline calcium phosphate, closely resembling hydroxyapatite, and an organic phase, which is composed largely of type I collagen fibers. Other constituents of bone tissue include water and organic molecules such as glycosaminoglycans, glycoproteins, lipids, and peptides. Ions such as sodium, magnesium, fluoride, and citrate are also present, as well as hydrogenophosphate. Hence, the mineral phase in bone may be characterized essentially as nonstoichiometric substituted apatite. Such a distinction is important in the development of synthetic calcium phosphates for application as skeletal implants. An understanding of bone function and its interfacial relationship to an implant clearly depends on the associated structure and composition. Therefore, it is essential to fully understand the chemical composition of bone, and Raman spectroscopy is an excellent technique for such an analysis. 相似文献
116.
Abstract: Raman spectroscopy has been applied to analyze testicular cancer cell lines. Spectral differences between resistant and sensitive subtypes of testicular cancer cell line 833k samples were successfully analysed. The technique allowed reproducible and quantitative analysis of the specimen and illustrated the chemical specifications of the samples precisely. Six pairs of testicular cancer cell line 833k were studied and the findings were backed by statistical methods; that is, partial least squares discriminant analysis (PLS-DA). It was concluded that Raman spectroscopy can objectively differentiate between resistant and sensitive cell lines. These results suggest that in the future it may be possible to use cell lines and diagnostic Raman spectroscopy for preoperative classification of biological molecules. Further research is underway to determine whether results obtained from spectroscopic analysis of cell lines can be applied to actual human tissue samples. 相似文献
117.
118.
A numerical scheme, based on the Haar wavelet operational matrices of integration for solving linear two-point and multi-point boundary value problems for fractional differential equations is presented. The operational matrices are utilized to reduce the fractional differential equation to system of algebraic equations. Numerical examples are provided to demonstrate the accuracy and efficiency and simplicity of the method. 相似文献
119.
Abdullah Chandra Sekhar Talari Marcela A. Garcia Martinez Zanyar Movasaghi Shazza Rehman 《应用光谱学评论》2017,52(5):456-506
This article reviews some of the recent advances on FTIR spectroscopy in areas related to natural tissues and cell biology. It is an update on our previously published review on the applications of spectroscopic methods employed for the analysis of biological molecules, and summarizes some of the most widely used peak frequencies and their assignments. The aim of this review is to update and consolidate our previously published spectral database, which will help researchers in defining the chemical structure of the biological tissues introducing most of the important peaks present in the natural tissues more precisely and accurately. In spite of applying different methods, there seems to be a considerable similarity in defining the peaks of identical areas of the FTIR spectra. As a result, it is believed that preparing a unique collection of the frequencies encountered in FTIR spectroscopic studies can provide substantial help for future studies. In this article, we have included recent studies that have been reported since previous publication that will be of considerable assistance and added value to those who are focusing their research on defining chemical pathway to the progression of different diseases. 相似文献
120.
Muhammad Imran Fayyaz Hussain Sardar Sikandar Hayat Rana Muhammad Arif Khalil Tariq Munir Muhammad Atif Sattar Abdul Rehman Muhammad Arshad Javid Sheikh Aftab Ahmad 《Surface and interface analysis : SIA》2019,51(5):489-497
This study presents the diffusion of heterogeneous ternary (Cu-Ag-Zr) adatoms clusters on Ag(111) using molecular dynamics techniques which could be important for the surface phenomena's and helpful for the ternary cluster's growth and formation of ternary alloy-based thin films. The mechanism of nanoscale surface diffusion is investigated for 1Cu-1Ag-1Zr, 2Cu-2Ag-2Zr, 3Cu-3Ag-3Zr, and 4Cu-4Ag-4Zr clusters at temperatures 300, 500, and 700 K. The diffusion mechanism displays that the diffusion of trimer cluster exhibits hopping, sliding, and shearing at 300 K, whereas for hexamer, nonamer, and decamer, the diffusion rate is low; however, breathing, anchoring, and concentrated motion dominates. At 500 K, trimer and hexamer show the process of atomic exchange; however, the atomic exchange is not observed in the case of nonamer and decamer diffusion. The atomic exchange mechanism of Cu and Zr adatoms dominates at 700 K for all size clusters, except Ag adatoms, where Zr adatoms show a relatively more tendency. Separation and rejoining of the one and two adatoms (likely Zr adatom) are also witnessed at high temperature. The pop-up of Ag adatoms also occurs in very short intervals over the remaining adatoms of clusters. Interestingly, during trimer diffusion, the adsorption of the Zr- or Cu-adatom among the trimer cluster into the substitutional site is found. At 700 K, vacancy generation, filling of vacancies, and migration of vacancy, in the neighborhood of the adatoms cluster, also observed. Moreover, the rate of diffusion decreases with the size increase of the clusters and increases with the increase in temperature. 相似文献