全文获取类型
收费全文 | 368篇 |
免费 | 2篇 |
专业分类
化学 | 158篇 |
晶体学 | 15篇 |
力学 | 39篇 |
数学 | 99篇 |
物理学 | 59篇 |
出版年
2023年 | 1篇 |
2021年 | 5篇 |
2020年 | 6篇 |
2019年 | 3篇 |
2018年 | 33篇 |
2017年 | 32篇 |
2016年 | 16篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 13篇 |
2012年 | 22篇 |
2011年 | 31篇 |
2010年 | 25篇 |
2009年 | 26篇 |
2008年 | 26篇 |
2007年 | 30篇 |
2006年 | 9篇 |
2005年 | 20篇 |
2004年 | 3篇 |
2003年 | 4篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1965年 | 1篇 |
1964年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有370条查询结果,搜索用时 0 毫秒
111.
Fatih Özkaynak 《Nonlinear dynamics》2018,92(2):305-313
Chaos-based cryptology has become one of the most common design techniques to design new encryption algorithms in the last two decades. However, many proposals have been observed to be weak against simple known attacks. However, security of proposals cannot be proved. An analysis roadmap is needed for the security analysis of new proposals. This study aims to address this shortcoming. Analysis and test results show that many chaos-based image encryption algorithms previously published in the nonlinear dynamics are actually not as secure as they are expressed although these algorithms do pass several statistical and randomness tests. A checklist has been proposed to solve these problems. The applications of the proposed checklist have been shown for different algorithms. The proposed checklist is thought to be a good starting point for researchers who are considering to work in chaos-based cryptography. 相似文献
112.
Rafet Kılınçarslan M. Emin Günay Rukiye Fırıncı Serpil Denizaltı Bekir Çetinkaya 《应用有机金属化学》2016,30(5):268-272
A new series of sterically hindered ligands containing (1R,2S,4R)‐(+)‐menthoxymethyl group attached to benzimidazole‐based N‐heterocyclic carbene (NHC), palladium–bis‐NHC complexes and (κ2‐C,N)‐palladacyclic NHC complexes have been synthesized and characterized using appropriate spectroscopic techniques. Catalytic performance of the palladium complexes has been investigated for allylic alkylation, Suzuki and Heck carbon–carbon coupling reactions. These complexes smoothly catalyse the carbon–carbon bond formation reactions. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
113.
This study reports the development of a novel sensing material that reports on analyte concentrations via diffraction of visible
light from polymerized crystalline colloidal arrays (PCCA). The PCCA contains periodic crystalline colloidal array (CCA) of spherical polystyrene colloids. This new method permanently locks the order of the CCA by embedding the CCA into a polymer
network. These materials are mostly used in the development of novel materials which are basically called sensors for metal
ions and all kinds of organic molecules. The polymer around the crystalline colloid can be functionalized with some recognition
molecule, making these materials useful as optical sensors. We developed a sensor, utilizing crown ether, 2-aminomethyl-18-crown-6
(2A18C6) as the recognition agent, that detects K+ in the concentration range from 5 to 160 ppm. 相似文献
114.
We have calculated relativistic energies and Landé factors for 5d6s
2, 5d
26s, 6s6p
2, 6s
27s, 5d
3, 5d6s7s, 6s
26p, 5d6s6p, 5d
26p and 6s
27p excited levels outside the core [Xe]4f
14 in neutral lutetium (Lu I, Z = 71). These calculations are based on the multiconfiguration Hartree-Fock (MCHF) method, within the framework of the Breit-Pauli
relativistic corrections. Moreover, the results obtained have been compared with other works. 相似文献
115.
A. Emin Atik Oscar Hernandez Philippe Maître Talat Yalcin 《Journal of mass spectrometry : JMS》2014,49(12):1290-1297
Characterization of ε‐N‐acetylated lysine containing peptides, one of the most prominent post‐translational modifications of proteins, is an important goal for tandem mass spectrometry experiments. A systematic study for the fragmentation reactions of b ions derived from ε‐N‐acetyllysine containing model octapeptides (KAcYAGFLVG and YAKAcGFLVG) has been examined in detail. Collision‐induced dissociation (CID) mass spectra of bn (n = 4–7) fragments of ε‐N‐acetylated lysine containing peptides are compared with those of N‐terminal acetylated and doubly acetylated (both ε‐N and N‐terminal) peptides, as well as acetyl‐free peptides. Both direct and nondirect fragments are observed for acetyl‐free and singly acetylated (ε‐N or N‐terminal) peptides. In the case of ε‐N‐acetylated lysine containing peptides, however, specific fragment ions (m/z 309, 456, 569 and 668) are observed in CID mass spectra of bn (n = 4–7) ions. The CID mass spectra of these four ions are shown to be identical to those of selected protonated C‐terminal amidated peptides. On this basis, a new type of rearrangement chemistry is proposed to account for the formation of these fragment ions, which are specific for ε‐N‐acetylated lysine containing peptides. Consistent with the observation of nondirect fragments, it is proposed that the b ions undergo head‐to‐tail macrocyclization followed by ring opening. The proposed reaction pathway assumes that bn (n = 4–7) of ε‐N‐acetylated lysine containing peptides has a tendency to place the KAc residue at the C‐terminal position after macrocyclization/reopening mechanism. Then, following the loss of CO, it is proposed that the marker ions are the result of the loss of an acetyllysine imine as a neutral fragment. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
116.
Preparation of CTA-based polymer inclusion membrane using calix[4]arene derivative as a carrier for Cr(VI) transport 总被引:1,自引:0,他引:1
Ahmet Kaya Canan Onac Ahmet Surucu Emin Karapinar Hamza K. Alpoguz Begum Tabakci 《Journal of inclusion phenomena and macrocyclic chemistry》2014,79(1-2):103-111
In this work, the transport of Cr(VI) ions from an aqueous donor phase solution to an acceptor phase that contained an acetic acid/ammonium acetate buffer at pH 5 through a polymer inclusion membrane (PIM) containing p-tert-butylcalix[4]arene amine derivative as carrier was studied. The Cr(VI) passed through a PIM comprised of cellulose triacetate as a support and 2-NPOE as a plasticizer. The transport efficiency of Cr(VI) was studied under various experimental conditions, such as effect of carrier concentration, acceptor phase pH, type of plasticizer in the membrane, stirring rate and membrane thickness. The kinetic parameters were calculated as rate constant (k), permeability coefficient (P), and flux (J). The transport efficiency of Cr(VI) was observed to be 95.07 % after 10 h under optimized conditions. The prepared PIM was characterized with Fourier transform infrared spectroscopy and the atomic force microscopy techniques as well as with contact angle measurements. This is an effective method for the removal of Cr(VI) which is toxic for human body and environment from the waste water. 相似文献
117.
Emin Aydın Ali Delice Derya Demiroğlu 《BSHM Bulletin: Journal of the British Society for the History of Mathematics》2016,31(3):215-229
Research in history of mathematics gained momentum in the past two decades in Turkey. The present paper aims to describe the patterns in the history of mathematics research in Turkey and to analyse the research in Turkey using a mathematics education framework. The qualitative paradigm and a case study design are used in the study. The obtained data were analysed by using the document analysis technique with the help of a content analysis. The study group which is comprised of twenty-two postgraduate theses at master's or doctoral level were purposefully selected from the higher education council postgraduate theses database. Findings indicate a dearth of research in the area and that most of the theses are done in the area of mathematics education. Moreover, the focus, in general, was on attitudinal variables, and cognitive aspects seemed to be ignored. 相似文献
118.
M. Emin Günay Osman Dayan Ayta Gürhan Gke Muhittin Aygün Bekir etinkaya Orhan Büyükgüngr 《Polyhedron》2008,27(18):3607-3610
Treatment of N,N′-bis(mesityl)pyridine-2,6-carboxyimidoyl dichloride, 1, in toluene solution with [Pt(PPh3)4] at 100 °C afforded a novel platinacyclic compound, 3, in 63% yield, instead of the expected compound 2. The molecular and crystal structures of the title compound, 3, have been determined by the single crystal X-ray diffraction technique. The coordination geometries around the Pt atoms are distorted square-planar. In the crystal structure, the molecules are linked by a pair of C–H···N hydrogen bonds into a centrosymmetric dimer with an ring, centred at (1/2,1/2,1/2). 相似文献
119.
Ahmet Coşkun Emin Karapinar 《Journal of inclusion phenomena and macrocyclic chemistry》2008,60(1-2):59-64
4-(Chloroacetyl)diphenyl thioether (1) was synthesized from chloroacetyl chloride and diphenyl thioether in the presence of
AlCl3 as catalyst in a Friedel-Crafts reaction. Subsequently, its keto oxime (2) and glyoxime (3) derivatives were prepared. N-(4′-Benzo[15-crown-5]thiophenoxyphenylaminoglyoxime
(H2L) and its sodium chloride complex (H2L · NaCl) were prepared from 4-(thiophenoxy)chlorophenylglyoxime (3), 4′-aminobenzo[15-crown-5] and sodium bicarbonate or
sodium bicarbonate and sodium chloride. Ni(II), Co(II) and Cu(II) complexes of H2L and H2L · NaCl have a metal–ligand ratio of 1:2 and the ligand coordinates through the two N atoms, as do most of the vic-dioximes. The BF2-capped Ni(II) mononuclear complex of the vic-dioxime was prepared. The macrocyclic ligands and their transition metal complexes
were characterized on the basis of FT-IR, 1H NMR, 13C NMR spectroscopy and elemental analyses data. 相似文献
120.
PROMETHEE is a powerful method, which can solve many multiple criteria decision making (MCDM) problems. It involves sophisticated preference modelling techniques but requires too much a priori precise information about parameter values (such as criterion weights and thresholds). In this paper, we consider a MCDM problem where alternatives are evaluated on several conflicting criteria, and the criterion weights and/or thresholds are imprecise or unknown to the decision maker (DM). We build robust outranking relations among the alternatives in order to help the DM to rank the alternatives and select the best alternative. We propose interactive approaches based on PROMETHEE method. We develop a decision aid tool called INTOUR, which implements the developed approaches. 相似文献