全文获取类型
收费全文 | 3456篇 |
免费 | 432篇 |
国内免费 | 237篇 |
专业分类
化学 | 1774篇 |
晶体学 | 25篇 |
力学 | 331篇 |
综合类 | 101篇 |
数学 | 473篇 |
物理学 | 1421篇 |
出版年
2024年 | 8篇 |
2023年 | 25篇 |
2022年 | 76篇 |
2021年 | 76篇 |
2020年 | 73篇 |
2019年 | 71篇 |
2018年 | 79篇 |
2017年 | 120篇 |
2016年 | 161篇 |
2015年 | 120篇 |
2014年 | 162篇 |
2013年 | 256篇 |
2012年 | 169篇 |
2011年 | 217篇 |
2010年 | 184篇 |
2009年 | 216篇 |
2008年 | 248篇 |
2007年 | 260篇 |
2006年 | 261篇 |
2005年 | 212篇 |
2004年 | 168篇 |
2003年 | 146篇 |
2002年 | 127篇 |
2001年 | 110篇 |
2000年 | 83篇 |
1999年 | 70篇 |
1998年 | 76篇 |
1997年 | 51篇 |
1996年 | 43篇 |
1995年 | 46篇 |
1994年 | 35篇 |
1993年 | 31篇 |
1992年 | 22篇 |
1991年 | 25篇 |
1990年 | 20篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1970年 | 1篇 |
1969年 | 2篇 |
1967年 | 1篇 |
1959年 | 2篇 |
排序方式: 共有4125条查询结果,搜索用时 93 毫秒
101.
Satyasankar Jana Vivek Arjunan Vasantha Ludger Paul Stubbs Anbanandam Parthiban Julius G. Vancso 《Journal of polymer science. Part A, Polymer chemistry》2013,51(15):3260-3273
Vinylimidazole‐based asymmetric ion pair comonomers ( IPC s) which are free from nonpolymerizable counter ions have been synthesized, characterized and polymerized by free radical polymerization (FRP), atom transfer radical polymerization (ATRP), and reversible addition‐fragmentation chain transfer (RAFT) mediated polymerizations in solution and by dispersion polymerization in water. The asymmetric nature of IPC s is due to the fact that cationic component of these IPCs is derived from vinylimidazole (VIm) and anionic component is derived from either styrenesulfonate (SS) or 2‐acrylamido‐2‐methyl‐1‐propanesulfonate. Although under ATRP, conversions are either very low or negligible, FRP and RAFT produces polymers with high to moderate monomer conversions but with different solubility characteristics. This investigation provides insight to the polymerization behavior of each component of the asymmetric IPCs and also its effects on composition and solubility characteristics of the resulting polymers. The IPCs studied here are high temperature ionic liquid and thus the polymers synthesized from these IPCs are highly ionic in nature and possess very strong intermolecular interactions which makes some of these IPC based polymers completely insoluble in organic and aqueous solvents. This highly ionic interaction is exploited to synthesize ionically crosslinked PMMA. MMA on copolymerization with 5–6 mol % of IPC yielded copolymer which is insoluble in common organic solvents like THF, DMF, etc., unlike homo PMMA. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3260–3273 相似文献
102.
固体材料在冲击拉伸载荷作用下常常会断裂成多个碎片(碎片化),固体材料碎片化的物理机制是多点损伤同时在固体中成核和发展,导致固体多处破坏。自 Mott 对固体的动态碎裂问题进行了开创性研究后,几十年来,对固体动态碎裂机制的研究一直是应用物理学、力学、航天和兵器工程等领域共同关心的重要课题。本文介绍了在冲击拉伸载荷作用下固体的动态碎裂研究的发展历史,给出相关的理论分析、实验研究和数值模拟的研究进展,特别针对现有的各种关于碎片尺度、碎片分布、以及碎片化物理机制的理论模型进行了较详尽的阐述和讨论,最后指出现有实验和理论研究中仍然存在的关键科学问题及进一步的研究展望。 相似文献
103.
Functional poly(N-isopropylacrylamide) (PNIPAM) hydrogels were prepared by reversible addition fragmentation chain transfer (RAFT) polymerization of NIPAM in the presence of four-arm poly(ethylene glycol) (4A-PEG) as backbone and 4-cyanopentanoic acid dithiobenzoate functional α -cyclodextrin threaded onto the PEG as chain transfer reagent (CTA).The structure of the hydrogels was characterized in detail with FTIR techniques. The analytical results demonstrated that α -cyclodextrin remains in as-obtained hydrogels. The swelling behavior was investigated and the functional hydrogels (functional gels) showed accelerated shrinking kinetics and higher swelling ratio comparing with conventional hydrogel (CG). It could be attributed to the presence of dangling chains. The hydrogel exhibited rapid swelling and deswelling kinetics. In principle, the hydrogel might find a number of applications including an on-off system and drug delivery systems. 相似文献
104.
Synthesis of polymer with defined fluorescent end groups via reversible addition fragmentation transfer polymerization for characterizing the conformations of polymer chains in solutions
下载免费PDF全文
![点击此处可从《Journal of polymer science. Part A, Polymer chemistry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Ye Sha Qing Zhu Yuanxin Wan Linling Li Xiaoliang Wang Gi Xue Dongshan Zhou 《Journal of polymer science. Part A, Polymer chemistry》2016,54(15):2413-2420
A new type of chain transfer agent used in reversible addition fragmentation chain transfer (RAFT) polymerization named 9‐anthracenylmethyl (4‐cyano‐4‐(N‐carbazylcarbodithioate) pentanoate) (ACCP) was synthesized with a total yield over 75% by the incorporation of both fluorescent donor and acceptor chromophores. Polymerization of heterotelechelic α,ω end‐labeled dye‐functionalized polystyrene (PS), poly(methyl methacrylate) (PMMA), and poly(n‐butyl methacrylate) (PBMA) with adjustable molecular weights and narrow polydispersity could be conducted by a one‐pot procedure through RAFT polymerization with this bischromophore chain transfer agent. The polymerizations demonstrated “living” controlled characteristics. By taking advantage of the characteristic fluorescence resonance energy transfer (FRET) response between the polymer chain terminals, the variation of chain dimensions in solution from the dilute region to the semidilute region can be monitored by changes in the ratio of the fluorescence intensities of the carbazolyl group to the anthryl group, which lends itself to potential applications in characterizing chain dimensions in solutions for thermodynamic or dynamic studies. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2413–2420 相似文献
105.
Eriko Sato Noboru Tamari Hideo Horibe 《Journal of polymer science. Part A, Polymer chemistry》2019,57(24):2474-2480
Graft copolymers show microphase separated structure as seen in block copolymers and have lower intrinsic viscosity than block copolymers because of a branching structure. Therefore, considering molding processability, especially for polymers containing rigid segments, graft copolymers are useful architectures. In this work, graft copolymers containing rigid poly(diisopropyl fumarate) (PDiPF) branches were synthesized by full free‐radical polymerization process. First, synthesis of PDiPF macromonomers by addition‐fragmentation chain transfer (AFCT) was investigated. 2,2‐Dimethyl‐4‐methylene‐pentanedioic acid dimethyl ester was found to be an efficient AFCT agent for diisopropyl fumarate (DiPF) polymerization because of the suppression of undesired primary radical termination, which significantly took place when common AFCT agent, methyl 2‐(bromomethyl)acrylate, was used. Copolymerization of PDiPF macromonomer with ethyl acrylate accomplished the generation of the graft copolymer having flexible poly(ethyl acrylate) backbone and rigid PDiPF branches. The graft copolymer showed a microphase separated structure, high transparency, and characteristic thermal properties to PDiPF and poly(ethyl acrylate). © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 2474–2480 相似文献
106.
Metabolite identification of the antimalarial piperaquine in vivo using liquid chromatography–high‐resolution mass spectrometry in combination with multiple data‐mining tools in tandem
下载免费PDF全文
![点击此处可从《Biomedical chromatography : BMC》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Aijuan Yang Meitong Zang Huixiang Liu Peihong Fan Jie Xing 《Biomedical chromatography : BMC》2016,30(8):1324-1330
Artemisinin‐based combination therapy is widely used for the treatment of uncomplicated Plasmodium falciparum malaria, and piperaquine (PQ) is one of important partner drugs. The pharmacokinetics of PQ is characterized by a low clearance and a large volume of distribution; however, metabolism of PQ has not been thoroughly investigated. In this work, the metabolite profiling of PQ in human and rat was studied using liquid chromatography tandem high‐resolution LTQ‐Orbitrap mass spectrometry (HRMS). The biological samples were pretreated by solid‐phase extraction. Data processes were carried out using multiple data‐mining techniques in tandem, i.e., isotope pattern filter followed by mass defect filter. A total of six metabolites (M1–M6) were identified for PQ in human (plasma and urine) and rat (plasma, urine and bile). Three reported metabolites were also found in this study, which included N‐oxidation (M1, M2) and carboxylic products (M3). The subsequent N‐oxidation of M3 resulted in a new metabolite M4 detected in urine and bile samples. A new metabolic pathway N‐dealkylation was found for PQ in human and rat, leading to two new metabolites (M5 and M6). This study demonstrated that LC‐HRMSn in combination with multiple data‐mining techniques in tandem can be a valuable analytical strategy for rapid metabolite profiling of drugs. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
107.
《Journal of mass spectrometry : JMS》2017,52(8):543-549
1,4,7,10‐Tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) derivatives are applied in quantitative proteomics owing to their ability to react with different functional groups, to harbor lanthanoides and hence their compatibility with molecular and elemental mass spectrometry. The new DOTA derivatives, namely Ln‐MeCAT‐Click and Ln‐DOTA‐Dimedone, allow efficient thiol labeling and targeting sulfenation as an important post‐translational modification, respectively. Quantitative applications require the investigation of fragmentation behavior of these reagents. Therefore, the fragmentation behavior of Ln‐MeCAT‐Click and Ln‐DOTA‐Dimedone was studied using collision‐induced dissociation (CID), infrared multiphoton dissociation (IRMPD) and higher‐energy collision dissociation (HCD) using different energy levels, and the efficiency of reporter ion production was estimated. The efficiency of characteristic fragment formation was in the order IRMPD > HCD (normal energy level) > CID. On the other hand, the application of HCD at high energy levels (HCD@HE; NCE > 250%) resulted in a significant increase in reporter ion production (33–54%). This new strategy was successfully applied to generate label‐specific reporter ions for DOTA amino labeling at the N‐termini and in a quantitative fashion for the estimation of amino:thiol ratio in peptides. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
108.
Norberto Manfredi Alberto Bianchi Valerio Causin Riccardo Ruffo Roberto Simonutti Alessandro Abbotto 《Journal of polymer science. Part A, Polymer chemistry》2014,52(5):719-727
The first use of PSn‐b‐PEOm‐b‐PSn block copolymers (PS = polystyrene, PEO = poly(ethylene oxide)) as solid hosts for iodine/iodide electrolytes in dye‐sensitized solar cells (DSSCs) is described. Using the benchmark photosensitizer N719, DSSC based on the quasi solid‐state electrolytes afforded efficiencies up to 6.7%, to be compared with an efficiency of 7.3% obtained in similar conditions with a conventional iodine/iodide liquid electrolyte. By varying the PS:PEO relative volume ratio in the block copolymers different properties and morphologies were obtained. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 719–727 相似文献
109.
Yukun Li Leela Christian‐Tabak Vivien Li Fong Fuan Jiong Zou Chong Cheng 《Journal of polymer science. Part A, Polymer chemistry》2014,52(22):3250-3259
Amphiphilic double‐brush copolymers (DBCs) with each graft site quantitatively carrying both a hydrophilic poly(ethylene oxide) (PEO) graft and a hydrophobic polystyrene (PSt) graft are synthesized by sequential reversible addition‐fragmentation chain transfer (RAFT) polymerization and ring‐opening metathesis polymerization (ROMP). These DBCs are used as both surfactants and polyfunctional RAFT agents in the radical polymerization of St in aqueous dispersed media. Miniemulsions with narrowly dispersed St‐based nanodroplets are readily obtained after ultrasonication of the reaction mixtures. Without the presence of crosslinker, chain‐extension polymerization of St from the DBCs yields well‐defined polymeric latexes with narrow size distributions. However, with the presence of divinylbenzene (DVB) as the crosslinker, vesicular polymeric nanoparticles are formed as the major product. Such crosslinking‐induced change in morphology of the resulting latex nanomaterials may be ascribed to the increase of interfacial curvature in the heterophase systems during crosslinking polymerization. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3250–3259 相似文献
110.
Bingyan Jiang Lei Zhang Jie Yan Qingquan Huang Bing Liao Hao Pang 《Journal of polymer science. Part A, Polymer chemistry》2014,52(17):2442-2453
A series of well‐defined thermoresponsive graft polymers with different lengths and graft densities, poly(glycidyl methacrylate)‐graft‐poly(N‐isopropylacrylate) (PGMA‐g‐PNIPAM), were successfully prepared by combination of controlled/living free radical polymerization and click chemistry. Effects of grafting length and density on the thermoresponsive behavior, aggregating mean diameter, and self‐assembly morphology are systematically investigated. The thermosensitive characteristics of graft polymers in aqueous solution prove that the length and graft density had positive co‐relationship with the lower critical solution temperature value and mean diameter of micelles as well as the size distribution, while the effect of graft length of polymers is more significant than that of density. Transmission electron microscopy analysis shows that the conformations of PGMA45‐g‐PNIPAM20 and PGMA45‐g‐PNIPAM46 with longer length and bigger grafting density in aqueous solutions are spherical nanoparticles with the increasing trend of the diameters, while that of PGMA45‐g‐PNIPAM(73, 50%) shows a spherical‐like morphology, which indicates that the graft length and density have a significant effect on the mean diameter of micelle but not on the self‐assembly morphology. These results reveal that to obtain desired thermoresponsive behavior and self‐assembly morphology of functional polymers, it is essential to design and fabricate the structure of graft polymers with proper length and graft density. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2442–2453 相似文献