全文获取类型
收费全文 | 1058篇 |
免费 | 100篇 |
国内免费 | 85篇 |
专业分类
化学 | 628篇 |
力学 | 30篇 |
综合类 | 11篇 |
数学 | 205篇 |
物理学 | 369篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 19篇 |
2020年 | 18篇 |
2019年 | 18篇 |
2018年 | 28篇 |
2017年 | 35篇 |
2016年 | 48篇 |
2015年 | 41篇 |
2014年 | 51篇 |
2013年 | 81篇 |
2012年 | 71篇 |
2011年 | 69篇 |
2010年 | 71篇 |
2009年 | 80篇 |
2008年 | 86篇 |
2007年 | 67篇 |
2006年 | 74篇 |
2005年 | 68篇 |
2004年 | 63篇 |
2003年 | 52篇 |
2002年 | 42篇 |
2001年 | 39篇 |
2000年 | 26篇 |
1999年 | 19篇 |
1998年 | 10篇 |
1997年 | 13篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1987年 | 1篇 |
1985年 | 3篇 |
1975年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有1243条查询结果,搜索用时 156 毫秒
81.
Aydan Dag Hakan Durmaz Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2008,46(1):302-313
Diels–Alder click reaction was successfully applied for the preparation of 3‐arm star polymers (A3) using furan protected maleimide end‐functionalized polymers and trianthracene functional linking agent (2) at reflux temperature of toluene for 48 h. Well‐defined furan protected maleimide end‐functionalized polymers, poly (ethylene glycol), poly(methyl methacrylate), and poly(tert‐butyl acrylate) were obtained by esterification or atom transfer radical polymerization. Obtained star polymers were characterized via NMR and GPC (refractive index and triple detector detection). Splitting of GPC traces of the resulting polymer mixture notably displayed that Diels–Alder click reaction was a versatile and a reliable route for the preparation of A3 star polymer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 302–313, 2008 相似文献
82.
Hugh Chaffey‐Millar Gene Hart‐Smith Christopher Barner‐Kowollik 《Journal of polymer science. Part A, Polymer chemistry》2008,46(5):1873-1892
A mass spectrometry analysis has been performed on complex architecture polymeric material produced during reversible addition fragmentation chain transfer (RAFT) polymerizations yielding star polymers. Para‐acetoxystyrene (AcOSty) has been polymerized at 60 °C, using azobisisobutyronitrile (AIBN) as the thermally decomposing initiator, in the presence of the R‐group approach tetrafunctional RAFT agent (1,2,4,5‐tetrakis‐(2‐phenyl‐thioacetyl‐sulfanylmethyl)‐benzene). In addition to ideal star material, a variety of products unique to this mode of polymerization have been identified. These include star–star couples, stars terminated with initiator fragments, star–star couples terminated with initiator fragments and linear polymers, supporting the notion that these species are responsible for the structured molecular‐weight distributions measured for these systems when analyzed via gel permeation chromatography. The analysis begins with a study of AcOSty polymerizing (i) in the absence of any mediating agent and (ii) in the presence of a monofunctional RAFT agent, revealing the mode of termination of propagating poly(AcOSty) radicals as combination and that some ionization biases exist among variants of poly (AcOSty). The interpretation of the mass spectrometry data has been aided by a novel kinetic model of star polymerizations, allowing the rationalization of experimental observations with theoretical expectations. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 1873–1892, 2008 相似文献
83.
Eda Gungor Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2008,46(20):6703-6711
The terminal alkyne homocoupling reaction (oxidative alkyne coupling) is presented here as a new route for the preparation of A2B2 type 4‐miktoarm star copolymer. The block copolymer with terminal alkyne at the junction point prepared by NMP‐ATRP and ROP‐NMP sequential routes is coupled via diyne formation to give (PS)2‐(PMMA)2 and (PCL)2‐(PS)2 4‐miktoarm star polymers, respectively, by using a combination of (PPh3)2PdCl2/PPh3/CuI in a solvent mixture of Et3N/CH3CN at room temperature for 72 h. The molecular weight, intrinsic viscosity ([η]), radius of gyration (Rg), and hydrodynamic radius (Rh) of A2B2 4‐miktoarm star copolymers were calculated using triple‐detection GPC as results of three detectors response. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6703–6711, 2008 相似文献
84.
SOME INEQUALITIES ABOUT DUAL MIXED VOLUMES OF STAR BODIES 总被引:1,自引:0,他引:1
The authors establish some inequalities about the dual mixed volumes of star bodies in R^n. These inequalities are the analogue in the Brunn-Minkowski theory of the inequalities of Marcus-Lopes and Bergstrom about symmetric functions of positive reals. 相似文献
85.
岑建苗 《浙江大学学报(理学版)》2005,32(6):601-604,610
利用态射的加权广义逆,引进并讨论态射集中的加权减序和加权星序.给出了态射集中的加权减序的一些刻画和性质以及加权减序和加权星序之间的关系.加权减序和加权星序都是态射集中的新的偏序.所得结果均可应用于矩阵理论中.
关键词:态射;加权广义逆;加权减序;加权星序 相似文献
86.
Peng‐Fei Gou Wei‐Pu Zhu Ning Zhu Zhi‐Quan Shen 《Journal of polymer science. Part A, Polymer chemistry》2009,47(11):2905-2916
Novel amphiphilic eight‐arm star triblock copolymers, star poly(ε‐caprolactone)‐block‐poly(acrylic acid)‐block‐poly(ε‐caprolactone)s (SPCL‐PAA‐PCL) with resorcinarene as core moiety were prepared by combination of ROP, ATRP, and “click” reaction strategy. First, the hydroxyl end groups of the predefined eight‐arm SPCLs synthesized by ROP were converted to 2‐bromoesters which permitted ATRP of tert‐butyl acrylate (tBA) to form star diblock copolymers: SPCL‐PtBA. Next, the bromide end groups of SPCL‐PtBA were quantitatively converted to terminal azides by NaN3, which were combined with presynthesized alkyne‐terminated poly(ε‐caprolactone) (A‐PCL) in the presence of Cu(I)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine in DMF to give the star triblock copolymers: SPCL‐PtBA‐PCL. 1H NMR, FTIR, and SEC analyses confirmed the expected star triblock architecture. The hydrolysis of tert‐butyl ester groups of the poly(tert‐butyl acrylate) blocks gave the amphiphilic star triblock copolymers: SPCL‐PAA‐PCL. These amphiphilic star triblock copolymers could self‐assemble into spherical micelles in aqueous solution with the particle size ranging from 20 to 60 nm. Their micellization behaviors were characterized by dynamic light scattering and transmission electron microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2905–2916, 2009 相似文献
87.
Eda Gungor Cigdem Bilir Hakan Durmaz Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2009,47(22):5947-5953
Azidopropyl‐heptaisobutyl‐substituted polyhedral oligomeric silsesquioxane (POSS‐N3) was reacted with 1,1,1‐tris[4‐(2‐propynyloxy)phenyl]‐ethane ( 1 ) and poly(ethylene glycol) (PEG)‐b‐poly(methyl methacrylate) (PMMA) copolymer with alkyne at its center (PEG‐PMMA‐alkyne) affording the first time synthesis of 3‐arm star POSS and PEG‐PMMA‐POSS 3‐miktoarm star terpolymer, respectively, in the presence of CuBr/N,N,N′,N″,N″‐pentamethyldiethylenetriamine as catalyst and N,N‐dimethylformamide/tetrahydrofuran as solvent at room temperature. The precursors and the target star polymers were characterized comprehensively by 1H NMR, GPC, and DSC. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5947–5953, 2009 相似文献
88.
Aziz Gozgen Aydan Dag Hakan Durmaz Okan Sirkecioglu Gurkan Hizal Umit Tunca 《Journal of polymer science. Part A, Polymer chemistry》2009,47(2):497-504
A combination of ring opening metathesis polymerization (ROMP) and click chemistry approach is first time utilized in the preparation of 3‐miktoarm star terpolymer. The bromide end‐functionality of monotelechelic poly(N‐butyl oxanorbornene imide) (PNBONI‐Br) is first transformed to azide and then reacted with polystyrene‐b‐poly(methyl methacrylate) copolymer with alkyne at the junction point (PS‐b‐PMMA‐alkyne) via click chemistry strategy, producing PS‐PMMA‐PNBONI 3‐miktoarm star terpolymer. PNBONI‐Br was prepared by ROMP of N‐butyl oxanorbornene imide (NBONI) 1 in the presence of (Z)‐but‐2‐ene‐1,4‐diyl bis(2‐bromopropanoate) 2 as terminating agent. PS‐b‐PMMA‐alkyne copolymer was prepared successively via nitroxide‐mediated radical polymerization (NMP) of St and atom transfer radical polymerization (ATRP) of MMA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 497–504, 2009 相似文献
89.
Aydan Dag Hakan Durmaz Umit Tunca Gurkan Hizal 《Journal of polymer science. Part A, Polymer chemistry》2009,47(1):178-187
Two types of multiarm star block copolymers: (polystyrene)m‐poly(divinylbenzene)‐poly(methyl methacrylate)n, (PS)m‐polyDVB‐(PMMA)n and (polystyrene)m‐poly(divinylbenzene)‐poly(tert‐butyl acrylate)k, (PS)m‐polyDVB‐(PtBA)k were successfully prepared via a combination of cross‐linking and Diels–Alder click reactions based on “arm‐first” methodology. For this purpose, multiarm star polymer with anthracene functionality as reactive periphery groups was prepared by a cross‐linking reaction of divinyl benzene using α‐anthracene end functionalized polystyrene (PS‐Anth) as a macroinitiator. Thus, obtained multiarm star polymer was then reacted with furan protected maleimide‐end functionalized polymers: PMMA‐MI or PtBA‐MI at reflux temperature of toluene for 48 h resulting in the corresponding multiarm star block copolymers via Diels–Alder click reaction. The multiarm star and multiarm star block copolymers were characterized by using 1H NMR, SEC, Viscotek triple detection SEC (TD‐SEC) and UV. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 178–187, 2009 相似文献
90.
Koji Nagahama Kanae Fujiura Shunsuke Enami Tatsuro Ouchi Yuichi Ohya 《Journal of polymer science. Part A, Polymer chemistry》2008,46(18):6317-6332
Starburst triblock copolymers consisting of 8‐arm poly(ethylene glycol) (8‐arm PEG) and biodegradable poly(L ‐lactide) (PLLA) or its enantiomer poly(D ‐lactide) (PDLA), 8‐arm PEG‐b‐PLLA‐b‐PEG ( Stri‐L ), and 8‐arm PEG‐b‐PDLA‐b‐PEG ( Stri‐D ) were synthesized. An aqueous solution of a 1:1 mixture ( Stri‐Mix ) of Stri‐L and Stri‐D assumed a sol state at room temperature, but instantaneously formed a physically crosslinked hydrogel in response to increasing temperature. The resulting hydrogel exhibited a high‐storage modulus (9.8 kPa) at 37 °C. Interestingly, once formed at the transition temperature, the hydrogel was stable even after cooling below the transition temperature. The hydrogel formation process was irreversible because of the formation of stable stereocomplexes. In aqueous solution, gradual hydrolytic erosion was observed because of degradation of the hydrogel. The combination of rapid temperature‐triggered irreversible hydrogel formation, high‐mechanical strength, and degradation behavior render this polymer mixture system suitable for use in injectable biomedical materials, for example, as a drug delivery system for bioactive reagents or a biodegradable scaffold for tissue engineering. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6317–6332, 2008 相似文献