全文获取类型
收费全文 | 2864篇 |
免费 | 162篇 |
国内免费 | 46篇 |
专业分类
化学 | 1799篇 |
晶体学 | 14篇 |
力学 | 129篇 |
综合类 | 2篇 |
数学 | 636篇 |
物理学 | 492篇 |
出版年
2023年 | 23篇 |
2022年 | 71篇 |
2021年 | 79篇 |
2020年 | 97篇 |
2019年 | 90篇 |
2018年 | 81篇 |
2017年 | 66篇 |
2016年 | 141篇 |
2015年 | 81篇 |
2014年 | 128篇 |
2013年 | 202篇 |
2012年 | 180篇 |
2011年 | 198篇 |
2010年 | 120篇 |
2009年 | 129篇 |
2008年 | 159篇 |
2007年 | 136篇 |
2006年 | 94篇 |
2005年 | 108篇 |
2004年 | 101篇 |
2003年 | 89篇 |
2002年 | 86篇 |
2001年 | 24篇 |
2000年 | 44篇 |
1999年 | 26篇 |
1998年 | 20篇 |
1997年 | 28篇 |
1996年 | 29篇 |
1995年 | 34篇 |
1994年 | 27篇 |
1993年 | 21篇 |
1992年 | 16篇 |
1991年 | 20篇 |
1990年 | 23篇 |
1989年 | 12篇 |
1988年 | 19篇 |
1987年 | 17篇 |
1986年 | 10篇 |
1985年 | 17篇 |
1984年 | 31篇 |
1982年 | 21篇 |
1981年 | 12篇 |
1980年 | 19篇 |
1979年 | 14篇 |
1978年 | 19篇 |
1977年 | 23篇 |
1976年 | 20篇 |
1975年 | 12篇 |
1974年 | 14篇 |
1973年 | 10篇 |
排序方式: 共有3072条查询结果,搜索用时 15 毫秒
111.
Yung-Sen Lin Tsung-Hsien Tsai Shih-Chan Hung Shih-Wei Tien 《Journal of Solid State Electrochemistry》2013,17(4):1077-1088
Enhanced lithium electrochromic performances of mixed organo-tungsten oxide (W x O y C z )/organo-molybdenum oxide (Mo x O y C z ) films by a rapid codeposition onto 40 Ω/□ flexible polyethylene terephthalate/indium tin oxide substrates at a short exposed duration of 23 s using an atmospheric pressure plasma jet (APPJ) at various mixed concentrations of hexacarbonyl precursors [W(CO)6 and Mo(CO)6] are investigated. The flexible organo-tungsten–molybdenum oxide (WMo x O y C z ) films demonstrated noteworthy electrochromic performance for 200 cycles of reversible Li+ ion intercalation and deintercalation in a 1 M LiClO4–propylene carbonate electrolyte by the switching measurements of potential sweep from ?1 to 1 V at a scan rate of 50 mV/s and the potential step at ?1 and 1 V, even after being bent 360o around a 2.5-cm diameter rod for 1,000 cycles. The optical modulation (ΔT) of 61.3 % for MoO y C z films at a wavelength of 795.6 nm was significantly improved up to 72.5 % for WMo x O y C z films cosynthesized with an APPJ. 相似文献
112.
α-n-amylcinnamaldehyde (jasminaldehyde) was obtained with 82 % yield by solid-liquid phase transfer catalysis without solvent within 3 days at room temperature. By use of domestic microwave irradiation, the same yield was obtained within 1 minute at a power of 600 W. 相似文献
113.
The aim of this paper is to control the rate of convergence for central limit theorems of sojourn times of Gaussian fields in both cases: the fixed and the moving level. Our main tools are the Malliavin calculus and the Stein method, developed by Nualart, Peccati and Nourdin. We also extend some results of Berman to the multidimensional case. 相似文献
114.
115.
Regioselective hydrolysis of cocaine led, according to the reaction conditions, either to benzoylecgonine or to ecgonine methyl ester. Acylation with benzoylecgonine was readily achieved when benzotriazolyloxytrisdimethylamino-phosphonium (BOP) was used as a coupling agent. 相似文献
116.
In the copolymerization of vinyl acetate (A) with either vinyl chloride (C) or vinylidene chloride (V), an internal transfer (backbiting) reaction—of the C- or V-ended radi-cals on an antepenultimate A unit—is proposed to be responsible for the deviation of the copolymerization kinetics from the Lewis and Mayo theory. The deviations disappear if A is replaced by isopropenylacetate [Ip], Then one gets, for the Ip -C copolymerization. rI p =0.35 and :rc=2.4, and for I -V copolymerization, rI p=0.13 and rv=5.9. The internal transfer reaction causes the formation of branches which may be evidenced by NMR analysis of constant composition suspension A-C copolymers. A kinetic scheme is proposed and the corresponding reactivity ratios derived rA=0.29, rc=1.60, r=0.3 (radical resulting from the transfer reaction), and kT=1500 (rate constant of the transfer reaction at 50°C). The distribution of branches is calculated together with the sequence distribution functions for the .A. or Cunits. 相似文献
117.
118.
119.
Redox‐responsive core cross‐linked micelles of poly(ethylene oxide)‐b‐poly(furfuryl methacrylate) by Diels‐Alder reaction for doxorubicin release
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)
Cuong M. Q. Le Hai Ha Pham Thi Xuan Thang Cao Gun‐Do Kim Chul‐Woong Oh Kwon Taek Lim 《Journal of polymer science. Part A, Polymer chemistry》2016,54(23):3741-3750
Redox‐responsive core cross‐linked (CCL) micelles of poly(ethylene oxide)‐b‐poly(furfuryl methacrylate) (PEO‐b‐PFMA) block copolymers were prepared by the Diels‐Alder click‐type reaction. First, the PEO‐b‐PFMA amphiphilic block copolymer was synthesized by the reversible addition‐fragmentation chain transfer polymerization. The hydrophobic blocks of PFMA were employed to encapsulate the doxorubicin (DOX) drug, and they were cross‐linked using dithiobismaleimidoethane at 60 °C without any catalyst. Under physiological circumstance, the CCL micelles demonstrated the enhanced structural stability of the micelles, whereas dissociation of the micelles took place rapidly through the breaking of disulfide bonds in the cross‐linking linkages under reduction environment. The core‐cross‐linked micelles showed fine spherical distribution with hydrodynamic diameter of 68 ± 2.9 nm. The in vitro drug release profiles presented a slight release of DOX at pH 7.4, while a significant release of DOX was observed at pH 5.0 in the presence of 1,4‐dithiothreitol. MTT assays demonstrated that the block copolymer did not have any practically cytotoxicity against the normal HEK293 cell line while DOX‐loaded CCL micelles exhibited a high antitumor activity towards HepG2 cells. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 3741–3750 相似文献
120.
Truong Son Pham Katalin Gönczi György Kardos Krisztina Süle László Hegedűs Mihály Kállay Miklós Kubinyi Pál Szabó Imre Petneházy László Tőke Zsuzsa Jászay 《Tetrahedron: Asymmetry》2013,24(24):1605-1614
Several cinchona based squaramide catalysts were applied to the asymmetric Michael addition of α-nitroethylphosphonates to acrylic acid aryl esters, resulting in high yields and enantioselectivities. The absolute configuration of one of the quaternary α-nitrophosphonate adducts was deduced from its experimental and calculated CD spectra. The adducts were reduced to their cyclic aminophosphonates by catalytic hydrogenation. 相似文献