全文获取类型
收费全文 | 1733篇 |
免费 | 118篇 |
国内免费 | 27篇 |
专业分类
化学 | 1200篇 |
晶体学 | 11篇 |
力学 | 70篇 |
综合类 | 2篇 |
数学 | 292篇 |
物理学 | 303篇 |
出版年
2023年 | 11篇 |
2022年 | 35篇 |
2021年 | 37篇 |
2020年 | 48篇 |
2019年 | 44篇 |
2018年 | 32篇 |
2017年 | 28篇 |
2016年 | 82篇 |
2015年 | 57篇 |
2014年 | 79篇 |
2013年 | 111篇 |
2012年 | 120篇 |
2011年 | 140篇 |
2010年 | 73篇 |
2009年 | 96篇 |
2008年 | 102篇 |
2007年 | 87篇 |
2006年 | 65篇 |
2005年 | 76篇 |
2004年 | 71篇 |
2003年 | 71篇 |
2002年 | 61篇 |
2001年 | 17篇 |
2000年 | 32篇 |
1999年 | 14篇 |
1998年 | 10篇 |
1997年 | 16篇 |
1996年 | 19篇 |
1995年 | 19篇 |
1994年 | 17篇 |
1993年 | 12篇 |
1992年 | 10篇 |
1991年 | 15篇 |
1990年 | 14篇 |
1989年 | 4篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1984年 | 20篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1974年 | 10篇 |
1973年 | 6篇 |
1972年 | 5篇 |
1970年 | 3篇 |
排序方式: 共有1878条查询结果,搜索用时 28 毫秒
71.
For a group G,we produce upper and lower bounds for the sum of the entries of the Brauer character table of G and the projective indecomposable character table of G.When G is a π-separable group,we show that the sum of the entries in the table of Isaacs' partial characters is a real number,and we obtain upper and lower bounds for this sum. 相似文献
72.
Identification and formation mechanism of individual degradation products in lithium‐ion batteries studied by liquid chromatography/electrospray ionization mass spectrometry and atmospheric solid analysis probe mass spectrometry 下载免费PDF全文
73.
74.
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
75.
76.
77.
78.
Hou Chien Chang Ching Hsuan Lin Hung Tse Lin Shenghong A. Dai 《Journal of polymer science. Part A, Polymer chemistry》2012,50(5):1008-1017
Generally, protection and deprotection procedures of amino groups are required in preparing propargyl ether‐containing benzoxazines. In this study, we report a facile, deprotection‐free preparation of a propargyl ether‐containing phosphinated benzoxazine (2) from the nucleophilic substitution of a phenolic OH‐containing phosphinated benzoxazine (1) and propargyl bromide in the catalysis of potassium carbonate. The structure of (2) was characterized and confirmed by a high‐resolution mass spectrum, 1H, 13C, 1H‐1H, 1H‐13C nuclear magnetic resonance (NMR) spectra, and X‐ray single crystal diffractogram. infrared (IR) and differential scanning calorimetry were used to monitor the ring‐opening of benzoxazine and crosslinking of propargyl ether. The microstructure and the structure–property relationship of the resulting homopolymers and copolymers are discussed. The Tg of homopolymer of (2) is 208 °C by dynamic mechanical analysis, the coefficient of thermal expansion is 43 ppm/°C, and Td 5% (N2) is 393 °C, respectively, which are higher than those of the homopolymer of (1) . Similar trends were observed in the copolymerization system. The results demonstrate the beneficial effect of crosslinking afforded by the propargyl ether group is higher than that by the phenolic OH group. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
79.
Ly Dieu Ha Poul Erik Hansen Fritz Duus Hung Dinh Pham Lien‐Hoa D. Nguyen 《Magnetic resonance in chemistry : MRC》2012,50(3):242-245
Four new prenylated depsidones, oliveridepsidones A–D, were isolated from the bark of Garcinia oliveri collected in Vietnam. Their structures were elucidated using mainly NMR techniques (1H and 13C NMR, HMQC, HMBC and NOE experiments). Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
80.
Hsu‐Feng Lee Po‐Hsun Wang Yi‐Chiang Huang Wen‐Hung Su Ram Gopal Chun Che Lee Steven Holdcroft Wen‐Yao Huang 《Journal of polymer science. Part A, Polymer chemistry》2014,52(18):2579-2587
A series of sterically‐encumbered, sulfonated, poly(arylene ether) copolymers were synthesized and their proton conductivity examined. The series was prepared by copolymerizing a novel monomer, 2″,3″,5″,6″‐tetraphenyl‐[1,1′:4',1″:4″,1″':4″',1″″‐quinquephenyl]‐4,4″″‐diol, with 4,4'‐difluorobenzophenone and bisphenol A. Subsequent sulfonation and solution casting provided membranes possessing ion exchange capacities of 1.9 to 2.7 mmol/g and excellent mechanical properties (Young's modulus, 0.2–1.2 GPa; tensile strength, 35–70 MPa; elongation at break, 62–231%). Water uptake ranged from 34 to 98 wt% at 80 °C/100% RH. Proton conductivities ranged between 0.24 to 16 mS/cm at 80 °C/60% RH, and 3 to 167 mS/cm at 80 °C/95% RH. TEM analysis of the polymers, in the dehydrated state, revealed isolated spherical aggregates of ions, which presumably coalesce when hydrated to provide highly conductive pathways. The strategy of using highly‐encumbered polymer frameworks for the design of mechanically‐robust and dimensionally‐stable proton conducting membranes is demonstrated. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 2579‐2587 相似文献