全文获取类型
收费全文 | 1194篇 |
免费 | 47篇 |
国内免费 | 7篇 |
专业分类
化学 | 828篇 |
晶体学 | 12篇 |
力学 | 35篇 |
数学 | 140篇 |
物理学 | 233篇 |
出版年
2024年 | 5篇 |
2023年 | 12篇 |
2022年 | 33篇 |
2021年 | 27篇 |
2020年 | 26篇 |
2019年 | 29篇 |
2018年 | 39篇 |
2017年 | 21篇 |
2016年 | 53篇 |
2015年 | 34篇 |
2014年 | 42篇 |
2013年 | 100篇 |
2012年 | 70篇 |
2011年 | 87篇 |
2010年 | 50篇 |
2009年 | 56篇 |
2008年 | 93篇 |
2007年 | 74篇 |
2006年 | 76篇 |
2005年 | 71篇 |
2004年 | 43篇 |
2003年 | 36篇 |
2002年 | 27篇 |
2001年 | 5篇 |
2000年 | 10篇 |
1998年 | 11篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1994年 | 8篇 |
1992年 | 4篇 |
1991年 | 9篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 5篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1967年 | 2篇 |
1963年 | 2篇 |
排序方式: 共有1248条查询结果,搜索用时 11 毫秒
51.
Siddiqui Madiha M. Nagargoje Amol A. Akolkar Satish V. Sangshetti Jaiprakash N. Khedkar Vijay M. Pisal Parshuram M. Shingate Bapurao B. 《Research on Chemical Intermediates》2022,48(3):1199-1225
Research on Chemical Intermediates - A simple and efficient protocol has been developed for the synthesis of new1,2,3-triazole-2,3-dihydroquinazolin-4[1H]-one (DHQ) conjugates(6a?j) via... 相似文献
52.
Anshu Dandia Dinesh Kumar Mahawar Ruchi Sharma Ranveer Singh Badgoti Kuldeep S. Rathore Vijay Parewa 《应用有机金属化学》2019,33(11)
Graphene oxide (GO)‐catalyzed selective synthesis of amides via CSp3–H activation of methylarenes and consequent C–N bond formation with anilines under aqueous medium has been described. Oxygen functionality allied with GO surface played a dual role both as acid catalyst and oxidizing agent to some extent. However, GO has a copious effect on the reaction, shown by a high TOF value with TBHP as co‐oxidant. The decisive role of carboxylic acid functional groups on GO nanosheets in this metal‐free strategy has been confirmed and was monitored by various analytic techniques viz. Fourier transform‐infrared, UV–Vis, Raman and XPS. A plausible mechanism was proposed by control experiments and by the isolation of the intermediate. Over‐oxidation of methylarenes was not detected, and high recyclability of the carbocatalyst with its heterogeneous behavior facilitated the isolation and purification of the desired products. We have further explored the utility of this process for the chemoselective synthesis of benzimidazoles. 相似文献
53.
Vijay Balasubramanian 《Foundations of Physics》2013,43(1):101-114
String theory has transformed our understanding of geometry, topology and space-time. Thus, for this special issue of Foundations of Physics commemorating “Forty Years of String Theory”, it seems appropriate to step back and ask what we do not understand. As I will discuss, time remains the least understood concept in physical theory. While we have made significant progress in understanding space, our understanding of time has not progressed much beyond the level of a century ago when Einstein introduced the idea of space-time as a combined entity. Thus, I will raise a series of open questions about time, and will review some of the progress that has been made as a roadmap for the future. 相似文献
54.
55.
56.
S. Vijay Kumar T. E. Musturappa S. Prasannakumar K. M. Mahadevan 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(11):1161-1169
Free radical copolymerization of N‐vinyl‐2‐pyrrolidone with 2‐ethoxyethyl methacrylates was carried out with 2,2′‐azobisisobutyronotrile as an initiator in 1,4‐dioxane. The resulting copolymer was characterized by FTIR, H1‐NMR and C13‐NMR spectroscopic techniques thermal properties of copolymer were determined by DSC and TGA. The reactivity ratios of the monomers were computed by the Fineman‐Rose (F‐R), Kelen‐Tudos (K‐T) and extended Kelen‐Tudos (EK‐T) method at lower conversion, using the data obtained from both FTIR and elemental analysis studies; the results are in good agreement with each other. The average reactivity ratio, Alfrey‐Price Q and e values were found to be r 1=0.769, r 2=0.266 and Q 1=0.0859, e 1=0.4508, respectively for NVP/EOEMA copolymer. The distribution of monomer sequence along the copolymer chain was calculated using a statistical method based on obtained reactivity ratio. The number average molecular weight and polydispersity were determined by GPC. 相似文献
57.
58.
The O-glycosidation reaction of 1-O-acetyl-2,3-dideoxy-DL-pent-2-enopyran - 4 -ulose catalysed by the environmentally accepted and inexpensive industrial catalyst Montmorillonite K-10 clay with variety of alcohols in high yield is reported. 相似文献
59.
A simple, efficient, and diastereoselective synthesis of 5-methylene-dihydropyran-2,6-diones and 3-methylene-3,4-dihydropyran-2-ones from substrates afforded by the SN2 reaction between the acetyl derivatives of the Baylis–Hillman adducts and methylacetoacetate or acetylacetone or benzoyl acetone via saponification followed by P2O5-mediated cyclization is described. 相似文献
60.
Limin Liu Sichu Li Blake Simmons Mohit Singh Vijay T. John Gary L. McPherson 《Journal of Dispersion Science and Technology》2013,34(1-3):441-452
The mixed surfactant system of bis (2-ethylhexyl) sodium sulfosuccinate (AOT) and α-phosphatidylcholine (lecithin) forms a rigid gel-like mesophase in the presence of equal volumes of water and a hydrocarbon (isooctane). Small angle neutron scattering (SANS) results indicate that these structures undergo transitions from columnar hexagonal geometries to lamellar geometries depending on the water content and/or the temperature. The system is used to synthesize nanostructured ceramics (silica) in the aqueous microphase. Interpenetrating networks of poly-(hydroxyethylmethacrylate) and poly(styrene) are also synthesized using the aqueous microphase to support the water soluble monomer (hydroxyethyl methacrylate) and the organic microphase (styrene). SANS results indicate that the template structure is maintained during materials synthesis. 相似文献