全文获取类型
收费全文 | 21204篇 |
免费 | 2987篇 |
国内免费 | 1673篇 |
专业分类
化学 | 24157篇 |
晶体学 | 139篇 |
力学 | 158篇 |
综合类 | 68篇 |
数学 | 330篇 |
物理学 | 1012篇 |
出版年
2024年 | 22篇 |
2023年 | 301篇 |
2022年 | 615篇 |
2021年 | 737篇 |
2020年 | 1388篇 |
2019年 | 1111篇 |
2018年 | 937篇 |
2017年 | 793篇 |
2016年 | 1401篇 |
2015年 | 1203篇 |
2014年 | 1249篇 |
2013年 | 1670篇 |
2012年 | 1446篇 |
2011年 | 1253篇 |
2010年 | 1067篇 |
2009年 | 1142篇 |
2008年 | 1151篇 |
2007年 | 1072篇 |
2006年 | 982篇 |
2005年 | 882篇 |
2004年 | 882篇 |
2003年 | 714篇 |
2002年 | 1343篇 |
2001年 | 344篇 |
2000年 | 281篇 |
1999年 | 302篇 |
1998年 | 313篇 |
1997年 | 228篇 |
1996年 | 171篇 |
1995年 | 159篇 |
1994年 | 96篇 |
1993年 | 60篇 |
1992年 | 82篇 |
1991年 | 58篇 |
1990年 | 60篇 |
1989年 | 39篇 |
1988年 | 42篇 |
1987年 | 27篇 |
1986年 | 72篇 |
1985年 | 19篇 |
1984年 | 16篇 |
1983年 | 13篇 |
1981年 | 10篇 |
1980年 | 13篇 |
1979年 | 12篇 |
1978年 | 12篇 |
1973年 | 8篇 |
1972年 | 11篇 |
1970年 | 7篇 |
1966年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Jesús Vázquez 《Tetrahedron letters》2006,47(10):1657-1661
Use of a semicarbazide resin for the solid-phase preparation of peptide ketones and aldehyde led to optimal results in terms of both purity of the final product and overall yield. This resin was prepared without complication by activation of the commercial available aminomethyl polystyrene with CDI at room temperature, followed by treatment with tert-butyl carbazate. Furthermore, the TNBSA colorimetric assay has been adapted for checking the incorporation of the carbonyl moiety onto hydrazine-based resins. 相似文献
42.
关新民 《新疆大学学报(理工版)》2002,19(1):95-99
介绍了采用MATLAB V5.2提供的模糊逻辑工具箱来设计研究电孤纺电极调节系统中的模糊--PD控制器,讨论了在SIMULINK环境下模糊-PD控制器的参数自调速原理、结构、建立模糊控制规则库和模糊推论方法,并给出仿真结果与结论。 相似文献
43.
Marcelino Maneiro Manuel R. Bermejo M. Isabel Fernndez Ana M. Gonzlez‐Noya Alexei M. Tyryshkin Robin G. Pritchard 《无机化学与普通化学杂志》2003,629(2):285-290
A new MnIII‐Schiff base complex, [MnL(OH2)](ClO4) ( 1 ) (H2L = N, N′‐bis‐(3‐Br‐5‐Cl‐salicylidene)‐1, 2‐diimino‐2‐methylethane), an inorganic model of the catalytic center (OEC, Oxygen Evolving Complex) in photosystem II (PSII), has been synthesized and characterized by elemental analysis, IR and EPR spectroscopy, mass spectrometry, magnetic susceptibility measurement and the study of its redox properties by cyclic and normal pulse voltammetry. This complex mimics reactivity (showing a relevant photolytic activity), and also some structural characteristics (parallel‐mode MnIII EPR signal from partially assembled OEC cluster) of the natural OEC. The complex 1 was found to rearrange in solution into a crystallographically solved square‐pyramidal complex, [MnLL′] ( 2 ) (HL′ = 6‐bromo‐4‐chloro‐2‐cyanophenol), through a process, which probably liberates radical species (detected by EPR), and provokes a C—N bond cleavage in the ligand. A photo‐radical mechanism is discussed to explain this rearrangement. 相似文献
44.
45.
46.
Employing a cleavable carbohydrate–peptide linker, a new strategy for single-bead analysis of multivalent cyclic neoglycopeptides based on Edman degradation is described. Edman degradation of glycopeptides is hampered by the acid lability of the glycosidic bond and potential incompatibilities of phenylthiohydantoin (PTH) derivatives of glycosylated amino acids with PTH derivatives of the proteinogenic amino acids. To overcome this problem, carbohydrates are detached from the cyclopeptide templates before single-bead analysis, allowing for micro sequencing under routine conditions. With this strategy, application of multivalent cyclic neoglycopeptides in split-mix libraries with a subsequent screening process becomes possible for the first time. 相似文献
47.
48.
49.
Using radical chemistry novel highly condensed heterocycles have been synthesized. The mechanism for their formation is discussed. 相似文献
50.
Thorsten Brand Kyle Ratinac Jeffrey V. Castro Robert G. Gilbert 《Journal of polymer science. Part A, Polymer chemistry》2004,42(22):5706-5713
A method was developed for free‐radical polymerization in the confines of a hollow latex particle. Hollow particles were prepared via the dynamic swelling method from polystyrene seed and divinylbenzene and had hollows of 500–1000 nm. So that these hollow poly(divinylbenzene) particles could function as submicrometer reactors, the particles were filled with a monomer (N‐isopropylacrylamide) via the dispersion of the dried particles in the molten monomer. The monomer that was not contained in the hollows was removed by washing and gentle abrasion. Free‐radical polymerization was then initiated by γ radiolysis in the solid state. Transmission electron microscopy showed that poly(N‐isopropylacrylamide) formed in the hollow interior of the particles, which functioned as submicrometer reactors. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5706–5713, 2004 相似文献