全文获取类型
收费全文 | 637篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
化学 | 519篇 |
晶体学 | 3篇 |
力学 | 7篇 |
数学 | 49篇 |
物理学 | 70篇 |
出版年
2023年 | 4篇 |
2022年 | 15篇 |
2021年 | 14篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 13篇 |
2017年 | 12篇 |
2016年 | 17篇 |
2015年 | 10篇 |
2014年 | 15篇 |
2013年 | 22篇 |
2012年 | 27篇 |
2011年 | 35篇 |
2010年 | 30篇 |
2009年 | 23篇 |
2008年 | 41篇 |
2007年 | 32篇 |
2006年 | 40篇 |
2005年 | 29篇 |
2004年 | 32篇 |
2003年 | 22篇 |
2002年 | 14篇 |
2001年 | 15篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1992年 | 5篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 12篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 11篇 |
1972年 | 4篇 |
1970年 | 3篇 |
1968年 | 3篇 |
排序方式: 共有648条查询结果,搜索用时 328 毫秒
51.
Daroui-Mokaddem H Kabouche A Bouacha M Soumati B El-Azzouny A Bruneau C Kabouche Z 《Natural product communications》2010,5(10):1669-1672
The essential oils of fresh leaves of Eucalyptus globulus L. (Myrtaceae), and leaves and stems of Smyrnium olusatrum L. (Apiaceae), obtained by hydrodistillation in a Clevenger-type apparatus, were analyzed by GC/MS. Twenty compounds were characterized, representing 98.3% of the essential oil of E. globulus, with 1,8-cineole (48.6%), globulol (10.9%), trans-pinocarveol (10.7%), and alpha-terpineol (6.6%) as main components, while thirty-three compounds were characterized, representing 94.3% of the essential oil of S. olusatrum, with sabinene (27.1%), curzerene (13.7%), methyl-1-benzyl-2-oxocyclooctane carboxylate (12.3%), alpha-pinene (7.2%), cryptone (7.1%) and beta-pinene (5.7%) as the major components. The essential oils of E. globulus and S. olusatrum were tested against a wide range of fungal and bacterial strains. Both oils showed significant antimicrobial activity. 相似文献
52.
Irena Akhrem Dzhul’etta Avetisyan Lyudmila Afanas’eva Nikolai Kagramanov Pavel Petrovskii Alexander Orlinkov 《Tetrahedron letters》2010,51(6):907-911
A novel ‘alkane-like’ methodology for the direct and very simple one-pot functionalization of amides and an ester of 1-adamantanecarboxylic acid provides access to new and synthetically challenging 1,3-dicarbonyl-containing adamantanoid compounds with the same or different functional groups. 相似文献
53.
Aida Toma 《Comptes Rendus Mathematique》2013,351(7-8):311-316
We consider new classes of estimators and test statistics for models satisfying linear constraints with unknown parameter. These procedures are based on minimization of divergences through duality techniques. We prove that, for various divergences, the new approach provides robust estimation and test procedures, unlike the empirical likelihood method. We give general results using the influence function approach, which we exemplify in detail in the case of the Cressie–Read divergences. It is found that the Hellinger distance is one of the divergences that leads to robust procedures. 相似文献
54.
55.
56.
57.
58.
Aida Isabel Tavares 《Computational & Mathematical Organization Theory》2017,23(2):199-220
Generic substitution policy has been adopted in several countries in order to control health expenditures. Using a model based on incentives, this work aims to analyze the response of doctors and pharmaceutical companies to the implementation of this policy. It is shown that after the implementation of GSP, the effort of doctor’s convincing the patient to take generics increase or decrease depending on his level of concern for patient well-being; pharmaceutical companies decrease the amount of detailing and the market share of generics tends to increase. 相似文献
59.
60.
Abdolreza Rezaeifard Maasoumeh Jafarpour Heidar RaissiEbrahim Ghiamati Aida Tootoonchi 《Polyhedron》2011,30(4):592-598
The oxidation of aryl sulfides by tetra-n-butylammonium peroxomonosulfate (n-Bu4NHSO5) was carried out in the presence of six different manganese (III) tetraarylporphyrins [Mn(Por)s] as biomimetic catalysts and a number of nitrogen donors as co-catalysts. There is no noticeable difference between the reactivity of sulfides, in the presence of electron-rich Mn(por)s, whereas, for electron-deficient catalysts, conversion rates are different. Nevertheless, the over-oxidation of sulfoxide is more sensitive to both the nature of substituents attached to the sulfur atom in substrates as well as porphyrin complex structure. The degree of catalytic activity of Mn(Por)s for the formation of sulfone product increases as the following order: Mn(TPFPP)OAc < Mn[T(4-NO2P)P]OAc < Mn(TDCPP)OAc < Mn(TPP)OAc < Mn(TMP)OAc < Mn[T(4-OMeP)P]OAc. Our results show that in the presence of electron-rich Mn(Por)s, the strong π-donor N-H imidazoles possess co-catalytic activity greater than that of strong σ-donor amines and weak π-donor pyridines. When electron-deficient Mn(Por)s were employed as catalyst, pyridines demonstrated a higher co-catalytic activity than that of N-H imidazoles. The pronounced effect of protic solvents on the rate and selectivity of oxidation reactions, particularly in the presence of electron-deficient Mn(Por)s has been observed. The outcome of our investigations accompanied by UV-Vis and Raman spectral data confirms the involvement of different active oxidant such as a high valent Mn-oxo species as well as a six-coordinate [(L)(Por)Mn-OHSO4] complex. 相似文献