全文获取类型
收费全文 | 629篇 |
免费 | 17篇 |
专业分类
化学 | 516篇 |
晶体学 | 8篇 |
力学 | 23篇 |
数学 | 50篇 |
物理学 | 49篇 |
出版年
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 10篇 |
2020年 | 15篇 |
2019年 | 12篇 |
2018年 | 4篇 |
2017年 | 4篇 |
2016年 | 15篇 |
2015年 | 11篇 |
2014年 | 14篇 |
2013年 | 31篇 |
2012年 | 31篇 |
2011年 | 36篇 |
2010年 | 18篇 |
2009年 | 20篇 |
2008年 | 36篇 |
2007年 | 36篇 |
2006年 | 30篇 |
2005年 | 29篇 |
2004年 | 33篇 |
2003年 | 28篇 |
2002年 | 36篇 |
2001年 | 9篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 16篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 17篇 |
1979年 | 11篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1969年 | 2篇 |
1934年 | 1篇 |
排序方式: 共有646条查询结果,搜索用时 0 毫秒
601.
Luigia Sabbatini Cosimino Malitesta Gemme Morea Luise Torsi Pier G. Zambonin 《Mikrochimica acta》1991,104(1-6):237-243
The potential of a complementary use of X-ray photoelectron spectroscopy and static ToF-SIMS has been exploited with reference to the characterization of electron conducting polymers (polybithiophene) electrochemically synthetized. Particular attention has been focused on the problem of material stability under electrochemical switching.A coherent picture could be drawn showing that irreversible modifications of the surface chemistry occur, strongly dependent on the dryness of the solvent; moreover, the pathway of doping-undoping process can vary noticeably in dependence on the experimental conditions. 相似文献
602.
The use of polystyrene-based anion exchangers with aqueous eluents for the separation of primary aromatic amines has been investigated, and extended with satisfactory results to microcrystalline cellulose, cellulose-based anion-exchangers and sodium CM-cellulose layers.Interesting separations of the amines have also been effected electrophoretically on AG 1-X4 layers.The use of water-organic solvent mixtures on polystyrene-based cation exchangers is discussed. 相似文献
603.
Marengo E Robotti E Cecconi D Hamdan M Scarpa A Righetti PG 《Analytical and bioanalytical chemistry》2004,379(7-8):992-1003
In this paper, principal component analysis (PCA) is applied to a spot quantity dataset comprising 435 spots detected in 18 samples belonging to two different cell lines (Paca44 and T3M4) of control (untreated) and drug-treated pancreatic ductal carcinoma cells. The aim of the study was the identification of the differences occurring between the proteomic patterns of the two investigated cell lines and the evaluation of the effect of the drug Trichostatin A on the protein content of the cells. PCA turned out to be a successful tool for the identification of the classes of samples present in the dataset. Moreover, the loadings analysis allowed the identification of the differentially expressed spots, which characterise each group of samples. The treatment of both the cell lines with Trichostatin A therefore showed an appreciable effect on the proteomic pattern of the treated samples. Identification of some of the most relevant spots was also performed by mass spectrometry. 相似文献
604.
Pontoglio A Viganò A Sebastiano R Citterio A Maragnoli L Righetti PG Gelfi C 《Electrophoresis》2004,25(7-8):1065-1070
Two compounds, derivatives of 1,4-diazobicyclo[2,2,2]octane (DABCO), have been evaluated as potential quenchers of silanol interactions with peptides and proteins during their capillary zone electrophoresis (CZE) separations. They are: 1-(4-iodobutyl)4-aza-1-azoniabicyclo[2,2,2]octane iodide (M7C4I) and 1,4-didecyl-1,4-diazoniabicyclo [2,2,2]octane dibromide (C10M7C10). The first compound is known to react with the wall, by forming a covalent bond via alkylation of silanols. On the contrary, the second one (C10M7C10) can only loosely interact with silica due to lack of reactive iodine and to a much too short distance (a C(2)) between the two quaternary nitrogens. Very good peptide maps of protein digests can be obtained in isoelectric glutamic acid (Glu) buffer, at pH 3.52 by utilizing the M7C4I. However, in the case of total tissue extracts, excellent resolution is obtained only with the first eluting part of the analyte spectrum (i.e., peptides and smaller proteins). With larger proteins, interaction with the wall and loss of resolution is experienced. When using the C10M7C10, good resolution of di- and tripeptides is obtained, while a loss of resolution is observed with entire protein digest. M7C4I does not seem to interact with the peptide/protein analytes, and simply repels them from the wall via its positive charges; it is believed that disalt (C10M7C10) acts by interacting with the same compounds, possibly by forming micelles in solution. 相似文献
605.
Solinas M Pfaltz A Cozzi PG Leitner W 《Journal of the American Chemical Society》2004,126(49):16142-16147
The enantioselective hydrogenation of N-(1-phenylethylidene)aniline using cationic iridium complexes with chiral phosphinooxazoline ligands was studied as a chemical probe to assess the potential of ionic liquid/carbon dioxide (IL/CO2) media for, multiphase catalysis. The biphasic system leads to activation, tuning, and immobilization of the catalyst that would be impossible in classical organic solvent systems or in either of the two unconventional media separately. In particular it is demonstrated that (i) the presence of CO2 can be beneficial or even mandatory for efficient hydrogenation in the IL; (ii) the precursor is activated in the IL by anion exchange allowing one to use in situ catalysts; (iii) the anion of the IL greatly influences the selectivity of the catalyst; (iv) the products are readily isolated from the catalyst solution by CO2 extraction without cross contamination of IL or catalyst; and (v) the IL leads to enhanced stability of the catalyst. These results are corroborated and rationalized on the basis of the physicochemical properties of the biphasic medium and the chemical characteristics of the catalytic systems. 相似文献
606.
607.
608.
609.
610.
Pier G. Daniele Giorgio Ostacoli Orfeo Zerbinati Silvio Sammartano Alessandro De Robertis 《Transition Metal Chemistry》1988,13(2):87-91
Summary A thermodynamic study of CuII–MII-citrate (MII=NiII, ZnII or CdII) ternary systems has been performed by means of potentiometric measurements of hydrogen ion concentration at different temperatures (10, 25, 35 and 45°C) and at I=0.1 mol dm–3 (KNO3).The different binary and ternary systems involved have been further characterized by visible spectra and by calculating the spectra ( versus ) of all the CuII complexes.The thermodynamic data suggest strong entropic stabilization for the species under discussion. As regards the visible spectral characteristics of CuII(d-d transitions), the substitution of one CuII ion in the dimer [Cu2(cit)2H–2]4– by NiII or ZnII to form heterobinuclear [CuM(cit)2H–2]4– complexes, gives rise to a change in the visible spectrum. 相似文献