全文获取类型
收费全文 | 802篇 |
免费 | 67篇 |
国内免费 | 44篇 |
专业分类
化学 | 569篇 |
晶体学 | 16篇 |
力学 | 16篇 |
综合类 | 8篇 |
数学 | 117篇 |
物理学 | 187篇 |
出版年
2023年 | 6篇 |
2022年 | 4篇 |
2021年 | 17篇 |
2020年 | 11篇 |
2019年 | 16篇 |
2018年 | 6篇 |
2017年 | 19篇 |
2016年 | 29篇 |
2015年 | 29篇 |
2014年 | 33篇 |
2013年 | 53篇 |
2012年 | 49篇 |
2011年 | 58篇 |
2010年 | 52篇 |
2009年 | 46篇 |
2008年 | 55篇 |
2007年 | 53篇 |
2006年 | 45篇 |
2005年 | 41篇 |
2004年 | 35篇 |
2003年 | 24篇 |
2002年 | 27篇 |
2001年 | 33篇 |
2000年 | 32篇 |
1999年 | 23篇 |
1998年 | 12篇 |
1997年 | 10篇 |
1996年 | 18篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1976年 | 2篇 |
1964年 | 1篇 |
排序方式: 共有913条查询结果,搜索用时 13 毫秒
1.
Rafael Caballero Mercedes González Flor M Guerrero Julián Molina Concepción Paralera 《European Journal of Operational Research》2007
In this work we present a multiobjective location routing problem and solve it with a multiobjective metaheuristic procedure. In this type of problem, we have to locate some plants within a set of possible locations to meet the demands of a number of clients with multiple objectives. This type of model is used to solve a problem with real data in the region of Andalusia (Spain). Thus, we study the location of two incineration plants for the disposal of solid animal waste from some preestablished locations in Andalusia, and design the routes to serve the different slaughterhouses in this region. This must be done while taking into account certain economic objectives (start-up, maintenance, and transport costs) and social objectives (social rejection by towns on the truck routes, maximum risk as an equity criterion, and the negative implications for towns close to the plant). 相似文献
2.
3.
4.
5.
F. J. Molina A. O. Vila C. Llcer M. J. Martos J. E. Figueruelo 《Journal of separation science》1991,14(9):590-592
Internal calibration in modified hydrodynamic chromatography has been realized by the approach of Prieve and Hoysan, i.e. the use of polystyrene monodisperse latexes to evaluate the equivalent capillary radius, R. The value obtained has been used to estimate the average sizes of a variety of liposome samples from egg yolk lecithin. 相似文献
6.
Guillermina L. Estiú Alicia H. Jubert Jos Molina Juan Costamagna Juan Canales Juan Vargas 《Journal of Molecular Structure》1995,330(1-3):201-210
Semiempirical self-consistent field (SCF) and configuration interaction (CI) calculations of the intermediate neglect of differential overlap (INDO) type are applied to the analysis of the electronic transitions of the hexaazacyclophane base and its Ni and Cu complexes. The ground states (1Ag for the ligand and Ni complex, 2B1g for the Cu complex) are planar structures of D2h symmetry. The low-energy region of the UV-visible spectra, whose analysis may help to recognize the catalytic active sites of the complexes is associated with d → d transitions in the Ni complex, and M → L charge transfer in the Cu complex. 相似文献
7.
A series of dimethyldihydropyrene derivatives was studied to elucidate the photochemical mechanism associated with the switching between the dimethyldihydropyrene (DHP, closed) and metacyclophanediene (CPD, open) forms of the molecule. Quantum yields of ring opening and closure, fluorescence quantum yields and lifetimes, as well as laser flash photolysis studies were performed to establish the effect of substituents on the switching efficiency. Ring opening of the DHPs occurs from the first singlet excited state. The low quantum yields for the ring opening reaction observed (< or =0.042) are a consequence of the low rate constant (< or =1.7 x 10(7) s(-1)) for this process. The quantum yields for ring closure of the CPD were determined for select compounds and were of the order of 0.1-0.4. These results show that the efficiency for ring opening of this class of compounds is intrinsically low, but can be modulated to some extent by the introduction of substituents. These properties should be taken into account when considering what type of photoswitching devices DHPs might be useful for. 相似文献
8.
M. P. Sánchez Sánchez J. M. Salas Peregrin M. A. Romero Molina 《Monatshefte für Chemie / Chemical Monthly》1987,118(8-9):883-891
Some news thiopyrimidine derivatives and complexes [4-amino-5-nitroso-6-oxo-1,2,3,6-tetrahydro-2-thio-pyrimidine (TANH), its 2-methylthio derivative (MTH), the ammonium salt ofTANH (sTANH) and six new complexes of formulas: Rh(MT)2Cl · 2H2O, Pd(MTH)2Cl2, Pt(MTH)2Cl4, Au(MTH)Cl3 Pd(TANH)2Cl2 and Au(TAN
–)Cl] have been synthesized and characterized by elemental analysis, IR and1H-NMR spectroscopy techniques. The thermal behaviour of all compounds has also been studied.
Rh(III), Pd(II), Pt(IV) und Au(III) Komplexe von 2-Thiopyrimidin Derivaten
Zusammenfassung Es wurden einige neue Thiopyrimidinderivate und deren Komplexe synthetisiert und mittels Elementaranalyse, IR und1H-NMR charakterisiert: 4-Amino-5-nitroso-6-oxo-1,2,3,6-tetrahydro-2-thio-pyrimidin (TANH), dessen 2-Methylthio-Derivat (MTH), das Ammoniumsalz vonTANH (sTANH) und sechs neue Komplexe der Formeln Rh(MT)2Cl · 2H2O, Pd(MTH)2Cl2, Pt(MTH)2Cl4, Au(MTH)Cl3, Pd(TANH)2Cl2 und Au(TAN –)Cl. Das thermische Verhalten der Verbindungen wurde ebenfalls untersucht.相似文献
9.
层状锑磷酸嵌接式卟啉锰制备与模拟细胞色素氧化催化研究 总被引:1,自引:0,他引:1
层状锑磷酸嵌接式卟啉锰制备与模拟细胞色素氧化催化研究胡希明,皮宗新,梅治乾,古国榜,黄仲涛(华南理工大学应用化学系,华南理工大学化学工程系,广州,510641)关键词卟啉锰,层状锑磷酸,嵌接,催化性能细胞色素P450是一种含血红素的单充氧化酶,在室温... 相似文献
10.
We give new sufficient conditions in order that a projective tensor product of Banach spaces contains complemented copies of ?1, which provides us new examples of this situation. 相似文献