全文获取类型
收费全文 | 383篇 |
免费 | 18篇 |
国内免费 | 3篇 |
专业分类
化学 | 237篇 |
晶体学 | 2篇 |
力学 | 2篇 |
数学 | 58篇 |
物理学 | 105篇 |
出版年
2023年 | 2篇 |
2022年 | 5篇 |
2021年 | 3篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2016年 | 9篇 |
2015年 | 11篇 |
2014年 | 11篇 |
2013年 | 20篇 |
2012年 | 19篇 |
2011年 | 20篇 |
2010年 | 20篇 |
2009年 | 12篇 |
2008年 | 13篇 |
2007年 | 19篇 |
2006年 | 18篇 |
2005年 | 17篇 |
2004年 | 11篇 |
2003年 | 13篇 |
2002年 | 12篇 |
2001年 | 16篇 |
2000年 | 20篇 |
1999年 | 17篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 15篇 |
1993年 | 8篇 |
1992年 | 9篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1960年 | 1篇 |
1938年 | 1篇 |
1932年 | 2篇 |
排序方式: 共有404条查询结果,搜索用时 15 毫秒
91.
92.
G. Gallego Ferrer M. Salmerón Sánchez J.L. Gómez Ribelles F.J. Romero Colomer 《European Polymer Journal》2007,43(8):3136-3145
The morphology of a series of hydrogels based on the interpenetration of poly(2-hydroxyethyl acrylate) and poly(ethyl acrylate) has been studied through transmission electron microscopy, TEM, atomic force microscopy, AFM, and dynamic-mechanical spectroscopy, DMA. For the TEM analysis phosphotungstic acid, PTA, was used as alternative selective staining agent to those commonly used. The good agreement between TEM and AFM images allowed us to confirm that the PTA technique is a very powerful tool for TEM analysis of these hydrogel systems. All the results show that the IPNs presented phase-separation with two kinds of microdomains: those preferentially with a hydrophilic nature and those with preferentially a hydrophobic one, of sizes that range from 30 nm to 100 nm. Each one of these domains is composed by smaller nanodomains of alternating hydrophobic and hydrophilic component ranging between 6 and 10 nm sizes, those preferentially with a hydrophilic nature having a larger proportion of hydrophilic nanodomains. The AFM images of the IPN with the highest PHEA mass fraction, xPHEA = 0.75, suggest that the hydrophilic phase is co-continuous in the material. A disperse hydrophilic phase is found when the PHEA mass fraction is reduced up to xPHEA = 0.38. This phase-separation is explained in terms of some characteristic parameters of the networks such as the mesh size and the number of units between cross-links. The morphology found makes the systems very attractive for cell adhesion substrates and for matrices of scaffolds in soft tissue engineering. 相似文献
93.
A micellar electrokinetic capillary chromatographic method is presented which enables quantification of dexamethasone, polymyxin B and trimethoprim in synthetic mixtures and pharmaceutical products. Separation was carried out at 25?°C and 30 kV, with 10 mmol L–1 borate–phosphate buffer adjusted to pH 8 as electrolyte, with 50 mmol L–1 sodium dodecyl sulfate. Under these conditions separations were performed in 10 min. The limits of detection and quantification were approximately 2 mg L–1 for each component, except for polymyxin B. The method was applied to different commercial formulations. 相似文献
94.
Santiago Gómez-Ruiz Beatriz Gallego Željko Žižak Evamarie Hey-Hawkins Zorica D. Juranić Goran N. Kaluđerović 《Polyhedron》2010
Four titanium(IV) carboxylate complexes [Ti(η5-C5H5)2(O2CCH2SMes)2] (1), [Ti(η5-C5H4Me)2(O2CCH2SMes)2] (2), [Ti(η5-C5H5)(η5-C5H4SiMe3)(O2CCH2SMes)2] (3) and [Ti(η5-C5Me5)(O2CCH2SMes)3] (4; Mes = 2,4,6-Me3C6H2) have been synthesised by the reaction of the corresponding titanium derivatives [Ti(η5-C5H5)2Cl2], [Ti(η5-C5H4Me)2Cl2], [Ti(η5-C5H5)(η5-C5H4SiMe3)Cl2] and [Ti(η5-C5Me5)Cl3] and two (for 1–3) or three (for 4) equivalents of mesitylthioacetic acid. Complexes 1–4 have been characterized by spectroscopic methods and the molecular structure of the complexes 1, 2 and 4 have been determined by X-ray diffraction studies. The cytotoxic activity of 1–4 was tested against tumor cell lines human adenocarcinoma HeLa, human myelogenous leukemia K562, human malignant melanoma Fem-x, and normal immunocompetent cells, that is peripheral blood mononuclear cells PBMC and compared with those of the reference complexes [Ti(η5-C5H5)2Cl2] (R1), [Ti(η5-C5H4Me)2Cl2] (R2), [Ti(η5-C5H5)(η5-C5H4SiMe3)Cl2] (R3) and cisplatin. In all cases, the cytotoxic activity of the carboxylate derivatives was higher than that of their corresponding dichloride analogues, indicating a positive effect of the carboxylato ligand on the final anticancer activity. Complexes 1–4 are more active against K562 (IC50 values from 72.2 to 87.9 μM) than against HeLa (IC50 values from 107.2 to 142.2 μM) and Fem-x cells (IC50 values from 90.2 to 191.4 μM). 相似文献
95.
Daniel Pellico Mar Gómez‐Gallego Prof. Pedro Ramírez‐López Dr. María José Mancheño Prof. Miguel A. Sierra Prof. M. Rosario Torres Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(5):1592-1600
A novel approach for the synthesis of macrocyclic bis‐β‐lactams based on the Cu‐catalyzed alkyne–azide cycloaddition (CuAAC) is reported. The procedure is general and allows access to a full range of diastereomerically or enantiomerically pure macrocyclic cavities in good yields. The incorporation of chiral oxazolidinone fragments at C3 in the β‐lactam rings allows the total enantiocontrol of the process. 相似文献
96.
97.
Epithelial cell lines from several tissues show a differential sensitivity to Pseudomonas aeruginosa adherence. A549 (lung), HepG2 (liver) and Caco-2 (colon) cells presented an adhesion index of about 3, 1.5 and 5 CFU/cell, respectively, whereas Mz-Ch cell lines (gallbladder cholangiocytes) presented adhesion indexes up to 35. These variations could be associated with the variable amount of sialic acid in cell surface glycoconjugates. Moreover, the presence of free sialic acid in culture media induces the secretion by P. aeruginosa of a sialidase which is able to hydrolyze glycoconjugate-linked sialic acid. As shown with A549 cells, this specific hydrolysis increases bacterial adhesion, probably by unmasking new binding sites onto the cell surface. 相似文献
98.
We propose a new mechanism for surface-induced magnetic anisotropy to explain the thickness dependence of the Kondo resistivity of thin films of dilute magnetic alloys. The surface anisotropy energy, generated by spin-orbit coupling on the magnetic impurity itself, is an oscillating function of the distance d from the surface and decays as 1/d2. Numerical estimates based on simple models suggest that this mechanism, unlike its alternatives, gives rise to an effect of the desired order of magnitude. 相似文献
99.
Fandos R Gallego B Otero A Rodríguez A Ruiz MJ Terreros P Pastor C 《Dalton transactions (Cambridge, England : 2003)》2006,(22):2683-2690
The new titanium dicarboxylate complex Cp*TiMe(OOC)2py (2) [Cp*=eta5-C5Me5; (OOC)2py = 2,6-pyridinedicarboxylate] has been synthesized. The reaction of complex 2 with water renders [Cp*Ti(OOC)2py]2O (3). The molecular structure of 3 has been studied by X-ray diffraction methods. Complex 2 reacts with isocyanides to yield the respective iminoacyl derivatives Cp*Ti(eta2-MeCNR)(OOC)2py [R=tBu (4), 2,6-dimethylphenyl (xylyl) (5)]. The molecular structure of complex4 has been established by X-ray diffraction. Compound 2 has been employed as a new building block for the preparation of new early-late heterometallic compounds; it reacts with [M(mu-OH)(COD)]2 (M = Rh, Ir) to give the corresponding tetranuclear metallomacrocycle derivatives [Cp*Ti{(OOC)(2)py}(mu-O)M(COD)]2 [M = Rh (6); Ir (7)]. The molecular structure of 6 has been established by X-ray diffraction. 相似文献
100.
ER Badman GE Patterson JM Wells RE Santini RG Cooks 《Journal of mass spectrometry : JMS》1999,34(8):889-894
Dual-detector differential non-destructive Fourier transform detection in a quadrupole ion trap is shown to improve signal intensity and reduce noise compared with spectra recorded using a single detector. A larger area detector in each end-cap electrode is machined to fit its hyperbolic shape and so minimize field imperfections on the z-axis. Argon, acetophenone and bromobenzene spectra were recorded to allow a comparison between single- and dual-detector (differential) modes of detection and to demonstrate the improvement achieved with differential detection. Copyright 1999 John Wiley & Sons, Ltd. 相似文献