全文获取类型
收费全文 | 1900篇 |
免费 | 53篇 |
国内免费 | 4篇 |
专业分类
化学 | 1161篇 |
晶体学 | 4篇 |
力学 | 111篇 |
数学 | 341篇 |
物理学 | 340篇 |
出版年
2024年 | 6篇 |
2023年 | 20篇 |
2022年 | 46篇 |
2021年 | 64篇 |
2020年 | 39篇 |
2019年 | 40篇 |
2018年 | 34篇 |
2017年 | 32篇 |
2016年 | 67篇 |
2015年 | 61篇 |
2014年 | 54篇 |
2013年 | 92篇 |
2012年 | 103篇 |
2011年 | 147篇 |
2010年 | 61篇 |
2009年 | 61篇 |
2008年 | 117篇 |
2007年 | 110篇 |
2006年 | 107篇 |
2005年 | 81篇 |
2004年 | 73篇 |
2003年 | 59篇 |
2002年 | 72篇 |
2001年 | 22篇 |
2000年 | 15篇 |
1999年 | 22篇 |
1998年 | 15篇 |
1997年 | 23篇 |
1996年 | 34篇 |
1995年 | 20篇 |
1994年 | 14篇 |
1993年 | 21篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 12篇 |
1989年 | 14篇 |
1988年 | 9篇 |
1987年 | 17篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1979年 | 10篇 |
1978年 | 14篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1975年 | 5篇 |
排序方式: 共有1957条查询结果,搜索用时 31 毫秒
251.
252.
253.
Michele Di Foggia Paola Taddei Armida Torreggiani Monica Dettin Anna Tinti 《Journal of Raman spectroscopy : JRS》2011,42(3):276-285
Five alternating polar/hydrophobic oligopeptides derived from EAK 16 (AEAEAKAKAEAEAKAK) were examined in comparison with EAK 16 (peptide 1) both after solubilisation/lyophilisation and deposition on oxidised titanium surfaces. The peptides were synthesised for their possible use as biomimetic materials due to their self‐assembling properties and the presence, in one of them, of the arginine‐glycine‐aspartic (RGD) sequence, an active modulator of cell adhesion. Infrared (IR) and Raman spectroscopies were used to investigate the influence of the amino acid substitution on the self‐assembling properties of the peptides under both experimental conditions. In the lyophilised peptides, β‐sheet was the prevailing conformation (65–69%) as in EAK 16, irrespective of acid substitution (E→D, peptide 2), basic substitution (K→O, peptide 3), hydrophobic spacer substitution (A→Abu, peptide 4 and A→Y, peptide 5) and RGD insertion (peptide 6). After deposition on oxidised titanium, the main conformation remained β‐sheet. The side‐chain shortening of the acidic amino acid residue (peptide 2) or the insertion of a rigid and bulky residue such as Y (peptide 5) decreased the self‐assembling ability more than the side‐chain shortening of the basic amino acid residue (peptide 3) or the insertion of the RGD head (peptide 6). The interaction with the oxidised titanium surface was mainly due to carboxylate groups with a bidentate bridging coordination and C O peptidic groups. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
254.
Michele Colturato 《Mathematical Methods in the Applied Sciences》2020,43(10):6598-6626
We consider the sliding mode control (SMC) problem for a diffuse interface tumor growth model coupling a Cahn–Hilliard equation with a reaction–diffusion equation perturbed by a maximal monotone nonlinearity. We prove existence and regularity of strong solutions and, under further assumptions, a uniqueness result. Then, we show that the chosen SMC law forces the system to reach within finite time a sliding manifold that we chose in order that the tumor phase remains constant in time. 相似文献
255.
Michele Iannone Anna Pia Dima Francesca Sciarra Francesco Botrè Andrea M. Isidori 《Biomedical chromatography : BMC》2022,36(5):e5344
We present a liquid chromatography tandem mass spectrometry method for the simultaneous analysis of 16 endogenous steroids (androgens, estrogens, glucocorticoids and progestogens) in human serum. Samples (250 μl of matrix) were extracted with t-butylmethyl ether prior to LC–MS/MS analysis. The chromatographic separation was achieved on a reversed-phase column using a methanol–water gradient. The HPLC was coupled to a triple quadrupole mass spectrometer equipped with an electrospray ionization source with acquisition in multiple reaction monitoring mode. The method was validated using surrogate matrices and human serum samples. The specificity of the method was confirmed for all of the considered steroids; linearity was also assessed (R2 > 0.99, lack-of-fit test) in the ranges of concentrations investigated. The lower limits of quantification were in the range 10–400 pg/ml depending on the target steroid. Accuracy was in the range 85–115% for all target steroids except for the lower limit of quantitation levels where it was 80–120%. The extraction recovery was always >65%. No significant matrix effects were observed. To test the reliability of the method, the analysis of serum samples collected from 10 healthy subjects (5 M/5F) was performed. The present method can be used to identify the trajectories of deviation from the concentration normality ranges applied to disorders of the gonadal and adrenal axes. 相似文献
256.
257.
Letters in Mathematical Physics - In this note, we study refined BPS invariants associated with certain quantum line defects in quantum field theories of class $${{\mathcal {S}}}$$. Such defects... 相似文献
258.
Michele Vascellari Danny Messig Arne Scholtissek Christian Hasse Meng Xia Benoît Fiorina Nasser Darabiha 《Proceedings of the Combustion Institute》2019,37(3):2857-2866
A multi-stream Flamelet Progress Variable (FPV) model, specifically developed for coal combustion, is proposed. The model accounts for the different fuel streams associated with the volatile and char burnout products. The applicability of the new FPV model is investigated in a laminar stagnation pulverized coal flame. The flame considered is a premixed mixture of CH4, O2 and N2, carrying pulverized coal particles, stabilized in an impinging wall. Spontaneous emissions of OH*, CH* and C are measured to identify the flame. The 1D numerical simulations of the experimental conditions are able to reproduce the main features of the flame. The applicability of the multi-stream FPV model to coal combustion is further evaluated with the a posteriori analysis of the FPV results, comparing the results with a reference model, where the species are fully transported and the chemistry directly evaluated. Then, with the budget analysis, the influence of the control variables used to build the look-up table is assessed by examining the conditional contributions to the overall transport terms of scalar quantities (e.g. species, temperature). The results of both analyses show that the proposed multi-stream FPV model can accurately predict the main features of coal combustion, with only minor issues related to the manifold used to build the look-up table. 相似文献
259.
Hexametaphosphate‐Capped Silica Mesoporous Nanoparticles Containing CuII Complexes for the Selective and Sensitive Optical Detection of Hydrogen Sulfide in Water 下载免费PDF全文
Sameh El Sayed Dr. Michele Milani Prof. Maurizio Licchelli Prof. Ramón Martínez‐Máñez Dr. Félix Sancenón 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(19):7002-7006
CuII‐macrocycle functionalized hexametaphosphate‐capped silica mesoporous nanoparticles have been prepared and used for the selective and sensitive detection of hydrogen sulfide in aqueous environments. The possibility of using different metal complexes combined with different capping anions and choice of different dyes or other sensing molecules as indicators makes this new protocol highly appealing for the preparation of new sensing systems for sulfide detection in different environments. 相似文献
260.