全文获取类型
收费全文 | 1089篇 |
免费 | 50篇 |
国内免费 | 6篇 |
专业分类
化学 | 685篇 |
晶体学 | 2篇 |
力学 | 41篇 |
数学 | 195篇 |
物理学 | 222篇 |
出版年
2023年 | 11篇 |
2022年 | 11篇 |
2021年 | 39篇 |
2020年 | 26篇 |
2019年 | 20篇 |
2018年 | 17篇 |
2017年 | 25篇 |
2016年 | 49篇 |
2015年 | 40篇 |
2014年 | 48篇 |
2013年 | 57篇 |
2012年 | 60篇 |
2011年 | 75篇 |
2010年 | 31篇 |
2009年 | 38篇 |
2008年 | 63篇 |
2007年 | 69篇 |
2006年 | 75篇 |
2005年 | 58篇 |
2004年 | 45篇 |
2003年 | 36篇 |
2002年 | 38篇 |
2001年 | 18篇 |
2000年 | 19篇 |
1999年 | 14篇 |
1998年 | 12篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 7篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 13篇 |
1983年 | 4篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1972年 | 2篇 |
排序方式: 共有1145条查询结果,搜索用时 31 毫秒
71.
Riccardo Ricceri Alessandro Abbotto Antonio Facchetti Daniela Grando Gabriella Gabrielli Giorgio A. Pagani 《Colloids and surfaces. A, Physicochemical and engineering aspects》1999,150(1-3):289-296
We report on Langmuir-Blodgett (LB) films characterization of 4-[5-dicyanomethanido)thien-2-y1]-N-(n-hexadecyl)pyridinium (C16H33-PDCNT), and 1-(N-(n-hexadecy]-4-pyridinio)-2-[5-(dicyanomethanido)thien-2-yl]ethene (C16H33-PDCNTE); LB films of the pure compounds and of the mixtures of the two compounds were prepared at 291 K: UV-vis investigation revealed the presence of photobleachable absorption bands, the ones at about 530 nm and 640 nm were due to charge transfer transitions of the monomer of C16H33-PDCNT and C16H33-PDCNTE, respectively; the sharp, photobleachable ones shifted to shorter wavelengths were due to H-aggregates of the two compounds. By changing the molar ratios of the two compounds in the mixtures and in other cases by annealing the LB films, the absorption maxima of the sharp, photobleachable bands due to H-aggregates could be tuned in the range 415–467 nm. These LB films are thus very promising in view of optical data storage applications. 相似文献
72.
73.
We generalize some identities and q-identities previously known for the symmetric group to Coxeter groups of type B and D. The extended results include theorems of Foata and Schützenberger, Gessel, and Roselle on various distributions of statistics, like inversion number, major index, and descent number. In order to show our results we provide explicit characterizations of the systems of minimal coset representatives of Coxeter groups of type B and D. 相似文献
74.
Riccardo Narizzano Fulvia Risso Gloria VenturelliCarla Devia Eugenio CarliniStefano Maggiolo 《Journal of chromatography. A》2009,1216(39):6762-6766
Two methods for the analysis of dimethyl fumarate (DMF) on silica gel, leather and other similar products are presented. The methods are based on solvent extraction or head space solid phase microextraction coupled with gas-chromatography–mass spectrometry. The methods are developed in order to satisfy the mandatory requirements of the European Community and with the aim to have easy and reliable methods to provide rapid responses. 相似文献
75.
76.
We introduce and analyze the characteristic foliation induced by a contact structure on a branched surface, in particular
a branched standard spine of a 3-manifold. We extend to (fairly general) singular foliations of branched surfaces the local
existence and uniqueness results which hold for genuine surfaces. Moreover we show that global uniqueness holds when restricting
to tight structures. We establish branched versions of the elimination lemma. We prove a smooth version of the Gillman-Rolfsen
PL-embedding theorem, deducing that branched spines can be used to construct contact structures in a given homotopy class
of plane fields.
Entrata in Redazione il 6 novembre 1998. 相似文献
77.
A heterodyne interferometric polarimeter for detection of the Jones components and Stokes parameters is demonstrated. The measurement of both sets of quantities for various polarization states is achieved with excellent precision. The details of the corresponding Lissajous picture (ellipse) can be visualized in real time. Finally, the polarization data collected at the output of a highly birefringent fiber have been used for submillimetric beat-Length measurements. 相似文献
78.
Riccardo Biagioli 《Discrete Mathematics》2005,296(1):1-13
Some posets of binary leaf-labeled trees are shown to be supersolvable lattices and explicit EL-labelings are given. Their characteristic polynomials are computed, recovering their known factorization in a different way. 相似文献
79.
Ivan Lazic Riccardo Pernice Tatjana Loncar-Turukalo Gorana Mijatovic Luca Faes 《Entropy (Basel, Switzerland)》2021,23(6)
Apnea and other breathing-related disorders have been linked to the development of hypertension or impairments of the cardiovascular, cognitive or metabolic systems. The combined assessment of multiple physiological signals acquired during sleep is of fundamental importance for providing additional insights about breathing disorder events and the associated impairments. In this work, we apply information-theoretic measures to describe the joint dynamics of cardiorespiratory physiological processes in a large group of patients reporting repeated episodes of hypopneas, apneas (central, obstructive, mixed) and respiratory effort related arousals (RERAs). We analyze the heart period as the target process and the airflow amplitude as the driver, computing the predictive information, the information storage, the information transfer, the internal information and the cross information, using a fuzzy kernel entropy estimator. The analyses were performed comparing the information measures among segments during, immediately before and after the respiratory event and with control segments. Results highlight a general tendency to decrease of predictive information and information storage of heart period, as well as of cross information and information transfer from respiration to heart period, during the breathing disordered events. The information-theoretic measures also vary according to the breathing disorder, and significant changes of information transfer can be detected during RERAs, suggesting that the latter could represent a risk factor for developing cardiovascular diseases. These findings reflect the impact of different sleep breathing disorders on respiratory sinus arrhythmia, suggesting overall higher complexity of the cardiac dynamics and weaker cardiorespiratory interactions which may have physiological and clinical relevance. 相似文献
80.
Riccardo Fazio 《Wave Motion》1992,16(4):299-305
In this paper we present some results obtained by studying the mathematical model describing a moving boundary hyperbolic problem related to a time dependent stress impact in a bar of Maxwell-like material. Due to the impact a shock front propagates with a finite speed. Here our interest is to underline the influence of the dissipative term on the propagation of the shock front.
In the framework of the similarity analysis we are able to reduce the moving boundary hyperbolic problem to a free boundary value problem for an ordinary differential system. It is then possible, by applying two numerical transformation methods, to solve the free boundary value problem numerically. The influence of the dissipative term is evident: the free boundary (that defines the shock front propagation) is an increasing function of the dissipative coefficient. 相似文献