全文获取类型
收费全文 | 3978篇 |
免费 | 79篇 |
国内免费 | 16篇 |
专业分类
化学 | 2463篇 |
晶体学 | 16篇 |
力学 | 274篇 |
数学 | 823篇 |
物理学 | 497篇 |
出版年
2023年 | 19篇 |
2022年 | 78篇 |
2021年 | 101篇 |
2020年 | 83篇 |
2019年 | 72篇 |
2018年 | 56篇 |
2017年 | 46篇 |
2016年 | 121篇 |
2015年 | 112篇 |
2014年 | 109篇 |
2013年 | 201篇 |
2012年 | 220篇 |
2011年 | 237篇 |
2010年 | 168篇 |
2009年 | 146篇 |
2008年 | 200篇 |
2007年 | 208篇 |
2006年 | 200篇 |
2005年 | 179篇 |
2004年 | 160篇 |
2003年 | 110篇 |
2002年 | 140篇 |
2001年 | 39篇 |
2000年 | 44篇 |
1999年 | 40篇 |
1998年 | 32篇 |
1997年 | 41篇 |
1996年 | 46篇 |
1995年 | 35篇 |
1994年 | 32篇 |
1993年 | 42篇 |
1992年 | 46篇 |
1991年 | 31篇 |
1990年 | 14篇 |
1989年 | 21篇 |
1988年 | 21篇 |
1987年 | 33篇 |
1986年 | 15篇 |
1985年 | 33篇 |
1984年 | 36篇 |
1983年 | 38篇 |
1982年 | 33篇 |
1981年 | 47篇 |
1980年 | 47篇 |
1979年 | 41篇 |
1978年 | 26篇 |
1977年 | 29篇 |
1976年 | 23篇 |
1975年 | 19篇 |
1967年 | 13篇 |
排序方式: 共有4073条查询结果,搜索用时 0 毫秒
131.
Scaramozzino Domenico Lacidogna Giuseppe Piana Gianfranco Carpinteri Alberto 《Meccanica》2019,54(13):1927-1940
Meccanica - Protein mechanical vibrations play a pivotal role in biological activity. In particular, low-frequency (terahertz) modes are related to protein conformational changes, which represent... 相似文献
132.
Iurato Giuseppe Khrennikov Andrei Yu. 《P-Adic Numbers, Ultrametric Analysis, and Applications》2020,12(1):68-71
p-Adic Numbers, Ultrametric Analysis and Applications - This comment is aimed to point out that the recent work due to H. Kim, J-Y. Moon, G. A. Mashour and U. Lee ([22]), in which the clinical and... 相似文献
133.
Dr. Qaisar Nadeem Dr. Giuseppe Meola Dr. Henrik Braband Robin Bolliger Dr. Olivier Blacque Daniel Hernández-Valdés Prof. Dr. Roger Alberto 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(3):1213-1216
The labeling of (bio)molecules with metallic radionuclides such as 99mTc demands conjugated, multidentate chelators. However, this is not always necessary since phenyl rings can directly serve as integrated, organometallic ligands. Bis-arene sandwich complexes are generally prepared by the Fischer–Hafner reaction. In extension of this, we show that [99mTc(η6-C6R6)2]+-type complexes are directly accessible from water and [99mTcO4]−, even using arenes incompatible with Fischer–Hafner conditions. To unambiguously confirm the nature of these unprecedented 99mTc complexes, their rhenium homologous have been prepared by substituting naphthalene ligands in [Re(η6-C10H8)2]+ with the corresponding phenyl groups. The ease with which highly stable [99mTc(η6-C6R6)2]+ complexes are formed under standard labeling conditions enables a multitude of new potential imaging agents based on commercial pharmaceuticals or lead structures. 相似文献
134.
135.
Raffaele Ferrari Giuseppe Storti Massimo Morbidelli 《Journal of polymer science. Part A, Polymer chemistry》2020,58(12):1642-1654
Emulsion polymerization of the three-monomer system butyl acrylate–styrene–methacrylic acid was performed in batch using a commercial maltodextrin derived from starch degradation as stabilizer. Stable latexes with narrow particle size distributions were obtained in all examined cases. A method was developed to analyze and quantify the partitioning of the maltodextrin between the continuous phase (supernatant) and the particle phase. Significant differences between the polysaccharides adsorbed onto particles with or without emulsion polymerization reaction were observed. The possible reactions of maltodextrin in presence of a radical initiator were studied in aqueous phase, thus confirming maltodextrin degradation. The formation of copolymers involving the original monomers and the stabilizer according to two different reactive pathways was also confirmed. In terms of adsorbed maltodextrin, two different contributions were observed: maltodextrin physically adsorbed and maltodextrin chemically grafted and/or physically incorporated into the polymer. 相似文献
136.
Heorhii V. Humeniuk Giuseppe Licari Eric Vauthey Naomi Sakai 《Supramolecular chemistry》2020,32(2):106-111
ABSTRACTDesign, synthesis and evaluation of push-pull N,N′-diphenyl-dihydrodibenzo[a,c]phenazines are reported. Consistent with theoretical predictions, donors and acceptors attached to the bent mechanophore are shown to shift absorption maxima to either red or blue, depending on their positioning in the chromophore. Redshifted excitation of push-pull fluorophores is reflected in redshifted emission of both bent and planar excited states. The intensity ratios of the dual emission in more and less polar solvents imply that excited-state (ES) planarization decelerates with increasing fluorophore macrodipole, presumably due to attraction between the wings of closed papillons. ES planarization of highly polarisable papillons is not observed in lipid bilayer membranes. All push-pull papillon amphiphiles excel with aggregation-induced emission (AIE) from bent ES as micelles in water and mechanosensitivity in viscous solvents. They are not solvatochromic and only weakly fluorescent (QY < 4%). 相似文献
137.
Coclite Giuseppe Maria Dipierro Serena Maddalena Francesco Valdinoci Enrico 《Journal of Nonlinear Science》2020,30(4):1285-1305
The formation of singularities in finite time in nonlocal Burgers’ equations, with time-fractional derivative, is studied in detail. The occurrence of finite-time singularity is proved, revealing the underlying mechanism, and precise estimates on the blowup time are provided. The employment of the present equation to model a problem arising in job market is also analyzed.
相似文献138.
Dr. Atash V. Gurbanov Dr. Maxim L. Kuznetsov Dr. Kamran T. Mahmudov Prof. Armando J. L. Pombeiro Prof. Giuseppe Resnati 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(65):14833-14837
Intramolecular chalcogen bonding in arylhydrazones of sulfamethizole is strengthened by conjugation in the π-system of a noncovalent five-membered ring. The S⋅⋅⋅O distance in the sulfamethizole moiety of these compounds ranges from 2.698(3) to 2.806(15) Å, which indicates its strong dependence on the attached arylhydrazone fragments. Information on the nature of the intramolecular chalcogen bond was afforded by DFT calculations. 相似文献
139.
We analyze isolated resonance curves (IRCs) in single-degree-of-freedom systems possessing nonlinear damping. Through the combination of singularity theory and the averaging method, the onset and merging of IRCs, which coincide to isola and simple bifurcation singularities, respectively, can be analytically predicted. Numerical simulations confirm the accuracy of the analytical developments. Another important finding of this paper is that we unveil a geometrical connection between the topology of the damping force and IRCs. Specifically, we demonstrate that extremas and zeros of the damping force correspond to the appearance and merging of IRCs. Considering a damping force possessing several minima and maxima confirms the general validity of the analytical result. It also evidences a very complex scenario for which different IRCs are created, co-exist and then merge together to form a super IRC which eventually merges with the main resonance peak. 相似文献
140.
Gianpiero Cattaneo Giuseppe Nisticó 《International Journal of Theoretical Physics》1991,30(10):1293-1336
Some of the most frequent misconceptions about axiomatic quantum physics are discussed with the aim of clarifying their true significance, taking Piron's approach as conceptual framework. In particular, we deal with the following topics: the wrong identification of Piron's questions and Mackey's questions, and some curious alleged empirical consequences; the role of propositions as suitable equivalence classes of questions, their partial order structure, and the paradoxical consequences of the erroneous assignment to questions of some lattice properties involving propositions; the logical and the empirical purport of some negative theorems; the standard Hilbert space model of the theory and the consequent metaphysical disasters related to some identifications, which are peculiar of this model. A controversy between Foulis-Piron-Randall and Hadjisavvas-Thieffine-Mugur-Schächter is analyzed on the basis of the proposed Hilbert space model (in which Piron's questions are realized by Hilbertian effects, i.e., linear bounded operatorsF such that which clarify the different point of views. As an example, we treat the unsharp localization operators inL
2(). 相似文献