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51.
Dr. Andrea Previtali Dr. Wei He Dr. Alessandra Forni Dr. Daniele Malpicci Dr. Elena Lucenti Dr. Daniele Marinotto Prof. Lucia Carlucci Prof. Pierluigi Mercandelli Dr. Marco Aldo Ortenzi Prof. Giancarlo Terraneo Dr. Chiara Botta Prof. Ryan Tsz Kin Kwok Dr. Jacky Wing Yip Lam Prof. Ben Zhong Tang Prof. Elena Cariati 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(67):16690-16700
Organic materials with multiple emissions tunable by external stimuli represent a great challenge. TTPyr, crystallizing in different polymorphs, shows a very rich photophyisics comprising excitation-dependent fluorescence and phosphorescence at ambient conditions, and mechanochromic and thermochromic behavior. Transformation among the different species has been followed by thermal and X-ray diffraction analyses and the emissive features interpreted through structural results and DFT/TDDFT calculations. Particularly intriguing is the polymorph TTPyr(HT), serendipitously obtained at high temperature but stable also at room temperature, whose non-centrosymmetric structure guarantees an SHG efficiency 10 times higher than that of standard urea. Its crystal packing, where only the TT units are strongly rigidified by π-π stacking interactions while the Pyr moieties possess partial conformational freedom, is responsible for the observed dual fluorescence. The potentialities of TTPyr for bioimaging have been successfully established. 相似文献
52.
Marco Wenzel Jan J. Weigand 《Journal of inclusion phenomena and macrocyclic chemistry》2017,88(3-4):247-252
By linkage of 1,5-naphthalenedisulfonate (1,5-NDS) anion fluorophore, 3D cucurbit[7]uril (CB[7]) framework has been constructed. The maximum solid-state fluorescence wavelength of the CB[7] framework exhibits blue-shift from 406 to 340 nm in comparison with that of 1,5-NDS, which was ascribed to increased excited energy from 0.10 to 0.13 eV according to theoretical calculations. 相似文献
53.
We show that symmetric block designs \({\mathcal {D}}=({\mathcal {P}},{\mathcal {B}})\) can be embedded in a suitable commutative group \({\mathfrak {G}}_{\mathcal {D}}\) in such a way that the sum of the elements in each block is zero, whereas the only Steiner triple systems with this property are the point-line designs of \({\mathrm {PG}}(d,2)\) and \({\mathrm {AG}}(d,3)\). In both cases, the blocks can be characterized as the only k-subsets of \(\mathcal {P}\) whose elements sum to zero. It follows that the group of automorphisms of any such design \(\mathcal {D}\) is the group of automorphisms of \({\mathfrak {G}}_\mathcal {D}\) that leave \(\mathcal {P}\) invariant. In some special cases, the group \({\mathfrak {G}}_\mathcal {D}\) can be determined uniquely by the parameters of \(\mathcal {D}\). For instance, if \(\mathcal {D}\) is a 2-\((v,k,\lambda )\) symmetric design of prime order p not dividing k, then \({\mathfrak {G}}_\mathcal {D}\) is (essentially) isomorphic to \(({\mathbb {Z}}/p{\mathbb {Z}})^{\frac{v-1}{2}}\), and the embedding of the design in the group can be described explicitly. Moreover, in this case, the blocks of \(\mathcal {B}\) can be characterized also as the v intersections of \(\mathcal {P}\) with v suitable hyperplanes of \(({\mathbb {Z}}/p{\mathbb {Z}})^{\frac{v-1}{2}}\). 相似文献
54.
Wei-Jing Gao Chiu Marco Lam Bao-Guo Sun R. Daniel Little Cheng-Chu Zeng 《Tetrahedron》2017,73(17):2447-2454
The electrochemically oxidative cleavage of lignin β-O-4 model compounds mediated by iodide ion has been studied. The results indicate that electrolytic conditions play a predominant role in determining the distribution of cleavage products. The preparative-scale electrolysis proceeds in a simple undivided cell, employing a catalytic amount of NaI as the redox mediator and supporting electrolyte in methanol. Under these conditions, the CβO bond is selectively cleaved with 2,2-dimethoxy-2-arylacetaldehyde being the main product. In some cases, the reaction gives a good yield of cleavaged products. The results further demonstrate that the indirect electrolysis mediated by halide is a versatile approach for chemical transformation. 相似文献
55.
Carla F. C. Ruschel Marcelo C. A. Marcelo Francisco P. dos Santos Marco F. Ferrão 《Analytical letters》2017,50(11):1767-1777
Automotive fuel adulteration is an old and significant problem. One common type of fuel adulteration is the addition of diesel to gasoline. Unsupervised models were developed through hierarchical cluster and principal component analysis models. Supervised models through partial least square discriminant analysis using 1H nuclear magnetic resonance spectra as the input were used to classify samples as adulterated or unadulterated. Quantitative models were developed using partial least squares to determine the gasoline and diesel concentrations in the samples. This set contained samples composed of pure gasoline and anhydrous ethanol reproducing commercial gasoline and other samples treated with diesel. Hierarchical cluster and principal component analysis did not distinguish between adulterated and unadulterated samples except for the most adulterated materials. However, partial least square discriminant analysis classified 100% of the samples correctly. The partial least square algorithm provided excellent regression models for the gasoline and diesel content. The determination coefficient was 0.9920 for both models, whereas the root mean square error of cross-validation and root mean square error of prediction for the diesel model were 2.32 and 1.42%, respectively, and 2.40 and 1.38% for the gasoline model. 相似文献
56.
Labiadh Lazhar Barbucci Antonio Carpanese Maria Paola Gadri Abdellatif Ammar Salah Panizza Marco 《Journal of Solid State Electrochemistry》2017,21(8):2167-2175
Journal of Solid State Electrochemistry - In this paper, the electrocatalytic properties of PbO2 and TiRuSnO2 anodes for direct and indirect electrochemical oxidation of a synthetic solution... 相似文献
57.
Natashia Boland Santanu S. Dey Thomas Kalinowski Marco Molinaro Fabian Rigterink 《Mathematical Programming》2017,162(1-2):523-535
We investigate how well the graph of a bilinear function \(b{:}\;[0,1]^n\rightarrow \mathbb {R}\) can be approximated by its McCormick relaxation. In particular, we are interested in the smallest number c such that the difference between the concave upper bounding and convex lower bounding functions obtained from the McCormick relaxation approach is at most c times the difference between the concave and convex envelopes. Answering a question of Luedtke, Namazifar and Linderoth, we show that this factor c cannot be bounded by a constant independent of n. More precisely, we show that for a random bilinear function b we have asymptotically almost surely \(c\geqslant \sqrt{n}/4\). On the other hand, we prove that \(c\leqslant 600\sqrt{n}\), which improves the linear upper bound proved by Luedtke, Namazifar and Linderoth. In addition, we present an alternative proof for a result of Misener, Smadbeck and Floudas characterizing functions b for which the McCormick relaxation is equal to the convex hull. 相似文献
58.
At some point, after publication, we realized that Proposition 4.1(2) and Theorem 4.4 in [2] hold under the assumption (not explicitly declared) that B = f(A)+J. Furthermore, we provide here the exact value for the embedding dimension of A?fJ, also when B≠f(A)+J, under the hypothesis that J is finitely generated as an ideal of the ring f(A)+J. 相似文献
59.
Marco Bee Giuseppe Espa Diego Giuliani Flavio Santi 《Journal of computational and graphical statistics》2017,26(3):695-708
In this article, we use the cross-entropy method for noisy optimization for fitting generalized linear multilevel models through maximum likelihood. We propose specifications of the instrumental distributions for positive and bounded parameters that improve the computational performance. We also introduce a new stopping criterion, which has the advantage of being problem-independent. In a second step we find, by means of extensive Monte Carlo experiments, the most suitable values of the input parameters of the algorithm. Finally, we compare the method to the benchmark estimation technique based on numerical integration. The cross-entropy approach turns out to be preferable from both the statistical and the computational point of view. In the last part of the article, the method is used to model the probability of firm exits in the healthcare industry in Italy. Supplemental materials are available online. 相似文献
60.
Ky Ho Kanishka Perera Inbo Sim Marco Squassina 《Journal of Fixed Point Theory and Applications》2017,19(1):157-173
We study a class of fractional p-Laplacian problems with weights which are possibly singular on the boundary of the domain. We provide existence and multiplicity results as well as characterizations of critical groups and related applications. 相似文献