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641.
Pierluigi Colli Augusto Visintin K. P. Hadeler 《Mathematical Methods in the Applied Sciences》1989,11(1):79-93
During fertilization of certain echinoderms, a long actin-filled tube is extended by the sperm towards the interior of the egg. This yields a parabolic free boundary problem, which differs from the classical one-phase Stefan problem by the presence of a convective term in the partial differential equation, and because the equilibrium interface condition θ(s(t),t) = 0 is here replaced by a kinetic law s′(t) = vθ(s(t),t). This problem is set in variational form and the existence of a solution is proved by means of a Faedo–Galerkin approximation procedure. 相似文献
642.
Augusto Colombo Jordi Frigola Juan Pars Blas Andaluz 《Journal of heterocyclic chemistry》1990,27(3):615-622
The synthesis, structure elucidation and chemotherapeutic activity of novel heterocyclic analogues of the cardiotropic agent Diclofurime are reported. 相似文献
643.
The electromagnetic corrections to τ → Mντ decay, where M is pseudoscalar meson, are treated with all generality. An expression for the decay rate is found, which is accurate up to a few hundredths of a percent, provided hard bremsstrahlung photons are discriminated. 相似文献
644.
Chrysomya blowflies are originally from Africa and Australasia and were introduced in the American Continent, probably as a sheep parasite, in the 1970s. These flies are extremely important for medical-sanitary purposes and are useful to forensic entomology being used as an indicative of decomposition time in human corpses. The morphology of the larval and pupal stages of some species has been already studied by different authors demonstrating that it is possible to identify them in premature stages. In this study, Chrysomya megacephala egg ultramorphology was analyzed to describe its structure, generating data for further comparison between different species and genera. The blowflies were collected in Rio Claro city, SP, Brazil. Flies were attracted by fish carcasses and maintained in net cages; small portions of minced meat were placed in plastic pots for egg laying. Eggs were collected, fixed in alcoholic Bouin, prepared according to SEM routine and observed under Philips scanning electron microscope. C. megacephala eggs are oval with one flat face and another convex, measuring approximately 0.52 (+/-0.03) mm of length and 0.12 (+/-0.02) mm of width. The micropyle is circular in shape, with two perforations enclosed by countless small projections and is located in one of the extremities in the interface between the flat and convex faces. On the convex surface hexagonal imprints were observed, this surface is impermeable to water and gases. The flat surface has numerous round projections with different sizes, creating a permeable surface with a thinner chorion from which the larvae hatches. The larvae presents itself all wrinkled and with numerous cuticular projections with a thorn shape facing the posterior region. The cuticle projections with a thorn shape from C. megacephala larvae are probably a vestige of the thorns found in larvae of parasite Diptera. 相似文献
645.
Giuseppe Cilento Nelson Durán Klaus Zinner Carmen C. C. Vidigal Olga M. M. Faria Oliveira Marcela Haun Adelaide Fauoni Ohara Augusto Roberto Casadei de Baptista Etelvino J. H. Bechara 《Photochemistry and photobiology》1978,28(4-5):445-450
Abstract— Several hemeprotein-catalyzed reactions generate products of the type expected from the cleavage of a high energy intermediate. For some systems, the formation, in high yield, of a carbonyl compound in its excited triplet state has been firmly established on the basis of (i) equivalence of the chemiluminescence and phosphorescence spectra of the expected products; (ii) energy transfer to sensitizers containing heavy atoms and (iii) occurrence of photoproducts. The excited species appears to be generated within the enzyme and shielded from quenching by oxygen. It may be quenched, however, via long-range triplet-singlet energy transfer.
This work strongly supports our hypothesis that excited electronic states are also formed in biological systems which are not necessarily bioluminescent. One of the functions which peroxidases may thus fulfill might be the utilization of the potential of photochemistry in the absence of light. 相似文献
This work strongly supports our hypothesis that excited electronic states are also formed in biological systems which are not necessarily bioluminescent. One of the functions which peroxidases may thus fulfill might be the utilization of the potential of photochemistry in the absence of light. 相似文献
646.
Armando Marzotto Dore Augusto Clemente Antonella Ciccarese Giovanni Valle 《Journal of chemical crystallography》1993,23(2):119-131
With the aim to obtain further insight into the nature of the Ni(II)-nitrogen bond in complexes with nucleobases, we have synthesized two novel Ni(II) ternary complexes constituted by Ni(II), tris(2-aminoethyl)amine (tren) and neutral adenine (AdH) or imidazole (ImH). The reaction of NiCl2·6H2O with tren and imidazole yields the ternary [Ni(tren)(ImH)(H2O)]Cl2·H2O complex and the same reaction with adenine instead of imidazole gives the ternary [Ni(tren)(AdH)Cl]Cl complex. The complexes have been studied by spectrophotometric and spectroscopic measurements and by X-ray diffraction. The ternary complex of adenine is monoclinic, space groupC2/c, and exhibits a pseudo-octahedral geometry, being Ni(II) coordinated to the four nitrogen atoms of the tetradentate tren ligand, to a Cl– ion and to the pyrimidine N3 site of a neutral adenine. Such an exclusive Ni-N3 bonding [2.081(4)Å] is now reported for the first time. The ternary complex of imidazole is monoclinic, space groupP21/n. Its pseudo-octahedral geometry is similar to that found in the above adenine complex although a water molecule instead of a Cl– ion is now present in the coordination sphere. In fact, Ni(II) is coordinated to tetradentate tren, to the imidazole N1 nitrogen and to a water molecule. Electronic and1H NMR spectra in solution indicate that the octahedral structures found in the solid state are substantially maintained in solution. Furthermore, the present investigation suggests that the adenine Ni-N3 and imidazole Ni-N1 bonds have the same chemical nature, involving mainly - and only partially-bonding. The Ni-N3 bonding is discussed in connection with biological implications and possible applications. 相似文献
647.
We introduce a family of Hamiltonian systems for measurement-based quantum computation with continuous variables. The Hamiltonians (i) are quadratic, and therefore two body, (ii) are of short range, (iii) are frustration-free, and (iv) possess a constant energy gap proportional to the squared inverse of the squeezing. Their ground states are the celebrated Gaussian graph states, which are universal resources for quantum computation in the limit of infinite squeezing. These Hamiltonians constitute the basic ingredient for the adiabatic preparation of graph states and thus open new venues for the physical realization of continuous-variable quantum computing beyond the standard optical approaches. We characterize the correlations in these systems at thermal equilibrium. In particular, we prove that the correlations across any multipartition are contained exactly in its boundary, automatically yielding a correlation area law. 相似文献
648.
Paulo Sérgio Lins Perazzo Marcos André Sarvat Francisco de Souza Amorim Filho Paulo Augusto de Lima Pontes 《Journal of voice》2011,25(5):626-631
Objectives
To assess the integration of an autologous composite fascia and fat graft implanted into the lamina propria of a porcine vocal fold using two different approaches.Study Design
An experimental prospective study on the porcine larynx was conducted at a tertiary research institution.Methods
An external cervical approach was used to expose the thyroid cartilage of 24 healthy minipigs under general anesthesia. The composite fascia/fat graft was implanted through two distinct approaches, transmuscular and submuscular. Animals were sacrificed at 7, 30, 90, and 180 days for macroscopic and histological study of the larynx. Graft integration and local inflammatory response were studied.Results
The survival rate of the experimental model was 100% and all animals had local inflammatory response to the surgical procedure. Only 41.7% of the grafts placed inside the thyroarytenoid (TA) muscle fibers were identified postmortem, whereas 83.3% of the submuscular grafts remained intact.Conclusions
Graft incorporation was better and there was less inflammation when the architecture of the TA muscle fibers was preserved. Graft extrusion was observed in the most of the cases where it was placed inside the muscle. 相似文献649.
Francesco Petitta Augusto C. Ponce Alessio Porretta 《Journal of Evolution Equations》2011,11(4):861-905
Given a parabolic cylinder Q = (0, T) × Ω, where
W ì \mathbb RN{\Omega\subset \mathbb {R}^N} is a bounded domain, we prove new properties of solutions of
ut-Dp u = m \textin Qu_t-\Delta_p u = \mu \quad \text{in }Q 相似文献
650.
Augusto Rivera Diego Quiroga Jaime Ríos‐Motta Karla Fejfarov Michal Duek 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(12):o505-o508
The title compound, C7H12N4O2, was obtained by nitrosation of the aminal cage (2R,7R,11S,16S)‐1,8,10,17‐tetraazapentacyclo[8.8.1.18,17.02,7.011,16]icosane. The crystal structure is a racemic mixture of RR and SS enantiomers. The asymmetric unit contains two crystallographically independent half‐molecules, one having two partially occupied conformers with refined occupancy factors of 0.747 (3) and 0.253 (3). The molecules sit across twofold axes. The unique molecules each form chains parallel to [001], with molecules connected by intermolecular C—H...O hydrogen bonds. The bonding between adjacent chains is weak. The analysis of eight different crystals confirmed the presence of disordered and nondisordered molecules in the same structure as a regular feature. 相似文献
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