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排序方式: 共有134条查询结果,搜索用时 15 毫秒
1.
Francesca Porta Sergio Cenini Sergio Giordano Maddalena Pizzotti 《Journal of organometallic chemistry》1978,150(2):261-271
The complexes M(CO)2(PPh3)3 (I, M = Fe; II, M = Ru) readily react with H2 at room temperature and atmospheric pressure to give cis-M(H)2(CO)2(PPh3)2 (III, M = Fe;IV,M = Ru). I reacts with O2 to give an unstable compound in solution, in a type of reaction known to occur with II which leads to cis-Ru(O2)(CO)2(PPh3)2(V). Even compound IV reacts with O2 to give V with displacement of H2; this reaction has been shown to be reversible and this is the first case where the displacement of H2 by O2 and that of O2 by H2 at a metal center has been observed. III and IV are reduced to M(CO)3(PPh3)2 by CO with displacement of H2; Ru(CO)3- (PPh3)2 is also formed by treatment of IV with CO2, but under higher pressure. Compounds II and IV react with CH2CHCN to give Ru(CH2CHCN)(CO)2- (PPh3)2(VI) which reacts with H2 to reform the hydride IV.cis-Ru(H)2(CO)2(PPh3)2(IV) has been studied as catalyst in the hydrogenation and isomerization of a series of monoenes and dienes. The catalysts are poisoned by the presence of free triphenylphosphine. On the other hand the ready exchange of H2 and O2 on the “Ru(CO)2(PPh3)2” moiety makes IV a catalyst not irreversibly poisoned by the presence of air. It has been found that even Ru(CO)2(PPh3)3(II) acts as a catalyst for the isomerization of hex-1-ene at room temperature under an inert atmosphere. 相似文献
2.
G. Principi A. Maddalena Ajay Gupta R. Dal Maschio S. Diré 《Hyperfine Interactions》1992,69(1-4):619-622
Conversion electron Mössbauer spectroscopy (CEMS) has been used to study tin oxide films prepared by sol-gel dipping and sputtering. The spectra of films prepared by sol-gel route result close to that of crystalline SnO2 after heat treatment at a temperature as low as 150°C. The Mössbauer parameters of as sputter deposited films indicate that the structure of the deposited stannic oxide has an amorphous character more pronounced for thinner samples. The structure becomes predominantly that of crystalline SnO2 by heating at 550°C for 30 min provided the film thickness is higher than 10 nm. 相似文献
3.
G. Di Francia V. La Ferrara P. Maddalena D. Ninno L. P. Odierna V. Cataudella 《Il Nuovo Cimento D》1996,18(10):1187-1196
Summary In this paper we report on the frequency dependence of the AC conductivity of porous silicon in the range 10 Hz-100 kHz. Two
types of testing devices have been fabricated on three different series of samples formed electrochemically using as a starting
materialptype,n
−-type andn
+-type silicon substrates. For frequencies less than 20-40 kHz the conductivity is found to follow a sublinear frequency dependence.
This behaviour is typical of a carrier transport mechanism determined by an anomalous diffusion process. At higher frequencies
we find that surface states influence the transport mechanism. This suggests a double-channel transport mechanism: one related
to porous-silicon “volume” properties and the other more connected to the “surface” itself.
Paper presented at the III INSEL (Incontro Nazionale sul Silicio Emettiore di Luce) Torino, 12–13 October 1995. 相似文献
4.
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5.
Herbst K Zanello P Corsini M D'Amelio N Dahlenburg L Brorson M 《Inorganic chemistry》2003,42(4):974-981
By reaction of the geometrically incomplete cubane-like clusters [(eta(5)-Cp')(3)Mo(3)S(4))][pts] and [(eta(5)-Cp')(3)W(3)S(4)][pts] (Cp' = methylcyclopentadienyl; pts = p-toluenesulfonate) with group 10 alkene complexes, three new heterobimetallic clusters with cubane-like cluster cores were isolated: [(eta(5)-Cp')(3)W(3)S(4)M'(PPh(3))][pts] ([5][pts], M' = Pd; [6][pts], M' = Pt); [(eta(5)-Cp')(3)Mo(3)S(4)Ni(AsPh(3))][pts] ([7][pts]). The compounds [5][pts]-[7][pts] are completing the extensive series of clusters [(eta(5)-Cp')(3)M(3)S(4)M'(EPh(3))][pts] (M = Mo, W; M' = Ni, Pd, Pt; E = P, As) which allows the consequences of replacing a single type of atom on structural and NMR and UV/vis spectroscopic as well as electrochemical properties to be determined. Single-crystal X-ray structure determinations of [5][pts]-[7][pts] revealed that [5][pts] was not isomorphous to the other members of the series [(eta(5)-Cp')(3)M(3)S(4)M'(EPh(3))][pts] due to distinctly different cell parameters, which in the molecular structure of [5](+) is reflected in a slightly different orientation of the PPh(3) ligand. Electrochemical measurements on the series showed that the Mo-based clusters were more difficult to oxidize than their W-based analogues. The Pd-containing clusters underwent two-electron oxidation processes, whereas the Ni- and Pt-containing clusters underwent two separated one-electron oxidation processes. 相似文献
6.
7.
F. A. Lops F. Maddalena S. Solimini 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2001,18(6):639
The paper deals with the problem of minimizing a free discontinuity functional under Dirichlet boundary conditions. An existence result was known so far for C1(∂Ω) boundary data û. We show here that the same result holds for ûC0,μ(∂Ω) if
and it cannot be extended to cover the case
. The proof is based on some geometric measure theoretic properties, in part introduced here, which are proved a priori to hold for all the possible minimizers. 相似文献
8.
Navin A Anthony DW Aumann T Baumann T Bazin D Blumenfeld Y Brown BA Glasmacher T Hansen PG Ibbotson RW Lofy PA Maddalena V Miller K Nakamura T Pritychenko BV Sherrill BM Spears E Steiner M Tostevin JA Yurkon J Wagner A 《Physical review letters》2000,84(2):266-269
We derive the formalism to obtain spatial distributions of collisional correlation times for macroscopic particles undergoing granular flow from pulsed gradient spin echo nuclear magnetic resonance diffusion data. This is demonstrated with an example of axial motion in the shear flow regime of a 3D granular flow in a horizontal rotating cylinder at one rotation rate. 相似文献
9.
In this paper, we propose a mathematical model with time delay to describe the process of diffusion of a new technology. This model is suitable for modeling diffusion processes of all those technologies that require great initial investments and public subsidies, such as technologies used for producing renewable energy. We consider external factors, such as the government policy and the production costs, that influence the decision of adoption of the new technology. We also consider the internal influence from adopters. The adoption process is described by a delay differential equation. The time delay represents the evaluation stage at which the potential consumers decide whether to adopt the new technology or not. A qualitative analysis is carried out in order to assess the stability of the equilibrium for certain parameters and to find the final level of adopters. 相似文献