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91.
The development of NMR diffusion imaging and diffusion tensor imaging (DTI) has offered the possibility of studying the porous structures beyond anatomical imaging. In fact, random molecular motions, within tissue components, probe tissue microstructures. Up to now, the DTI method was mainly used to investigate cerebral morphology and study white matter diseases. In this study, it has been applied to trabecular bone marrow analysis to obtain structural information on spongy bone tissue. Our first results show that DTI could represent an important tool in studying the microstructural architecture of the trabecular bone as well as the microarchitecture of porous media. 相似文献
92.
Bianco A Guiso M Nicoletti M Foddai S Piccin A Serafini M Ballero M Poli F 《Natural product research》2005,19(6):615-617
The phytochemical analysis of iridoidic fraction of the aerial parts of Vinca sardoa and Vinca difformis, gave the identification of loganic acid in V. difformis as unique iridoid glucoside, while loganin is also present in V. sardoa. The two taxa highly differ in alkaloids, so the chemotaxonomic classification in two different species is supported. 相似文献
93.
M. Ambrosio G. Anzivino G. Barbarino U. Becker G. Carboni V. Cavasinni T. Del Prete G. Kantardjian D. Lloyd Owen M. Morganti J. Paradiso G. Paternoster S. Patricelli M. Steuer M. Valdata-Nappi 《Physics letters. [Part B]》1982,113(4):347-352
We measured the elastic scattering of and of αp at . For αα, the differential cross section dσ/dt has a diffractive pattern minima at |t| = 0.10 and 0.38 GeV2. At small |t| = 0.05?0.07 GeV2, this cross section behaves like exp[(100 ± 10) t]. Extrapolating a fit to the data to the optical point, we obtained for the total cross section αtot(αα) = 250 ± 50 mb and an integrated elastic cross section σe1(αα) = 45 ± mb. Another method of estimating σtot(αα), based on measuring the interaction rate, yielded 295 ± 40 mb. For αp, dσ/dt has aminimum at |t| = 0.20 GeV2, and for 0.05 < |t| < 0.18 GeV2 behaves like exp[(41 ± 2) t]. Extrapolating this slope to |t| = 0, we found σtot(αp) = 130 ± 20 and σe1(αp) = 20 ± 4mb. Results on pp elastic scattering at agree with previous ISR experiments. 相似文献
94.
G. Barbiellini A. Barletta M. Ambrosio G. Barbarino M. Castellano G. Paternoster S. Patricelli L. Tortora U. Troya C. Bemporad G. Brosco M. Calvetti F. Costantini G.R. Giannini P. Lariccia R. Biancastelli 《Physics letters. [Part B]》1977,68(4):397-401
We present experimental evidence for a resonant behaviour of the hadron production from e+e? annihilations at the e+e? storage ring ADONE. A Breit-Wigner fit to the enhancement present between 1800 and 1850 MeV gives the following parameters M = 1812?13+7 MeV, Γ = 34?15+21 MeV. 相似文献
95.
In recent years, significant advances have clarified the mechanism of photosensitized oxidations (see, for example, Foote, 1968), especially as regards the nature of the reactive oxidizing agents. This fact stimulated the development of reaction systems which allow selective photooxidation of specific components of biological macromolecules (Spikes and Livingston, 1969; Spikes and MacKnight, 1970). In the field of proteins, the selective conversion of the methionyl residues to the sulfoxide can be achieved by irradiation with visible light in the presence of hematoporphyrin at neutral or acid pH (Jori et al. , 1969). 相似文献
96.
Aloisi GG Barbafina A Canton M Dall'Acqua F Elisei F Facciolo L Latterini L Viola G 《Photochemistry and photobiology》2004,79(3):248-258
This article describes the results of a combined photophysical and photobiological study aimed at understanding the phototoxicity mechanism of the antimalarial drugs quinine (Q), quinacrine (QC) and mefloquine (MQ). Photophysical experiments were carried out in aqueous solutions by stationary and time-resolved fluorimetry and by laser flash photolysis to obtain information on the various decay pathways of the excited states of the drugs and on transient species formed on irradiation. The results obtained showed that fluorescence and intersystem crossing account for all the adsorbed quanta for Q and MQ (quantum yield of about 0.1 and 0.9, respectively) and only for 24% in the case of QC, which has a negligible fluorescence quantum yield (0.001). Laser flash photolysis experiments evidenced, for QC and MQ, the occurrence of photoionization processes leading to the formation of the radical cations of the drugs. The effects of tryptophan and histidine on the excited states and transient species of the three drugs were also investigated. In parallel, the photoactivity of the antimalarial drugs was investigated under UV irradiation on various biological targets through a series of in vitro assays in the presence and in the absence of oxygen. Phototoxicity on 3T3 cultured fibroblasts and lipid photoperoxidation were observed for all the drugs. The photodamage produced by the drugs was also evaluated on proteins by measuring the photosensitized cross-linking of spectrin. The combined approaches were proven to be useful for understanding the mechanism of phototoxicity induced by the antimalarial drugs. 相似文献
97.
Use of peptide nucleic acid probes for detecting DNA single-base mutations by capillary electrophoresis 总被引:1,自引:0,他引:1
Peptide nucleic acid (PNA) oligomers can be used as probes in pre-gel hybridization experiments, as an alternative to Southern hybridization. In this technique, the PNA probe is hybridized to a cyanine-5 labeled DNA sample denatured at low ionic strength, and the mixture is directly injected for size separation into a capillary electrophoresis (CE) system equipped with laser-induced fluorescence (LIF) detector. The neutral backbone of PNA allows hybridization to occur at low ionic strength and assures an efficient CE separation of the PNA/DNA hybrids from both double-stranded and single-stranded DNA. We have used as a model system the cystic fibrosis R553X and R1162X single-base mutations and we have assessed the influence of various factors, such as temperature and denaturants concentration on DNA/PNA hybrid stability in order to achieve the high specificity required for a single base pair discrimination. 相似文献
98.
Giuseppina Castronuovo Vittorio Elia Marcella Niccoli Filomena Velleca 《Journal of inclusion phenomena and macrocyclic chemistry》2002,44(1-4):229-234
The formation of complexes of -cyclodextrin with 1,2-alkanediols, ,-alkanediols and some cycloalkanols has been studied calorimetrically at 25 °C in water, in 7 mol kg-1 aqueous urea and in 3 mol kg-1 aqueous glucose. When a complex is formed, calorimetry enables the calculation of both the enthalpy and the association constant, from which the free energy and the entropy of the process can be obtained. The forces involved in the association process are discussed in the light of the signs and values of the thermodynamic parameters obtained. The effect of the variation of the aqueous medium on the hydration of the interacting substances and the consequent changes in the association parameters have been investigated. As respect to water, complexes are less stable in urea and more stable in glucose. The analysis of the data shows that this is the result of a different enthalpy-entropy balance in the two solvent media. Deaquation of the interacting substances plays a major role in determining the stability of the inclusion complexes. 相似文献
99.
Dr. David Schweinfurth Marcella Mazzolini Dr. Dmytro Neshchadin Carolin Hoyer Roman Geier Dr. Karl Gatterer Dr. Nils Trapp Prof. Dr. Georg Gescheidt Prof. Dr. François Diederich 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(21):7152-7157
The synthesis of redox‐active p‐ and o‐quinones 2‐phenylamino‐4‐phenylimino[6]helicene‐1‐one 1 , 2‐phenylamino[6]‐helicene‐1,4‐dione 2 , and 4‐phenyl[6]helicene‐1,2‐dione 3 in their enantiopure forms by post‐functionalization of (P)‐ and (M)‐1,2‐dimethoxy[6]helicene is presented. Structural characterization in solution and in the solid state was accomplished by 2D NMR spectroscopy methods and X‐ray diffraction analysis, respectively. Interpretation of electrochemical redox data was accompanied by a detailed orbital picture, derived from DFT calculations. The electronic structures of compounds 1 – 3 were investigated by UV/Vis and electronic circular dichroism (ECD) spectroscopy, complemented by TD‐DFT calculations. Quinones 1 – 3 were chemically reduced to study the EPR signatures of their respective radical anions. DFT methods were used for the atom assignment of the hyperfine coupling constants. The results are discussed within the context of electrochromic chiral switches and molecular recognition. 相似文献