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421.
Chung CY Cheng CW Lee YP Liao HY Sharp EN Rupper P Miller TA 《The Journal of chemical physics》2007,127(4):044311
We have recorded several rovibronic bands of CH3OO and CD3OO in their A<--X transitions in the range of 1.18-1.40 microm with the cavity ringdown technique. While the electronic origins for these species have been reported previously, many newly observed rovibronic bands are described here. The experimental vibrational frequencies (given as nu in the unit cm(-1) in this paper) for the COO bending (nu8) and COO symmetric stretching (nu7) modes in the A state are 378 and 887 cm(-1) for CH3OO, and 348 and 824 cm(-1) for CD3OO, respectively. In addition, two other vibrational frequencies were observed for the A state of CD3OO, namely, nu5 (954 cm(-1)) and nu6 (971 cm(-1)). These experimental vibrational frequencies for the A state of both CH3OO and CD3OO are in good agreement with predictions from quantum-chemical calculations at the UB3LYP/aug-cc-pVTZ level. The enhanced activity of the nu5 vibrational mode in CD3OO is rationalized by mode mixing with the nu7 mode, as supported by calculations of multidimensional Franck-Condon factors. In addition, many hot bands involving the methyl torsional mode (nu12) are observed for both normal and deuterated methyl peroxy. These bands include the "typical" sequence transitions and some "atypical" ones due to the nature of the eigenvalues and eigenfunctions which are a consequence of the low, but very different, torsional barriers in the X and A states. In addition, the 12(2)2 band in CH3OO and the 12(3)3 band in CD3OO show quite different structures than the origin bands, an effect which results from tunneling splittings comparable to the rotational contour. 相似文献
422.
This paper compares different buffer systems for the electrophoretic separation of the five most abundant serum proteins on native-PAGE gel and cellulose membranes. A modified Tris-tricine system was shown to be superior for the separation of these serum proteins in a 7% m/v native-PAGE gel as compared with the traditionally used Tris-glycine and Tris-tricine methods. This modified Tris-tricine buffer system was also employed for the separation of serum proteins using a cellulose acetate membrane and very effective separation was observed as compared with the traditionally used Tris-barbital and Tris-glycine buffer systems. 相似文献
423.
Oxaliplatin is an important anti-cancer drug that has been approved for the treatment of colorectal cancer. It is known that
oxaliplatin, like other Pt-based drugs, interacts with DNA to form cytotoxic Pt-DNA adducts that disrupt important biological
processes such as DNA replication and protein synthesis. Linear ion trap electrospray ionisation mass spectrometry (ESI-MS)
was employed to study the interaction of oxaliplatin with DNA nucleobases. It was shown that oxaliplatin formed adducts with
all four DNA nucleobases when present individually and in combination in solution. Multiple-stage tandem mass spectrometry
(MSn) enabled the fragmentation pathways of each adduct to be established. In addition, proposed structures for each product ion
were obtained from the MS data. When all four bases were present together with the drug at near-equal molar concentrations,
adducts containing predominantly adenine and guanine were formed, confirming that the drug preferentially binds to these nucleobases.
A large molar excess of drug was required to ensure the formation of cytosine and thymine adducts in the presence of adenine
and guanine. Even with a large excess of oxaliplatin, only mono-adducts of these nucleobases were observed when all four nucleobases
were present.
Figure Schematic of a linear ion trap mass spectrometer being used to isolate the diadduct of guanine with oxaliplatin showing the
characteristic isotope pattern due to 194Pt, 195Pt and 196Pt. 相似文献
424.
Hydrodynamic and mass transfer studies in an external-loop air-lift bioreactor for immobilized animal cell culture 总被引:1,自引:0,他引:1
Noreen A. Sharp Andrew J. Daugulis Mattheus F. A. Goosen 《Applied biochemistry and biotechnology》1998,73(1):59-77
Air-lift bioreactors containing suspended or immobilized animal cells have been used for the production of a variety of high-value
biologicals. In the bioprocessing industry, there is a need to study and quantify the relationships between bioreactor-system
properties such as mixing, flow, mass transfer, and cell processes. In the present study, the performance of a 1-L external-loop
air-lift bioreactor was investigated by studying gas-liquid oxygen transfer, mixing time, liquid velocity and gas hold-up
at various aeration rates. These studies were performed over a range (0-25%) of loadings of small (500-800 μm) calcium alginate
beads to investigate the effect of using various concentrations of cell immobilization matrices on the physical properties
of the system. At an aeration rate of 0.5 vvm, the mixing time was decreased by 50%, from 75 s at 0% bead loading to 38 s
at 10% bead loading. A minimum liquid velocity of 10 cm/s was required to keep the alginate beads in suspension. As bead loading
increased, flow within the reactor went from turbulent conditions to the transition zone. At all bead loadings tested, the
gas hold-up increased by only 2% with an increase in aeration rate from 0.1 to 1.0 vvm, regardless of whether the total reactor
volume (i.e., liquid and beads) or the liquid volume was used in calculating the hold-up. A mathematical correlation was developed
for expressing the dependence of the volumetric mass-transfer coefficient, k1a, on aeration rate (vvm) and microbead loading. With this equation it was possible to predict, within 20%, the k1a knowing the gas-flow rate and the volume percentage of microbeads present in the bioreactor. A theoretical study was also
performed to calculate the oxygen transfer from the bulk liquid to the center of microcapsules containing animal cells using
experimental k1a data. The results suggest that whereas there is no oxygen limitation at 10 to 15% microcapsule loading, there is a potential
mass-transfer problem at 25% loading if the bioreactor is operated at an aeration rate of less than 1.06 vvm. 相似文献
425.
Let \(\Gamma \) be a (non-elementary) convex co-compact group of isometries of a pinched Hadamard manifold X. We show that a normal subgroup \(\Gamma _0\) has critical exponent equal to the critical exponent of \(\Gamma \) if and only if \(\Gamma /\Gamma _0\) is amenable. We prove a similar result for the exponential growth rate of closed geodesics on \(X/\Gamma \). These statements are analogues of classical results of Kesten for random walks on groups and Brooks for the spectrum of the Laplacian on covers of Riemannian manifolds. 相似文献
426.
Instead of maintaining the original ideal of having a broad scientific basis for practical Operational Research, it is suggested that the O.R. community has uncritically accepted a myth which views O.R. as a "Hard" (Physical or even Mathematical) Science. It is argued that this has had profound consequences which explain the present difficulties O.R. workers have with problems involving major Social or Behavioural features. It is concluded that the "Hard" Science myth must be replaced, and a return made to the original conception of O.R., if we are to assist effectively in the complex social issues we face today. 相似文献
427.
Min Wang Vasilis Nikolaou Anna Loiudice Ian D. Sharp Antoni Llobet Raffaella Buonsanti 《Chemical science》2022,13(43):12673
Copper-based tandem schemes have emerged as promising strategies to promote the formation of multi-carbon products in the electrocatalytic CO2 reduction reaction. In such approaches, the CO-generating component of the tandem catalyst increases the local concentration of CO and thereby enhances the intrinsic carbon–carbon (C–C) coupling on copper. However, the optimal characteristics of the CO-generating catalyst for maximizing the C2 production are currently unknown. In this work, we developed tunable tandem catalysts comprising iron porphyrin (Fe-Por), as the CO-generating component, and Cu nanocubes (Cucub) to understand how the turnover frequency for CO (TOFCO) of the molecular catalysts impacts the C–C coupling on the Cu surface. First, we tuned the TOFCO of the Fe-Por by varying the number of orbitals involved in the π-system. Then, we coupled these molecular catalysts with the Cucub and assessed the current densities and faradaic efficiencies. We discovered that all of the designed Fe-Por boost ethylene production. The most efficient Cucub/Fe-Por tandem catalyst was the one including the Fe-Por with the highest TOFCO and exhibited a nearly 22-fold increase in the ethylene selectivity and 100 mV positive shift of the onset potential with respect to the pristine Cucub. These results reveal that coupling the TOFCO tunability of molecular catalysts with copper nanocatalysts opens up new possibilities towards the development of Cu-based catalysts with enhanced selectivity for multi-carbon product generation at low overpotential.Coupling the tunability of molecular catalysts and copper nanocatalysts opens up new possibilities towards the development of Cu-based catalysts with enhanced selectivity for multi-carbon product generation at low overpotential. 相似文献
428.
429.
J. A. Sharp 《The Journal of the Operational Research Society》1987,38(4):319-328
A project to reduce the despatch costs of a manufacturer is described. This involved the construction of a model that would enable the lowest-cost haulier to be selected and answer the question of which of that haulier's depots should be used to handle the despatches. The existing information system did not generate the necessary data for the regular use of a model based on actual despatches. Furthermore, the pattern of demand was fairly volatile, so that the least-cost haulier might have been expected to change quite often. Therefore, the use of the analytic hierarchy process to derive the necessary data was explored. Attempts were made to compare the results of a complete census of traffic carried out in the initial stage of the project with the data obtained from the analytic hierarchy process. 相似文献
430.
In this note, we discuss an analogue of the Weil–Petersson metric for spaces of metric graphs and some of its properties. 相似文献