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61.
Self-assembled nanocages for hydrophilic guest molecules 总被引:1,自引:0,他引:1
Jones MC Tewari P Blei C Hales K Pochan DJ Leroux JC 《Journal of the American Chemical Society》2006,128(45):14599-14605
Reverse polymeric micelles are obtained following the association of polymeric amphiphiles in apolar media. To this date, reports of pharmaceutical applications for such micelles have been scarce, mainly because these systems have been studied in solvents that are not suitable for medical use. Here, alkylated star-shaped poly(glycerol methacrylate) polymers have been proposed in the design of oil-soluble reverse polymeric micelles. Micellar behavior was studied in various apolar solvents, including ethyl oleate, a pharmaceutically acceptable vehicle. The polymers were shown to assemble into spherical nanostructures (<40 nm) as determined by cryogenic transmission electron microscopy and atomic force microscopy studies. Interestingly, the reverse micelles were able to encapsulate various peptides/proteins (vasopressin, myoglobin, and albumin) in substantial amounts and facilitate their solubilization in oil. The nature of both the polymer used in micelle formation and the guest molecules was found to influence the ability of the micelle to interact with hydrophilic compounds. 相似文献
62.
Stefan Bode Claudia C. Quentmeier Pen-Nan Liao Tiago Barros Peter J. Walla 《Chemical physics letters》2008,450(4-6):379-385
The Car S1 → Chl energy transfer efficiency, ΦTransfer, in xanthophyll-cycle mutants of living plants and LHC II was investigated by selective Car S1 two-photon excitation. Before high-light illumination ΦTransfer, of the violaxanthin deficient mutant npq2 is 30% smaller than the corresponding value for wild type plants. For the zeaxanthin deficient mutant, npq1, ΦTransfer is 30% larger. Wild type Arabidopsis thaliana is the only variant which is capable of a light-dependent decrease of up to 40% and complete recovery to the original ΦTransfer values. In contrast, ΦTransfer remains constant during dark adaptation in both mutants. Surprisingly, changes in ΦTransfer of LHC II preparations were less than 5% only, when substituting violaxanthin by zeaxanthin. 相似文献
63.
Coexisting lamellar phases in water-oil-surfactant systems induced by the addition of an amphiphilic block copolymer 总被引:1,自引:0,他引:1
We report here a pioneering study using quadrupolar splitting NMR to detect new phases and phase compositions in the quasi-ternary microemulsion system water-decane-C(10)E(4)/PEP5-PEO5. The striking observation is that at certain compositions the polymer is apparently no longer incorporated into the membranes of the lamellar phase due to space restrictions. The polymer therefore induces a phase separation into two different lamellar phases L(alpha)(1) and L(alpha)(2) such that it fits into L(alpha)(1) while the excess surfactant forms a polymer-free L(alpha)(2) phase. 相似文献
64.
65.
A high-performance liquid chromatography (HPLC) method was established using an analytical reversed-phase column and gradient
elution to achieve chromatographic separation of typical compounds in essential oils. For detection, a diode array detector
monitoring different wavelengths simultaneously as well as a mass spectrometer (MS) were used. Atmospheric pressure chemical
ionization operating in the positive mode turned out to be a suitable tool to detect volatiles of different chemical classes
and to identify them in essential oil matrices. Characteristic fingerprints of eucalyptus, lavender, may chang, pine, rosemary,
thyme, and turpentine essential oils monitored at a representative wavelength (220 nm) demonstrated the suitability of HPLC
in essential oil analysis. Additional monitoring wavelengths (210, 250, and 280 nm) provided useful information about the
identity of the specific component and opened the possibility to differentiate presumably coeluting compounds by means of
their distinct absorption behavior. Finally, peak assignment in seven essential oils was performed on the basis of characteristic
retention times and UV and MS data of a broad set of reference volatiles. 相似文献
66.
67.
Karina González‐Segura Paulina Cañete‐Rosales Rodrigo del Rio Claudia Yáñez Nancy F. Ferreyra Gustavo A. Rivas Soledad Bollo 《Electroanalysis》2012,24(12):2317-2323
The electrochemical response of a glassy carbon electrode modified with carbon nanotubes (CNT) dispersed in two solvents, water and DMF, and two polymers, chitosan and Nafion is reported. The films were homogeneous when the dispersing agent was water or DMF. In the case of polymers, the surfaces present areas with different density of CNTs. A more sensitive electrochemical response was obtained when CNTs are dispersed in the solvents. In the case of CNT dispersed with polymers, the nature of the polymer demonstrated to be a critical parameter not only for dispersing the nanotubes but also for the electrochemical activity of the resulting electrodes. 相似文献
68.
A one-pot synthesis of poly-substituted tetramic acids and of their six-membered ring analogs have been obtained in one step by reaction of N-Boc dipeptides, activated as their O-succinimidyl esters (Boc-AA-AA-OSu), with the sodium anion of dibenzyl malonate. The adducts spontaneously cyclize to form five or six-member rings. To check whether this class of compounds may be used to promote reverse-turn conformations, one adduct was further derivatized. The formation of a hydrogen bond between the NH–Boc and the carbonyl at C2 of the heterocycle is highlighted, upon analysis of the product by IR, 1H NMR, and MD techniques, thus suggesting that these compounds are good candidates to promote reverse-turn conformations or other secondary structures and may be used for the formation of new foldamers. 相似文献
69.
Andrea D. Beck David G. Flad Claudia Tonhäuser Gregor Gassner Claus-Dieter Munz 《Flow, Turbulence and Combustion》2016,97(2):475-511
In this work we investigate the interplay of polynomial de-aliasing and sub-grid scale models for large eddy simulations based on discontinuous Galerkin discretizations. It is known that stability is a major concern when simulating underresolved turbulent flows with high order nodal collocation type discretizations. By changing the interpolatory character of the nodal collocation type discretization to a projection based discretization by increasing the number of quadrature points (polynomial de-aliasing), one is able to remove the aliasing induced stability problems. We focus on this effect and on the consequence for large eddy simulations with explicit subgrid scale models. Often, subgrid scale models have to achieve two possibly conflicting tasks in a single simulation: firstly stabilizing the numerics and secondly modeling the physical effect of the missing scales. Within a discontinuous Galerkin approach, it is possible to use either a fast (but potentially aliasing afflicted) nodal collocation discretization or a projection-based (but computationally costly) variant in combination with an explicit subgrid scale model. We use this framework to investigate the effect on the appropriate model parameter of a standard Smagorinsky subgrid scale model and of a Variational Multiscale Smagorinsky formulation. For this we first consider the 3-D viscous Taylor-Green vortex example to investigate the impact on the stability of the method and second the turbulent flow past a circular cylinder to investigate and compare the accuracy of the results. We show that the aliasing instabilities of collocative discretizations severely limit the choice of the model constant, in particular for high order schemes, while for de-aliased DG schemes, the closure model parameters can be chosen independently from the numerical scheme. For the cylinder flow, we also find that for the same model settings, the projection-based results are in better agreement with the reference DNS than those of the collocative scheme. 相似文献
70.
Daniele Cauzzi Claudia Graiff Chiara Massera Giovanni Predieri Antonio Tiripicchio 《Journal of Cluster Science》2001,12(1):259-271
The reaction of [Ru3(CO)12] with Ph2(pyth)PSe (pyth=5-(2-pyridyl)-2-thienyl) allows to obtain two novel clusters [Ru3(3-Se)2(CO)7{P(pyth)Ph2}2] 1 and [Ru3(3-Se)(-PPh2)(-pyth)(CO)6{P(pyth)Ph2}] 2 in satisfactory yields. The first one exhibits the well-known bicapped, open triangular, 50-electron nido-core, whereas 2, whose crystal structure has been determined, shows the rather rare Ru3Se tetrahedron with the Ph2P and pyth fragments as side-bridging ligands. Morever cluster 2 belongs to the exiguous family of selenido-phosphido clusters not easily achievable by other routes. 相似文献