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71.
Michel M Arntz Y Fleith G Toquant J Haikel Y Voegel JC Schaaf P Ball V 《Langmuir : the ACS journal of surfaces and colloids》2006,22(5):2358-2364
The development of chemical reactions in nanospaces is of paramount importance for the development of active nanodevices, particularly in nanofluidics. It has been shown in a previous paper that phospholipid vesicles can be incorporated without spontaneous bilayer rupture into poly-L-glutamic acid/poly(allylamine) (PGA/PAH) multilayered polyelectrolyte films. The aim of the present study was to use such a system as an "embedded submicronic reactor" able to trigger precipitation of calcium phosphates within closed spaces through an enzymatic reaction, the enzyme also being encapsulated in the vesicle interior. To this aim, large unilamellar vesicles (LUVs) were produced containing calcium ions as active ions in the mineralization process, spermine as an activator of crystal growth, and alkaline phosphatase as a catalyst to convert phosphate esters into phosphates. After stabilization by adding a layer of poly-(D-lysine), these vesicles were embedded in a (PGA-PAH)n film. A paranitrophenyl phosphate containing solution was then put in contact with this film. It is shown by means of infrared spectroscopy in the attenuated total reflection mode that, consecutively to this contact, calcium phosphates are growing inside the embedded vesicles. By using scanning near-field fluorescence microscopy, it is demonstrated that the alkaline phosphatase enzymes are most probably located inside the vesicles after their embedding. In addition, atomic force microscopy was used to show, after chemical removal of the organic top layer of the film, that the inorganic platelets produced after the precipitation reaction are localized in volumes of similar size and shape as that of the vesicles into which the phosphate ester hydrolysis and subsequent precipitation reaction did occur. 相似文献
72.
Abstract. We formulate a robust optimal stopping-time problem for a state-space system and give the connection between various notions
of lower value function for the associated games (and storage function for the associated dissipative system) with solutions
of the appropriate variational inequality (VI) (the analogue of the Hamilton—Jacobi—Bellman—Isaacs equation for this setting).
We show that the stopping-time rule can be obtained by solving the VI in the viscosity sense and a positive definite supersolution
of the VI can be used for stability analysis. 相似文献
73.
Cornelis Lensink Graeme J. Gainsford Neville I. Baxter 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(4):366-367
The title compound, [Ti(CF3O3S)2(C14H15NO2S)(C4H8O)], contains a unique ligand system in which the Ti ion is bound to the N and O atoms of a 2‐p‐toluenesulfonamide ligand, which is linked by an ethyl group to a coordinated cyclopentadiene moiety. The distorted octahedral geometry about the Ti ion is completed by two trifluoromethanesulfonate ligands and a tetrahydrofuran molecule. Comparison with related compounds shows that both the Ti—N and Ti—O bonds of the sulfonamide, although longer than normal values, indicate significant bonding interactions. 相似文献
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77.
Harding DJ Gruene P Haertelt M Meijer G Fielicke A Hamilton SM Hopkins WS Mackenzie SR Neville SP Walsh TR 《The Journal of chemical physics》2010,133(21):214304
The geometric structures of small cationic rhodium clusters Rh(n)(+) (n = 6-12) are investigated by comparison of experimental far-infrared multiple photon dissociation spectra with spectra calculated using density functional theory. The clusters are found to favor structures based on octahedral and tetrahedral motifs for most of the sizes considered, in contrast to previous theoretical predictions that rhodium clusters should favor cubic motifs. Our findings highlight the need for further development of theoretical and computational methods to treat these high-spin transition metal clusters. 相似文献
78.
Jarrod J. M. Amoore Dr. Suzanne M. Neville Dr. Boujemaa Moubaraki Dr. Simon S. Iremonger Dr. Keith S. Murray Prof. Jean‐François Létard Dr. Cameron J. Kepert Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(6):1973-1982
We previously reported the dinuclear material [FeII2(ddpp)2(NCS)4] ? 4 CH2Cl2 ( 1? 4 CH2Cl2; ddpp=2,5‐di(2′,2′′‐dipyridylamino)pyridine) and its partially desolvated analogue ( 1? CH2Cl2), which undergo two‐ and one‐step spin‐crossover (SCO) transitions, respectively. Here, we manipulate the type and degree of solvation in this system and find that either a one‐ or two‐step spin transition can be specifically targeted. The chloroform clathrate 1? 4 CHCl3 undergoes a relatively abrupt one‐step SCO, in which the two equivalent FeII sites within the dinuclear molecule crossover simultaneously. Partial desolvation of 1? 4 CHCl3 to form 1? 3 CHCl3 and 1? CHCl3 occurs through single‐crystal‐to‐single‐crystal processes (monoclinic C2/c to P21/n to P21/n) in which the two equivalent FeII sites become inequivalent sites within the dinuclear molecule of each phase. Both 1? 3 CHCl3 and 1? CHCl3 undergo one‐step spin transitions, with the former having a significantly higher SCO temperature than 1? 4 CHCl3 and the latter, and each has a broader SCO transition than 1? 4 CHCl3, attributable to the overlap of two SCO steps in each case. Further magnetic manipulation can be carried out on these materials through reversibly resolvating the partially desolvated material with chloroform to produce the original one‐step SCO, or with dichloromethane to produce a two‐step SCO reminiscent of that seen for 1? 4 CH2Cl2. Furthermore, we investigate the light‐induced excited spin state trapping (LIESST) effect on 1? 4 CH2Cl2 and 1? CH2Cl2 and observe partial LIESST activity for the former and no activity for the latter. 相似文献
79.
R. J. Ball G. C. Allen G. Starrs W. J. McCarter 《Applied Physics A: Materials Science & Processing》2011,105(3):739-751
The conduction and dielectric behaviour of two different grades of natural hydraulic lime is presented over the frequency
range 1 Hz–1 MHz, with measurements taken over the initial six months after gauging with water. Samples containing embedded
electrodes were exposed to both a natural atmosphere (20°C and 65% relative humidity) and a natural atmosphere with a carbon
dioxide concentration maintained at 400 ppm which was used to accelerate the carbonation process. A decrease in relative dielectric
permittivity and rise in conductivity, with increasing frequency, was observed at all stages over the time-scale presented.
When plotted in the complex plane, the impedance featured a bulk response comprising two depressed semicircles and a low frequency
spur, the latter being associated with the electrode/sample interface. The complex impedance plot, together with the application
of an equivalent circuit model, indicated a dual arc feature with carbonation and hydration contributing to bulk impedance
response. This study demonstrates the applicability of electrical property measurements to monitor the combined processes
of hydration and carbonation in this group of materials. 相似文献
80.
A. Gorelov J.A. Behr D. Melconian M. Trinczek P. Dubé O. Häusser U. Giesen K.P. Jackson T. Swanson J.M. D'Auria M. Dombsky G. Ball L. Buchmann B. Jennings J. Dilling J. Schmid D. Ashery J. Deutsch W.P. Alford D. Asgeirsson W. Wong B. Lee 《Hyperfine Interactions》2000,127(1-4):373-380
Laser trapping and cooling techniques are now being applied to the study of nuclear β-decay at several labs. A magneto-optical
trap (MOT) provides a localized source of atoms suspended in space, so the low-energy recoiling nuclei can freely escape and
be detected in coincidence with the β. This allows reconstruction of the neutrino momentum, and the deduction of the β-v correlation in a more direct fashion than previously possible. In addition, the nuclei can be polarized by atomic techniques,
opening a new class of spin correlation measurements to test the degree to which parity is maximally violated in the weak
interaction. Our present experiment has detected several hundred thousand recoil-β+ coincidences from the 0+ → 0+ pure Fermi decay of 38mK, produced at the on-line isotope separators TISOL and ISAC at TRIUMF. Our goal is to set constraints on non-Standard Model
scalar bosons competitive with high-energy colliders and more conventional β-v correlation experiments.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献