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Ab initio calculations are carried out to determine γΠ (true), the first-order contribution to the spin-rotation constant, γΠ, for the X2Π ground states of OH, HF+, and HCl+ and their deuterated analogs. These calculations demonstrate that the contribution of this term to the experimentally determined value of γΠ is small, as has been previously conjectured. Furthermore, it is found in the cases under study that the Van Vleck approximation to γΠ (true) significantly overestimates its importance, and a more realistic approximation is presented. 相似文献
33.
Spatial patterning of thin polyacrylamide films bonded to self-assembled monolayers on silica microchannels is described as a means for manipulating cell-adhesion and electroosmotic properties in microchips. Streaming potential measurements indicate that the zeta potential is reduced by at least two orders of magnitude at biological pH, and the adhesion of several kinds of cells is reduced by 80-100%. Results are shown for cover slides and in wet-etched silica microchannels. Because the polyacrylamide film is thin and transparent, this film is consistent with optical manipulation of cells and detection of cell contents. The spatial patterning technique is straightforward and has the potential to aid on-chip analysis of single adherent cells. 相似文献
34.
Rotationally resolved photoelectron angular distributions from vibrational autoionization of the NO 14s ( nu = 1, N = 20, N(+)(R) = 20) level are measured by photoelectron spectroscopy, and they are analyzed using a theoretical model based on first-order coupling between the Rydberg level and the ionization continuum. The analysis reveals that lambda-changing collisions and l-changing collisions between the molecular-ion core and the outgoing electron are comparable in magnitude and account for 40% of the partial waves produced in the ionization continuum. 相似文献
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Dr. Xiaowei Song Dr. Qingce Zang Dr. Chao Li Dr. Tianhao Zhou Prof. Richard N. Zare 《Angewandte Chemie (International ed. in English)》2023,62(9):e202216969
We present immunoassay-based desorption electrospray ionization mass spectrometry imaging (immuno-DESI-MSI) to visualize functional macromolecules such as drug targets and cascade signaling factors. A set of boronic acid mass tags (BMTs) were synthesized to label antibodies as MSI probes. The boronic ester bond is employed to cross-link the BMT with the galactosamine-modified antibody. The BMT can be released from its tethered antibody by ultrafast cleavage of the boronic ester bond caused by the acidic condition of sprayed DESI microdroplets containing water. The fluorescent moiety enables the BMT to work in both optical and MS imaging modes. The positively charged quaternary ammonium group enhances the ionization efficiency. The introduction of the boron element also makes mass tags readily identified because of its unique isotope pattern. Immuno-DESI-MSI provides an appealing strategy to spatially map macromolecules beyond what can be observed by conventional DESI-MSI, provided antibodies are available to the targeted molecules of interest. 相似文献
37.
The composition of essential oil extracted from Valeriana officinalis L. roots growing wild in Iran was studied by hydrodistillation and supercritical CO2 extraction. Forty-seven components representing 89.3% and 35 constituents varying from 86.1% to 95.1% of the oil obtained by hydrodistillation and supercritical CO2 were identified, respectively. The major components in the extracted oil from supercritical CO2 were isovaleric acid (18.7-41.8%), valerenic acid (8.2-11.8%), acetoxyvaleranone (5.6-9.6%), (Z)-valernyl acetate (4.5-6.5%), bornyl acetate (2.3-7.7%) and valerenol (3.7-5.2%), whereas by hydrodistillation were bornyl acetate (11.6%), valerenic acid (8.0%), (Z)-valernyl acetate (7.9%) and acetoxyvaleranone (7.6%). The analysis of the extracts was performed by capillary GC and GC/MS. 相似文献
38.
D.L. Albritton W.J. Harrop A.L. Schmeltekopf R.N. Zare 《Journal of Molecular Spectroscopy》1973,46(1):25-36
Expressions are developed for computing the centrifugal distortion constants Dv, Hv, and Lv directly from the Rydberg-Klein-Rees rotationless potential of a diatomic molecule. These expressions involve summations over integrals of the wavefunctions of all neighboring vibrational levels. Application is made to the X1Σ+ state of CO and the state of O2. In these applications, we have neglected the contributions of the continuum wavefunctions. For higher vibrational levels, particularly those near the dissociation limit, this approximation would be expected to fail. For the lowest vibrational levels of an electronic state, this method gives the same results for Dv, Hv, and Lv as the Dunham relations. However, for intermediate vibrational levels the present method is an improvement since expressions for only a few coefficients of the Dunham expansion are available. The use of Dv and Hv values calculated from Rydberg-Klein-Rees potentials in an iterative improvement of the reduction of spectroscopic data is described. 相似文献
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