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51.
This study was designed to evaluate changes in erythrocyte contents during endurance moderate intensity exercise, a model of physiological oxidative stress. 16 endurance-trained subjects cycled 2 h at 55% of maximal aerobic capacity and blood was collected every 15 min. Transmission FT-IR spectrometry was used to analyze separately plasma and erythrocyte content changes during oxidative stress. Erythrocyte FT-IR spectra were corrected for hemoconcentration (Hc) before spectral areas integration of main IR absorbances belonging to phospholipids [nu(as)(CH(3)), [nu(as)(CH(2)), and nu(P=O)], proteins [nu(C=O) and delta(N-H)], and lactate [nu(C-O)] were used to determine erythrocyte content changes. Changes in nu(as)(CH(2)) and nu(P=O) absorbances while nu(as)(CH(3)) remained stable showed the magnitude of free radical attacks on phospholipids bilayer. Decrease in nu(C=O) and delta(N-H) absorbances while plasma and intracellular lactate, O(2) consumption, and Hc rose were linked to hemoglobin, and possibly spectrin, denaturation. Finally, the synergistic changes found between physiological, plasmatic and erythrocyte parameters showed that FT-IR spectrometry was a sufficiently accurate and sensitive method to determine acute changes in erythrocytes during moderate, physiological, oxidative stress. 相似文献
52.
Poriel C Ferrand Y Le Maux P Rault-Berthelot J Simonneaux G 《Inorganic chemistry》2004,43(16):5086-5095
Anodic oxidation of free base and manganese complexes of tetraspirobifluorenylporphyrins leads to the coating of the working electrode by insoluble electroactive poly(9,9'-spirobifluorene-free and manganese porphyrin) films which electrochemical behavior and physicochemical properties are described. After removal from the electrode, the manganese-complexed polymers were evaluated as catalysts for the oxidation of alkenes by iodobenzene diacetate or iodosylbenzene. The results show that the reactions proceeded very efficiently at room temperature with good yields. The electrosynthesized polymer catalysts can be recycled by simple filtration and reused even up to the eighth cycle without loss of activity and selectivity. These results represent an important improvement over those previously described for manganese-porphyrin-catalyzed epoxidation reactions. 相似文献
53.
Floquet S Ouali N Bocquet B Bernardinelli G Imbert D Bünzli JC Hopfgartner G Piguet C 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(8):1860-1875
The segmental tris-tridentate ligand L7 reacts with stoichiometric quantities of Ln(III) (Ln=La-Lu) in acetonitrile to give the complexes [Ln(2)(L7)(3)](6+) and [Ln(3)(L7)(3)](9+). Formation constants point to negligible size-discriminating effects along the lanthanide series, but Scatchard plots suggest that the self-assembly of the trimetallic triple-stranded helicates [Ln(3)(L7)(3)](9+) is driven to completion by positive cooperativity, despite strong intermetallic electrostatic repulsions. Crystallization provides quantitatively [Ln(3)(L7)(3)](CF(3)SO(3))(9) (Ln=La, Eu, Gd, Tb, Lu) and the X-ray crystal structure of [Eu(3)(L7)(3)](CF(3)SO(3))(9).(CH(3)CN)(9).(H(2)O)(2) (Eu(3)C(216)H(226)N(48)O(35)F(27)S(9), triclinic, P1, Z=2) shows the three ligand strands wrapped around a pseudo-threefold axis defined by the three metal ions rigidly held at about 9 A. Each metal ion is coordinated by nine donor atoms in a pseudo-trigonal prismatic arrangement, but the existence of terminal carboxamide units in the ligand strands differentiates the electronic properties of the terminal and the central metallic sites. Photophysical data confirm that the three coordination sites possess comparable pseudo-trigonal symmetries in the solid state and in solution. High-resolution luminescence analyses evidence a low-lying LMCT state affecting the central EuN(9) site, so that multi-metal-centered luminescence is essentially dominated by the emission from the two terminal EuN(6)O(3) sites in [Eu(3)(L7)(3)](9+). New multicenter equations have been developed for investigating the solution structure of [Ln(3)(L7)(3)](9+) by paramagnetic NMR spectroscopy and linear correlations for Ln=Ce-Tb imply isostructurality for these larger lanthanides. NMR spectra point to the triple helical structure being maintained in solution, but an inversion of the magnitude of the second-rank crystal-field parameters, obtained by LIS analysis, for the LnN(6)O(3) and LnN(9) sites with respect to the parameters extracted for Eu(III) from luminescence data, suggests that the geometry of the central LnN(9) site is somewhat relaxed in solution. 相似文献
54.
Solladié N Walther ME Gross M Duarte TM Bourgogne C Nierengarten JF 《Chemical communications (Cambridge, England)》2003,(19):2412-2413
In addition to the ammonium-crown ether recognition, pi-stacking interactions between the C60 sphere and the porphyrin moiety have been evidenced in a supramolecular complex obtained from a porphyrin-crown ether conjugate and a fullerene derivative bearing an ammonium unit. 相似文献
55.
Godard C Duckett SB Parsons S Perutz RN 《Chemical communications (Cambridge, England)》2003,(18):2332-2333
UV irradiation of a solution of (eta5-C5H5)bis(ethene)rhodium in the presence of 2,2'-dipyridylketone yields (eta5-C5H5)Rh(kappa2-N,O-2,2'-dipyridylketone) which inserts ethene to yield a bicyclic oxametallacyclopentane. 相似文献
56.
Suárez S Mamula O Imbert D Piguet C Bünzli JC 《Chemical communications (Cambridge, England)》2003,(11):1226-1227
Complexes between lanthanide nitrates and a pro-mesogenic 18-membered diaza-substituted coronand are luminescent both as powders and liquid crystals (between 87 and 195 degrees C), and the phase transitions are detected by monitoring luminescence intensity and lifetime. 相似文献
57.
Rainer Cremer Mirjam Witthaut Dieter Neuschütz Cyril Trappe Martin Laurenzis Olaf Winkler Heinrich Kurz 《Mikrochimica acta》2000,133(1-4):299-302
Cu3N films for optical data storage were deposited on Si(100) wafers and 0.6 mm thick polycarbonate DVD base material discs at
a temperature of 50 °C by reactive magnetron sputtering. A copper target was sputtered in rf mode in a nitrogen plasma. For
basic investigations concerning the composition and structure of Cu3N, Si wafers were used as substrate material. To study the suitability of Cu3N as an optical data storage medium under technical conditions, Cu3N/Al bilayers were deposited on polycarbonate discs. The composition and structure of the films were investigated by X-ray
photoelectron spectroscopy (XPS) and X-ray diffraction (XRD).
The decomposition of Cu3N into metallic copper and nitrogen was induced and characterized with a dynamic tester consisting of an optical microscope
with an integrated high power laser diode. The change in reflectivity induced by the laser pulses was measured by a high sensitivity
photo detector. Optimized Cu3N films could be decomposed into metallic copper at pulse lengths of 200 ns. The reflectivity change from 3.2% to 33.2% for
completely transformed areas and to 12% for single bits as well as the maximum write data rate of 3.3 Mbit/s demonstrated
the suitability of Cu3N for write once optical data storage. Especially the carrier to noise ratio of 41 dB shows an increase of a factor of 3 for
this novel material as compared to conventional optical data storage media. 相似文献
58.
Henri Imbert A. Astruc und Schon früher 《Fresenius' Journal of Analytical Chemistry》1901,40(2):127-129
Ohne Zusammenfassung 相似文献
59.
60.
Cyril Girardin Daniel P. Rasse Philippe Biron Jaleh Ghashghaie Claire Chenu 《Rapid communications in mass spectrometry : RCM》2009,23(12):1792-1800
The molecular composition of plant residues is suspected to largely govern the fate of their constitutive carbon (C) in soils. Labile compounds, such as metabolic carbohydrates, are affected differently from recalcitrant and structural compounds by soil‐C stabilisation mechanisms. Producing 13C‐enriched plant residues with specifically labeled fractions would help us to investigate the fate in soils of the constitutive C of these compounds. The objective of the present research was to test 13C pulse chase labeling as a method for specifically enriching the metabolic carbohydrate components of plant residues, i.e. soluble sugars and starch. Bean plants were exposed to a 13CO2‐enriched atmosphere for 0.5, 1, 2, 3 and 21 h. The major soluble sugars were then determined on water‐soluble extracts, and starch on HCl‐hydrolysable extracts. The results show a quick differential labeling between water‐soluble and water‐insoluble compounds. For both groups, 13C‐labeling increased linearly with time. The difference in δ13C signature between water‐soluble and insoluble fractions was 7‰ after 0.5 h and 70‰ after 21 h. However, this clear isotopic contrast masked a substantial labeling variability within each fraction. By contrast, metabolic carbohydrates on the one hand (i.e. soluble sugars + starch) and other fractions (essentially cell wall components) on the other hand displayed quite homogeneous signatures within fractions, and a significant difference in labeling between fractions: δ13C = 414 ± 3.7‰ and 56 ± 5.5‰, respectively. Thus, the technique generates labeled plant residues displaying contrasting 13C‐isotopic signatures between metabolic carbohydrates and other compounds, with homogenous signatures within each group. Metabolic carbohydrates being labile compounds, our findings suggest that the technique is particularly appropriate for investigating the effect of compound lability on the long‐term storage of their constitutive C in soils. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献