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981.
Makarova L. I. Sergienko N. V. Trankina E. S. Zhdanov A. A. Ahmet"eva E. A. 《Russian Chemical Bulletin》2003,52(1):170-172
The reactions of [(2-acetoxyetoxy)methyl]dimethylchlorosilane and 1-acetoxy-2-(dimethylchlorosilylmethoxy)benzene with the cage phenylcopper and phenylmanganese siloxanes leads to the cleavage of the M—O—Si bond to give metal chlorides and six-unit cyclosiloxanes with an acetoxy group in the organic substituent at the silicon atom. Methanolysis of these acetoxy derivatives does not affect the ring structure and affords the corresponding polyhydric alcohols. 相似文献
982.
Liu Y Chen SH Berti D Baglioni P Alatas A Sinn H Alp E Said A 《The Journal of chemical physics》2005,123(21):214909
The phonon propagation and damping along the axial direction of films of aligned 40 wt % calf-thymus DNA rods are studied by inelastic x-ray scattering (IXS). The IXS spectra are analyzed with the generalized three effective eigenmode theory, from which we extract the dynamic structure factor S(Q,E) as a function of transferred energy E=variant Planck's over 2piomega, and the magnitude of the transferred wave vector Q. S(Q,E) of a DNA sample typically consists of three peaks, one central Rayleigh scattering peak, and two symmetric Stokes and anti-Stokes Brillouin side peaks. By analyzing the Brillouin peaks, the phonon excitation energy and damping can be extracted at different Q values from about 4 to 30 nm(-1). A high-frequency sound speed is obtained from the initial slope of the linear portion of the dispersion relation below Q=4 nm(-1). The high-frequency sound speed obtained in this Q range is 3100 ms, which is about twice faster than the ultrasound speed of 1800 ms, measured by Brillouin light scattering at Q approximately 0.01 nm(-1) at the similar hydration level. Our observations provide further evidence of the strong coupling between the internal dynamics of a DNA molecule and the dynamics of the solvent. The effect on damping and propagation of phonons along the axial direction of DNA rods due to divalent and trivalent counterions has been studied. It is found that the added multivalent counterions introduce stronger phonon damping. The phonons at the range between approximately 12.5 and approximately 22.5 nm(-1) are overdamped by the added counterions according to our model analyses. The intermediate scattering function is extracted and it shows a clear two-step relaxation with the fast relaxation time ranging from 0.1 to 4 ps. 相似文献
983.
In this study the V2O5/-Al2O3 catalysts were prepared by the grafting method. Their Brönsted and Lewis acid sites were investigated with pyridine adsorption using infrared spectroscopic techniques. It was concluded that when the catalysts composition of the active component V2O5 increased, the supporting material -Al2O3 was covered by a monolayer of V2O5. When the amount of active component was over 11.8 wt.%, the supporting material was covered as multilayer.It was also concluded that after pyridine adsorption, the number of Lewis acid sites of V2O5/-Al2O3 catalyst decreased with increasing V2O5 content. The number of the Brönsted acid sites of the V2O5/-Al2O3 catalyst showed an increase with increasing V2O5 content and reached a maximum for the catalyst with 11.8 wt.% V2O5. Upon further increase of V2O5 content, the number of the Brönsted acid sites decreased. 相似文献
984.
Bis(fluorenyl)dimethylzirconium has been prepared from fluorene, methyllithium and zirconium tetrachloride by a new and convenient route. The compound was characterized by elemental analysis, proton NMR and mass spectrometry. Photolysis of bis(fluorenyl)dimethylzirconium in solution leads to cleavage of the methyl groups, with formation of methane and a bis(fluorenyl)zirconium-type compound of possible polynuclear nature. Infrared studies using specifically deuterated analogs have shown that this process occurs, at least in part, by intramolecular proton abstraction from theπ-coordinated fluorenyl rings. 相似文献
985.
The reactions of 4-hydroxy-5-oximino-3-thiophenecarboxylates with hydrazine and substituted hydrazines have been investigated. The products of the reactions have been shown to be pyrazole-3- or 5-thiohydroxamic acids rather than the hydrazones previously described by Benary and Silberstrom. Two alternate mechanisms are proposed which account for the regiochemical outcome. The structures of the pyrazole-3- and 5-thiohydroxamic acids and corresponding nitriles have been proven by independent synthesis, comparison to known compounds, and by proton and carbon magnetic resonance and long range HETCOR experiments. 相似文献
986.
987.
988.
Whei Oh Lin Maria C. Bastos Vieira de Souza Antonio P. Altoé Helmut G. Alt 《Monatshefte für Chemie / Chemical Monthly》1983,114(3):359-363
A series of ether-esters containing multidentate components have been prepared from phenoxyacetic acid. The ligands were synthesized from the appropriate phenoxyacetic acid chloride and various alcohols. Four types of new compounds have been obtained. 相似文献
989.
Khalil A. Mahmoud Antony J. Rest Helmut G. Alt 《Journal of organometallic chemistry》1983,246(2):c37-c41
Infrared spectroscopic evidence including 13CO labelling and energy-factored force-field fitting is presented for the first time to show that the radicals (η5-C5H5)-M(CO)3? (M = MO, W) and HCO are produced on photolysis of (η5-C5H5)M(CO)3H complexes in CO matrices at 12 K. 相似文献
990.
Preparation of a potentiometric immobilized urease electrode and urea determination in serum 总被引:2,自引:0,他引:2
Polyvinylalcohol was activated with 2-fluoro-1-methylpyridiniumtoluene-4-sulphonate and urease (EC.3.5.1.5) was covalently linked to the activated matrix. PVA-urease was then immobilized on the surface of a pH glass electrode with gelatine gel and it was cross-linked using glutaraldehyde. This potentiometric membrane electrode provides a linearity to urea in the 8.910−5 to 1.110−3 M concentration range, but by changing the buffer concentration can be studied in the range of 10−4 to 10−2 M urea concentration. Reproducibility experiments (n:20) were carried out with the urease enzyme electrode and with photometric methods for pooled serum sample. Average values for the two methods were 5.96 and 5.86 mM, variation coefficients were 2.5 and 3.5% respectively. 相似文献