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991.
A new concept for the amplified electrochemical detection of the 7229-base viral DNA of M13phi is developed. A thiolated 27-base nucleic acid (1) is assembled on an Au-electrode. Hybridization between the sensing interface and the M13phi DNA is followed by the polymerase-induced replication of the analyte DNA in the presence of dCTP, dGTP, dATP, and ferrocene-tethered-dUTP (2). The generated redox-active replica mediates electron transfer between the enzyme glucose oxidase (GOx) and the electrode and activates the bioelectrocatalyzed oxidation of glucose. The bioelectrocatalyzed oxidation of glucose provides a biocatalytic amplification path for the formation of the redox-active replica. The electrochemical techniques to follow the replication and the bioelectrocatalytic amplification are differential pulse voltammetry and cyclic voltammetry. The electrical responses from the system relate to the bulk concentration of the M13phi DNA, thus enabling the quantitative analysis of the viral gene. 相似文献
992.
Raitman OA Patolsky F Katz E Willner I 《Chemical communications (Cambridge, England)》2002,(17):1936-1937
A novel method to generate an integrated electrically contacted glucose dehydrogenase electrode by the surface reconstitution of the apo-enzyme on a pyrroloquinoline quinone (PQQ)-modified polyaniline is described. In situ electrochemical surface plasmon resonance (SPR) is used to characterize the bioelectrocatalytic functions of the system. 相似文献
993.
Fernando Sartillo-Piscil Silvano CruzMario Sánchez Herbert HöpflCecilia Anaya de Parrodi Leticia Quintero 《Tetrahedron》2003,59(23):4077-4083
Twelve 2-phenoxy-2-oxo-1,3,2-dioxaphosphorinanes fused with a 1,2-O-isopropylidene-α-d-xylofuranose moiety in cis orientation and substituted at the C′5 position were prepared in two steps from commercially available diacetone-α-d-glucose. Their conformations, and configurations were determined by 1H and 31P NMR and X-ray crystallographic techniques. Both, chair-twisted-chair and chair-boat equilibria were observed in solution. We observed that the strong anisotropic shielding effect of the benzene ring in the phenoxy group generates an upfield shift of the H1 hydrogen atom, when the cyclic phosphates adopt a boat conformation. This is due to a relative cis-orientation of the P-phenoxy group and the H1 proton of the 1,2-O-isopropylidene-α-d-xylofuranose moiety. Therefore, the configuration of the phosphorus center (SP or RP) can be determined by 1H NMR spectroscopy. Interestingly, the crystal structure of one of the cyclic phosphates exhibits two independent molecules in the asymmetric unit, one with a chair and the other one with a boat conformation. 相似文献
994.
Beatriz Fernandez-Band Fernando Lázaro M.D. Luque de Castro Miguel Valcarcel 《Analytica chimica acta》1990
A method for the determination of 2,4-dinitrophenylhydrazine and 2- and 4-nitrophenylhydrazine in mixtures based on their different spectral features is proposed. The sample containing the amines is injected into an FIA manifold and passed through the flow cell of a diode-array spectrophotometer where a support (C18 bonded silica) retains the analytes. The amines are concentrated in situ, thereby achieving a determination limit of 5 × 10?7 M. The carrier (phosphate buffer-methanol) rapidly elutes the retained compounds, so a sampling frequency of 40 h?1 could be obtained. The resolution of mixtures of these amines can be carried out with acceptable low errors. 相似文献
995.
996.
[reaction: see text] 5'-Peptide oligonucleotide conjugates were prepared stepwise on a single support using N(alpha)-Fmoc-protected amino acids and unprotected phosphate groups. The method uses commercially available reagents and is successful with most natural amino acids. The simplicity of the method may encourage researchers to prepare new oligonucleotide-peptide conjugates with novel properties. 相似文献
997.
Cembran A Bernardi F Olivucci M Garavelli M 《Journal of the American Chemical Society》2003,125(41):12509-12519
In this paper we use ab initio multireference M?ller-Plesset second-order perturbation theory computations to map the first five singlet states (S(0), S(1), S(2), S(3), and S(4)) along the initial part of the photoisomerization coordinate for the isolated rhodopsin chromophore model 4-cis-gamma-methylnona-2,4,6,8-tetraeniminium cation. We show that this information not only provides an explanation for the spectral features associated to the chromophore in solution but also, subject to a tentative hypothesis on the effect of the protein cavity, may be employed to explain/assign the ultrafast near-IR excited-state absorption, stimulated emission, and transient excited-state absorption bands observed in rhodopsin proteins (e.g. rhodopsin and bacteriorhodopsin). We also show that the results of vibrational frequency computations reveal a general structure for the first (S(1)) excited-state energy surface of PSBs that is consistent with the existence of the coherent oscillatory motions observed both in solution and in bacteriorhodopsin. 相似文献
998.
Analytical methods based on secondary ion mass spectrometry were developed for the characterisation of a complex layered silicate REE-mineral, named sazhinite, for which a number of issues are still open regarding its chemistry and structure. Such procedures involved the analysis and quantification of light, volatile, alkaline, medium-Z, rare earth and actinide elements. The accuracy of the SIMS data is within the assigned precision of the concentration values assumed as reference in the calibration standards employed. REE and actinide data yield a good agreement in terms of calculated site scattering at the M site: 58.42 electrons per formula unit (epfu) vs. 60.39epfu obtained by Single Crystal Structure-Refinement (SREF). Accuracy is estimated on the order of 5% rel. for H, Li, Be and B, and 10% rel. for F. Na analysis was crucial to solve the open questions about the structure, and excellent agreement was obtained by comparing data from SIMS (REE, Y, actinides, Na)+EMPA (SiO2, CaO, SO3 and K2O) with information derived from SREF: site scattering of the M site+Na sites=92.56epfu calculated from chemical data, against 91.95epfu from SREF. Such procedures can be easily extended to the analysis of variously complex, silicate REE-minerals. 相似文献
999.
The mass spectrometric study of 2,4-dinitrophenyl 2′-R-phenyl ethers (R ? H, Me, Et, i-Pr, tert-Bu) showed that (1) fragmentation proceeds differently from unsubstituted and 4-nitro-substituted diphenyl ethers; (2) important fragmentation routes involve interannular migrations and cyclizations; (3) these occur between two groups ortho to the ether linkage while the ethers are in unfavorable endo, endo twist conformations; (4) the observed interannular interactions can be ustified by the existence in these compounds of an intramolecular π-complex which stabilizes the sterically unfavorable conformation and explains the observed fragmentations. 相似文献
1000.
A laser-induced fluorescence method has been used to study the vibrational relaxation of NO by atomic oxygen, i.e. NO(v=1) + O — NO(v=0) + O(2). The NO was excited indirectly by vibrational-vibrational energy transfer from HCI(v=1), these molecules having been prepared using the output from a pulsed HCl chemical laser. The experiments yield: k2=(6.5 ± 0.7) × 10?11 cm3 molecule?1 s?1 at (296 ± 3) K. 相似文献