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991.
Jerzy T. Wróbel Agnieszka Iwanow Krystyna Wojtasiewicz Halszka Bielawska Barbara Bobeszko 《Phosphorus, sulfur, and silicon and the related elements》2013,188(1-2)
Abstract Further studies on basic compounds from Nuphar luteum L. Sm. resulted in isolation of a new group of sulfoxides with thiohemiaminal type of structure. 相似文献
992.
During a study of a general synthesis of α-methylenecarbonyl compounds,1 we investigated the Mannich reaction of 2-carbomethoxycyclohexanone with formaldehyde and various secondary amines. The unexpected formation of 6-methylene-2-carbomethoxycyclohexanone, existing mainly in the enol form, as the only isolable product is the subject of this report. 相似文献
993.
994.
995.
Roberto Centore Antonio Roviello Angela Tuzi Barbara Panunzi 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(1):m26-m28
The title compounds, {5‐(dimethylamino)‐2‐[N‐(4‐methoxyphenyl)iminomethyl]phenyl}[N‐(4‐methoxyphenyl)‐4‐nitrosalicylaldiminato]palladium(II), [Pd(C14H11N2O4)(C16H17N2O)], (I), and [4‐(diethylamino)‐N‐(4‐methoxyphenyl)salicylaldiminato]{2‐[N‐(4‐methoxyphenyl)iminomethyl]‐5‐nitrophenyl}palladium(II) dichloromethane hemisolvate, [Pd(C14H11N2O3)(C18H21N2O2)]·0.5CH2Cl2, (II), both contain push–pull chromophores coordinated to Pd in a square‐planar arrangement. In both compounds, the five‐membered orthopalladated ring is essentially planar, while the coordinated six‐membered ring is not. Deviations from a coplanar arrangement of the phenylene rings of the coordinated Schiff bases are observed in both (I) and (II) as a result of intramolecular steric interactions. 相似文献
996.
997.
Barbieri CM Li TK Guo S Wang G Shallop AJ Pan W Yang G Gaffney BL Jones RA Pilch DS 《Journal of the American Chemical Society》2003,125(21):6469-6477
Spectroscopic and calorimetric techniques were employed to characterize and contrast the binding of the aminoglycoside paromomycin to three octamer nucleic acid duplexes of identical sequence but different strand composition (a DNA.RNA hybrid duplex and the corresponding DNA.DNA and RNA.RNA duplexes). In addition, the impact of paromomycin binding on both RNase H- and RNase A-mediated cleavage of the RNA strand in the DNA.RNA duplex was also determined. Our results reveal the following significant features: (i) Paromomycin binding enhances the thermal stabilities of the RNA.RNA and DNA.RNA duplexes to similar extents, with this thermal enhancement being substantially greater in magnitude than that of the DNA.DNA duplex. (ii) Paromomycin binding to the DNA.RNA hybrid duplex induces CD changes consistent with a shift from an A-like to a more canonical A-conformation. (iii) Paromomycin binding to all three octamer duplexes is linked to the uptake of a similar number of protons, with the magnitude of this number being dependent on pH. (iv) The affinity of paromomycin for the three host duplexes follows the hierarchy, RNA.RNA > DNA.RNA > DNA.DNA. (v) The observed affinity of paromomycin for the RNA.RNA and DNA.RNA duplexes decreases with increasing pH. (vi) The binding of paromomycin to the DNA.RNA hybrid duplex inhibits both RNase H- and RNase A-mediated cleavage of the RNA strand. We discuss the implications of our combined results with regard to the specific targeting of DNA.RNA hybrid duplex domains and potential antiretroviral applications. 相似文献
998.
Morzyk-Ociepa B Michalska D 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2003,59(6):1247-1254
The FT-Raman and FT-infrared spectra of (1-methyluracilato)silver, [Ag(C(5)H(5)N(2)O(2))] in the solid state have been studied. The complex is a polymer in which one silver ion is linearly bonded to two 1-MeU ligands through the deprotonated N(3) sites and another silver ion is tetrahedrally coordinated to the four 1-MeU ligands through the O2 and O4 carbonyl oxygen atoms. The harmonic vibrational frequencies, infrared intensities and Raman scattering activities of the N(3)-deprotonated 1-methyluracilate anion have been calculated using density functional (B3LYP) and ab initio (HF and MP2) methods with the 6-31G(d,p) and 6-31++G(df,pd) basis sets. The calculated potential energy distribution (PED) for the 1-MeU anion has proved to be of great help in assigning the spectra of the title complex. It can be concluded that the two strong Raman bands at 1263 and 796 cm(-1) are diagnostic for the N3-deprotonation of the 1-methyluracilate ring and complexation with silver ion. The linear N-Ag-N stretching vibrations are assigned to the bands at 448 and 362 cm(-1) (IR) and 453, 362 cm(-1) (Raman). The Ag-O stretching vibrations are assigned to the bands in the range of 280-250 cm(-1). 相似文献
999.
The field of proteomics requires methods that offer high sensitivity and wide dynamic range. One of the strategies used to improve the dynamic range is sample prefractionation, such as microsolution isoelectric focusing (IEF). We have modified a commercial solution IEF instrument, the Rotofor, to prefractionate protein mixtures by carrier ampholyte-free solution IEF. The focusing chamber of the Rotofor was divided into several compartments by polyacrylamide membranes with imbedded Immobiline mixtures of specific pH values. When an electric field is applied, each protein migrates to the compartment confined by membranes with pH values flanking its isoelectric point. The approach was demonstrated for the focusing of myoglobin into a predicted compartment, as well as the separation of a complex soluble yeast protein mixture into several distinct fractions. The proteins were dissolved in water or 30% isopropanol. The method is applicable to both gel-based and solution-phase protein identification methods, without the need for further sample preparation. 相似文献
1000.
Paulson EK Morcombe CR Gaponenko V Dancheck B Byrd RA Zilm KW 《Journal of the American Chemical Society》2003,125(47):14222-14223
A highly sensitive new 1H-detected 3D solid-state NMR method is described for characterizing 1H-1H spin exchange in nanocrystalline samples of 15N- and 2H-enriched protein. Long-range contacts are observed in human ubiquitin. The method is also used to show that numerous NOEs between backbone amides and crystal water protons can be observed. 相似文献