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991.
Jozef Saloň Viktor Milata Nadežda Prónayová Ján Leško 《Monatshefte für Chemie / Chemical Monthly》2000,131(3):293-299
Summary. Reaction of 5-aminoquinoxaline with alkoxymethylene derivatives affords the corresponding quinoxalinoaminoethylenes. These
undergo a thermal cyclization to yield angularly annelated 10H-pyrido[2,3-f]quinoxalines. The structures of all products were deduced from their IR, UV, mass, 1H, and 13C NMR spectra.
Received September 24, 1999. Accepted November 18, 1999 相似文献
992.
993.
994.
Kirill N. Bakeev Sergey A. Chugunov Tat'yana A. Larina William J. Macknight Alexander B. Zezin Viktor A. Kabanov 《Macromolecular Symposia》1996,106(1):19-30
A systematic study of complexation reactions of sulfonated polystyrene ionomers containing up to 5 molar percent of polar chain units with various oil-soluble surfactants is carried out in low-polarity organic solvents. Dipole-dipole attractions of the components lead to the formation of complexes characterized by limiting compositions and an unusual polymer-colloidal morphology of joint clusters and/or micelles. The limiting compositions (φ) for the complexes formed between ionomers and surfactant of the same charge (bis(2-ethylhexyl)sulfosuccinate sodium salt), or nonionic surfactants (primarily aliphatic amines) are equal to 15–30 surfactant molecules per one ionomer salt/acid group on average, with φ depending on the hydrophilic-lypophilic balance of the components, the initial aggregation state of surfactant and the nature of low-polarity solvent. Ionomersurfactant complexation is accompanied by disruption of self-contacts of ionomer salt/acid groups, leading to “unfastening” and expansion of the ionomer coils in dilute solution. The “driving force” of the ionomersurfactant complexation and the structure of the resultant complexes are discussed. 相似文献
995.
Viktor Kettmann Jan Svtlík 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(8):o419-o421
The reaction between 4‐(4‐methylphenyl)but‐3‐en‐2‐one and aminoguanidine produced an unexpected product of formula C12H15N3O, consisting of a carboxamide moiety joined to a substituted pyrazoline ring at one of the N atoms. The pyrazoline ring adopts a flat‐envelope conformation and the substituted phenyl ring is oriented almost perpendicular to the heterocycle. The carbonyl O atom has partial anionic character as a result of the transfer of π density from the two adjacent sp2 N atoms and is involved in an intermolecular hydrogen bond with the amide group. 相似文献
996.
Lidiya Z. Rogovina Viktor G. Vasilev Vladimir S. Papkov Olga I. Shchegolikhina Grigorii L. Slonimskii Alexandr A. Zhdanov 《Macromolecular Symposia》1995,93(1):135-142
An unusual effect of physical network formation during heating or at room temperature alter previous heating was found for originally liquid poly(dimethylcarbosiloxane) containing 0.5 – 2.5 mol% of side carboxyl groups by means of the measurement of its Theological properties. The reason for this behaviour is supposed to be the predominance of intramolecular hydrogen bonding of COOH groups in original polymer and the intra– to Intermolecular bonds rearrangement during heating. The alternative reason can be the microphase separation with domains of COOH groups. The reversibility of the network is confirmed by the decrease in the elasticity modulus, development of irreversible deformation on further heating and by break-up of Junctions on the addition of small amounts of polar liquids. 相似文献
997.
Viktor A. Tafeenko Rene Peschar Olga V. Kaukova Henk Schenk Leonid A. Aslanov 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(1):o62-o64
In the title compound, C8H12N+·C8HN4O2−, the anion and cation lie on a crystallographic mirror plane and form planar ribbons via N—H⋯O [N⋯O = 2.933 (4) Å, H⋯O = 2.01 Å and N—H⋯O = 170°] and N—H⋯N [N⋯N = 3.016 (5) Å, H⋯N = 2.15 Å and N—H⋯N = 169°] hydrogen bonds. The ribbons are further linked via weak C—H⋯O and C—H⋯N hydrogen bonds. In adjacent planes, anions lie opposite cations; π–π interactions (separation a/2 = 3.520 Å) exist between the anions and the cations, and stacks are formed, running along the a axis. The cations are disordered over two interpenetrating sites, with occupancies of 0.833 (5) and 0.167 (5). 相似文献
998.
Intermetallic compounds SrNi2Si and BaNi2Si were prepared by arc‐melting of stoichiometric mixture of the elements and subsequent annealing in welded niobium ampoules. Both compounds were investigated by X‐ray diffraction on powder as well as single crystal methods. The title compounds both crystallize in the BaNi2Ge structure type (space group Pmmn, Z = 2), a ternary ordered variant of TiCu3: a = 4.0296(9) Å, b = 6.5121(14) Å, c = 5.6839(21) Å, R1 = 0.040 for SrNi2Si and a = 4.0681(9) Å, b = 6.580(4) Å, c = 5.976(5) Å, R1 = 0.031 for BaNi2Si. The structure contains corrugated polyanionic [Ni2Si]2– layers, stacked according to the primitive sequence AA along the c axis. Six‐membered Ni rings adopt a boat conformation, silicon atoms are in the plane with nickel, and the alkaline earth cations sit between the layers. These two compounds extend the family AeNi2X (Ae = Ca, Sr, Ba; X = Si, Ge), where up to date CaNi2Si, SrNi2Ge, and BaNi2Ge are known. LMTO band structure calculations, including DOS, COHP, and ELF were performed to gain more insight into the electronic situation of SrNi2Si and BaNi2Si. 相似文献
999.
Elena N.Danilovtseva Stanislav N.Zelinskiy Viktor A.Pal'shin Gayathri Kandasamy Uma Maheswari Krishnan Vadim V.Annenkov 《高分子科学》2019,37(7):637-645
Polymeric amines are being studied intensively as components of systems for gene delivery in genetic engineering and gene therapy of genetic disorders, including cancer. Despite remarkable achievements in the field, polymeric amines, such as polyethyleneimine, show some disadvantages. Strong interaction between the amine-containing polymer and nucleic acid hampers the release of nucleic acid in the cell cytoplasm. Amine groups can interact with the cell membrane which results in cell death. These limitations of polymeric amines stimulated an investigation of new structures for gene delivery. Imidazole-containing polymers have attracted attention as lesser basic substances, while they are able to interact with polymeric acids. Further development of imidazole-based gene delivery agents requires knowledge about some fundamental aspects of interaction between nucleic acids, and polymeric imidazoles. In this work, we studied the complexation of poly(1-vinylimidazole) and oligomeric DNA. We found that the number of active sites capable of binding with negatively charged phosphate groups is comparable with the number of protonated imidazole units in the case of high molecular weight polymer. The increase in polymer charge by 1-bromopropane quaternizating 1%?5% imidazole units or by decreasing the pH to 6.5?7 considerably increased the ability of poly(1-vinylimidazole) to interact with oligonucleotides. The pH sensitivity of this interaction is interesting for cancer gene therapy because the tumours have a lowered intercellular pH (stable oligonucleotide complex) and a higher extracellular pH which can lead to complex dissociation. Minimal critical length for complexation of quaternized poly(1-vinylimidazole) and DNA is below eight units which corresponds to polymers with amine groups. Fluorescence-tagged poly(1-vinylimidazole) samples were obtained and their potential for monitoring the polymer and polymer-oligonucleotide complex internalization into living cells was demonstrated. 相似文献
1000.
Alexander P. Chetverikov Werner Ebeling Viktor D. Lakhno Alexey S. Shigaev Manuel G. Velarde 《The European Physical Journal B - Condensed Matter and Complex Systems》2016,89(4):101
It is shown that in DNA-like molecules containing added, excess charges, such as electrons and holes (cation-radicals), it is possible by highly energetic, local, mechanical excitation at definite places of the chain to control the creation of breathers/bubbles and hence to control the long-range transfer of charges moving along the chain in a definite given direction with no external electric field needed. 相似文献