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991.
992.
During the first formation stage of the negative plate in H2SO4 solution lead monoxide and tribasic sulphate transform into Pb and PbSO4 giving rise to a Pb?PbSO4 zone. It was established that these processes take place within a thin layer (the δ-layer) situated between the Pb?PbSO4 zone and the paste. The rate determining step is the transport (by diffusion and migration) of H+ and SO42? ions from the bulk of the electrolyte towards the δ-layer. An equation is derived for the dependence of the concentration of the H2SO4 in the Pb?PbSO4 zone on the thickness of this zone. It was found that during formation until a limiting thickness of the Pb?PbSO4 zone, PbSO4 originates mainly at the expense of the H2SO4 present in the bulk of the electrolyte. When the formation rate of PbSO4 becomes very small the reaction of PbSO4 reduction to Pb takes place. This reaction proceeds in a second reaction layer (the α-layer) which is located in the Pb?PbSO4 zone at the plate surface. Subsequently, the formation of PbSO4 in the δ-layer takes place at the expense of H2SO4 generated in the α-layer. The model is confirmed by the experimentally determined distribution of PbSO4 across the cross-section of the plate during formation.  相似文献   
993.
CBD is a promising candidate for treatment of many diseases and plays a major role in the growing trend to produce high-end drugs from natural, renewable resources. In the present work, we demonstrate a way to incorporate the anti-inflammatory drug CBD into smart microgel particles. The copolymer microgels that we chose as carrier systems exhibit a volume phase transition temperature of 39 C, which is just above normal body temperature and makes them ideal candidates for hyperthermia treatment. While a simple loading route of CBD was not successful due to the enormous hydrophobicity of CBD, an alternative route was developed by immersing the microgels in ethanol. Despite the expected loss of thermoresponsive behaviour of the microgel matrix due to the solvent exchange, a temperature-dependent release of CBD was detected by the material, creating an interesting question of interactions between CBD and the microgel particles in ethanol. Furthermore, the method developed for loading of the microgel particles with CBD in ethanol was further improved by a subsequent transfer of the loaded particles into water, which proves to be an even more promising approach due to the successful temperature-dependent release of the drug above the collapse temperature of the microgels.  相似文献   
994.
We describe an approach that utilizes nonlinear peptides to direct the assembly of previously reported Self-Assembling Fibers (SAFs). The SAF system comprises two complementary linear peptides, SAF-p1 and SAF-p2a, which combine to form exclusively linear, nonbranched fibers. The Matrix-Programming (MaP) peptides described herein are based on these peptides: they comprise two or three half-peptide blocks derived from the SAF peptides, which are conjugated via dendritic hubs. Different MaP peptides coassembled with the standard SAF peptides to form specific structures, such as hyperbranched networks, polygonal matrices, and regularly segmented and terminated fibers. The role of each half-peptide block in dictating the different features has been elucidated. This provides a strong basis for designing new peptide-based nanostructured materials from the bottom up.  相似文献   
995.
A possibility of a combination of supported liquid membrane (SLM) and solid-phase extraction (SPE) for the determination of atrazine at microgram level in different type of fruit juices is presented. In comparison to SPE extraction from juice samples, the application of SLM-SPE enrichment provides much cleaner extracts and the possibility of lowering the limit of detection as low as 30 microg/l. However, it was also shown that by appropriate manipulation of SLM extraction conditions mainly flow-rate of donor phase and volume ratio between donor and acceptor phase, the level of detection can be further decreased to 10 microg/l. The results suggest that the application of SLM extraction prior to SPE is an alternative method for atrazine enrichment from complicated liquid matrices and could be used as routine method for the clean-up of such samples.  相似文献   
996.
In liquid In0.83Te0.17 which exhibits demixing at Tc=835 K, we have measured the nuclear spin relaxation rate R of the isomeric probe 117msb by a TDPAD technique. Within an interval of 50 K, an increase of R by about 30% is observed as T Tc. This phenomenon is interpreted as indicating a marked increase of concentration fluctuations over small regions in r-space.Guest of Sfb 161We are obliged to Gesellschaft für Kernforschung Karlsruhe for machine time and technical assistance. This work is supported by Deutsche Forschungsgemeinschaft through Sonderforschungsbereich 161.  相似文献   
997.
Depending on the conditions, -hydrohexafluoroisobutyric anhydride, hexafluorodimethylketene, or hexafluoroisobutenylidene sulfate is formed in the sulfotrioxidation of -hydrohexafluoroisobutyric acid. The sulfotrioxidation of -hydrohexafluoroisobutyric anhydride similarly gives hexafluorodimethylketene or hexafluoroisobutenylidene sulfate.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 13–15, January, 1973.  相似文献   
998.
A combination of electron, synchrotron X-ray and neutron powder diffraction reveals a new orthorhombic structure type within the Sr-doped rare earth perovskite cobaltates Ln1−xSrxCoO3−δ (Ln=Y3+, Dy3+, Ho3+, Er3+, Tm3+and Yb3+). Electron diffraction shows a C-centred cell based on a 2√2ap×4ap×4√2ap superstructure of the basic perovskite unit. Not all of these very weak satellite reflections are evident in the synchrotron X-ray and neutron powder diffraction data and the average structure of each member of this series could only be refined based on Cmma symmetry and a 2√2ap×4ap×2√2ap cell. The nature of structural and magnetic ordering in these phases relies on both oxygen vacancy and cation distribution. A small range of solid solution exists where this orthorhombic structure type is observed, centred roughly around the compositions Ln0.2Sr0.8CoO3−δ. In the case of Yb3+ the pure orthorhombic phase was only observed for 0.850?x?0.875. Tetragonal (I4/mmm; 2ap×2ap×4ap) superstructures were observed for compositions having higher or lower Sr-doping levels, or for compounds with rare earth ions larger than Dy3+. These orthorhombic phases show mixed valence (3+/4+) cobalt oxidation states between 3.2+ and 3.3+. DC magnetic susceptibility measurements show an additional magnetic transition for these orthorhombic phases compared to the associated tetragonal compounds with critical temperatures > 330 K.  相似文献   
999.
Using 1H-NMR spectra of radical copolymers of methyl acrylate (M1) and 4-vinyl pyridine (M2), the terminal model of copolymerization has been tested. Reactivity ratios (r1 = 0.18 r2 = 1.77) were found. The probability of “coisotactic” alternating addition (σ = 0.98) has been obtained as the best fit of experimental methoxy signal fractions and the theoretical curves.  相似文献   
1000.
Anisotropies of rays emitted in the decay of167Lu,T 1/2=51·5 min, were measured. The167Lu was oriented by the hyperfine interaction when the lutetium activity was included in a gadolinium host which was cooled to 15 mK temperature. A top-loading3He4He dilution refrigerator capable of quickly cooling a short-lived sample was used. Multipole mixing ratios have been evaluated for many transitions. The spin assignments have been made for a number of levels in167Yb and their parities have been deduced. In particular, an unambiguous 11/2 assignment was made for the 571·5 keV level which was identified as the band head of the 11/2 [505] band observed by Lindblad. The rotational bands in167Yb are discussed.Dedicated to the 25th anniversary of the Joint Institute for Nuclear Research.  相似文献   
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