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61.
Biology‐Oriented Synthesis of a Withanolide‐Inspired Compound Collection Reveals Novel Modulators of Hedgehog Signaling 下载免费PDF全文
Dr. Jakub Švenda Dipl.‐Biochem. Michael Sheremet M. Sc. Lea Kremer Lukáš Maier Dr. Jonathan O. Bauer Prof. Dr. Carsten Strohmann Dr. Slava Ziegler Dr. Kamal Kumar Prof. Dr. Herbert Waldmann 《Angewandte Chemie (International ed. in English)》2015,54(19):5596-5602
Biology‐oriented synthesis employs the structural information encoded in complex natural products to guide the synthesis of compound collections enriched in bioactivity. The trans‐hydrindane dehydro‐δ‐lactone motif defines the characteristic scaffold of the steroid‐like withanolides, a plant‐derived natural product class with a diverse pattern of bioactivity. A withanolide‐inspired compound collection was synthesized by making use of three key intermediates that contain this characteristic framework derivatized with different reactive functional groups. Biological evaluation of the compound collection in cell‐based assays that monitored biological signal‐transduction processes revealed a novel class of Hedgehog signaling inhibitors that target the protein Smoothened. 相似文献
62.
Doping of Zinc Oxide with Selected First Row Transition Metals for Photocatalytic Applications 下载免费PDF全文
ZnO doped with Cr, Mn, Fe, Co, Ni and Cu was prepared by homogeneous hydrolysis of sulfates with urea. The samples were annealed at various temperatures and characterized by X‐ray powder diffraction, UV/VIS reflectance spectroscopy, BET (Brunauer‐Emmet‐Teller) surface area and porosity measurements. The photocatalytic activity of the samples was evaluated by measuring the degradation of an organic dye Reactive Black 5. The morphology of the samples was determined by scanning electron microscopy and atomic force microscopy. For the Cu‐doped ZnO sample, EPR spectra were obtained. All samples annealed at 800°C contained hexagonal ZnO. In the VIS region, the best photocatalytic performance had the ZnO samples doped with Cr, Fe and Cu. 相似文献
63.
64.
Luís F. Guido Daniel O. Carvalho Jakub Taborsky Jana Skopalova Helena M. E. B. Saldanha Petr Bednar 《Chromatographia》2015,78(19-20):1233-1243
65.
Consider a simple graph and its proper edge coloring c with the elements of the set . We say that c is neighbor set distinguishing (or adjacent strong) if for every edge , the set of colors incident with u is distinct from the set of colors incident with v. Let us then consider a stronger requirement and suppose we wish to distinguishing adjacent vertices by sums of their incident colors. In both problems the challenging conjectures presume that such colorings exist for any graph G containing no isolated edges if only . We prove that in both problems is sufficient. The proof is based on the Combinatorial Nullstellensatz, applied in the “sum environment.” In fact the identical bound also holds if we use any set of k real numbers instead of as edge colors, and the same is true in list versions of the both concepts. In particular, we therefore obtain that lists of length ( in fact) are sufficient for planar graphs. 相似文献
66.
Adamczyk Z Barbasz J Cieśla M 《Langmuir : the ACS journal of surfaces and colloids》2011,27(11):6868-6878
Adsorption of fibrinogen, modeled as a linear chain of touching beads of various sizes, was theoretically studied using the random sequential adsorption (RSA) model. The adsorption process was assumed to consist of two steps: (i) formation of an irreversibly bound fibrinogen monolayer under the side-on orientation, which is independent of the bulk protein concentration and (ii) formation of the reversibly bound, end-on monolayer, whose coverage was dependent on the bulk concentration. Calculation based on the RSA model showed that the maximum surface concentration of the end-on (reversible) monolayer equals N(⊥∞) = 6.13 × 10(3) μm(-2) which is much larger than the previously found value for the side-on (irreversible) monolayer, equal to N(∞) = 2.27 × 10(3) μm(-2). Hence, the maximum surface concentration of fibrinogen in both orientations is determined to be 8.40 × 10(3) μm(-2) corresponding to the protein coverage of 5.70 mg m(-2) assuming 20% hydration. Additionally, the surface blocking function (ASF) was determined for the end-on fibrinogen adsorption, approximated for the entire range of coverage by the interpolating polynomial. For the coverage approaching the jamming limit, the surface blocking function (ASF) was shown to vanish proportionally to (θ(⊥∞) - θ(⊥))(2). These calculation allowed one to theoretically predict adsorption isotherms for the end-on regime of fibrinogen and adsorption kinetics under various transport conditions (diffusion and convection). Using these theoretical results, a quantitative interpretation of experimental data obtained by TIRF and ellipsometry was successfully performed. The equilibrium adsorption constant for the end-on adsorption regime was found to be 8.04 × 10(-3) m. On the basis of this value, the depth of the adsorption energy minimum, equal to -17.4 kT, was predicted, which corresponds to ΔG = -41.8 kJ mol(-1). This is in accordance with adsorption energy derived as the sum of the van der Waals and electrostatic interactions. Besides having significance for predicting fibrinogen adsorption, theoretical results derived in this work also have implications for basic science providing information on mechanisms of anisotropic protein molecule adsorption on heterogeneous surfaces. 相似文献
67.
Acyclic monounary algebras are characterized by the property that any compatible partial order r can be extended to a compatible linear order. In the case of rooted monounary algebras A=(A,f){\cal A}=(A,f) we characterize the intersection of compatible linear extensions of r by several equivalent conditions and generalize these results to compatible quasiorders of A{\cal A}. We show that the lattice QuordA{\rm{Quord}}{\cal A} of compatible quasiorders is a disjoint union of semi-intervals whose maximal elements equal the intersection of their compatible
quasilinear extensions. We also investigate algebraic properties of the lattices QuordA{\rm{Quord}}{\cal A} and ConA{\rm{Con}}{\cal A}. 相似文献
68.
For any integer r > 1, an r-trestle of a graph G is a 2-connected spanning subgraph F with maximum degree Δ(F) ≤ r. A graph G is called K
1,r
-free if G has no K
1,r
as an induced subgraph. Inspired by the work of Ryjáček and Tkáč, we show that every 2-connected K
1,r
-free graph has an r-trestle. The paper concludes with a corollary of this result for the existence of k-walks. 相似文献
69.
Jirkovský JS Panas I Ahlberg E Halasa M Romani S Schiffrin DJ 《Journal of the American Chemical Society》2011,133(48):19432-19441
A novel strategy to direct the oxygen reduction reaction to preferentially produce H(2)O(2) is formulated and evaluated. The approach combines the inertness of Au nanoparticles toward oxidation, with the improved O(2) sticking probability of isolated transition metal "guest" atoms embedded in the Au "host". DFT modeling was employed to screen for the best alloy candidates. Modeling indicates that isolated alloying atoms of Pd, Pt, or Rh placed within the Au surface should enhance the H(2)O(2) production relative to pure Au. Consequently, Au(1-x)Pd(x) nanoalloys with variable Pd content supported on Vulcan XC-72 were prepared to investigate the predicted selectivity toward H(2)O(2) production for Au alloyed with Pd. It is demonstrated that increasing the Pd concentration to 8% leads to an increase of the electrocatalytic H(2)O(2) production selectivity up to nearly 95%, when the nanoparticles are placed in an environment compatible with that of a proton exchange membrane. Further increase of Pd content leads to a drop in H(2)O(2) selectivity, to below 10% for x = 0.5. It is proposed that the enhancement in H(2)O(2) selectivity is caused by the presence of individual surface Pd atoms surrounded by gold, whereas surface ensembles of contiguous Pd atoms support H(2)O formation. The results are discussed in the context of exergonic electrocatalytic H(2)O(2) synthesis in Polymer Electrolyte Fuel Cells for the simultaneous cogeneration of chemicals and electricity, the latter a credit to production costs. 相似文献
70.
Multistep phosphorelay (MSP) pathways mediate a wide spectrum of adaptive responses in plants, including hormonal and abiotic stress regulations. Recent genetic evidence suggests both partial redundancy and possible functional cross-talk on the one hand and a certain level of specificity on the other. Here, we discuss recent achievements improving our understanding of possible molecular mechanisms of specificity in MSP. We consider a certain evolutionary conservation of ancestral two-component signalling systems from bacteria in a process of molecular recognition that, as we have recently shown, could be applied also to a certain extent in the case of plant MSP. Furthermore, we discuss possible roles of kinase and phosphatase activities, kinetics of both these enzymatic reactions, and phosphorylation lifetime. We include also recent findings on the expression specificity of individual members of MSP pathways and, finally, based on our recent findings, we speculate about a possible role of magnesium in regulation of MSP pathways in plants. All these mechanisms could significantly influence specificity and signalling output of the MSP pathways. 相似文献