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The mass spectra of 25 triphenylmethyl (trityl) substituted compounds have been recorded. The trityl cation m/e 243 appears as a peak of major intensity for all classes of compounds examined; these contained trityl-carbon, trityl-nitrogen, trityl-oxygen or trityl-sulfur bonds. Fragmentation of the non-trityl portion of the molecules produced simple ions whose origin was predictable or of low intensity. A mechanism for the decay of the trityl cation is presented which is based upon retention of the α-carbon. Supporting evidence was afforded by mass spectral analysis of (C6H5)313CH in which all fragments from the trityl cation appear to retain nearly all of the 13C. 相似文献
84.
Donald F. Mullica Dennis R. Dillin Darrell G. Watson Michael Angel J. Matt Farmer Jason A. Kautz 《Journal of chemical crystallography》1998,28(12):899-903
Crystallographic structural refinement of E-4-(N-methylanilino)-3-pentene-2-one (I) has been carried out by means of three-dimensional single-crystal X-ray diffractometry. The title compound crystallizes in space group C2 (No. 5,Z = 4). The lattice constants are a = 21.543(4), b = 6.433(1), c = 8.019(2) Å, and = 97.82(3)°. Characterizations include physical property determinations and spectrometric identifications employing IR, 1H and 13C NMR, and X-ray powder analyses. The molecules in the crystal lattice are held together by van der Waals forces. Selected bond distances and angles are presented and discussed as well as synthesis and peripheral studies. 相似文献
85.
Peter C. DeMuth Wilfredo F. Garcia‐Beltran Michelle Lim Ai‐Ling Paula T. Hammond Darrell J. Irvine 《Advanced functional materials》2013,23(2):161-172
Transcutaneous administration has the potential to improve therapeutics delivery, providing an approach that is safer and more convenient than traditional alternatives, while offering the opportunity for improved therapeutic efficacy through sustained/controlled drug release. To this end, a microneedle materials platform is demonstrated for rapid implantation of controlled‐release polymer depots into the cutaneous tissue. Arrays of microneedles composed of drug‐loaded poly(lactide‐co‐glycolide) (PLGA) microparticles or solid PLGA tips are prepared with a supporting and rapidly water‐soluble poly(acrylic acid) (PAA) matrix. Upon application of microneedle patches to the skin of mice, the microneedles perforate the stratum corneum and epidermis. Penetration of the outer skin layers is followed by rapid dissolution of the PAA binder on contact with the interstitial fluid of the epidermis, implanting the microparticles or solid polymer microneedles in the tissue, which are retained following patch removal. These polymer depots remain in the skin for weeks following application and sustain the release of encapsulated cargos for systemic delivery. To show the utility of this approach the ability of these composite microneedle arrays to deliver a subunit vaccine formulation is demonstrated. In comparison to traditional needle‐based vaccination, microneedle delivery gives improved cellular immunity and equivalent generation of serum antibodies, suggesting the potential of this approach for vaccine delivery. However, the flexibility of this system should allow for improved therapeutic delivery in a variety of diverse contexts. 相似文献
86.
Andrew J. Guenthner Sureeporn Khombhongse Wenxia Liu Pratyush Dayal Darrell H. Reneker Thein Kyu 《Macromolecular theory and simulations》2006,15(1):87-93
Summary: To mimic the emergence of gradient morphology in polymer nanofibers, a new theoretical approach has been developed in the context of Cahn‐Hilliard time evolution equation, alternatively known as time‐dependent Ginzburg‐Landau equation (Model B) involving concentration order parameter. The effects of solvent evaporation on the morphology evolution of the nanofibers have been demonstrated. The numerical simulation showed that the formation of skin layers is governed by the competition between solvent evaporation rate and mutual diffusion rate. That is to say the skin layers are formed in the nanotube whenever the rate of evaporation exceeds a critical value; otherwise, a solid fiber is formed. In hollow nanofibers, the layer can grow to a substantial fraction of the fiber diameter, allowing it to remain intact, albeit often in a collapsed form.
87.
Kline TR Iwata J Lammert PE Mallouk TE Sen A Velegol D 《The journal of physical chemistry. B》2006,110(48):24513-24521
We recently reported the convection and pattern formation of tracers caused by a catalytically generated electric field. The electric field arises due to the heterogeneous electrochemical reduction and oxidation of hydrogen peroxide (H2O2) on silver (Ag) and gold (Au), respectively.1 Here we describe an electrokinetic model, developed in conjunction with experiments, that explains the details of the convection and pattern formation phenomenon. The model also enables the measurement of reaction kinetic parameters that are otherwise difficult to obtain. This quantitative model serves as a platform for the modeling of other catalytic redox systems and systems with broken symmetries. 相似文献
88.
Proteomic profiling of human urine using multi-dimensional protein identification technology 总被引:2,自引:0,他引:2
Ru QC Katenhusen RA Zhu LA Silberman J Yang S Orchard TJ Brzeski H Liebman M Ellsworth DL 《Journal of chromatography. A》2006,1111(2):166-174
Human urine samples are ideal for proteomic profiling and have tremendous potential as sources of biomarkers. Multi-dimensional protein identification technology (MudPIT) is an effective approach to analyzing human urine or other fluids dominated by diverse metabolites. MudPIT analysis was used to identify 87 proteins in just 15 ml of human urine. A high throughput, reproducible, and sensitive technology, MudPIT may soon be used for more proteomic analyses of metabolites. 相似文献
89.
Darrell E.P. Hoy 《Experimental Techniques》1997,21(4):17-19
In this paper, some considerations regarding the use of color digital imaging systems in experimental mechanics applications have been discussed. Two examples in the areas of photoelastic fringe analysis and machining chip color classification were presented. The author feels that the increasing availability of affordable color imaging systems will allow the discovery of many interesting applications in the areas of experimental mechanics and engineering. 相似文献
90.
Bruce R. Bailey III K. Darrell Berlin Douglas R. Powell Dick Van der Helm 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):121-133
Abstract A series of N-alkyl-3-thia-7-azabicyclo[3.3.1]nonan-9-ones and derivatives have been prepared from the reaction of an appropriate 4-thianone, an aldehyde and an amine in a Mannich type condensation. Reduction of the ketones via Wolff-Kishner conditions produced bicyclic systems with the methylene bridging group. Addition of Grignard reagents to the ketones did yield the expected alcohols. Conformational analysis of the systems was performed via diagnosis of the 1H and 13C NMR spectra. A single crystal X-ray diffraction analysis of 2,2,4,4-tetramethyl-6,8-diphenyl-3-thia-7-azabicyclo[3.3.1]nonan-9-one was accomplished and revealed a boat conformer for the nitrogen-containing ring and a chair conformer for the sulfur-containing ring. The ketone crystallized in the triclinic space group P1 (Z=2) with a=6.216 (3), b=10.507 (5), c=15.335 (6) Å, α=86.64 (4), β=86.66 (4), and γ=98.51 (5)° [Vol=986.55 Å3]. 相似文献