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991.
Protein adsorption on PDMS surfaces poses a significant challenge in microfluidic devices that come into contact with biofluids such as blood. Polyurethane (PU) is often used for the construction of medical devices, but despite having several attractive properties for biointerfacing, it has not been widely used in microfluidic devices. In this work we developed two new fabrication processes for making thin, transparent and flexible PU-based microfluidic devices. Methods for the fabrication and bonding of microchannels, the integration of fluidic interconnections and surface modification with hydrophilic polyethylene oxide (PEO) to reduce protein adsorption are detailed. Using these processes, microchannels were produced having high transparency (96% that of glass in visible light), high bond strength (326.4 kPa) and low protein adsorption (80% reduction in fibrinogen adsorption vs. unmodified PDMS), which is critical for prevention of fouling. Our findings indicate that PEO modified PU could serve as an effective alternative to PDMS in blood contacting microfluidic applications. 相似文献
992.
S Koch RK Joshi M Noyong J Timper JJ Schneider U Simon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(37):11614-11620
The formation of stochastically oriented carbon-nanotube networks on top of an array of free-standing chromium-capped silicon nanopillars is reported. The combination of nanosphere lithography and chemical vapor deposition enables the construction of nanostructures that exhibit a hierarchical sequence of structural sizes. Metallic chromium serves as an etching mask for Si-pillar formation and as a nucleation site for the formation of carbon nanotubes through the chemical vapor deposition of ethene, ethanol, and methane, respectively, thereby bridging individual pillars from top to top. Iron and cobalt were applied onto the chromium caps as catalysts for CNT growth and the influence of different carbon sources and different gas-flow rates were investigated. The carbon nanotubes were structurally characterized and their DC electrical properties were studied by in situ local- and ex situ macroscopic measurements, both of which reveal their semiconductor properties. This process demonstrates how carbon nanotubes can be integrated into Si-based semiconductors and, thus, this process may be used to form high-surface-area sensors or new porous catalyst supports with enhanced gas-permeation properties. 相似文献
993.
We report the synthesis and characterization of a tamoxifen-tethered single-walled carbon nanotube (SWCNT) conjugate, in which tamoxifen is covalently attached to the single-walled carbon nanotube via oxidation and esterification reactions for the first time. The functionalized SWCNT derivative was characterized by using spectroscopic techniques: IR, UV-vis, Raman, and (1)H NMR Spectroscopy. The attachment of the drug tamoxifen to SWCNTs is analogous to the gold conjugate, which provided an endocrine treatment for breast cancer. 相似文献
994.
Mukherjee B Peterson A Subramanian VR 《Chemical communications (Cambridge, England)》2012,48(18):2415-2417
Heterostructured CdS nanowires with PbS deposits forming p-n junctions have been synthesized by successive cation exchange. The method developed herein opens up the possibility of preparing a spatially distributed heterojunction-based multifunctional electrode. The (photo)electrochemical activity of the material may be chemically tuned by changing the size and density of the p type PbS nanoparticles. 相似文献
995.
Tetrahydropyranyl (THP) ethers have been efficiently and simply deprotected by using Silica supported sodium hydrogen sulphate (NaHSO4‐SiO2) in methanol at room temperature to regenerate the parent alcohols in high yields. 相似文献
996.
Lalithambigai K Suresh P Ravi V Prabakaran K Jaroszewicz Z Rajesh KB Anbarasan PM Pillai TV 《Optics letters》2012,37(6):999-1001
We investigate the focusing properties of a double-ring-shaped azimuthally polarized beam by a high numerical aperture (NA) lens axicon based on vector diffraction theory. We observe that our proposed system generates a sub wavelength focal hole of 0.5λ having large uniform focal depth of 48λ without any annular aperture. We also observed that the distribution of the total intensity near the focus has little variation with the degree of truncation β of the incident beam by the pupil. The authors expect such a super-long dark channel may find applications in optical, biological, and atmospheric sciences. 相似文献
997.
Ravi Montenegro 《Random Structures and Algorithms》2009,34(3):395-407
We bound total variation and L∞ mixing times, spectral gap and magnitudes of the complex valued eigenvalues of general (nonreversible nonlazy) Markov chains with a minor expansion property. The resulting bounds for the (nonlazy) simple and max‐degree walks on a (directed) graph are of the optimal order. It follows that, within a factor of two or four, the worst case of each of these mixing time and eigenvalue quantities is a walk on a cycle with clockwise drift. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009 相似文献
998.
Ravi Chitikireddy Subhendu K. Datta Arvind H. Shah Hao Bai 《International Journal of Solids and Structures》2011,48(21):3063-3074
This paper presents a theoretical study of transient ultrasonic guided waves generated by concentrated heating of the outer surface of an infinite anisotropic hollow circular cylinder. Generalized thermoelastic theory proposed by Lord and Shulman is adopted to model the dynamic thermoelastic behavior of the cylinder. The concentrated heat source model used is to represent heating due to a pulsed laser beam, which is focused on the outer surface of the cylinder. A semi-analytical finite element (SAFE) method is employed to evaluate guided wave modes in the cylinder. Using integral transform techniques, the modal wave forms are obtained in frequency and wave number domains. Time histories of the propagating modes are then calculated by applying inverse Fourier transformation in the time domain. Numerical results showing the dispersion curves for the group velocities of the propagating modes and transient radial displacements are presented. For this purpose it is assumed that the cylinder is made of transversely isotropic silicon nitride (Si3N4). Attention is focused on the propagation characteristics of longitudinal and flexural modes separately. 相似文献
999.
de Silva ED Williams DE Jayanetti DR Centko RM Patrick BO Wijesundera RL Andersen RJ 《Organic letters》2011,13(5):1174-1177
Dhilirolides A (1) to D (4), a family of secondary metabolites with a putative meroterpenoid biogenetic origin and the unprecedented dhilirane and isodhilirane carbon skeletons, have been isolated from laboratory cultures of the fruit-infecting fungus Penicillium purpurogenum collected in Sri Lanka. The structures of 1 to 4 were elucidated by interpretation of NMR data and a single crystal X-ray diffraction analysis of 1. 相似文献
1000.
We carried out the structural, morphological and transport study of PrFe0.5Ni0.5O3 thin films prepared by pulsed laser deposition (PLD) over various substrates. Different substrates like LaAlO3 (001),GaAs(001) and Si(001) were used for deposition to understand effect of lattice mismatch on various physical properties. The film deposited on LaAlO3 was of best quality with well (001)-oriented and having good crystalline properties. Whereas, film deposited on GaAs(001) is well textured. Both films shows semiconducting behavior and resistance of the film deposited on GaAs(001) shows larger than that of film deposited on LAO. However, film deposited on Si, also shows polycrystalline growth with unusual metallic behavior. We tried to correlate this behavior with strain-induced growth of these films. Other possibilities for this unusual trend is also explored. 相似文献