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991.
992.
Herein we demonstrate the ability to pattern Ag nanoparticle films of arbitrary geometry inside sealed PDMS/TiO2/glass microfluidic devices. The technique can be employed with aqueous solutions at room temperature under mild conditions. A 6 nm TiO2 film is first deposited onto a planar Pyrex or silica substrate, which is subsequently bonded to a PDMS mold. UV light is then exposed through the device to reduce Ag+ from an aqueous solution to create a monolayer-thick film of Ag nanoparticles. We demonstrate that this on-chip deposition method can be exploited in a parallel fashion to synthesize nanoparticles of varying size by independently controlling the solution conditions in each microchannel in which the film is formed. The film morphology was checked by atomic force microscopy, and the results showed that the size of the nanoparticles was sensitive to solution pH. Additionally, we illustrate the ability to biofunctionalize these films with ligands for protein capture. The results indicated that this could be done with good discrimination between addressed locations and background. The technique appears to be quite general, and films of Pd, Cu, and Au could also be patterned. 相似文献
993.
Feldman AR Leung EK Bennet AJ Sen D 《Chembiochem : a European journal of chemical biology》2006,7(1):98-105
Much interest has focused on the mechanisms of the five naturally occurring self-cleaving ribozymes, which, in spite of catalyzing the same reaction, adopt divergent strategies. These ribozymes, with the exception of the recently described glmS ribozyme, do not absolutely require divalent metal ions for their catalytic chemistries in vitro. A mechanistic investigation of an in vitro-selected, RNA-cleaving DNA enzyme, the bipartite, which catalyzes the same chemistry as the five natural self-cleaving ribozymes, found a mechanism of significant complexity. The DNAzyme showed a bell-shaped pH profile. A dissection of metal usage indicated the involvement of two catalytically relevant magnesium ions for optimal activity. The DNAzyme was able to utilize manganese(II) as well as magnesium; however, with manganese it appeared to function complexed to either one or two of those cations. Titration with hexaamminecobalt(III) chloride inhibited the activity of the bipartite; this suggests that it is a metalloenzyme that utilizes metal hydroxide as a general base for activation of its nucleophile. Overall, the bipartite DNAzyme appeared to be kinetically distinct not only from the self-cleaving ribozymes but also from other in vitro-selected, RNA-cleaving deoxyribozymes, such as the 8-17, 10-23, and 614. 相似文献
994.
Modeling iron binding to organic matter 总被引:1,自引:0,他引:1
The aim of the present work is to model iron speciation during its interaction with natural organic matter. Experimental data for iron speciation were achieved with an insolubilised humic acid used as an organic matter analogue for 30microM to 1.8 mM total iron concentrations and 2< or = pH< or = 5.5. IHA was found to be able to impose its redox potential to the solution and therefore the Fe(ll)/Fe(lll) ratio. Model VI and the NICA-Donnan model have been adjusted to experimental results of acid-base titrations, total iron measurements, and redox speciation in solution. They both describe well pH and concentration dependence of iron adsorption. For high iron concentration, Fe(lll) solution activity is limited by precipitation of a poorly ordered Fe oxyhydroxide with a higher solubility (log Ks = 5.6-5.7) than ferryhydrite described in the litterature. 相似文献
995.
Kostsov EG 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(12):2294-2298
The design of the capacitive motors that are based on the electrostatic rolling of the thin metallic film on the ferroelectric surface is studied. It is shown that this method of energy conversion allows one to move the main stage of electromechanical energy conversion into the nanometer range when using the materials with high dielectric permeability (more than 500). The analysis of the distribution of the forces and field in the nanometer gap of the electrostatic micromotors is carried out. An experimental investigation of these micromotors is performed. 相似文献
996.
Fronheiser MP Light ED Idriss SF Wolf PD Smith SW 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(1):100-105
Modifications were made to a commercial real-time, three-dimensional (3-D) ultrasound system for near simultaneous 3-D scanning with two matrix array transducers. As a first illustration, a transducer cable assembly was modified to incorporate two independent, 3-D intra-cardiac echo catheters, a 7 Fr (2.3 mm O.D.) side scanning catheter and a 14 Fr (4.7 mm O.D) forward viewing catheter with accessory port, each catheter using 85 channels operating at 5 MHz. For applications in treatment of atrial fibrillation, the goal is to place the sideviewing catheter within the coronary sinus to view the whole left atrium, including a pulmonary vein. Meanwhile, the forward-viewing catheter inserted within the left atrium is directed toward the ostium of a pulmonary vein for therapy using the integrated accessory port. Using preloaded, phasing data, the scanner switches between catheters automatically, at the push of a button, with a delay of about 1 second, so that the clinician can view the therapy catheter with the coronary sinus catheter and vice versa. Preliminary imaging studies in a tissue phantom and in vivo show that our system successfully guided the forward-viewing catheter toward a target while being imaged with the sideviewing catheter. The forward-viewing catheter then was activated to monitor the target while we mimicked therapy delivery. In the future, the system will switch between 3-D probes on a line-by-line basis and display both volumes simultaneously. 相似文献
997.
Baier RE 《Journal of materials science. Materials in medicine》2006,17(11):1057-1062
“Biomaterials” are non-living substances selected to have predictable interactions with contacting biological phases, in applications
ranging from medical/dental implants to food processing to control of biofouling in the sea. More than 30 years of empirical
observations of the surface behaviours of various materials in biological settings, when correlated with the contact-angle-determined
Critical Surface Tensions (CST) for these same materials, support the definition of the “theta surface”. The “theta surface”
is that characteristic expression of outermost atomic features least retentive of depositing proteins, and identified by the
bioengineering criterion of having measured CST between 20 and 30 mN/m. Biomaterials applications requiring strong bioadhesion
must avoid this range, while those requiring easy release of accumulating biomass should have “theta surface” qualities. Selection
of blood-compatible materials is a main example. It is forecast that future biomaterials will be safely and effectively translated
directly to clinical use, without requiring animal testing, based on laboratory data for CST, protein denaturation, and cell
spreading alone. 相似文献
998.
Cossmann SM Rothwell EJ Kempel LC 《Journal of the Optical Society of America. A, Optics, image science, and vision》2006,23(9):2320-2323
The time-domain reflection coefficient for a plane wave obliquely incident on a Lorentz-medium half-space is determined analytically by inversion of the frequency-domain reflection coefficient. The resulting expression contains only simple functions and a single convolution of these functions. Owing to its simplicity, this form of the reflection coefficient provides insight into its temporal behavior, specifically how the relationship between the damping coefficient and the oscillation frequency determines the shape of the response. The simple form of the reflection coefficient is validated numerically through comparison with the inverse fast Fourier transform of the frequency-domain reflection coefficient. 相似文献
999.
Knol EF 《Molecular nutrition & food research》2006,50(7):620-624
This article reviews the characteristics of high affinity IgE receptors (FcepsilonRI) and their role in the response to allergenic proteins. The requirements for successful cross-linking of FcepsilonRI on basophils and mast cells and subsequent degranulation by allergenic proteins will be explained in detail. Methods for in vitro analysis of allergen-induced mast cell and basophil degranulation will be described and issues/problems in applying these methods will be discussed. Finally, implications for manipulation of protein allergens will be discussed. 相似文献
1000.
Microstructural evolution during high-temperature oxidation of spark plasma sintered Ti2AlN ceramics
Bai CuiRafael Sa Daniel D. JayaseelanFawad Inam Michael J. ReeceWilliam Edward Lee 《Acta Materialia》2012,60(3):1079-1092
Microstructures of Ti2AlN ceramics synthesized and simultaneously consolidated from starting mixtures of Ti/Al/TiN powders by spark plasma sintering (SPS) were characterized using X-ray diffraction, scanning electron microscopy, focused ion beam (FIB) and transmission electron microscopy (TEM). When sintered for 10 min at 1300 °C, nearly single-phase Ti2AlN ceramics with elongated (∼22 × 6 × 6 μm) grains were obtained. After sintering for 10 min at 1200 °C and chemical etching, Ti2AlN nanowhiskers (150-200 nm dia., 1-5 μm long) were exposed in pores coexisting with TiAl, TiN and Ti2AlN grains. FIB-TEM studies revealed single-crystal Ti2AlN nanowhiskers in a TiAl matrix with orientation relationship [1 1 −2 0]H//[−1 0 1]γ, (0 0 0 1)H//(1 1 1)γ, γ = TiAl, H = Ti2AlN. The nanowhiskers are believed to form by diffusion of TiN into TiAl during SPS and to be exposed during the chemical etch. Microstructural development during high-temperature oxidation of dense Ti2AlN ceramics for 1 h at <1200 °C involves gradual formation on the surface of layered microstructures containing anatase, rutile and α-Al2O3. After 1 h at >1200 °C, more complex layered microstructures containing Al2TiO5, rutile, α-Al2O3 and continuous voids layers form. After heating to 1100 °C for 1 h and cooling to room temperature, planar defects are observed in surface TiO2 grains identified as stacking faults bounded by partial dislocations. After heating for 1 h at 1400 °C and cooling to room temperature, cracks propagate in TiO2 grains. It is believed that planar defects and cracks arise from stress generation in the oxide scale. Thermal stresses formed on cooling may arise from thermal expansion mismatch of phases (TiO2, Al2O3 and Al2TiO5) in the oxide scale, the high anisotropy of thermal expansion in Al2TiO5 and thermal expansion mismatch between the oxide scale and Ti2AlN substrate. Growth stresses formed during the isothermal oxidation treatment may arise from the volume changes associated with oxidation reactions of Ti2AlN. An oxidation mechanism for Ti2AlN ceramics is proposed, which involves initial reaction with atmospheric oxygen to form oxide phases, demixing of the mixed oxide phases, void formation due to the Kirkendall effect and gaseous NOx release. Oxidation of Ti2AlN <1200 °C with 1 h hold times is limited, while above this temperature the oxide scale grows rapidly, and Ti2AlN ceramics undergo heavy oxidation. 相似文献