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991.
Margolin Arthur; Avants S. Kelly; Warburton Lara A.; Hawkins Keith A.; Shi Julia 《Canadian Metallurgical Quarterly》2003,22(2):223
This study randomized 90 HIV-seropositive, methadone-maintained injection drug users (IDUs) to an HIV Harm Reduction Program (HHRP+) or to an active control that included harm reduction components recommended by the National AIDS Demonstration Research Project. The treatment phase lasted 6 months, with follow-ups at 6 and 9 months after treatment entry. Patients in both treatments showed reductions in risk behaviors. However, patients assigned to HHRP+ were less likely to use illicit opiates and were more likely to adhere to antiretroviral medications during treatment; at follow-up, they had lower addiction severity scores and were less likely to have engaged in high risk behavior. Findings suggest that enhancing methadone maintenance with an intervention targeting HIV-seropositive IDUs increases both harm reduction and health promotion behaviors. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
992.
Francesc Torrades Julia García-Montao Jos Antonio García-Hortal Xavier Domnech Jos Peral 《Solar Energy》2004,77(5):573-581
The degradation of different commercial reactive dyes: a monoreactive dye (Procion Red H-E7B), an hetero-bireactive dye (Red Cibacron FN-R) and a Standard Trichromatic System, by using solar light assisted Fenton and photo-Fenton reaction is investigated. The reaction efficiencies have been compared with the ones obtained for the same system in the dark or under the assistance of an artificial light source. The use of solar light is clearly beneficial for the removal of color, aromatic compounds (UV254), total organic carbon (TOC), and the increase of the BOD5/COD ratio. The possibility of a combined advanced oxidation process (AOP)/biological treatment based on the use of sunlight is suggested. 相似文献
993.
Four studies explored the motivational and experiential dynamics of psychological needs, applying both self-determination theory and motive disposition theory. In all 4 studies, motive dispositions toward achievement and affiliation (“wanting” particular experiences) predicted corresponding feelings of competence and relatedness (“having” those experiences). Competence and relatedness in turn predicted well-being, again indicating that these 2 experiences may really be “needed.” Illuminating how wanting gets to having, in Studies 2 and 3, participants reported greater self-concordance for motive-congruent goals, which, in longitudinal Study 3, predicted greater attainment of those goals and thus enhanced well-being. Study 4 replicated selected earlier results using an implicit as well as an explicit motive disposition measure. Supporting the presumed universality of competence and relatedness needs, in no studies did motive dispositions moderate the effects of corresponding need-satisfaction on well-being. Discussion focuses on a “sequential process” model of psychological needs that views needs as both motives that instigate and outcomes that reward behavior. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
994.
Three-dimensional profiling with binary fringes using phase-shifting interferometry algorithms 总被引:2,自引:0,他引:2
Ayubi GA Di Martino JM Alonso JR Fernández A Perciante CD Ferrari JA 《Applied optics》2011,50(2):147-154
Three-dimensional shape measurements by sinusoidal fringe projection using phase-shifting interferometry algorithms are distorted by the nonlinear response in intensity of commercial video projectors and digital cameras. To solve the problem, we present a method that consists in projecting and acquiring a temporal sequence of strictly binary patterns, whose (adequately weighted) average leads to a sinusoidal fringe pattern with the required number of bits. Since binary patterns consist of "ones" and "zeros"--and no half-tones are involved--the nonlinear response of the projector and the camera will not play a role, and a nearly unit contrast gray-level sinusoidal fringe pattern is obtained. Validation experiments are presented. 相似文献
995.
Anne-Kathrin Maier Laura Dezmirean Julia Will Peter Greil 《Journal of Materials Science》2011,46(9):2947-2954
Three-dimensional indirect printing of flash-setting calcium aluminate cement (CAC) was investigated. Upon water injection
into a biphasic mixture of tricalcium aluminate (3CaO·Al2O3) and dodecacalcium heptaaluminate (12CaO·7Al2O3) (phase ratio 0.56/0.44) initially a gel formed acting as a bonding phase which stabilizes the printed object geometry. Post-exposure
in water finally resulted in the formation of 2CaO·Al2O3·8H2O and 4CaO·Al2O3·19H2O reaction phases as confirmed by SEM, X-ray diffraction, and FTIR analyses. Reduction of porosity by volume expansion upon
hydrolysis reaction from 50% after printing to 20% after post-treatment gave rise for an increase of compressive strength
from 5 to 20 MPa, respectively. A bone regenerating scaffold for a micro-vascular loop model was fabricated by 3D printing
and hydraulic reaction bonding to demonstrate the potential of using flash-setting calcium aluminate cement powder for biomedical
ceramic applications. 相似文献
996.
Dmitry Shepelev Julia Klempf Menachem Bamberger Alex Katsman 《Journal of Materials Science》2011,46(17):5798-5806
Improved mechanical properties and structural uniformity of Mg-based alloys can be achieved by use of grain-refining additives
prior to casting. Ceramic particles of α-Al2O3 and SiC can serve as such additives to refine the microstructure of Mg–Al-based alloys. However, direct introduction of ceramic
particles into Mg matrix is limited by the poor wetting of those particles by liquid Mg and their massive agglomeration. Mg/α-Al2O3 and Mg/SiC master alloys were prepared using a method based on the insertion of the ceramic particles into a molten Mg bath
through a Mg-nitride layer formed on the surface of the molten bath. The mixture of Mg/ceramic particles was cooled to room
temperature under a nitrogen atmosphere. Mg-15%Al2O3 and AZ91E + 10%SiC master alloys were obtained. These master alloys were used to refine AZ91E alloys by introducing various
amounts of ceramic particles to manufacture AZ91E + 1%Al2O3, AZ91E + 1%SiC, and AZ91E + 3%SiC alloys. These were cast using high-pressure die casting and gravity die casting. The alloy
AZ91E + 1%Al2O3 was grain refined to ~20 μm and the alloys AZ91E + SiC were grain refined to ~50 μm as against 110 μm in non-refined counterparts.
The mechanical properties of the modified alloys are substantially better than those of a non-refined AZ91E alloy which is
the result of a combination of grain refinement and reinforcement of the matrix by ceramic particles. Alloy AZ91E + 1%Al2O3 exhibited the best mechanical properties. 相似文献
997.
A material strength depends on its microstructure, which in turn, is controlled by an engineering process. Strengthening mechanisms like work hardening, precipitate, and grain boundary strengthening can alter the strength of a material in a predictive, quantitative manner and are readily linked to the deformation mechanism. This quantification strongly depends on the characteristic length scale of a particular microstructure, thereby dictating bulk material’s strength as a function of, for example, grain or precipitate size, twin boundary spacing, or dislocation density. This microstructural, or intrinsic, size governs the mechanical properties and post-elastic material deformation at all sample dimensions, as the classical definition of “ultimate tensile strength” deems it to be “an intensive property, therefore its value does not depend on the size of the test specimen.” Yet in the last 5 years, the vast majority of uniaxial deformation experiments and computations on small-scale metallic structures unambiguously demonstrated that at the micron and sub-micron scales, this definition no longer holds true. In fact, it has been shown that in single crystals the ultimate tensile strength and the yield strength scale with external sample size in a power law fashion, sometimes attaining a significant fraction of material’s theoretical strength, and exhibiting the now-commonly-known phenomenon “smaller is stronger.” Understanding of this “extrinsic size effect” at small scales is not yet mature and is currently a topic of rigorous investigations. As both the intrinsic (i.e. microstructural) and extrinsic (i.e. sample size) dimensions play a non-trivial role in the mechanical properties and material deformation mechanisms, it is critical to develop an understanding of their interplay and mutual effects on the mechanical properties and material deformation, especially in small-scale structures. This review focuses on providing an overview of metal-based material classes whose properties as a function of external size have been investigated and provides a critical discussion on the combined effects of intrinsic and extrinsic sizes on the material deformation behavior. 相似文献
998.
The silica nanoparticles with a rough surface were developed using a silane precursor in a reverse microemulsion followed by a drying treatment. The surface roughness of the nanoparticles was adjustable by changing the amount of the precursor. Within a certain range, the roughness increased as the amount of the silane precursor increased. The rough surface provided a larger surface area than the smooth one. The produced nanoparticles were characterized using the transmission electron microscopy, ultraviolet-visible spectroscopy, energy-dispersive X-ray elemental analysis, and Brunauer-Emmet-Teller analysis technique. Additionally, the amount of surface functional amino groups on the nanoparticles was detected using the traditional acid-base titration and the dissociation constant of this functional group was calculated. On the basis of the experimental results, the mechanism of the formation of the rough surface was proposed. Finally, the produced silica nanoparticles were utilized as a carrier for the chemical binding of a near-infrared dye molecule and the adsorption of the gold nanoparticles. The results demonstrated that the rough surface provide the silica nanoparticles with a high capacity of surface chemical and supramolecular reactions. 相似文献
999.
LaGrange Beth; Cole David A.; Jacquez Farrah; Ciesla Jeff; Dallaire Danielle; Pineda Ashley; Truss Alanna; Weitlauf Amy; Tilghman-Osborne Carlos; Felton Julia 《Canadian Metallurgical Quarterly》2011,120(3):511
In a four-wave, cohort-longitudinal design with a community sample of 515 children and adolescents (grades 2 through 9), this study examined the longitudinal structure of and prospective interrelations between maladaptive cognitions and depressive symptoms. Multigroup structural equation modeling generated four major findings. First, the longitudinal structures of maladaptive cognitions and depressive symptoms consist of a single time-invariant factor and a series of time-varying factors. Second, evidence supported a model in which depressive symptoms predicted negative cognitions but not the reverse. Third, the time-invariant components of cognition and depression were highly correlated. Fourth, the strength of the depression-to-cognition relation increased with age. Implications regarding the mechanisms underlying clinical interventions with depressed children are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
1000.
In this study, an isothermal microcalorimetric technique has been used to show that beta-cypermethrin (CYP) had no significant effect (p > 0.05) on soil microbial activity at 80 μg g(-1) soil. Our soil enzyme data indicated that beta-CYP ranging 10-80 μg g(-1) soil had no significant effect (p > 0.05) on soil enzyme activities such as β-glucosidase, urease, acid-phosphatase, and dehydrogenase. Therefore, our results infer that beta-CYP would not pose severe toxicity to soil microbial community, but its toxic level may vary greatly with environment that associates with its increase in bioavailability: the level in soil (at μg g(-1)) < the level in sediment (varying from μg g(-1) to μg L(-1)) 0.05). These results suggest that the heavy application of beta-CYP may not cause damage to soil microbial community which is very different from its high toxicity to the aquatic organism. 相似文献