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91.
92.
Optimization of segmented constrained layer damping with mathematical programming using strain energy analysis and modal data 总被引:2,自引:0,他引:2
A new method for enhancement of damping capabilities of segmented constrained layer damping material is proposed. Constrained layer damping has been extensively used since many years to damp flexural vibrations. The shear deformation occurring in the viscoelastic core is mainly responsible for the dissipation of energy. Cutting both the constraining and the constrained layer, which leads to segmentation, increases the shear deformation at that position. This phenomenon is called edge effect. A two-dimensional model of a cantilever beam has been realized for further investigations. An optimization algorithm using mathematical programming is developed in order to identify a cuts arrangement that optimizes the loss factor. The damping efficiency is estimated using the modal strain energy method. The Nelder–Mead simplex method is used to find the best distribution of cuts. In order to take into account geometrical limitations, the exterior point penalty method is used to transform the constrained objective function into an unconstrained objective function. As the optimization problem is not convex, a modal analysis is performed at each mode in order to identify initial cuts positions that lead to a global minimum. Over a large frequency range, the algorithm is able to identify a distribution of cuts that optimizes the loss factor of each mode under consideration. 相似文献
93.
Gerald J. Hahn 《技术计量学》2013,55(4):337-339
We describe a diagnostic method for assessing the degree to which individual cases and groups of cases influence the Box-Cox likelihood estimate of the transformation parameter for the response variable in linear regression models. We compare the method to a method proposed by Atkinson (1982) and sketch the extension to explanatory variables. We present two examples. 相似文献
94.
Gerald R. Fast 《Canadian Journal of Science, Mathematics, & Technology Education》2013,13(2-3):149-181
Abstract Analogies were used to facilitate reconstructing the probability knowledge of 54 culturally diverse, female, Zimbabwean secondary school students in cases where there were misconceptions in their comprehension of probability. Ten contextually appropriate misconception‐prone target situations were generated, together with their conceptually analogous counterparts, known as source or anchoring situations. The source analogues were designed to draw out those areas where student beliefs agreed with accepted mathematical theory. Students’ responses to the target situations indicated that probability misconceptions were common and that the source analogues were effective in providing anchors for mathematically correct ideas. The participants were interviewed and knowledge reconstruction was attempted using the source analogues. A success rate of 0.88 was achieved. Testing after one month indicated a stability rate of 0.82 for the reconstructed probability knowledge. 相似文献
95.
Asiri K. A. R. Wijenayaka Christopher B. Colby Gerald J. Atkins Peter Majewski 《Journal of materials science. Materials in medicine》2009,20(7):1467-1473
The osteoclast (OC) is the cell type responsible for the resorption of bone. The activity of this cell is important in the
aetiology of a large number of skeletal pathologies, and also for the biocompatibility and osseointegration of orthopaedic
implant materials. OC mediated acid hydrolysis of calcium phosphate from the bone matrix offers a prime means of studying
the biology and activity of this cell type. We have developed a method of coating glass coverslips with a hydroxyapatite (HA)-like
mineral, using a biomimetic approach. Hydroxylation followed by formation of a self assembled monolayer (SAM) using the surfactant
triethoxysilylpropyl succinic anhydride (TESPSA), allowed biomimetic deposition of HA-like mineral from a simulated body fluid
(SBF). The biocompatibility of the TESPSA SAM-HA coated glass coverslips was tested by culturing human mature OC present in
samples of giant cell tumour of bone (GCT). Parameters of OC activity were assayed, including F-actin ring formation, release
of calcium and formation of osteoclastic resorption pits, confirming that OC were able to attach to and resorb the coated
surface. This approach for the preparation of HA coatings on glass coverslips could have wide applicability for the study
of osteoclast behaviour in vitro.
Gerald J. Atkins and Peter Majewski share senior author status. 相似文献
96.
Eddie Hyatt Russell Griffin Loring W. Rue III Gerald McGwin Jr. 《Accident; analysis and prevention》2009,41(5):1075-1079
Motorcyclists have been reported to be more likely to die in a motor vehicle collision (MVC) than automobile occupants. With the recent increase in the pump price of gasoline, it has been reported that people are switching to motorcycles as main modes of transportation. This study evaluated the association between motor vehicle collision-related injury and mortality rates and increases in gasoline prices for occupants of automobiles and riders of motorcycles.There were an estimated 1,270,512 motorcycle MVC and 238,390,853 automobile MVC involved occupants in the U.S. from 1992 to 2007. Higher gasoline prices were associated with increased motorcycle-related injuries and deaths; however, this association no longer remained after accounting for changes in the number of registered vehicles.The current study observed that, while the number of injuries and fatalities in motorcycle-related MVCs increase with increasing gasoline price, rates remained largely unchanged. This suggests that the observed increase in motorcycle-related injuries and fatalities with increasing gasoline price is more a factor of the number of motorcycles on the road rather than operator characteristics. 相似文献
97.
This paper proposes four decision-making procedures to be employed by electric generating companies as part of their bidding strategies when competing in an ologopolistic market: naïve, forward, adaptive, and moving average expectations. Decision-making is formulated in a dynamic framework by using linear control theory. The results reveal that interactions among all GENCOs affect market dynamics. Several numerical examples are reported, and conclusions are presented. 相似文献
98.
99.
The behavior of a single injected bubble in a rectangular air-fluidized bed of glass microspheres has been studied experimentally for the ac and dc applied electric field cases. An empirical dimensionless equation for bubble-rise velocity and bubble volume is reviewed for application below a critical ac electric field strength for significant electromechanical effects. As observed previously, dc experiments in electrofluidized beds are more sensitive to time dependence and to hysteresis effects than are ac experiments, as densely spaced particles tend to become immobilized in the presence of dc electric fields. 相似文献
100.
Ankley GT Diamond SA Tietge JE Holcombe GW Jensen KM Defoe DL Peterson R 《Environmental science & technology》2002,36(13):2853-2858
A number of environmental stressors have been hypothesized as responsible for recent increases in limb malformations in several species of North American amphibians. The purpose of this study was to generate dose-response data suitable for assessing the potential role of solar ultraviolet (UV) radiation in causing limb malformations in a species in which this phenomenon seemingly is particularly prevalent, the northern leopard frog (Rana pipiens). Frogs were exposed from early embryonic stages through complete metamorphosis to varying natural sunlight regimes, including unaltered (100%) sunlight, sunlight subjected to neutral density filtration to achieve relative intensities of 85%, 75%, 65%, 50%, and 25% of unaltered sunlight, and sunlight filtered with glass or acrylamide to attenuate, respectively, the UVB (290-320 nm) and UVB plus UVA (290-380 nm) portions of the spectrum. The experiments were conducted in a controlled setting, with continual monitoring of UVB, UVA, and visible light to support a robust exposure assessment. Full sunlight caused approximately 50% mortality of the frogs during early larval development; no significant treatment-related mortality occurred under any of the other exposure regimes, including 100% sunlight with glass or acrylamide filtration. There was a dose-dependent (p < 0.0001) induction of hindlimb malformations in the frogs, with the percentage of affected animals ranging from about 97% under unaltered sunlight to 0% in the 25% neutral density treatment. Malformations were comprised mostly of missing or truncated digits, and generally were bilateral as well as symmetrical. Filtration of sunlight with either glass or acrylamide both significantly reduced the incidence of malformed limbs. The estimated sunlight dose resulting in a 50% limb malformation rate (ED50) was 63.5%. The limb ED50 values based on measured sunlight intensities corresponded to average daily doses of 4.5 and 100 Wh x m(-2) for UVB and UVA, respectively. Exposure to sunlight also resulted in increased eye malformations in R. pipiens, however, the dose-response relationship for this endpoint was not monotonic. The results of this study, in conjunction with measured or predicted exposure data from natural settings, provide a basis for quantitative prediction of the risk of solar UV radiation to amphibians. 相似文献