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71.
72.
New algorithms and results are presented for flutter testing and adaptive notching of structural modes in V-22 tiltrotor aircraft
based on simulated and flight-test data from Bell Helicopter Textron, Inc. (BHTI). For flutter testing and the identification
of structural mode frequencies, dampings and mode shapes, time domain state space techniques based on Deterministic Stochastic
Realization Algorithms (DSRA) are used to accurately identify multiple modes simultaneously from sine sweep and other multifrequency
data, resulting in great savings over the conventional Prony method. Two different techniques for adaptive notching are explored
in order to design an Integrated Flight Structural Control (IFSC) system. The first technique is based on on-line identification
of structural mode parameters using DSRA algorithm and tuning of a notch filter. The second technique is based on decoupling
rigid-body and structural modes of the aircraft by means of a Kalman filter and using rigid-body estimates in the feedback
control loop. The difference between the two approaches is that on-line identification and adaptive notching in the first
approach are entirely based on the knowledge of structural modes, whereas the Kalman filter design in the second approach
is based on the rigid-body dynamic model only. In the first IFSC design, on-line identification is necessary for flight envelope
expansion and to adjust the notch filter frequencies and suppress aero-servoelastic instabilities due to changing flight conditions
such as gross weight, sling loads, and air speed. It is shown that by tuning the notch filter frequency to the identified
frequency, the phase lag is reduced and the corresponding structural mode is effectively suppressed and stability is maintained.
In the second IFSC design using Kalman filter design, the structural modes are again effectively suppressed. Furthermore,
the rigid-body estimates are found to be fairly insensitive to both natural frequency and damping factor variations and therefore
stability is maintained. The Kalman filter design might be a better choice when the rigid-body dynamics are well known because
no adaptation is necessary in this case. 相似文献
73.
Sampath Kumar Puttapati Venkataramana Gedela Vadali V S S Srikanth M V Reddy Stefan Adams B V R Chowdari 《Bulletin of Materials Science》2018,41(2):53
Unique reduced graphene oxide named solar reduced graphene oxide (SRGO) was found to be an excellent anode material in Li ion battery. SRGO exhibited first cycle discharge- and charge-capacities as high as 1480 and 880 mAh \(\hbox {g}^{-1}\), respectively. Moreover, the columbic efficiency was found to be >95% and the specific capacity retention even after 60 cycles was >500 mAh \(\hbox {g}^{-1}\). 相似文献
74.
Vishnu Priya Sampath Shiv Vardan Singh Ilana Pelov Ofir Tirosh Yigal Erel David Lichtstein 《International journal of molecular sciences》2022,23(22)
Bipolar Disorder (BD) is a severe recurrent affective mood disorder characterized by a wide range of lifelong mood swings, varying between depressive and manic states. BD affects more than 1% of the world’s population irrespective of nationality, ethnic origin, or socioeconomic status and is one of the main causes of disability among young people, leading to cognitive and functional impairment and raised mortality, particularly death by suicide. Trace elements play a vital role in many biochemical and physiological processes. Compelling evidence shows that element toxicity might play a crucial role in the onset and progression of neurodegenerative disorders, but their involvement in mood disorders has been scarcely studied. In the present investigation, we determined the concentration of 26 elements in the serum of BD patients before and after treatment and in postmortem brain samples from BD patients and compared them with matched controls. The only element that was reduced significantly in the serum following treatment was vanadium (V). Furthermore, the concentration of Al, B, Cu, K, Mg and V were significantly lower in the pre-frontal cortex of BD patients compared with those of the controls. A comparison of Spearman’s rank correlation coefficients between the elements in the serum and brain of BD patients and control groups pointed to boron and aluminum as being involved in the disease. These results suggest that there is a disturbance in the elements’ homeostasis and the inter-elements’ relationship in the brain of BD patients and advocate a thorough examination of the possible involvement of chemical elements in different stages of the disease. 相似文献
75.
Felipe R. Caliari Eugenio Garcia Felipe Miranda Gilberto Petraconi Filho Sanjay Sampath 《Journal of the European Ceramic Society》2021,41(10):5248-5257
Nb2O5 polymorphism and defect chemistry depend on the temperature, pressure, atmosphere composition and the initial crystallography. Plasma spray of Nb2O5 is a pathway to form coatings with in-situ metastable and nonstoichiometric phases, however so far unexplored. This study aimed to understand the phase evolution of plasma sprayed Nb2O5 coatings, and its effect on their morphology and properties. Phase evolution from H-Nb2O5 in the feedstock, to T-Nb2O5, TT-Nb2O5, N-Nb2O5, H-Nb2O5, Nb12O29 and NbO2 in the coatings depends on the plasma Ar/H2 ratio and its related enthalpy. The microstructure shows a layered distribution of nonstoichiometric phases at the splat boundaries and splat cores composed of T-Nb2O5 or TT-Nb2O5. The presence and distribution of these phases are related to the thermomechanical and electrical properties. The mechanisms driving the formation of these coatings are based on the Nb2O5 incongruent vaporization which promote retention of nonstoichiometric phases and the rapid solidification of metastable phases. 相似文献
76.
Thin films of tellurium of wide range of thicknesses have been deposited by vacuum evaporation and their electrical properties
such as electrical resistivity and temperature coefficient of resistance have been measured. The suitability of these films
for possible use as strain gauges has been studied and their strain resistivity behaviour is presented. The thermal conductivity
of these films have been determined and these results are presented alongwith. An interesting phenomenon has been noticed.
In all these effects an extraordinary behaviour is observed at a specific thickness. This smears out with an increase in the
thickness of the film. These effects are explained in terms of size effects in thin films. 相似文献
77.
78.
Dual-polarization versus single-polarization MIMO channel measurement results and modeling 总被引:1,自引:0,他引:1
This paper presents a simple multiple-input-multiple-output (MIMO) channel model that predicts the eigenvalue distribution and hence, the capacity of MIMO systems using vertically polarized and dual-polarized transmit-antenna configurations with dual-polarized receive antennas. The channel model is verified using broadband outdoor channel measurements taken by a 2 x 3 MIMO system in the 2.5 GHz band. 相似文献
79.
Bone morphogenetic proteins induce chondrogenesis and osteogenesis in vivo. To investigate molecular mechanisms involved in chondrocyte induction, we examined the effect of osteogenic protein (OP)-1/bone morphogenetic protein-7 on the collagen X promoter. In rat calvaria-derived chondrogenic C5.18 cells, OP-1 up-regulates collagen X mRNA levels and its promoter activity in a cell type- specific manner. Deletion analysis localizes the OP-1 response region to 33 bp (-310/-278), which confers OP-1 responsiveness to both the minimal homologous and heterologous Rous sarcoma virus promoter. Transforming growth factor-beta2 or activin, which up-regulates the expression of a transforming growth factor-beta-inducible p3TP-Lux construct, has little effect on collagen X mRNA and on this 33-bp region. Mutational analysis shows that both an AP-1 like sequence (-294/-285, TGAATCATCA) and an A/T-rich myocyte enhancer factor (MEF)-2 like sequence (-310/-298, TTAAAAATAAAAA) in the 33-bp region are necessary for the OP-1 effect. Gel shift assays show interaction of distinct nuclear proteins from C5.18 cells with the AP-1-like and the MEF-2-like sequences. OP-1 rapidly induces nuclear protein interaction with the MEF-2-like sequence but not with the AP-1 like sequence. MEF-2-like binding activity induced by OP-1 is distinct from the MEF-2 family proteins present in C2C12 myoblasts, in which OP-1 does not induce collagen X mRNA or up-regulate its promoter activity. In conclusion, we identified a specific response region for OP-1 in the mouse collagen X promoter. Mutational and gel shift analyses suggest that OP-1 induces nuclear protein interaction with an A/T-rich MEF-2 like sequence, distinct from the MEF-2 present in myoblasts, and up-regulates collagen X promoter activity, which also requires an AP-1 like sequence. 相似文献
80.
Saifi Usmani Sanjay Sampath Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1996,48(11):51-54
The solid-particle erosion resistance of ceramic thermal barrier coatings (TBCs) is of considerable economic and industrial significance. Of additional significance to the service performance of these coatings is the effort to minimize the differences in coefficients of thermal expansion between the metallic substrate and the overlay TBC. A new design strategy toward this effort is the introduction of functionally graded interlayers between the metallic and ceramic layers. This research examines the role of interlayer grading, microstructure, and thermal cycling on the solid-particle erosion behavior of partially stabilized zirconia and alumina coatings at ambient and elevated temperatures. The results point to beneficial effects of grading and processing on the elevated temperature erosion response of these deposits. 相似文献