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51.
52.
Peter W. Lucas Ridwaan Omar Khaled Al-Fadhalah Abdulwahab S. Almusallam Amanda G. Henry Shaji Michael Lidia Arockia Thai J?rg Watzke David S. Strait Anthony G. Atkins 《Journal of the Royal Society Interface》2013,10(80)
The wear of teeth is a major factor limiting mammalian lifespans in the wild. One method of describing worn surfaces, dental microwear texture analysis, has proved powerful for reconstructing the diets of extinct vertebrates, but has yielded unexpected results in early hominins. In particular, although australopiths exhibit derived craniodental features interpreted as adaptations for eating hard foods, most do not exhibit microwear signals indicative of this diet. However, no experiments have yet demonstrated the fundamental mechanisms and causes of this wear. Here, we report nanowear experiments where individual dust particles, phytoliths and enamel chips were slid across a flat enamel surface. Microwear features produced were influenced strongly by interacting mechanical properties and particle geometry. Quartz dust was a rigid abrasive, capable of fracturing and removing enamel pieces. By contrast, phytoliths and enamel chips deformed during sliding, forming U-shaped grooves or flat troughs in enamel, without tissue loss. Other plant tissues seem too soft to mark enamel, acting as particle transporters. We conclude that dust has overwhelming importance as a wear agent and that dietary signals preserved in dental microwear are indirect. Nanowear studies should resolve controversies over adaptive trends in mammals like enamel thickening or hypsodonty that delay functional dental loss. 相似文献
53.
A CFD code with 2-D cascade model was developed to predict the cavitation behavior around the impeller blades of impeller
in a centrifugal pump. The governing equations are the two-phase Reynolds Averaged Navier-Stokes equations in a homogeneous
form in which both liquid and vapor phases are treated as incompressible fluid. To close the model, a standard k-ɛ turbulence
model is introduced. And the mass transfer rates between liquid and vapor phases are implemented as well. The validations
are carried out by comparing with reference data in impeller of a centrifugal pump impeller. The cavitation characteristics
of current centrifugal pumps is tested at an ondesign point (V=8 m/s) and two off-design points (V=20 m/s and V=30 m/s), respectively.
The criteria of cavitation and flow instability around blades are presented. The results show that the current centrifugal
pump can safely operate without cavitation at on-design point. Also, the simulation shows cavitation develops inhomogeneously
among the blades at off-design points. Moreover, the effects of additional blades in the impeller are studied as well. From
the numerical results, it is expected that a half-length blade is the optimum configuration as additional blades in cavitation
point of view. 相似文献
54.
Munawar Hussain Nguyen Thai Hung Rasheed Ahmad Khera Imran Malik Dhafer Saber Zinad Peter Langer 《Advanced Synthesis \u0026amp; Catalysis》2010,352(9):1429-1433
Suzuki–Miyaura reactions of 2,4,5,6‐tetrachloropyrimidine allow a convenient synthesis of mono‐, di‐, tri‐ and tetraarylpyrimidines which are not readily available by other methods. All reactions proceed with excellent site‐selectivity. 相似文献
55.
N. K. Rastogi Loc Thai Nguyen Bo Jiang V. M. Balasubramaniam 《Food and Bioprocess Technology》2010,3(5):762-771
The effect of pretreatment pressure (0.1 to 400 MPa), temperature (25 to 75 °C), and calcium chloride concentration (0 to
1.5%) and their complex interaction on hardness, residual pectinmethylesterase (PME) activity, and diffused calcium content
of pressure-assisted thermal processed (PATP, 700 MPa, 105 °C for 15 min) carrot have been studied using response surface
methodology. Predicted values of carrot hardness, calcium content, and residual PME activity were found to be in good agreement
with experimental values as indicated by the high R
2 values of 0.98, 0.96 and 0.96, respectively. The optimum processing conditions, namely, calcium chloride concentration 1.0%;
pretreatment pressure ranging from 286 to 314 MPa; pretreatment temperature varying from 53.8 to 58.3 °C, fulfill the conditions
to obtain the PATP carrot with hardness ≥145 N, calcium content ≥ 2.5 mg/g, and residual PME activity ≥ 70%. These conditions
resulted in more than tenfold increase in the hardness of PATP carrot (14.08 to 145 N) as compared to PATP carrot without
any pretreatment. The study demonstrated that response surface methodology can be used for modeling carrot quality parameters
of PATP. 相似文献
56.
A simple and versatile approach to constructing patterns on a solid surface using nanoscale objects is demonstrated. The approach is essentially an inlaying process, in which recess patterns fabricated on a surface are selectively filled with nanoscale objects. The objects are anchored firmly on the surface due to the spatial confinement provided by the recess structures. Protein molecules and inorganic nanoparticles are used in this demonstration. Cyclic voltammetry is used to detect electron transfer signals from patterns of protein molecules. The approach suggests a potentially fast, high-throughput and versatile technique for constructing architectural structures on a solid surface using nanoscale objects. 相似文献
57.
Nguyen HL Leermakers M Elskens M De Ridder F Doan TH Baeyens W 《The Science of the total environment》2005,341(1-3):211-226
Correlations between trace metals in dissolved and particulate phases, zooplankton, mussels and sediments in Lake Balaton were investigated. The degree of correlation between the various metals was different in each of the investigated compartments. Particulate metal concentrations (microg g(-1)) were anti-correlated with suspended particulate matter (SPM) (mg l(-1)), indicating a dilution effect, while total metal concentrations in the water column (microg l(-1)) were highly correlated with SPM, implying a major influence of the turbidity on the total metal concentrations. Between compartments, not many significant correlations were recognized. Only Ba, Ca, Sr and Mg are correlated in the sediments and in the particulate phase, suggesting common sources for both compartments. Partitioning coefficients (Kd) of trace metals between dissolved and particulate phases are generally low, typical for natural water and fairly stable over the lake. Most of the trace metals (Zn, Co, Cd and Pb) exist in the particulate phase (for about 70% of the total metal load). Cu and Ni are exceptions, showing a more equal distribution. Bioconcentration factors (BCF) of zooplankton and mussels were comparable to those of other natural waters. A negative biomagnification from suspended particulate matter to zooplankton and from sediment to mussel was recognized for all trace metals, except a small enrichment of Zn in zooplankton and Cd in mussel. Four factors were recognized in SPM and in sediments but they did not contain the same group of metals. Cluster analysis showed that metal accumulations in the sediments were different between northern and southern shores and in SPM between western and eastern areas. 相似文献
58.
Zhuolu Li Yingjie Lyu Zhao Ran Yujia Wang Yang Zhang Nianpeng Lu Meng Wang Michel Sassi Thai Duy Ha Alpha T. N'Diaye Padraic Shafer Carolyn Pearce Kevin Rosso Elke Arenholz Jenh-Yih Juang Qing He Ying-Hao Chu Weidong Luo Pu Yu 《Advanced functional materials》2023,33(17):2212298
Magnetic spinel oxides have attracted extensive research interest due to their rich physics and wide range of applications. However, these materials invariably suffer suppressed magnetization, due to structural imperfections (e.g., disorder, anti-site defects, etc.). Herein, a dramatic enhanced magnetization is obtained with an increasement of 5 µB/u.c in CoFe2O4 (CFO) through ionic liquid gating induced hydrogen doping. The intercalated hydrogen ions lead to both distinct lattice expansion of ≈0.7% and notable Fe valence state reduction through electron doping, in which ≈17% Fe3+ is reduced into Fe2+. These facts collectively trigger a site-specific spin-flip on tetrahedrally coordinated Co2+ sites that enhances the net ferrimagnetic moment nearly to its theoretical maximum for perfect CFO. 相似文献
59.
Costache Romulus Arabameri Alireza Costache Iulia Crăciun Anca Pham Binh Thai 《Water Resources Management》2022,36(12):4765-4783
Water Resources Management - Floods are among the most severe natural hazard phenomena that affect people around the world. Due to this fact, the identification of zones highly susceptible to... 相似文献
60.
Yuanhui Zheng Thibaut Thai Philipp Reineck Ling Qiu Yueming Guo Udo Bach 《Advanced functional materials》2013,23(12):1519-1526
The excitation of surface plasmons in metallic nanostructures provides an opportunity to localize light at the nanoscale, well below the scale of the wavelength of the light. The high local electromagnetic field intensities generated in the vicinity of the nanostructures through this nanofocusing effect are exploited in surface enhanced Raman spectroscopy (SERS). At narrow interparticle gaps, so‐called hot‐spots, the nanofocusing effect is particularly pronounced. Hence, the engineering of substrates with a consistently high density of hot‐spots is a major challenge in the field of SERS. Here, a simple bottom‐up approach is described for the fabrication of highly SERS‐active gold core‐satellite nanostructures, using electrostatic and DNA‐directed self‐assembly. It is demonstrated that well‐defined core‐satellite gold nanostructures can be fabricated without the need for expensive direct‐write nanolithography tools such as electron‐beam lithography (EBL). Self‐assembly also provides excellent control over particle distances on the nanoscale. The as‐fabricated core‐satellite nanostructures exhibit SERS activities that are superior to commercial SERS substrates in signal intensity and reproducibility. This also highlights the potential of bottom‐up self‐assembly strategies for the fabrication of complex, well‐defined functional nanostructures with future applications well beyond the field of sensing. 相似文献