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排序方式: 共有684条查询结果,搜索用时 15 毫秒
1.
《Ceramics International》2022,48(18):26055-26062
Indo-Pacific glass beads are produced by the drawn technique, which originates from South Asia, and their chemical compositions are unique in South and Southeast Asia. However, a small number of Indo-Pacific beads with Sassanian glass compositions are excavated in Asia and Africa after the 3rd c. CE, and their production sites in South/Southeast Asia or in the Sassanian region remain controversial. In this study, 15 drawn glass beads with various colours from Astana necropolis (ca. the 4th-8th c. CE) in Xinjiang, northwest China were investigated by using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), Scanning Electron Microscope, Raman spectroscopy and visible to near-infrared spectroscopy to characterize the production technology and origins. The results show that most Astana glass beads share similar chemical compositions with the glassware from Veh Arda?īr, a famous Sasanian site. Furthermore, Sasanian glass compositions predominate in Indo-Pacific beads in Xinjiang during the 4th-8th c. CE, while popular glass recipes in contemporary South/Southeast Asia are infrequently found; thus, it is deduced that the drawn method should have been mastered by Sasanian craftsmen. Moreover, the cobalt materials in Sasanian glass were imported from further western regions and changed over time. The popular Sasanian glass across central Eurasia reflects the trade monopoly of Sasanian in West and Central Asia, and the land glass bead trade is distinct from the contemporary maritime trade in the Indian and Pacific Oceans. 相似文献
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The production of porous polymeric particles is attractive for a large number of applications and can be achieved by various techniques. Although numerous production schemes exist for glassy polymers, difficulties arise for soft, rubbery materials that need a chemical crosslinking step, such as elastomers. This is particularly true for poly(dimethylsiloxane) (PDMS), which shows the lowest glass‐transition temperature among the polymers. Recent studies suggest in situ hydrogen bubble formation or vacuum drying of water droplets dispersed in the polymer matrix in order to generate porous PDMS structures. In this work we report early results based on the chemical crosslinking of water in PDMS emulsion droplets in a mechanically stirred thermostated water vessel. This approach is shown to lead to high porosity PDMS beads (ca. 10?3 m particle diameter) with an open structure whose properties (diameter and porosity) are strongly influenced by the starting composition (solvent, surfactant, and polymer types and ratios), as well as the operating parameters (agitation and temperature). The possible uses of these derived beads are discussed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 967–971, 2002 相似文献
5.
Preparation and characterization of porous carbon beads and their application in dispersing small metal crystallites 总被引:2,自引:0,他引:2
Porous carbon beads were prepared by the pyrolysis of poly(vinylidene chloride) beads that were synthesized by suspension polymerization. After prolysis treatment at 180–300 °C under argon stream, the polymeric beads were further carbonized at 1000 °C for 3 h under argon stream to acquire porous carbon beads, of which the specific surface area was about 1000 m2/g, and pore size was mainly in the width range of 0.8–1.2 nm. The carbon structure and surface chemical composition characterized by X-ray diffraction and X-ray photoelectron spectroscopy, depended on the preparation temperature and the relations between them were examined. The characterization of the carbon beads by scanning electron microscopy, atomic force microscopy presented the morphological structure of the carbon beads surface and a global view of pores. The dispersion of nickel crystallites on the carbon beads surface was characterized by electron microprobe analysis. This study reveals that uniform surface morphological structure leads to the fine dispersion of metal crystallites. 相似文献
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Nuran Iiklan 《应用聚合物科学杂志》2006,99(4):1310-1319
Interpenetrating network polymeric beads of sodium alginate (NaAlg) and its blend with gelatin (gels) or sodium carboxymethyl cellulose (NaCMC) have been prepared by crosslinking with a common crosslinking agent, glutaraldehyde (GA), for the release of insecticide carbaryl (Carb). The prepared beads were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Scanning electron microscopy confirmed the spherical nature and surface morphology of the particles. Bead characteristics, such as carbaryl entrapment efficiency, particle size, equilibrium swelling degree, and carbaryl release kinetics, were determined. The effects of the preparation conditions, such as Carb/NaAlg ratio, time of exposure to GA, blend ratio, and temperature of release medium on the carbaryl release, were investigated for 25 days at 25°C. It was observed that the carbaryl release decreased with increase in crosslinking of network, while it increased with increase in Carb/NaAlg ratio and temperature. The release of carbaryl also increased with increase in Gel or NaCMC content in the blend beads. The highest carbaryl release was found to be 100%, for the beads that were prepared with 1 : 1 NaAlg/Gel at 16 days. The diffusion coefficients have been calculated for the transport of insecticide through the polymeric beads, using initial time approximation method. These values were also consistent with the carbaryl release data. The carbaryl release from most of the bead formulations followed the Fickian trend. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1310–1319, 2006 相似文献
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Novel morphologies of activated carbons such as monolith, beads and fiber cloth can effectively capture organic vapors from industrial sources. These adsorbent materials are also unique because they can undergo direct electrothermal regeneration to recover the adsorbed organic vapors for potential re-use. This investigation compares and contrasts the properties of these adsorbents when using electrothermal-swing adsorption. The adsorption systems consisted of an organic vapor generation system, an electrothermal-swing adsorption vessel, a gas detection unit, and a data acquisition and control system. The activated carbon monolith (ACM) had the lowest pressure drop, highest permeability, highest electrical resistivity and lowest cost as compared to the activated carbon beads (ACB) and the activated carbon fiber cloth (ACFC). ACB had the largest throughput ratio and lowest length of unused bed as compared to the other adsorbents. However, ACFC had the largest adsorption capacity for toluene when compared to ACM and ACB. ACFC was also faster to regenerate and had a larger concentration factor than ACM and ACB. These results describe relevant physical, electrical, adsorption and cost properties for specific morphologies of the adsorbents to more effectively capture and recover organic vapors from gas streams. 相似文献
8.
目的应用生物反应器培养细胞和病毒,大规模生产人用狂犬病疫苗。方法以巴斯德PV2061为毒种,以143代以内Vero细胞为培养基质,应用生物反应器,每升投放25g微载体,灌流式细胞培养,连续收获病毒液,经浓缩、灭活、纯化,制成Vero细胞狂犬病疫苗。结果细胞培养密度达1.2×107~1.5×107个/ml,病毒感染后可连续收获18~22d,病毒最高滴度8.5LogLD50/ml,平均滴度7.6LogLD50/ml。经柱层析纯化,杂蛋白去除率达99.95%以上,总蛋白含量≤80μg/g,DNA含量≤10pg/0.5ml,GP含量3.5~4.5IU/0.5ml,效力≥4.5IU/0.5ml。结论应用生物反应器细胞培养,可以大规模生产优质Vero细胞人用狂犬病疫苗。 相似文献
9.
Porous carbon beads were prepared by carbonizing at 700 and 1000 °C under N2 (NN-series) or CO2 atmospheres (CO-series) and a subsequent oxidization with boiling nitric acid solution (13%, v/v) for 3 h (ANN- and ACO-series). BET surface area of both CO- and NN-series samples tends to increase with increasing carbonization temperature, but CO-series samples show higher BET surface areas (700 °C: 610 m2/g, 1000 °C: 780 m2/g) compared with those of NN-series samples (700 °C: 380 m2/g, 1000 °C: 580 m2/g). After acid oxidation, BET surface areas of NN-series samples increased from 580 to 650 m2/g, whereas those of CO-series samples decreased from 780 to 600 m2/g. On subsequent acid oxidation, acidic surface functional groups increased in both CO- and NN-series samples, but the CO-series samples tend to have much more acidic surface functional groups. Adsorption of halogenated methanes, such as tetra-, tri- and dichloromethanes, onto the samples of CO-, NN-, ACO- and ANN-series was thought to be driven initially by the basicity, but the acidic functional groups that could attract adsorbates via dipole-dipole interaction might hinder the adsorption of subsequently incoming adsorbates. 相似文献
10.
We have developed a method that would allow for the fabrication of carbon aerogel (CA) spheres. The inverse phase suspension polymerization of resorcinol and formaldehyde monomers with Na2CO3 as a catalyst followed by supercritical drying was explored. The effects of the chemical formulation and processing procedures and the conditions of the structures of organic and related carbon aerogels were studied. The experimental results indicated that it was easy to avoid the accumulation of polymerization heat during gelation, and easy to take out the products from the reaction container, through this fabrication method. Sol-gel microspheres with diameters ranging from about 30-1000μm could be obtained. After drying the sol-gel spheres under alcohol supercritical drying conditions, aerogel spheres with a bulk density of 0.8-1.0 g/cm3were prepared, and by subsequently pyrolyzing them, CA spheres with surface areas of 250-650 m2/g were obtained. The resultant CA spheres could be used as the electrode materials of supercapacitors. The specific capacitance of the CA spheres was as high as 215 F/g, and the equivalent series resistance at 48 Hz was about 1 Ω. 相似文献