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991.
Hypoeutectic Sn-Zn may be a better choice than the eutectic Sn-9Zn as a lead-free solder. We checked the non-equilibrium melting behaviors of a series of Sn-Zn alloys (2.5-9 wt.% Zn) by differential thermal analysis, and found that at a heating rate of 5 °C/min, Sn-6.5Zn behaves the same way as the eutectic Sn-9Zn in melting. Dipping and spreading tests were carried out to characterize the wettability of Sn-Zn alloys on Cu. Both tests indicated that Sn-6.5Zn has significantly better wettability to Cu than Sn-9Zn does. The reaction layers formed during the spreading tests were examined. For all samples with 2.5-9 wt.% Zn, two reaction layers are formed at the interface, a thick and flat Cu5Zn8 layer adjacent to Cu and a thin and irregular Cu-Zn-Sn layer adjacent to the alloy. The total thickness of the reaction layers between the alloy and Cu was found to remarkably decrease with decrease of the Zn concentration. 相似文献
992.
He Yueying Zhang Yan Gu Chunhua Dai Weifeng Lang Meidong 《Journal of materials science. Materials in medicine》2010,21(2):567-574
Block copolymers of Methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) bearing ketone groups (MPEG-b-P(CL-co-OPD)) are synthesized and evaluated for its potential to form micelles containing doxorubicin (DOX), a representative anticancer
drug, by using an in vitro method based on membrane dialysis to emulate drug release in vivo. The 1H NMR spectra of the prepared block copolymers in D2O solution exhibit peaks due to the P(OPD-co-CL) in decreased intensity, indicates that the polymers form micelle particles containing the hydrophilic segments in their
external parts. The CMC of the copolymer decrease with an increase in the content of ketone groups in the hydrophobic chain.
Drug-free and drug-loaded solutions of structurally related copolymers indicate the polymeric aggregation into micellar-type
constructs. The size of the drug-loaded micelles is found to be larger than corresponding drug-free micelles. The release
rate of MPEG-b-PCL micelles is faster than MPEG-b-P(OPD-co-CL) micelles in pH 7.4 buffered solution and they have a similar release rate in pH 5.0 buffered solution. This study, therefore,
confirms the potential of a novel functional block copolymers, Methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) bearing ketone Groups, for the formation of polymeric micelles for drug delivery. 相似文献
993.
Shen Lang Poudel Nirakar Gibson George N. Hou Bingya Chen Jihan Shi Haotian Guignon Ernest Page William D. Pilar Arturo Cronin Stephen B. 《Nano Research》2018,11(4):2310-2314
Nano Research - We report plasmon resonant excitation of hot electrons in a photodetector based on a metal/oxide/metal (Au/Al2O3/graphene) heterostructure. In this device, hot electrons, excited... 相似文献
994.
本文用ASAP2000吸附仪测定了吸附性能优异的沥青基高比表面积新型活性碳(PHAC)的BET比表面积、用BJH和DRS法分析了其孔隙结构参数,用XPS测定了PHAC的表面元素组成及含氧官能团,对PHAC的表面形态结构进行了SEM和TEM观察。研究表明:PHAC具有高度发达且均匀的微孔结构,其表面含有一定量的C-O-C、C-OH、C=O、O=C-O等多种类型的含氧官能团。 相似文献
995.
稻壳灰(RHA)是稻壳控制燃烧产生的高活性火山灰材料,广泛用作生产高性能混凝土的矿物掺合料。稻壳灰的加入对水泥水化有着复杂的影响,目前的模型并不能解释所有这些复杂的影响。通过考虑稻壳灰对复合胶凝体系的稀释效应、化学效应、稻壳灰多孔结构对于水的吸收和释放等因素,建立了RHA-水泥胶凝体系的水化动力学模型,并以水灰比、环境温度,RHA颗粒细度和掺量等为变化参数,通过模型计算与试验结果相比较,证明所建立的模型可较好地模拟含RHA-水泥胶凝体系的水化进程,可用于预测RHA-水泥胶凝体系的水化程度随龄期的变化规律。结果表明,RHA-水泥胶凝体系的水化程度与水灰比、环境温度和比表面积是成正比的关系。研究可为稻壳灰在水泥中的应用提供依据,同时达到提高水泥的经济性和节约资源的目的。 相似文献
996.
Eric C. O’Quinn Jessica L. Bishop Roman Sherrod Joerg Neuefeind Sagrario M. Montemayor Antonio F. Fuentes Maik Lang 《Journal of Materials Science》2018,53(19):13400-13410
Materials that adopt the pyrochlore (A2B2O7) structure show promise for use in a variety of energy-related applications such as immobilization of actinide-rich nuclear waste and oxide fuel cells. Mechanochemical synthesis, a combination of milling and high-temperature treatment, has been successfully applied to fabricate many different pyrochlore compositions. High-resolution neutron total scattering experiments were used to gain fundamental insight into the structural details of milled Er2Ti2O7 pyrochlore and the subsequent evolution under high-temperature treatment. The milling process creates a highly disordered structure in which local atomic ordering is present that is significantly different than the observed long-range behavior. Thermal annealing leads to a complex defect recovery scheme with a gradual local rearrangement from a weberite-type atomic ordering to a pyrochlore phase independent of the sharp long-range crystallization process. Annealing of the milled sample up to 1200 °C does not reproduce the local structure of the same pyrochlore sample prepared by solid-state synthesis. This indicates that despite both samples possessing identical long-range structures, local defects induced by the milling process persist to very high temperatures. These findings provide a direct insight into the mechanochemical synthesis of pyrochlore oxides and help to better elucidate the structural properties of highly disordered complex oxides under extreme conditions from the local atomic arrangement to the macroscale. 相似文献
997.
Mg–Air Batteries: Atomic Fe–Nx Coupled Open‐Mesoporous Carbon Nanofibers for Efficient and Bioadaptable Oxygen Electrode in Mg–Air Batteries (Adv. Mater. 40/2018) 下载免费PDF全文
998.
Kazuhiko Misawa Isao Matsuda Naoyuki T. Hashimoto Roy Lang 《Journal of Modern Optics》2013,60(16-18):2685-2692
Abstract A new optical telecommunication method combining time and frequency domain multiplexing is proposed using phase-controlled femtosecond pulses. Each pulse in a pulse train can be used as a data packet with data bits in the frequency domain. We call the new principle ‘wave packet engineering’, which adjusts the amplitude and phase of the wave function in device materials arbitrarily by controlling the spectral phase of femtosecond pulses. The optical phase-to-amplitude converter is demonstrated with organic dye molecules, in which the phase information in the phase-modulated pulses can be demodulated into the luminescence intensity. The luminescence intensity from cyanine dye molecules is observed to be chirp dependent, and is explained quantum mechanically in terms of coherent population transfer. The design principle of the device using semiconductor coupled quantum nanostructures is also discussed in terms of wave packet engineering. 相似文献
999.
1000.
在氟气中引入惰性气体——氮气,与三种不同结构的沥青(中间相炭微球、中间相沥青和各向同性沥青)在旋转式反应釜中进行反应,制得三种氟化沥青。研究了所制样品的表面能、与水的接触角、耐酸碱稳定性和热失重性能。结果发现:三种氟化沥青的性质既有共性又有差异。比如,均具有极低的表面能,耐酸碱性稳定;但是氟化反应速度不同,受热行为不同,表现在最大失重速率各有特点。从原料沥青的分子结构、氟化沥青分子结构及分子之间的相互作用和排列的角度分析,认为氟化沥青的分子结构和分子量大小分布是导致其物理性质不同的主要原因,原料沥青的组成和结构则是造成氟化反应速率差异的根本。 相似文献