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1.
Zhang Junbao Huang Haojun Yang Changlin Liu Jizhao Fan Yinting Yang Guan 《Wireless Networks》2022,28(3):1301-1312
Wireless Networks - Although centrality is widely used to differentiate the importance of nodes for social-aware routing in mobile opportunistic networks (MONs), it is destination-agnostic since... 相似文献
2.
《Ceramics International》2021,47(24):34810-34819
This study evaluated the effects of different Z-values on the physical, chemical, and biological properties of β-SiAlON ceramics. Increasing the Z-value of the β-Si3N4 solid solution's main phase resulted in the replacement of Si–N bonds with Al–O bonds. The number of columnar crystals decreased, bulk density increased, and porosity decreased, thus transforming the fine-particle microstructure of β-Si3N4 into the columnar structure of β-SiAlON. The compressive strength increased, which facilitated sintering at 1500 °C without sintering auxiliaries. H+ and OH− ions in deionized water broke the covalent bonds on the β-SiAlON surface, thereby forming new Si–OH, Al–OH, and N–H bonds on the β-SiAlON surface and producing SiO44−, AlO2−, and NH4+ groups in the solution. Increasing the soaking time changed the compositions of ionized H+ and OH− ions, thus increasing the pH. MC3T3-E1 cells were cultured on the β-SiAlON surface, and it was observed that the increase in the Z-value of β-SiAlON had no influence on cell adhesion and spreading, but it may slightly suppress cell proliferation at high Z-values. At low Z-values, the low AlO2− concentration helps promote osteogenic differentiation and mineralized nodule formation. Thus, β-SiAlON ceramics possess excellent physical, chemical, and biological properties and are considered excellent bone-repairing materials. 相似文献
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4.
《International Journal of Hydrogen Energy》2020,45(27):13929-13938
Durability and cost of Proton Exchange Membrane fuel cells (PEMFCs) are two major factors delaying their commercialization. Cost is associated with the price of the catalysts, while durability is associated with degradation and poisoning of the catalysts, primarily by CO. This motivated us to develop tungsten-carbide-oxide (WxCyOz) as a new non-carbon based catalyst support for Pt–Ru–based anode PEMFC catalyst. The aim was to improve performance and obtain higher CO tolerance compared to commercial catalysts. The performance of obtained PtRu/WxCyOz catalysts was investigated using cyclic voltammetry, linear scan voltammetry and rotating disk electrode voltammetry. Particular attention was given to the analysis of CO poisoning, to better understand how WxCyOz species can contribute to the CO tolerance of PtRu/WxCyOz. Improved oxidation of COads at low potentials (E < 0.5 V vs. RHE) was ascribed to OH provided by the oxide phase at the interfacial region between the support and the PtRu particles. On the other hand, at high potentials (E > 0.5 V vs. RHE) CO removal proceeds dominantly via OH provided from the oxidized metal sites. The obtained catalyst with the best performance (30% PtRu/WxCyOz) was tested as an anode catalyst in PEM fuel cell. When using synthetic reformate as a fuel in PEMFC, there is a significant power drop of 35.3 % for the commercial 30% PtRu/C catalyst, while for the PtRu/WxCyOz anode catalyst this drop is around 16 %. 相似文献
5.
《International Journal of Hydrogen Energy》2020,45(27):14028-14037
Intermetallic alloy ZrCo is believed to be a good substitution for uranium to store tritium. Nevertheless, disproportionation reaction often happens during the hydriding and dehydriding processes, and hydrogen storage property of ZrCo is therefore degraded. Alloying elements are often used to substitute Zr or Co in ZrCo to restrain disproportionation reaction. However, many experimental results do not agree with each other, and it lacks overall tendency for all transition metal elements. In this work, systematical ab initio calculations are performed to study more than 20 transition alloying elements to substitute Co and Zr in ZrCoH3 to study the anti-disproportionation effects. It is found that substitution of Co by transition metal elements on anti-disproportionation reaction is unconspicuous, and only Ni can enlarge Zr–H bond length and decrease the volume of 8e site, presenting anti-disproportionation effect, which qualitatively agrees with the previous experiments. In contrast, all transition alloying elements considered except Fe, Co, Ni, Ru, Rh, Pd, Os and Ir replacing Zr can both enlarge the length of Zr–H bond and decrease the volume of 8e site, and thus restrain the disproportionation effects. At last, two-dimensional charge density and density of states are calculated to analyze the underlying mico-mechanisms affecting the effects of transition alloying elements on anti-disproportionation reaction. 相似文献
6.
以机械共混法制备亲水性聚对苯二甲酸乙二醇酯(PET)共混材料,并通过接触角测定仪、差示扫描量热仪(DSC)和电子万能材料试验机等对共混材料的亲水性能、热性能和力学性能等进行研究与分析。结果表明,亲水处理剂聚乙二醇(PEG)、聚丙烯酸钠(PAAS)、聚乙烯吡咯烷酮(PVP)均能改善PET的亲水性能,影响PET的结晶性能,但亲水处理剂对PET的力学性能影响较小,其中PET/PEG共混材料的亲水性最优;随着PEG含量的增加,PET/PEG共混材料的亲水性先逐渐增强,当PEG含量高于5 %后,共混材料的亲水性变化很小;且PET的结晶度随着PEG的加入呈现先增大后减小的趋势。 相似文献
7.
Porous mullite ceramics with different crystal shapes of mullite are fabricated by in-situ reaction with middle-grade kyanite as raw material, Al(OH)3, γ-Al2O3, ρ-Al2O3 and α-Al2O3 as alumina sources. Effects of Al2O3 crystal types on morphology evolution and formation mechanisms of mullite, and properties of porous ceramics are investigated. Results show that mullite in the sample with Al(OH)3 mainly shows acicular morphology, because its (001) plane has the minimum interplanar crystal spacing and maximal attachment energy, it grows fast along [001] direction by screw dislocation mechanism. With a successive slowdown in reactivities of Al(OH)3, γ-Al2O3, ρ-Al2O3 and α-Al2O3, the amount and aspect ratio of mullite reduce, its growth mechanism gradually transforms into two-dimensional nucleation. Acicular mullite not only reinforces samples, but makes effective pore sizes smaller, which enable the sample with Al(OH)3 to present low bulk density, high apparent porosity and linear changes, small average pore size and good mechanical strength. 相似文献
8.
以三氟乙酸和二氯甲烷为混合溶剂,采用静电纺丝法制备聚对苯二甲酸丁二酯(PBT)/聚乙烯醇(PVA)复合膜。用旋转粘度计和电导率仪测定溶液的黏度和电导率,用扫描电子显微镜、拉伸和水接触角测试PBT/PVA不同比例对纤维膜的形貌、力学和亲水性能的影响。结果表明,随着PVA比例的增加,混合溶液的黏度逐渐增大,而电导率先增大后减小;当PBT/PVA的比例为90/10时,纳米纤维的平均直径最小,为323 nm,而其纳米纤维膜的力学性能与纯PBT纤维膜相比显著提高,拉伸强度、弹性模量和断裂伸长率分别增加了213%,260%和57%;PVA的加入改善PBT纤维的亲水性,制备出力学性能优异且亲水的PBT/PVA纤维膜。 相似文献
9.
为提高酚醛基纳米活性碳纤维的吸附性能,首先采用乙酸锌、硫酸双催化合成高邻位酚醛树脂,然后配制酚醛/聚乙烯醇缩丁醛(PVB)混合溶液,采用静电纺丝、固化、炭化和活化工艺制备得到柔性高邻位酚醛基纳米活性碳纤维,借助傅里叶变换红外光谱仪、扫描电子显微镜、热重分析仪、比表面积及孔径分析仪对其结构和性能进行测试与分析。结果表明:静电纺丝制备的酚醛初生纤维在溶液固化后,酚环对位取代增加,纤维内发生了分子间交联,但PVB有一定的醇解,使酚醛纤维在炭化过程中低温稳定性下降,而高温残碳率升高,炭化后制备得到多孔碳纤维;活化后得到的高邻位酚醛基纳米活性碳纤维比表面积为1 409 m2/g,其对亚甲基蓝及碘的吸附量分别达到837和2 641 mg/g。 相似文献
10.
为研究短纤维纱条中纤维的排列状态与纱条截面纤维根数分布不匀的关系,采用几何概率方法建立了等分区间内纤维左头端数分布与纱条截面纤维根数的期望之间的数学模型,并定义了表征纱条中纤维排列状态的参数。运用蒙特卡罗方法模拟了纱条截面根数不匀随排列参数变化的关系曲线。结果表明:短纤维纱条截面纤维根数的CV值与纱条中短纤维排列参数呈负线性关系,与纤维长度分布和模拟区间大小的划分无关;且当排列参数接近1时,即纤维左头端数在所划分区间中为固定值时,纱条截面纤维根数不匀最低,而当排列参数趋向于0时,即纤维左头端数在所划分区间中呈泊松分布时则不匀最大。 相似文献