全文获取类型
收费全文 | 7687篇 |
免费 | 580篇 |
国内免费 | 185篇 |
专业分类
电工技术 | 58篇 |
综合类 | 247篇 |
化学工业 | 1378篇 |
金属工艺 | 1160篇 |
机械仪表 | 148篇 |
建筑科学 | 397篇 |
矿业工程 | 456篇 |
能源动力 | 247篇 |
轻工业 | 459篇 |
水利工程 | 108篇 |
石油天然气 | 78篇 |
武器工业 | 10篇 |
无线电 | 226篇 |
一般工业技术 | 1242篇 |
冶金工业 | 2009篇 |
原子能技术 | 132篇 |
自动化技术 | 97篇 |
出版年
2024年 | 3篇 |
2023年 | 318篇 |
2022年 | 374篇 |
2021年 | 424篇 |
2020年 | 420篇 |
2019年 | 354篇 |
2018年 | 363篇 |
2017年 | 201篇 |
2016年 | 206篇 |
2015年 | 177篇 |
2014年 | 290篇 |
2013年 | 550篇 |
2012年 | 310篇 |
2011年 | 470篇 |
2010年 | 281篇 |
2009年 | 320篇 |
2008年 | 283篇 |
2007年 | 330篇 |
2006年 | 304篇 |
2005年 | 262篇 |
2004年 | 228篇 |
2003年 | 236篇 |
2002年 | 174篇 |
2001年 | 146篇 |
2000年 | 130篇 |
1999年 | 234篇 |
1998年 | 172篇 |
1997年 | 150篇 |
1996年 | 112篇 |
1995年 | 97篇 |
1994年 | 84篇 |
1993年 | 87篇 |
1992年 | 80篇 |
1991年 | 69篇 |
1990年 | 52篇 |
1989年 | 34篇 |
1988年 | 15篇 |
1987年 | 19篇 |
1986年 | 12篇 |
1985年 | 29篇 |
1984年 | 20篇 |
1983年 | 15篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 7篇 |
排序方式: 共有8452条查询结果,搜索用时 15 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(49):21231-21240
To explore the feasibility and related mechanism of MFC biosensor for wastewater detection under the action of combined heavy metals. Cyclic voltammetry (CV) and scanning electrochemical impedance spectroscopy (EIS) were used to explore the related bioelectrochemical process. The response of the reactor to single/combined heavy metals, low/high heavy metal concentrations, and the differences in ohmic resistance (Rs) and charge transfer resistance (Rct) were investigated using Ni as the core heavy metal and the combined action of Cd, Cu and Zn. The results indicated that there was a linear relationship between the concentration and output voltage of the MFC biosensor under the action of combined heavy metals (R2 = 0.8803–0.973). However, the internal resistance (Rint) of the MFC biosensor under the action of single heavy metal was far less than that of the combined heavy metal group, and the power density (19.849 W m?3) was 4 times that of the combined heavy metal group (3.109–4.589 W m?3). The Rs of the biosensors in the combined heavy metal group were 0.868Ω and 0.860, which were higher than 0.768Ω of the single heavy metal sensor. With the increase of the concentration of heavy metals in the influent, the increase of Rct was more obvious in the combined group, while the Rs in the single group significantly increased (P < 0.05). The results imply that it is possible for MFC biosensors to be used in the detection of actual water polluted by various heavy metals, but the biosensor performance is mainly limited by Rct, which needs to be further improved. 相似文献
2.
树枝状过渡金属催化剂是在树枝状大分子上负载上过渡金属活性中心,因此,此类催化剂既具有树枝状大分子特有的艺术结构,同时还具有过渡金属配合物的功能化性能,使其两者能够协同发挥作用,兼具均相和非均相催化体系的特点,在催化烯烃聚合方面具有较高的催化活性和良好的催化稳定性,近年来备受关注,催化乙烯聚合就是其中的研究热点之一。本文按其过渡金属活性中心进行分类,综述了近年来国内外树枝状过渡金属催化剂在这乙烯聚合方面的进展,阐述了多种树枝状效应产生的原因,并且对乙烯聚合用树枝状过渡金属催化剂的发展前景进行了展望。 相似文献
3.
针对Calpuff模型、主成分分析法缺少对气候条件和特定条件下的空间污染特征分析导致扩散模拟结果不精准的问题,提出了危险废物填埋土壤中的重金属污染扩散特征分析方法。确定污染区域,分析该地区的风速风向、温度。通过分析各地区重金属污染分布情况,计算各区域元素的平均污染指数,建立扩散模型。根据这一模型求得采样点与污染源之间的距离,并以此距离精确计算采样点土壤受污染程度。以富集系数为主要的参数指标测量土壤和沉积物中的重金属含量,按富集系数大小划分污染程度等级,完成重金属污染扩散特征分析。由扩散模拟分析结果可知,该方法与实际全年超标率基本一致,最大误差为0.1%,为危险废物填埋提供了数据支持。 相似文献
4.
为科学推进矿山生态修复,依托传统野外调查工作手段与技术优势,结合室内综合测试与系统分析,开
展长江上游金沙江流域内矿产资源开发引起土壤重金属含量变化相关研究。 以西南地区某矿产集采区为例,探索区
内土壤重金属含量及其随流域迁移规律,分析区内土壤重金属潜在生态风险。 研究表明:该矿产集采区铅锌矿区、磷
矿区土壤样品重金属含量超标存在差异;源于矿产资源开采方式、洗选方式、矿区固体废弃物分布、地表径流强度等
诸多因素影响,区内土壤样品重金属含量从上游到下游的迁移规律呈多种类型。 相关结果既可作为生产矿山生态环
境监测的工作依据,亦可作为闭坑矿山生态保护修复的重要参考。 相似文献
5.
《International Journal of Hydrogen Energy》2022,47(70):30097-30106
In recent years, alternative renewable energy generation sources have been investigated, highlighting the dark fermentation process due to it’s potential to obtain hydrogen-rich gas, which can be used as an energy source. Different trace metals intervene in this biological process. Nickel is one of the most important because it is a component of the [Ni–Fe] hydrogenase enzyme that catalyzes the oxidation of H2 in numerous bacteria. The aim of this study was to evaluate the effect of nickel on biohydrogen production from organic solid waste (OSW). The experimental setup was carried out in batch tests using OSW as the substrate, glucose as a reference compound and the valuation of Ni2+ doses on the operation in a Sequencing Batch Reactor. The results of the batch tests showed that when using glucose as a substrate, 2 mg Ni2+/g VSinoculum generated the highest hydrogen production (774 ± 7.3 mL H2/L/d) and highest yield (55.8 ± 3.4 mL H2/g of glucose), which was 34.4% higher than the control. Testing of different concentrations of nickel using OSW as a carbon source showed that the highest production was obtained without Ni2+ addition since the nickel concentration in the residue was 0.17 ± 0.06 mgNi/gVS; consequently, hydrogen production was not affected by the lack of Ni. The addition of 0.5 mg Ni2+/g VSinoculum decreased acetate and butyrate production and increased caproate production. 相似文献
6.
《水科学与水工程》2022,15(3):237-246
Algae and cyanobacteria are known to be able to remove a variety of pollutants from water, including toxic metal ions. In this study, algal and cyanobacterial species growing in two polluted water bodies were identified, and the Pb(II) removal ability of these isolated species was investigated. Based on microscopic observations, 27 species were identified, and nine species were isolated as pure cultures. Pb(II) bioremediation of five selected species (Anacystis sp., Chlorella sp. 1, Monoraphidium sp., Phormidium sp., and Uronema sp.) was studied in detail. The mean Pb(II) removal abilities varied among these five species: Phormidium sp. > Monoraphidium sp. > Uronema sp. > Chlorella sp. 1 > Anacystis sp. The Pb(II) tolerance of each species was determined based on the live cell percentage and biofilm formation capacity. Within a period of 3 d, Phormidium sp., Monoraphidium sp., and Uronema sp. showed nearly 90% of survival, and all five species demonstrated biofilm formation capacities exceeding 50%. Furthermore, the Pb(II) removal ability of the five species exhibited a strong positive correlation with the live cell percentage and showed a strong negative correlation with the biofilm formation capacity. In conclusion, Phormidium sp., Monoraphidium sp., and Uronema sp. exhibited high tolerances towards Pb(II) and presented high removal abilities. Thus, these species can be identified as potential sorbents for development of suitable adsorption systems to remove Pb(II) from aqueous solutions. 相似文献
7.
8.
《中国稀土学报(英文版)》2022,40(3):467-472
RM3 compounds (R = rare earth metals, M = transition metals) have rarely been studied for gaseous hydrogen storage applications because of unfavorable thermodynamics. In this work, the hydrogen storage properties of a single-phase YFe3 alloy were improved by non-stoichiometric composition and alloying with Sc and Zr. Only the Y1.1–yScyFe3 (y = 0.22, 0.33) alloys consist of a single rhombohedral phase. The Sc substitution for Y leads to the reduction in the unit cell volume of the YFe3 phase, and thus significantly increases the dehydriding equilibrium pressure and decreases the dehydrogenation temperature. The alloy Y0.77Sc0.33Fe3 delivers a decomposition enthalpy change of 33.54 kJ/mol and a lowest dehydrogenation temperature of 135 °C, in comparison with 38.99 kJ/mol and 165 °C for the alloy Y1.1Fe3. The Zr substitution causes a similar thermodynamic destabilization effect, but the composition and microstructure of Y–Zr–Fe alloys need to be further optimized. 相似文献
9.
《中国稀土学报(英文版)》2022,40(1):57-62
High surface area mixed oxide 8.7% NiO-CeO2 nanoparticles (122 m2/g; 6–7 nm) were prepared using a reversed microemulsion method, and were tested for dry methane reforming (DRM). The catalytic activity of these nanoparticles remains stable under the severe conditions of DRM (700 °C), and they show better carbon resistance than conventional NiO-CeO2 catalysts prepared without control of the size. The activity and selectivity of nanoparticles and reference catalyst are similar, but nanoparticles reduce the accumulation of carbon by 63% during the DRM tests, which is a key feature for this reaction. XPS and H2-TPR suggest that the improved carbon resistance of the nanoparticles is due to the better interaction and cooperation between NiO and CeO2 mixed phases. In nanoparticles, the participation of cerium cations in the redox processes taking place during DRM stabilizes cationic species of nickel. On the contrary, the catalyst prepared without control of the size suffers segregation of Ni during DRM reaction, and segregated Ni explains the higher catalytic formation of carbon. 相似文献
10.
《中国稀土学报(英文版)》2022,40(3):457-461
To investigate the influence of the addition of Pr–Ga alloys on magnetic properties and morphology of materials, the hot-deformed PrNd-Fe-B magnets were prepared by the addition of Pr–Ga alloys using a dual-alloys diffusion. The room-temperature coercivity of the hot-deformed PrNd-Fe-B magnets increases substantially from 1.68 to 2.34 T, while the remanence decreases from 1.42 to 1.24 T, by the addition of 5 wt% Pr–Ga alloys. Moreover, the thermal stability of coercivity improves from ?0.46%/oC to ?0.42%/oC. Two types of grain boundary phases (PrNd-rich and PrNd-Ga-rich) are generated at grain boundaries by microstructural analysis, resulting in the decrease of Fe element concentration from more than 60% to about 10% at grain boundaries. The decrease of ferromagnetic element concentration at grain boundaries and the refinement of grain are considered to be the main reasons for the improvement of coercivity and thermal stability. 相似文献