全文获取类型
收费全文 | 12514篇 |
免费 | 1267篇 |
国内免费 | 441篇 |
专业分类
电工技术 | 244篇 |
综合类 | 714篇 |
化学工业 | 5797篇 |
金属工艺 | 632篇 |
机械仪表 | 137篇 |
建筑科学 | 240篇 |
矿业工程 | 496篇 |
能源动力 | 324篇 |
轻工业 | 2375篇 |
水利工程 | 37篇 |
石油天然气 | 498篇 |
武器工业 | 13篇 |
无线电 | 343篇 |
一般工业技术 | 1321篇 |
冶金工业 | 706篇 |
原子能技术 | 300篇 |
自动化技术 | 45篇 |
出版年
2024年 | 58篇 |
2023年 | 221篇 |
2022年 | 372篇 |
2021年 | 439篇 |
2020年 | 485篇 |
2019年 | 418篇 |
2018年 | 384篇 |
2017年 | 465篇 |
2016年 | 490篇 |
2015年 | 435篇 |
2014年 | 673篇 |
2013年 | 866篇 |
2012年 | 929篇 |
2011年 | 947篇 |
2010年 | 645篇 |
2009年 | 660篇 |
2008年 | 568篇 |
2007年 | 715篇 |
2006年 | 697篇 |
2005年 | 593篇 |
2004年 | 510篇 |
2003年 | 415篇 |
2002年 | 391篇 |
2001年 | 337篇 |
2000年 | 305篇 |
1999年 | 244篇 |
1998年 | 182篇 |
1997年 | 143篇 |
1996年 | 113篇 |
1995年 | 90篇 |
1994年 | 71篇 |
1993年 | 70篇 |
1992年 | 62篇 |
1991年 | 48篇 |
1990年 | 33篇 |
1989年 | 24篇 |
1988年 | 20篇 |
1987年 | 9篇 |
1986年 | 13篇 |
1985年 | 21篇 |
1984年 | 14篇 |
1983年 | 11篇 |
1982年 | 10篇 |
1981年 | 2篇 |
1980年 | 10篇 |
1979年 | 4篇 |
1976年 | 2篇 |
1961年 | 1篇 |
1959年 | 4篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
以国内某焦化企业场地多环芳烃污染土壤为研究对象,研究了过硫酸钠作为氧化剂时,硫酸亚铁或次氯酸钠助剂的使用对修复效率的影响,同时通过对比阐述了硫酸亚铁及次氯酸钠在过硫酸钠氧化体系中的不同作用。结果表明:微量硫酸亚铁对过硫酸钠氧化土壤中多环芳烃起到催化作用,可显著提高多环芳烃去除效率;次氯酸钠可与过硫酸钠协同使用,达到共氧化的目的。 相似文献
63.
The micellar properties of aqueous binary mixed solutions for two systems consisting of sodium cholate (NaC)-octaoxyethylene
glycol mono n-decyl ether (C10E8) and sodium glycocholate (NaGC)-C10E8 have been studied on the basis of surface tensions, polarity of the micelle interior and the mean aggregation number. Application
of two theoretical treatments, based on regular solution and excess thermodynamic quantities for critical micellar concentration
(CMC) data from surface tension curves of two mixed systems showed that the mole fraction of each bile salt in the mixed micelles
near the CMC is lower than that of the corresponding prepared mole fraction in the mixed solution. The polarity of the interior
suggested that the hydrophobicity of intramicelles increased with the increase of the mole fraction of bile salt in the mixed
solution and that the mixed micelles become dramatically more hydrophobic at a mole fraction of 0.68 for NaGC−C10E8 system and 0.75 for NaC−C10E8 system, respectively. This implies that the micelles become richer in the bile salt molecules and the tendency appears strongly
for NaGC−C10E8 system due to the strong cohesion between the conjugated glycines in the NaGC molecules. The decrease of aggregation number
with the increase of the mole fraction of bile salts shows that the micelles approach those of the single system of each bile
salt. This supports the previously mentioned facts. 相似文献
64.
Mirjam Theelen Vincent Hans Nicolas Barreau Henk Steijvers Zeger Vroon Miro Zeman 《Progress in Photovoltaics: Research and Applications》2015,23(5):537-545
Unencapsulated CIGS solar cells with high and low contents of sodium (Na) and potassium (K) were simultaneously exposed to damp heat and illumination. The solar cells with a high alkali (Na, K) content exhibited higher initial conversion efficiencies, but degraded severely within 100 h, while the alkali poor samples kept relatively stable performance under damp heat and illumination. The degradation of the samples with a high alkali content resulted in the formation of sodium rich spots on the top ZnO:Al surface of the samples. This is likely caused by light‐induced Na+ migration via the grain boundaries in the absorber to the depletion region, where the Na+ accumulated. This allowed subsequent Na+ transport through the depletion region due to the lowering of the internal electric field caused both by the Na+ accumulation and illumination. The migration resulted in the formation of shunt paths, which reduced the shunt resistance and open circuit voltage. Furthermore, ingression of water into the ZnO:Al is expected to be responsible for a slow but steady increase in series resistance for both high and low alkali solar cells. Additionally, sodium migration led to a severe increase of the series resistance in case of alkali rich samples. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
65.
66.
Xu Han Tianyu Qiu Meiwei Li Jing Du Wensi Tang Sihang Cheng Ruiqi Yao Yingqi Li Huaqiao Tan Yonghui Wang Yangguang Li 《Advanced functional materials》2023,33(43):2303102
Pre-intercalating ions between V O layers is considered to be an effective strategy to modulate the interlayer spacing of 2D vanadium oxides. However, the rigid pre-intercalated ions hardly keep stable during repeated charging/discharging process and their sizes limit the extent of interlayer spacing expansion, which inevitably lead to poor rate capability and cycle stability. In this work, aliphatic diamines are adopted as pre-intercalated guests to elastically modulate the interlayer spacing of V O layers by tuning the chain length of the organic diamine molecules. Benefiting from the strong interaction between the terminal doubly protonated amine and the polar negative oxygen bridge of the V O layers, the aliphatic diamine molecules can act as a structural stabilizer between the layers and boost fast Na ion diffusion (10−8 to 10−10 cm2 s−1). The sodium ion battery based on the first synthesized 1,6-hexanediamine pre-intercalated vanadium oxide supported on nickel foam hybrid cathode achieves a large specific capacity of 597 mAh g−1 at 0.09 A g−1, as well as superior rate performance and cycling stability. This work provides a strategy to elastically modulate 2D layered materials with tunable interlayer spacing for batteries based on large-size-ions. 相似文献
67.
Tianbing Song Hai Chen Zhi Li Qunjie Xu Haimei Liu Yonggang Wang Yongyao Xia 《Advanced functional materials》2019,29(22)
With the increasing demand for low cost, long lifetime, high energy density storage systems, an extensive amount of effort has recently been focused on the development of sodium‐ion batteries (SIBs), and a variety of cathode materials have been discovered. However, looking for the most suitable anode material for practical application is a major challenge for SIBs. Herein, a high capacity sulfur‐doped black phosphorus‐TiO2 (TiO2‐BP‐S) anode material for SIBs is first synthesized by a feasible and large‐scale high‐energy ball‐milling approach, and its stability in air exposure is investigated through X‐ray photoelectron spectroscopy. The morphology of TiO2‐BP‐S is characterized using transmission electron microscopy, indicating that the TiO2 nanoparticles produce P? Ti bonds with BP. The TiO2‐BP‐S composite with P? S and P? Ti bonds exhibits excellent stability in air and the superior electrochemical performance. For example, the discharge specific capacity is up to 490 mA h g?1 after 100 cycles at 50 mA g?1, and it remains at 290 mA h g?1 after 600 cycles at 500 mA g?1. Meanwhile, the scientific insight that the formation of stable P? S and P? Ti bonds can provide a guide for the practical large‐scale application of SIBs in other titanium base and black phosphorus materials is looked forward. 相似文献
68.
69.
70.