全文获取类型
收费全文 | 72598篇 |
免费 | 4634篇 |
国内免费 | 1182篇 |
专业分类
电工技术 | 1839篇 |
技术理论 | 3篇 |
综合类 | 1691篇 |
化学工业 | 14175篇 |
金属工艺 | 2305篇 |
机械仪表 | 2608篇 |
建筑科学 | 3517篇 |
矿业工程 | 1051篇 |
能源动力 | 2362篇 |
轻工业 | 9255篇 |
水利工程 | 883篇 |
石油天然气 | 1669篇 |
武器工业 | 164篇 |
无线电 | 5920篇 |
一般工业技术 | 10681篇 |
冶金工业 | 9710篇 |
原子能技术 | 576篇 |
自动化技术 | 10005篇 |
出版年
2024年 | 176篇 |
2023年 | 748篇 |
2022年 | 1386篇 |
2021年 | 2438篇 |
2020年 | 1766篇 |
2019年 | 1790篇 |
2018年 | 2255篇 |
2017年 | 2351篇 |
2016年 | 2386篇 |
2015年 | 2135篇 |
2014年 | 2978篇 |
2013年 | 4558篇 |
2012年 | 4303篇 |
2011年 | 4674篇 |
2010年 | 3662篇 |
2009年 | 3554篇 |
2008年 | 3414篇 |
2007年 | 3127篇 |
2006年 | 2748篇 |
2005年 | 2497篇 |
2004年 | 2142篇 |
2003年 | 1925篇 |
2002年 | 1929篇 |
2001年 | 1564篇 |
2000年 | 1367篇 |
1999年 | 1377篇 |
1998年 | 3279篇 |
1997年 | 2214篇 |
1996年 | 1665篇 |
1995年 | 1159篇 |
1994年 | 971篇 |
1993年 | 939篇 |
1992年 | 472篇 |
1991年 | 483篇 |
1990年 | 357篇 |
1989年 | 325篇 |
1988年 | 344篇 |
1987年 | 253篇 |
1986年 | 254篇 |
1985年 | 258篇 |
1984年 | 194篇 |
1983年 | 142篇 |
1982年 | 176篇 |
1981年 | 184篇 |
1980年 | 174篇 |
1979年 | 133篇 |
1978年 | 105篇 |
1977年 | 192篇 |
1976年 | 303篇 |
1975年 | 104篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Wireless Networks - Geolocation is important for many emerging applications such as disaster management and recommendation system. In this paper, we propose a multilayer recognition model (MRM) to... 相似文献
2.
Bernette Maria Oosterlaken Heiner Friedrich Gijsbertus de With 《Microscopy research and technique》2022,85(1):412-417
Transmission electron microscopy (TEM) is an important analysis technique to visualize (bio)macromolecules and their assemblies, including collagen fibers. Many protocols for TEM sample preparation of collagen involve one or more washing steps to remove excess salts from the dispersion that could hamper analysis when dried on a TEM grid. Such protocols are not standardized and washing times as well as washing solvents vary from procedure to procedure, with each research group typically having their own protocol. Here, we investigate the influence of washing with water, ethanol, but also methanol and 2-propanol, for both mineralized and unmineralized collagen samples via a protocol based on centrifugation. Washing with water maintains the hydrated collagen structure and the characteristic banding pattern can be clearly observed. Conversely, washing with ethanol results in dehydration of the fibrils, often leading to aggregation of the fibers and a less obvious banding pattern, already within 1 min of ethanol exposure. As we show, this process is fully reversible. Similar observations were made for methanol and propanol. Based on these results, a standardized washing protocol for collagenous samples is proposed. 相似文献
3.
4.
5.
6.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical... 相似文献
7.
KH550, KH560, CTAB, and F127 were adopted to modify silicon (Si) to improve the dispersity and stability of Si in the polyacrylonitrile/dimethyl sulfoxide (PAN/DMSO) polymer solutions. The influence of surfactants on rheological behaviors of PAN/DMSO/Si blending polymer solutions was investigated by an advanced solution and melt rotation rheometer. The homogeneity and stability were also studied. The results showed that the surfactants could change the viscosity dependence of blending polymer solutions on shear rate, temperature and storage time by increase the steric hindrance of Si. Among the four solutions, PAN/DMSO/Si blending polymer solution with F127 exhibited the lowest viscosity, activation energy and the smallest structural viscosity index and exhibited the trend close to the Newtonian fluids. Moreover, PAN/DMSO/Si blending polymer solution with F127 exhibited the best dispersity and stability, indicating its best physical properties and machinability. 相似文献
8.
Gabriela Pitolli Lyra Valdemir Santos Eliria Maria de Jesus Agnolon Pallone Ruth Herta Goldschmidt Aliaga Kiminami Bruno Carlos De Santis João Adriano Rossignolo 《International Journal of Applied Ceramic Technology》2021,18(3):705-715
This work aimed to examine the performance of the hybrid sintering of clay ceramic in a microwave furnace, compared to the sintering process in a conventional furnace. The raw materials were subjected to X-ray fluorescence, loss on ignition (LOI), X-ray diffraction, particle size distribution, real specific mass, and thermogravimetric analyses. The red clay ceramic mass was prepared, extruded, pre-sintered in a conventional furnace at 600°C/60 min, and sintered at temperatures between 700 °C and 1100 °C. The sintering conventional (resistive oven) was carried out for 60 min with a heating rate of 10°C/min. In the microwave furnace, the sintering times were 5, 10, and 15 min, with a heating rate of 50°C/min, with a sintering chamber coated with silicon carbide (susceptor). The sintered specimens were characterized according to linear shrinkage, water absorption, apparent porosity, apparent specific mass, X-ray diffraction, Raman spectroscopy analysis, spectroscopy analysis in the ultraviolet and visible regions, microhardness, and scanning electron microscopy. The results showed that microwave sintering promoted an increase in the microhardness and apparent specific mass, and reduction in water absorption and apparent porosity values, due to greater densification in the microstructure. The best results occurred for specimens sintered at 1100°C. 相似文献
9.
基于冲击破碎技术对截割滚筒结构进行了优化设计,将其设计为振动形式.利用MATLAB软件对截割滚筒中关键的偏心锤结构进行了优化设计.利用COMSOL软件对行星齿轮结构固有频率进行分析,发现工作频率远小于固有频率,不会发生共振问题.将设计的新型截割滚筒应用到煤矿工程实践中,采煤效率显著提升. 相似文献
10.
Angelika Varga Zoltn Mszr Mikls Sivad Tímea Bcskai Bence Vgh va Kkai Istvn Nagy Pter Szücs 《International journal of molecular sciences》2021,22(5)
The phosphorylation of serine 10 in histone 3 (p-S10H3) has recently been demonstrated to participate in spinal nociceptive processing. However, superficial dorsal horn (SDH) neurons involved in p-S10H3-mediated nociception have not been fully characterized. In the present work, we combined immunohistochemistry, in situ hybridization with the retrograde labeling of projection neurons to reveal the subset of dorsal horn neurons presenting an elevated level of p-S10H3 in response to noxious heat (60 °C), causing burn injury. Projection neurons only represented a small percentage (5%) of p-S10H3-positive cells, while the greater part of them belonged to excitatory SDH interneurons. The combined immunolabeling of p-S10H3 with markers of already established interneuronal classes of the SDH revealed that the largest subset of neurons with burn injury-induced p-S10H3 expression was dynorphin immunopositive in mice. Furthermore, the majority of p-S10H3-expressing dynorphinergic neurons proved to be excitatory, as they lacked Pax-2 and showed Lmx1b-immunopositivity. Thus, we showed that neurochemically heterogeneous SDH neurons exhibit the upregulation of p-S10H3 shortly after noxious heat-induced burn injury and consequential tissue damage, and that a dedicated subset of excitatory dynorphinergic neurons is likely a key player in the development of central sensitization via the p-S10H3 mediated pathway. 相似文献