全文获取类型
收费全文 | 26387篇 |
免费 | 3090篇 |
国内免费 | 1835篇 |
专业分类
电工技术 | 4471篇 |
综合类 | 1584篇 |
化学工业 | 7260篇 |
金属工艺 | 1923篇 |
机械仪表 | 992篇 |
建筑科学 | 871篇 |
矿业工程 | 532篇 |
能源动力 | 984篇 |
轻工业 | 2465篇 |
水利工程 | 261篇 |
石油天然气 | 506篇 |
武器工业 | 119篇 |
无线电 | 2438篇 |
一般工业技术 | 4020篇 |
冶金工业 | 980篇 |
原子能技术 | 1288篇 |
自动化技术 | 618篇 |
出版年
2024年 | 94篇 |
2023年 | 450篇 |
2022年 | 752篇 |
2021年 | 976篇 |
2020年 | 963篇 |
2019年 | 919篇 |
2018年 | 875篇 |
2017年 | 1065篇 |
2016年 | 1036篇 |
2015年 | 1023篇 |
2014年 | 1433篇 |
2013年 | 1538篇 |
2012年 | 1857篇 |
2011年 | 1977篇 |
2010年 | 1361篇 |
2009年 | 1492篇 |
2008年 | 1325篇 |
2007年 | 1812篇 |
2006年 | 1624篇 |
2005年 | 1380篇 |
2004年 | 1207篇 |
2003年 | 1021篇 |
2002年 | 866篇 |
2001年 | 765篇 |
2000年 | 630篇 |
1999年 | 486篇 |
1998年 | 368篇 |
1997年 | 299篇 |
1996年 | 279篇 |
1995年 | 238篇 |
1994年 | 235篇 |
1993年 | 166篇 |
1992年 | 169篇 |
1991年 | 126篇 |
1990年 | 98篇 |
1989年 | 68篇 |
1988年 | 76篇 |
1987年 | 51篇 |
1986年 | 56篇 |
1985年 | 32篇 |
1984年 | 29篇 |
1983年 | 14篇 |
1982年 | 17篇 |
1981年 | 12篇 |
1980年 | 8篇 |
1978年 | 6篇 |
1976年 | 4篇 |
1974年 | 5篇 |
1959年 | 6篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The bulk modification of SBS rubber with maleic anhydride in a mixing chamber of a Haake rheomixer was studied. The effect of temperature, maleic anhydride, and benzoyl peroxide concentrations on the grafting efficiency was evaluated. High grafting efficiency was achieved when the ratio of peroxide and maleic anhydride concentration was high. On the other hand, on this condition high insoluble fraction was generated. The addition of a diamine, 4,4′‐diaminediphenylmethane to the reaction mixture minimizes the amount of insoluble polymer. However, the grafted MAH content also decreases. The graft copolymer was characterized by infrared spectroscopy and the grafting extension was determined by titration. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2953–2960, 2002; DOI 10.1002/app.10355 相似文献
102.
Xiang Lu S. Sundar Kumar Iyer Jin Lee Brian Doyle Zhineng Fan Paul K. Chu Chenming Hu Nathan W. Cheung 《Journal of Electronic Materials》1998,27(9):1059-1066
We have demonstrated feasibility to form silicon-on-insulator (SOI) substrates using plasma immersion ion implantation (PIII)
for both separation by implantation of oxygen and ion-cut. This high throughput technique can substantially lower the high
cost of SOI substrates due to the simpler implanter design as well as ease of maintenance. For separation by plasma implantation
of oxygen wafers, secondary ion mass spectrometry analysis and cross-sectional transmission electron micrographs show continuous
buried oxide formation under a single-crystal silicon overlayer with sharp Si/SiO2 interfaces after oxygen plasma implantation and high-temperature (1300°C) annealing. Ion-cut SOI wafer fabrication technique
is implemented for the first time using PIII. The hydrogen plasma can be optimized so that only one ion species is dominant
in concentration and there are minimal effects by other residual ions on the ion-cut process. The physical mechanism of hydrogen
induced silicon surface layer cleavage has been investigated. An ideal gas law model of the microcavity internal pressure
combined with a two-dimensional finite element fracture mechanics model is used to approximate the fracture driving force
which is sufficient to overcome the silicon fracture resistance. 相似文献
103.
104.
H. de Groot 《Materialwissenschaft und Werkstofftechnik》2007,38(12):965-968
Ischemia‐reperfusion injury of the bone occurs due to traumatic and non‐traumatic alterations affecting blood supply to the bone. It is likely to occur also upon insertion of an implant. Ischemia‐reperfusion injury of the bone has been studied by interruption of blood supply in situ, in limb replantation/transplantation models, in revascularized bone grafts and non‐vascularized bone fragments, as well as in isolated cultured cells. All cells of the bone are affected, including osteoblasts, osteocytes, osteoclasts, chondrocytes, and bone marrow cells. Critical ischemia times for induction of bone cell death, either in the ischemic period or following reperfusion, are in the range of 3 to 7 h. These critical ischemia times are significantly increased by decreasing the temperature from 37 °C to 0–4 °C. Anoxia is the most likely trigger of cell injury in the ischemic phase. In the reperfusion phase, reactive oxygen species are decisively involved in the injurious process. In general, however, the available information on the mechanism of ischemia‐reperfusion injury of the bone is relatively sparse. On the other hand, there are clear similarities to the mechanisms of ischemia‐reperfusion injury known from other organs, and there is a clear potential for protection against ischemia‐reperfusion injury of the bone. 相似文献
105.
Bob Eisenberg 《Journal of Computational Electronics》2002,1(3):331-333
Ion channels are proteins with a hole down their middle important in a wide range of biological functions yet simple enough to be analyzed as devices in the engineering tradition. 相似文献
106.
黄埔发电厂#6发电机转冷水铜离子含量超标,通过对缺陷原因进行分析,针对二级水封的特性对溢出的转冷水进行回收并利用化学凝结水处理去除溶出的铜离子,通过控制转冷水的pH值最终减缓铜管的腐蚀. 相似文献
107.
Ying Bai Yanfeng Yin Na Liu Bingkun Guo Hongjun Shi Jianyong Liu Zhaoxiang Wang Liquan Chen 《Journal of power sources》2007
As the continuance of our series study on LiCoO2 surface modification, the complicated traditional surface coating method is replaced with simple addition of amorphous YPO4 and Al2O3 in commercial LiCoO2 or in commercial electrolyte based on our understanding to the improvement mechanism of surface modification. Comprehensive studies by X-ray photoelectron spectroscopy (XPS), gas chromatography and mass spectroscopy (GC–MS), inductively coupled plasma (ICP) and Fourier transformed infrared (FTIR) indicate that the products of spontaneous reaction between the additive and the LiPF6 based electrolyte are responsible for the performance improvements. 相似文献
108.
A methodology for evaluating the reactivity of titanium with mould materials during casting has been developed. Microhardness
profiles and analysis of oxygen contamination have provided an index for evaluation of the reactivity of titanium. Microhardness
profile delineates two distinct regions, one of which is characterised by a low value of hardness which is invariant with
distance. The reaction products are uniformly distributed in the metal in this region. The second is characterised by a sharp
decrease in microhardness with distance from the metal-mould interface. It represents a diffusion zone for solutes that dissolve
into titanium from the mould. The qualitative profiles for contaminants determined by scanning electron probe microanalyser
and secondary ion mass spectroscopy in the as-cast titanium were found to be similar to that of microhardness, implying that
microhardness can be considered as an index of the contamination resulting from metal-mould reaction. 相似文献
109.
小型密闭压力容器测试(MCPVT)法是安全工程领域中近几年发展起来的、评价有机过氧化物及自反应物质受热分解反应激烈程度的新方法。pmax是MCPVT方法中用来表征自反应物质受热分解反应激烈程度的物理量之一。文中通过大量实验,研究了样品容器容积V、升温速率R及样品质量M对pmax重复性误差的影响,研究了一系列典型的有机过氧化物和自反应物质在标准实验条件下pmax重复性误差。结果表明,小型密闭压力容器测试系统重复性好,测试结果可靠,从而为MCPVT法最终成为国际上评价自反应物质受热分解反应激烈程度标准方法奠定了基础。 相似文献
110.
双螺杆反应挤出模型的研究 总被引:5,自引:0,他引:5
详细研究了双螺杆中反应挤出聚合物的动力学模型、流动模型和传热模型。通过实验得到了双螺杆反应器中聚合物的停留时间分布及平均停留时间。 相似文献