全文获取类型
收费全文 | 1876篇 |
免费 | 116篇 |
国内免费 | 48篇 |
专业分类
电工技术 | 40篇 |
综合类 | 204篇 |
化学工业 | 120篇 |
金属工艺 | 163篇 |
机械仪表 | 187篇 |
建筑科学 | 340篇 |
矿业工程 | 63篇 |
能源动力 | 150篇 |
轻工业 | 163篇 |
水利工程 | 30篇 |
石油天然气 | 50篇 |
武器工业 | 19篇 |
无线电 | 47篇 |
一般工业技术 | 339篇 |
冶金工业 | 62篇 |
原子能技术 | 7篇 |
自动化技术 | 56篇 |
出版年
2024年 | 1篇 |
2023年 | 26篇 |
2022年 | 35篇 |
2021年 | 38篇 |
2020年 | 70篇 |
2019年 | 61篇 |
2018年 | 44篇 |
2017年 | 42篇 |
2016年 | 50篇 |
2015年 | 60篇 |
2014年 | 86篇 |
2013年 | 129篇 |
2012年 | 140篇 |
2011年 | 137篇 |
2010年 | 102篇 |
2009年 | 115篇 |
2008年 | 100篇 |
2007年 | 130篇 |
2006年 | 119篇 |
2005年 | 97篇 |
2004年 | 75篇 |
2003年 | 72篇 |
2002年 | 47篇 |
2001年 | 41篇 |
2000年 | 31篇 |
1999年 | 22篇 |
1998年 | 26篇 |
1997年 | 22篇 |
1996年 | 25篇 |
1995年 | 18篇 |
1994年 | 14篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 4篇 |
1982年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有2040条查询结果,搜索用时 15 毫秒
1.
In the chemical industry large amounts of saline wastewater occur. Its disposal into rivers is a considerable burden to the ecosystem. To strive for a circular economy and enable a viable raw material recycling, energy-efficient concentration processes are requisite. High-pressure reverse osmosis meets this criterion, but its industrial application demands suitable membrane elements that withstand the exceptional operation conditions and provide sufficient performance. Hence, new requirements regarding the design of spiral-wound elements arise. To identify those, specific performance-limiting effects need a better understanding. 相似文献
2.
《International Journal of Hydrogen Energy》2022,47(77):33135-33152
Self-ignition may occur during hydrogen storage and transportation if high-pressure hydrogen is suddenly released into the downstream pipelines, and the presence of obstacles inside the pipeline may affect the ignition mechanism of high-pressure hydrogen. In this work, the effects of multiple obstacles inside the tube on the shock wave propagation and self-ignition during high-pressure hydrogen release are investigated by numerical simulation. The RNG k-ε turbulence model, EDC combustion model, and 19-step detailed hydrogen combustion mechanism are employed. After verifying the reliability of the model with experimental data, the self-ignition process of high-pressure hydrogen release into tubes with obstacles with different locations, spacings, shapes, and blockage ratios is numerically investigated. The results show that obstacles with different locations, spacings, shapes and blockage ratios will generate reflected shock waves with different sizes and propagation trends. The closer the location of obstacles to the burst disk, the smaller the spacing, and the larger the blockage ratio will cause the greater the pressure of the reflected shock wave it produces. Compared with the tubes with rectangular-shaped, semi-circular-shaped and triangular-shaped obstacles, self-ignition is preferred to occur in tube with triangular-shaped obstacles. 相似文献
3.
为避免传统均匀采样方法因忽视曲线重要特征而生成不理想的采样结果,获得给定数量且由特征点和辅助点组成的采样点序列,提出基于特征识别的高质量空间曲线非均匀采样方法.首先使用抛物线插值法得到曲线上所有曲率极大值点和挠率极大值点的近似位置,经筛选后产生特征点,以更好地抓住空间曲线的轮廓特征.然后定义基于弧长、曲率和挠率加权组合的特征函数,并以此自适应地选取曲线上的辅助点.与3种主流采样方法比较的实验结果表明,该方法能够获得更高质量的采样结果且具有更好的实用性,从而进一步改善空间曲线的B样条拟合效果. 相似文献
4.
5.
A size-dependent governing equation is derived to investigate the torsional static behaviors of two-dimensionally functionally graded microtubes based on the modified couple stress theory. The shear modulus is assumed to vary along the tube’s length direction according to an exponential distribute function, and varies along the tube’s radius direction according to a power-law function. A generalized differential quadrature method is developed to determine the rotational angle and shear stresses. Some illustrative examples are given to investigate the effects of applied torques, the length scale parameter and various material compositions on the torsional angle and shear stresses. 相似文献
6.
7.
目的研究感应淬火对曲轴扭转疲劳性能的影响,为曲轴的设计和制造工艺调整提供技术参考。方法开展淬火曲轴和未淬火曲轴的扭转疲劳强度试验,利用升降法得到疲劳试验结果,从试验数据和微观组织等方面开展分析和讨论。结果未经过淬火的曲轴在99.9%存活率下的扭转疲劳极限为967.6N·m,经过感应淬火的曲轴在99.9%存活率下的扭转疲劳极限为1361.2N·m。感应淬火后曲轴的表面形成深度约3.5 mm的淬火层,平均硬度为HV0.5600,金相组织为细针状马氏体。曲轴的失效情况均为连杆颈油孔处开裂。结论 38MnVS6非调质钢曲轴在感应淬火后的扭转疲劳极限提升了约41%,曲轴油孔内壁的加工缺陷是形成裂纹源的主要原因,对曲轴淬火层区域的油孔内壁进行一定的表面处理,可进一步提高曲轴的扭转疲劳强度。 相似文献
8.
9.
《Journal of the European Ceramic Society》2019,39(4):944-951
Three types of hexagonal boron nitride (h-BN) with graphitic crystal structure having different microstructures were subjected to high pressures (HP) and high temperatures (HT), and the kinetics of the phase transitions to the sp3-hybridized phases (w-BN, c-BN) was studied using in situ synchrotron diffraction. The analysis of the phase transformation kinetics revealed the transformation paths and activation energies Ea of the transformation of h-BN to the high-pressure forms of BN for different microstructures of h-BN. Defect-poor h-BN transforms to metastable wurtzitic BN (w-BN) with Ea ≈ 0.3 eV/at. Defect-rich forms of h-BN transform directly to c-BN, but with a higher activation energy. It was observed that the turbostratic disorder in h-BN retards the phase transition as compared to h-BN containing corrugated basal planes and a low degree of turbostracity. The experimental results are discussed in view of the microstructure changes during the HP/HT treatment and compared to available theoretical phase transition models. 相似文献
10.
Yerim Kang Sung Min Cho Dong Kyu Kim 《International Journal of Hydrogen Energy》2021,46(13):9174-9185
A lightweight type 4 vessel with a polyethylene terephthalate (PET) liner is analyzed. The derived heat transfer coefficients between the gas and wall are applied, and a parametric study is performed. An optimized charging strategy is also developed. Firstly, when the injected hydrogen temperature decreases, the charging time increases, and the charged gas temperature decreases. Secondly, the higher the ambient temperature, the shorter the charging time, and the higher the charged gas temperature. Thirdly, the larger the mass flow rate, the shorter the charging time, and the higher charged gas temperature. Fourthly, as the initial pressure inside the vessel increases, the charging time shortens, and the charged gas temperature decreases. Fifthly, using the formulated charging strategy, during summer, the charged gas temperature decreases by approximately 9 °C. In winter, the charging time is reduced by approximately 58 s. The results provide important information of temperature control for ensuring vessel safety. 相似文献