全文获取类型
收费全文 | 3175篇 |
免费 | 265篇 |
国内免费 | 188篇 |
专业分类
电工技术 | 146篇 |
综合类 | 277篇 |
化学工业 | 158篇 |
金属工艺 | 109篇 |
机械仪表 | 191篇 |
建筑科学 | 241篇 |
矿业工程 | 349篇 |
能源动力 | 33篇 |
轻工业 | 301篇 |
水利工程 | 58篇 |
石油天然气 | 779篇 |
武器工业 | 28篇 |
无线电 | 146篇 |
一般工业技术 | 307篇 |
冶金工业 | 85篇 |
原子能技术 | 21篇 |
自动化技术 | 399篇 |
出版年
2024年 | 6篇 |
2023年 | 10篇 |
2022年 | 73篇 |
2021年 | 80篇 |
2020年 | 70篇 |
2019年 | 69篇 |
2018年 | 56篇 |
2017年 | 85篇 |
2016年 | 93篇 |
2015年 | 113篇 |
2014年 | 181篇 |
2013年 | 167篇 |
2012年 | 235篇 |
2011年 | 266篇 |
2010年 | 182篇 |
2009年 | 157篇 |
2008年 | 160篇 |
2007年 | 221篇 |
2006年 | 204篇 |
2005年 | 149篇 |
2004年 | 133篇 |
2003年 | 149篇 |
2002年 | 131篇 |
2001年 | 116篇 |
2000年 | 114篇 |
1999年 | 98篇 |
1998年 | 75篇 |
1997年 | 65篇 |
1996年 | 44篇 |
1995年 | 39篇 |
1994年 | 31篇 |
1993年 | 13篇 |
1992年 | 13篇 |
1991年 | 6篇 |
1990年 | 11篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1979年 | 2篇 |
1956年 | 1篇 |
排序方式: 共有3628条查询结果,搜索用时 15 毫秒
1.
在多晶硅太阳能电池的生产过程中, 金刚线切割技术(Diamond wire sawn, DWS)具有切割速度快、精度高、原材料损耗少等优点, 受到了广泛关注。金刚线切割多晶硅表面形成的损伤层较浅, 与传统的酸腐蚀制绒技术无法匹配, 金属催化化学腐蚀法应运而生。金属催化化学腐蚀法制绒具有操作简单、结构可控且易形成高深宽比的绒面等优点, 具有广阔的应用前景。本文总结了不同类型的金属催化剂在制绒过程中的腐蚀机理及其形成的绒面结构, 深入分析和讨论了具有代表性的银、铜的单一及复合催化腐蚀过程及绒面结构和电池片性能。最后对金刚线切割多晶硅片表面的金属催化化学腐蚀法存在的问题进行了分析, 并展望了未来的研究方向。 相似文献
2.
3.
4.
就经典分水岭图像分割算法中存在的过分割问题,提出一种结合位图切割和区域合并的彩色图像分割算法。对原始彩色图像通过空域梯度算子求其梯度图像,并利用位图切割重建梯度图像;对新梯度图像进行分水岭预分割;对预分割图像基于异质性最小原则进行区域合并,并获得最终分割结果。相比于现有的同类方法,该算法引入位图切割,抑制噪声对分割结果的影响,在边缘模糊处分割准确,得到符合人类视觉的较小分割区域数目,同时在运行效率上提高。 相似文献
5.
Propagation characteristics of Rayleigh-type wave in a piezoelectric layered system are theoretically investigated. The piezoelectric layer is considered as a cubic crystal with finite thickness rotated about Y-axis and is imperfectly bonded onto a semi-infinite dielectric substrate. The imperfect interface between the two constituents is assumed to be mechanically compliant and dielectrically weakly conducting. The exact dispersion relations for electrically open or shorted boundary conditions are obtained. The numerical results show that the phase velocity of Rayleigh-type wave is symmetric with respect to the cut orientation of 45。 and can achieve the maximum propagation speed in this orientation. The mechanical imperfection plays an important role in the dispersion relations, further the normal imperfection can produce a significant reduction of phase velocity comparing with the tangential imperfection. Comparing with the mechanical imperfection the electrical imperfection makes a relatively small reduction of phase velocity of Rayleigh-type wave. The obtained results can provide some fundamentals for understanding of piezoelectric semiconductor and for design and application of piezoelectric surface acoustic wave devices. 相似文献
6.
Andrés Mario Zervigón 《History of Photography》2019,43(2):130-143
For decades now, Douglas Crimp’s landmark 1980 essay ‘The Photographic Activity of Postmodernism’ has shaped our understanding of modernism’s aftermath, at least as it unfolded in North America and Western Europe. Less remembered, however, is the degree to which the procedures of disjunction, copying, appropriation, and outright theft that he highlighted were epitomised not just by contemporary photography, but by photomontage in particular. This article recovers the debates that led critics such as Crimp, Abigail Solomon-Godeau, Christopher Phillips, Benjamin Buchloh and others to turn to photomontage as one of their principal objects of concern in what became known as the postmodern critique of photography. Why was montage tasked to perform this critical function, particularly by people around the journal October who had not otherwise devoted the balance of their writing to photography’s history? The article suggests that these men and women, along with the contemporary artists they foregrounded, manifested what Mary Anne Doane has called a ‘desire for signification’, a reaction in the late 1970s against the mute theatricality of minimalist and conceptual art. Photomontage reintroduced representation to contemporary art and to the canon of art history. But unlike the reemerging illusionism in painting that also manifested this desire, montage guarded against an uncomplicated realism by highlighting and critiquing operations of representation in a manner that painting no longer could. 相似文献
7.
Alessandra Danza Amalia Conte Annamaria Cedola Inna Chisacova Matteo Alessandro Del Nobile 《International Journal of Food Science & Technology》2015,50(12):2688-2693
The best packaging conditions for rocket salad were assessed by subsequent experimental trials. In the first step, a preliminary screening of different packaging materials was performed and two micro‐perforated oriented polypropylene films with different micro‐hole diameters (90 and 110 μm) were selected as best packaging solutions. In the subsequent experimental step, modified headspace conditions were applied without any improvement on product quality. In the last step, the effects of an ethylene adsorbent were analysed. Rocket salad packaged in both films with the ethylene adsorbent recorded a shelf life of about 16 days, compared to the control samples that remained acceptable for 13 days. During storage, the microbial quality (mesophilic and psychrotrophic bacteria, pseudomonadaceae, lactic acid bacteria, yeasts, total coliforms and enterobacteriacae), the pH, the colour changes and the main sensory parameters were also monitored. 相似文献
8.
Video cutout refers to extracting moving objects from videos, which is an important step in many video editing tasks. Recent algorithms have limitations in terms of e?ciency, interaction style, and rob... 相似文献
9.
为了解决潘三矿1642(1)大断面切眼的支护及施工技术难题,实现工作面的快速接替,分析了大断面切眼的支护原理,提出了锚网索、T3钢带和单体液压支柱配合工字钢挑梁的联合支护方式。同时根据一次成巷与二次成巷的优缺点对比,最终确定采用分次交替掘进、一次成巷的施工方案并取得了良好的社会经济效益,为类似条件下大断面切眼巷道的施工提供了很好的借鉴和参考。 相似文献
10.
切光马达使用寿命到期之后就会停转,从而对仪表的测量造成误差,失真的仪表示值又会对工艺人员的操作造成直接的影响,进而影响工艺产品的产品质量。本文通过对这种红外分析仪最常见的且容易发生的故障进行分析,并写出如何更换马达,以及更换后使用效果很好地恢复这一示例,给出了解决马达失效停转问题的正确方法。 相似文献