全文获取类型
收费全文 | 550894篇 |
免费 | 26367篇 |
国内免费 | 12648篇 |
专业分类
电工技术 | 20865篇 |
技术理论 | 35篇 |
综合类 | 18566篇 |
化学工业 | 93034篇 |
金属工艺 | 27412篇 |
机械仪表 | 26322篇 |
建筑科学 | 29445篇 |
矿业工程 | 11233篇 |
能源动力 | 13412篇 |
轻工业 | 42521篇 |
水利工程 | 7690篇 |
石油天然气 | 26089篇 |
武器工业 | 2471篇 |
无线电 | 58903篇 |
一般工业技术 | 83717篇 |
冶金工业 | 62206篇 |
原子能技术 | 8410篇 |
自动化技术 | 57578篇 |
出版年
2023年 | 5155篇 |
2022年 | 9336篇 |
2021年 | 13823篇 |
2020年 | 10107篇 |
2019年 | 9300篇 |
2018年 | 11982篇 |
2017年 | 13046篇 |
2016年 | 12013篇 |
2015年 | 14015篇 |
2014年 | 18228篇 |
2013年 | 27438篇 |
2012年 | 25370篇 |
2011年 | 29574篇 |
2010年 | 24585篇 |
2009年 | 24298篇 |
2008年 | 24650篇 |
2007年 | 24413篇 |
2006年 | 24156篇 |
2005年 | 23240篇 |
2004年 | 16630篇 |
2003年 | 14735篇 |
2002年 | 13453篇 |
2001年 | 12665篇 |
2000年 | 12875篇 |
1999年 | 14243篇 |
1998年 | 19507篇 |
1997年 | 15224篇 |
1996年 | 12607篇 |
1995年 | 9952篇 |
1994年 | 8767篇 |
1993年 | 7523篇 |
1992年 | 6049篇 |
1991年 | 5321篇 |
1990年 | 4977篇 |
1989年 | 4684篇 |
1988年 | 4279篇 |
1987年 | 3533篇 |
1986年 | 3433篇 |
1985年 | 3668篇 |
1984年 | 3498篇 |
1983年 | 3188篇 |
1982年 | 2826篇 |
1981年 | 2987篇 |
1980年 | 2712篇 |
1979年 | 2863篇 |
1978年 | 2738篇 |
1977年 | 2841篇 |
1976年 | 3693篇 |
1975年 | 2457篇 |
1973年 | 2320篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
41.
Towards a Better Prediction of Cell Settling on Nanostructure Arrays—Simple Means to Complicated Ends 下载免费PDF全文
Nina Buch‐Månson Sara Bonde Jessica Bolinsson Trine Berthing Jesper Nygård Karen L. Martinez 《Advanced functional materials》2015,25(21):3246-3255
Vertical arrays of nanostructures (NSs) are emerging as promising platforms for probing and manipulating live mammalian cells. The broad range of applications requires different types of interfaces, but cell settling on NS arrays is not yet fully controlled and understood. Cells are both seen to deform completely into NS arrays and to stay suspended like tiny fakirs, which have hitherto been explained with differences in NS spacing or density. Here, a better understanding of this phenomenon is provided by using a model that takes into account the extreme membrane deformation needed for a cell to settle into a NS array. It is shown that, in addition to the NS density, cell settling depends strongly on the dimensions of the single NS, and that the settling can be predicted for a given NS array geometry. The predictive power of the model is confirmed by experiments and good agreement with cases from the literature. Furthermore, the influence of cell‐related parameters is evaluated theoretically and a generic method of tuning cell settling through surface coating is demonstrated experimentally. These findings allow a more rational design of NS arrays for the numerous exciting biological applications where the mode of cell settling is crucial. 相似文献
42.
43.
44.
研究了受外场驱动的两个二能级系统分别与两个单模量子化光场相互作用模型中纠缠演化及转移问题。该工作主要是对外场驱动的Landau-Zener模型进行了研究,采用旋转波近似的方法,通过数值计算详细分析了二能级系统初始状态、能级间的耦合常数以及驱动外场的参数对子系统间纠缠和转移特性的影响。结果表明,适当调节模型中的参数,可以使系统初始纠缠完全转移为光腔场间的纠缠,实现二能级系统与光场间的最大纠缠转移。 相似文献
45.
Lu Xu Baijun Liu Mingyao Zhang Yang Bai Jinming Zhang Jiayin Song 《Polymer Engineering and Science》2020,60(6):1194-1201
A series of methacrylate-acrylonitrile-butadiene-styrene (MABS) resins was prepared using bulk polymerization. The polarity of the continuous phase and the compatibility of two phases were changed by adjusting the methyl methacrylate (MMA) content, choosing values that were close to styrene-butadiene rubber solubility value. The possibility of controlling the microstructure of the MABS resin by changing the polarity of the components and the compatibility of two phases was assessed. The dynamic mechanical analysis shows that the compatibility of two phases varies with the MMA content. The morphological analysis shows that increasing MMA contents results in a gradual decrease in the sub-inclusion structure with a network skeleton of rubber particles, and that all the particles become solid rubber when the MMA content reaches 75%. The sub-inclusion structure reappears but does not have a network skeleton when the MMA content is 90%. The impact strength and morphological analysis indicate that the solid rubber particles and the sub-inclusion structure with a network skeleton provide excellent toughness, while the sub-inclusion structure without a network skeleton does not. In contrast, the transmittance of the ABS resin first increased and then decreased with increasing MMA content. 相似文献
46.
Zhijiang Li Yingping Zheng Liqin Cao Lei Jiao Yanfei Zhong Caiyi Zhang 《Color research and application》2020,45(4):656-670
Image color clustering is a basic technique in image processing and computer vision, which is often applied in image segmentation, color transfer, contrast enhancement, object detection, skin color capture, and so forth. Various clustering algorithms have been employed for image color clustering in recent years. However, most of the algorithms require a large amount of memory or a predetermined number of clusters. In addition, some of the existing algorithms are sensitive to the parameter configurations. In order to tackle the above problems, we propose an image color clustering method named Student's t-based density peaks clustering with superpixel segmentation (tDPCSS), which can automatically obtain clustering results, without requiring a large amount of memory, and is not dependent on the parameters of the algorithm or the number of clusters. In tDPCSS, superpixels are obtained based on automatic and constrained simple non-iterative clustering, to automatically decrease the image data volume. A Student's t kernel function and a cluster center selection method are adopted to eliminate the dependence of the density peak clustering on parameters and the number of clusters, respectively. The experiments undertaken in this study confirmed that the proposed approach outperforms k-means, fuzzy c-means, mean-shift clustering, and density peak clustering with superpixel segmentation in the accuracy of the cluster centers and the validity of the clustering results. 相似文献
47.
L. S. Belevskii M. A. Levantsevich R. R. Dema L. V. Deryabina T. V. Usataya O. R. Latypov 《Russian Engineering Research》2020,40(5):390-395
The machining of metal surfaces and the application of functional coatings by means of a flexible tool (a rotating wire brush) is considered. Frictional cladding may be applied on metal-cutting machines by means of simple attachments or manual angle grinders. 相似文献
48.
49.
50.
Muntasir Hashim Farnoosh Farhad David Smyth‐Boyle Robert Akid Xiang Zhang Philip J. Withers 《工业材料与腐蚀》2019,70(11):2009-2019
The environmental performance of 316L grade stainless steel, in the form of tensile specimens containing a single corrosion pit with various aspect ratios, under cyclic loading in aerated chloride solutions is investigated in this study. Results from environmental tests were compared and contrasted with those obtained using finite element analysis (FEA). Fractography of the failed specimens obtained from experiments revealed that fatigue crack initiation took place at the base of the shallow pit. The crack initiation shifted towards the shoulder and the mouth of the pit for pits of increasing depth. This process is well predicted by FEA, as the strain contour maps show that strain is the highest around the centric strip of the pit. However, for shallow pits, local strain is uniformly distributed around that strip but begins to concentrate more towards the shoulder and the mouth region for increasingly deep pits. 相似文献