全文获取类型
收费全文 | 81747篇 |
免费 | 8653篇 |
国内免费 | 5279篇 |
专业分类
电工技术 | 6038篇 |
技术理论 | 2篇 |
综合类 | 6726篇 |
化学工业 | 11812篇 |
金属工艺 | 5245篇 |
机械仪表 | 5895篇 |
建筑科学 | 6590篇 |
矿业工程 | 2583篇 |
能源动力 | 2199篇 |
轻工业 | 6928篇 |
水利工程 | 2189篇 |
石油天然气 | 3823篇 |
武器工业 | 842篇 |
无线电 | 9709篇 |
一般工业技术 | 8454篇 |
冶金工业 | 3633篇 |
原子能技术 | 1046篇 |
自动化技术 | 11965篇 |
出版年
2024年 | 262篇 |
2023年 | 1473篇 |
2022年 | 2775篇 |
2021年 | 3898篇 |
2020年 | 2913篇 |
2019年 | 2239篇 |
2018年 | 2359篇 |
2017年 | 2710篇 |
2016年 | 2431篇 |
2015年 | 3685篇 |
2014年 | 4592篇 |
2013年 | 5549篇 |
2012年 | 6130篇 |
2011年 | 6773篇 |
2010年 | 6089篇 |
2009年 | 5894篇 |
2008年 | 5883篇 |
2007年 | 5376篇 |
2006年 | 4966篇 |
2005年 | 4034篇 |
2004年 | 2682篇 |
2003年 | 1989篇 |
2002年 | 1880篇 |
2001年 | 1731篇 |
2000年 | 1499篇 |
1999年 | 1108篇 |
1998年 | 831篇 |
1997年 | 684篇 |
1996年 | 646篇 |
1995年 | 575篇 |
1994年 | 454篇 |
1993年 | 365篇 |
1992年 | 250篇 |
1991年 | 221篇 |
1990年 | 163篇 |
1989年 | 130篇 |
1988年 | 104篇 |
1987年 | 62篇 |
1986年 | 55篇 |
1985年 | 31篇 |
1984年 | 20篇 |
1983年 | 34篇 |
1982年 | 28篇 |
1981年 | 18篇 |
1980年 | 24篇 |
1979年 | 17篇 |
1976年 | 4篇 |
1967年 | 3篇 |
1959年 | 9篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
多种退化类型混合的图像比单一类型的退化图像降质更严重,很难建立精确模型对其复原,研究端到端的神经网络算法是复原的关键.现有的基于操作选择注意力网络的算法(operation-wiseattentionnetwork,OWAN)虽然有一定的性能提升,但是其网络过于复杂,运行较慢,复原图像缺乏高频细节,整体效果也有提升的空间.针对这些问题,提出一种基于层级特征融合的自适应复原算法.该算法直接融合不同感受野分支的特征,增强复原图像的结构;用注意力机制对不同层级的特征进行动态融合,增加模型的自适应性,降低了模型冗余;另外,结合L1损失和感知损失,增强了复原图像的视觉感知效果.在DIV2K,BSD500等数据集上的实验结果表明,该算法无论是在峰值信噪比和结构相似性上的定量分析,还是在主观视觉质量方面,均优于OWAN算法,充分证明了该算法的有效性. 相似文献
22.
23.
Liang Yan-Jun Lu You-Jun Gao De-Xin Wang Zhong-Sheng 《International Journal of Control, Automation and Systems》2022,20(2):507-514
International Journal of Control, Automation and Systems - The vibration control problem of offshore jacket platforms is studied. The model of offshore platforms with nonlinear interactions of the... 相似文献
24.
Juan Ding Yong He Shenhe Fu Xiangsheng Xie Haowen Liang Jianying Zhou 《Journal of the Society for Information Display》2022,30(2):159-167
Illumination is essential for modern life as colorful world is perceived by human visionary system. Display technology has been developing rapidly in recent decades, and the basic principle is related to the way that the image is illuminated and light is emanated. Traditional illumination is provided by different types of light sources, and the display image is visible in large viewing space until the emanating light decays to zero. This work proposes and demonstrates a novel illumination scheme for a display in which the displaying images are visible only in specific spatial regions. The directional backlight ensures the image propagating to specific direction while imaging visibility can be controlled to terminate abruptly at certain distance from the display screen while exerting no influence to nearby regions. The working principle for such an illumination scheme is the use of the modulated coherent directional backlight through an axicon lens. It is shown that the illumination scheme can robustly deliver carried image information to the designated viewing region. This new illumination scheme has many advantages over conventional illumination, including its usage for personal display, very lower energy consumption, as well as minimizing light hazard pollution. 相似文献
25.
We used scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to observe the oral organelle, cytopharynx, and subpellicular structure of a Dileptus sp. The main results were as follows: (a) the cytostome was located on the ventral surface of the base of the beak, surrounded by a periportal matrix that integrated 135 microtube bundles. When these microtube bundles contract, radially arranged into a disk, the cytostome was closed. When these microtube bundles were stretch, they fell into the cytostome and opens. The diameter of the cytostome was about 16 μm regardless of its closure or opening, indicating that the contraction or elongation of these microtube bundles did not change the size of the cytostome, which was only related to whether it blocked the cytostome, thus determining the opening and closing of the cytostome. There were many microtube bundles on two sides of the feeding trough, which could widen or narrow the feeding trough and facilitate beak feeding. (b) The cytopharynx was basket‐like without a bottom with a diameter of about 6 μm and was woven from two kind fibers about 0.08 and 0.19 μm. (c) There were two types of extrusomes under the pellicle. Using transmission electron microscopy,the Type I extrusomes showed narrow and long egg shape, its cross section was circular which is composed by various electronic density of concentric. Using the scanning electron microscope, they were two slightly thin clavate, the length was about 5 μm, the diameter of the middle section was about 0.75 μm, and the diameter of the two ends was about 0.32 μm, they were distributed abundantly between the microtubule fasciculi which were located on both sides of the gap on the feeding groove. Using transmission electron microscopy, the Type II extrusomes showed egg shape. Using the scanning electron microscopy, they were about 1.6 × 0.8 μm in size, they were distributed abundantly under the body pellicle while rarely the proboscis. In addition, many different of developmental stages two types of extrusomes could be also seen in the cytoplasm. (d) There were very well‐developed fibrous systems under the pellicle that were woven from fibers about 0.14 μm in diameter that attached to the pellicle and bound some organelles in the cytoplasm (e.g., mitochondria, extrusomes) and other structures to the cytoplasm and maintained cell morphology. The results of this study not only supplement and enrich the morphological contents of the Dileptus sp., but also provide the basis for the study of the taxonomy of the Dileptus sp. It also provides a new method for researchers to explore the morphology and structure of ciliate cells under the cortex by SEM. 相似文献
27.
28.
29.
30.
针对芦岭煤矿Ⅲ4采区8#、9#和10#煤层赋存情况、地质构造,结合现有矿井开拓系统及Ⅲ2、Ⅱ88采区巷道布置情况,按照采区巷道布置设计原则,提出3种采区巷道布置方案。方案一利用-590西皮大巷和-590轨道大巷新掘Ⅲ4采区上部车场,上山布置于F10断层东侧;方案二利用Ⅱ88采区下部车场及-590西皮大巷和-590轨道大巷布置Ⅲ4采区上部车场;方案三延长-900 m大巷至采区下部车场,从-590西皮大巷和-590轨道大巷中部新掘3条采区上山,并掘Ⅲ4采区石门总回风巷至Ⅱ88采区轨道巷,采区西翼布置区段平巷至井田西边界,东翼区段平巷布置至Ⅲ2采区边界。通过技术、经济比较,方案三具有初期投资小,运营费用低,经济效益最大,资源回收率高,巷道施工难度较低,开拓系统较为简单,投产工期最小的特点,最终决定采用方案三作为Ⅲ4采区巷道布置方案,保证工作面安全高效生产。 相似文献