首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   118480篇
  免费   21717篇
  国内免费   4263篇
电工技术   5839篇
技术理论   9篇
综合类   6358篇
化学工业   29477篇
金属工艺   5013篇
机械仪表   6236篇
建筑科学   8398篇
矿业工程   2773篇
能源动力   3357篇
轻工业   11861篇
水利工程   1895篇
石油天然气   5425篇
武器工业   824篇
无线电   16038篇
一般工业技术   20274篇
冶金工业   4485篇
原子能技术   933篇
自动化技术   15265篇
  2024年   202篇
  2023年   1374篇
  2022年   2195篇
  2021年   3574篇
  2020年   3976篇
  2019年   5240篇
  2018年   5458篇
  2017年   5942篇
  2016年   6082篇
  2015年   7085篇
  2014年   7756篇
  2013年   9555篇
  2012年   7653篇
  2011年   7801篇
  2010年   7517篇
  2009年   7085篇
  2008年   6712篇
  2007年   6259篇
  2006年   5923篇
  2005年   5021篇
  2004年   4071篇
  2003年   4574篇
  2002年   5152篇
  2001年   4456篇
  2000年   3386篇
  1999年   2579篇
  1998年   1487篇
  1997年   1242篇
  1996年   1052篇
  1995年   948篇
  1994年   784篇
  1993年   593篇
  1992年   438篇
  1991年   309篇
  1990年   258篇
  1989年   188篇
  1988年   165篇
  1987年   104篇
  1986年   70篇
  1985年   42篇
  1984年   32篇
  1983年   33篇
  1982年   26篇
  1981年   22篇
  1980年   19篇
  1979年   8篇
  1978年   2篇
  1959年   6篇
  1951年   2篇
  1890年   1篇
排序方式: 共有10000条查询结果,搜索用时 625 毫秒
1.
Feng  Wenran  Li  Zhen  Chen  Yingying  Chen  Jinyang  Lang  Haoze  Wan  Jianghong  Gao  Yan  Dong  Haitao 《Journal of Materials Science》2022,57(3):1881-1889
Journal of Materials Science - Although chalcogenide materials continue to generate considerable interest due to great potentials for various optoelectronic devices, annealing for a long time in...  相似文献   
2.
3.
液相色谱-串联质谱(LC-MS/MS)技术具有高灵敏度、高特异性、高分辨率和高效率的优点。近年来随着仪器灵敏度的提高,LC-MS/MS在常规临床检验中显示出极大的潜力,并在疾病早期预防和诊断中发挥着不可替代的作用。本文对LC-MS/MS在新生儿疾病筛查、维生素D检测、内分泌激素检测、肽类和蛋白质定量分析等临床检验方面的研究进展进行综述,并讨论了未来面临的挑战。  相似文献   
4.
5.
Multimedia Tools and Applications - In geometry-based point cloud compression, the geometry information is typically compressed using octree coding. In octree coding, the size of the blocks in the...  相似文献   
6.
在医疗卫生、金融证券等应用领域,经常会同时出现零观测值、一观测值较多的情况. 为更好地拟合这类数据,提出0–1膨胀几何分布模型并进行客观贝叶斯分析. 通过参数变换,得到Jeffreys先验和reference先验. 设计后验分布的抽样算法,设置不同的样本量和参数真值,采用数值模拟方法对不同客观先验下的估计效果进行评估.  相似文献   
7.
Hydraulic fracturing with slickwater is a field-proven stimulation technology used in tight reservoirs. Because of the high pumping rate associated with slickwater fracturing, drag reduction (DR) is critical in minimizing pressure drop and the success of oilfield operations. In this paper, a new type of drag reducer (SPR) was synthesized with acrylamide and 12-allyloxydodecyl acid sodium, and its drag reduction performance was evaluated. The results showed that the new drag reducer features low molecular weight, fast-dissolving rate and low interfacial tension. The algorithm of estimating the drag reduction rate of non-Newtonian fluid SPR was proposed and validated. Empirical or semianalytical models for estimating the friction ratio (σ) or friction factor (λ or f) were used to simulate the turbulence behavior of the SPR drag reducer under different Reynolds numbers (Re). The modified Virk's correlation could accurately model the turbulent behavior of the SPR drag reducer. A unified calculation formula was established in this study for different pipe diameters.  相似文献   
8.
Synthetic active matters are perfect model systems for non-equilibrium thermodynamics and of great potential for novel biomedical and environmental applications. However, most applications are limited by the complicated and low-yield preparation, while a scalable synthesis for highly functional microswimmers is highly desired. In this paper, an all-solution synthesis method is developed where the gold-loaded titania-silica nanotree can be produced as a multi-functional self-propulsion microswimmer. By applying light, heat, and electric field, the Janus nanotree demonstrated multi-mode self-propulsion, including photochemical self-electrophoresis by UV and visible light radiation, thermophoresis by near-infrared light radiation, and induced-charge electrophoresis under AC electric field. Due to the scalable synthesis, the Janus nanotree is further demonstrated as a high-efficiency, low-cost, active adsorbent for water decontamination, where the toxic mercury ions can be reclaimed with enhanced efficiency.  相似文献   
9.
Ambient condition, especially the wind condition, is an important factor to determine the behavior of hydrogen diffusion during hydrogen release. However, only few studies aim at the quantitative study of the hydrogen diffusion in a wind-exist condition. And very little researches aiming at the variable wind condition have been done. In this paper, the hydrogen diffusion in different wind condition which including the constant wind velocity and the variable wind velocity is investigated numerically. When considering the variable wind velocity, the UDF (user defined function) is compiled. Characteristics of the FGC (flammable gas cloud) and the HMF (hydrogen mass fraction) are analyzed in different wind condition and comparisons are made with the no-wind condition. Results indicate that the constant wind velocity and the variable wind velocity have totally different effect for the determination of hydrogen diffusion. Comparisons between the constant wind velocity and the variable wind velocity indicate that the variable wind velocity may cause a more dangerous situation since there has a larger FGC volume. More importantly, the wind condition has a non-negligible effect when considering the HMF along the radial direction. As the wind velocity increases, the distribution of the HMF along the radial direction is not Gaussian anymore when the distance between the release hole and the observation line exceeds to a critical value. This work can be a supplement of the research on the hydrogen release and diffusion and a valuable reference for the researchers.  相似文献   
10.
Recent advances in three‐dimensional (3D) printing have enabled the fabrication of interesting structures which are not achievable using traditional fabrication approaches. The 3D printing of carbon microtube composite inks allows fabrication of conductive structures for practical applications in soft robotics and tissue engineering. However, it is challenging to achieve 3D printed structures from solution‐based composite inks, which requires an additional process to solidify the ink. Here, we introduce a wet 3D printing technique which uses a coagulation bath to fabricate carbon microtube composite structures. We show that through a facile nanogrooving approach which introduces cavitation and channels on carbon microtubes, enhanced interfacial interactions with a chitosan polymer matrix are achieved. Consequently, the mechanical properties of the 3D printed composites improve when nanogrooved carbon microtubes are used, compared to untreated microtubes. We show that by carefully controlling the coagulation bath, extrusion pressure, printing distance and printed line distance, we can 3D print composite lattices which are composed of well‐defined and separated printed lines. The conductive composite 3D structures with highly customised design presented in this work provide a suitable platform for applications ranging from soft robotics to smart tissue engineering scaffolds. © 2019 Society of Chemical Industry  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号