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   4683篇
  免费   275篇
  国内免费   8篇
电工技术   58篇
综合类   8篇
化学工业   924篇
金属工艺   55篇
机械仪表   74篇
建筑科学   177篇
矿业工程   5篇
能源动力   159篇
轻工业   326篇
水利工程   53篇
石油天然气   35篇
无线电   390篇
一般工业技术   1185篇
冶金工业   579篇
原子能技术   13篇
自动化技术   925篇
  2024年   13篇
  2023年   59篇
  2022年   96篇
  2021年   140篇
  2020年   113篇
  2019年   122篇
  2018年   126篇
  2017年   137篇
  2016年   162篇
  2015年   134篇
  2014年   188篇
  2013年   331篇
  2012年   309篇
  2011年   384篇
  2010年   295篇
  2009年   281篇
  2008年   306篇
  2007年   243篇
  2006年   214篇
  2005年   185篇
  2004年   152篇
  2003年   133篇
  2002年   128篇
  2001年   65篇
  2000年   60篇
  1999年   59篇
  1998年   43篇
  1997年   42篇
  1996年   46篇
  1995年   40篇
  1994年   38篇
  1993年   34篇
  1992年   37篇
  1991年   20篇
  1990年   26篇
  1989年   13篇
  1988年   13篇
  1987年   27篇
  1986年   15篇
  1985年   28篇
  1984年   13篇
  1983年   6篇
  1982年   12篇
  1981年   20篇
  1977年   5篇
  1976年   7篇
  1975年   7篇
  1974年   5篇
  1973年   6篇
  1964年   4篇
排序方式: 共有4966条查询结果,搜索用时 15 毫秒
101.
4‐Anilinoquinolines were identified as potent and narrow‐spectrum inhibitors of the cyclin G associated kinase (GAK), an important regulator of viral and bacterial entry into host cells. Optimization of the 4‐anilino group and the 6,7‐quinoline substituents produced GAK inhibitors with nanomolar activity, over 50 000‐fold selectivity relative to other members of the numb‐associated kinase (NAK) subfamily, and a compound (6,7‐dimethoxy‐N‐(3,4,5‐trimethoxyphenyl)quinolin‐4‐amine; 49 ) with a narrow‐spectrum kinome profile. These compounds may be useful tools to explore the therapeutic potential of GAK in prevention of a broad range of infectious and systemic diseases.  相似文献   
102.
103.
Previous NMR microimaging studies at 360 MHz have demonstrated a clear differentiation between the nucleus and cytoplasm in isolated single neurons. In particular, theT 2 of the cell nucleus is 2.5 times larger than that of the cytoplasm. In order to determine the magnitude of possibleT 2 * influences on these observations, images of single cells have been obtained at 500 MHz using spin-echo and line-narrowing sequences. Comparison of the images acquired by the two sequences, and of the spin-echo images at 360 and 500 MHz, imply that anyT 2 * contributions are relatively small. Consequently, the measuredT 2 differences in spin-echo imaging represent a true difference in theT 2 relaxation in the two cellular compartments.  相似文献   
104.
In this work, we systematically study the spectroscopic properties of Tb3+/Dy3+ co-doped phosphate glasses in the visible spectral region and explore the sensitization role of Dy3+ in the enhancement of visible fluorescence of Tb3+ ions. Judd-Ofelt parameters Ω2 and Ω46 of the phosphate glass as host for Tb3+ are calculated as 21.60 × 10-20 cm2 and 0.73, respectively, based on the measured spectral absorption. Multiple energy transfer (ET) routes from Dy3+ to Tb3+ and their efficiencies are characterized, and the enhanced fluorescence properties of Tb3+ are investigated, including the emission spectral strength and the spontaneous emission lifetime as functions of Dy3+ doping concentration. The efficient nonradiative ET processes between Dy3+ and Tb3+ allow a moderate concentration level of Tb3+ to achieve favorably stronger spectral absorption at blue and ultraviolet wavelengths. Tb3+/Dy3+ co-doped phosphate glass shows promising potential for phosphors and lasing operation at visible wavelengths.  相似文献   
105.
3D打印,又被称为增材制造,是通过逐层累积叠加制造三维物体的一种技术手段。过去几年中,这种技术吸引了越来越多来自建筑业的关注。与传统混凝土浇筑技术相比,3D打印混凝土的应用可以实现更加高效的自由建筑制造,同时减小对人工劳动力的依赖。在全球范围内,由于相关高校和科研单位的积极参与,关于3D打印混凝土的研究工作取得了巨大的进展,其中包括澳大利亚的相关研究。本文主要对澳大利亚在3D打印混凝土研究方面有代表性的两所高校的最新进展进行介绍,两所学校分别是皇家墨尔本理工大学(RMIT大学)和斯威本科技大学。本文首先介绍了两所高校的打印设备及其特点,随后讨论了具体研究领域和近期发表的相关文章。RMIT大学主要侧重于研究纤维增强对3D打印混凝土力学性能方面的影响,而斯威本科技大学则着重研究3D打印地聚物混凝土的性能。本文旨在促进相关领域研究人员对澳大利亚3D打印混凝土研究团队和研究进展的理解。  相似文献   
106.
In this study the rational design, synthesis, and anticancer activity of quinoline‐derived trifluoromethyl alcohols were evaluated. Members of this novel class of trifluoromethyl alcohols were identified as potent growth inhibitors in a zebrafish embryo model. Synthesis of these compounds was carried out with an sp3‐C?H functionalization strategy of methyl quinolines with trifluoromethyl ketones. A zebrafish embryo model was also used to explore the toxicity of ethyl 4,4,4‐trifluoro‐3‐hydroxy‐3‐(quinolin‐2‐ylmethyl)butanoate ( 1 ), 2‐benzyl‐1,1,1‐trifluoro‐3‐(quinolin‐2‐yl)propan‐2‐ol ( 2 ), and trifluoro‐3‐(isoquinolin‐1‐yl)‐2‐(thiophen‐2‐yl)propan‐2‐ol ( 3 ). Compounds 2 and 3 were found to be more toxic than compound 1 ; apoptotic staining assays indicated that compound 3 causes increased cell death. In vitro cell proliferation assays showed that compound 2 , with an LC50 value of 14.14 μm , has more potent anticancer activity than cisplatin. This novel class of inhibitors provides a new direction in the discovery of effective anticancer agents.  相似文献   
107.
108.
109.
Adipose tissue secretes numerous hormone-like factors, which are known as adipokines. Adipokine receptors have been identified in the central nervous system but the potential role of adipokine signaling in neuroprotection is unclear. The aim of this study is to determine (1) Whether adipokines secreted from cultured adipose tissue of lean humans is protective against oxidative stress-induced neurotoxicity in human SH-SY5Y neuronal cells; and (2) To explore potential signaling pathways involved in these processes. Adipose tissue conditioned media (ATCM) from healthy lean subjects completely prevented H2O2 induced neurotoxicity, while this effect is lost after heating ATCM. ATCM activated the phosphorylation of ERK1/2, JNK and Akt at serine 308 in SH-SY5Y cells. PD98059 (25 µM), SP600125 (5 µM) and LY29400 (20 µM) partially blocked the protective effects of ATCM against H2O2 induced neurotoxicity. Findings demonstrate that heat-sensitive factors secreted from human adipose tissue of lean subjects are protective against H2O2 induced neurotoxicity and ERK1/2, JNK, and PI3K signaling pathways are involved in these processes. In conclusion, this study demonstrates preliminary but encouraging data to further support that adipose tissue secreted factors from lean human subjects might possess neuroprotective properties and unravel the specific roles of ERK1/2, JNK and PI3K in these processes.  相似文献   
110.
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