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   14294篇
  免费   1255篇
  国内免费   735篇
电工技术   969篇
综合类   1294篇
化学工业   2256篇
金属工艺   773篇
机械仪表   768篇
建筑科学   1164篇
矿业工程   401篇
能源动力   400篇
轻工业   995篇
水利工程   366篇
石油天然气   709篇
武器工业   103篇
无线电   1566篇
一般工业技术   1646篇
冶金工业   587篇
原子能技术   131篇
自动化技术   2156篇
  2024年   68篇
  2023年   202篇
  2022年   338篇
  2021年   499篇
  2020年   386篇
  2019年   344篇
  2018年   365篇
  2017年   384篇
  2016年   345篇
  2015年   498篇
  2014年   641篇
  2013年   689篇
  2012年   825篇
  2011年   807篇
  2010年   802篇
  2009年   758篇
  2008年   829篇
  2007年   790篇
  2006年   705篇
  2005年   589篇
  2004年   521篇
  2003年   765篇
  2002年   1090篇
  2001年   946篇
  2000年   507篇
  1999年   356篇
  1998年   218篇
  1997年   191篇
  1996年   140篇
  1995年   151篇
  1994年   139篇
  1993年   87篇
  1992年   77篇
  1991年   54篇
  1990年   28篇
  1989年   24篇
  1988年   36篇
  1987年   13篇
  1986年   16篇
  1985年   12篇
  1984年   8篇
  1983年   7篇
  1982年   4篇
  1981年   4篇
  1980年   9篇
  1979年   7篇
  1972年   3篇
  1971年   2篇
  1968年   1篇
  1951年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Shu  Fei  Dinneen  Jesse David  Chen  Shiji 《Scientometrics》2022,127(6):3613-3628
Scientometrics - Examining the relationships among scientific disciplines is important today, but existing methods are limited by the contents and structure of their bibliographic databases. We...  相似文献   
3.
Background: Within the claudin (CLDN) family, CLDN12 mRNA expression is altered in various types of cancer, but its clinicopathological relevance has yet to be established due to the absence of specific antibodies (Abs) with broad applications. Methods: We generated a monoclonal Ab (mAb) against human/mouse CLDN12 and verified its specificity. By performing immunohistochemical staining and semiquantification, we evaluated the relationship between CLDN12 expression and clinicopathological parameters in tissues from 138 cases of cervical cancer. Results: Western blot and immunohistochemical analyses revealed that the established mAb selectively recognized the CLDN12 protein. Twenty six of the 138 cases (18.8%) showed low CLDN12 expression, and the disease-specific survival (DSS) and recurrence-free survival rates were significantly decreased compared with those in the high CLDN12 expression group. We also demonstrated, via univariable and multivariable analyses, that the low CLDN12 expression represents a significant prognostic factor for the DSS of cervical cancer patients (HR 3.412, p = 0.002 and HR 2.615, p = 0.029, respectively). Conclusions: It can be concluded that a reduced CLDN12 expression predicts a poor outcome for cervical cancer. The novel anti-CLDN12 mAb could be a valuable tool to evaluate the biological relevance of the CLDN12 expression in diverse cancer types and other diseases.  相似文献   
4.
In this study, the anti-atherosclerotic properties of three marine phospholipids (MPLs) extracts from fishery by-products including codfish roe, squid gonad, and shrimp head are verified. Their effects on key factors involved in atherosclerosis are examined and compared to explore whether the differences in their constitutions lead to the differences in the function. All three MPLs dampen oxidation of low- density lipoproteins (LDL) in vitro. Treating RAW264.7 macrophages and HUVECs endothelial cells with each MPLs ranging 10–100 µg mL−1 does not decrease cell viability, yet ox-LDL caused cytotoxicity of both cells are alleviated by 50 or 100 µg mL−1 MPLs treatment. In addition, the three MPLs reduce ox-LDL induced macrophage foam-like transition, mainly through inhibition of lipid uptake. Of the three MPLs, the one from squid gonad exhibits the best effect. On the other hand, all three MPLs modulate inflammatory responses, equally, by inhibiting the adhesion of monocytes to endothelial cells, and decreasing secretion of pro-inflammatory cytokines IL-6 and MCP-1. Using a high-cholesterol diet induced zebrafish model, it is found that all three MPLs, especially the one from squid gonad, alleviates cholesterol accumulation in early plaques, and decreases total cholesterol as well as lipid peroxide in vivo. Practical Applications: As a way of making the best of the increasingly scarce marine resources, valuable lipid components can be recovered from by-products and wastes from the fishery industry. Here, we tested the anti-atherosclerotic effects and the mechanisms of three MPLs extracted from codfish roe, squid gonad, and shrimp head. Our study provides further evidence that marine phospholipids extracted from fishery by-products could protect against atherosclerosis, and helps to elucidate the structure-function relationship of MPLs.  相似文献   
5.
使用气-质联用仪测定餐饮废油生物柴油(WCME)和-10号柴油(-10PD)的组成,使用冷滤点试验器和运动黏度试验器测定WCME的低温流动性,同时使用调合、添加低温流动性改进剂的方法改进WCME的低温流动性。实验结果表明,WCME主要由饱和脂肪酸甲酯和不饱和脂肪酸甲酯组成,质量分数分别为27.63%和71.81%;WCME冷滤点为0℃,运动黏度(40℃)为4.41mm2/s;WCME与-10PD调合后,冷滤点降低,其中B20的冷滤点最低,为-13℃,运动黏度随着WCME的体积分数的减少,逐渐接近-10PD的运动黏度。通过添加低温流动性改进剂,WCME,B10,B20的冷滤点分别从0,-8,-13℃降至-4,-26,-25℃。  相似文献   
6.
设计了基于Web的3D模型浏览与交互系统,主要采用基于WebGL的第三方库Three.js来实现。该系统的建立主要包括场景的构建、场景的交互控制和模型的云存储。模型是场景构建的前提,用户可从外部导入所需模型或利用系统自带的简单模型进行模型的构建。场景交互技术主要包括模型的平移、旋转、缩放、拾取、剖切、3D动画模型的播放以及信息的显示等。模型的云存储是指用户可以通过登录账户将3D模型存储到服务器,日后需要时直接从服务器中加载即可。  相似文献   
7.
Chen  Xi  Zhao  Huan-jing  Zhao  Shu  Chen  Jie  Zhang  Yan-ping 《Scientometrics》2019,121(2):937-956
Scientometrics - Due to the development of academic, more and more attentions are paid to citation recommendation. To solve the citation recommendation problem, researchers begin to focus on the...  相似文献   
8.
9.
10.
A locomotive cabin adsorption air‐conditioner has been equipped in #DF4B‐2369 locomotive; and has been successfully run for 2 years. It is powered by waste heat from the exhaust of the diesel engine. The influence on heat transfer is described by the equivalent heat transfer coefficient or thermal resistance of components inside the adsorber. The variation of adsorption capacity is expressed by a non‐equilibrium adsorption function. The dynamic heat transfer process of adsorption air‐conditioning system is treated with the lumped parameter method. Some typical running experimental results are present. The diesel engine rotating speed and locomotive speed influenced on the refrigeration system are discussed. The maximum mean refrigeration power is regarded as an objective function. Based on experiments and theoretical analysis, the running characteristics of the air‐conditioning system are optimized. Some techniques of performance improvement are suggested as well. Copyright © 2006 John Wiley & Sons, Ltd.  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