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   4819640篇
  免费   317699篇
  国内免费   182755篇
电工技术   260075篇
技术理论   125篇
综合类   263455篇
化学工业   705065篇
金属工艺   231218篇
机械仪表   259008篇
建筑科学   270319篇
矿业工程   112503篇
能源动力   135490篇
轻工业   396178篇
水利工程   100166篇
石油天然气   142485篇
武器工业   35676篇
无线电   515896篇
一般工业技术   587392篇
冶金工业   565152篇
原子能技术   63956篇
自动化技术   675935篇
  2023年   42783篇
  2022年   101905篇
  2021年   145353篇
  2020年   105034篇
  2019年   85767篇
  2018年   102801篇
  2017年   112883篇
  2016年   104218篇
  2015年   126208篇
  2014年   172743篇
  2013年   272889篇
  2012年   281472篇
  2011年   320218篇
  2010年   286938篇
  2009年   287130篇
  2008年   293810篇
  2007年   285114篇
  2006年   258783篇
  2005年   216070篇
  2004年   154167篇
  2003年   118467篇
  2002年   111054篇
  2001年   101938篇
  2000年   99052篇
  1999年   81873篇
  1998年   143177篇
  1997年   101112篇
  1996年   85651篇
  1995年   67116篇
  1994年   58307篇
  1993年   50176篇
  1992年   33459篇
  1991年   30148篇
  1990年   29952篇
  1989年   29017篇
  1988年   26870篇
  1987年   24426篇
  1986年   23712篇
  1985年   25476篇
  1984年   22105篇
  1983年   20283篇
  1982年   19178篇
  1981年   19532篇
  1980年   18760篇
  1979年   16826篇
  1978年   16241篇
  1977年   22923篇
  1976年   33660篇
  1975年   14037篇
  1974年   13030篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
RCAS1 is a protein that participates in regulation of the tumor microenvironment and its immune responses, all in order to evade the immune system. The aim of this study was to analyze RCAS1 expression in urothelial bladder cancer cells (and in fibroblasts and macrophages of the tumor stroma) and its relationship with the histological pattern of malignancy. Eighty-three postcystectomy patients were enrolled. We analyzed the histological maturity (grade), progress (pT stage), tissue invasion type (TIT), nonclassic differentiation number (NDN), and the ability to metastasize (pN). The expression of RCAS1 protein was analyzed by immunohistochemistry. Indicators of histological malignancy were observed solely in association with the RCAS1 expression in cells in the border parts (BPs) of the tumor. Histological malignancy of the tumor, indicated by the pT and pN, and metastasis-free survival time, correlated significantly with RCAS1 expression in tumor neoplastic cells, whereas malignancy determined by grade, TIT, and NDN correlated with RCAS1 expression in fibroblasts and macrophages in the tumor microenvironment. These findings suggest that the increased RCAS1 expression depends on its cellular source and that RCAS1 expression itself is a component of various signaling pathways. The immune escape occurs within the tumor BPs, where the increase in the RCAS1 expression occurs within tumor cells and stromal cells in its microenvironment. We conclude that the histological pattern of tumor malignancy, indicated by grade, TIT, NDN, pT, and pN is a morphological indicator of immune escape.  相似文献   
972.
Peer-to-Peer Networking and Applications -  相似文献   
973.
974.
SDN中基于KMOBPSO的高可靠性控制器部署算法   总被引:1,自引:0,他引:1  
针对SDN中控制器系统的单节点故障问题,兼顾系统成本和系统时延,应用N+1冗余备份模型来提高SDN控制器部署的可靠性,并将其抽象为多目标优化问题.同时,提出了一种融合K-means聚类算法和遗传算子的多目标二进制粒子群算法——KMOBPSO算法,以求解SDN控制器高可靠性部署问题的解.仿真结果表明,所提算法具有求解精度高、分布均匀、沿Pareto前沿面覆盖广的特点,能够显著提高SDN中控制器部署的可靠性.  相似文献   
975.
976.
Number entry is a ubiquitous activity and is often performed in safety- and mission-critical procedures, such as healthcare, science, finance, aviation and in many other areas. We show that Monte Carlo methods can quickly and easily compare the reliability of different number entry systems. A surprising finding is that many common, widely used systems are defective, and induce unnecessary human error. We show that Monte Carlo methods enable designers to explore the implications of normal and unexpected operator behaviour, and to design systems to be more resilient to use error. We demonstrate novel designs with improved resilience, implying that the common problems identified and the errors they induce are avoidable.  相似文献   
977.
978.
This study investigates the impact of lighting colors on subjective judgments of fabric: in particular, whether the influence of lighting varies depending on fabric types and color combinations. We conducted two visual assessments. In Study 1 (N = 44), eight illuminants and six types of fabric were presented as cloth stimuli. Derived from the literature review, four sets of adjectives (humble-luxurious, cool-warm, old-new, and not preferred-preferred) were used as metrics. In Study 2 (N = 41), five sets of fabric color combination swatches were assessed under lighting conditions that were identical to those of Study 1. Three bipolar scales (ordinary-characterful, classic-modern, and soft-rigid), were employed from factor analysis along with three unipolar scales (luxurious, preferred, harmonious with lighting). The results showed that hue characteristics of lighting and cloth types influenced participants' perceptions of the fabric. Overall, white lighting with 4000 K was the most preferred and luxurious lighting across various types of clothes, while a pinkish white with 4700 K (duv = −0.0127) was the best matched in every color combination. In addition, there were interaction effects between lighting colors, clothes types, and fabric color combinations with regard to each of the perceptual qualities. This study provides empirical evidence for optimally match lighting colors with fabric in the presentation of fabric goods.  相似文献   
979.
980.
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