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   13962篇
  免费   184篇
  国内免费   7篇
教育   10207篇
科学研究   1208篇
各国文化   80篇
体育   1111篇
综合类   7篇
文化理论   86篇
信息传播   1454篇
  2021年   102篇
  2020年   154篇
  2019年   253篇
  2018年   350篇
  2017年   359篇
  2016年   329篇
  2015年   202篇
  2014年   279篇
  2013年   2582篇
  2012年   299篇
  2011年   362篇
  2010年   224篇
  2009年   218篇
  2008年   323篇
  2007年   232篇
  2006年   301篇
  2005年   199篇
  2004年   183篇
  2003年   174篇
  2002年   213篇
  2001年   319篇
  2000年   287篇
  1999年   259篇
  1998年   128篇
  1997年   156篇
  1996年   171篇
  1995年   175篇
  1994年   139篇
  1993年   161篇
  1992年   234篇
  1991年   209篇
  1990年   207篇
  1989年   242篇
  1988年   244篇
  1987年   205篇
  1986年   204篇
  1985年   216篇
  1984年   189篇
  1983年   229篇
  1982年   170篇
  1981年   159篇
  1980年   156篇
  1979年   229篇
  1978年   181篇
  1977年   164篇
  1976年   149篇
  1975年   128篇
  1974年   119篇
  1973年   125篇
  1971年   106篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
We present evidence on productivity improvement experienced by the research institutes of the Chinese Academy of Sciences (CAS) after its implementation of the Knowledge Innovation Program (KIP). Using a balanced panel of data on R&D inputs and outputs of 59 research institutes in CAS, we analyze the productivity, technological and efficiency changes from 1997 to 2005. We document that the CAS research institutes have a productivity growth of 12.5% from 1998 to 2005, which can be further decomposed into 8.8% attributed to technological progress and 3.3% to efficiency improvement. Results of regional analysis show that institutes in Beijing and Shanghai, performed better than institutes in other regions during the same period.  相似文献   
992.
The design and fabrication of a membrane-integrated microfluidic cell culture device (five layers,≤500 μm total thickness) developed for high resolution microscopy is reported here. The multi-layer device was constructed to enable membrane separated cell culture for tissue mimetic in vitro model applications and pharmacodynamic evaluation studies. The microdevice was developed via a unique combination of low profile fluidic interconnect design, substrate transfer methodology, and wet silane bonding. To demonstrate the unique high resolution imaging capability of this device, we used oil immersion microscopy to image stained nuclei and mitochondria in primary hepatocytes adhered to the incorporated membrane  相似文献   
993.
In this work a disposable, parallel microbioreactor (MBR) suitable for screening in batch or continuous mode is presented. The reactor consists of five parallel microchambers made of poly(dimethylsiloxane) bonded to a glass substrate. A grid structure is engraved on each chamber, allowing subsequent morphology imaging. Measurements are recorded over the entire cultivation period with constant parameters, namely, position and focus in the z-axis. The microdevice may be used for either parallel, uni- or multiparametric screening, and overcomes the drawback of gridless microwell plates which require expensive equipment such as an inverted microscope with an automatic stage. To validate the scalability from laboratory scale to microscale, and thus the cultivation protocol in the MBR, the germination of fungal spores (A. ochraceus) is evaluated for two different key magnitudes (pH and temperature) and compared to the results obtained from conventional laboratory scale systems (flasks and agar plates). Information on germination capacity with regard to interspecies' variability allows for optimization of industrial processes as optimal pH and temperature matched to the mesoscopic cultivation systems. The germination conditions therefore remain unaffected inside the MBR, while providing the following advantages: (i) dramatic reduction of medium consumption, (ii) submerged cultivation with constant oxygen supply, (iii) assured low cost and disposability, and (iv) possibility of a continuous cultivation mode.  相似文献   
994.
In this study, carbon fiber electrodes were incorporated within a hollow microneedle array, which was fabricated using a digital micromirror device-based stereolithography instrument. Cell proliferation on the acrylate-based polymer used in microneedle fabrication was examined with human dermal fibroblasts and neonatal human epidermal keratinocytes. Studies involving full-thickness cadaveric porcine skin and trypan blue dye demonstrated that the hollow microneedles remained intact after puncturing the outermost layer of cadaveric porcine skin. The carbon fibers underwent chemical modification in order to enable detection of hydrogen peroxide and ascorbic acid; electrochemical measurements were demonstrated using integrated electrode-hollow microneedle devices.  相似文献   
995.
This study evaluated the interpersonal sensitivity of third culture individuals, defined as people who lived in a country other than that of their nationality during their developmental years, by comparing them to mono-cultured individuals. While the notion that third culture individuals develop enhanced perceptual skills as a result of intercultural adaptation is widely accepted in popular and professional literature, this assertion has not been empirically tested. Previous research on intercultural communication competence and adaptation has almost exclusively focused on intercultural exposure among adults. This study collected data from 142 individuals using web-based surveys. The instruments measured two aspects of participants’ interpersonal sensitivity: social and emotional sensitivity. Results showed that third culture individuals have significantly higher social sensitivity than mono-cultured individuals, while mono-cultured individuals reported higher emotional sensitivity. Additionally, no significant correlation was found between greater intercultural experience and increased interpersonal sensitivity.  相似文献   
996.
997.
Perception of affordances research in children with developmental disabilities has only examined well practiced skills. Ten toddlers with Down syndrome and 10 with typical development walked across a GAITRite mat, with and without an obstacle. We coded the toddlers' behaviors after 1 and 3 months of walking experience when they encountered the obstacle (avoid, crawl, error and walk successfully) and calculated gait parameters (step length, width, and velocity). Both groups actively explored their affordances. Despite similar decreases in step length and velocity when approaching the obstacle, toddlers with Down syndrome were more likely to select successful but conservative crawling strategies that minimized balance requirements and reduced risk of falling. Group differences were due to risk management rather than difficulty perceiving affordances.  相似文献   
998.
999.
1000.
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