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   1417篇
  免费   20篇
教育   1039篇
科学研究   56篇
各国文化   22篇
体育   138篇
综合类   2篇
文化理论   29篇
信息传播   151篇
  2021年   13篇
  2020年   19篇
  2019年   39篇
  2018年   35篇
  2017年   32篇
  2016年   36篇
  2015年   26篇
  2014年   50篇
  2013年   351篇
  2012年   44篇
  2011年   44篇
  2010年   30篇
  2009年   20篇
  2008年   31篇
  2007年   41篇
  2006年   27篇
  2005年   31篇
  2004年   27篇
  2003年   26篇
  2002年   27篇
  2001年   9篇
  2000年   25篇
  1999年   6篇
  1998年   10篇
  1997年   15篇
  1996年   15篇
  1995年   12篇
  1994年   18篇
  1993年   31篇
  1992年   15篇
  1991年   38篇
  1990年   20篇
  1989年   16篇
  1988年   16篇
  1987年   11篇
  1986年   16篇
  1985年   16篇
  1983年   18篇
  1982年   17篇
  1981年   19篇
  1980年   11篇
  1979年   17篇
  1978年   14篇
  1977年   8篇
  1976年   13篇
  1974年   5篇
  1973年   10篇
  1972年   6篇
  1971年   8篇
  1970年   8篇
排序方式: 共有1437条查询结果,搜索用时 234 毫秒
71.
Handedness has been studied for association with language-related disorders because of its link with language hemispheric dominance. No clear pattern has emerged, possibly because of small samples, publication bias, and heterogeneous criteria across studies. Non-right-handedness (NRH) frequency was assessed in N = 2503 cases with reading and/or language impairment and N = 4316 sex-matched controls identified from 10 distinct cohorts (age range 6–19 years old; European ethnicity) using a priori set criteria. A meta-analysis (Ncases = 1994) showed elevated NRH % in individuals with language/reading impairment compared with controls (OR = 1.21, CI = 1.06–1.39, p = .01). The association between reading/language impairments and NRH could result from shared pathways underlying brain lateralization, handedness, and cognitive functions.  相似文献   
72.
The emerging technologies on mobile-based diagnosis and bioanalytical detection have enabled powerful laboratory assays such as enzyme-linked immunosorbent assay (ELISA) to be conducted in field-use lab-on-a-chip devices. In this paper, we present a low-cost universal serial bus (USB)-interfaced mobile platform to perform microfluidic ELISA operations in detecting the presence and concentrations of BDE-47 (2,2′,4,4′-tetrabromodiphenyl ether), an environmental contaminant found in our food supply with adverse health impact. Our point-of-care diagnostic device utilizes flexible interdigitated carbon black electrodes to convert electric current into a microfluidic pump via gas bubble expansion during electrolytic reaction. The micropump receives power from a mobile phone and transports BDE-47 analytes through the microfluidic device conducting competitive ELISA. Using variable domain of heavy chain antibodies (commonly referred to as single domain antibodies or Nanobodies), the proposed device is sensitive for a BDE-47 concentration range of 10−3–104 μg/l, with a comparable performance to that uses a standard competitive ELISA protocol. It is anticipated that the potential impact in mobile detection of health and environmental contaminants will prove beneficial to our community and low-resource environments.  相似文献   
73.
Recent simulations by Chen and Dorfman [Electrophoresis 35, 405–411 (2014)] suggested that “tilting” the electric field with respect to the lattice vectors of a hexagonal post array would lead to a substantial improvement in electrophoretic DNA separations therein. We constructed such an array where the electric field is applied at an angle equidistant between the two lattice vectors. This tilted array leads to (i) baseline resolution of 20 kbp DNA and λ DNA (48.5 kbp) in a 4 mm channel and (ii) measurable separation resolutions for electric fields up to 50 V/cm, both of which are improvements over untilted post arrays of the same post density. The predicted time required to reach a resolution of unity is approximately 5 min, independent of electric field. The separations are more reproducible at higher fields.  相似文献   
74.
75.
76.
77.
78.
79.
Joel West 《Research Policy》2003,32(7):1259-1285
Computer platforms provide an integrated architecture of hardware and software standards as a basis for developing complementary assets. The most successful platforms were owned by proprietary sponsors that controlled platform evolution and appropriated associated rewards.Responding to the Internet and open source systems, three traditional vendors of proprietary platforms experimented with hybrid strategies which attempted to combine the advantages of open source software while retaining control and differentiation. Such hybrid standards strategies reflect the competing imperatives for adoption and appropriability, and suggest the conditions under which such strategies may be preferable to either the purely open or purely proprietary alternatives.  相似文献   
80.
任何一个复杂的问题都是近乎无数的事实和关系的组合。商业行为尤其受到方方面面的影响,包括过去的、非逻辑的和不可知的事物的影响。这种复杂性又因目标不同与服务于各种各样的顾客的需要而更加盘根错节,而顾客的许多目标不得不经过权衡后放弃。在这样复杂的条件下解决问题需要井井有条的、系统的方法以试图优化最后的决定。  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