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   15048篇
  免费   1230篇
  国内免费   1篇
  2021年   157篇
  2020年   123篇
  2019年   162篇
  2018年   228篇
  2017年   176篇
  2016年   350篇
  2015年   574篇
  2014年   574篇
  2013年   853篇
  2012年   1036篇
  2011年   999篇
  2010年   696篇
  2009年   550篇
  2008年   814篇
  2007年   912篇
  2006年   880篇
  2005年   870篇
  2004年   845篇
  2003年   770篇
  2002年   787篇
  2001年   196篇
  2000年   139篇
  1999年   185篇
  1998年   213篇
  1997年   147篇
  1996年   123篇
  1995年   154篇
  1994年   134篇
  1993年   127篇
  1992年   157篇
  1991年   136篇
  1990年   98篇
  1989年   123篇
  1988年   104篇
  1987年   91篇
  1986年   102篇
  1985年   113篇
  1984年   144篇
  1983年   117篇
  1982年   129篇
  1981年   112篇
  1980年   104篇
  1979年   88篇
  1978年   91篇
  1977年   78篇
  1976年   70篇
  1975年   61篇
  1974年   63篇
  1973年   52篇
  1971年   51篇
排序方式: 共有10000条查询结果,搜索用时 39 毫秒
1.
2.
3.
Summary Fifty one independent cystic fibrosis (CF) families originating from a restricted area of Southern Italy (Campania) have been analyzed for KM19 and XV2c haplotypes and the ΔF508 mutation: 54% of the total CF chromosomes show the ΔF508 mutation. No significative correlations were obtained when clinical score, radiological score,Pseudomonas colonization, or clinical symptoms at presentation were matched with the presence or absence of the ΔF508 mutation.  相似文献   
4.
The impact of using a Femtosecond laser on final functional results of penetrating keratoplasty is low. The corneal incisions presented here result from laser ablations with ultrafast desorption by impulsive vibrational excitation (DIVE). The results of the current study are based on the first proof-of-principle experiments using a mobile, newly introduced picosecond infrared laser system, and indicate that wavelengths in the mid-infrared range centered at 3 μm are efficient for obtaining applanation-free deep cuts on porcine corneas.  相似文献   
5.
This study compared two forms of accountability that can be used to promote diversity and fairness in personnel selections: identity-conscious accountability (holding decision makers accountable for which groups are selected) versus identity-blind accountability (holding decision makers accountable for making fair selections). In a simulated application screening process, undergraduate participants (majority female) sorted applicants under conditions of identity-conscious accountability, identity-blind accountability, or no accountability for an applicant pool in which white males either did or did not have a human capital advantage. Under identity-conscious accountability, participants exhibited pro-female and pro-minority bias, particularly in the white-male-advantage applicant pool. Under identity-blind accountability, participants exhibited no biases and candidate qualifications dominated interview recommendations. Participants exhibited greater resentment toward management under identity-conscious accountability.  相似文献   
6.
7.
8.
Human, rat and mouse pituitary tissues have been examined electron microscopically in transmission (TEM), scanning-transmission (STEM) and scanning (SEM) modes for the surface appearance of the secretory granules in tissue sections. Cryofixed and cryosectioned tissue showed only slightly protruding granule profiles which had a smooth surface. Cryofixed, freeze-dried and Epon embedded pituitaries, on the other hand, demonstrated swollen and furrowed surfaces over the granules after contact with water. This topography could also be seen after glutaraldehyde fixation but less after post-fixation in OsO4. The surface alterations in the sections of pituitary secretory granules are thought to be due to differences in the homogeneity of the resin infiltration, leaving resin-free openings where water can enter. It also seems probable that the Epon resin is more influenced by water than has been previously assumed, based on the findings of efficient elimination of osmium from the granules after incubation of tissue sections in water for only 10 min.  相似文献   
9.
10.
Vibrio is a very diverse genus that is responsible for different human and animal diseases. The accurate identification of Vibrio at the species level is important to assess the risks related to public health and diseases caused by aquatic organisms. The ecology of Vibrio spp., together with their genetic background, represents an important key for species discrimination and evolution. Thus, analyses of population structure and ecology association are necessary for reliable characterization of bacteria and to investigate whether bacterial species are going through adaptation processes. In this study, a population of Vibrionaceae was isolated from shellfish of the Venice lagoon and analyzed in depth to study its structure and distribution in the environment. A multilocus sequence analysis (MLSA) was developed on the basis of four housekeeping genes. Both molecular and biochemical approaches were used for species characterization, and the results were compared to assess the consistency of the two methods. In addition, strain ecology and the association between genetic information and environment were investigated through statistical models. The phylogenetic and population analyses achieved good species clustering, while biochemical identification was demonstrated to be imprecise. In addition, this study provided a fine-scale overview of the distribution of Vibrio spp. in the Venice lagoon, and the results highlighted a preferential association of the species toward specific ecological variables. These findings support the use of MLSA for taxonomic studies and demonstrate the need to consider environmental information to obtain broader and more accurate bacterial characterization.  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