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   98篇
  免费   9篇
  2023年   3篇
  2022年   1篇
  2021年   3篇
  2020年   1篇
  2019年   3篇
  2018年   1篇
  2017年   3篇
  2016年   3篇
  2015年   3篇
  2014年   4篇
  2013年   6篇
  2012年   9篇
  2011年   6篇
  2010年   5篇
  2009年   1篇
  2007年   4篇
  2006年   3篇
  2005年   5篇
  2004年   3篇
  2003年   2篇
  2002年   2篇
  2001年   1篇
  2000年   4篇
  1999年   4篇
  1998年   6篇
  1997年   4篇
  1996年   2篇
  1995年   4篇
  1994年   4篇
  1991年   1篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1985年   1篇
  1980年   1篇
  1975年   1篇
排序方式: 共有107条查询结果,搜索用时 935 毫秒
41.
42.
43.
It is of interest to evaluate the prevalence of systemic disorders in patients undergoing minor oral surgeries at a dental hospital. This will help to take necessary precautions prior to oral surgeries. We used the digital case records of 1288 patients who underwent minor oral surgeries in a hospital. Demographic details and systemic diseases of the patients were recorded from digital case records. Data shows that 103 patients (7.9%) of the total number of patients undergoing minor oral surgeries had systemic diseases with 3.8% of patients diagnosed with diabetes. Statistically significant associations were found between type of minor oral surgery and the type of systemic disease (p<0.001); age of patients and type of minor oral surgery (p<0.001); age and type of systemic diseases (p<0.001) and gender of patient and type of minor oral surgery (p = 0.005). Thus, data shows the prevalence of systemic diseases in patients undergoing minor oral surgeries was 7.9%.  相似文献   
44.
We describe for the first time the sexual behavior and the courtship song of males of the African fly Zaprionus indianus (Gupta), a recent invader of South America. The male courtship song is formed by monocyclic pulses and the courtship behavior is simple when compared to that of species of Drosophila. Two interpulse interval (IPI) distributions were observed: pre-mounting and mounting. No significant difference was observed between the pre-mounting IPIs of males that descended from three geographical populations from South America. We also observed the songs produced by females and the homosexual behavior exhibited by males. A sequence of bursts is produced by females as a refusal signal against males, while males emit a characteristic song that identifies sex genus, which differs from the courtship song. The short courtship and mating latencies recorded reveal vigorous males and receptive females, respectively.  相似文献   
45.
In this study we describe the sociodemographic characteristics of people participating in a clinical trial on the safety and immunogenicity of a H5N1 influenza vaccine and we identify the main motivations for joining it.  相似文献   
46.
Running  S. W.  Waring  R. H.  Rydell  R. A. 《Oecologia》1975,21(1):1-16
Summary Pre-hatching developmental times for prosobranch gastropods are greatly influenced by temperature and taxonomic affinity. If the data used here (including all available data from the Muricacea) are a representative sample, then reasonably accurate estimates of developmental time can be obtained for most prosobranchs knowing only temperature and taxon. Times are also significantly affected by egg or hatching size. Correlations between developmental time and hatching form are probably accounted for by egg size. Prehatching periods are little, if at all, longer for metamorphosed hatchlings than for swimming hatchlings; in any event, differences are small relative to typical free swimming periods. Therefore, the planktonic period is a substantial addition to the total pre-juvenile period. Many embryos die before hatching. More would survive if development were faster; development is, therefore, prolonged at a measurable selective cost. Factors promoting extended developmental periods should be evaluated with these costs in mind. For example, providing much of the yolk as nurse-eggs may allow a species to have a large hatching size and at the same time a relatively brief developmental time.  相似文献   
47.
48.
Arabidopsis (Arabidopsis thaliana) mutants lacking a functional ERA1 gene, which encodes the beta-subunit of protein farnesyltransferase (PFT), exhibit pleiotropic effects that establish roles for protein prenylation in abscisic acid (ABA) signaling and meristem development. Here, we report the effects of T-DNA insertion mutations in the Arabidopsis GGB gene, which encodes the beta-subunit of protein geranylgeranyltransferase type I (PGGT I). Stomatal apertures of ggb plants were smaller than those of wild-type plants at all concentrations of ABA tested, suggesting that PGGT I negatively regulates ABA signaling in guard cells. However, germination of ggb seeds in response to ABA was similar to the wild type. Lateral root formation in response to exogenous auxin was increased in ggb seedlings compared to the wild type, but no change in auxin inhibition of primary root growth was observed, suggesting that PGGT I is specifically involved in negative regulation of auxin-induced lateral root initiation. Unlike era1 mutants, ggb mutants exhibited no obvious developmental phenotypes. However, era1 ggb double mutants exhibited more severe developmental phenotypes than era1 mutants and were indistinguishable from plp mutants lacking the shared alpha-subunit of PFT and PGGT I. Furthermore, overexpression of GGB in transgenic era1 plants partially suppressed the era1 phenotype, suggesting that the relatively weak phenotype of era1 plants is due to partial redundancy between PFT and PGGT I. These results are discussed in the context of Arabidopsis proteins that are putative substrates of PGGT I.  相似文献   
49.
Genetic separation of third and fourth whorl functions of AGAMOUS.   总被引:13,自引:2,他引:11       下载免费PDF全文
AGAMOUS (AG) is an Arabidopsis MADS box gene required for normal development of the third and fourth whorls of the flower. In previously described ag mutants, the third whorl stamens are replaced by petals, and the fourth whorl is replaced by another (mutant) flower. We describe two new ag alleles, ag-4 and AG-Met205, retaining partial AG activity. Both produce flowers with stamens in the third whorl and indeterminate floral meristems; however, ag-4 flowers contain sepals in the fourth whorl, and AG-Met205 produces carpels. The ag-4 mutation results in partial loss of the C terminus of the K domain, a putative coiled coil, and AG-Met205 contains a site-directed mutation that causes a single amino acid change in this same region of the K box. Two models that might explain how these changes in AG result in the separation of different AG activities are discussed.  相似文献   
50.
Testing scale dependent assumptions in regional ecosystem simulations   总被引:1,自引:0,他引:1  
Abstract. We present a Regional Ecosystem Simulation System (RESSys) which uses satellite data to define vegetation properties, topographic and soil data to define site characteristics, and a climate generator program to build a topographically sensitive microclimate map. We use a 150-km2 mountainous forested watershed in Glacier National Park to test the consequences of modeling various ecosystems processes using different versions of RESSys with increasing simplification of the landscape: (1) spatial scaling generated using 30 m x 30 m Landsat Thematic Mapper data versus 1 km x 1 km Advanced Very High Resolution Radiometer data for vegetation definition; (2) modeling hydrologic dynamics produced by using a topographic routing model versus a simple soil ‘bucket’ model; (3) variable landscape partitioning based on patterns of topographic complexity; and (4) representation of annual net primary productivity (ANPP) using an absorbed photosynthetic active radiation (APAR) model. We evaluate results of these simulations by comparison with average values and areal distributions of photosynthesis, evapotranspiration, hydrologic outflow, and ANPP. Our primary goal is to test whether areal average flux of carbon and water can be scaled linearly over a complex landscape. We found that daily photosynthesis could be predictably estimated between modeling scales with correlation coefficients ranging between 0.89 to 0.99. ANPP was highly correlated among the modeling scales with maximum differences between ANPP prediction of ca. 0.5Mg C ha-1 yr-1. Evapotranspiration was similarly predictable between scales but was influenced by differences associated with hydrologic modeling. Hydrologic outflow was not highly correlated between different modeling scales as a function of the different hydrologic models used at different scales.  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