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   302篇
  免费   22篇
  2022年   2篇
  2021年   3篇
  2019年   2篇
  2018年   2篇
  2017年   6篇
  2016年   4篇
  2015年   12篇
  2014年   15篇
  2013年   18篇
  2012年   20篇
  2011年   11篇
  2010年   9篇
  2009年   16篇
  2008年   15篇
  2007年   14篇
  2006年   17篇
  2005年   17篇
  2004年   15篇
  2003年   7篇
  2002年   6篇
  2001年   13篇
  2000年   12篇
  1999年   8篇
  1998年   12篇
  1997年   6篇
  1996年   6篇
  1995年   4篇
  1994年   2篇
  1993年   2篇
  1992年   3篇
  1991年   2篇
  1990年   2篇
  1989年   4篇
  1987年   3篇
  1986年   3篇
  1984年   4篇
  1983年   2篇
  1982年   3篇
  1979年   2篇
  1978年   1篇
  1977年   1篇
  1976年   5篇
  1975年   1篇
  1974年   1篇
  1972年   1篇
  1971年   1篇
  1970年   1篇
  1967年   3篇
  1966年   1篇
  1887年   1篇
排序方式: 共有324条查询结果,搜索用时 31 毫秒
1.
The treatment of five children with the haemolytic-uraemic syndrome using streptokinase is described to illustrate the difficulties and limitations of thrombolytic therapy in this disease. This experience is germane to the design of multicentre clinical trials.A multivariate analysis relating clinical outcome to the data obtained at the time of admission was also carried out for 31 children with the disease treated in four centres. The results suggest that this technique may help to identify those patients likely to have a fatal outcome. An expanded form of this type of analysis should be incorporated in future clinical trials.  相似文献   
2.
A. M. Flinn  D. L. Smith 《Planta》1967,75(1):10-22
Summary Enzyme activity is not uniformly distributed through the cotyledon of Pisum arvense. Initially the peripheral region, certain scattered cells of the storage tissue and the procambium show a high level of activity of succinic dehydrogenase, cytochrome oxidase, acid phosphatase and esterase. Activity of acid phosphatase declines sharply after the first day of germination; activity of the other enzymes declines after about three days. In the storage tissue, where activity is lower initially, it declines after about five days and is correlated with the disappearance of the reserves. The pattern of alkaline phosphatase activity is similar except that activity is lower in the procambium but increases in the sieve-elements during differentiation of the phloem. 5-nucleotidase and glucose-6-phosphatase activity is low throughout the cotyledon but it also increases to a significant level in the sieve-elements. Activity of starch synthesizing enzymes is high in the parenchymatous bundle sheath, where they may be involved in the pathway from lipids to soluble carbohydrates.  相似文献   
3.
Storage proteins of interior spruce ( Picea glauca engelmanii complex) somatic embryos were compared to those of zygotic embryos by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. Somatic embryos contain the same storage proteins as zygotic embryos based on similarities of molecular weight, isoelectric variants, solubility characteristics and disulfide linkages. Storage protein levels varied among different somatic embryo genotypes; however, all genotypes tested accumulated significant amounts of storage proteins. Zygotic and somatic embryos display a similar developmental accumulation of storage proteins. The 22, 24, 33 and 35 kDa proteins appear in early stage embryos, while the 41 kDa protein begins to accumulate during mid cotyledon development. The 22, 24 and 41 kDa proteins accumulate continuously during cotyledon development in somatic embryos cultured on abscisic acid. In contrast, zygotic embryos display a more rapid and transient accumulation of these proteins.  相似文献   
4.
5.
The effect of neurotensin on submaximally-stimulated hepatobiliary and pancreatic secretion was studied in 6 healthy subjects. An intravenous infusion of neurotensin 1.4 ± 0.3 pmol/kg/min, designed to reproduce plasma neurotensin immunoreactivity levels within the physiological range, produced a significant increase in pancreatic bicarbonate output. Plasma concentrations of pancreatic polypeptide rose by 83 ± 16 pmol/l and were associated with a small reduction in trypsin, but no significant change in bilirubin outputs.  相似文献   
6.
Elevated postexercise amino acid availability has been demonstrated to enhance muscle protein synthesis acutely, but the long-term impact of postexercise protein supplementation on variables such as health, muscle soreness, and function are unclear. Healthy male US Marine recruits from six platoons (US Marine Corps Base, Parris Island, SC; n = 387; 18.9 +/- 0.1 yr, 74.7 +/- 1.1 kg, 13.8 +/- 0.4% body fat) were randomly assigned to three treatments within each platoon. Nutrients supplemented immediately postexercise during the 54-day basic training were either placebo (0 g carbohydrate, 0 g protein, 0 g fat), control (8, 0, 3), or protein supplement (8, 10, 3). Subjects and observers making measurements and data analysis were blinded to subject groupings. Compared with placebo and control groups, the protein-supplemented group had an average of 33% fewer total medical visits, 28% fewer visits due to bacterial/viral infections, 37% fewer visits due to muscle/joint problems, and 83% fewer visits due to heat exhaustion. Recruits experiencing heat exhaustion had greater body mass, lean, fat, and water losses. Muscle soreness immediately postexercise was reduced by protein supplementation vs. placebo and control groups on both days 34 and 54. Postexercise protein supplementation may not only enhance muscle protein deposition but it also has significant potential to positively impact health, muscle soreness, and tissue hydration during prolonged intense exercise training, suggesting a potential therapeutic approach for the prevention of health problems in severely stressed exercising populations.  相似文献   
7.
All networks are made up of vertices (points interconnected by segments), which include terminals interconnected by terminal segments, nodes interconnected by link segments and the root point connected to the tree by the root segment. All nodes may be classified into unique types according to the number of terminal and link segments they drain. For example, there are three distinct dichotomous nodes, a 'primary' node draining two terminal segments, a 'secondary' node draining one terminal segment and a link segment, and a 'tertiary' node draining two link segments. The numbers of primary and tertiary nodes approximate to equality in large networks and thus the ratio of primary to secondary nodes defines topology. All higher order nodes ( trichotomous and beyond) may be resolved into dichotomous forms and incorporated into the analysis. Different forms of growth may thus be analysed by comparing the frequency distributions of nodes with those generated by computer simulated growth models. Moreover, all vertices can be ordered so that metrical parameters are easily incorporated and the hierarchical arrangements of vertices of different order discerned. The dendritic trees of 48 Purkinje cells, taken from folia along the primary fissure, were analysed using vertex analysis. The mean number of segments in Purkinje cell trees was 881 +/- 23 (s.e.) and mean total dendritic length 7959 +/- 233 (s.e.) micrometers. Segment lengths were longest over proximal segments but over most of the tree segment lengths were constant at 10 +/- 0.2 (s.e.) micrometers. Vertex, segment and terminal frequency distributions of equivalent orders were all normal with a slight positive skew. Peak frequencies were recorded at the 12th equivalent order. The mean primary/secondary nodal vertex ratio was 0.93 and the proportion of trichotomous branch points in the tree was 5%. Comparison of the frequency distribution of all vertices with computer generated models showed that growth of the Purkinje cell was most closely simulated by a random terminal growth model, incorporating 5% trichotomy , in which the branching of high order terminals was more likely than low order terminals. It was concluded that growth of the Purkinje cell tree could proceed by random terminal branching with growth occurring preferentially over a front composed of terminals that are ascending through a corridor in the molecular layer whose margins are defined by neighbouring trees.  相似文献   
8.
9.
10.
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