全文获取类型
收费全文 | 275篇 |
免费 | 17篇 |
出版年
2022年 | 2篇 |
2021年 | 3篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 13篇 |
2012年 | 13篇 |
2011年 | 15篇 |
2010年 | 15篇 |
2009年 | 10篇 |
2008年 | 15篇 |
2007年 | 11篇 |
2006年 | 14篇 |
2005年 | 12篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 9篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 5篇 |
1992年 | 4篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1971年 | 3篇 |
1970年 | 5篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1943年 | 1篇 |
1855年 | 5篇 |
排序方式: 共有292条查询结果,搜索用时 31 毫秒
1.
Corolla expansion inIpomoea nil appears to be triggered by changes in gibberellin concentration and ethylene production during development. We investigated the role of responsiveness to GA and ethylene in corolla expansion. The effects of growth regulators applied in vitro were measured as a change in area of corolla segments from younger (15–17 mm) and older (18–20 mm) whole corollas. Applied gibberellic acid (GA3) significantly (p < 0.05) promoted growth in the younger segments but was less effective in the older segments. Moreover, applications of the GA biosynthesis inhibitors, PP333 (paclobutrazol) AMO1618 (2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidinecarboxylate methyl chloride), chlorocholine chloride, and tetcyclasis had little effect on younger segments but inhibited growth of older segments. The older corollas have apparently synthesized and accumulated enough GA-like substances to become less responsive to additional applied GA3. The amount of growth induced by applied or endogenous GA depended on the amount of ethylene simultaneously produced in the tissue. The younger corollas rapidly produced ethylene from endogenous 1-aminocyclopropane-1-carboxylic acid (ACC) and did not respond to applied ACC whereas the older corollas naturally produced much less ethylene and were significantly (p < 0.05) inhibited by applied ACC. When ethylene production was inhibited by applying aminoethoxyvinylglycine (AVG), growth was promoted in all segments. However, only the growth of the younger segments was further stimulated by simultaneously applied AVG and GA3 over the GA3 control. Thus the differential responses of segments from 15- to 20-mm long corollas to applied growth regulators reflect developmental changes in responsiveness of the developing corolla. The change in responsiveness is attributed in part to the changes in production of endogenous growth regulators and to the effect of one endogenous plant growth regulator (PGR) on the responsiveness of the corolla to another PGR. 相似文献
2.
3.
M G Dunlop T F Beattie G K White G M Raab R I Doull 《BMJ (Clinical research ed.)》1986,293(6547):603-605
A prospective study was performed to establish definitive guidelines for selective use of radiography in the assessment of inversion ankle injuries. Five hundred patients were included, representing 3.2% of the workload of the department during the study period. There were 379 soft tissue injuries, 56 malleolar fractures, 40 avulsion fractures, 21 fractures at the base of the fifth metatarsal, and four calcaneal fractures. Multiple logistic regression identified distal fibular tenderness, age, and ability to bear weight as the most important clinical variables in predicting important fractures (p less than 0.001). A policy of requesting x ray examination of only those patients with distal fibular tenderness or inability to bear weight or aged over 60, with a further proviso that no foot radiographs should be obtained, would produce a 60% reduction in ankle radiography in this centre without detriment to patient care. 相似文献
4.
The effects of a 10-wk training regimen on the mechanical properties of the femur and humerus were evaluated in 2.5- and 25-mo-old Fischer 344 female rats. The rats trained on a rodent treadmill 5 days/wk for 10 wk. Duration, grade, and speed increased until the rats maintained 1 h/day at 15% grade and either 15 m/min (old rats) or 36 m/min (young rats). Excised bones were mechanically tested with a 3-point flexure test for mechanical properties of force, stress, and strain. Fat-free dry weight (FFW) and moment of inertia were also obtained. With aging, similar increases were observed in both the femur and humerus for FFW, moment of inertia, and force. Ultimate stress was reduced in the senescent femur while strain was elevated; a similar but nonsignificant trend was observed in the humerus. Irrespective of age, training increased FFW in the femur and, to a lesser degree, in the humerus. Breaking force was elevated for both bones after training. In young and old bones, the training-induced differences in bone mass and force were similar, despite differences in training intensity. In the old trained rats, femur ultimate stress was greater than that in control rat femurs and similar to that in young rat femurs. The results of the present study indicate that training effects were not limited by age. 相似文献
5.
6.
D L Smith M S Berkowitz D Potoczak M Krause C Raab F Quinn F P Doerder 《The Journal of protozoology》1992,39(3):420-428
In the ciliate protist Tetrahymena thermophila the L, H, T, I, S, M and P cell surface proteins (immobilization antigens) are expressed under different conditions of temperature (L, H, T), culture media (I, S), and mutant genotype (M, P). Immunoblot and autoradiographic studies using antisera to purified protein show that the molecular weights of these proteins range from 25,000 to 59,000. The H, T, S, M and P antigens are recognized as single polypeptides, whereas L, I, and one allelic form of T each appear to consist of a family of polypeptides. Although antisera are specific in immobilization and immunofluorescence assays of surface protein in living cells, cross-reactivity is seen with denatured protein on immunoblots. It is hypothesized that the surface protein genes are organized into families of evolutionarily related isoloci. 相似文献
7.
8.
Intercellular communication in the rat anterior pituitary gland: an in vivo and in vitro study 总被引:3,自引:1,他引:2 下载免费PDF全文
The concept of "stimulus-secretion coupling" suggested by Douglas and co-workers to explain the events related to monamine discharge by the adrenal medulla (5, 7) may be applied to other endocrine tissues, such as adrenal cortex (36), pancreatic islets (4), and magnocellular hypothalamic neurons (6), which exhibit a similar ion-dependent process of hormone elaboration. In addition, they share another feature, that of joining neighbor cells via membrane junctions (12, 26, and Fletcher, unpublished observation). Given this, and the reports that hormone secretion by the pars distalis also involves a secretagogue-induced decrease in membrane bioelectric potential accompanied by a rise in cellular [Ca++] (27, 34, 41), it was appropriate to test the possibility that cells of the anterior pituitary gland are united by junctions. 相似文献
9.
10.
Achim Raab 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1970,68(3):272-275
Summary The present method permits rapid and sensitive study of the concentration levels of serotonin (5-HT) and 5-hydroxyindolacetic acid (5-HIAA) in the same tissue sample and the determination of the turnover of these substances in small brain parts.I wish to thank Merck Sharp and Dohme for supplies of probenecid. 相似文献