全文获取类型
收费全文 | 2069篇 |
免费 | 288篇 |
出版年
2021年 | 23篇 |
2018年 | 18篇 |
2016年 | 27篇 |
2015年 | 46篇 |
2014年 | 55篇 |
2013年 | 90篇 |
2012年 | 93篇 |
2011年 | 97篇 |
2010年 | 45篇 |
2009年 | 59篇 |
2008年 | 66篇 |
2007年 | 79篇 |
2006年 | 81篇 |
2005年 | 77篇 |
2004年 | 71篇 |
2003年 | 57篇 |
2002年 | 59篇 |
2001年 | 42篇 |
2000年 | 55篇 |
1999年 | 44篇 |
1998年 | 31篇 |
1997年 | 26篇 |
1996年 | 21篇 |
1995年 | 26篇 |
1994年 | 20篇 |
1993年 | 22篇 |
1992年 | 41篇 |
1991年 | 44篇 |
1990年 | 53篇 |
1989年 | 38篇 |
1988年 | 43篇 |
1987年 | 36篇 |
1986年 | 47篇 |
1985年 | 55篇 |
1984年 | 37篇 |
1983年 | 33篇 |
1982年 | 32篇 |
1981年 | 31篇 |
1980年 | 24篇 |
1979年 | 33篇 |
1978年 | 40篇 |
1977年 | 30篇 |
1976年 | 25篇 |
1975年 | 28篇 |
1974年 | 24篇 |
1973年 | 29篇 |
1972年 | 22篇 |
1971年 | 20篇 |
1970年 | 21篇 |
1969年 | 18篇 |
排序方式: 共有2357条查询结果,搜索用时 15 毫秒
1.
2.
Transport of zinc and manganese to developing wheat grains 总被引:11,自引:0,他引:11
An understanding of the transport pathway used by Zn and Mn to enter developing grains may allow measures to increase the Zn and Mn content of wheat grain grown on Zn/Mn deficient soils. For this reason, transport of Zn and Mn into developing grains of wheat ( Triticum aestivum L. cv. Aroona) was investigated. Detached ears (18–22 days post-anthesis) were cultured for 48 h in a solution containing 185 kBq of 65 Zn and 185 kBq of 54 Mn. Transport of 65 Zn to the grain was unaffected by removal of glumes but was slightly reduced after the lemma was removed. Heat girdling the peduncle slightly reduced the amount of 65 Zn transported to the grain, whilst heat girdling the rachilla reduced transport of 65 Zn to the grain to a greater degree, suggesting phloem transport to the rachilla. The transport inhibitor CCCP (carbonyl cyanide m -chlorophenyl hydrazone) blocked 65 Zn transport to grain but not to lemma and glumes. Removing glumes and lemma and heat girdling the peduncle did not affect transport of 54 Mn, but transport was slightly affected by heat girdling the rachilla, indicating xylem transport. CCCP blocked transport of 54 Mn into the grain but not to lemma and glumes. It was concluded that xylem-to-phloem transfer of Zn occurs in the rachis and to a lesser extent in peduncle and lemma. The results suggest that the lemma may be an important site for phloem loading when the concentration of Zn within the xylem is high. The data also suggest that Mn was predominantly translocated to the spikelets in the xylem, but that transport to the grain was dependent upon membrane transport before entering the grain. Phloem loading of Mn into the grain vascular system may have occurred at the site of xylem discontinuity in the floral axis. 相似文献
3.
4.
5.
6.
7.
8.
9.
This paper reviews hypotheses about roles of angiogenesis in the pathogenesis of inflammatory disease in two organs, the synovial joint and the lung. Neovascularisation is a fundamental process for growth and tissue repair after injury. Nevertheless, it may contribute to a variety of chronic inflammatory diseases, including rheumatoid arthritis, osteoarthritis, asthma, and pulmonary fibrosis. Inflammation can promote angiogenesis, and new vessels may enhance tissue inflammation. Angiogenesis in inflammatory disease may also contribute to tissue growth, disordered tissue perfusion, abnormal ossification, and enhanced responses to normal or pathological stimuli. Angiogenesis inhibitors may reduce inflammation and may also help to restore appropriate tissue structure and function. 相似文献
10.
Sixteen patients with an early dense hemiplegia due to cerebrovascular accidents were shown to have a greater degree of hypoxia than 16 matched control patients. The patients with hemiplegia had a reflex compensatory fall in arterial carbon dioxide tensions (PaCO2) with possible reduction in cerebral blood flow. Oxygen treatment led to an increase in PaCO2 in the patients with hemiplegia, but the increase in oxygen tensions in these patients was significantly less than that in the control group, suggesting increased pulmonary shunting as the cause for the hypoxia. Oxygen treatment may improve cerebral blood flow and oxygenation and have a useful role in the early management of patients with a dense hemiplegia. 相似文献