全文获取类型
收费全文 | 19426篇 |
免费 | 1390篇 |
国内免费 | 1篇 |
出版年
2021年 | 138篇 |
2020年 | 124篇 |
2019年 | 125篇 |
2018年 | 330篇 |
2017年 | 268篇 |
2016年 | 488篇 |
2015年 | 841篇 |
2014年 | 771篇 |
2013年 | 1166篇 |
2012年 | 1400篇 |
2011年 | 1349篇 |
2010年 | 784篇 |
2009年 | 626篇 |
2008年 | 1203篇 |
2007年 | 1180篇 |
2006年 | 1141篇 |
2005年 | 1066篇 |
2004年 | 998篇 |
2003年 | 924篇 |
2002年 | 854篇 |
2001年 | 402篇 |
2000年 | 413篇 |
1999年 | 357篇 |
1998年 | 166篇 |
1997年 | 139篇 |
1996年 | 123篇 |
1995年 | 131篇 |
1994年 | 120篇 |
1993年 | 103篇 |
1992年 | 223篇 |
1991年 | 225篇 |
1990年 | 208篇 |
1989年 | 151篇 |
1988年 | 172篇 |
1987年 | 140篇 |
1986年 | 133篇 |
1985年 | 127篇 |
1984年 | 112篇 |
1983年 | 93篇 |
1982年 | 86篇 |
1981年 | 113篇 |
1980年 | 75篇 |
1979年 | 115篇 |
1978年 | 106篇 |
1977年 | 82篇 |
1976年 | 93篇 |
1975年 | 79篇 |
1974年 | 92篇 |
1973年 | 69篇 |
1971年 | 76篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
At least nine monoclonal antibodies against phytochrome from Pisum sativum L. and 20 against phytochrome from Avena sativa L. have been obtained from mouse hybridomas that were produced by fusion of spleen cells with SP 2/O-Ag14 myeloma cells. Hybridomas were selected and cloned in a single step by plating on a semisolid methylcellulose medium. Eight antibodies to Pisum and one to Avena phytochrome were immunopurified from hybridoma medium or ascitic fluid. When necessary, secreted antibodies were verified to be against phytochrome by demonstrating to be against phytochrome by demonstrating immunoadsorption of phytochrome, detected as loss of photoactivity and-or by appearance of the approx. 120,000-dalton phytochrome band upon sodium dodecyl sulfate polyacrylamide gel electrophoresis. 相似文献
172.
We have developed and used a sensitive and specific radioimmunoassay to demonstrate the presence of CRF-like immunoreactivity in extra-hypothalamic areas of ovine brain. Synthetic CRF displaced antibody bound tracer at an ED50 value of 200 pg and there was no cross-reactivity with LHRH, TRH, ACTH, beta-endorphin and several other peptides. Displacement of bound 125I-CRF by brain extracts exhibited curves parallel to synthetic CRF standards. Highest concentrations (1 ng/mg tissue) of CRF-like immunoreactivity were found in the median eminence but surprisingly, high concentrations of CRF-like immunoreactivity were found in frontal, parietal, occipital and particularly temporal areas of cerebral cortex. Much lower concentrations were found in other brain areas including the basal ganglia, limbic system and brain stem. 相似文献
173.
174.
175.
176.
Summary We have described some characteristics of Lolium multiflorum cultivated under very short photoperiods (2 hours and 1 hour). The estimations of leaf growth were based on dry weight, surface measurements, and chlorophyll content. The pigment analyses were carried out by column chromatography; chloroplast ultrastructure was observed after chemical fixation.These measurements have permitted us to note a sharp drop in the growth curve of plants grown under different day-lengths: the limiting photoperiod lies between 1 hour and 2 hours of daily illumination.Pigment analyses and chloroplast ultrastructure observations show that there is a greater difference between plants cultivated under 1 hour and 2 hours of daily illumination than between plants cultivated under 2 hours and 12 hours.A decrease in day-length causes a deficit in the chlorophyll b content as well as a poor development of the grana.We have attempted to correlate these structural anomalies with the abnormal chlorophyll a/chlorophyll b ratio. 相似文献
177.
178.
179.
180.