全文获取类型
收费全文 | 2684篇 |
免费 | 352篇 |
出版年
2023年 | 16篇 |
2022年 | 29篇 |
2021年 | 81篇 |
2020年 | 55篇 |
2019年 | 68篇 |
2018年 | 85篇 |
2017年 | 83篇 |
2016年 | 112篇 |
2015年 | 156篇 |
2014年 | 179篇 |
2013年 | 170篇 |
2012年 | 217篇 |
2011年 | 173篇 |
2010年 | 146篇 |
2009年 | 121篇 |
2008年 | 133篇 |
2007年 | 139篇 |
2006年 | 110篇 |
2005年 | 113篇 |
2004年 | 102篇 |
2003年 | 83篇 |
2002年 | 98篇 |
2001年 | 56篇 |
2000年 | 51篇 |
1999年 | 48篇 |
1998年 | 25篇 |
1997年 | 24篇 |
1996年 | 16篇 |
1995年 | 20篇 |
1994年 | 14篇 |
1993年 | 30篇 |
1992年 | 34篇 |
1991年 | 26篇 |
1990年 | 31篇 |
1989年 | 14篇 |
1988年 | 20篇 |
1987年 | 12篇 |
1986年 | 15篇 |
1985年 | 12篇 |
1984年 | 13篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 8篇 |
1975年 | 7篇 |
1974年 | 6篇 |
1973年 | 7篇 |
1972年 | 6篇 |
1971年 | 5篇 |
排序方式: 共有3036条查询结果,搜索用时 15 毫秒
1.
Amy Chapman Gonzalo Gonzales Wayne R. Burrowes Paul Assanah Bernadette Iannone Michael K. Leung George B. Stefano 《Cellular and molecular neurobiology》1984,4(2):143-155
In Mytilus and Leucophaea the high-affinity binding site density is significantly lower in old animals than in young animals, whereas the low-affinity site density remains unchanged. In Mytilus the estimated met-enkephalin and met-enkephalin-Arg6-Phe7 levels are significantly higher in old than in young animals. In Leucophaea only the met-enkephalin level can be determined, and it is also higher in old animals. The decrease in the high-affinity binding site density and the corresponding increase in endogenous enkephalin levels suggest the existence of an opioid compensatory mechanism associated with the aging process. In Mytilus there is a demonstrated decrease with age in intraganglionic dopamine levels in response to applied opiates. In addition, the inhibition of dopamine-stimulated adenylate cyclase activity by opiates also decreases in older animals. In Leucophaea the sex difference in opioid binding densities diminishes with age. 相似文献
2.
3.
4.
Serum gastrin and gastric acid secretion at high altitude 总被引:1,自引:0,他引:1
N Jó O García R Jara F Garmendia A Nago R García H Hidalgo L Flores 《Hormones et métabolisme》1987,19(4):182-183
5.
6.
The effect of chronic alcoholism on the amygdaloid complex was studied in 16 humans and 10 rats. Eighteen patients whose death was due to extraneural causes were selected as controls with 3 rats. The alcoholic cases, in addition to the data collected in their clinical history, showed, microscopically confirmed, liver cirrhosis or steatosis. The alcoholics and controls were divided into 4 groups: 35-44 years old (4 cases), 45-54 (5 cases), 55-64 (5 cases) over 65 (2 alcoholics and 4 controls). The alcoholic ingestion in the rats (Wistar, 10 weeks old) was 3 ml at a concentration of 30% in water solution administered by esophagic intubation, for 48 (5 rats) or 58 weeks (5 rats). To judge the state of the amygdaloid nuclei, a neuronal count and caryometry were carried out. The numerical data obtained in this study were analyzed statistically. The results in humans have paralleled those obtained in rats and the behaviour of the different nuclei of the amygdala was uniform and can be summarized as follows: 1) ethanol provoked a prominent and early loss of neurons, and 2) the remainder of non-affected neurons did not react in order to compensate for this neuronal loss. 相似文献
7.
8.
9.
Control of Nitrogenase mRNA Levels by Products of Nitrate Assimilation in the Cyanobacterium Anabaena sp. Strain PCC 7120 总被引:1,自引:0,他引:1
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Nitrate inhibited nitrogenase synthesis and heterocyst development in the cyanobacterium Anabaena sp. strain PCC 7120. Inhibition of dinitrogen fixation by nitrate did not take place, however, in nitrate reductase-deficient derivatives of this strain. Hybridization of total RNA isolated from cells grown on different nitrogen sources with an internal fragment of the nifD gene showed that regulation of nitrogenase activity by nitrate is exerted through a negative control of the nitrogenase mRNA levels. 相似文献
10.
C M Contreras M L Marván H Lara-Morales A Barradas L Chacón M A Guzmán-Sáenz C Márquez Flores 《Boletín de estudios médicos y biológicos》1991,39(1-4):3-8
An increased firing rate in lateral septal nuclei (LSN) appears in urethane-anesthetized rats after several acute drug and non-drug human antidepressant treatments. A still more pronounced increase in firing rate is produced in LSN after clomipramine (CMI) long-term treatment. In spite of urethane is a widely used anesthetic for single unit extracellular recordings, it modifies evoked potentials wave-form. Therefore, present study discards urethane interaction with CMI in LSN single unit extracellular recordings. CMI was acutely injected (1.25 mg/kg: IP) either to urethane-anesthetized, or non-anesthetized encephale-isolé rats. The CMI treated groups showed higher rates of firing in LSN regardless of the use of general anesthesia during recordings. Another group of urethane-anesthetized rats received intracerebroventricular (ICV) microinjections of CMI (100 micrograms/10 microliters/1 min). An amount of 42.8% of LSN-recorded neurons responded with a long-lasting increased firing rate. Results discard urethane and CMI interactions. Additionally, systemic actions of CMI on firing rate of LSN are reproduced by ICV/route microinjections. 相似文献