全文获取类型
收费全文 | 1370485篇 |
免费 | 122498篇 |
国内免费 | 1434篇 |
专业分类
1494417篇 |
出版年
2021年 | 17855篇 |
2019年 | 16123篇 |
2018年 | 17987篇 |
2017年 | 16760篇 |
2016年 | 28161篇 |
2015年 | 42250篇 |
2014年 | 50248篇 |
2013年 | 76368篇 |
2012年 | 37199篇 |
2011年 | 26169篇 |
2010年 | 43903篇 |
2009年 | 45155篇 |
2008年 | 25143篇 |
2007年 | 23201篇 |
2006年 | 28164篇 |
2005年 | 29254篇 |
2004年 | 28484篇 |
2003年 | 25874篇 |
2002年 | 24014篇 |
2001年 | 33428篇 |
2000年 | 30865篇 |
1999年 | 31042篇 |
1998年 | 25401篇 |
1997年 | 25301篇 |
1996年 | 24762篇 |
1995年 | 22927篇 |
1994年 | 22714篇 |
1993年 | 21812篇 |
1992年 | 27260篇 |
1991年 | 25809篇 |
1990年 | 24543篇 |
1989年 | 25250篇 |
1988年 | 23472篇 |
1987年 | 22368篇 |
1986年 | 21207篇 |
1985年 | 23084篇 |
1984年 | 22848篇 |
1983年 | 20226篇 |
1982年 | 20596篇 |
1981年 | 19830篇 |
1980年 | 18586篇 |
1979年 | 19042篇 |
1978年 | 17899篇 |
1977年 | 17197篇 |
1976年 | 16470篇 |
1975年 | 16009篇 |
1974年 | 16668篇 |
1973年 | 16989篇 |
1972年 | 14581篇 |
1971年 | 13363篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
291.
292.
293.
294.
295.
296.
Cynthia L. Deitrick Richard E. Katholi David J. Huddleston Kathy Hardiek Lucienne Burrus 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2001,751(2)
Vitamin B6, measured as pyridoxal 5′-phosphate (PLP), is a co-enzyme in the transsulfuration pathway of homocysteine metabolism. Since depletion of PLP has been suggested as an independent risk factor for coronary artery disease, PLP is frequently measured to guide patient care. By a change and utilization of an Aquasil C18 column and the addition of an acetonitrile clean-up gradient to the potassium phosphate, with sodium perchlorate and bisulfite buffer between samples we report the modification of a previously described method for analysis of PLP. The result is a more practical, efficient, reliable and robust method for daily clinical use. We also determined and report that it is critical to protect freshly prepared standard PLP samples from light exposure during assay preparation. 相似文献
297.
298.
We studied the impulse activity of neurons of the basal and lateral amygdalar nuclei generated when experimental animals (rats) performed fast stereotyped food-procuring movements by the forelimb. Within the basolateral amygdala, there are neurons whose activity is related to different stages of getting off the food, and according to the characteristics of their spiking these neurons should be divided into a number of subpopulations. Activation forestalling the movement initiation by 0.5-1.0 sec was observed in most neurons of the basolateral amygdala; this is considered a manifestation of excitation related to a motivation component of the food-procuring behavior. Activation of amygdalar neurons following movement initiation can result from generation in this structure of additional excitation necessary for successful performance of a complete food-procuring motor cycle. 相似文献
299.
Hugo R. Permingeat Maria V. Romagnoli Juliana I. Sesma Ruben H. Vallejos 《Plant Molecular Biology Reporter》1998,16(1):89-89
An easy, reproducible and fast procedure to isolate DNA from cotton leaves is described. The addition of 0.5 M glucose in the extraction buffer avoids browning by polyphenolic compounds and improves the quality of DNA for molecular analysis. The DNA yield ranged between 150–400 mg per gram of fresh tissue. The DNA was suitable for digestion by restriction enzymes and amplificatiion by Taq DNA polymerase. 相似文献
300.
Richard D. Gregory 《Ecography》1998,21(1):92-96