全文获取类型
收费全文 | 1335465篇 |
免费 | 99882篇 |
国内免费 | 4263篇 |
专业分类
耳鼻咽喉 | 16799篇 |
儿科学 | 43583篇 |
妇产科学 | 36356篇 |
基础医学 | 197824篇 |
口腔科学 | 35901篇 |
临床医学 | 129549篇 |
内科学 | 258059篇 |
皮肤病学 | 26375篇 |
神经病学 | 111847篇 |
特种医学 | 48172篇 |
外国民族医学 | 366篇 |
外科学 | 184019篇 |
综合类 | 28772篇 |
现状与发展 | 1篇 |
一般理论 | 462篇 |
预防医学 | 114367篇 |
眼科学 | 28978篇 |
药学 | 98824篇 |
6篇 | |
中国医学 | 3167篇 |
肿瘤学 | 76183篇 |
出版年
2021年 | 10897篇 |
2019年 | 11633篇 |
2018年 | 16316篇 |
2017年 | 12288篇 |
2016年 | 13244篇 |
2015年 | 15191篇 |
2014年 | 20797篇 |
2013年 | 32049篇 |
2012年 | 44237篇 |
2011年 | 46882篇 |
2010年 | 27074篇 |
2009年 | 24920篇 |
2008年 | 42710篇 |
2007年 | 45051篇 |
2006年 | 45162篇 |
2005年 | 43584篇 |
2004年 | 41558篇 |
2003年 | 39490篇 |
2002年 | 38301篇 |
2001年 | 60841篇 |
2000年 | 62513篇 |
1999年 | 52274篇 |
1998年 | 14578篇 |
1997年 | 13276篇 |
1996年 | 13114篇 |
1995年 | 12456篇 |
1994年 | 11625篇 |
1993年 | 10920篇 |
1992年 | 41568篇 |
1991年 | 40760篇 |
1990年 | 39446篇 |
1989年 | 37342篇 |
1988年 | 34581篇 |
1987年 | 33695篇 |
1986年 | 32150篇 |
1985年 | 30638篇 |
1984年 | 23035篇 |
1983年 | 19591篇 |
1982年 | 11752篇 |
1979年 | 20805篇 |
1978年 | 14814篇 |
1977年 | 12064篇 |
1976年 | 11877篇 |
1975年 | 12112篇 |
1974年 | 14800篇 |
1973年 | 14472篇 |
1972年 | 13357篇 |
1971年 | 12418篇 |
1970年 | 11485篇 |
1969年 | 10410篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
982.
Calcitonin gene-related peptide: functional role in cerebrovascular regulation. 总被引:14,自引:1,他引:13 下载免费PDF全文
J McCulloch R Uddman T A Kingman L Edvinsson 《Proceedings of the National Academy of Sciences of the United States of America》1986,83(15):5731-5735
Distribution studies disclosed that all major cerebral arteries and cortical arterioles of the cat were invested with fine varicose nerve fibers that contained calcitonin gene-related peptide (CGRP)-like immunoreactivity; the trigeminal ganglia likewise contained CGRP immunoreactivity. Sequential immunostaining with antibodies to CGRP and to substance P (SP) revealed identical distributions of these two peptides in trigeminal ganglia and cerebrovascular nerve fibers, suggesting that CGRP and SP are colocalized in these nerves. CGRP completely disappeared from ipsilateral blood vessels after unilateral section of the trigeminal nerve. Exogenous CGRP was a potent relaxant of feline middle cerebral arteries in vitro (maximum relaxation, 10.5 +/- 1.5 mN; concentration eliciting half-maximal response, 9.6 +/- 1.3 nM). Perivascular microapplication of CGRP to individual cortical arterioles of chloralose-anesthetized cats provoked dose-dependent dilatations (maximum increase in diameter, 38 +/- 5%; concentration eliciting half-maximal response, approximately equal to 3 nM). CGRP was significantly more potent than SP as a cerebrovascular dilator, both in vitro and in situ. Chronic division of the ipsilateral trigeminal nerve in cats did not modify the magnitude of arteriolar responses to perivascular microapplication of either vasoconstrictor or vasodilator agents, but the duration of vasoconstrictor responses to norepinephrine (0.1 mM) or alkaline solutions (pH 7.6) was significantly increased. The cerebrovascular trigeminal neuronal system, in which CGRP is the most potent vasoactive constituent, may participate in a reflex or local response to excessive cerebral vasoconstriction that restores normal vascular diameter. 相似文献
983.
984.
Russell L. Deter 《Journal of clinical ultrasound : JCU》1986,14(6):420-420
985.
Relationship between transmitter release and presynaptic calcium influx when calcium enters through discrete channels. 总被引:12,自引:2,他引:10 下载免费PDF全文
R S Zucker A L Fogelson 《Proceedings of the National Academy of Sciences of the United States of America》1986,83(9):3032-3036
We have used a three-dimensional diffusion model of calcium entering the presynaptic nerve terminal through discrete channels to simulate experiments relating transmitter release to presynaptic calcium current. The relationship will be less than linear, or will curve downward, if calcium channels are well separated. It will resemble a power-law function with exponent less than the cooperativity of calcium action if channels are clustered closer together. Large presynaptic depolarizations elicit more release than small depolarizations admitting the same calcium influx. This occurs because large pulses open more channels near each other, with the result that the calcium concentration near release sites is greater, due to overlap of calcium diffusing from adjacent channels. 相似文献
986.
S Pampfer L Vankrieken E Loumaye R De Hertogh K Thomas 《Human reproduction (Oxford, England)》1989,4(4):396-402
Follicular fluids from eight patients with one ovary and from ten patients with two ovaries were investigated for bioactive inhibin, total renin, oestradiol (E2) and progesterone (P4) concentrations. Four follicular fluids were pooled per patient before assessment. All women had been stimulated similarly using a protocol including a GnRH agonist, HMG and HCG. Renin levels were significantly lower and P4 significantly higher in pools of follicular fluid from patients with one ovary, whereas inhibin and E2 concentrations were similar in both patient groups. A significant negative correlation was found in the pools of follicular fluid between inhibin and E2 in both groups. These results suggest a role for inhibin and renin in the paracrine and autocrine control of stimulated follicular development. 相似文献
987.
988.
A 16-year-old boy, the only affected member of the family, noticed early onset contracture of the elbows, and developed slowly progressive humeroperoneal weakness and atrophy, and bilateral equinus. The severe restriction of the forward flexion of the neck and thoracolumbar spine, resembled a rigid spine syndrome. An electrocardiogram showed atrioventricular conduction abnormalities. Muscle biopsy was consistent with mild myopathy. The overall conventional findings of a detailed electromyographic study in the limbs and erector trunci muscles, as well as the results of conduction velocity, automatic analysis of the voluntary pattern and single fiber electromyography studies were consistent with myopathy, although some atypical findings were found. The controversy about neurogenic and myopathic features in Emery-Dreifuss disease is discussed. The unspecific value of the flexion limitation of the spine, and the uncertain nosological position of the rigid spine syndrome are also commented. 相似文献
989.
I L Gibbins 《Neuroscience letters》1989,107(1-3):45-50
Retrograde axonal tracing and double-labelling immunofluorescence have been combined to determine the neuropeptide content of identified pilomotor neurons in the superior cervical ganglion of guinea pigs. These neurons lacked immunoreactivity to neuropeptide Y (NPY) but they generally contained low levels of immunoreactivity to prodynorphin-derived peptides, including dynorphin A(1-8), dynorphin A(1-17), and alpha-neo-endorphin. Thus pilomotor neurons are neurochemically distinct from superior cervical ganglion cells which contain immunoreactivity to NPY and prodynorphin-derived peptides and which innervate the iris and most of the vasculature in the head of guinea pigs. They are also distinct from sympathetic secretomotor neurons which lack both NPY and prodynorphin-derived peptides. 相似文献
990.
Behavioral neurology of multi-infarct dementia 总被引:2,自引:0,他引:2
Multi-infarct dementia (MID) is a heterogeneous entity in which a variety of cerebrovascular disorders leads to intellectual impairment. A variety of patterns of behavioral changes may be observed in MID, depression, psychosis, and personality change are common. The neurobehavioral syndromes of MID are determined by the specific arteries involved and the location and extent of tissue infarction. 相似文献