全文获取类型
收费全文 | 1347篇 |
免费 | 88篇 |
国内免费 | 10篇 |
专业分类
耳鼻咽喉 | 19篇 |
儿科学 | 73篇 |
妇产科学 | 49篇 |
基础医学 | 188篇 |
口腔科学 | 57篇 |
临床医学 | 170篇 |
内科学 | 248篇 |
皮肤病学 | 28篇 |
神经病学 | 84篇 |
特种医学 | 155篇 |
外科学 | 97篇 |
综合类 | 19篇 |
预防医学 | 83篇 |
眼科学 | 12篇 |
药学 | 76篇 |
中国医学 | 2篇 |
肿瘤学 | 85篇 |
出版年
2021年 | 12篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 18篇 |
2017年 | 18篇 |
2016年 | 16篇 |
2015年 | 18篇 |
2014年 | 20篇 |
2013年 | 36篇 |
2012年 | 48篇 |
2011年 | 48篇 |
2010年 | 39篇 |
2009年 | 33篇 |
2008年 | 56篇 |
2007年 | 57篇 |
2006年 | 58篇 |
2005年 | 51篇 |
2004年 | 44篇 |
2003年 | 42篇 |
2002年 | 41篇 |
2001年 | 13篇 |
2000年 | 16篇 |
1999年 | 19篇 |
1998年 | 51篇 |
1997年 | 66篇 |
1996年 | 49篇 |
1995年 | 38篇 |
1994年 | 41篇 |
1993年 | 31篇 |
1992年 | 31篇 |
1991年 | 24篇 |
1990年 | 11篇 |
1989年 | 27篇 |
1988年 | 37篇 |
1987年 | 37篇 |
1986年 | 38篇 |
1985年 | 33篇 |
1984年 | 30篇 |
1983年 | 14篇 |
1982年 | 17篇 |
1981年 | 21篇 |
1980年 | 13篇 |
1979年 | 8篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1976年 | 16篇 |
1975年 | 8篇 |
1973年 | 8篇 |
1971年 | 6篇 |
1960年 | 6篇 |
排序方式: 共有1445条查询结果,搜索用时 15 毫秒
1.
Christine E. Marx William T. Trost Lawrence J. Shampine Robert D. Stevens Christine M. Hulette David C. Steffens John F. Ervin Marian I. Butterfield Daniel G. Blazer Mark W. Massing Jeffrey A. Lieberman 《Neuropsychopharmacology》2006,60(12):1287-1294
BACKGROUND: Few data are currently available investigating neurosteroids (NS) in Alzheimer's disease (AD). The NS allopregnanolone may be decreased in serum and plasma in patients with AD, but it is unclear if allopregnanolone is also reduced in brain. Because a number of NS exhibit neuroprotective effects and impact cognitive performance in rodent models, these molecules may be relevant to the pathophysiology of neurodegenerative disorders. We therefore investigated prefrontal cortex (PFC) NS levels in AD. METHODS: Neurosteroid levels (allopregnanolone, pregnenolone, dehydroepiandrosterone [DHEA]) were determined in postmortem PFC in 14 male subjects with AD and 15 cognitively intact male control subjects by gas chromatography/mass spectrometry preceded by high-performance liquid chromatography purification. RESULTS: Subjects with AD exhibit significant reductions in allopregnanolone compared with cognitively intact control subjects (median levels = 2.50 ng/g vs. 5.59 ng/g, respectively; p = .02). Allopregnanolone levels are inversely correlated with neuropathological disease stage (Braak), r = -.49, p = .007. Median DHEA levels are elevated in subjects with AD (p = .01). CONCLUSIONS: Subjects with AD demonstrate significant reductions in PFC allopregnanolone levels, a finding that may be relevant to neuropathological disease stage severity. Neurosteroids may have utility as candidate biomarkers in AD. 相似文献
2.
Intracranial circulation: pulse-sequence considerations in three- dimensional (volume) MR angiography 总被引:2,自引:0,他引:2
The technique and feasibility of magnetic resonance (MR) angiography of intracranial vessels were studied in 35 healthy volunteers. Variations in image orientation, repetition time (TR), and flip angle were evaluated to determine their effects on flow-related enhancement. Gradient modifications--including echo time (TE), motion compensation, bandwidth, and field of view--were also studied in an effort to reduce motion-induced phase shifts. Results indicated that a FISP (fast imaging with steady precession) sequence with a TR of 50 msec, TE of 15 msec, velocity compensation in the read and section-select directions, acceleration compensation in the read direction, anisotropic volume, and a 1.25-mm partition thickness produced three-dimensional angiographic MR images that were accurate and reproducible in the depiction of the major intracranial vessels. Difficulties with field of view, persistent signal void secondary to higher-order motion, and spatial resolution remain major problems requiring additional study. 相似文献
3.
Reproductive Function in Epilepsy 总被引:10,自引:10,他引:0
Summary: : The hypothalamic-pituitary-gonadal axis is a complex system within which both positive and negative feedback occur among its elements and higher brain systems. The occurrence of seizures and changes in the secretion of pituitary hormones can affect the feedback loop. Both seizures and antiepileptic drugs can affect the hypothalamic-pituitary-gonadal axis of males and females and cause changes in hormones and sexuality. Reproductive dysfunction has a social impact because of reduced fertility. Once conception occurs, live birth rates are not diminished. Prospective studies of men and women with epilepsy are needed. 相似文献
4.
Paediatric dacryocystorhinostomy 总被引:1,自引:0,他引:1
KN Hakin FRCS FRCOphth TJ Sullivan FRACO FRACS A Sharma FCOphth † RAN Welham FRCS FCOphth † 《Clinical & experimental ophthalmology》1994,22(4):231-235
Of 258 cases of dacryocystorhinostomy performed on children in the period September 1981 to September 1991, 130 were for simple, unresolved congenital nasolacrimal duct obstruction. Other indications for surgery included punctal agenesis, lacrimal fistula, post-traumatic and post-inflammatory canalicular obstruction. Of 177 children without canalicular pathology, 171 (96%) were relieved of symptoms with one operation, without canalicular intubation. Of 81 cases with canalicular disease, 55 of 70 (79%) who underwent DCR plus canalicular intubation, and 10 of 11 who underwent DCR plus Lester-Jones tube, were substantially improved with one operation. No child required peroperative or postoperative blood transfusion. Dacryocystorhinostomy in childhood, in experienced surgical hands, is a safe procedure, achieving relief of symptoms in most cases, particularly in the absence of canalicular disease. 相似文献
5.
6.
7.
Pantin Hilda Coatsworth J. Douglas Feaster Daniel J. Newman Frederick L. Briones Ervin Prado Guillermo Schwartz Seth J. Szapocznik José 《Prevention science》2003,4(3):189-201
This paper reports a test of the efficacy of Familias Unidas, a Hispanic-specific, ecologically focused, parent-centered preventive intervention, in promoting protection against and reducing risk for adolescent behavior problems. Specifically, the intervention was designed to foster parental investment, reduce adolescent behavior problems, and promote adolescent school bonding/academic achievement, all protective factors against drug abuse and delinquency. One-hundred sixty seven Hispanic families of 6th and 7th grade students from three South Florida public schools were stratified by grade within school and randomly assigned to intervention and no-intervention control conditions. Results indicated that Familias Unidas was efficacious in increasing parental investment and decreasing adolescent behavior problems, but that it did not significantly impact adolescent school bonding/academic achievement. Summer-vacation rates of adolescent behavior problems were six times higher in the control condition than in the intervention condition. Furthermore, change in parental investment during the intervention was predictive of subsequent levels of adolescent behavior problems. The findings suggest that Familias Unidas is efficacious in promoting protection and reducing risk for adolescent problem behaviors in poor immigrant Hispanic families. 相似文献
8.
Factors influencing women to undergo screening mammography 总被引:2,自引:0,他引:2
9.
10.