全文获取类型
收费全文 | 2857篇 |
免费 | 246篇 |
国内免费 | 8篇 |
专业分类
耳鼻咽喉 | 43篇 |
儿科学 | 101篇 |
妇产科学 | 23篇 |
基础医学 | 272篇 |
口腔科学 | 108篇 |
临床医学 | 241篇 |
内科学 | 608篇 |
皮肤病学 | 87篇 |
神经病学 | 251篇 |
特种医学 | 325篇 |
外科学 | 441篇 |
综合类 | 100篇 |
预防医学 | 181篇 |
眼科学 | 31篇 |
药学 | 116篇 |
中国医学 | 26篇 |
肿瘤学 | 157篇 |
出版年
2022年 | 19篇 |
2021年 | 37篇 |
2020年 | 17篇 |
2019年 | 37篇 |
2018年 | 44篇 |
2017年 | 46篇 |
2016年 | 50篇 |
2015年 | 56篇 |
2014年 | 78篇 |
2013年 | 125篇 |
2012年 | 158篇 |
2011年 | 120篇 |
2010年 | 104篇 |
2009年 | 75篇 |
2008年 | 131篇 |
2007年 | 129篇 |
2006年 | 126篇 |
2005年 | 117篇 |
2004年 | 82篇 |
2003年 | 87篇 |
2002年 | 93篇 |
2001年 | 73篇 |
2000年 | 68篇 |
1999年 | 65篇 |
1998年 | 74篇 |
1997年 | 62篇 |
1996年 | 45篇 |
1995年 | 32篇 |
1994年 | 39篇 |
1993年 | 42篇 |
1992年 | 56篇 |
1991年 | 56篇 |
1990年 | 53篇 |
1989年 | 67篇 |
1988年 | 75篇 |
1987年 | 51篇 |
1986年 | 46篇 |
1985年 | 52篇 |
1984年 | 21篇 |
1983年 | 34篇 |
1982年 | 28篇 |
1981年 | 23篇 |
1980年 | 19篇 |
1979年 | 31篇 |
1978年 | 28篇 |
1977年 | 19篇 |
1976年 | 22篇 |
1975年 | 17篇 |
1970年 | 17篇 |
1967年 | 21篇 |
排序方式: 共有3111条查询结果,搜索用时 15 毫秒
1.
2.
3.
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
4.
5.
Aaron M Kipp Jennifer A Lehman Richard A Bowen Patricia E Fox Michael R Stephens Kaci Klenk Nicholas Komar Michel L Bunning 《The American journal of tropical medicine and hygiene》2006,75(4):688-690
To better understand the potential environmental health risk presented by West Nile virus (WNV)-contaminated feces, we quantified the amount of WNV present in the feces of experimentally infected American crows (Corvus brachyrhynchos) and fish crows (Corvus ossifragus). Peak fecal titers ranged from 10(3.5) to 10(8.8) plaque-forming units (PFU)/g for 10 American crows and from 10(2.3) to 10(6.4) PFU/g for 10 fish crows. The presence of infectious WNV in bird feces indicates a potential for direct transmission of WNV. Thus, handlers of sick or dead birds should take appropriate precautions to avoid exposure to fecal material. 相似文献
6.
7.
8.
Effect of acute tyrosine depletion in using a branched chain amino-acid mixture on dopamine neurotransmission in the rat brain. 总被引:1,自引:0,他引:1
Marisa Le Masurier Weite Oldenzeil Claire Lehman Philip Cowen Trevor Sharp 《Neuropsychopharmacology》2006,31(2):310-317
Central dopamine function is reduced by decreasing the availability of the catecholamine precursor, tyrosine, using a tyrosine-free amino acid mixture containing multiple large neutral as well as branched chain amino-acids, which compete with tyrosine for uptake into the brain. Current mixtures are cumbersome to make and administer, and unpalatable to patients and volunteers. Here, we investigate whether individual or limited amino-acid combinations could reduce brain tyrosine levels and hence dopamine function. Measurements of regional brain tyrosine levels, catecholamine and indoleamine synthesis (L-DOPA and 5-HTP accumulation, respectively) were used to identify an effective paradigm to test in neurochemical, behavioral and fos immunocytochemical models. Administration of leucine or isoleucine, or a mixture of leucine, isoleucine, and valine reduced tyrosine and 5-HTP, but not L-DOPA accumulation. A mixture of leucine, valine, and isoleucine supplemented with tryptophan reduced brain tyrosine and L-DOPA, but not 5-HTP. In microdialysis experiments this amino-acid mixture reduced basal and amphetamine-evoked striatal dopamine release, as well as amphetamine-induced hyperactivity. This mixture also reduced amphetamine-induced fos expression in striatal areas. In conclusion, the present study identified a small combination of amino acids that reduces brain tyrosine and dopamine function in a manner similar to mixtures of multiple amino acids. This minimal mixture may have use as a dopamine reducing paradigm in patient and volunteer studies. 相似文献
9.
Maxillary sinusitis in adults: an evaluation of placebo-controlled double-blind trials 总被引:1,自引:0,他引:1
BACKGROUND: In general practice, acute sinusitis is frequently diagnosed
and treated with antibiotics. OBJECTIVE: This study aimed to determine the
evidence for the effectiveness of antibiotic treatment in acute maxillary
sinusitis in adults by assessing the methodological quality of
placebo-controlled double-blind randomized trials. METHOD: An evaluation by
four raters through a 35-item scoring-scale for internal and external
validity of all placebo-controlled double-blind randomized trials on acute
sinusitis found between January 1966 and July 1996. RESULTS: Eighty-five
trials were excluded because they were not placebo-controlled,
double-blind, randomized, or were carried out in patients with chronic
sinusitis or in children. The three remaining trials were performed in
different populations (one in general practice) between 1973 and 1978. Only
one study claimed superiority of antibiotic treatment. Different inclusion
criteria and major outcome measures were used by the authors. The
reliability of major outcome events was reported poorly or not at all and
in two studies outcome measures were clinically inappropriate. The studies
scored 30-62% of the maximum attainable score for internal validity and
10-20% for external validity. CONCLUSION: The effectiveness of antibiotic
treatment in acute maxillary sinusitis in a general practice population is
not based sufficiently on evidence.
相似文献
10.