全文获取类型
收费全文 | 7947篇 |
免费 | 652篇 |
国内免费 | 20篇 |
专业分类
耳鼻咽喉 | 74篇 |
儿科学 | 357篇 |
妇产科学 | 194篇 |
基础医学 | 976篇 |
口腔科学 | 196篇 |
临床医学 | 727篇 |
内科学 | 1829篇 |
皮肤病学 | 66篇 |
神经病学 | 908篇 |
特种医学 | 379篇 |
外科学 | 828篇 |
综合类 | 195篇 |
一般理论 | 2篇 |
预防医学 | 884篇 |
眼科学 | 128篇 |
药学 | 306篇 |
中国医学 | 24篇 |
肿瘤学 | 546篇 |
出版年
2021年 | 72篇 |
2019年 | 61篇 |
2018年 | 106篇 |
2017年 | 91篇 |
2016年 | 79篇 |
2015年 | 98篇 |
2014年 | 169篇 |
2013年 | 250篇 |
2012年 | 338篇 |
2011年 | 320篇 |
2010年 | 223篇 |
2009年 | 216篇 |
2008年 | 341篇 |
2007年 | 348篇 |
2006年 | 303篇 |
2005年 | 292篇 |
2004年 | 271篇 |
2003年 | 323篇 |
2002年 | 280篇 |
2001年 | 265篇 |
2000年 | 271篇 |
1999年 | 246篇 |
1998年 | 135篇 |
1997年 | 128篇 |
1996年 | 100篇 |
1995年 | 88篇 |
1994年 | 84篇 |
1993年 | 84篇 |
1992年 | 220篇 |
1991年 | 221篇 |
1990年 | 200篇 |
1989年 | 181篇 |
1988年 | 178篇 |
1987年 | 181篇 |
1986年 | 144篇 |
1985年 | 180篇 |
1984年 | 115篇 |
1983年 | 92篇 |
1982年 | 72篇 |
1981年 | 72篇 |
1979年 | 120篇 |
1978年 | 94篇 |
1977年 | 58篇 |
1976年 | 69篇 |
1975年 | 65篇 |
1974年 | 72篇 |
1973年 | 58篇 |
1972年 | 71篇 |
1970年 | 48篇 |
1966年 | 52篇 |
排序方式: 共有8619条查询结果,搜索用时 15 毫秒
1.
Benyam Kinde Harrison W. Gabel Caitlin S. Gilbert Eric C. Griffith Michael E. Greenberg 《Proceedings of the National Academy of Sciences of the United States of America》2015,112(22):6800-6806
DNA methylation at CpG dinucleotides is an important epigenetic regulator common to virtually all mammalian cell types, but recent evidence indicates that during early postnatal development neuronal genomes also accumulate uniquely high levels of two alternative forms of methylation, non-CpG methylation and hydroxymethylation. Here we discuss the distinct landscape of DNA methylation in neurons, how it is established, and how it might affect the binding and function of protein readers of DNA methylation. We review studies of one critical reader of DNA methylation in the brain, the Rett syndrome protein methyl CpG-binding protein 2 (MeCP2), and discuss how differential binding affinity of MeCP2 for non-CpG and hydroxymethylation may affect the function of this methyl-binding protein in the nervous system. 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.
4.
5.
Rice varieties with similar amylose content differ in starch digestibility and glycemic response in humans 总被引:7,自引:0,他引:7
L N Panlasigui L U Thompson B O Juliano C M Perez S H Yiu G R Greenberg 《The American journal of clinical nutrition》1991,54(5):871-877
Three high-amylose rice varieties, IR42, IR36, and IR62, with similar chemical composition including amylose content (26.7-27.0%), were cooked under the same conditions and tested for in vitro digestibility as well as blood glucose and insulin responses in healthy human volunteers. The starch-digestion rate and the glycemic and insulin responses were the highest in IR42, followed by IR36 and, then IR62. The differences were not due to unabsorbed carbohydrate but were related to their physicochemical properties, such as gelatinization temperature, minimum cooking time, amylograph consistency, and volume expansion upon cooking. When the three varieties were cooked for their minimum cooking time, they had the same degree of gelatinization and their starch-digestion rates and glycemic responses were similar. We conclude that amylose content alone is not a good predictor of starch-digestion rate or glycemic response. Rice varieties with similar high-amylose contents can differ in physicochemical (gelatinization) properties and this, in turn, can influence starch digestibility and blood glucose response. 相似文献
6.
7.
D Greenberg 《American journal of psychotherapy》1987,41(3):409-416
Four cases of compulsive hoarding are described, all sharing the following characteristics: (1) onset in the twenties, (2) preoccupation with hoarding to the exclusion of work and family, (3) diminished insight, (4) little interest in receiving treatment, (5) no attempt to curb their compulsion. They do not show clear psychotic features. The implications of these characteristics for the diagnosis of hoarding are discussed. 相似文献
8.
The CXC chemokine stromal cell-derived factor 1 is not responsible for CD8+ T cell suppression of syncytia-inducing strains of HIV-1
下载免费PDF全文
![点击此处可从《Proceedings of the National Academy of Sciences of the United States of America》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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.
J Morris D Schneider M R Greenberg 《Public health reports (Washington, D.C. : 1974)》1994,109(6):761-766
In a survey of the 50 State health agencies in the spring of 1992, officials were asked about their manpower and research needs in the specific areas of administration, behavioral and social science, education and information, environmental health, environmental protection, epidemiology, laboratory, law, occupational health, policy and planning, and statistics. In all, 40 agencies (80 percent) responded. Indepth telephone interviews to determine whether universities and schools and graduate programs in public health filled these needs completed the data collection process. Agency officials indicated that their resources were least adequate in environmental protection, behavioral and social science, and occupational health. They did not feel their research needs were being met. There was a general feeling that universities and schools and programs in public health have different agendas than State agencies and that practical solutions to the shortage of research resources are not forthcoming from these sources. Suggestions are made as to what can be done to improve relationships between those who train public health personnel and those who employ them. 相似文献