全文获取类型
收费全文 | 1031篇 |
免费 | 42篇 |
国内免费 | 6篇 |
专业分类
耳鼻咽喉 | 8篇 |
儿科学 | 40篇 |
妇产科学 | 6篇 |
基础医学 | 104篇 |
口腔科学 | 37篇 |
临床医学 | 92篇 |
内科学 | 173篇 |
皮肤病学 | 11篇 |
神经病学 | 150篇 |
特种医学 | 241篇 |
外科学 | 43篇 |
综合类 | 22篇 |
预防医学 | 28篇 |
眼科学 | 15篇 |
药学 | 68篇 |
肿瘤学 | 41篇 |
出版年
2021年 | 4篇 |
2020年 | 6篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 7篇 |
2015年 | 13篇 |
2014年 | 17篇 |
2013年 | 24篇 |
2012年 | 25篇 |
2011年 | 17篇 |
2010年 | 34篇 |
2009年 | 35篇 |
2008年 | 23篇 |
2007年 | 35篇 |
2006年 | 23篇 |
2005年 | 30篇 |
2004年 | 26篇 |
2003年 | 22篇 |
2002年 | 24篇 |
2001年 | 18篇 |
2000年 | 13篇 |
1999年 | 14篇 |
1998年 | 48篇 |
1997年 | 63篇 |
1996年 | 57篇 |
1995年 | 55篇 |
1994年 | 49篇 |
1993年 | 30篇 |
1992年 | 20篇 |
1991年 | 14篇 |
1990年 | 20篇 |
1989年 | 21篇 |
1988年 | 36篇 |
1987年 | 19篇 |
1986年 | 32篇 |
1985年 | 33篇 |
1984年 | 16篇 |
1983年 | 21篇 |
1982年 | 21篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 12篇 |
1976年 | 20篇 |
1975年 | 6篇 |
1973年 | 2篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1969年 | 4篇 |
排序方式: 共有1079条查询结果,搜索用时 31 毫秒
1.
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.
S. Shaikh D. A. Collier P. Sham L. Pilowsky T. Sharma L. K. Lin M. A. Crocq M. Gill R. Kerwin 《American journal of medical genetics. Part A》1995,60(6):541-545
We have examined the hypothesis that a variable number of tandem repeats in the third cytoplasmic loop of the dopamine D4 receptor influences clinical response to clozapine using a sample of 189 schizophrenic patients. Alleles of the 48-bp repeat, which range from two to ten copies in the normal human population, were analysed by the polymerase chain reaction using genomic DNA as template. Association between these alleles and response to clozapine was tested using the difference in pre-and post-treatment GAS scores as a measure of response. We found no statistically significant variation between genotypic groups and response by analysis of variance. We conclude that the variation of the number of 48-bp repeats alone does not determine response to clozapine. Larger studies are underway to determine if there is a more subtle relationship with sequence variation within the repeats or at other polymorphic sites within the gene that may provide evidence for a component of clozapine's action being at D4 receptors. © 1995 Wiley-Liss, Inc. 相似文献
5.
6.
Geraldo F. Busatto Lyn S. Pilowsky Durval C. Costa John Mertehs Dirk Terriere Peter J. Ell Rachel Mulligan Michael J. Travis Josée E. Leysen Dominic Lui Sveto Gacinovic Wendy Waddington Anne Lingford-Hughes Robert W. Kerwin 《European journal of nuclear medicine and molecular imaging》1997,24(2):119-124
The mapping of 5-HT2 receptors in the brain using functional imaging techniques has been limited by a relative lack of selective radioligands.
Iodine-123 labelled 4-amino-N-[1-[3-(4-fluorophenoxy)propyl]-4-methyl-4-piperidinyl]-5-iodo-2-methoxybenzamide (123I-5-I-R91150 or123I-R93274) is a new ligand for single-photon emission tomography (SPET), with high affinity and selectivity for 5-HT2A receptors. This study reports on preliminary123I-5-I-R91150 SPET, wholebody and blood distribution findings in five healthy human volunteers. Maximal brain uptake was approximately
2% of total body counts at 180 min post injection (p.i.). Dynamic SPET sequences were acquired with the brain-dedicated, single-slice
multi-detector system SEM-810 over 200 min p.i. Early peak uptake (at 5 min p.i.) was seen in the cerebellum, a region free
from 5HT2A receptors. In contrast, radioligand binding in the frontal cortex increased steadily over time, up to a peak at approximately
100–120 min p.i. Frontal cortex-cerebellum activity ratios reached values of 1.4, and remained stable from approximately 100
min p.i. onwards. Multi-slice SPET sequences showed a pattern of regional variation of binding compatible with the autoradiographic
data on the distribution of 5-HT2A receptors in (cerebral cortex>striatum>cerebellum). These findings suggest that123I-5-I-R91150 may be used for the imaging of 5-HT2A receptors in the living human brain with SPET. 相似文献
7.
Ralls PW; Johnson MB; Kanel G; Dobalian DM; Colletti PM; Boswell WD Jr; Radin DR; Halls JM 《Radiology》1986,161(2):451-454
FM sonography - a signal-processing technique that uses frequency and phase information as well as amplitude data - shows promise in evaluation of patients with diffuse liver disease. In a prospective blinded review of 37 patients with biopsy-proved liver disease and 42 healthy volunteers, FM sonography was clearly superior to traditional amplitude-based (AM) sonography in distinguishing healthy from diseased subjects. Statistically significant differences were seen in accuracy (FM, 98.7%; AM, 84.8%), sensitivity (FM, 97.3%; AM, 70.3%), and negative predictive value (FM, 97.7%; AM, 78.8%). Our data also suggest that current FM sonographic techniques cannot differentiate among histologic findings associated with different hepatic parenchymal abnormalities. It is unclear, therefore, whether FM imaging can reduce the numbers of patients who require biopsy for diagnosis or the frequency of biopsy procedures in patients with known disease. 相似文献
8.
Objective . To describe the importance of migraine in Santiago, Chile, by analyzing its prevalence, clinical features and impact by age, gender and socioeconomic status. Methods . In 1993, a representative sample of 1,540 adults of the province of Santiago were interviewed using a standard questionnaire. A total of 1,385 (89.9%) subjects responded to the survey. Initially, a designated member of each household responded to the questionnaire. Subsequently, each household member with headaches was asked to respond to questions about severity, frequency, location, duration, associated symptoms and impact in work and social activities of their most frequent headaches. Migraine diagnoses were determined in accordance with the International Headache Society (IHS) criteria of 1988. Results. Recurrent headaches in the past year were found in 516 (36.82%) respondents, 145 (28.1%) males and 371 (71.9%) females. Total prevalence of migraine was found to be 7.3% (95%, CI 5.9–8.6); 11.9% (95% CI 9.6–14.2) in females and 2.0% (95% CI 0.9–3.0) in males. Overall, migraine constituted 19.6% (101/516) of all headaches reported in this sample. The prevalence did not vary significantly by age groups or socioeconomic status (SES). Migraine with aura had an overall prevalence of 3.5% (CI 0.8–7.1), and was significantly more frequent in females. In 60–70% of cases the attacks lasted 2–6 h and the frequency was 3.3 and 3.4 per month in females and males respectively. Both males and females reported significantly high percentages of attacks during work. Conclusions . Migraine prevalence in a sample of adults of Santiago is similar to that reported in previous studies using IHS criteria. Women of all socioeconomic levels are at an increased risk. 相似文献
9.
10.