全文获取类型
收费全文 | 2583271篇 |
免费 | 189053篇 |
国内免费 | 7558篇 |
专业分类
耳鼻咽喉 | 34272篇 |
儿科学 | 85196篇 |
妇产科学 | 71568篇 |
基础医学 | 363564篇 |
口腔科学 | 69646篇 |
临床医学 | 234500篇 |
内科学 | 515487篇 |
皮肤病学 | 62450篇 |
神经病学 | 213454篇 |
特种医学 | 99877篇 |
外国民族医学 | 736篇 |
外科学 | 386409篇 |
综合类 | 50390篇 |
现状与发展 | 5篇 |
一般理论 | 968篇 |
预防医学 | 196163篇 |
眼科学 | 56663篇 |
药学 | 187975篇 |
8篇 | |
中国医学 | 5331篇 |
肿瘤学 | 145220篇 |
出版年
2021年 | 19976篇 |
2019年 | 20620篇 |
2018年 | 29284篇 |
2017年 | 22591篇 |
2016年 | 26223篇 |
2015年 | 29499篇 |
2014年 | 40437篇 |
2013年 | 60421篇 |
2012年 | 80221篇 |
2011年 | 84478篇 |
2010年 | 51002篇 |
2009年 | 49141篇 |
2008年 | 79017篇 |
2007年 | 83831篇 |
2006年 | 85563篇 |
2005年 | 81725篇 |
2004年 | 78719篇 |
2003年 | 76044篇 |
2002年 | 73329篇 |
2001年 | 128407篇 |
2000年 | 131330篇 |
1999年 | 110497篇 |
1998年 | 31252篇 |
1997年 | 27921篇 |
1996年 | 28219篇 |
1995年 | 27383篇 |
1994年 | 25068篇 |
1993年 | 23420篇 |
1992年 | 85162篇 |
1991年 | 81563篇 |
1990年 | 78783篇 |
1989年 | 76059篇 |
1988年 | 69468篇 |
1987年 | 67996篇 |
1986年 | 63542篇 |
1985年 | 60510篇 |
1984年 | 44940篇 |
1983年 | 37943篇 |
1982年 | 22456篇 |
1981年 | 19984篇 |
1979年 | 38959篇 |
1978年 | 27439篇 |
1977年 | 23252篇 |
1976年 | 21495篇 |
1975年 | 22813篇 |
1974年 | 26786篇 |
1973年 | 25370篇 |
1972年 | 23749篇 |
1971年 | 21955篇 |
1970年 | 20183篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Changes on serial assessments of brain MRI lesion load are used for monitoring therapeutic efficacy in patients with multiple
sclerosis (MS). We assessed the accuracy and reliability of conventional spin-echo (CSE) and fast spin-echo (FSE) sequences
for measurement of lesion volume using a semiautomated contour technique. Cranial CSE and FSE examinations of 18 patients
with secondary progressive MS were studied. The mean lesion load was slightly higher with the CSE sequence (p = 0.002). Intraobserver
variability was significantly higher for FSE than for CSE, according to both the coefficient of variation between two measurements
(mean 2.48 % and 1.35 % respectively, p < 0.05) and back-transformed 95 % limits of agreement (1.005–1.060 for FSE; 0.988–1.019
for CSE). Although FSE sequences are quicker and the total lesion volume measurements are similar to those obtained with CSE,
the poorer reproducibility raises doubts about the use of FSE to replace CSE in clinical trials.
Received: 26 March 1996 Accepted: 4 April 1996 相似文献
992.
993.
David A. Rothenberger M.D. 《Diseases of the colon and rectum》1997,40(5):632-635
994.
Is colonic electrical activity a similar phenomena to small-bowel electrical activity? 总被引:4,自引:0,他引:4
Dr. José A. S. Medeiros M.D. Ph.D. Fausto A. Pontes M.D. Ph.D. Octávio A. R. O. Mesquita 《Diseases of the colon and rectum》1997,40(1):93-99
PURPOSE: This study was designed to investigate colonic spike bursts regarding 1) their migration behavior, 2) their pressure correlates, and 3) comparing colonic short spike bursts with spike bursts from migrating myoelectric complex from the small bowel. METHODS: Rectosigmoid electromyography and manometry were recorded simultaneously in seven normal volunteers and electromyography alone in five others during two hours of fasting and for two hours after one 2,100-kJ meal. One patient with an ileostomy was also studied by the same method to record the migrating myoelectric complex from the terminal ileum during fasting. RESULTS: Three kinds of spike bursts were observed in the pelvic colon: rhythmic short spike bursts, migrating long spike bursts, and nonmigrating long spike bursts. The meal significantly increased the number of migrating and nonmigrating long spike bursts (from 25 to 38.7 percent of the recording time;
P
<0.01). These bursts of potentials showed a peak 15 minutes after the meal, which may be caused by the gastrocolic reflex. Migrating long spike bursts started anywhere along the rectosigmoid and migrated from there aborad 82 percent of the time and orad or in both directions in 10 or 7 percent of the time, respectively. They originated pressure waves 99 percent of the time. Short spike bursts were more frequent before the meal (15.1 percent before and 9.6 percent after the meal), but the difference was not significant; they neither propagated nor initiated pressure waves detected by the miniballoon. CONCLUSIONS: Migrating long spike bursts were the only potentials that migrated, sometimes for short distances. Short spike bursts are a different phenomenon from the small-bowel migrating myoelectric complex because they do not migrate; they can occur during the postprandial period and never originated intraluminal pressure waves.Supported by a grant from the Instituto Nacional de Investigação Científica, Proc. DBI-22086.Presented at the meeting of the Portuguese Congress of Gastrenterology, Vila Moura, Portugal, June 2 to 5, 1993. 相似文献
995.
996.
Bullous pemphigoid in association with cutaneous lesions specific to a myelodysplastic syndrome 总被引:1,自引:0,他引:1
P. MODIANO S. REICHERT A. BARBAUD P. BERNARD† M. WEBER J.L. SCHMUTZ 《The British journal of dermatology》1997,136(3):402-405
Specific cutaneous lesions are a rare occurrence in myelodysplastic syndromes (MDS). The concurrent association of blistering skin lesions similar to those in bullous pemphigoid (BP), even though a rare event, suggests that BP may be a paraneoplastic syndrome. We report an 86-year-old man who had a refractory anaemia with excess bone marrow blasts in transformation, who developed a generalized pruritic blistering eruption. Immunohistopathological tests showed subepidermal blisters with linear deposits of IgG and C3 along the basement membrane zone of the epidermis surrounding a tumoral dermal infiltrate of CD13+ and CD15+ cells. Immunoblotting studies using epidermal extracts revealed circulating IgG antibodies against three protein bands: a 210–215 kDa band. a 180kDa band which co-migrated with the BP 180 antigen, and a 190kDa band. The tumour infiltrate may have revealed antigenic determinants which led to the onset of BP. The concept of paraneoplastic pemphigoid remains to be either confirmed or invalidated by further epidemiological studies. 相似文献
997.
Bone mineral density in patients with atopic dermatitis 总被引:1,自引:0,他引:1
With the aim of evaluating the systemic effect of glucocorticoids (GCs), we measured bone mineral density (BMD) in 29 adult patients with chronic atopic dermatitis. BMD was measured in the lumbar spine and in the left femoral neck using dual–energy X–ray absorptiometry (DEXA). In the right calcaneus. BMD was measured using broad–spectrum ultrasound attenuation (BUA). For BMD, the patients with dermatitis did not differ from healthy controls. We did not find any statistically significant correlation between BMD and single risk factors, such as the barrier function of the skin (P = 0.08), the duration of the dermatitis (P = 0.58), and the use of oral GCs (P = 0.27) and potent topical GCs (P = 0.10). However, selected patients with severe disease, needing topical GCs of higher potency than hydrocortisone (HC), had lower values for lumbar BMD than the patients who had not used these preparations (–1.0 vs. +0.1 SD; P = 0.026). The lower lumbar BMD in this group could be explained by a long-term systemic effect of GCs. 相似文献
998.
J. Viac C. Goujon L. Misery V. Staniek M. Faure D. Schmitt A. Claudy 《Photodermatology, photoimmunology & photomedicine》1997,13(3):103-108
Ultraviolet radiation B (UVB) on the skin induces erythema, inflammation and modifications of the immune system. These changes have been reported after excessive short-term or long-term exposure to broad spectrum UVB. In this study, we examined the effects of local repetitive UVB irradiation of 311 nm wavelength on the skin of seven young volunteers. Skin biopsies were taken before and after UVB irradiation, and we immunohistochemically analyzed the expression of CD1a and HLA-DR antigens of Langerhans cells (LC), the possible infiltration of dermis/epidermis by CD11b macrophages, the modifications or the induction of intercellular adhesion molecule-1 (ICAM-1), E-selectin and vascular cell adhesion molecule-1 (VCAM-1) involved in the binding of leukocytes to the endothelial surface and the development of perivascular infiltrates of LFA-1+ mononuclear cells. We also determined the expression of substance P receptors (SPR) using biotinylated substance P (SPB). Exposure of UVB 311 nm induced a drastic reduction of CD1a+ cells and a moderate increase of HLA-DR+ dendritic cells in the epidermis without infiltration by CD11b macrophages. An increase of the binding of SPB to upper layer epidermal cells was noted in five of seven biopsies. In the dermis, vessel-associated ICAM-1 expression increased and an induction of E-selectin occurred on nearly 20 to 40% of endothelial cells, but VCAM-1 expression remained undetectable. The percentage of LFA-1+ cells did not change significantly after irradiation. These observations may be compatible with a selective role of UVB 311 nm on the skin immune response. 相似文献
999.
The objective of this article is to describe various radiographic projections which can be used during endodontic therapy. Changes to the angulation of the X-ray beam in relation to the teeth and film can help diagnosis and treatment by producing images which provide additional information not always visible on radiographs taken with standard angulations. For example, changes in angulation can be useful to determine the number and curvature of roots and canals, to identify superimposed roots and to distinguish between anatomical landmarks and apical pathology. Although use of such techniques increases the diagnostic yield of films, it must be appreciated that such views lead to images that are less distinct because of inherent image distortion. Nevertheless, use of the various techniques during endodontics can provide substantial benefit for clinicians in their daily practice. 相似文献
1000.
The case report presents a 25-year-old woman who got pregnant twice in 1 year. Both pregnancies were terminated after ultrasound examination demonstrated limb abnormalities. Radiological and pathological examinations showed diastrophic dysplasia, a rare form of an osteochondrodysplasia with autosomal recessive inheritance. Here the histopathological findings in the cartilage and prenatal diagnosis by ultrasound are discussed. 相似文献