首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1407482篇
  免费   115698篇
  国内免费   3329篇
耳鼻咽喉   18354篇
儿科学   46547篇
妇产科学   41040篇
基础医学   200679篇
口腔科学   37681篇
临床医学   125856篇
内科学   284030篇
皮肤病学   33358篇
神经病学   116813篇
特种医学   53819篇
外国民族医学   464篇
外科学   210476篇
综合类   32746篇
现状与发展   3篇
一般理论   487篇
预防医学   109849篇
眼科学   31453篇
药学   98467篇
  1篇
中国医学   3347篇
肿瘤学   81039篇
  2021年   10846篇
  2019年   11659篇
  2018年   16567篇
  2017年   12666篇
  2016年   14257篇
  2015年   16001篇
  2014年   22555篇
  2013年   33389篇
  2012年   45373篇
  2011年   47912篇
  2010年   28160篇
  2009年   27046篇
  2008年   44305篇
  2007年   46820篇
  2006年   47380篇
  2005年   45845篇
  2004年   43740篇
  2003年   41680篇
  2002年   40181篇
  2001年   72998篇
  2000年   74525篇
  1999年   61554篇
  1998年   16988篇
  1997年   15428篇
  1996年   15581篇
  1995年   14788篇
  1994年   13394篇
  1993年   12581篇
  1992年   45836篇
  1991年   43478篇
  1990年   41486篇
  1989年   39550篇
  1988年   36178篇
  1987年   35351篇
  1986年   32860篇
  1985年   31276篇
  1984年   23823篇
  1983年   20024篇
  1982年   12209篇
  1981年   10779篇
  1979年   20700篇
  1978年   14576篇
  1977年   12084篇
  1976年   11364篇
  1975年   11619篇
  1974年   13988篇
  1973年   13533篇
  1972年   12633篇
  1971年   11469篇
  1970年   10910篇
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
911.
From March 1990 through January 1991, 47 patients undergoing myocardial revascularization had one (37) or both (10) inferior epigastric arteries (IEA) used as a conduit for bypass with 62 distal anastomoses. The internal thoracic artery (ITA) was used bilaterally in 41 patients and unilaterally in 6 with 100 distal anastomoses. Five patients had a single saphenous vein graft. In total, 167 anastomoses (3.55 per patient) were performed. Single IEA grafts were harvested through a paramedian incision and bilateral grafts, a midline incision. Harvest time was 36.5 minutes for IEA grafts and 29.6 minutes for ITA grafts (p less than 0.0001). Graft length was 11.9 cm for IEA grafts and 16.5 cm for ITA grafts (p less than 0.0001). Distal graft diameter was 2.0 mm for IEA grafts and 2.1 mm for ITA grafts (p less than 0.01). Graft flow was 49.7 mL/min for IEA grafts and 48.7 mL/min for ITA grafts. Microscopic assessment of segments of both the IEA and ITA from 14 patients revealed similar internal elastic laminae and an equal number of fenestrations. Combined intimal and medial thickness was comparable in both conduits. Medial elastic tissue was more prominent in ITA grafts and lacking in eight of the 14 IEA grafts. Gross plaque formation was noted in the proximal 1 to 3 cm of 50% of IEA grafts, but the lumen was not compromised and microscopic thickening was minimal. An unexpected finding was medial calcifications (M?nckeberg's disease) in two of the 14 IEAs without associated atherosclerosis. There was one hospital death, one abdominal wound infection, and one instance of fat necrosis superficial to the sternum.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
912.
Esophageal pH monitoring is the accepted standard for the investigation of gastroesophageal reflux (GER) in adults. A postal questionnaire was sent to 912 United Kingdom paediatric physicians & surgeons. Five hundred forty-seven (61%) replied, with 124 (22.7%) currently using the technique, mostly in conjunction with barium swallow and/or esophagoscopy. The use of pH monitoring to quantify GER was also accepted in principal as being the best determinant of reflux by a further 186 (34%), but as yet was unavailable in their hospitals. Pediatricians were also questioned as to their management of children with GER. The majority were treated medically with a variety of antireflux medication, with only 237 (42%) referring cases for surgery.  相似文献   
913.
914.
915.
Immunoregulators in the nervous system   总被引:15,自引:0,他引:15  
The nervous system, through the production of neuroregulators (neurotransmitters, neuromodulators and neuropeptides) can regulate specific immune system functions, while the immune system, through the production of immunoregulators (immunomodulators and immunopeptides) can regulate specific nervous system functions. This indicates a reciprocal communication between the nervous and immune systems. The presence of immunoregulators in the brain and cerebrospinal fluid is the result of local synthesis--by intrinsic and blood-derived macrophages, activated T-lymphocytes that cross the blood-brain barrier, endothelial cells of the cerebrovasculature, microglia, astrocytes, and neuronal components--and/or uptake from the peripheral blood through the blood-brain barrier (in specific cases) and circumventricular organs. Acute and chronic pathological processes (infection, inflammation, immunological reactions, malignancy, necrosis) stimulate the synthesis and release of immunoregulators in various cell systems. These immunoregulators have pivotal roles in the coordination of the host defense mechanisms and repair, and induce a series of immunological, endocrinological, metabolical and neurological responses. This review summarizes studies concerning immunoregulators--such as interleukins, tumor necrosis factor, interferons, transforming growth factors, thymic peptides, tuftsin, platelet activating factor, neuro-immunoregulators--in the nervous system. It also describes the monitoring of immunoregulators by the central nervous system (CNS) as part of the regulatory factors that induce neurological manifestations (e.g., fever, somnolence, appetite suppression, neuroendocrine alterations) frequently accompanying acute and chronic pathological processes.  相似文献   
916.
Atheromatous lesions of the proximal vertebral artery and the subclavian artery may lead to ischaemic manifestations, occasionally with severe consequences in the vertebro-basilar territory. These transient ischaemic attacks are most often caused by haemodynamic insufficiency rather than thrombo-embolic complications addressed by anticoagulant and antiaggregant treatments. In this study, 8 cases of vertebro-basilar ischaemia (VBI), secondary to subclavian and proximal vertebral artery lesions, are reported. Surgical techniques, subclavian-to-subclavian artery by-pass (5 cases) and vertebral to common carotid artery transposition (3 cases) are described with their respective results. Through a review of the literature, the various operative modalities are discussed in the different pathological conditions of the proximal extracranial vertebro-basilar disease. It appears that the subclavian to subclavian artery by-pass as well as the vertebral-to-common carotid artery transposition are safe surgical procedures with strikingly low morbidity and mortality rates. The widely achieved relief of the ischaemic episodes, undoubtedly makes this surgery an alternative to medical treatment.  相似文献   
917.
918.
The records of 108 adult patients with supratentorial low grade astrocytoma presenting between 1/1/80 and 31/12/87 were examined for the following factors which might affect survival: patient age, extent of surgical resection, site of tumour, tumour grade, radiation field size and radiation dose. Univariate analysis showed that patient age, field size and radiation dose were significant prognostic factors, but with multivariate analysis only patient age and radiation field size were significant independent variables. It is possible that field size is a proxy variable for tumour size.  相似文献   
919.
32nd Annual Meeting of the Scandinavian Society for Psychopharmacology Copenhagen, Denmark April 10–12, 1991 Abstracts  相似文献   
920.
D C Perry  L M Grimes 《Brain research》1989,477(1-2):100-108
Quantitative in vitro autoradiography was used to assess the effects of kainic acid (KA) and colchicine (COL) on mu and lambda opiate binding in the rat hippocampus. Rats were treated with either systemic KA, a neurotoxin that damages CA3 pyramidal cells and causes seizures and wet-dog shakes, or intrahippocampal COL to destroy dentate granule cells and their mossy fibers, or both toxins. Moderate levels of mu binding were detected in the pyramidal layer and in the stratum lacunosum-moleculare; binding was greater in the ventral hippocampus. Levels of mu binding were markedly increased in all regions 48 h after treatment with KA. Two weeks after COL treatment, there was a modest decrease in mu binding; COL plus KA gave results similar to COL alone. Dense lambda binding was present over the mossy fibers in the stratum lucidum, but was absent over the pyramidal layer. In contrast to mu binding, lambda binding was greater in the dorsal hippocampus. KA alone had little effect on lambda binding, whereas COL alone caused large decreases. KA plus COL caused even larger decreases in lambda binding, to as much as 85% below control. These results demonstrate that mu and lambda binding are localized to different parts of the hippocampus, respond differently to neurotoxin lesions, and likely serve different roles in this brain region. The number of mu sites is responsive to the release of enkephalin; these receptors appear to be linked to opiate-induced hippocampal seizure activity, especially wet-dog shakes. Lambda sites may serve as autoreceptors on mossy fibers.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号