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   23222篇
  免费   1468篇
  国内免费   303篇
耳鼻咽喉   409篇
儿科学   340篇
妇产科学   384篇
基础医学   3752篇
口腔科学   302篇
临床医学   1818篇
内科学   4873篇
皮肤病学   759篇
神经病学   1810篇
特种医学   1372篇
外科学   3032篇
综合类   130篇
现状与发展   1篇
一般理论   13篇
预防医学   1051篇
眼科学   784篇
药学   2004篇
中国医学   249篇
肿瘤学   1910篇
  2023年   141篇
  2022年   439篇
  2021年   709篇
  2020年   368篇
  2019年   580篇
  2018年   714篇
  2017年   535篇
  2016年   847篇
  2015年   1080篇
  2014年   1281篇
  2013年   1421篇
  2012年   2107篇
  2011年   2072篇
  2010年   1266篇
  2009年   1058篇
  2008年   1349篇
  2007年   1324篇
  2006年   1136篇
  2005年   1102篇
  2004年   927篇
  2003年   738篇
  2002年   698篇
  2001年   346篇
  2000年   346篇
  1999年   295篇
  1998年   152篇
  1997年   109篇
  1996年   99篇
  1995年   89篇
  1994年   65篇
  1993年   66篇
  1992年   153篇
  1991年   151篇
  1990年   124篇
  1989年   162篇
  1988年   115篇
  1987年   116篇
  1986年   100篇
  1985年   84篇
  1984年   67篇
  1983年   47篇
  1982年   30篇
  1981年   33篇
  1980年   31篇
  1979年   38篇
  1977年   27篇
  1975年   28篇
  1974年   28篇
  1973年   25篇
  1972年   26篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
Six flavonoids were isolated from the aerial parts ofCirsium rhinoceros. The flavonoids were identified as apigenin, luteolin, pectolinarigenin-7-O-β-D-glucopyranoside, linarin, pectolinarin and hispidulin-7-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside on the basis of chemical and spectral evidence.  相似文献   
103.
104.
Fournier's gangrene   总被引:1,自引:0,他引:1  
Fournier's gangrene is a rapidly progressive, necrotizing fasciitis of the perineal, genital or perianal regions. Despite increasing knowledge about aetiology, diagnostic procedures and treatment, the gangrene is still a destructive and potentially lethal disease. In two patients, men aged 54 and 63 years, Fournier's gangrene was diagnosed. The first one died of septic shock 12 hours after admission. Surgical débridement had been performed immediately. He had a latent promyelocytic leukaemia. The second patient recovered fully after extensive surgical and antimicrobial therapy. Fournier's gangrene appears to be caused by the synergistic pathogenic action of various individually non-pathogenic commensal bacteria. Virtually all patients have an underlying systemic disorder, mainly chronic alcoholism or diabetes mellitus. Immunosupression is a predisposing factor. The gangrene requires an aggressive approach, treatment being based on the combination of haemodynamic stabilisation, antibiotic triple therapy and radical surgical débridement.  相似文献   
105.
Carcinoid tumours in the intestine are slowly growing neuroendocrine tumours. Patients as a rule report symptoms of the carcinoid syndrome: attacks of diarrhoea and of flushing. When the earliest symptoms manifest themselves, metastases are already present, virtually always localized in the liver. At a late stage, heart failure may occur, difficult to treat and caused by fibrosis of the tricuspid valve in the presence of protractedly raised blood serotonin levels. To diagnose carcinoid tumours, use is made of radioactive substances binding to hormone receptors such as 131I-MIBG and 111-In-octreotide. When multiple metastases exist, only palliative treatment is possible. The drugs used are the somatostatin analog octreotide, interferon alpha, radioactive MIBG and non-radioactive MIBG; these drugs may also be used in combination. The therapies mentioned have approximately the same effect: symptoms improve in 60-80%, while 30-50% show a biochemical response, i.e. decrease of the number of breakdown products in the urine of the hormones produced by the tumour; tumour size decreases in 0-12%.  相似文献   
106.
Adenovirus (Ad) isolates from a large number of human immunodeficiency virus (HIV)-infected individuals were compared serologically and genetically with Ad isolates from immunocompetent patients. Between 1982 and 1994, stool and urine samples from 137 subjects with AIDS hospitalized in The Netherlands yielded 143 Ad strains. Forty additional Ad strains were obtained from 35 HIV-positive patients in Manchester, United Kingdom, in 1992 and 1993. Of these 183 HIV-associated Ad strains, 84% belonged to species D and 3% belonged to species C. These strains were compared with 2,301 Ad strains collected during general diagnostic examinations in The Netherlands from 1973 to 1992. Of the latter strains, 5% belonged to species D and 49% belonged to species C. Two of the Ads isolated from fecal specimens of AIDS patients represent new serotypes: candidate Ad serotype 50 (prototype strain, Wan) of subspecies B1 and candidate Ad serotype 51 (prototype strain, Bom) of species D. The DNA restriction enzyme patterns of strains Wan and Bom differed from the patterns of all established prototypes.  相似文献   
107.
BACKGROUND AND PURPOSE: The objective was to evaluate the results of high-resolution, fast-speed, section-interpolation MR angiography and digital subtraction angiography (DSA), thereby examining the potential use of a primary noninvasive screening test for intracranial aneurysms. METHODS: The images were obtained in 39 cerebral aneurysmal lesions from 30 patients with a time-of-flight MR angiographic technique using a 1.5-T superconducting MR system. The total image volume was divided into four slabs, with 48 partitions each. To save time, only 24 phase-encoded steps were measured and interpolated to 48. The parameters used included 30/6.4 (TR/TE), a flip angle of 25 degrees , a 160x512 matrix, a field of view of 150x200, 7 minutes 42 seconds of scan time, an effective thickness of 0.7 mm, and an entire thickness of 102.2 mm. Maximum intensity projection was used for the image analysis, and a multiplanar reconstruction technique was used for patients with intracranial aneurysms. RESULTS: Among 39 intracranial aneurysmal lesions in 30 patients, 21 were ruptured and 18 were unruptured. Twelve lesions were less than 2 mm in size, 12 were 3 to 5 mm, 12 were 6 to 9 mm, and three were larger than 10 mm. At initial examinations, 38 of 39 aneurysmal lesions were detected by both MR angiography and DSA, with 97% sensitivity. In confirming aneurysms in neck and parent vessels, multiplanar reconstruction was successful in detecting all 39 aneurysms, whereas MR angiography was successful in detecting 27 (69%) and DSA was successful in detecting 32 (82%) of the lesions. CONCLUSION: High-resolution MR angiography with a section-interpolation technique showed equal results to those of DSA for the detection of intracranial aneurysms and may be used as a primary noninvasive screening test. In the evaluation of aneurysms in neck and parent vessels, the concurrent use of MR angiography and multiplanar reconstruction was far superior to the use of either MR angiography or DSA alone.  相似文献   
108.
OBJECTIVE: To determine the spectrum of clinical and MRI/1H MRS features of patients with fatty aldehyde dehydrogenase (FALDH) deficiency. BACKGROUND: The Sjogren-Larsson syndrome (SLS) was originally defined as a clinical triad consisting of ichthyosis, spastic di- or tetralegia, and mental retardation, with autosomal recessive inheritance. By now, both the deficiency of the enzyme FALDH, and the genetic mutations on chromosome 17 responsible for this deficiency, have been identified. SLS, defined by fibroblast FALDH deficiency, seems to be a much broader syndrome. METHODS: The clinical findings of 11 FALDH-deficient patients of different ages and one patient with the characteristic SLS-like ichthyosis, but without FALDH deficiency, were evaluated in relation to their cerebral MRI, and to 1H MRS in six patients. RESULTS: The severity of neurologic symptoms showed considerable variation. Fundoscopic perifoveal glistening dots and the characteristic SLS-like ichthyosis were present in all patients. Serial MRI findings showed evidence of retarded myelination and a variable degree of dysmyelination. 1H MRS showed an accumulation of free lipids in the periventricular white matter, even before the stage of visible dysmyelination. CONCLUSIONS: The neurologic consequences of FALDH deficiency show considerable variation. The characteristic pattern of ichthyosis and retinal degeneration are seen consistently, yet they are not pathognomonic. MRI and 1H MRS findings suggest an accumulation of long-chain fatty alcohol intermediates, resulting in retarded myelination and dysmyelination.  相似文献   
109.
Axonal degeneration plays an important role in the accumulation of disability in patients with multiple sclerosis (MS). Pathological studies have demonstrated axonal damage, particularly in areas of acute inflammation and demyelination, and in chronic lesions. Axonal loss and its progression, which is associated with neurological disability, has also been demonstrated by magnetic resonance imaging (MRI) studies. The mechanisms of axonal loss are uncertain, but may involve axonal degeneration secondary to demyelination, or damage to the axonal cytoskeleton. Inflammatory mediators, including cytokines and proteolytic enzymes may contribute to axonal damage, as may nitric oxide. Axonal destruction may also be due to immune attack directed at axonal components. The realisation that axonal degeneration is a fundamental component of MS that may occur early in the disease course should alter the approach to management and open avenues to a more targeted immunotherapy aimed at reducing the progression of disability.  相似文献   
110.
The aim of this study was to develop a model to evaluate the retrieval quality of search queries performed by Dutch general practitioners using the printed Index Medicus, MEDLINE on CD-ROM, and MEDLINE through GRATEFUL MED. Four search queries related to general practice were formulated for a continuing medical education course in literature searching. The selected potential relevant citations from the course instructor and the 103 course participants together served as the basic set for the three judges to evaluate for (a) relevance and (b) quality, with the latter based on journal ranking, research design and publication type. Relevant individual citations received a citation quality score from 1 (low) to 4 (high). The overall search quality was expressed in a formula, which included the individual citation quality score of the selected and missed relevant citations, and the number of selected non-relevant citations. The outcome measures were the number and quality of relevant citations and agreement between the judges. Out of 864 citations, 139 were assessed as relevant, of which 44 citations received an individual citation quality score of 1, 76 of 2, 19 of 3 and none of 4. The level of agreement between the judges was 68% for the relevant citations, and 88% for the non-relevant citations. We describe a model for the evaluation of search queries based not only on the relevance, but also on the quality of the citations retrieved. With adaptation, this model could be generalized to other professional users, and to other bibliographic sources.  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