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   22647篇
  免费   2181篇
  国内免费   138篇
耳鼻咽喉   371篇
儿科学   666篇
妇产科学   362篇
基础医学   3214篇
口腔科学   600篇
临床医学   2314篇
内科学   4162篇
皮肤病学   289篇
神经病学   1699篇
特种医学   803篇
外科学   3328篇
综合类   561篇
一般理论   26篇
预防医学   2445篇
眼科学   660篇
药学   1491篇
中国医学   16篇
肿瘤学   1959篇
  2021年   300篇
  2020年   172篇
  2019年   261篇
  2018年   341篇
  2017年   263篇
  2016年   301篇
  2015年   329篇
  2014年   473篇
  2013年   716篇
  2012年   1020篇
  2011年   1005篇
  2010年   568篇
  2009年   510篇
  2008年   892篇
  2007年   1048篇
  2006年   964篇
  2005年   997篇
  2004年   875篇
  2003年   881篇
  2002年   798篇
  2001年   769篇
  2000年   770篇
  1999年   677篇
  1998年   299篇
  1997年   281篇
  1996年   269篇
  1995年   240篇
  1994年   250篇
  1993年   238篇
  1992年   587篇
  1991年   521篇
  1990年   494篇
  1989年   528篇
  1988年   460篇
  1987年   438篇
  1986年   415篇
  1985年   399篇
  1984年   328篇
  1983年   261篇
  1982年   205篇
  1981年   214篇
  1979年   294篇
  1978年   263篇
  1977年   183篇
  1975年   188篇
  1974年   253篇
  1973年   195篇
  1972年   203篇
  1971年   169篇
  1969年   165篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
AMEDLINEsearchwasconductedtoidentifystudiespublishedfromJanuary1999toMarch2004thatcom-paredinjectablecalciumphosphatebone(NorianSRS)cementwithconventionaltreatmentindistalradialfrac-tures.Fromalistof13articlesidentifiedfromthesearchstrategy,fourarticleswe…  相似文献   
102.
BACKGROUND: Chronic inflammation is associated with processes that contribute to the onset or progression of cancer. This study examined the relationships between circulating levels of the inflammatory markers interleukin-6 (IL-6), C-reactive protein (CRP), and tumor necrosis factor-alpha (TNF-alpha) and total as well as site-specific cancer incidence. METHODS: Study subjects (n = 2,438) were older adults (ages 70-79 years) participating in the Health Aging and Body Composition study, who did not report a previous cancer diagnosis (except for nonmelanoma skin cancer) at baseline. Incident cancer events (n = 296) were ascertained during an average follow-up of 5.5 years. Inflammatory markers were measured in stored baseline fasting blood samples. RESULTS: The adjusted hazard ratios (95% confidence intervals) for incident cancer associated with a 1-unit increase on the natural log-scale were 1.13 (0.94-1.37), 1.25 (1.09-1.43), and 1.28 (0.96-1.70) for IL-6, CRP, and TNF-alpha, respectively. Markers were more strongly associated with cancer death: hazard ratios were 1.63 (1.19-2.23) for IL-6, 1.64 (1.20-2.24) for CRP, and 1.82 (1.14-2.92) for TNF-alpha. Although precision was low for site-specific analyses, our results suggest that all three markers were associated with lung cancer, that IL-6 and CRP were associated with colorectal cancer, and that CRP was associated with breast cancer. Prostate cancer was not associated with any of these markers. CONCLUSIONS: These findings suggest that (a) the associations between IL-6, CRP, and TNF-alpha and the risk of cancer may be site specific and (b) increased levels of inflammatory markers are more strongly associated with the risk of cancer death than cancer incidence.  相似文献   
103.
Traditional treatments of spectacle magnification for distant objects consider only stigmatic spectacle lenses and they compare the retinal image size in a refractively fully compensated eye with the image size in the uncompensated eye. Spectacle magnification is expressed as a product of two factors, the power and shape factors of the lens. The power factor depends on the position of the entrance pupil of the eye. For an eye with an astigmatic cornea, however, the position of the entrance pupil is not well defined. Thus, the traditional approach to spectacle magnification does not generalize properly to allow for astigmatism. Within the constraints of linear optics and subject to the restriction that the eye's iris remains the aperture stop, this paper provides a complete, unified and exact treatment for optical instruments in general. It compares retinal image size in a generalized sense (including image shape and orientation) for any instrument in front of an eye with that of the eye alone irrespective of whether the instrument compensates or not. The approach does not make use of the concept of the entrance pupil at all and it allows for astigmatism and for non-alignment of refracting elements in the instrument and in the eye. The concept of spectacle magnification generalizes to the concept of instrument size magnification. Instrument size magnification can be expressed as the product of two matrix factors one of which can be interpreted as a power factor (as back-vertex power) and the other factor for which the name dilation factor is more appropriate in general. The general treatment is then applied to a number of special cases including afocal instruments, spectacle lenses (including obliquely crossing thick bitoric lenses), contact lenses, stigmatic systems and stigmatic eyes. In the case of spectacle lenses, the dilation factor reduces to the usual shape factor.  相似文献   
104.
A general expression is derived for the proximity factor in near image size magnification for an arbitrary instrument in front of an arbitrary eye. The proximity factor is a 2 x 2 matrix. The instrument and eye may be astigmatic and have decentred elements. The image on the retina may be blurred or not. The analysis is exact within the limitations of linear optics. The general results are specialized for the case of a stigmatic instrument and a stigmatic eye. The results are applied to the case of a thick, possibly bitoric, spectacle lens. The Appendix treats two numerical examples.  相似文献   
105.
Age‐related macular degeneration is a major cause of serious vision loss. The earliest stages of age‐related maculopathy may be defined by the size of the drusen present in the macula and the effects on vision. Further manifestations may include soft drusen, choroidal neovascularisation, macular haemorrhage and cicatricial or disciform degeneration of the macula. This report describes a patient with a macular haemorrhage, a choroidal neovascular membrane and serious loss of vision. In addition, the pathogenesis, diagnosis and treat‐ment options of macular degeneration are reviewed.  相似文献   
106.
Hodgkin's lymphoma rarely involves the thyroid gland. We report the clinical and pathologic features of five cases of Hodgkin's lymphoma that presented as thyroid lesions. All five patients were females, aged 29-59 years. Three patients had a history of chronic thyroiditis and hypothyroidism and two were euthyroid. One patient had a remote history of Hodgkin's lymphoma. Imaging studies showed a 'cold' nodule (three cases) or a diffusely enlarged thyroid gland, resembling goiter or fibrosclerosing thyroiditis (two cases). Thyroid fine-needle aspiration was performed before thyroidectomy in all cases; three of these cases contained some atypical cells, raising the possibility of Hodgkin's lymphoma. Histologically, all cases were classical Hodgkin's lymphoma, nodular sclerosis subtype. The four patients with primary thyroid lymphoma had Stage IIE disease. All patients were treated with surgical excision and chemotherapy, with or without radiation therapy, and were alive after 2 months to 7 years of follow-up. A review of the English literature between 1962 and 2005 revealed 16 cases of thyroid Hodgkin's lymphoma, with a female preponderance and generally favorable outcome similar to the cases in our series. Hodgkin's lymphoma of the thyroid is rare and can mimic a primary thyroid epithelial tumor or thyroiditis clinically. Histologic diagnosis may be difficult due to marked fibrosis. Hodgkin's lymphoma should be considered in the differential diagnosis of thyroid neoplasms.  相似文献   
107.
108.
109.
A 15-year experience with 38 aortic graft infections, including 15 patients with graft enteric fistulas, is reviewed in order to analyze modern-day surgical results utilizing extra-anatomic bypass and aortic graft excision. Perioperative mortality was 14% during the most recent 7-year interval, which was a notable improvement compared with the earlier time interval (p = 0.06). Extended follow-up of the perioperative survivors demonstrated a 77% cumulative 5-year survival and a 76% cumulative 5-year limb salvage rate. Subsequent axillofemoral graft infection occurred in 22% of survivors and resulted in a significantly higher amputation rate compared with those patients with no axillofemoral graft infection (p less than 0.001). The results suggest good perioperative and long-term survival in patients with aortic graft infection, with excellent limb salvage if subsequent axillofemoral graft infection can be avoided.  相似文献   
110.
Gangliosides were isolated from human cataractous nuclei by solvent extraction, dialysis, and thin-layer chromatography and compared to gangliosides present in human whole normal and cataractous lenses. Three predominant gangliosides were tentatively identified as GM1, GM3, and GD1a, and several other resorcinol-positive components were observed in each of the sets of lens tissue. Thin-layer chromatographic patterns were similar, although some minor and possibly significant differences in band intensities were observed when chromatograms of gangliosides from cataractous nuclei and cataractous whole lenses were visually compared with those of whole normal lenses. Total ganglioside extracts were methanolyzed and the fatty acid methyl esters extracted with hexane and resolved by gas chromatography. Nervonic acid (C-24:1) content was increased in cataractous nuclei as compared to normal and cataractous whole lenses.  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