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   2634077篇
  免费   210202篇
  国内免费   4904篇
耳鼻咽喉   35848篇
儿科学   87611篇
妇产科学   74895篇
基础医学   374171篇
口腔科学   75583篇
临床医学   236367篇
内科学   515572篇
皮肤病学   58610篇
神经病学   215993篇
特种医学   103115篇
外国民族医学   897篇
外科学   395494篇
综合类   64776篇
现状与发展   6篇
一般理论   970篇
预防医学   207246篇
眼科学   60894篇
药学   192583篇
  3篇
中国医学   5478篇
肿瘤学   143071篇
  2018年   27431篇
  2017年   21083篇
  2016年   23762篇
  2015年   27020篇
  2014年   37924篇
  2013年   57291篇
  2012年   77426篇
  2011年   81813篇
  2010年   48321篇
  2009年   46182篇
  2008年   76966篇
  2007年   81376篇
  2006年   82627篇
  2005年   80184篇
  2004年   77755篇
  2003年   74366篇
  2002年   72283篇
  2001年   125887篇
  2000年   129506篇
  1999年   108834篇
  1998年   30514篇
  1997年   27621篇
  1996年   27561篇
  1995年   26499篇
  1994年   24509篇
  1993年   23157篇
  1992年   86262篇
  1991年   83153篇
  1990年   80624篇
  1989年   77492篇
  1988年   71814篇
  1987年   70481篇
  1986年   66629篇
  1985年   63897篇
  1984年   48289篇
  1983年   41321篇
  1982年   24724篇
  1981年   22043篇
  1979年   44742篇
  1978年   31268篇
  1977年   26309篇
  1976年   24782篇
  1975年   25742篇
  1974年   31465篇
  1973年   30381篇
  1972年   28060篇
  1971年   26127篇
  1970年   24421篇
  1969年   22751篇
  1968年   21050篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
Clinicopathological and electron microscopical findings of eight cases of enzootic nasal adenocarcinoma of sheep, diagnosed solely in one big flock in Slovenia between years 2001 and 2003 are described. All affected sheep were female, their mean age was 4.5 ± 1.5 years and they either belonged to the Istrian pramenka breed (five sheep) or were crossbreeds (three sheep). Tumours that arose from the ethmoid area of the nasal cavity were unilateral in six cases (75%) and bilateral in two cases (25%). All tumours were classified as adenocarcinomas by histopathological examination and they displayed either a combination of tubular and papillary growth or less often solely tubular proliferation. No metastases were detected in regional lymph nodes, brain or other organs. Electron microscopical studies performed on the reprocessed paraffin‐embedded tissues revealed the presence of the virus‐like particles with an average diameter between 70 and 90 nm.  相似文献   
93.
A new semi-empirical formula for the evaluation of (n,(3)He) reaction cross-sections at the energy of 14.6 and 20 MeV is presented. Formula was derived using the analytical expression for the evaluation of the (3)He spectrum within the frame of pre-equilibrium exciton model. The systematics obtained is compared with the empirical formula for the (n,(3)He) reaction cross-section.  相似文献   
94.
95.
Systems of care (SOCs) have been developed throughout the country to meet the needs of children with severe emotional disturbances (SED) and their families. In these SOCs, multiple agencies and disciplines are expected to work together with informal community supports to address families' needs (Stroul & Friedman, 1986a). A review of the literature on the impact of SOCs suggests: (a) communities' service delivery systems change; and (b) children experience modest improvements in symptomatology and functioning. At the same time, little is known about (a) which components of the SOC approach, at what levels, are necessary to impact child and family outcomes; (b) the degree to which SOCs affect other family members, beyond the target child; and (c) the impact of community contexts and supports in SOCs. Future research should improve measurement of key SOC constructs, examine the relation between specific levels of implementation and outcomes for the entire family, and investigate the impact of broader community systems and supports on families within SOCs. © 2004 Wiley Periodicals, Inc. J Comm Psychol 32: 655–674, 2004.  相似文献   
96.
Although melanocytic skin lesions have been recognized since antiquity, their literature was limited to Caucasians. To date, the clinicopathologic features of these lesions in Egyptians are still unknown. To define these features, diagnostic records of the melanocytic skin lesions received at the Pathology Department, Assuit University Hospitals (1989-2004) were reviewed. The lesions examined included 12 benign naevi (BN), 10 dysplastic naevi (DN), and 21 cutaneous malignant melanomas (CMMs). The DN and CMMs were more common in men than in women (2 : 1 and 1.5 : 1, respectively) while BN were more common in women (2 : 1). The average age incidence was 33+/-5, 38+/-7 and 54+/-3 years, for BN, DN and CMM, respectively. The lower limb (13/21, 62%), head and neck (7/21, 33%) were the most common sites for CMMs. The average size (mm) was 2+/-0.3, 4+/-0.6 and 21+/-0.3 for BN, DN and CMMs, respectively. Recurrence occurred in 10% of CMMs. Histologically, CMMs were of nodular type and composed of epithelioid (7/21, 33%), spindle cells (1/21, 5%), or mixed cells (13/21, 62%). The mean tumour thickness (Breslow) was 6+/-0.5 mm. CMMs included two of 21(9%), three of 21(14%), six of 21(38%), and 10 of 21(38%) with Clark level II, III, IV and V. In Egypt, CMM is the third most common cutaneous neoplasm following squamous and basal cell carcinomas. Compared with Western societies, melanoma has a male sex predilection, similar histological features but different topographical distribution and rare incidence. The striking difference from Western series is the incidence of nodular melanoma - in the West this represents 15-30% of melanomas, with superficial spreading being the majority. Another key difference from the West is the 'sun-bed' culture of the West and the desire to have suntans. This is the first study that reports the clinicopathologic features of melanocytic skin lesions in Egypt.  相似文献   
97.
Erythropoietin exerts hematopoietic effects by stimulating proliferation of early erythroid precursors. Nonhematopoietic effects of erythropoietin have also been shown. It may act as a new angiogenic factor in wound healing. This study aimed to investigate the effect of systemic administration of recombinant human erythropoietin on wound healing in mice. Dorsal incisional wounds were performed in mice, which were then divided into two groups; a group treated for 7 days with recombinant human erythropoietin, and a control group. Sacrificing animals on day 7, the wound tissues were collected for analysis of wound breaking strength, malondialdehyde, a marker of lipid peroxidation, hydroxyproline, an index of reparative collagen deposition, reduced glutathione levels, and for histological evaluation. The immunohistochemical determination of vascular endothelial growth factor (VEGF) which is believed to be the most prevalent angiogenic factor throughout the skin repair process, was also studied. The treatment significantly increased wound breaking strength by decreasing malondialdehyde and increasing hydroxyproline levels on day 7 after wounding. No statistically meaningful change was observed in reduced glutathione content. VEGF was immunostained significantly more on wound tissue of treated animals compared to the control group. Recombinant human erythropoietin treatment may be effective in wound healing due to inhibition of lipid peroxidation, deposition of collagen, and VEGF expression in wound area.  相似文献   
98.
99.
100.
Liposarcomas are extremely rare in the mediastinum. They may achieve considerable size before causing any symptoms. Mediastinal liposarcomas may invade surrounding structures like the pericardium or the superior vena cava. Complete surgical excision is the optimal treatment in resectable cases. Excision of adjacent structures like the pericardium may be needed if the tumor infiltrates them. We report on a case of a giant liposarcoma of the mediastinum involving both hemithoraces and extending into the neck, which was successfully managed by complete surgical excision.  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