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   2637103篇
  免费   199234篇
  国内免费   4989篇
耳鼻咽喉   37789篇
儿科学   83925篇
妇产科学   76060篇
基础医学   371006篇
口腔科学   79553篇
临床医学   229090篇
内科学   512026篇
皮肤病学   58373篇
神经病学   212634篇
特种医学   105316篇
外国民族医学   879篇
外科学   403717篇
综合类   64339篇
现状与发展   9篇
一般理论   918篇
预防医学   195792篇
眼科学   62109篇
药学   199351篇
  7篇
中国医学   5390篇
肿瘤学   143043篇
  2018年   24047篇
  2015年   24238篇
  2014年   33658篇
  2013年   51626篇
  2012年   68627篇
  2011年   72534篇
  2010年   43077篇
  2009年   41247篇
  2008年   69666篇
  2007年   74523篇
  2006年   75497篇
  2005年   73426篇
  2004年   71904篇
  2003年   69337篇
  2002年   68136篇
  2001年   122296篇
  2000年   126048篇
  1999年   107350篇
  1998年   29260篇
  1997年   26614篇
  1996年   26101篇
  1995年   25090篇
  1994年   23588篇
  1993年   22130篇
  1992年   86558篇
  1991年   83930篇
  1990年   82174篇
  1989年   80078篇
  1988年   74557篇
  1987年   73398篇
  1986年   70077篇
  1985年   67224篇
  1984年   50357篇
  1983年   43236篇
  1982年   25665篇
  1981年   23211篇
  1980年   21748篇
  1979年   48270篇
  1978年   34031篇
  1977年   29064篇
  1976年   26820篇
  1975年   29305篇
  1974年   35464篇
  1973年   34209篇
  1972年   32026篇
  1971年   30116篇
  1970年   28130篇
  1969年   26723篇
  1968年   24848篇
  1967年   22376篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
93.
94.
95.
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   
96.
97.
98.
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   
99.
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   
100.
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   
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