首页 | 官方网站   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   26597篇
  免费   1732篇
  国内免费   177篇
医药卫生   28506篇
  2023年   129篇
  2022年   72篇
  2021年   623篇
  2020年   379篇
  2019年   631篇
  2018年   737篇
  2017年   488篇
  2016年   590篇
  2015年   743篇
  2014年   987篇
  2013年   1278篇
  2012年   2035篇
  2011年   1994篇
  2010年   1165篇
  2009年   1190篇
  2008年   1813篇
  2007年   1811篇
  2006年   1754篇
  2005年   1815篇
  2004年   1665篇
  2003年   1565篇
  2002年   1485篇
  2001年   311篇
  2000年   248篇
  1999年   327篇
  1998年   295篇
  1997年   253篇
  1996年   175篇
  1995年   177篇
  1994年   134篇
  1993年   157篇
  1992年   166篇
  1991年   129篇
  1990年   129篇
  1989年   108篇
  1988年   118篇
  1987年   74篇
  1986年   79篇
  1985年   73篇
  1984年   67篇
  1983年   73篇
  1982年   51篇
  1981年   57篇
  1980年   47篇
  1979年   37篇
  1978年   23篇
  1977年   26篇
  1975年   25篇
  1974年   24篇
  1972年   22篇
排序方式: 共有10000条查询结果,搜索用时 453 毫秒
71.
Summary Simultaneous tumors are rarely encountered during the course of acute leukemias. We report on a case of seminoma of the testis that occurred during the evolution of acute myelogenous leukemia. To our knowledge, this stimultaneous association has not previously been described, but a causal relationship was not apparent in the present case. The likelihood of a common carcinogenesis existed, but direct exposure to carcinogens could not be established. Although the results of a physical examination and echography were normal at the time of diagnosis, we cannot exclude the presence of microscopic cancer of the testis. Since the dissemination pattern of seminoma is usually slower than that observed in this case and the disease remains limited to the lymph nodes for long periods following dissemination, the rapid development of the present case might have been attributable to the immunosuppression and the scrotal sepsis that occurred during the induction therapy. Immunosuppression might have stimulated the progression of a primary microscopic seminoma and the development of metastasis, whereas the scrotal sepsis and inflammation might have favored the occurrence of metastasis through bypass of the lymphatic barrier.  相似文献   
72.
The authors report their surgical experiences with 55 extensive tumours of the pharyngoesophageal junction. Thirty-three of these cases were managed by circular pharyngolaryngectomy, total oesophagectomy with stripping and left coloplasty, and 22 were treated with circular pharyngolaryngectomy with free intestinal transplants. A comparative study of the post-operative courses of the patients and their oncological and functional outcomes shows the advantages, disadvantages and indications of these two techniques.  相似文献   
73.
STUDY OBJECTIVE: To investigate the effects of hypoxia-inducible factor (HIF) inhibitors, flotation agents, barriers, and a surfactant on pneumoperitoneum-enhanced adhesions in a laparoscopic mouse model. DESIGN: Prospective randomized trial (Canadian Task Force classification I). SETTING: Department of Obstetrics and Gynecology, University Hospital Gasthuisberg, Catholic University of Leuven. SUBJECTS: One hundred fourteen female BALB/c mice. INTERVENTIONS: Adhesions were induced during laparoscopy in BALB/c female mice. Pneumoperitoneum was maintained for 60 minutes with humidified CO(2). In 3 experiments the effects of HIF inhibitors such as 17-allylamino 17-demethoxygeldanamycin, radicicol, rapamycin, and wortmanin, flotation agents such as Hyskon and carboxymethylcellulose, barriers such as Hyalobarrier gel and SprayGel, and surfactant such as phospholipids were evaluated. MEASUREMENTS AND MAIN RESULTS: Adhesions were scored after 7 days during laparotomy. Adhesion formation decreased with the administration of wortmannin (p <.01), phospholipids (p <.01), Hyalobarrier Gel (p <.01), and SprayGel (p <.01). CONCLUSIONS: These experiments confirm the efficacy of barriers and phospholipids to separate or lubricate damaged surfaces. They also confirm the role of mesothelial hypoxia in this model by the efficacy of the HIF inhibitor wortmannin.  相似文献   
74.
75.
Fetal ultrasound measurements were employed to investigate the relationship between weight and ponderal index at birth and kidney size during the second (23 weeks) and third (32 weeks) trimesters of pregnancy in a sample of 25 normally growing fetuses. Kidney volume and kidney volume / fetal weight ratio at 32 weeks are significantly and positively related to both weight and ponderal index at birth, controlling for sex, gestational age at birth, and day of ultrasound measurement. A second‐degree polynomial relationship approximates the predictability of kidney volume fetal weight ratio at 23 weeks to that at 32 weeks, demonstrating shifting growth rates in fetal organ and body growth relationships during midgestation. Sex and parental size are suggested as contributing to these patterns. Females have a surge in renal growth between 23 and 32 weeks to catch up to earlier growing males, and maternal weight significantly predicts incremental growth in kidney volume and the kidney volume / fetal weight ratio at 32 weeks of gestation. The observation that fetuses relatively thin at birth have relatively smaller kidneys for their size in late gestation suggests that the influence of maternal weight on birth outcome may act through organ growth. Am. J. Hum. Biol. 14:398–406, 2002. © 2002 Wiley‐Liss, Inc.  相似文献   
76.
77.
78.
79.
Using repeated measurements of regional cerebral blood flow with positron emission tomography, we investigated the regional cortical activations induced in 10 normal subjects, by two different finger motor tasks, i.e., a repeated flexion–extension of all fingers and a repeated flexion–extension of the middle finger. The all-finger movement only activated the primary sensorimotor cortex (SM) and the supplementary motor area (SMA) contralateral to the movement. However, the activation of the SMA was clearly task related during this motor task, because it was only observed when the movement was triggered by an auditory cue but not when it was self-paced. The middle finger movement was performed during self-paced conditions. It induced a much more complex pattern of activation than the all-finger movement, characterized by a high degree of SM and SMA activation contralateral to the side of the movement, as well as a slight ipsilateral activation of these areas. We suggest that this pattern of cortical activation may reflect the process of individuating finger movement or the early stages of motor learning of this unusual and technically difficult movement. Our data also confirm that the SM activation is closely linked to the intrinsic parameters of the movement; while the SMA may be activated by different aspects of the movement realization and preparation.  相似文献   
80.
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-23

京公网安备 11010802026262号