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   150601篇
  免费   31240篇
  国内免费   2414篇
耳鼻咽喉   5196篇
儿科学   5400篇
妇产科学   2460篇
基础医学   3104篇
口腔科学   1522篇
临床医学   26672篇
内科学   47113篇
皮肤病学   7461篇
神经病学   14710篇
特种医学   6337篇
外科学   40926篇
综合类   261篇
现状与发展   72篇
预防医学   7038篇
眼科学   3335篇
药学   953篇
中国医学   19篇
肿瘤学   11676篇
  2024年   688篇
  2023年   4800篇
  2022年   1194篇
  2021年   3103篇
  2020年   6028篇
  2019年   2168篇
  2018年   7392篇
  2017年   7357篇
  2016年   8434篇
  2015年   8436篇
  2014年   15495篇
  2013年   15622篇
  2012年   5478篇
  2011年   5446篇
  2010年   10351篇
  2009年   14219篇
  2008年   5738篇
  2007年   3983篇
  2006年   6437篇
  2005年   3726篇
  2004年   2963篇
  2003年   1958篇
  2002年   2037篇
  2001年   3788篇
  2000年   2991篇
  1999年   3196篇
  1998年   3638篇
  1997年   3452篇
  1996年   3354篇
  1995年   3207篇
  1994年   1937篇
  1993年   1561篇
  1992年   1371篇
  1991年   1402篇
  1990年   1054篇
  1989年   1172篇
  1988年   1017篇
  1987年   851篇
  1986年   885篇
  1985年   719篇
  1984年   552篇
  1983年   519篇
  1982年   514篇
  1981年   405篇
  1980年   362篇
  1979年   308篇
  1978年   329篇
  1977年   400篇
  1975年   280篇
  1972年   306篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
BACKGROUND: Endovascular radiofrequency obliteration has been used since 1998 as an alternative to conventional vein stripping surgery for elimination of saphenous vein insufficiency. OBJECTIVE: To demonstrate the long-term efficacy of this treatment modality. METHODS: Data were prospectively collected in a multicenter ongoing registry. Only great saphenous vein above-knee treatments were included in this study. Eight hundred ninety patients (1,078 limbs) were treated prior to November 2003 at 32 centers. Clinical and duplex ultrasound follow-up was performed at 1 week, 6 months, and 1, 2, 3, and 4 years. RESULTS: Among 1,078 limbs treated, 858 were available for follow-up within 1 week, 446 at 6 months, 384 at 1 year, 210 at 2 years, 114 at 3 years, and 98 at 4 years. The vein occlusion rates were 91.0%, 88.8%, 86.2%, 84.2%, and 88.8%, respectively; the reflux-free rates were 91.0%, 89.3%, 86.2%, 86.0%, and 85.7%, respectively; and the varicose vein recurrence rates were 7.2%, 13.5%, 17.1%, 14.0%, and 21.4%, respectively, at each follow-up time point at 6 months, and 1, 2, 3, and 4 years. Patient symptom improvement persisted over 4 years. CONCLUSIONS: Endovascular temperature-controlled radiofrequency obliteration of saphenous vein reflux exhibits an enduring treatment efficacy clinically, anatomically, and hemodynamically up to 4 years following treatment.  相似文献   
92.
93.
94.
Polycythemia vera is a myeloproliferative disease, which, if untreated, leads to thrombohemorrhagic complications and eventually to progressive myelofibrosis, anemia, and splenomegaly. Two newly available drugs, interferon alfa and imatinib mesylate, may alter the course of this disease. Used as single agents, each produces lasting remissions in about 75% of patients with polycythemia vera. Of significance, change in JAK2 expression has been reported after treatment with both agents.  相似文献   
95.
96.
97.
98.
The purpose of this study was to determine the genetic characteristics of foot polydactyly and identify its inheritance pattern by analyzing familial pedigree. Five cases from 2 Korean families were studied: 1 is a family whose members have been affected for 4 generations and the other for 2 generations. Using peripheral blood samples, we performed chromosomal analysis using the banding technique with Giemsa stain and karyotyping. We investigated the shape and structure of 46 chromosomes, looking for translation, deletion, inversion, ring chromosome, and isochromosome abnormalities. All peripheral blood samples demonstrated no chromosomal abnormalities, though the genetic nature of foot polydactyly and a new genetic locus was identified recently by other studies. Familial pedigree analysis suggested that polydactyly was inherited as an autosomal dominant trait in the first family. The mode of inheritance for the second family could not be determined due to an insufficient number of family members. The result of this study brought us to the conclusion that, while genetic factors play a major role in polydactyly, other factors may contribute to its occurrence.  相似文献   
99.
100.
Cerebrospinal fluid (CSF) from 7 patients with infantile spasms (mean age: 6.7 months) was collected before and after treatment with adrenocorticotropic hormone (ACTH). The concentration of neurotransmitter metabolites was analyzed using high-performance liquid chromatography and compared to the metabolite concentration in the CSF from 7 age-matched controls (mean age: 6.1 months). Pretreatment levels of CSF 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid, 3-methoxy-4-hydroxyphenyl glycol (MHPG), and kynurenine were significantly lower in infantile spasm patients compared to controls. Following treatment, marked increases in 5-HIAA and decreases in kynurenine levels were observed in the CSF of the 5 infants whose seizures were eliminated or reduced by ACTH. In the 2 nonresponders 5-HIAA levels decreased. The level of MHPG was reduced slightly in 5 infants, including the 2 nonresponders, and was increased in 2 responders. CSF homovanillic acid levels increased in 4 infantile spasm infants and decreased in 3 following ACTH. These data demonstrate that the presence of seizures in infantile spasms is associated with a significant decrease in serotonergic activity and that elimination of seizures by ACTH is accompanied by increased serotonin turnover. The simultaneous increase of 5-HIAA and decrease of kynurenine, an alternate metabolite of tryptophan, suggests an underlying disturbance of tryptophan metabolism in infantile spasms. The possibility that elimination of seizures by ACTH may be related to decreased production of certain kynurenine metabolites, particularly quinolinic acid, is discussed.  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