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   3425篇
  免费   191篇
  国内免费   11篇
耳鼻咽喉   27篇
儿科学   85篇
妇产科学   35篇
基础医学   470篇
口腔科学   470篇
临床医学   234篇
内科学   631篇
皮肤病学   74篇
神经病学   172篇
特种医学   181篇
外科学   276篇
综合类   82篇
预防医学   337篇
眼科学   134篇
药学   282篇
  1篇
中国医学   35篇
肿瘤学   101篇
  2023年   24篇
  2022年   70篇
  2021年   100篇
  2020年   68篇
  2019年   91篇
  2018年   114篇
  2017年   64篇
  2016年   74篇
  2015年   96篇
  2014年   146篇
  2013年   177篇
  2012年   258篇
  2011年   308篇
  2010年   138篇
  2009年   133篇
  2008年   196篇
  2007年   192篇
  2006年   165篇
  2005年   124篇
  2004年   112篇
  2003年   100篇
  2002年   73篇
  2001年   58篇
  2000年   59篇
  1999年   39篇
  1998年   41篇
  1997年   59篇
  1996年   51篇
  1995年   40篇
  1994年   44篇
  1993年   41篇
  1992年   40篇
  1991年   28篇
  1990年   21篇
  1989年   20篇
  1988年   29篇
  1987年   10篇
  1986年   14篇
  1985年   17篇
  1984年   20篇
  1983年   18篇
  1982年   17篇
  1981年   18篇
  1980年   10篇
  1979年   7篇
  1978年   7篇
  1977年   13篇
  1976年   19篇
  1975年   12篇
  1968年   11篇
排序方式: 共有3627条查询结果,搜索用时 15 毫秒
1.
2.
3.
We prospectively evaluated the effectiveness of contrast-enhanced ultrasonography (CEUS) for differentiation of benign versus malignant portal vein thrombosis (PVT). We studied a total of 43 patients with chronic liver disease, hepatocellular carcinoma-suggestive nodules and confirmed PVT, in whom the nature of the PVT was confirmed by follow-up imaging (US, computed tomography and/or magnetic resonance imaging) performed up to 6 mo after CEUS. PVT was assessed by US, Doppler US and CEUS with respect to vessel wall disruption and/or invasion, color Doppler vascularization, pulsed Doppler vascularization pattern and CEUS enhancement and vascularization pattern, and thrombi were classified as benign or malignant based on these findings. Follow-up studies revealed malignant PVT in 22 of the 43 patients (51%) and benign PVT in 21 patients (49%). CEUS findings were consistent with follow-up studies in 41 of the 43 patients (95%), with κ?=?0.903 (p < 0.0001), sensitivity?=?91% and specificity?=?100%, indicating that CEUS can be confidently used to differentiate benign from malignant portal vein thrombosis in the setting of chronic liver disease.  相似文献   
4.
5.
We report the results of administration of danazol after suspension of gonadotrophin-releasing hormone analogue (GnRHa) therapy for uterine myomas. A total of 21 women with uterine myomas was treated with 100 mg danazol for 6 months after GnRHa therapy. Uterine volume and endocrine status were monitored monthly by ultrasound and assay of plasma gonadotrophins, oestradiol and progesterone. The results show a rebound of uterine volume about 30% less than in controls at the end of danazol therapy. Menstrual cyclicity returned after 65 +/- 3 days in 16 subjects and five patients remained amenorrhoeic. Hormone assays confirmed renewed ovarian function in the women whose menstrual periods returned. Bone mineral content was substantially reduced during GnRHa treatment but improved significantly during danazol therapy even in the women who remained amenorrhoeic. These results show the utility of danazol in prolonging the therapeutic effects of GnRHa. The mechanism by which danazol inhibits rebound of uterine volume may be due to its antiprogesterone effects on uterine myomas.   相似文献   
6.
7.
8.
Thanks to recent advances in the molecular genetics of mitochondrial encephalomyopathies, we can now begin to correlate genetic lesions with biochemical defects. In the fatal infantile myopathy due to cytochrome c oxidase (COX) deficiency, an autosomal recessive condition, immunocytochemical studies have shown an isolated defect of subunit VIIa, which is 1 of the only 2 tissue-specific subunits of human COX. In muscle biopsies from patients with Kearns-Sayre syndrome, a multisystem disorder characterized by deletions of the mitochondrial DNA (mtDNA), the activities of all mitochondrial enzymes containing mtDNA-encoded subunits are decreased. The results of Northern analysis, in situ hybridization, and immunocytochemistry in muscle, and of mitochondrial protein synthesis in cultured fibroblasts suggest that partially deleted mtDNAs are transcribed but not translated, probably due to lack of indispensable tRNAs.  相似文献   
9.
The periodontal condition of patients with insulin-dependent diabetes mellitus was evaluated in terms of plaque, gingival indices, pocket depth, and alveolar bone loss. Thirty male and female diabetic patients aged 5 to 18 years were compared with 30 non-diabetic subjects and correlated with sex and age. Statistical analyses of the data showed that the mean plaque index was significantly higher (P less than 0.01) among the diabetic patients (1.23) than among the control subjects (0.81). The plaque index was significantly higher (P less than 0.01) among diabetic females (1.34) than among diabetic males (1.10), whereas no sex differences were observed in the control group. The arithmetic means obtained for gingival index were statistically higher (P less than 0.01) for the diabetics (0.58) when compared with the controls (0.15), but no significant differences were obtained when the values were correlated with sex and age. Pocket depth did not differ statistically between groups. When pocket depth was correlated with sex, a statistically significant difference (P less than 0.05) was observed only for the palatal region, with a depth of 2.1 mm in female patients and 1.92 mm in male patients. When pocket depth was correlated with age, a positive correlation (P less than 0.01) was detected in the diabetic group for all regions investigated, whereas the correlation was not significant in the control group. Mean alveolar bone loss was higher in the anterior upper (1.94 mm) and anterior lower (1.87 mm) regions of the diabetic group when compared to the controls (1.52 and 1.37 mm respectively), the difference being significant at the 5% level of probability.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
10.
We have studied five children with mitochondrial myopathy manifesting within or soon after the first year of life. Muscle biopsies showed ragged-red fibers and decreased respiratory chain activity. All five patients had a severe decrease (2 to 34% of normal) in the amount of muscle mitochondrial DNA (mtDNA). The depletion of mtDNA correlated with absence of mtDNA-encoded translation products and with loss of cytochrome c oxidase enzyme activity in individual muscle fibers. This mitochondrial myopathy of childhood illustrates one phenotypic expression of a novel pathogenetic mechanism in mitochondrial diseases, the specific depletion of mtDNA in affected tissues.  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