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   108627篇
  免费   8460篇
  国内免费   5759篇
耳鼻咽喉   1147篇
儿科学   1552篇
妇产科学   2311篇
基础医学   12677篇
口腔科学   1995篇
临床医学   14431篇
内科学   17040篇
皮肤病学   924篇
神经病学   5953篇
特种医学   3593篇
外国民族医学   42篇
外科学   11700篇
综合类   14998篇
现状与发展   23篇
一般理论   20篇
预防医学   6204篇
眼科学   2940篇
药学   10902篇
  85篇
中国医学   4964篇
肿瘤学   9345篇
  2025年   66篇
  2024年   1716篇
  2023年   2032篇
  2022年   3952篇
  2021年   5336篇
  2020年   3813篇
  2019年   3488篇
  2018年   3561篇
  2017年   2967篇
  2016年   2901篇
  2015年   4442篇
  2014年   5638篇
  2013年   5025篇
  2012年   7532篇
  2011年   8264篇
  2010年   4977篇
  2009年   3819篇
  2008年   5268篇
  2007年   5560篇
  2006年   5407篇
  2005年   5703篇
  2004年   3830篇
  2003年   3398篇
  2002年   3004篇
  2001年   2442篇
  2000年   2651篇
  1999年   2699篇
  1998年   1580篇
  1997年   1482篇
  1996年   1314篇
  1995年   1162篇
  1994年   986篇
  1993年   635篇
  1992年   998篇
  1991年   805篇
  1990年   686篇
  1989年   601篇
  1988年   593篇
  1987年   529篇
  1986年   420篇
  1985年   330篇
  1984年   208篇
  1983年   159篇
  1982年   85篇
  1981年   98篇
  1980年   84篇
  1979年   116篇
  1978年   54篇
  1977年   56篇
  1974年   45篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
OBJECTIVES: To examine the effect of individual patient factors (age, parity, body mass index, menstrual cycle, menopause, hormone replacement therapy, bladder neck position and urethral mobility) on the appearance of Doppler flow in urethral vessels, to investigate the association between the Doppler flow parameters and intrinsic urethral function, storage and voiding, and to explore differences in the urethral vasculature between subjects with and without urodynamic stress incontinence (USI). METHODS: Over a 4-year period we prospectively performed imaging studies in 355 women, including 244 who denied any lower urinary tract symptoms within the previous 3 months (Group A) and 111 who had had lower urinary tract symptoms (Group B). Studies included morphologic assessment and Doppler flow investigation of the lower urinary tract. Vascular flow velocity and vessel density in the urethral vasculature were measured. For women in Group B, multichannel urodynamic studies were also performed. RESULTS: The urethral vasculature has five main branches of vessels. Their appearance was not affected by the menstrual cycle or menopause except for those of the anterior vaginal vessel and anterior branch of the middle urethral vessel. Other than that of the posterior urethral vessel, in which there was a correlation with parity, the resistance index (RI) was not affected by individual patient factors. However, there was a correlation between the vascular index (VI) and individual factors such as age (r = -0.336, P = 0.002), body mass index (r = -0.287, P = 0.028), menopause (r = -0.402, P < 0.001), and hormone replacement therapy (r = 0.392, P = 0.027). Only the VI and RI of the posterior urethral vessel correlated significantly with the urethral pressure profile. In subjects with lower urinary tract symptoms, the appearance of the urethral vasculature on power Doppler imaging and the corresponding RI and VI values were not correlated with objective evidence of USI. CONCLUSION: Patient factors may affect specific Doppler flow parameters of the urethral vasculature, which are related to intrinsic resting urethral closure. There is no difference in the appearance of the urethral vasculature in subjects with or without USI.  相似文献   
23.
24.
Amyloidosis is a systemic disease that usually occurs in the gastrointestinal tract or in muscular or adipose tissue. Primary amyloidosis of the urinary bladder is a rare disease that can mimic bladder cancer on cystoscopic examination as well as in its clinical presentation of painless gross hematuria. This report describes a 49-year-old male with repeated painless gross hematuria, who underwent transurethral resection of a suspected bladder tumor. Pathologic examination revealed papillary urothelial hyperplasia with vascular ectasia and no signs of malignancy. Massive gross hematuria occurred 2.5 years later. Cystoscopy showed multiple papillary lesions with yellowish-brown submucosal plaques on the posterior bladder wall. A second transurethral tumor resection was performed and histologic examination revealed plasma cell infiltration and eosinophilic amorphous deposits in the subepithelial stroma and vascular wall. The deposits were positive for Congo red and apple-green birefringence under polarized light examination but negative for Masson's trichrome stain, indicating that they were not fibrotic in nature. Hence, the diagnosis of amyloidosis of the urinary bladder was confirmed. Screening for amyloidosis was negative in other organ systems and the patient has remained disease-free up to the last follow-up 4 years after the second transurethral resection. Amyloidosis should be considered in the differential diagnosis of patients with recurrent hematuria who have symptoms characteristic of bladder cancer but negative pathologic study for malignancy. Correct diagnosis relies on clinical alertness and the use of a special staining technique during pathologic examination.  相似文献   
25.
26.
T lymphocytes play a fundamental role in the initiation and regulation of chronic inflammatory responses in patients with asthma. CD69 is an early marker of T‐cell activation. The levels of intercellular adhesion molecule‐1 (ICAM‐1, CD54) and L ‐selectin have been reported to increase in patients with allergic diseases and asthma. The present study was therefore undertaken to investigate the expression of CD69, CD54, and L ‐selectin by T lymphocytes of children with asthma, before and after immunotherapy. Eighteen children newly diagnosed with asthma, 11 good and nine poor responders to immunotherapy, and 16 normal subjects, were enrolled in this study. The percentages of CD69+, CD54+, and CD62L+ cells in T lymphocytes were measured by using flow cytometry. The levels of CD69, CD54, and CD62L in serum and culture supernatants were determined by using enzyme‐linked immunosorbent assay (ELISA). The expression of CD69 and CD54 on CD3+ T lymphocytes was significantly higher in children with asthma than in control patients. All the patient groups expressed (spontaneously and following stimulation with phorbol myristate acetate and ionomycin together with mite‐extract proteins) greater amounts of CD69 and CD54 than did control subjects. With long‐term immunotherapy, the percentages of CD69+ and CD54+ T lymphocytes were significantly lower in patients with a good response to immunotherapy. Our results also showed significantly lower serum L ‐selectin levels following immunotherapy. In conclusion, successful immunotherapy resulted in decreased expression and production of CD69 and CD54. These results may explain, in part, the clinical efficacy of immunotherapy.  相似文献   
27.
28.
29.
Propionic acidemia is a rare hereditary disease which is an autosomal recessive disorder. Defect of propionyl CoA carboxylase results in abnormal accumulation of propionate and its metabolites which interfere the pathway of glycine cleavage and the urea cycle. This organic acidemia is characterized by a wide spectrum of clinical and biochemical findings, including recurrent vomiting, difficult feeding, lethargy, hypotonia, metabolic ketoacidosis, hyperglycinemia and hyperammonemia during the acute episodes. We present a male newborn infant who sustained this disorder and was managed successfully with blood exchange transfusion, peritoneal dialysis, supplemented with sodium benzoate and sodium bicarbonate therapy. Urine gas chromatography disclosed significant elevation of propionate and its metabolites which subsided 2 days after peritoneal dialysis. Special designed formula was then given with restriction of protein intake and supplement with sodium benzoate and sodium carbonate. Prenatal genetic counseling is necessary in further pregnancy. Diagnosis can be obtained when propionyl CoA carboxylase activity is low in cultured amniotic fluid cells or chorion villi sample or when there is abnormally high methylcitrate level in amniotic fluid.  相似文献   
30.
A 51-year-old man was admitted because of hemoptysis. Physical examinations and chest XP revealed no abnormal findings. Fiberoptic bronchoscopy showed pulsatile bleeding at the orifice of right B6. Right bronchial arteriography showed a markedly dilated and tortous bronchial artery and shunting to the pulmonary arterial system in the middle and lower lobes. Pulmonary arteriography showed complete obstruction of the right middle lobar and lower lobe segmental arteries (A6, 9, 10). The hemoptysis was thought to be due to increased blood flow of the right bronchial artery, which compensated for reduced right pulmonary arterial flow. Right middle and lower lobe resection was done to prevent further hemoptysis. The resected specimen revealed old thromboemboli in the right middle and lower lobe pulmonary arteries. In this case old pulmonary embolism should be considered as a cause of intrabronchial bleeding.  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