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   2492864篇
  免费   174445篇
  国内免费   5396篇
耳鼻咽喉   33828篇
儿科学   80501篇
妇产科学   67626篇
基础医学   356478篇
口腔科学   72003篇
临床医学   225104篇
内科学   478071篇
皮肤病学   57241篇
神经病学   192767篇
特种医学   95668篇
外国民族医学   437篇
外科学   375088篇
综合类   54060篇
现状与发展   6篇
一般理论   772篇
预防医学   182174篇
眼科学   58923篇
药学   189117篇
  13篇
中国医学   6745篇
肿瘤学   146083篇
  2021年   20217篇
  2019年   20109篇
  2018年   28935篇
  2017年   22178篇
  2016年   25071篇
  2015年   28891篇
  2014年   39424篇
  2013年   56796篇
  2012年   78738篇
  2011年   82345篇
  2010年   48836篇
  2009年   45370篇
  2008年   75279篇
  2007年   79874篇
  2006年   80108篇
  2005年   76446篇
  2004年   73266篇
  2003年   69794篇
  2002年   67060篇
  2001年   128178篇
  2000年   131143篇
  1999年   108793篇
  1998年   28595篇
  1997年   25008篇
  1996年   25039篇
  1995年   23908篇
  1994年   21830篇
  1993年   20387篇
  1992年   82086篇
  1991年   79169篇
  1990年   76943篇
  1989年   73842篇
  1988年   67145篇
  1987年   65424篇
  1986年   61825篇
  1985年   58603篇
  1984年   42905篇
  1983年   36532篇
  1982年   20509篇
  1979年   38193篇
  1978年   26274篇
  1977年   22846篇
  1976年   20737篇
  1975年   22541篇
  1974年   26939篇
  1973年   25954篇
  1972年   24245篇
  1971年   22624篇
  1970年   20924篇
  1969年   19784篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
A variety of nutritional factors influence the bioavailability of calcium and increase a woman's risk of osteoporosis. Eight healthy women completed an 8-week metabolic study designed to investigate the effect of nonalcoholic carbonated beverage consumption on calcium metabolism. Compared with women receiving a control diet, women consuming a diet high in nonalcoholic carbonated beverages demonstrated similar mean serum levels of calcium, ionized calcium, phosphorus, alkaline phosphatase, parathyroid hormone, 1,25-dihydroxyvitamin D3, and osteocalcin. Twenty-four-hour urine volume, creatinine clearance, calcium-creatinine ratio, and phosphorus-creatinine ratio were similar during consumption of the diet high in nonalcoholic carbonated beverages and the control diet. Twenty-four-hour cyclic adenosine monophosphate-creatinine ratio was significantly lower in women consuming the diet high in nonalcoholic carbonated beverage compared with women receiving the control diet (342 +/- 27.4 nmol/mmol vs 409 +/- 22.1 nmol/mmol). Consumption of a diet high in nonalcoholic carbonated beverages on a short-term basis does not appear to affect adversely the serum or urinary markers of calcium metabolism.  相似文献   
994.
There is evidence that leukocyte contaminating red blood cells and platelet concentrates are responsible for refractoriness to platelet transfusions. The efficacy of a cotton-wool filter to remove leukocytes from red blood cells has been documented previously. The present study was designed to evaluate whether the cotton-wool filters can effectively remove leukocytes from platelet concentrates. Sixty pools of random-donor platelets and single-donor plateletpheresis products were filtered through a cotton-wool filter. The efficacy of filtration was determined by measuring the absolute numbers of leukocytes and platelets and subpopulations of mononuclear cells. The average platelet loss was 8% per pool of random platelets and 10% per plateletpheresis product. The average leukocyte removal was 99% from a pool of random platelets and plateletpheresis concentrates collected by CS-3000 and 90% from plateletpheresis concentrates harvested by single-stage COBE/IBM-2997. The filtration removed 100% of granulocytes, 95% of monocytes, 90% of B-lymphocytes, and 85% of T-lymphocytes. We conclude that filtration through a cotton-wool filter is an efficient and cost-effective method for preparation of leukocyte-poor platelets.  相似文献   
995.
996.
A 41-year-old woman had acute hepatitis A infection complicated with severe anemia due to selective erythroblastopenia and hemolysis. A mechanism involving a cellular immune reaction is suggested. The hematological complications resolved during steroid treatment. She later developed a transient seropositive arthritis.  相似文献   
997.
Breast preserving surgery or conservative surgery consists at present of a combination of a reduced operation--tumorectomy or wedge resection or subcutaneous mastectomy--with adequate radiotherapy whereby a doses of 40-50 Gy is used with or without an additional booster dose of 10 Gy. Recent studies of 5-year- and 10-year-survival rates after conservative management have been shown to be identical with radical operations (Rotter-Halsted, Patey-Auchincloss). In the Departments of Gynecology and Obstetrics of the Universities of Münster and Rostock the partial bilateral subcutaneous mastectomy with lymphadenectomy and irradiation is the preferred method of conservative management for breast cancer. Indications and technique are discussed.  相似文献   
998.
To evaluate the use of pelvic ultrasonography in the diagnosis and management of female adolescents with pelvic inflammatory disease (PID), sonograms of 60 patients with PID were compared with those of 40 age-matched controls. Sonograms were evaluated for adnexal volume, adnexal adherence, uterine size, and the presence of cul-de-sac fluid. Eleven (19.3%) of the 57 patients with PID, in whom adequate sonograms were obtained, had tubo-ovarian abscesses; in seven of these patients, the abscesses were diagnosed ultrasonographically before suspected clinically. Even in those patients without tubo-ovarian abscesses, the mean (+/- SD) adnexal volume in the PID group was significantly larger than that of the control group (11.0 +/- 6.8 cm3 vs 5.2 +/- 2.7 cm,3 respectively). Adnexal adherence, uterine size, and the presence of cul-de-sac fluid were not useful in differentiating patients with PID from normal controls. Pelvic ultrasonography can be a useful adjunct in the diagnosis and management of PID in adolescents and may, in some instances, provide diagnoses in the absence of clinical findings.  相似文献   
999.
K M Klueber 《The Anatomical record》1987,219(4):370-3, 429-33
Although the reinnervation of muscle grafts has been demonstrated, the question remains as to the source of neurons reinnervating the graft. A muscle graft could be reinnervated by its original neurons (neural neurotization) or by sprouting of axons which supply the intact myofibers of surrounding muscles (muscle neurotization). The objective of this study was to evaluate the role of muscle neurotization in the reinnervation process using both horseradish peroxidase and fluorescent tracers. Observations from 20 muscle grafts indicate that the neurons reinnervating the grafts are from the original motor neuron pool. Thus muscle neurotization may not occur during the reinnervation process.  相似文献   
1000.
OBJECTIVE: To assess the impact of activity restriction (AR) on the incidence of preterm birth in women treated for preterm labor testing negative for fetal fibronectin (fFN). STUDY DESIGN: Women who were diagnosed with preterm labor and tocolyzed with magnesium sulfate were concurrently screened with fFN for the purpose of subsequent management. Included were consenting patients with negative fFN, gestational age 23 0/7-33 6/7 weeks, cervical dilation < or =3 cm, and minimal vaginal bleeding. Patients were randomized to AR or no AR. Primary study outcome was incidence of preterm delivery and interval from randomization to delivery. RESULTS: A total of 73 women with negative fFN were randomized (36 with AR, 37 without AR). The overall preterm birth rate was 40%, with 44.4% of patients with AR and 35.1% of patients without AR delivering preterm, p=0.478. CONCLUSION: Maternal AR did not impact pregnancy outcome. The incidence of preterm birth in symptomatic women testing fFN negative was higher than previously reported.  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