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   45949篇
  免费   4666篇
  国内免费   52篇
耳鼻咽喉   342篇
儿科学   1596篇
妇产科学   1283篇
基础医学   6395篇
口腔科学   837篇
临床医学   6057篇
内科学   8279篇
皮肤病学   697篇
神经病学   4177篇
特种医学   1593篇
外国民族医学   5篇
外科学   5271篇
综合类   901篇
一般理论   61篇
预防医学   6066篇
眼科学   1053篇
药学   3177篇
中国医学   54篇
肿瘤学   2823篇
  2023年   303篇
  2022年   385篇
  2021年   963篇
  2020年   607篇
  2019年   990篇
  2018年   1023篇
  2017年   822篇
  2016年   840篇
  2015年   914篇
  2014年   1226篇
  2013年   1832篇
  2012年   2579篇
  2011年   2532篇
  2010年   1451篇
  2009年   1274篇
  2008年   2185篇
  2007年   2329篇
  2006年   2246篇
  2005年   2094篇
  2004年   2037篇
  2003年   1889篇
  2002年   1793篇
  2001年   1276篇
  2000年   1249篇
  1999年   1084篇
  1998年   520篇
  1997年   450篇
  1996年   424篇
  1995年   357篇
  1994年   386篇
  1993年   356篇
  1992年   849篇
  1991年   821篇
  1990年   791篇
  1989年   700篇
  1988年   713篇
  1987年   673篇
  1986年   615篇
  1985年   675篇
  1984年   560篇
  1983年   435篇
  1982年   290篇
  1981年   302篇
  1980年   282篇
  1979年   474篇
  1978年   355篇
  1976年   291篇
  1974年   295篇
  1973年   270篇
  1972年   273篇
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
71.
The skeletal effects from intensive exercise throughout puberty are undefined. Forty-five female gymnasts and 52 controls were studied over 3 years, including a heredity aspect. The effects of size, maturity, exercise, and diet were identified using a multilevel regression model. Results demonstrated sustained skeletal benefits resulting from exercise throughout all stages of pubertal development. INTRODUCTION: Weight-bearing exercise is beneficial for peak bone mass development. However, whether skeletal benefits achieved with exercise are maintained if training remains intensive throughout the pubertal years is not entirely clear. The influence of familial resemblance for bone mass remains undefined in physically active versus inactive children. The aim of this study was to investigate the long-term influences of impact-loading exercise on bone quantity and quality in young females after controlling for growth, maturation, and hereditary factors. MATERIALS AND METHODS: At baseline, 45 gymnasts (G) and 52 normally active controls (C) 8-17 years of age were recruited. Anthropometry, diet, physical activity, and quantitative ultrasound (QUS) were measured annually for 3 consecutive years. DXA scans of total body (TB) and lumbar spine (LS) bone mineral content (BMC) and density (BMD) were taken three times at 1-year intervals. A multilevel regression model was fitted, and the independent effects of body size, maturity, physical activity, and diet were identified over time. To assess heredity influences, 27 G mothers and 26 C mothers volunteered for cross-sectional measurements of anthropometry, QUS, and BMC/BMD. RESULTS AND CONCLUSIONS: Gymnasts were smaller and lighter (as were their mothers) than controls, but they had significantly higher QUS and axial and appendicular BMC and BMD, with > 170 g more bone mineral in TB across puberty (after adjustment for maturity [years from peak height velocity], height, weight, energy, and protein intake). Gymnasts had up to 24-51% higher BMC and 13-28% higher BMD, depending on skeletal site. These results provide evidence of sustained skeletal benefits from impact-loading exercise, which are unlikely to result entirely from heredity, throughout pubertal years.  相似文献   
72.
73.
A total of 586 admissions for 12 medical conditions were reviewed. The stay of children accompanied by a resident parent was 31% shorter than those whose parents were not resident. Resident parents benefit the emotional well being of the child and increase hospital efficiency; accommodation for parents should therefore be an integral part of a unit admitting children.  相似文献   
74.
Progressive, cystic tumor enlargement in the abdomen developed in a patient with teratocarcinoma during treatment with systemic chemotherapy. Tumor markers were elevated in the cyst fluid and negative in serum. Further, the patient underwent a successful surgical debulking of large amounts of cystic teratoma.  相似文献   
75.
BACKGROUND: Pre-clinical and clinical studies suggest that transplantation of bone marrow-derived stem cells can improve global cardiac function. However, no quantitative assessment of regional systolic contraction and correlation with phenotype has been made. Therefore, we used our model of cryoinfarcted rabbit myocardium for intracardiac transplantation of a mixed population of bone marrow-derived cells and assessed both regional function and myogenic conversion of the cells. METHODS: Nineteen New Zealand white rabbits underwent cryoinjury of the left ventricle. Autologous bone marrow (BM) cells were expanded in vitro. After 2 weeks, either 1 x 10(8) mixed BM-derived progenitor cells (BM group, n = 11) or vehicle (control group, n = 8) were injected into the cryoinjured region. Regional systolic function was measured using micromanometry and sonomicrometry before and 4 weeks after cell injection; cell phenotype was evaluated histologically. RESULTS: All animals in the BM group significantly improved both systolic shortening (0.11 +/- 0.7 vs -0.05 +/- 0.05 mm in the control group, p < 0.05) and regional stroke work when compared with control (9.6 +/- 2.4 vs -1.2 +/- 1.2 mm . mm Hg, p < 0.003). In addition, the BM group had improved global diastolic function, as measured by minimum dP/dt and end-diastolic pressure. On histologic assessment, BM cells differentiated toward a myogenic phenotype. CONCLUSIONS: Transplanting a mixed population of marrow-derived cells that can adopt a myogenic phenotype improves regional contractility and diastolic relaxation after myocardial infarction.  相似文献   
76.
OBJECTIVE: The development of acute renal failure following cardiac surgery is a rare but devastating complication with high morbidity and mortality. This study aimed to assess the incidence of acute renal failure necessitating continuous renal replacement therapy (CRRT) in patients who required cardiopulmonary bypass, to determine the factors associated with mortality and to evaluate long-term outcome. METHODS: Patients who underwent cardiac surgery between October 1997 and 2003 and treated with CRRT were included (n=98). Six patients were then excluded (already in established renal failure pre-operatively) and one patient lost to follow-up. A retrospective analysis was carried out. RESULTS: Overall CRRT was used in 2.9% (92/3172). The mean (SD) age of patients was 68 (10) years. Their mean pre-operative creatinine level and duration of cardiopulmonary bypass were 154 (87)micromol/l and 160 (84)min, respectively. Mean duration from surgery to establishment of CRRT was 50 (42)h. Mean creatinine level prior to hospital discharge was 168 (93)micromol/l. Thirty-day mortality was 42%. Significant risk factors for death were complex procedures (odds ratio=9.9), gastro-intestinal complications (OR=7.2), cross-clamp time over 88min (OR=5.9), re-exploration (OR=4.0) and patients age over 75 years (OR=3.3). Actuarial 1 and 5-year survivals (95% CI) were 53 (43, 63) % and 52 (42, 62) %, respectively. Only 2 (2.2%) patients required long term renal support. CONCLUSIONS: Acute renal failure necessitating the use of CRRT is a rare but serious complication post cardiopulmonary bypass. In the long-term, surviving patients are not likely to require further renal support.  相似文献   
77.
BACKGROUND: Merkel cell carcinoma is a rare malignant neuroendocrine neoplasm characteristically arising from the dermis of sunlight-exposed skin. It rarely arises outside the skin. OBJECTIVE: We present a patient with primary Merkel cell carcinoma arising from subcutaneous fat, with no involvement of the overlying skin. We describe the clinical manifestations and magnetic resonance imaging (MRI) findings. METHODS: We report a 63-year-old woman with a primary lesion of Merkel cell carcinoma that arose from the subcutaneous fat layer of the left arm. The lesion presented as a subcutaneous nodule with intact overlying skin. MRI showed that the nodular lesion was located entirely in the subcutaneous fat layer, with no involvement of the dermis. Peritumoral infiltration around the lesion and enlarged lymph nodes deep to the lesion were noted. The patient received wide excision of the lesion with dissection of the regional lymph nodes and adjuvant radiotherapy and chemotherapy. RESULTS: Histopathologic examination confirmed the diagnosis of Merkel cell carcinoma with local lymphatic metastasis, and the lesion was completely located in the subcutaneous fat, with no involvement of the dermis. These findings were well correlated with MRI findings. CONCLUSION: Primary Merkel cell carcinoma may arise from the subcutaneous fat and present as an entirely subcutaneous lesion with intact skin. MRI is helpful to evaluate the local extension of the lesion and regional lymphatic metastasis.  相似文献   
78.
79.
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