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   3258篇
  免费   223篇
  国内免费   77篇
耳鼻咽喉   52篇
儿科学   138篇
妇产科学   73篇
基础医学   383篇
口腔科学   68篇
临床医学   328篇
内科学   696篇
皮肤病学   80篇
神经病学   238篇
特种医学   368篇
外科学   317篇
综合类   96篇
预防医学   314篇
眼科学   35篇
药学   202篇
中国医学   5篇
肿瘤学   165篇
  2021年   29篇
  2019年   42篇
  2018年   37篇
  2016年   29篇
  2015年   45篇
  2014年   39篇
  2013年   76篇
  2012年   109篇
  2011年   115篇
  2010年   93篇
  2009年   106篇
  2008年   102篇
  2007年   133篇
  2006年   113篇
  2005年   114篇
  2004年   85篇
  2003年   87篇
  2002年   86篇
  2001年   79篇
  2000年   80篇
  1999年   62篇
  1998年   109篇
  1997年   90篇
  1996年   82篇
  1995年   76篇
  1994年   69篇
  1993年   63篇
  1992年   81篇
  1991年   71篇
  1990年   84篇
  1989年   86篇
  1988年   87篇
  1987年   74篇
  1986年   66篇
  1985年   81篇
  1984年   59篇
  1983年   51篇
  1982年   44篇
  1981年   33篇
  1980年   41篇
  1979年   44篇
  1978年   44篇
  1977年   41篇
  1976年   43篇
  1975年   42篇
  1974年   29篇
  1973年   48篇
  1972年   41篇
  1971年   28篇
  1969年   27篇
排序方式: 共有3558条查询结果,搜索用时 15 毫秒
61.
Persistent hyperinsulinemic hypoglycaemia of infancy (PHHI) is the most frequent cause of hypoglycaemia in infancy. Clinical presentation is heterogeneous, with variable onset of hypoglycaemia and response to diazoxide, and presence of sporadic or familial forms. Underlying histopathological lesions can be focal or diffuse. Focal lesions are characterised by focal hyperplasia of pancreatic islet-like cells, whereas diffuse lesions implicate the whole pancreas. The distinction between the two forms is important because surgical treatment and genetic counselling are radically different. Focal lesions correspond to somatic defects which are totally cured by limited pancreatic resection, whereas diffuse lesions require a subtotal pancreatectomy exposing to high risk of diabetes mellitus. Diffuse lesions are due to functional abnormalities involving several genes and different transmission forms. Recessively inherited PHHI have been attributed to homozygote mutations for the beta-cell sulfonylurea receptor (SUR1) or the inward-rectifying potassium-channel (Kir6.2) genes. Dominantly inherited PHHI can implicate the glucokinase gene, particularly when PHHI is associated with diabetes, the glutamate dehydrogenase gene when hyperammonaemia is associated, or another locus.  相似文献   
62.
A perfect metabolic correction of diabetes is essential to completely eradicate long-term chronic complications. Only a total pancreatic graft with portal venous drainage enables such an achievement. Isogenic Lewis rats were used for donors, recipients and controls. Pancreatico-duodenal transplantation was either heterotopic with systemic venous drainage (n = 12) or paratopic with portal drainage (n = 11). All animals were regularly monitored for non-fasting plasma glucose and insulin. Both techniques promptly restored the non-fasting plasma glucose to normal values (p<0.003). Normo-insulinemia (47.4+/-6.4 microU/ml) was obtained in the paratopic group, while the heterotopic group showed hyperinsulinism (132.0+/-15.2 microU/ml). Perfect metabolic control justifies the additional technical difficulties of total paratopic pancreatic transplantation with portal venous drainage.  相似文献   
63.
The authors studied 10 consecutive patients with closed femoral shaft or supracondylar fractures who were nonambulatory and who were treated by reamed retrograde intramedullary nailing via an intercondylar notch approach. The study consisted of five women and five men with an average age of 60.7 years (range, 40-89 years). Six patients had spinal cord lesions, one had a brain injury, one had cerebral palsy, one had multiple sclerosis, and one had progressive myelopathy. Three fractures were supracondylar, and seven fractures involved the mid-distal diaphysis. The average time of surgery was 110 minutes (range, 70-225 minutes) with an average estimated blood loss of 288 mL (range, 150-400 mL). There were two postoperative deaths (at 15 days and 2 months, respectively) after the procedure that were attributable to pneumonia. The remaining eight patients were observed for an average of 13 months (range, 6-20 months) after surgery. All fractures healed as evaluated radiographically. Retrograde intramedullary nailing is a simple, safe, and effective alternative to nonoperative treatment for femoral shaft or supracondylar fractures in patients who are nonambulatory. Stabilization by this method allows fracture healing and rapid return of patients to their previous level of function. There were no nonunions, malunions, significant shortening, implant failure, or wound infections.  相似文献   
64.
65.
66.
The aims were to determine the median survival and prognostic factors of patients with central nervous system (CNS) metastases managed with whole‐brain radiation therapy (WBRT), and to explore selection criteria in recently published clinical trials using aggressive interventions in CNS metastases. A retrospective audit was performed on patients managed with WBRT for CNS metastases. Potential prognostic factors were recorded and analysed for their association with survival duration. The proportion of patients with these factors was also compared with those of patients managed under three recently reported studies investigating aggressive interventions, such as radiosurgery and chemotherapy for CNS metastases. Seventy‐three patients were treated with WBRT for cerebral metastases over a 12‐month period. The median survival of the population was 3.4 months (95% confidence interval: 2.7–4.1), with 6‐ and 12‐month survival rates of 30 and 18%, respectively. Significant prognostic factors for prolonged median survival were Eastern Cooperative Oncology Group status 0–2 (P = 0.015), Medical Research Council neurological functional status 0–1 (P = 0.006), and Recursive Partitioning Analysis Class 2 versus Class 3 (P = 0.020). On multivariate analysis, younger patient age (P = 0.02) and better performance status (P < 0.01) were associated with improved outcome. When comparing these characteristics with selected published studies, our study cohort demonstrated a higher proportion of patients with poor performance status, a greater number of metastases per patient and a higher incidence of extracranial disease. This reflects the selected nature of patients in these published studies. Central nervous system metastases confer a poor prognosis and, for the majority of patients, aggressive interventions are unlikely to improve survival. The use of potentially toxic and expensive treatments should be reserved for those few in whom these studies have shown a potential benefit.  相似文献   
67.
68.
Two different classes of neoplastic T cells were isolated from radiation leukemia virus (RadLV)-inoculated and from X-ray-treated C57BL/6 mice. One consisted of growth factor-dependent T-cell lymphoma (FD-TCL) lines which were established from the spleens and thymuses of treated mice within a day of lymphoma detection. FD-TCL cells were often eudiploid and could be grown in pure culture only at high concentrations, or on stromal feeder layers. Non-thymic, factor-dependent TCL cells produced interleukin-2 upon lectin stimulation, and were autostimulatory because they secreted growth factor(s) constitutively. Single cell cloning of FD-TCL cells in semisolid medium required the addition of exogenous conditioned medium. In vivo, FD-TCL cells that were injected intraperitoneally or intravenously homed to the spleen, proliferated in it and killed the injected mice. FD-TCL cells did not produce local tumors at the site of subcutaneous injection. The isolation and study of FD-TCL cells was facilitated by their cultivation on stromal hematopoietic monolayers in supplemented "lymphocyte medium", until an autostimulating, self-sustaining concentration of FD-TCL cells was obtained. FD-TCL cells could not be grown from lymphoid tissue of normal, control mice. In contrast, T-cell lymphoma (TCL) lines, which were established from virus-induced thymomas which had been kept in situ for 4-6 weeks after detection, consisted of factor-independent cells that possessed an aneuploid karyotype (in some cases trisomic for chromosome No. 15), and produced local tumors at the site of subcutaneous injection. These cells could be cloned in semisolid medium without addition of exogenous factor(s). The phenotypic markers of TCL cells differed from those of FD-TCL cells, suggesting heterogeneity in the stages of differentiation at which cells can give rise to growth factor-independent (TCL) and to growth factor-dependent (FD-TCL) lines.  相似文献   
69.
异一枝蒿酮酸的结构   总被引:3,自引:0,他引:3  
从新疆一枝蒿(Artemisia rupestris L.)中分得一个新成分,命名为异一枝蒿酮酸(isorupestonic acid),根据光谱(IR,UV,MS.NMR),X-ray晶体衍射及CD谱分析,确定其结构及绝对构型。并经X-ray晶体衍射及CD谱分析修正了一枝蒿酮酸的绝对构型。  相似文献   
70.
This study was performed to determine the safety and efficacy of intravenous contrast echocardiography in children attending a tertiary cardiac center. This was a prospective study to evaluate the use of Optison contrast agent in children with severely limited transthoracic echocardiographic windows. Twenty children (median age, 15 years; range, 9–18) underwent fundamental imaging (FI), harmonic imaging (HI), and HI with intravenous contrast (Optison FS-069). Endocardial border delineation was determined based on a visual qualitative scoring system (0, none: 4, excellent). Endocardial border definition was significantly improved in all patients using contrast echocardiography (FI vs Optison, p < 0.001 for each). Improved border definition was most dramatic in the apical and left ventricular (LV) free wall regions. Left ventricular ejection fraction (LVEF) was measurable in 20 patients (100%) using contrast compared to 11 (55%) with FI or HI (p < 0.05). The echocardiographic diagnosis was correctly delineated in 1 patient with a severely dyskinetic LV segment only with use of intravenous contrast and HI. No patients suffered adverse hemodynamic effects, changes in taste, or flushing episodes. Three patients experienced transient headaches. Intravenous contrast echocardiography offers an additional tool in evaluating children with very poor transthoracic echocardiographic windows. Such a strategy increases diagnostic accuracy and allows accurate LVEF determination. Adverse hemodynamic effects related to intravenous contrast are exceedingly rare.  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