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   170392篇
  免费   6782篇
  国内免费   314篇
耳鼻咽喉   3062篇
儿科学   6394篇
妇产科学   4372篇
基础医学   24010篇
口腔科学   4796篇
临床医学   12724篇
内科学   31009篇
皮肤病学   4676篇
神经病学   15706篇
特种医学   8777篇
外国民族医学   24篇
外科学   28319篇
综合类   1090篇
一般理论   37篇
预防医学   7980篇
眼科学   4603篇
药学   11795篇
中国医学   348篇
肿瘤学   7766篇
  2023年   774篇
  2021年   1235篇
  2020年   1110篇
  2019年   1298篇
  2018年   2875篇
  2017年   2366篇
  2016年   3301篇
  2015年   3658篇
  2014年   3872篇
  2013年   5429篇
  2012年   8319篇
  2011年   7716篇
  2010年   4613篇
  2009年   3670篇
  2008年   7656篇
  2007年   8491篇
  2006年   8540篇
  2005年   8934篇
  2004年   8502篇
  2003年   8416篇
  2002年   8303篇
  2001年   6183篇
  2000年   6250篇
  1999年   5407篇
  1998年   1586篇
  1997年   1305篇
  1996年   999篇
  1995年   806篇
  1994年   748篇
  1992年   2393篇
  1991年   2316篇
  1990年   2278篇
  1989年   2125篇
  1988年   1858篇
  1987年   1844篇
  1986年   1708篇
  1985年   1647篇
  1984年   1284篇
  1983年   1023篇
  1979年   1382篇
  1978年   1017篇
  1977年   852篇
  1975年   1088篇
  1974年   1131篇
  1973年   1018篇
  1972年   1033篇
  1971年   1002篇
  1970年   887篇
  1969年   833篇
  1968年   802篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
251.
Abstrakt 1. Die Abgabe von Hilfsmitteln innerhalb einer Arztpraxis ist durch x 4 Nr. 11 UWG (n. F.) i. V. mit x 3 Abs. 2 BO nicht von vornherein ausgeschlossen, wenn dies aus medizinischen Gründen geschieht. 2. Ein etwaiger Versto? gegen sozialversicherungsrechtliche Vorschriften kann nicht als wettbewerbsrechtlich unlauter beurteilt werden; sozialversicherungsrechtliche Normen sind einer wettbewerbsrechtlichen Beurteilung entzogen.  相似文献   
252.
(18)F-Galacto-RGD has been developed for PET of alpha(v)beta(3) integrin expression, a receptor involved in, for example, angiogenesis and metastasis. Our aim was to study the kinetics and biodistribution of (18)F-Galacto-RGD in cancer patients. METHODS: Nineteen patients with metastases of malignant melanoma (n = 7), sarcomas (n = 10), or osseous metastases (n = 2) were examined. After injection of 133-200 MBq (18)F-Galacto-RGD, 3 consecutive emission scans from the pelvis to the thorax or dynamic emission scans of the tumor over 60 min, followed by 1 static emission scan of the body, were acquired. Time-activity curves and standardized uptake values (SUVs) were derived by image region-of-interest analysis with image-based arterial input functions. Compartmental modeling was used to derive the distribution volume for muscle tissue and tumors. RESULTS: (18)F-Galacto-RGD showed rapid blood clearance and primarily renal excretion. SUVs in tumors ranged from 1.2 to 9.0. Tumor-to-blood and tumor-to-muscle ratios increased over time, with peak ratios of 3.1 +/- 2.0 and 7.7 +/- 4.3, respectively, at 72 min. The tumor kinetics were consistent with a 2-tissue compartment model with reversible specific binding. Distribution volume values were, on average, 4 times higher for tumor tissue (1.5 +/- 0.8) than those for muscle tissue (0.4 +/- 0.1). The data suggest that there was only minimal free and bound (specific or nonspecific) tracer in muscle tissue. CONCLUSION: (18)F-Galacto-RGD demonstrates a highly favorable biodistribution in humans with specific receptor binding. Most important, this study shows that (18)F-Galacto-RGD allows visualization of alpha(v)beta(3) expression in tumors with high contrast. Consequently, this tracer offers a new strategy for noninvasive monitoring of molecular processes and may supply helpful information for planning and controlling of therapeutic approaches targeting the alpha(v)beta(3) integrin.  相似文献   
253.
Monitoring left ventricular dilation in mice with PET.   总被引:3,自引:0,他引:3  
Molecular imaging by small-animal PET is an important noninvasive means to phenotype transgenic mouse models in vivo. When investigating pathologies of the left ventricular (LV) myocardium, the serial assessment of LV volumes is important. By this, the presence of LV dilation as a sign of developing heart failure can be detected. Whereas PET is usually used to derive biochemical and molecular information, functional parameters such as ventricular volumes are generally measured using echocardiography or MRI. In this study, a novel method to monitor LV dilation in mice with PET is presented and evaluated using cardiac MRI. METHODS: A semiautomatic 3-dimensional algorithm was used to delineate the LV myocardial wall on static PET images depicting myocardial glucose metabolism ((18)F-FDG PET) for 20 mice: 10 wild-type and 10 genetically modified littermates designed to develop a dilative cardiomyopathy phenotype (cardiomyocyte-specific knockout of survivin). The volume enclosed by the 3-dimensional midmyocardial contour was calculated as a measure for LV volume for each mouse. Data were compared with ventricular volumes measured by MRI in the same animals. RESULTS: LV volumes obtained by PET and MRI correlated well (R = 0.89) for hearts with small and large left ventricles. In accordance with the hypothesis, the LV volumes were increased significantly for transgenic mice examined at an older age compared with those examined at a younger age (MRI: 160.5 +/- 25.7 microL vs. 114.7 +/- 15.2 microL [P = 0.012]; PET: 129.3 +/- 15.3 microL vs. 73.8 +/- 15.0 microL [P < 0.001], all values shown as mean +/- SD; for MRI, mean of end-diastolic and end-systolic volumes are given), whereas they did not for their wild-type littermates (MRI: 106.2 +/- 12.3 microL vs. 94.7 +/- 14.6 microL [P = 0.214]; PET: 82.6 +/- 20.9 microL vs. 65.0 +/- 16.9 microL [P = 0.185]). CONCLUSION: Evaluation and quantitation of LV dilation in both control and cardiomyopathic mice can be reliably and serially performed using small-animal PET and (18)F-FDG, yielding useful functional information in addition to metabolic data.  相似文献   
254.
255.
Reoperations for fractures of the proximal femur   总被引:1,自引:0,他引:1  
The number and type of reoperations after fractures of the proximal femur was studied in Jokilaakso Regional Hospital, Finland, from 1970 to 1981. Reoperations after fractures of the femoral neck occurred in 32% (24/74), in trochanteric fractures in 13% (6/48). In fractures of the femoral neck 38% (9/24) of the reoperations were performed during the first postoperative year, in trochanteric fractures half of the cases. The average time of hospital stay for reoperation was 19 days.  相似文献   
256.
257.
Bone morphogenetic proteins (BMPs) are bone growth factors, which regulate bone formation during fetal development and bone repair after injury in postfetal life. Since 1992 BMP-7 has been produced by recombinant technique (rhBMP-7). Numerous animal models and clinical trials have shown that rhBMP-7 can induce de novo bone formation in segmental defects of bones and in cases of nonunion. Since 2001 rhBMP-7 has been approved for treatment of tibial nonunion in Europe. The effect of rhBMP-7 is comparable to the clinical and radiological results achieved with bone autografts. The problem of donor site morbidity (which occurs in up to 20% of all cases) is eliminated by the use of BMP-7. Long-term results and experience in clinical practice are not yet available.  相似文献   
258.
Abstract Kyphoplasty and vertebroplasty have become recognized procedures for the treatment of vertebral fractures, especially in patients with osteoporosis. In most cases of osteoporotic spinal vertebral fracture in elderly patients, polymethylmethacrylate (PMMA) cement is used to fill the defect and stabilize the vertebral body. The techniques of vertebroplasty and kyphoplasty differ in the possibility of realignment and reconstruction of the vertebral body and spinal column. Long-term results in terms of integration of the cement and bioreactivity of the vertebral body are still lacking; so, these procedures are still no options in the treatment of younger patients. Vertebroplasty and kyphoplasty show different success in the management of fresh traumatic spine fractures. The acute traumatic vertebral fracture has to be classified sensitively, to find the right indication for cement augmentation. Mild acute compression fractures can be treated by vertebroplasty or kyphoplasty, severe compression and burst fractures by combination of internal fixation and kyphoplasty. The indications for use of biological or osteoinductive cement in spinal fracture management must still be regarded as restricted owing to the lack of basic biomechanical research data. Such cement should not be used except in clinical studies.  相似文献   
259.
260.
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