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   6925篇
  免费   455篇
  国内免费   16篇
耳鼻咽喉   107篇
儿科学   337篇
妇产科学   122篇
基础医学   1018篇
口腔科学   207篇
临床医学   420篇
内科学   1643篇
皮肤病学   161篇
神经病学   718篇
特种医学   194篇
外科学   952篇
综合类   23篇
一般理论   1篇
预防医学   611篇
眼科学   89篇
药学   375篇
中国医学   20篇
肿瘤学   398篇
  2023年   33篇
  2022年   69篇
  2021年   165篇
  2020年   86篇
  2019年   197篇
  2018年   215篇
  2017年   138篇
  2016年   113篇
  2015年   149篇
  2014年   193篇
  2013年   233篇
  2012年   390篇
  2011年   415篇
  2010年   240篇
  2009年   251篇
  2008年   375篇
  2007年   383篇
  2006年   396篇
  2005年   403篇
  2004年   377篇
  2003年   388篇
  2002年   318篇
  2001年   264篇
  2000年   280篇
  1999年   240篇
  1998年   68篇
  1997年   53篇
  1996年   58篇
  1995年   35篇
  1994年   25篇
  1993年   32篇
  1992年   120篇
  1991年   85篇
  1990年   81篇
  1989年   63篇
  1988年   46篇
  1987年   44篇
  1986年   41篇
  1985年   41篇
  1984年   35篇
  1983年   22篇
  1982年   16篇
  1979年   23篇
  1978年   20篇
  1976年   22篇
  1975年   21篇
  1974年   13篇
  1973年   19篇
  1972年   13篇
  1967年   14篇
排序方式: 共有7396条查询结果,搜索用时 11 毫秒
11.
The interlocking intramedullary nail has greatly expanded the indications for closed intramedullary nailing of the femur. We describe a complication caused by the presence of a calcified lesion located at the proximal metaphyseal-diaphyseal junction of the femur. This lesion could not be penetrated by hand reamers. We used a long 3.5-mm drill bit to place a hole in the infarct, which then allowed passage of the hand reamer. The operation then proceeded in the standard fashion without complications.  相似文献   
12.
PCR-based hybridization methods have been used to show that some women with normal cytology are carriers of HPV DNA of the types strongly related to cervical cancer. How these women should be managed remains unclear. This chapter selectively reviews reports which have estimated type-specific HPV prevalence in relation to the presence or absence of morphological signs of HPV infection. Overall, these reports indicate that among women who were identified as carriers of HPV DNA (by PCR-based methods) and who also had a normal cytological smear, the HPV type detected in the majority of instances was a high-risk viral type for cervical cancer (HPV types 16/18 = 44.7%; HPV types 31/33/35 = 8.1%; other and unknown types = 37.9%). This suggests that screening programmes which include PCR-based HPV detection could reduce the false negative rates currently reported by screening programmes based on cytology alone.  相似文献   
13.
Pancreatitis and hyperparathyroidism   总被引:2,自引:0,他引:2  
Hypercalcaemia is considered to be a rare cause of pancreatitis but the true cause-and-effect relationship between hyperparathyroidism and pancreatic inflammatory disease remains controversial. Over 100 patients have been reported in whom both processes have occurred concurrently, but doubts have been expressed as to whether or not this association is due to chance. We report 10 new cases of hypercalcaemic hyperparathyroidism associated with different types of pancreatitis. Seven patients had primary hyperparathyroidism and three had hyperparathyroidism after renal transplantation. Two experienced acute pancreatitis after parathyroidectomy. Of the remaining eight patients, five had hypercalcaemia equal to or above 120 mg/l. The prevalence of pancreatitis in our series of 86 cases of primary hyperparathyroidism is 8 per cent. Acute and chronic calcifying types of pancreatitis were observed. Three patients died of the disease, two of them after renal transplantation. It is suggested that pancreatitis may complicate the clinical course of hyperparathyroidism, particularly when hypercalcaemia is moderate to severe and/or there are other risk factors such as treatment with steroids and azathioprine after renal transplantation.  相似文献   
14.
BALB/c mice injected at birth with 10(8) semi-allogeneic (C57BL/6 x BALB.IgHb)F1 spleen cells develop a lupus-like syndrome in which autoantibodies bear exclusively the donor allotype. We have analyzed the evolution of donor B cell chimerism and the autoimmune manifestations during the first year of life in these mice. Anti-DNA, -histone, and -cardiolipin IgG antibodies as well as circulating immune complexes appeared in the second week of life, reached the highest values around the sixth week, and then progressively dropped to normal values after the sixth month in most mice. The kinetics of the evolution of the autoimmune manifestations, as well as the kinetics of serum donor Ig allotype, were parallel to the kinetics of donor B cell chimerism, which was particularly prominent in the spleens in early weeks of life, and progressively decreased after remission of the autoimmune syndrome. Membrane-proliferative glomerulonephritis, which was followed as the more representative histological abnormality in this model, was particularly evident after 10 weeks of life, but disappeared by the end of the follow-up. Interestingly, when mice with a self-limited disease were re-injected with 10(8) F1 spleen cells i.v., a flare in the serological manifestations was observed. In these re-injected mice a predominance of anti-DNA, IgG1 antibodies bearing exclusively the donor allotype was also observed, as in the early weeks of life.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
15.
16.
This study analyzed the effect of population aging on organ donation for transplants in 43 countries and on the effectiveness of the donation process by comparing the results between Spain and the United States. The percentage of the population aged 65 or over accounted for 33% of the difference in the donation rates between the countries and for 91% of the variation in the rates after age adjustment. However, the level of aging of the Spanish (16.5%) and American (12.3%) populations failed to account for the percentages of deceased donors 65 or over (28% vs. 10%), due to the different age-specific donation rates, much higher in Spain above 50 years. These differences lead to a higher effectiveness of the process in the United States (3.1 transplanted organs per donor vs. 2.5 in Spain), though at lower rates of transplant per million population (73 vs. 87). We conclude that older populations have a greater donation potential as donation rates are strongly associated with population aging. It should therefore be mandatory to adjust donation rates for age before making comparisons. Additionally, effectiveness decreases with older donors, so age should be considered when establishing standards relating to organ donation and effectiveness of the process.  相似文献   
17.
In response to traumatic brain injury (TBI), neurons initiate neuroplastic processes through the activation of intracellular signaling pathways. However, the molecular mechanisms underlying neuroplasticity after TBI are poorly understood. To study this, we utilized the fluid-percussion brain injury (FPI) model to investigate alterations in the mammalian target of rapamycin (mTOR) signaling pathways in response to TBI. Mammalian target of rapamycin stimulates mRNA translation through phosphorylation of eukaryotic initiation factor 4E binding protein-1 (4E-BP1), p70 ribosomal S6 kinase (p70S6K), and ribosomal protein S6 (rpS6). These pathways coordinate cell growth and neuroplasticity via dendritic protein synthesis. Rats received sham surgery or moderate parasagittal FPI on the right side of the parietal cortex, followed by 15 mins, 30 mins, 4 h, 24 h, or 72 h of recovery. Using Western blot analysis, we found that mTOR, p70S6K, rpS6, and 4E-BP1 phosphorylation levels were significantly increased in the ipsilateral parietal cortex and hippocampus from 30 mins to 24 h after TBI, whereas total protein levels were unchanged. Using confocal microscopy to localize these changes, we found that rpS6 phosphorylation was increased in the parietal cortex and all subregions of the hippocampus. In accordance with these results, eIF4E, a key, rate-limiting mRNA translation factor, was also phosphorylated by mitogen-activated protein kinase-interacting kinase 1 (Mnk1) 15 mins after TBI. Together, these results suggest that changes in mRNA translation may be one mechanism that neurons use to respond to trauma and may contribute to the neuroplastic changes observed after TBI.  相似文献   
18.
Familial hypercholesterolaemia is a frequent, inherited, monogenic disorder, associated with accelerated development of atherosclerotic disease leading to coronary artery disease. Life expectancy of patients with familial hypercholesterolaemia is reduced by 15-30 years unless they are adequately treated with lipid-lowering therapy. Given the chronic nature of this disease, the selection of a therapeutic approach should be strongly based on its long-term safety and tolerability. The introduction of HMG-CoA reductase inhibitors has revolutionised the treatment of familial hypercholesterolaemia.Simvastatin 40-80 mg/day effectively reduces serum low density lipoprotein (LDL)-cholesterol levels. Furthermore, simvastatin reduces triglycerides and mildly raises high density lipoprotein-cholesterol levels. In addition to the hypolipidaemic effect, other potentially important effects, such as improvement of endothelial function and reduction of LDL oxidation and vascular inflammation, have been associated with HMG-CoA reductase inhibitor therapy. Simvastatin has also been shown to abolish the progression, and even facilitate the regression, of existing human atherosclerotic lesions.The good safety and tolerability profile of simvastatin is clearly highlighted by the low rate of therapy discontinuation observed in several population-based clinical trials. The most common adverse events leading to the discontinuation of therapy are gastrointestinal upset and headache. Asymptomatic elevations in liver transaminase levels and myopathy are uncommon.The overwhelming clinical evidence regarding the long-term use of HMG-CoA reductase inhibitor therapy in patients with familial hypercholesterolaemia together with the long-term safety data (particularly relating to simvastatin) provide support for the use of this drug as a first-line agent when pharmacological treatment is indicated. Early intervention with simvastatin treatment can be successfully implemented with favourable economic benefits.  相似文献   
19.
Deficits in visual-spatial ability can be associated with Parkinson's disease (PD), and there are several possible reasons for these deficits. Dysfunction in frontal-striatal and/or frontal-parietal systems, associated with dopamine deficiency, might disrupt cognitive processes either supporting (e.g., working memory) or subserving visual-spatial computations. The goal of this study was to assess visual-spatial orientation ability in individuals with PD using the Mental Rotations Test (MRT), along with other measures of cognitive function. Non-demented men with PD were significantly less accurate on this test than matched control men. In contrast, women with PD performed similarly to matched control women, but both groups of women did not perform much better than chance. Further, mental rotation accuracy in men correlated with their executive skills involving mental processing and psychomotor speed. In women with PD, however, mental rotation accuracy correlated negatively with verbal memory, indicating that higher mental rotation performance was associated with lower ability in verbal memory. These results indicate that PD is associated with visual-spatial orientation deficits in men. Women with PD and control women both performed poorly on the MRT, possibly reflecting a floor effect. Although men and women with PD appear to engage different cognitive processes in this task, the reason for the sex difference remains to be elucidated.  相似文献   
20.
Regional cerebral blood flow (CBF) was studied with O(15)-water positron emission tomography and anatomic region-of-interest analysis on co-registered magnetic resonance in patients with idiopathic (n = 12) and secondary (n = 5) normal pressure hydrocephalus (NPH). Mean CBF was compared with values obtained from healthy volunteers (n = 12) and with clinical parameters. Mean CBF was significantly decreased in the cerebrum and cerebellum of patients with NPH. The regional analysis demonstrated that CBF was reduced in the basal ganglia and the thalamus but not in white matter regions. The results suggest that the role of the basal ganglia and thalamus in NPH may be more prominent than currently appreciated. The implications for theories regarding the pathogenesis of NPH are discussed.  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