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   9806篇
  免费   523篇
  国内免费   48篇
耳鼻咽喉   169篇
儿科学   456篇
妇产科学   234篇
基础医学   998篇
口腔科学   219篇
临床医学   788篇
内科学   2209篇
皮肤病学   157篇
神经病学   689篇
特种医学   336篇
外科学   1951篇
综合类   185篇
一般理论   4篇
预防医学   534篇
眼科学   192篇
药学   580篇
中国医学   36篇
肿瘤学   640篇
  2023年   80篇
  2022年   189篇
  2021年   381篇
  2020年   246篇
  2019年   277篇
  2018年   353篇
  2017年   217篇
  2016年   271篇
  2015年   290篇
  2014年   423篇
  2013年   573篇
  2012年   788篇
  2011年   792篇
  2010年   444篇
  2009年   375篇
  2008年   591篇
  2007年   645篇
  2006年   598篇
  2005年   515篇
  2004年   469篇
  2003年   413篇
  2002年   345篇
  2001年   113篇
  2000年   98篇
  1999年   81篇
  1998年   53篇
  1997年   27篇
  1996年   40篇
  1995年   47篇
  1994年   37篇
  1993年   39篇
  1992年   57篇
  1991年   59篇
  1990年   44篇
  1989年   53篇
  1988年   39篇
  1987年   41篇
  1986年   34篇
  1985年   29篇
  1984年   29篇
  1983年   16篇
  1981年   22篇
  1980年   16篇
  1979年   10篇
  1978年   10篇
  1977年   13篇
  1974年   8篇
  1973年   9篇
  1972年   9篇
  1967年   15篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
3.
The present investigation was aimed at studying the possible role of curcumin against N-nitrosodiethylamine (NDEA)-induced toxicity in albino rats. Administration of NDEA to rats at a concentration of 0.1 mg/ml in drinking water ad libitum for 21 days produced toxicity in them, which was evident from histopathological changes in the rat livers, and increased levels of blood serum enzyme markers, i.e. aspartate transaminase, alanine transaminase, alkaline phosphatase, and lactate dehydrogenase. In addition, the levels of oxidative stress markers like lipid peroxidation (LPO), protein carbonyl (PCC), and glutathione-S-transferase (GST) activity were elevated and the total glutathione (GSH) content was reduced in the livers. The administration of curcumin to rats at concentrations of 10, 20, and 40 mg/ml in drinking water along with 0.1 mg/ml of NDEA for 21 days effectively suppressed NDEA-induced toxicity and also resulted in a dose-dependent reduction in the levels of blood serum enzyme markers (AST, ALT, ALP, and LDH). Moreover, LPO, PCC, and GST activity were reduced and the GSH level was increased upon the administration of curcumin along with NDEA. The results obtained for the comet assay in rat hepatocytes and blood lymphocytes showed a significant dose-dependent decrease in the mean tail length. The micronucleus assay performed on rat hepatocytes also showed a dose-dependent reduction in the frequency of micronucleated cells along with curcumin administration. These results suggest that curcumin has a protective role against NDEA-induced toxicity in albino rats.  相似文献   
4.
Objectives:To assess cerebral venous thrombosis risk factors, and associated clinical outcomes in Jazan region, Kingdom of Saudi Arabia.Methods:This study is a retrospective review of the medical records of patients diagnosed with cerebral venous thrombosis and admitted to King Fahad Central Hospital in Jazan between 2010 and 2019. Data concerning socio-demographics, clinical features, risk factors, laboratory, and imaging investigations were retrieved. Furthermore, data about cases management, and outcomes, including death, were collected and analysed.Results:A total of 51 medical records were identified. The majority of the patients were females (68.6%), and the mean age of the patients was 33.3 years, of which three patients were under 18 years old. The most frequently recorded symptom was headache (76.5%), followed by seizure (45.1%). The most commonly recorded risk factor was protein S deficiency (57%), followed by anaemia (51%). Venous infarction and haemorrhage were the most common acute complications (13.7%). The majority of the patients had a favourable prognosis where only 27.5% recovered with disability and only one patient died due to the disease.Conclusion:Clinical presentation of cerebral venous thrombosis in Jazan region is similar to other local and international studies. However, anaemia was recorded as a main risk factor for the disease, which might require further investigation to assess the possible association between prevalence of anaemia in Jazan region and the incidence of cerebral venous thrombosis.

Cerebral venous thrombosis (CVT) is a rare form of cerebrovascular disease in comparison with arterial stroke. CVT cases represent approximately 0.5-1% of all types of stroke which mainly occur in young and middle-aged adults.1 The data concerning the global epidemiology of CVT is currently limited.2 However, the incidence of CVT has been reported to vary between countries where the incidence might be higher as in Asian and the Middle Eastern countries in comparison to Australia and European countries.3According to a recent study conducted in Australia, the incidence of CVT was reported to reach 15.7 per 1,000,000 persons on a yearly basis. The incidence was higher among women and among those between 31-50 years old.4 In the Middle East, an Iranian study looked at the frequency of CVT between 2001 and 2004, and the annual frequency of CVT was 12.3 per one million.5 An older study, conducted in the city of Riyadh in Saudi Arabia between 1985 and 1994, identified 40 cases of CVT. Those identified were aged between 16 and 40.6 In addition, in a more recent study conducted in Jeddah and Al-Baha between 1990 and 2010, the number of detected cases of CVT was 111 where 19 of these were detected among children.7The CVT occurs when a thrombus develops as a result of a disturbance of the balance between the process of prothrombosis and thrombolysis.8,9 Risk factors for CVT can be categorised into transient and permanent risk factors. Permanent risk factors are hereditary thrombophilia, systemic diseases or miscellaneous factors, such as obesity. Transient risk factors can be subcategorised into sex-specific, iatrogenic, or miscellaneous risk factors, such as infection, head trauma or anaemia.8 The prevalence of CVT risk factors differs between countries. Infection, pregnancy, post-partum period, and dehydration have been reported to be more common in Asia and the Middle Eastern countries in comparison to European countries.8Patients with CVT exhibit variable clinical manifestations and complications, some of which can be life threatening. The most common clinical presentation is a headache, while some patients exhibit other signs and symptoms, such as seizure, decreased level of consciousness, vomiting, focal neurological deficit, or visual symptoms.8-10 Venous infarction and haemorrhage are frequently reported complications of CVT.11 Late presentation of CVT patients can increase the risk of disability and death. The mortality rate among CVT patients has been reported to vary between 4.3% and 6.8%.12Since CVT risk factors and vulnerable groups can vary between different populations, assessment of the distribution of risk factors among local populations can be clinically valuable. Studies assessing CVT prevalence and associated risk factors and clinical outcomes in Saudi populations are currently limited. Furthermore, data about CVT in Jazan region is currently lacking. This investigation aims to identify cases diagnosed with CVT in Jazan region and to evaluate the risk factors and associated clinical outcomes.  相似文献   
5.
Harinakshi Sanikini  David C. Muller  Marisa Sophiea  Sabina Rinaldi  Antonio Agudo  Eric J. Duell  Elisabete Weiderpass  Kim Overvad  Anne Tjønneland  Jytte Halkjær  Marie-Christine Boutron-Ruault  Franck Carbonnel  Iris Cervenka  Heiner Boeing  Rudolf Kaaks  Tilman Kühn  Antonia Trichopoulou  Georgia Martimianaki  Anna Karakatsani  Valeria Pala  Domenico Palli  Amalia Mattiello  Rosario Tumino  Carlotta Sacerdote  Guri Skeie  Charlotta Rylander  María-Dolores Chirlaque López  Maria-Jose Sánchez  Eva Ardanaz  Sara Regnér  Tanja Stocks  Bas Bueno-de-Mesquita  Roel C.H. Vermeulen  Dagfinn Aune  Tammy Y.N. Tong  Nathalie Kliemann  Neil Murphy  Marc Chadeau-Hyam  Marc J. Gunter  Amanda J. Cross 《International journal of cancer. Journal international du cancer》2020,146(4):929-942
Obesity has been associated with upper gastrointestinal cancers; however, there are limited prospective data on associations by subtype/subsite. Obesity can impact hormonal factors, which have been hypothesized to play a role in these cancers. We investigated anthropometric and reproductive factors in relation to esophageal and gastric cancer by subtype and subsite for 476,160 participants from the European Prospective Investigation into Cancer and Nutrition cohort. Multivariable hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox models. During a mean follow-up of 14 years, 220 esophageal adenocarcinomas (EA), 195 esophageal squamous cell carcinomas, 243 gastric cardia (GC) and 373 gastric noncardia (GNC) cancers were diagnosed. Body mass index (BMI) was associated with EA in men (BMI ≥30 vs. 18.5–25 kg/m2: HR = 1.94, 95% CI: 1.25–3.03) and women (HR = 2.66, 95% CI: 1.15–6.19); however, adjustment for waist-to-hip ratio (WHR) attenuated these associations. After mutual adjustment for BMI and HC, respectively, WHR and waist circumference (WC) were associated with EA in men (HR = 3.47, 95% CI: 1.99–6.06 for WHR >0.96 vs. <0.91; HR = 2.67, 95% CI: 1.52–4.72 for WC >98 vs. <90 cm) and women (HR = 4.40, 95% CI: 1.35–14.33 for WHR >0.82 vs. <0.76; HR = 5.67, 95% CI: 1.76–18.26 for WC >84 vs. <74 cm). WHR was also positively associated with GC in women, and WC was positively associated with GC in men. Inverse associations were observed between parity and EA (HR = 0.38, 95% CI: 0.14–0.99; >2 vs. 0) and age at first pregnancy and GNC (HR = 0.54, 95% CI: 0.32–0.91; >26 vs. <22 years); whereas bilateral ovariectomy was positively associated with GNC (HR = 1.87, 95% CI: 1.04–3.36). These findings support a role for hormonal pathways in upper gastrointestinal cancers.  相似文献   
6.
7.
Metabolomics may reveal novel insights into the etiology of prostate cancer, for which few risk factors are established. We investigated the association between patterns in baseline plasma metabolite profile and subsequent prostate cancer risk, using data from 3,057 matched case–control sets from the European Prospective Investigation into Cancer and Nutrition (EPIC). We measured 119 metabolite concentrations in plasma samples, collected on average 9.4 years before diagnosis, by mass spectrometry (AbsoluteIDQ p180 Kit, Biocrates Life Sciences AG). Metabolite patterns were identified using treelet transform, a statistical method for identification of groups of correlated metabolites. Associations of metabolite patterns with prostate cancer risk (OR1SD) were estimated by conditional logistic regression. Supplementary analyses were conducted for metabolite patterns derived using principal component analysis and for individual metabolites. Men with metabolite profiles characterized by higher concentrations of either phosphatidylcholines or hydroxysphingomyelins (OR1SD = 0.77, 95% confidence interval 0.66–0.89), acylcarnitines C18:1 and C18:2, glutamate, ornithine and taurine (OR1SD = 0.72, 0.57–0.90), or lysophosphatidylcholines (OR1SD = 0.81, 0.69–0.95) had lower risk of advanced stage prostate cancer at diagnosis, with no evidence of heterogeneity by follow-up time. Similar associations were observed for the two former patterns with aggressive disease risk (the more aggressive subset of advanced stage), while the latter pattern was inversely related to risk of prostate cancer death (OR1SD = 0.77, 0.61–0.96). No associations were observed for prostate cancer overall or less aggressive tumor subtypes. In conclusion, metabolite patterns may be related to lower risk of more aggressive prostate tumors and prostate cancer death, and might be relevant to etiology of advanced stage prostate cancer.  相似文献   
8.
9.
The first observations of altered metabolism in malignant cells were made nearly 100 years ago and therapeutic strategies targeting cell metabolism have been in clinical use for several decades.  In this review, we summarize our current understanding of cell metabolism dysregulation in childhood acute lymphoblastic leukemia (cALL). Reprogramming of cellular bioenergetic processes can be expected in the three distinct stages of cALL: at diagnosis, during standard chemotherapy, and in cases of relapse. Upregulation of glycolysis, dependency on anaplerotic energy sources, and activation of the electron transport chain have all been observed in cALL. While the current treatment strategies are tackling some of these aberrations, cALL cells are likely to be able to rewire their metabolism in order to escape therapy, which may contribute to a refractory disease and relapse. Finally, here we focus on novel therapeutic approaches emerging from our evolving understanding of the alterations of different metabolic networks in lymphoblasts.  相似文献   
10.
Low molecular weight heparins are widely used in the prophylaxis and treatment of thrombotic disorders. The effect of low molecular weight heparins on coagulation was examined ultrastructurally in an animal model. A test and a control group was formed, each consisting of five rabbits. Nadroparine (225 Institute of Chaoy Unit/kg twice daily) was applied to the test group for 10 days. The control group received 1 ml saline solution subcutaneously. Blood and vascular tissue samples collected at the end of the 10th day were evaluated under a JEM 100 B electron microscope. Platelet degranulation and agglutination was observed in the control group. Fibrin materials were detected in the cytoplasms and surroundings of degranulated platelets. Erythrocyte accumulation was remarkable on the vascular endothelium with intact coagulation periods. In the test group, outer membranes of platelets, hyalomere, and granular structures in the granulomeres were detected to be nearly intact. There were rare erythrocytes in the large vascular lumens. The aggregation phase had occurred but no agglutination was detected. Nadroparine seems to preserve consistency of lipoprotein membranes of platelets and granular structures containing enzymes, which contribute to the coagulation mechanisms.  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