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   843篇
  免费   58篇
  国内免费   3篇
耳鼻咽喉   5篇
儿科学   102篇
妇产科学   19篇
基础医学   102篇
口腔科学   17篇
临床医学   47篇
内科学   167篇
皮肤病学   12篇
神经病学   35篇
特种医学   16篇
外科学   83篇
综合类   48篇
预防医学   71篇
眼科学   33篇
药学   94篇
中国医学   4篇
肿瘤学   49篇
  2023年   4篇
  2022年   18篇
  2021年   32篇
  2020年   10篇
  2019年   12篇
  2018年   27篇
  2017年   16篇
  2016年   16篇
  2015年   21篇
  2014年   28篇
  2013年   36篇
  2012年   49篇
  2011年   60篇
  2010年   34篇
  2009年   27篇
  2008年   47篇
  2007年   60篇
  2006年   39篇
  2005年   28篇
  2004年   33篇
  2003年   27篇
  2002年   29篇
  2001年   15篇
  2000年   10篇
  1999年   15篇
  1998年   6篇
  1995年   8篇
  1994年   4篇
  1993年   11篇
  1992年   13篇
  1991年   8篇
  1990年   7篇
  1989年   4篇
  1988年   9篇
  1987年   12篇
  1986年   4篇
  1985年   8篇
  1984年   7篇
  1983年   4篇
  1981年   7篇
  1978年   5篇
  1977年   5篇
  1974年   3篇
  1973年   9篇
  1972年   5篇
  1971年   7篇
  1970年   5篇
  1969年   8篇
  1968年   4篇
  1967年   7篇
排序方式: 共有904条查询结果,搜索用时 15 毫秒
891.
Dengue is an arboviral disease and occurs in tropical countries where over 2.5 billion people are at risk of infection. Each year an estimated 100 million cases of dengue fever (DF) occur and between 2.5 and 5 lakh cases of dengue hemorrhagic fever (DHF) are reported to WHO. Severe thrombocytopenia and increased vascular permeability are two major characteristics of DHF. A study was conducted to note the relationship between the platelet counts and severity of the disease in pediatric cases of dengue fever. Platelet counts were found to be predictive as well as recovery parameter of DF/DHF/DSS.  相似文献   
892.

Objective

Menopause, an estrogen deficient state, is known to increase the cardiovascular risk. Lipid changes accompanying menopause account for only few cases of coronary artery disease (CAD). Endothelium-dependent nitric oxide-mediated vasodilatory mechanisms are also known to play a role in development of coronary artery disease, but studies in menopausal women are very few. This study was hence undertaken to see if nitric oxide (NO)–cyclic guanidine monophosphate (c-GMP) pathway is influenced by menopause.

Design

This study was a hospital-based case–control study involving 100 women in age group 40–55 years. Of these, 50 women were postmenopausal and 50 were premenopausal. Women with known risk factors for CAD were excluded. Fasting blood samples from these women were collected and analyzed for estradiol levels, lipid profile, apolipoprotein B, plasma nitric oxide, c-GMP and platelet nitric oxide using standard kits and reagents. Statistical analysis was done on SPSS and two-tailed p-value <0.05 was considered significant.

Result

Postmenopausal women had significantly lower estradiol, plasma NO, and c-GMP levels as compared to premenopausal women (p < 0.05). Cholesterol, low-density lipoprotein (LDL) cholesterol and apolipoprotein B (apo-B) levels were higher and HDL levels were lower in postmenopausal as compared to premenopausal women (p < 0.05). Plasma NO showed a significant positive correlation with estradiol, HDL levels and negative correlation with apo-B levels.

Conclusion

Menopause tends to downregulate NO–c-GMP pathway resulting in endothelial dysfunction. The mechanism may be directly through estrogen receptors or indirectly through potentiation of dyslipidemia.  相似文献   
893.
Purpose: In the Alabama Black Belt, poverty is high, and the educational level is low. Studies have found increased tobacco use among individuals exposed to high levels of stress. Few studies have been conducted in this region to measure smoking status, its sociodemographic determinants, and how smoking status relates to stressful environmental conditions. Methods: A cross‐sectional questionnaire survey of 1,387 individuals. Findings: Approximately 25% of the respondents currently smoked cigarettes. Females were less likely to smoke compared to males (OR, 0.29; 95% CI, 0.23‐0.38). Blacks were less likely to smoke cigarettes compared to whites (OR, 0.64; 95% CI, 0.43‐0.95). Compared to individuals who were employed, participants who were unemployed or retired had increased odds of smoking (OR, 1.68; 95% CI, 1.15‐2.20). The odds of being a current smoker were increased in the presence of moderate level stress (OR, 2.06; 95% CI, 1.38‐3.07) or when there was a high level of stress (OR, 2.21; 95% CI, 1.47‐3.31). Smoking was associated with increased odds of having a moderate level (OR, 2.06; 95% CI, 1.38‐3.08) and a high level of stress (OR, 2.21; 95% CI, 1.47‐3.32). Females who reported moderate to high levels of stress had increased odds of being smokers compared to males. Interaction between gender and stress showed deviation from additivity. Conclusion: Our findings suggest a high rate of cigarette use in the area. Increased stress levels appear to predispose females more than males to cigarette smoking. The implications of this association may guide interventions targeted at reducing smoking and its complications.  相似文献   
894.
Emergency cholecystectomy for acute cholecystitis in critically ill patients with organ failure and sepsis carries a high risk of morbidity and mortality. Temporizing interventions such as laparoscopic cholecystostomy can help the patient to recover from the critical illness by deferring the definitive procedure to a later, safer period. We describe our experience of laparoscopic cholecystostomy performed in two critically ill patients. In the first case, a 56-year-old man with hypertension, diabetes, and ischemic heart disease, was admitted for evaluation of malena. During the course of his stay, he developed acute calculous cholecystitis, acute renal failure, and right pleural effusion. In the second case, a 68-year-old man presented with diabetes, hypertension, diabetic nephropathy, acute chronic renal failure, and acute calculous cholecystitis. Both patients failed to improve with conservative measures and underwent laparoscopic cholecystostomy under local anesthesia and sedation in view of severe comorbidities and sepsis. Both patients recovered from sepsis. Laparoscopic cholecystectomy was performed uneventfully after six and eight weeks, respectively, and both patients were doing well at one-year follow-up.  相似文献   
895.
In this report, we have investigated the relationship between androgen levels and prostate tumorigenesis in Nkx3.1; Pten mutant mice, a genetically engineered mouse model of human prostate cancer. By experimentally manipulating serum levels of testosterone in these mice for an extended period (i.e., 7 months), we have found that prolonged exposure of Nkx3.1; Pten mutant mice to androgen levels that are 10-fold lower than normal (the "Low-T" group) resulted in a marked acceleration of prostate tumorigenesis compared with those exposed to androgen levels within the reference range (the "Normal-T" group). We found that prostate tumors from the Low-T mutant mice share a similar gene expression profile as androgen-independent prostate tumors from these mutant mice, which includes the deregulated expression of several genes that are up-regulated in human hormone-refractory prostate cancer, such as Vav3 and Runx1. We propose that exposure to reduced androgens may promote prostate tumorigenesis by selecting for molecular events that promote more aggressive, hormone-refractory tumors.  相似文献   
896.
897.
898.
The U.S. College of American Pathologists (CAP) has conducted a focused study of the proficiency testing for von Willebrand disease (vWD) analysis from 2003 to 2005. This report summarizes the findings regarding the accuracy and precision of the various assays at different analyte levels, as well as the influence of the reference material used to construct the assay standard curve. The results show that testing of von Willebrand factor (vWF):antigen (vWF:Ag) and ristocetin cofactor activity (vWF:RCo) is reasonably accurate, with all-method mean values falling within 3.2 and 5.6%, respectively, of the International Society on Thrombosis and Haemostasis Secondary Coagulation Standard (lot 2) assigned values. vWF:Ag measurements are reasonably precise (all-method coefficients of variation [CVs] = 10.7 to 15.1%), even at lower levels of vWF. The highest precision was observed for immunoturbidometric assays (CVs, 6.3 to 9.7%). vWF:RCo measurements are less precise (all-method CVs, 23.3 to 30.9%). The reference materials used in the standard curves for immunoturbidometric vWF:Ag assays appear to have accurately assigned vWF values for the majority of commercial suppliers.  相似文献   
899.
Purpose:To evaluate the effectiveness of a modified therapeutic protocol used for vernal keratoconjunctivitis (VKC) based on severity as per Bonini grading system.Methods: This was a prospective observational clinical study conducted with 123 eyes of 63 patients. A meticulous clinical examination was performed, and data was documented in all the cases. Patients on known systemic atopy and antiallergic therapy were excluded from the study. Eyes with a clinical diagnosis of VKC were segregated based on Bonnini’s grading system. A treatment protocol was created depending on the grade of VKC. Therapeutic responses were documented at 3 weeks, 3 months, 6 months, 12 months, and 24 months. Grading of the eyes was performed in each visit.Results: The mean age of the patients was 8.85 years with a standard deviation of 4.48 years. Males were predominant, and 95.24% had bilateral manifestation. The palpebral component was the most common form of manifestation. Itching was the most common manifestation, followed by congestion, discharge, and papillae in a decreasing order. Also, 68% of patients were in grade 2, 14% in grade 3, 12% in grade 1, and the rest were in grade 4. Following the treatment protocol, 70% showed signs of significant improvement in grade by the end of 6 weeks, reaching 90% at the end of 6 months (P = 0.074) and 92% at the end of 12 months (P = 0.002). Also, 52.4% versus 77.8% of patients had no recurrence in the pre- versus posttreatment protocol and it was statistically significant (P = 0.001).Conclusion: Grading of VKC gives a clear evaluation of the severity and progression of the condition. Besides, significant improvement in the grades was observed with fewer incidences of recurrences following execution of the therapeutic protocol. Hence, it is essential to maintain a treatment protocol in our clinical practice to provide grade-based therapy and monitor accurate changes in the clinical condition.  相似文献   
900.
Though angiogenesis has been investigated in depth, vascular regression and rarefaction remain poorly understood. Regression of renal vasculature accompanies many pathological states such as diabetes, hypertension, atherosclerosis, and radiotherapy. Radiation decreases microvessel density in multiple organs, though the mechanism is not known. By using a whole animal (rat) model with a single dose of partial body irradiation to the kidney, changes in the volume of renal vasculature were recorded at two time points, 60 and 90 days after exposure. Next, a novel vascular and metabolic imaging (VMI) technique was used to computationally assess 3D vessel diameter, volume, branch depth, and density over multiple levels of branching down to 70 µm. Four groups of rats were studied, of which two groups received a single dose of 12.5 Gy X-rays. The kidneys were harvested after 60 or 90 days from one irradiated and one non-irradiated group at each time point. Measurements of the 3D vasculature showed that by day-90 post-radiation, when renal function is known to deteriorate, total vessel volume, vessel density, maximum branch depth, and the number of terminal points in the kidneys decreased by 55%, 57%, 28%, and 53%, respectively. Decreases in the same parameters were not statistically significant at 60 days post-irradiation. Smaller vessels with internal diameters of 70-450 µm as well as large vessels of diameter 451-850 µm, both decreased by 90 days post-radiation. Vascular regression in the lungs of the same strain of irradiated rats has been reported to occur before 60 days supporting the hypothesis that this process is regulated in an organ-specific manner and occurs by a concurrent decrease in luminal diameters of small as well as large blood vessels.  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