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   54140篇
  免费   5062篇
  国内免费   3087篇
耳鼻咽喉   849篇
儿科学   676篇
妇产科学   616篇
基础医学   7356篇
口腔科学   1059篇
临床医学   6461篇
内科学   8888篇
皮肤病学   799篇
神经病学   3241篇
特种医学   2710篇
外国民族医学   21篇
外科学   5950篇
综合类   6239篇
现状与发展   14篇
一般理论   5篇
预防医学   3053篇
眼科学   1287篇
药学   5560篇
  39篇
中国医学   2456篇
肿瘤学   5010篇
  2024年   113篇
  2023年   749篇
  2022年   1191篇
  2021年   2996篇
  2020年   2174篇
  2019年   2013篇
  2018年   2048篇
  2017年   1838篇
  2016年   1833篇
  2015年   2667篇
  2014年   3084篇
  2013年   3002篇
  2012年   4294篇
  2011年   4554篇
  2010年   2810篇
  2009年   2239篇
  2008年   2976篇
  2007年   2898篇
  2006年   2714篇
  2005年   2551篇
  2004年   1881篇
  2003年   1720篇
  2002年   1434篇
  2001年   1138篇
  2000年   1125篇
  1999年   1147篇
  1998年   621篇
  1997年   604篇
  1996年   474篇
  1995年   427篇
  1994年   382篇
  1993年   221篇
  1992年   372篇
  1991年   287篇
  1990年   277篇
  1989年   246篇
  1988年   221篇
  1987年   189篇
  1986年   159篇
  1985年   121篇
  1984年   81篇
  1983年   67篇
  1982年   26篇
  1981年   35篇
  1980年   22篇
  1979年   37篇
  1978年   21篇
  1977年   22篇
  1976年   32篇
  1974年   25篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Li  Xiao-ming  Yang  Qi  Li  Xu-bo  Cheng  Qiang  Zhang  Kun  Han  Jing  Zhao  Jian-ning  Liu  Gang  Zhao  Ming-gao 《Metabolic brain disease》2017,32(1):259-265
Metabolic Brain Disease - Isopsoralen is a type of furocoumarin that exhibits estrogen-like activities. The aim of this study was to determine the estrogen-like neuroprotection of isopsoralen in an...  相似文献   
992.
The chitosan-caffeic acid (CCA) conjugate shows a hepatoprotective effect against oxidative stress-induced hepatic damage in cultured hepatocytes. The objective of this study is the verification of the hepatoprotective effect of the CCA in vivo against ethanol-induced liver injury in mice. The administration of ethanol resulted in the increase of the serum-aminotransferase activities (AST and ALT), triglycerides, total cholesterol, and lipid peroxidation. The CCA co-administration, however, significantly (p < 0.05) ameliorated these serum biomarkers. The antioxidant-enzyme activities in the liver tissue, including those of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), were significantly decreased by a chronic ethanol administration, whereas the hepatic lipid-peroxidation level was increased. Moreover, the chronic ethanol administration elevated the gene expression of pro-inflammatory cytokines such as tumor-necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in the liver tissue. The CCA co-administration, however, significantly (p < 0.05) increased the activities of the SOD, CAT, and GPx and caused the down-regulation of the TNF-α- and IL-6-gene expressions in the liver tissue. An histopathologic evaluation also supported the hepatoprotective effect of the CCA against ethanol-induced hepatotoxicity in the mice.  相似文献   
993.
Studies confirming a possible relationship of polymyositis within thyroid dysfunction, either hypothyroidism or hyperthyroidism, are hardly available. To define the association, identify clinical, laboratory, electromyographic, and pathologic features in polymyositis (PM) patients with hypothyroidism or hyperthyroidism, we conducted a MEDLINE and Chinese biomedicine database search to identify relevant literature published in the past 25 years. Seventeen cases were included. All patients were female (10 hypothyroidism patients, seven hyperthyroidism patients). The mean (SD) age of PM, hypothyroidism, and hyperthyroidism at diagnosis was 54.8 (16.7), 55.5 (16.5), and 32.7 years (10.2), respectively. PM diagnosis can precede or parallel hypothyroidism while PM may occur following the diagnosis of hyperthyroidism. The most common comorbidities were malignant tumors in these disorders, including thymoma, colon cancer, and thyroid cancer. Muscle weakness was described in 100% of patients. Other common manifestations included muscles’ atrophy and pain, deep tendon reflexes, polyarthralgia, and dysphagia. Most patients had markedly elevated creatine kinase and the presence of anti-Sjogren’s syndrome A (SSA) antibodies was also found in two cases. Malignancy associated with PM may more frequently occur in hypothyroidism than in hyperthyroidism. The abnormalities on electromyography and biopsy did not differ from those findings of PM. Therapy consisting of corticosteroids, thyroid hormone, or anti-thyroid drugs was administrated; however, poor prognosis seemed to be associated with malignant tumors as well as older age and the presence of anti-SSA antibodies. It is reasonable to suggest that those patients should be routinely evaluated for thyroid function, especially in older female and patients suffering from cancers.  相似文献   
994.
Toxicity due to overexposure to manganese (Mn) is becoming increasingly prevalent. Mn-induced neurodegenerative toxicity has been demonstrated, but little is known concerning the adverse effects of the element on the liver. Under physiological conditions, manganese primarily exists as divalent manganese (Mn2+) and trivalent manganese (Mn3+). The present study was designed to evaluate and compare the effects of Mn2+ and Mn3+ on oxidative hepatic damage, membrane fluidity and histopathological changes in rats. Rats exposed to Mn2+ or Mn3+ (2.0 mg Mn/kg body weight) showed significant inhibition of superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity, as well as decreased levels of glutathione (GSH) and increased levels of malondialdehyde (MDA) in liver tissues. We also showed a significant inhibition of SOD activity and increased MDA levels in hepatocyte nuclei. We also observed reduced Na+,K+-ATPase activity, increased MDA levels and decreased plasma membrane fluidity, which was accompanied by an increase of fluorescence anisotropy (r) values, in hepatic plasma membranes. In addition, Mn2+ and Mn3+ both caused histopathological changes, such as mononuclear cell infiltration, congestion, enlargement of the veins and sinusoids, hepatocellular damage, necrotic changes, mitochondrial hyperplasia, swelling and vacuolization, as determined by light and electron microscopy. Taken together, these data suggest that both Mn2+ and Mn3+ inhibit the normal physiological functioning of the liver. Under the experimental conditions used, the adverse effects of Mn2+ were more severe than those of Mn3+.  相似文献   
995.
Sepsis‐induced acute kidney injury (SAKI) is a major complication of kidney disease associated with increased mortality and faster progression. Therefore, the development of imaging biomarkers to detect septic AKI is of great clinical interest. In this study, we aimed to characterize the endogenous chemical exchange saturation transfer (CEST) MRI contrast in the lipopolysaccharide (LPS)‐induced SAKI mouse model and to investigate the use of CEST MRI for detecting such injury. We used a SAKI mouse model that was generated by i.p. injection of 10 mg/kg LPS. The resulting kidney injury was confirmed by the elevation of serum creatinine and histology. MRI assessments were performed 24 h after LPS injection, including CEST MRI at different B1 strengths (1, 1.8 and 3 μT), T1 mapping, T2 mapping and conventional magnetization transfer contrast (MTC) MRI. The CEST MRI results were analyzed using Z‐spectra, in which the normalized water signal saturation (Ssat/S0) is measured as a function of saturation frequency. Substantial decreases in CEST contrast were observed at both 3.5 and ? 3.5 ppm frequency offset from water at all B1 powers, with the most significant difference obtained at a B1 of 1.8 μT. The average Ssat/S0 differences between injured and normal kidneys were 0.07 (0.55 ± 0.04 versus 0.62 ± 0.04, P = 0.0028) and 0.07 (0.50 ± 0.04 versus 0.57 ± 0.03, P = 0.0008) for 3.5 and ? 3.5 ppm, respectively. In contrast, the T1 and T2 relaxation times and MTC contrast in the injured kidneys did not show a significant change compared with the normal control. Our results showed that CEST MRI is more sensitive to the pathological changes in injured kidneys than the changes in T1, T2 and MTC effect, indicating its potential clinical utility for molecular imaging of renal diseases.  相似文献   
996.
997.
998.
999.
For persons living with HIV, health-related quality of life (HRQOL) may be threatened by physical and mental conditions but may be protected by positive psychological traits. We performed an exploratory look at the risk and protective factors for HRQOL in older adults living with HIV. Cross-sectional analyses of baseline data from the Rush Center of Excellence on Disparities in HIV and Aging (CEDHA), a community-based cohort of persons ages ≥50 living with HIV (n?=?176) were performed. Analyses examined the relationship between risk/protective factors and two outcomes (i.e., self-reported health status [SRHS] and the healthy days index [HDI]). Having good/excellent health was associated with being a non-smoker (p?=?0.002), greater purpose in life (p?=?0.006), higher education (p?=?0.007), fewer depressive symptoms (p?=?0.004), fewer disabilities (p?=?0.000), and less loneliness (p?=?0.002) in bivariate analyses. Males (p?=?0.03) and African Americans/Blacks (p?=?0.03) reported higher HDI. Fewer depressive symptoms (p?=?0.000), disabilities (p?=?0.002), adverse life events (p?=?0.0103), and loneliness (p?=?0.000) were associated with higher HDI in bivariate analyses. In a logistic regression model, greater purpose in life, fewer disabilities, and being a non-smoker were associated with better SRHS after adjusting for covariates. For African Americans/Blacks, having fewer depressive symptoms and disabilities were associated with higher HDI after adjusting for covariates. Disabilities, depression, smoking status, race/ethnicity, and purpose in life were significantly associated with HRQOL. Findings support the need for research to examine the influence of cultural interpretations of life quality and focus on promoting physical function, smoking cessation, and psychological wellness in persons aging with HIV.  相似文献   
1000.
We describe a case of a fetus with an ectopic connection of the ductus venosus to a dilated coronary sinus that was diagnosed at ShengJing Hospital of China Medical University. A dilated coronary sinus was initially detected with prenatal echocardiography. Neither a persistent left superior vena cava nor an anomalous pulmonary venous connection was present. After comprehensive examination, we discovered that the ductus venosus had an abnormal course draining into the coronary sinus. The postnatal outcome of this fetus was good. Once a dilated coronary sinus is confirmed, further ultrasound evaluation should be performed to search for a potential cause.  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