全文获取类型
收费全文 | 68019篇 |
免费 | 5981篇 |
国内免费 | 3387篇 |
专业分类
耳鼻咽喉 | 1207篇 |
儿科学 | 819篇 |
妇产科学 | 763篇 |
基础医学 | 9370篇 |
口腔科学 | 1225篇 |
临床医学 | 7605篇 |
内科学 | 11767篇 |
皮肤病学 | 1380篇 |
神经病学 | 4260篇 |
特种医学 | 3516篇 |
外国民族医学 | 24篇 |
外科学 | 7793篇 |
综合类 | 6491篇 |
现状与发展 | 13篇 |
一般理论 | 12篇 |
预防医学 | 3659篇 |
眼科学 | 1661篇 |
药学 | 6840篇 |
41篇 | |
中国医学 | 2706篇 |
肿瘤学 | 6235篇 |
出版年
2024年 | 185篇 |
2023年 | 955篇 |
2022年 | 2493篇 |
2021年 | 3504篇 |
2020年 | 2435篇 |
2019年 | 2371篇 |
2018年 | 2492篇 |
2017年 | 2186篇 |
2016年 | 2332篇 |
2015年 | 3379篇 |
2014年 | 3933篇 |
2013年 | 3891篇 |
2012年 | 5609篇 |
2011年 | 5799篇 |
2010年 | 3582篇 |
2009年 | 2894篇 |
2008年 | 3805篇 |
2007年 | 3625篇 |
2006年 | 3361篇 |
2005年 | 3147篇 |
2004年 | 2331篇 |
2003年 | 2089篇 |
2002年 | 1782篇 |
2001年 | 1240篇 |
2000年 | 1190篇 |
1999年 | 1217篇 |
1998年 | 683篇 |
1997年 | 660篇 |
1996年 | 497篇 |
1995年 | 455篇 |
1994年 | 407篇 |
1993年 | 236篇 |
1992年 | 401篇 |
1991年 | 313篇 |
1990年 | 299篇 |
1989年 | 273篇 |
1988年 | 229篇 |
1987年 | 206篇 |
1986年 | 180篇 |
1985年 | 129篇 |
1984年 | 96篇 |
1983年 | 78篇 |
1982年 | 31篇 |
1981年 | 47篇 |
1980年 | 27篇 |
1979年 | 47篇 |
1978年 | 26篇 |
1977年 | 26篇 |
1976年 | 35篇 |
1974年 | 33篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
This study aimed to determine mercury concentrations in tree rings and surface soils at distances of 4, 26 and 40 km from a fertilizer plant located in Yeosu City, Korea. Mercury concentrations in all tree rings were low prior to the establishment of the plant in 1977 and became elevated thereafter. The highest average mercury concentration in the tree rings was 11.96 ng g?1 at the Yeosu site located nearest to the plant, with the lowest average mercury concentration of 4.45 ng g?1 at the Suncheon site furthest away from the plant. In addition, the highest mercury content in the surface soil was 108.51 ng cm?3 at the Yeosu site, whereas the lowest mercury content in the surface soil was 31.47 ng cm?3 at the Suncheon site. The mercury levels decreased gradually with increasing distance from the plant. 相似文献
992.
Peili Huang Guojun Li Chunxia Chen Hui Wang Ying Han Shuhua Zhang Yang Xiao Man Zhang Na Liu Jinhua Chu Long Zhang Zhiwei Sun 《Experimental and toxicologic pathology》2012,64(3):197-203
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
993.
Jing Liu Zheng Han Guoli Chen Yuguo Li Jia Zhang Jiadi Xu Peter C.M. van Zijl Shuixing Zhang Guanshu Liu 《NMR in biomedicine》2018,31(8)
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
994.
995.
Hyo Hyeok Lee Dae Shick Ryu Sang Sig Jung Seung Mun Jung Soo Jung Choi Dae Hee Shin 《Korean journal of radiology》2011,12(3):390-394
Pericardial fat necrosis is an infrequent cause of acute chest pain and this can mimic acute myocardial infarction and acute pericarditis. We describe here a patient with the magnetic resonance imaging (MRI) findings of pericardial fat necrosis and this was correlated with the computed tomography (CT) findings. The MRI findings may be helpful for distinguishing pericardial fat necrosis from other causes of acute chest pain and from the fat-containing tumors in the cardiophrenic space of the anterior mediastinum. 相似文献
996.
997.
998.
In vivo confocal microscopic investigation of the cornea after autologous implantation of lenticules obtained through small incision lenticule extraction for treatment of hyperopia
下载免费PDF全文
![点击此处可从《Clinical & experimental optometry》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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.
Abnormal Connection of the Ductus Venosus to a Dilated Coronary Sinus Imaged by Prenatal Echocardiography: Case Report
下载免费PDF全文
![点击此处可从《Echocardiography (Mount Kisco, N.Y.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yuan Qian M.S. Han Bing M.S. Cai Ailu M.D. Sun Wei M.S. Wang Yu M.S. Wang Lei M.S. 《Echocardiography (Mount Kisco, N.Y.)》2016,33(1):154-156
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