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   3788篇
  免费   239篇
  国内免费   18篇
耳鼻咽喉   104篇
儿科学   158篇
妇产科学   92篇
基础医学   323篇
口腔科学   299篇
临床医学   256篇
内科学   781篇
皮肤病学   56篇
神经病学   231篇
特种医学   114篇
外科学   911篇
综合类   75篇
一般理论   1篇
预防医学   166篇
眼科学   80篇
药学   228篇
中国医学   24篇
肿瘤学   146篇
  2023年   40篇
  2022年   51篇
  2021年   135篇
  2020年   105篇
  2019年   142篇
  2018年   178篇
  2017年   115篇
  2016年   162篇
  2015年   164篇
  2014年   203篇
  2013年   198篇
  2012年   273篇
  2011年   299篇
  2010年   151篇
  2009年   134篇
  2008年   242篇
  2007年   233篇
  2006年   212篇
  2005年   205篇
  2004年   155篇
  2003年   117篇
  2002年   87篇
  2001年   69篇
  2000年   51篇
  1999年   50篇
  1998年   15篇
  1997年   8篇
  1996年   12篇
  1995年   11篇
  1994年   7篇
  1993年   10篇
  1992年   20篇
  1991年   26篇
  1990年   13篇
  1989年   6篇
  1988年   13篇
  1987年   13篇
  1986年   12篇
  1985年   14篇
  1984年   9篇
  1983年   9篇
  1982年   13篇
  1981年   6篇
  1980年   5篇
  1979年   6篇
  1978年   6篇
  1977年   6篇
  1974年   4篇
  1973年   4篇
  1971年   4篇
排序方式: 共有4045条查询结果,搜索用时 31 毫秒
1.
In this prospective study, we investigated the impact of SARS-CoV-2 infection on semen parameters in a cohort of men who had recently recovered from COVID-19. A total of 24 men who had recently recovered from mild COVID-19 were included in the study. Their semen parameters were normal before COVID-19 according to the World Health Organization 2010 reference values. Semen samples were collected from these participants in the recovery phases of COVID-19. To determine the effect of SARS-CoV-2 infection on semen parameters, the patients' pre-COVID-19 and post-COVID-19 semen analyses were compared. The mean age of the participants was 34.7 ± 6.4 years. The median interval between the positive nasopharyngeal swab test and obtaining semen samples was 111.5 (158) days. There was no significant difference in semen parameters before and after COVID-19 in terms of semen volume (p = .56), sperm concentration (p = .06), and progressive motility (p = .14). Total motility (p = .01) and total motile sperm count (p = .02) decreased significantly after SARS-CoV-2 infection compared to the pre-infection values. This study demonstrated that sperm motility and total motile sperm count were the semen parameters which showed a significant reduction in cases with a history of mild COVID-19.  相似文献   
2.
3.
4.
Today, cardiovascular diseases remain a leading cause of morbidity and mortality worldwide. Endothelial to mesenchymal transition (EndMT) does not only play a major role in the course of development but also contributes to several cardiovascular diseases in adulthood. EndMT is characterized by down-regulation of the endothelial proteins and highly up-regulated fibrotic specific genes and extracellular matrix-forming proteins. EndMT is also a transforming growth factor-β-driven (TGF-β) process in which endothelial cells lose their endothelial characteristics and acquire a mesenchymal phenotype with expression of α-smooth muscle actin (α-SMA), fibroblast-specific protein 1, etc. EndMT is a vital process during cardiac development, thus disrupted EndMT gives rise to the congenital heart diseases, namely septal defects and valve abnormalities. In this review, we have discussed the main signaling pathways and mechanisms participating in the process of EndMT such as TGF-β and Bone morphogenetic protein (BMP), Wnt#, and Notch signaling pathway and also studied the role of EndMT in physiological cardiovascular development and pathological conditions including myocardial infarction, pulmonary arterial hypertension, congenital heart defects, cardiac fibrosis, and atherosclerosis. As a perspective view, having a clear understanding of involving cellular and molecular mechanisms in EndMT and conducting Randomized controlled trials (RCTs) with a large number of samples for involving pharmacological agents may guide us into novel therapeutic approaches of congenital disorders and heart diseases.  相似文献   
5.
p53 is a key regulator of apoptosis. p53 upregulated modulator of apoptosis (PUMA) is a critical mediator of p53‐dependent and independent apoptosis. The objective of this study was to evaluate the relationship of p53 and PUMA to the prognosis of MDS. Bone marrow biopsies of MDS patients at the time of diagnosis (n = 76) and at the time of transformation (n = 19) were included in the study group. The expression of p53 and PUMA was evaluated using immunohistochemistry. When compared to the control group, both p53 (p < 0.001) and PUMA (p = 0.012) expression levels were significantly higher in MDS group. In MDS group, there was a moderate positive correlation between p53 and PUMA expressions. PUMA expression was not correlated with event free and overall survival. However, overall survival was significantly lower in cases with p53 expression in more than 50% of the cells. There was an increase in PUMA expression in cases that showed transformation as compared to the initial diagnostic bone marrows but was not statistically significant. The correlation that existed between p53 and PUMA was lost in transformed cases. Our results showed that PUMA and p53 expressions are increased in MDS marrows compared to normal marrows. PUMA expression increases further during transformation while the expression of p53 is not significantly altered which suggests that PUMA alterations might be a late event during the evolution of MDS.  相似文献   
6.
7.
Acute limb ischemia (ALI) is a limb-threatening and life-threatening disease process. Mural aortic thrombosis (MAT) is a rare cause of ALI. While there is limited evidence on the use of bedside ultrasound for the detection of ALI or MAT, duplex ultrasound remains the standard in the diagnosis and ultimate medical decision-making in patients with acute and chronic limb ischemia. Point-of-care ultrasound may be used in the evaluation of patients with signs and symptoms of this disease entity. This is a case of a 79-year-old female with a complicated medical history, who presented with a pulseless right leg and abdominal tenderness. The patient quickly decompensated requiring intubation for airway protection. A post-intubation arterial blood gas (ABG) was unsuccessfully attempted in the right femoral artery, prompting an ultrasound-guided ABG. On B-mode ultrasound evaluation, echogenic material was visualized in the right common femoral artery without evidence of Doppler flow signal. Additionally, a partially obstructing echogenic material was also noted at the femoro-saphenous vein junction with only partial compressibility by compression sonography. A computed tomography angiography of the aorta was performed indicating extensive infrarenal aortic thrombosis. The patient expired despite the relatively prompt diagnosis, highlighting the importance of early identification of acute arterial occlusion.  相似文献   
8.
9.
In this study, the influence of the glass-forming ability (GFA) of a drug on its physical stability in a supersaturated solid dispersion was investigated. Nine drugs were classified according to their GFA using their respective critical cooling rate. Their respective solubility in poly(vinylpyrrolidone-co-vinyl acetate) 6:4 (PVPVA64) was predicted using the melting point depression method based on the Flory-Huggins lattice theory. Supersaturated amorphous solid dispersions at a level of 25% w/w drug above saturation solubility in the polymer were prepared by film-casting, and their respective physical stability at temperatures of 10°C or 20°C above or below their respective Tg (dry conditions) was monitored by the use of polarized light microscopy. This study showed that drugs with good GFA (class 3) on average have higher physical stability in supersaturated amorphous solid dispersion compared to drug with modest GFA (class 2), which in turn have higher physical stability in supersaturated amorphous solid dispersion than drugs with poor GFA (class 1). These results indicate that the GFA of a drug and its physical stability in a supersaturated amorphous solid dispersion stored at a temperature above or below its Tg are correlated.  相似文献   
10.
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