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   11059篇
  免费   583篇
  国内免费   25篇
耳鼻咽喉   92篇
儿科学   320篇
妇产科学   297篇
基础医学   2059篇
口腔科学   213篇
临床医学   1036篇
内科学   1932篇
皮肤病学   172篇
神经病学   1150篇
特种医学   484篇
外科学   1357篇
综合类   91篇
一般理论   3篇
预防医学   966篇
眼科学   142篇
药学   703篇
中国医学   29篇
肿瘤学   621篇
  2022年   66篇
  2021年   148篇
  2020年   97篇
  2019年   131篇
  2018年   159篇
  2017年   128篇
  2016年   162篇
  2015年   214篇
  2014年   272篇
  2013年   390篇
  2012年   656篇
  2011年   693篇
  2010年   412篇
  2009年   373篇
  2008年   624篇
  2007年   662篇
  2006年   631篇
  2005年   660篇
  2004年   597篇
  2003年   538篇
  2002年   544篇
  2001年   125篇
  2000年   85篇
  1999年   114篇
  1998年   127篇
  1997年   99篇
  1996年   86篇
  1995年   91篇
  1994年   69篇
  1993年   66篇
  1992年   50篇
  1991年   67篇
  1990年   50篇
  1989年   47篇
  1985年   48篇
  1984年   53篇
  1982年   49篇
  1974年   48篇
  1933年   76篇
  1932年   67篇
  1931年   65篇
  1930年   70篇
  1929年   49篇
  1928年   57篇
  1927年   68篇
  1926年   61篇
  1925年   55篇
  1924年   61篇
  1923年   45篇
  1922年   46篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Liver-related death in human immunodeficiency virus (HIV)-infected individuals is about 10 times higher compared with the general population, and the prevalence of significant liver fibrosis in those with HIV approaches 15%. The present study aimed to assess risk factors for development of hepatic fibrosis in HIV patients receiving a modern combination anti-retroviral therapy (cART).This cross-sectional prospective study included 432 HIV patients, of which 68 (16%) patients were anti-hepatitis C virus (HCV) positive and 23 (5%) were HBsAg positive.Health trajectory including clinical characteristics and liver fibrosis stage assessed by transient elastography were collected at inclusion. Liver stiffness values >7.1 kPa were considered as significant fibrosis, while values >12.5 kPa were defined as severe fibrosis. Logistic regression and Cox regression uni- and multivariate analyses were performed to identify independent factors associated with liver fibrosis.Significant liver fibrosis was detected in 10% of HIV mono-infected, in 37% of HCV co-infected patients, and in 18% of hepatitis B virus co-infected patients. The presence of diabetes mellitus (odds ratio [OR] = 4.6) and FIB4 score (OR = 2.4) were independently associated with presence of significant fibrosis in the whole cohort. Similarly, diabetes mellitus (OR = 5.4), adiposity (OR = 4.6), and the FIB4 score (OR = 3.3) were independently associated with significant fibrosis in HIV mono-infected patients. Importantly, cumulative cART duration protected, whereas persistent HIV viral replication promoted the development of significant liver fibrosis along the duration of HIV infection.Our findings strongly indicate that besides known risk factors like metabolic disorders, HIV may also have a direct effect on fibrogenesis. Successful cART leading to complete suppression of HIV replication might protect from development of liver fibrosis.  相似文献   
3.
4.
To understand in situ behavior of osteocytes, we characterized a model of osteocytes in their native bone matrix and demonstrated real-time biologic activity of osteocytes while bending the bone matrix. Using 43 male Sprague-Dawley rats, dumbbell-shaped explants were harvested from stainless steel femoral implants after 6-12 weeks and incubated in culture medium or fixed. Sixteen specimens were used to determine bone volume density (BV/TV), volumetric bone mineral density (BMD) and histology for different implantation periods. Osteocyte viability was evaluated by L-lactate dehydrogenase (LDH) activity in 12 cultured explants. Confocal microscopy was used to assess tracer diffusion in three explants and changes in osteocyte pH of a mechanically loaded explant. From 6 to 12 weeks, explant BV/TV and volumetric BMD trended up 92.5% and 101%, respectively. They were significantly and highly correlated. Tissues were uniformly intramembranous and all bone cell types were present. Explants maintained LDH activity through culture day 8. Diffusion at 200 microM was limited to 1,209 Da. Explants appeared capable of reproducing complex bone biology. This model may be useful in understanding osteocyte mechanotransduction in the context of a physiologically relevant bone matrix.  相似文献   
5.
Previous observational research confirms abundant variation in primary care practice. While variation is sometimes viewed as problematic, its presence may also be highly informative in uncovering ways to enhance health care delivery when it represents unique adaptations to the values and needs of people within the practice and interactions with the local community and health care system. We describe a theoretical perspective for use in developing interventions to improve care that acknowledges the uniqueness of primary care practices and encourages flexibility in the form of intervention implementation, while maintaining fidelity to its essential functions.  相似文献   
6.
Small intestinal transplantation represents a potentially therapeutic procedure for individuals with short gut syndrome. The purpose of this study was to develop a model for small intestinal transplantation in primates that is: technically feasible without microsurgery; consistent in the prevention of allograft rejection; functional in terms of nutrient absorption; and compatible with harvest for multiple organ procurement. First, autotransplantations on four rhesus monkeys were performed in order to study a variety of harvesting techniques and vascular anastomoses. Then, a study was performed with 14 heterotopic allotransplants in 4 baboons and 10 rhesus primates. The successful donor model consisted of division of the pancreas, harvesting the small bowel with a superior mesenteric artery and portal vein pedicle. The allograft vascular pedicle was anastomosed to the recipient's common iliac vessels in end-to-side fashion. The graft was transplanted as an out-of-continuity loop, both ends being exteriorized as stomas providing access for absorption studies and biopsy. Three immunosuppressive regimens were tested: (1) cyclosporine A (CyA) 20 mg/kg/d, solumedrol (SML) 2 mg/kg/d, and graft irradiation (150 rad) (n = 4); (2) CyA 20 mg/kg/d and SML 2 mg/kg/d (n = 3); and (3) CyA 40 mg/kg/d, SML 2 mg/kg/d, and azathioprine 5 mg/kg/d (n = 3). There were 4 deaths due to technical error in the first 24 hours. Weekly graft biopsy, serum CyA levels, complete blood count, and automated 24-channel serum analysis were performed. Grafts surviving greater than 14 days underwent absorption study via luminal perfusion with sucrose, maltose, dextrose, Pregestimil, xylose, and cyclosporine.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
7.
BACKGROUND: Results from studies in serotonin-1A (5-HT1A) knockout mice and previous positron emission tomography (PET) studies in humans imply a role for 5-HT1A receptors in normal state anxiety as well as in certain anxiety disorders. The objective of this study was to investigate 5-HT1A receptor binding potential (BP) in social anxiety disorder (SAD). METHODS: Using PET and [carbonyl-11C]WAY-100635, we compared a homogeneous group of 12 unmedicated, male SAD patients with 18 healthy control subjects (HC). A multivariate ANOVA with all regional BP values as dependent variables, age and four radiochemical variables as covariates was performed. RESULTS: We found a significantly lower 5-HT1A BP in several limbic and paralimbic areas but not in the hippocampus (p = .234) of SAD patients. The difference in 5-HT1A binding was most significant in the amygdala (-21.4%; p = .003). There was also a more than 20% lower 5-HT(1A) BP of SAD patients in the anterior cingulate cortex (p = .004), insula (p = .003), and dorsal raphe nuclei (p = .030). CONCLUSIONS: The lower 5-HT1A binding in the amygdala and mesiofrontal areas of SAD patients is consistent with 1) preclinical findings of elevated anxiety in 5-HT1A knockout mice, 2) a previous PET study in healthy volunteers showing an inverse correlation between 5-HT1A BP and state anxiety, and 3) another human PET study in patients with panic disorder showing reduced 5-HT1A binding, thus corroborating the potential validity of 5-HT1A receptors as targets in the treatment of human anxiety disorders.  相似文献   
8.
9.
PURPOSE: To investigate whether balloon angioplasty of the superficial femoral artery (SFA) increases serum levels of C5a and whether C5a predicts risk of restenosis. METHODS: C5a antigen was measured at baseline and 8 hours after intervention in 131 consecutive patients (76 women; median age 72 years) with intermittent claudication who underwent successful primary SFA balloon angioplasty. Patients were followed for a median 10 months [interquartile range (IQR) 6 to 14] for the occurrence of >50% restenosis by duplex ultrasound. RESULTS: Median C5a levels increased significantly from 39.7 ng/mL (IQR 27.8 to 55.0) at baseline to 53.8 ng/mL (IQR 35.6 to 85.1, p<0.001) 8 hours post intervention. During the follow-up period, 70 (53%) patients developed restenosis. Increasing levels of C5a (quartiles) at baseline were significantly associated with an increased risk for restenosis (p=0.0092). Adjusted hazard ratios (95% confidence intervals) for restenosis with increasing quartiles of baseline serum C5a levels were 1.24 (0.60 to 2.58), 1.93 (0.95 to 3.93), and 2.08 (1.02 to 4.21), respectively, compared to the lowest quartile. This effect was independent of nonspecific inflammation as reflected by plasma levels of C-reactive protein. CONCLUSION: Inflammatory mechanisms play a major role in the development of restenosis after angioplasty. The complement component C5a exerts strong chemotactic and proinflammatory effects. Enhanced complement activation prior to PTA, as measured by higher levels of C5a, was significantly associated with restenosis after SFA balloon angioplasty. Pathways of complement inhibition thus may be worth investigating with respect to improving patency rates.  相似文献   
10.
Introduction Iniencephaly, a neural tube defect involving occiput and inion and combined with rachischisis of the cervical, thoracic spine, and retroflexion position of the head is a very rare congenital abnormality of the fetus–newborn with a 0.1–10 of 10,000 prevalence. This abnormality’s prognosis is thought to be dismal. This abnormality can be associated with other abnormalities such as anencephaly, encephalocele, hydrocephalus, cyclopia, absence of the mandible, cleft lip and palate, cardiovascular disorders, diaphragmatic hernia, renal abnormalities, overgrowth of the arms compared to the legs, and club food and gastrointestinal atresia. Discussion Most of the patients are dead born, and the others die in a few hours. There are only six previously documented long-term survivors. In our case, our patient with iniencephalic signs and findings is still living. She is 2 years old now. We think that this patient presents a mild form of iniencephaly.  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