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   4048篇
  免费   239篇
  国内免费   11篇
耳鼻咽喉   33篇
儿科学   142篇
妇产科学   232篇
基础医学   445篇
口腔科学   77篇
临床医学   286篇
内科学   927篇
皮肤病学   76篇
神经病学   156篇
特种医学   118篇
外科学   533篇
综合类   118篇
一般理论   4篇
预防医学   151篇
眼科学   385篇
药学   347篇
中国医学   14篇
肿瘤学   254篇
  2024年   4篇
  2023年   43篇
  2022年   117篇
  2021年   203篇
  2020年   118篇
  2019年   131篇
  2018年   169篇
  2017年   92篇
  2016年   146篇
  2015年   142篇
  2014年   195篇
  2013年   221篇
  2012年   389篇
  2011年   383篇
  2010年   178篇
  2009年   119篇
  2008年   220篇
  2007年   217篇
  2006年   202篇
  2005年   180篇
  2004年   154篇
  2003年   133篇
  2002年   90篇
  2001年   53篇
  2000年   66篇
  1999年   46篇
  1998年   22篇
  1997年   21篇
  1996年   17篇
  1995年   14篇
  1994年   9篇
  1993年   19篇
  1992年   21篇
  1991年   18篇
  1990年   18篇
  1989年   24篇
  1988年   19篇
  1987年   9篇
  1986年   17篇
  1985年   8篇
  1984年   10篇
  1983年   4篇
  1981年   5篇
  1979年   4篇
  1978年   3篇
  1977年   5篇
  1970年   4篇
  1969年   4篇
  1968年   2篇
  1967年   3篇
排序方式: 共有4298条查询结果,搜索用时 15 毫秒
201.
Background: Tobacco is one of the leading causes of preventable deaths. It is both a major social and health problem. According to National Sample Survey Organization of Government of India about 20 million children of ages 10-14 are estimated to be tobacco-addicted. There are grave consequences of tobacco both socially and also on health thus it is of utmost importance to understand the factors leading to its use and to plan strategies to reduce its intake. However, the health implications of this social issue in a rural context have not been explored. Aims and Objective: this study makes an attempt to explore the health and social implications of tobacco usage by the children below the age of 14 years in hamlet. Materials and Methods:  The present study employed a qualitative study design. Data was collected using focus group discussion and in-depth interview of key informants. Thematic analysis for exploring the explicit and implicit meanings within the data was done. The themes which emerged were knowledge about tobacco and the various products available, children and parents’ tobacco use and habits, the health and social implication of tobacco use, reasons for tobacco use by the children. Results: It was found tobacco use by the children was very common in the community. Parent, peer pressure, sibling pressure were found to be playing important role in the initiation of tobacco habit by the child. Further illiteracy and lack of awareness was also lead to tobacco use among children. Conclusion: The study identifies education and awareness of parents about the ill-effects of tobacco play an important role as parents act as role model for their children, thus equal stress should be laid in improving the parental habits. Even raising the prices of tobacco products can help in controlling this habit.  相似文献   
202.
Aim: To evaluate and compare salivary and serum levels of Alkaline Phosphates and Lactate Dehydrogenase in patients without the habit of tobacco, in patients with the habit of tobacco, in patients with benign oral lesions and in patients with oral premalignant lesions and oral malignant lesions. Material and Methodology: This study was comprised of 500 subjects, Group I: 100 healthy individuals without the habit of tobacco usage formed the control group. Group II: 100 patients with the habit of tobacco/ smoking consumption without any oral lesion. Group III: 100 patients with benign oral lesions. Group IV: 100 patients having the history of tobacco consumption and having apparent precancerous lesions like leukoplakia, erythroplakia. Group V:100  patients having frank oral cancer. The grade of dysplasia in these patients was statically correlated with the levels of serum and salivary ALP and LDH. Results: This study revealed that there was high expression of both serum and salivary ALP and LDH  in group IV and Group V as compared with the other groups and mean difference showed a statistically significant p value of less than 0.01. This study revealed that the in group V, the highest level of serum and salivary ALP was found in those patients who were reported with poorly differentiated oral cancer. Conclusion: Both Alkaline phosphates and Lactate dehydrogenase could be considered a sensitive markers for the detection of dysplasia with already existing precancancerous and cancerous lesions.  相似文献   
203.
Primary pancreatic lymphoma is a rare disease. It comprises less than 0.5 % of pancreatic neoplasm and 0.1% of malignant lymphoma. It should be differentiated from pancreatic adenocarcinoma because management differs. At computed tomography, 2 types of morphology of primary pancreatic lymphoma have been described- a localized well-circumscribed tumoral form and another diffuse enlargement infiltrating or replacing most of the pancreatic gland. Here, we are presenting computed tomography (CT) imaging features of a case of primary pancreatic lymphoma in a 27 year old female who presented with a complaint of abdominal pain radiating to the back for 3 months and yellowish discoloration of sclera and skin for the last 15 days. In contrast-enhanced computed tomography an exophytic homogenously hypoenhancing mass arising from head and neck region of pancreas was seen. Involvement of common bile duct (CBD) and duodenum was there. The main pancreatic duct was not dilated. Common hepatic artery was encased by mass without arterial luminal narrowing or distortion. Diagnosis of primary pancreatic lymphoma was suggested on basis of imaging findings and further confirmed with fine-needle aspiration cytology.  相似文献   
204.
The SARS-CoV-2 pandemic has had a disastrous impact on global health. Although some vaccine candidates have been effective in combating SARS-CoV-2, logistical, economical, and sociological aspects still limit vaccine access globally. Recently, we reported on two room-temperature stable AAV-based COVID-19 vaccines that induced potent and protective immunogenicity following a single injection in murine and primate models. Obesity and old age are associated with increased mortality in COVID-19, as well as reduced immunogenicity and efficacy of vaccines. Here, we investigated the effectiveness of the AAVCOVID vaccine candidates in murine models of obesity and aging. Results demonstrate that obesity did not significantly alter the immunogenicity of either vaccine candidate. In aged mice, vaccine immunogenicity was impaired. These results suggest that AAV-based vaccines may have limitations in older populations and may be equally applicable in obese and non-obese populations.  相似文献   
205.

Background

Toxic liver injury from drugs including paracetamol is the main cause of acute liver failure in developed countries. The mechanisms that drive irreversible liver failure are poorly understood; platelets could have an important role in this process given their roles beyond haemostasis, including liver regeneration. Ligation of the platelet receptor CLEC-2 with its cognate ligand podoplanin (PDPN) powerfully activates platelets; we sought to investigate the role of CLEC-2 in the pathogenesis of acute liver failure.

Methods

Paracetamol or carbon tetrachloride (CCl4) were used to induce acute liver damage in mice. The role of CLEC-2-mediated platelet activation was investigated in mice with conditional deletions for either the platelet CLEC-2 receptor (PF4creCLEC1bfl/fl) or PDPN (Vav1-iCre+PDPNfl/fl), or with specific function blocking antibodies. Liver necrosis, and the subsequent inflammatory response, was gauged by assessment of hepatic leucocyte infiltration and measurement of liver histological and serum markers.

Findings

Initial liver injury after CCl4 and paracetamol administration was similar in both wild-type (WT) and CLEC-2-deficient mice. Abrogating CLEC-2-driven platelet activation accelerated liver healing from both toxic insults: mean serum alanine aminotransferase [ALT] after paracetamol administration was 1264 IU/L (SE 296·5) in WT mice versus 52·00 (5·00) in CLEC-2-deficient mice (n=5–8, p=0·0078); and after CCl4 4451 (886·3) versus 367 (99·35) (n=4–8, p=0·0015). Targeting this pathway therapeutically with a specific PDPN function blocking antibody in WT mice also enhanced liver healing: after CCl4 administration mean ALT in control antibody treated mice was 5482 (SE 785·4) versus 598·8 (102·4) in anti-PDPN antibody treated mice (n=6, p=0·0001), and after paracetamol 2850 (1128) versus 194·5 (61·26) (p=0·0176). In-vitro experiments showed that CLEC-2-deficient platelets interacted with Kupffer cells to enhance production of tumour necrosis factor α (TNFα) and increase accumulation of hepatic neutrophils. Healing was prevented by either blocking TNFα or depleting neutrophils in mice. Upregulation of PDPN on Kupffer cells in human acute liver failure suggests that this pathway is also activated in human beings.

Interpretation

Platelets are involved in determining the outcome of the sterile inflammatory response to toxic liver injury. Platelet activation via CLEC-2 in the context of an acute liver injury inhibits TNFα-driven reparative inflammation mediated by neutrophils. The fact that blocking CLEC-2-mediated platelet activation enhances neutrophil-driven liver repair without causing bleeding, suggests that this could be a completely novel treatment for human acute liver failure.

Funding

Wellcome Trust.  相似文献   
206.

Introduction

The present review is based on the study of various classifications of pneumatization of temporal bone and their comparison. The air cells are classified based on their location in the temporal bone in a radiograph or based on their interpretation by a radiologist or otolaryngologist with the help of different reference structures.

Methods

The analysis of pneumatization in temporal bone is done by reviewing research articles related to pneumatization of temporal bone in pig, sheep, macaque and humans published in Pubmed, Sciencedirect, Scopus, and Medline, Indexed journals.

Results and discussion

According to classical classification the temporal bone is divided into five regions viz., middle ear, squamomastoid(mastoid), perilabyrinthine, petrous apex and accessory. The cells are named accordingly and they are further classified into various grades by the degree of pneumatization and density of cells present in the respective regionsMost recent work which has been cited in various articles, is done by Han et al. [19] In this pneumatization is classified based on the visualization of various reference structures such as, sigmoid sinus, labyrinth, and internal carotid artery. The lack of consensus among surgeons and otolaryngologists regarding the classification of the pneumatization of temporal bone may be a cause of failure in a few otologic surgeries such as 10 mastoidectomies etc and postoperative care of skull base surgeries.  相似文献   
207.
Recent advances in understanding CD4+ T‐cell differentiation suggest that previous models of a few distinct, stable effector phenotypes were too simplistic. Although several well‐characterized phenotypes are still recognized, some states display plasticity, and intermediate phenotypes exist. As a framework for reexamining these concepts, we use Waddington's landscape paradigm, augmented with explicit consideration of stochastic variations. Our animation program “LAVA” visualizes T‐cell differentiation as cells moving across a landscape of hills and valleys, leading to attractor basins representing stable or semistable differentiation states. The model illustrates several principles, including: (i) cell populations may behave more predictably than individual cells; (ii) analogous to reticulate evolution, differentiation may proceed through a network of interconnected states, rather than a single well‐defined pathway; (iii) relatively minor changes in the barriers between attractor basins can change the stability or plasticity of a population; (iv) intrapopulation variability of gene expression may be an important regulator of differentiation, rather than inconsequential noise; (v) the behavior of some populations may be defined mainly by the behavior of outlier cells. While not a quantitative representation of actual differentiation, our model is intended to provoke discussion of T‐cell differentiation pathways, particularly highlighting a probabilistic view of transitions between states.  相似文献   
208.
209.
Reports on metastatic differentiated carcinoma in endemic goiter regions are scarce. The aim of this study was to look into the clinicopathological profile and outcome of patients with metastatic differentiated thyroid carcinoma (DTC) of endemic origin. This was a retrospective study of 28 cases of metastatic DTC out of a total of 140 DTC patients managed between 1990 and June 1999. Demographic data, clinicopathological profile, operative and radioiodine ablation therapy details, and follow-up findings were noted. The overall incidence of distant metastases in our series was 20%. Mean age was 48.5 +/- 12.8 years (32.1%patients were < 45 years). Most metastases were detected synchronously (85.7%) and were multiple, with the skeletal system being the commonly affected site. Out of 22 cases having skeletal metastases, 6 patients were young (< 45 years). Though most patients with skeletal metastases had follicular carcinoma (FTC), 4 cases had papillary thyroid cancer (PTC). Near total or total thyroidectomy was done in 26 cases. Sixteen patients required regional lymph node dissection. Resection of metastases was performed in 9 cases.Histopathological diagnosis was PTC, FTC, and poorly differentiated carcinoma in 32.1%, 50.0%, and 17.9% of cases, respectively. Most patients had good symptomatic palliation following administration of I131 therapy. In 17.9% of cases there were locoregional recurrences. There was an overall 28.6% mortality. Two patients expired in the perioperative period. Six others died in follow-up (all within 3-9 months). In contrast to iodine sufficient regions, the incidence of metastases was high; the majority of cases had synchronous, symptomatic skeletal metastases. Skeletal metastases were not infrequent even in cases of PTC and in young patients. One-third of the cases were young. Though survival was poor despite aggressive management, significant symptomatic palliation could be achieved in most cases.  相似文献   
210.
BACKGROUND: Tumour necrosis factor alpha (TNFalpha) is a major therapeutic target in a range of chronic inflammatory disorders characterised by a Th1 type immune response in which TNFalpha is generated in excess. By contrast, asthma is regarded as a Th2 type disorder, especially when associated with atopy. However, as asthma becomes more severe and chronic, it adopts additional characteristics including corticosteroid refractoriness and involvement of neutrophils suggestive of an altered inflammatory profile towards a Th1 type response, incriminating cytokines such as TNFalpha. METHODS: TNFalpha levels in bronchoalveolar lavage (BAL) fluid of 26 healthy controls, 42 subjects with mild asthma and 20 with severe asthma were measured by immunoassay, and TNFalpha gene expression was determined in endobronchial biopsy specimens from 14 patients with mild asthma and 14 with severe asthma. The cellular localisation of TNFalpha was assessed by immunohistochemistry. An open label uncontrolled clinical study was then undertaken in 17 subjects with severe asthma to evaluate the effect of 12 weeks of treatment with the soluble TNFalpha receptor-IgG1Fc fusion protein, etanercept. RESULTS: TNFalpha levels in BAL fluid, TNFalpha gene expression and TNFalpha immunoreative cells were increased in subjects with severe corticosteroid dependent asthma. Etanercept treatment was associated with improvement in asthma symptoms, lung function, and bronchial hyperresponsiveness. CONCLUSIONS: These findings may be of clinical significance in identifying TNFalpha as a new therapeutic target in subjects with severe asthma. The effects of anti-TNF treatment now require confirmation in placebo controlled studies.  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