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   4291篇
  免费   320篇
  国内免费   32篇
耳鼻咽喉   24篇
儿科学   232篇
妇产科学   54篇
基础医学   542篇
口腔科学   126篇
临床医学   444篇
内科学   1022篇
皮肤病学   108篇
神经病学   225篇
特种医学   470篇
外科学   511篇
综合类   42篇
一般理论   2篇
预防医学   240篇
眼科学   44篇
药学   243篇
  1篇
中国医学   7篇
肿瘤学   306篇
  2023年   15篇
  2022年   39篇
  2021年   73篇
  2020年   57篇
  2019年   85篇
  2018年   90篇
  2017年   71篇
  2016年   75篇
  2015年   87篇
  2014年   119篇
  2013年   175篇
  2012年   176篇
  2011年   210篇
  2010年   142篇
  2009年   181篇
  2008年   168篇
  2007年   177篇
  2006年   152篇
  2005年   170篇
  2004年   139篇
  2003年   149篇
  2002年   120篇
  2001年   100篇
  2000年   107篇
  1999年   109篇
  1998年   127篇
  1997年   147篇
  1996年   136篇
  1995年   98篇
  1994年   96篇
  1993年   120篇
  1992年   70篇
  1991年   72篇
  1990年   68篇
  1989年   80篇
  1988年   80篇
  1987年   53篇
  1986年   72篇
  1985年   63篇
  1984年   34篇
  1983年   32篇
  1982年   30篇
  1981年   49篇
  1980年   28篇
  1979年   28篇
  1978年   18篇
  1977年   30篇
  1976年   33篇
  1975年   17篇
  1971年   9篇
排序方式: 共有4643条查询结果,搜索用时 15 毫秒
101.
Background: Periodontal disease has been associated with diabetes, but there is still controversy on the relationship between periodontal clinical parameters and glycemic control. The purpose of this study is to assess the relationship between blood glucose levels and clinical parameters of periodontal disease in individuals with diabetes. Methods: A total of 65 individuals with diabetes and 81 individuals without diabetes were included in the study. A full-mouth periodontal examination and preprandial fasting glycemia values were recorded for each individual. Glycosylated hemoglobin was only measured in patients with diabetes. A comparative analysis between groups (Mann-Whitney U test) and a correlation analysis between glycemia and periodontal parameters were performed (Spearman test). Results: Patients without diabetes presented more teeth than individuals with diabetes (P <0.05). Patients with diabetes with periodontitis displayed loss of periodontal clinical attachment compared to patients without diabetes, but the highest value was observed in patients with periodontitis that reported a smoking habit. Furthermore, patients with diabetes with periodontitis presented higher glycemia and glycated hemoglobin values in contrast to patients with gingivitis. Patients with diabetes with hyperglycemia had a higher risk to develop periodontitis (odds ratio = 2.24; 95% confidence interval = 1.02 to 4.93). A positive correlation was observed between glycemia and clinical attachment loss (AL), whereas a negative correlation between glycemia and the number of teeth present was found (P <0.05). Conclusions: Tooth and periodontal AL were increased by hyperglycemia in individuals with diabetes. This study contributes additional evidence that diabetes could aggravate periodontal disease and affect the systemic health of individuals.  相似文献   
102.
Introduction: There is a high prevalence of methotrexate (MTX) use in males of reproductive age. The scope of this paper reviews what is known regarding risks to fertility and partners’ pregnancy outcomes with regard to MTX use in men.

Areas covered: This paper reviews the evidence for current recommendations for MTX use and male fertility and aims to educate professionals regarding MTX use in reproducing males so that patients may be counseled appropriately. A literature search included peer-reviewed sources from PubMed searches and the literature referenced within.

Expert opinion: There is a lack of evidence regarding effects of MTX on male fertility. The recommendation to stop MTX three months prior to conception is safe, but is not evidenced by an understanding of the impact of MTX on spermatogenesis or paternal-mediated teratogenicity but rather the timeframe of spermatogenesis. Given the unclear evidence, patients treated with MTX must be counseled on the likelihood of adverse effects of MTX and role of sperm cryopreservation. Future studies are needed to help elucidate the unclear evidence of MTX effects on male fertility and pregnancy outcomes.  相似文献   

103.
Neurological Sciences - Dolichoectasia is a form of brain large artery disease associated with a high risk of mortality and morbidity. Progressive enlargement of arterial size is a predictor of...  相似文献   
104.
B-1 cells are important players in the first line of defense against pathogens. According to current models for the origin of B-1 cells, they either represent a separate lineage from conventional B-2 cells or differentiate from conventional B-2 cells via an intermediate, B-1(int), in response to positive selection by antigen. Here we show that Btk, a Tec family kinase that mediates B cell antigen receptor (BCR) signaling, is required at multiple stages of B-1 cell development. VH12 anti-phosphatidylcholine (PtC) IgH transgenic mice provide a model for the induced differentiation of B-1 cells. This transgene selects for PtC-reactive cells and induces them to adopt a B-1 phenotype. Both processes have been shown to depend on Btk. To determine whether this is secondary to a requirement for Btk in the development of mature B-2 cells, we crossed VH12 transgenic mice to mice expressing low levels of Btk. B-2 cell development occurs normally in Btk(lo) mice despite reduced responsiveness to BCR crosslinking. Analysis of VH12.Btk(lo) mice reveals that Btk regulates the B-1(int) to B-1 transition and/or the survival of splenic B-1 cells, in part via a mechanism independent of its role in BCR signaling. We also show that Btk mediates the survival of, and expression of IL-10 by, those B-1 cells that do develop and migrate to the peritoneum. Multiple roles for Btk in B-1 cell development and maintenance may explain the particular sensitivity of this population to mutations in components of Btk signaling pathways.  相似文献   
105.

Introduction

This study aimed to determine whether ethnic differences show different patterns of arterial disease in the lower limb.

Methods

A prospective analysis of 100 consecutive patients with 160 lower limb arteriograms was performed looking at the pattern of disease with relation to ethnicity in Trinidad and Tobago.

Results

There were 53 male and 47 female patients with an age range of 43–90 years (mean: 66 years). Of the 100 patients, 45 were of East Indian descent, 36 of Afro-Caribbean descent, 14 of mixed descent and 5 had other backgrounds. There were 32 smokers and 69 diabetics.The most commonly affected artery in East Indians was the anterior tibial artery (ATA, 70%) followed by the peroneal artery (60%), superficial femoral artery (SFA, 60%), posterior tibial artery (PTA, 57%) and tibioperoneal trunk (TPT, 39%). In Afro-Caribbeans, the most commonly affected artery was the ATA (79%) followed by the PTA (74%), peroneal artery (66%) and TPT (55%). The mixed group showed the PTA (85%) to be most diseased followed by the peroneal artery (75%), ATA (70%), SFA (70%), dorsalis pedis artery (DPA, 60%) and TPT (50%). Overall, the most diseased vessel in all groups was the ATA (73%) followed by the PTA (66%), peroneal artery (64%), SFA (59%), TPT (46%), DPA (38%), popliteal artery (31%) and medial plantar artery (MPA, 29%), with the proximal vessels not being affected severely.

Conclusions

Ethnic divisions were only statistically significant (p<0.05) with East Indians showing worse disease in the profunda femoris artery and Afro-Caribbeans showing worse disease in the PTA, DPA and MPA. This suggests that environmental factors may play a significant role in the disease process including smoking and dietary factors rather than purely genetics.  相似文献   
106.

Introduction

In 2009 the Department of Health instructed McKinsey & Company to provide advice on how commissioners might achieve world class National Health Service productivity. Asymptomatic inguinal hernia repair was identified as a potentially cosmetic procedure, with limited clinical benefit. The Birmingham and Solihull primary care trust cluster introduced a policy of watchful waiting for asymptomatic inguinal hernia, which was implemented across the health economy in December 2010. This retrospective cohort study aimed to examine the effect of a change in clinical commissioning policy concerning elective surgical repair of asymptomatic inguinal hernias.

Methods

A total of 1,032 patients undergoing inguinal hernia repair in the 16 months after the policy change were compared with 978 patients in the 16 months before. The main outcome measure was relative proportion of emergency repair in groups before and after the policy change. Multivariate binary logistic regression was used to adjust the main outcome for age, sex and hernia type.

Results

The period after the policy change was associated with 59% higher odds of emergency repair (3.6% vs 5.5%, adjusted odds ratio [OR]: 1.59, 95% confidence interval [CI]: 1.03–2.47). In turn, emergency repair was associated with higher odds of adverse events (4.7% vs 18.5%, adjusted OR: 3.68, 95% CI: 2.04–6.63) and mortality (0.1% vs 5.4%, p<0.001, Fisher’s exact test).

Conclusions

Introduction of a watchful waiting policy for asymptomatic inguinal hernias was associated with a significant increase in need for emergency repair, which was in turn associated with an increased risk of adverse events. Current policies may be placing patients at risk.  相似文献   
107.

Introduction

An individual’s genetic background plays a significant role in his or her chances of developing an abdominal aortic aneurysm (AAA). This risk is likely to be due to a combination of multiple small effect genetic factors acting together, resulting in considerable difficulty in the identification of these factors.

Methods

Methods for the identification of genetic factors associated with disease are usually based on the analysis of genetic variants in case-control studies. Over the last decade, owing to advances in bioinformatics and laboratory technology, these studies have progressed from focusing on the examination of a single genetic variant in each study to the examination of many millions of variants in a single experiment. We have conducted a series of such experiments using these methods.

Results

Our original methods using candidate gene approaches led to the initial identification of a genetic variant in the interleukin-10 gene associated with AAA. However, further studies failed to confirm this association and highlighted the necessity for adequately powered studies to be conducted, as well as the need for confirmatory studies to be performed, prior to the acceptance of a variant as a risk for disease. The subsequent application of genomic techniques to our sample set, in a global collaboration, has led to the identification of three robustly verified risk loci for AAA in the LRP1, LDLR and SORT1 genes.

Conclusions

Genomic studies of AAA have led to the identification of new pathways involved in the pathogenesis of AAA. The exploration of these pathways has the potential to unlock new avenues for therapeutic intervention to prevent the development and progression of AAA.  相似文献   
108.
BackgroundThe worldwide seroprevalence of human BK polyomavirus (BKV) in adults is 80%. About 10%–60% of renal transplant recipients experience BKV infection, nephropathy of the graft may occur in 5% of the cases, and up to 45% lose the graft. The aim of this work was to describe the prevalence of BK viruria during the 1st year after transplantation.MethodsAn epidemiologic multicenter cross-sectional study was carried out in consecutive patients at each site with kidney transplantation from August 2011 to July 2012. Clinically significant viruria was defined as >107 copies/mL. Viral DNA was extracted with the use of silica columns. Quantification was performed with the use of real-time polymerase chain reaction with primers that amplify a fragment of the large T-antigen gene and with a specific Taqman-MGB probe for BKV. For each assay, a standard curve with a quantified plasmid was included.ResultsOf 402 renal transplant recipients at 18 renal transplant sites, we analyzed 382; median age was 46.33 years, and 46.40% were female. The median of the temporal distribution for urine samples was 153 days. BK virus was detected in 50/382 samples (13%), 18 with values >107 copies/mL (4.7%). The median of the distribution of positive values was 123 days and the highest frequency of positive values was in months 3–7. The conditions of recipient older than 34 years and donor older than 41 years were the only ones that showed statistically significant association with BK viruria. No association with any specific immunosuppressive drug was observed.ConclusionsThis is the first multicenter study conducted in Argentina to determine the prevalence of BK viruria in renal transplant recipients. Because of the growing number of the population susceptible to this infection, it is important to register and describe data about its epidemiology and associated risk factors.  相似文献   
109.
Chronic stress and depression have adverse consequences on many organ systems, including the skeleton, but the mechanisms underlying stress‐induced bone loss remain unclear. Here we demonstrate that neuropeptide Y (NPY), centrally and peripherally, plays a critical role in protecting against stress‐induced bone loss. Mice lacking the anxiolytic factor NPY exhibit more anxious behavior and elevated corticosterone levels. Additionally, following a 6‐week restraint, or cold‐stress protocol, Npy‐null mice exhibit three‐fold greater bone loss compared to wild‐type mice, owing to suppression of osteoblast activity. This stress‐protective NPY pathway acts specifically through Y2 receptors. Centrally, Y2 receptors suppress corticotropin‐releasing factor expression and inhibit activation of noradrenergic neurons in the paraventricular nucleus. In the periphery, they act to control noradrenaline release from sympathetic neurons. Specific deletion of arcuate Y2 receptors recapitulates the Npy‐null stress response, coincident with elevated serum noradrenaline. Importantly, specific reintroduction of NPY solely in noradrenergic neurons of otherwise Npy‐null mice blocks the increase in circulating noradrenaline and the stress‐induced bone loss. Thus, NPY protects against excessive stress‐induced bone loss, through Y2 receptor‐mediated modulation of central and peripheral noradrenergic neurons. © 2014 American Society for Bone and Mineral Research.  相似文献   
110.
ObjectivesThe purpose of this study was to describe coping strategies (eg, mechanisms, including self-treatment) that a person uses to reduce pain and its impact on functioning as reported by patients with chronic low back pain who were seen by doctors of chiropractic and how these coping strategies vary by patient characteristics.MethodsData were collected from a national sample of US chiropractic patients recruited from chiropractic practices in 6 states from major geographical regions of the United States using a multistage stratified sampling strategy. Reports of coping behaviors used to manage pain during the past 6 months were used to create counts across 6 domains: cognitive, self-care, environmental, medical care, social activities, and work. Exploratory analyses examined counts in domains and frequencies of individual items by levels of patient characteristics.ResultsA total of 1677 respondents with chronic low back pain reported using an average of 9 coping behaviors in the prior 6 months. Use of more types of behaviors were reported among those with more severe back pain, who rated their health as fair or poor and who had daily occurrences of pain. Exercise was more frequent among the healthy and those with less pain. Female respondents tended to report using more coping behaviors than men, and Hispanics more than non-Hispanics.ConclusionPersons with chronic back pain were proactive in their coping strategies and frequently used self-care coping strategies like those provided by chiropractors in patient education. In alignment with patients’ beliefs that their condition was chronic and lifelong, many patients attempted a wide range of coping strategies to relieve their pain.  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