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   179622篇
  免费   12959篇
  国内免费   4219篇
耳鼻咽喉   1357篇
儿科学   2537篇
妇产科学   3078篇
基础医学   23643篇
口腔科学   3362篇
临床医学   12243篇
内科学   23026篇
皮肤病学   2180篇
神经病学   11951篇
特种医学   6445篇
外国民族医学   1篇
外科学   14526篇
综合类   24071篇
现状与发展   21篇
一般理论   8篇
预防医学   14911篇
眼科学   2279篇
药学   25326篇
  53篇
中国医学   12565篇
肿瘤学   13217篇
  2024年   334篇
  2023年   2193篇
  2022年   4662篇
  2021年   7449篇
  2020年   6017篇
  2019年   6016篇
  2018年   6087篇
  2017年   6721篇
  2016年   6743篇
  2015年   6292篇
  2014年   7029篇
  2013年   10965篇
  2012年   8861篇
  2011年   10772篇
  2010年   6708篇
  2009年   6838篇
  2008年   8335篇
  2007年   9335篇
  2006年   8867篇
  2005年   8237篇
  2004年   7053篇
  2003年   6337篇
  2002年   5003篇
  2001年   4495篇
  2000年   3769篇
  1999年   3210篇
  1998年   2496篇
  1997年   2608篇
  1996年   2396篇
  1995年   2076篇
  1994年   2013篇
  1993年   1697篇
  1992年   1566篇
  1991年   1464篇
  1990年   1266篇
  1989年   1042篇
  1988年   1006篇
  1987年   905篇
  1986年   833篇
  1985年   1212篇
  1984年   969篇
  1983年   736篇
  1982年   758篇
  1981年   622篇
  1980年   607篇
  1979年   481篇
  1978年   298篇
  1977年   259篇
  1976年   245篇
  1975年   186篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
143.
144.
BackgroundThe peripheral level of matrix metalloproteinase (MMP)-9 and polymorphism of MMP9 -1562C>T in patients with obstructive sleep apnea (OSA) remains controversial. Therefore, the aims of this systemic review and meta-analysis are to assess the MMP9 level in OSA patients and identify the relationship between MMP9 -1562C>T and OSA susceptibility.MethodsThis systematic review was performed following the PRISMA guideline. We searched for studies in major databases, identifying those indexed from inception to July 3, 2019 which related to MMP9 level, MMP9 -1562C>T and OSA. The pooled standardized mean differences (SMDs) and 95% confidence interval (CI) of MMP9 levels were calculated. In addition, the relationship between MMP9 -1562C>T and OSA susceptibility was assessed by three genetic models. The heterogeneity analysis and calculation of the pooled odds ratio (OR) were also performed, followed by quality assessment using the Newcastle-Ottawa Scale (NOS).ResultsIn sum, our review included 15 eligible studies regarding MMP9 level and three regarding MMP9 -1562C>T. The pooled results showed that peripheral level of MMP9 was increased in OSA patients (SMD = 1.37; 95% CI = 1.15–1.59). Furthermore, significant difference of MMP9 level can be found between severe and mild-to-moderate OSA patients (SMD = 28.17; 95% CI = 4.23–52.11) or between moderate-severe and mild OSA (SMD = 36.62; 95% CI = 12.19–61.04). However, no relationship was observed between MMP9 -1562C>T and OSA susceptibility in three genetic models (Homozygote model, OR = 1.37; 95% CI = 0.87–2.18); (Recessive model, OR = 1.42; 95% CI = 0.83–2.42); (Allele model, OR = 1.07; 95% CI = 0.96–1.18).ConclusionsThis systemic review and meta-analysis indicated that the level of MMP9 was increased in patients with OSA and this increase is relevant to OSA severity. Moreover, the relationship between MMP9 -1562 C>T and OSA susceptibility has currently not been proven by current merging values. Further analyses with larger sample size are required to verify these associations.  相似文献   
145.
BackgroundArtificial insemination with the husband’s semen (AIH) is an economical and noninvasive method of infertility treatment. However, AIH’s pregnancy rate is much lower than in vitro fertilization (IVF) as its multiple and complex uncertainty factors. Semen quality has been one of the main factors which affect the pregnancy outcome of AIH.MethodsThe relevant parameters of 1,142 AIH cycles were retrospectively studied, including the general parameters and the semen quality parameters among clinical pregnancy, biochemical pregnancy, non-pregnancy group, age, infertility duration, infertility type, body mass index (BMI), cycle count, morphology in previously semen examination, and semen quality parameters on the day of AIH.ResultsThe statistically significant difference was only found on processed total non-forward and non-motile sperm count (N-TFMSC). The mean processed N-TFMSC in the biochemical pregnancy group was 6.37±4.27 million, significantly higher than the other two groups (vs. 4.40±3.15 million or vs. 4.48±3.60 million, P<0.05). The study was then divided into two groups according to processed N-TFMSC, Group 1 ≤5.0 million, and Group 2 >5.0 million. A statistical increase in biochemical pregnancy rate was observed when the processed N-TFMSC was >5.0 million (2.72% vs. 0.90%).ConclusionsProcessed N-TFMSC may be one of the independent factors on AIH’s outcome; it should be given equal attention the same as processed total forward motile sperm count (TFMSC).  相似文献   
146.
Diabetes is a complex, chronic metabolic disorder affecting approximately 9.3% of the adult population with the estimated number of adults with diabetes worldwide having more than tripled since 2000. This increase has largely been attributed to global urbanization and lifestyle changes. Diabetes affects 10–15% of the surgical population. These patients are frequently elderly, have complex medical co-morbidities and present for both high-risk elective and emergency surgery. This multisystem disease poses a significant challenge to both anaesthesia and surgery with patients with diabetes demonstrating higher morbidity and mortality rates compared to their non-diabetic counterparts. It is crucial that good glycaemic control is maintained throughout the perioperative period as this has been shown to correlate with positive patient outcomes. It is well-recognized that a co-ordinated, multidisciplinary approach aimed at optimizing every point in the patient pathway from GP referral to post-discharge care is required to obtain the best outcomes for the surgical patient with diabetes. The anaesthetist has a key role in the perioperative diabetes multidisciplinary team. Patients themselves are well experienced in manging their own diabetes and should be involved in doing so whenever possible.  相似文献   
147.
148.
Approximately 36 400 cardiac and 23 100 thoracic operations are carried out in the United Kingdom between 2006 and 2015. National Health Service (NHS) resolution, as known as the NHS litigation authority, is one of the essential bodies of the Department of Health. Its purpose is to provide NHS expertise to resolve concerns fair and square share learning for improvement. We aim to evaluate and increase awareness of medicolegal cases in cardiothoracic surgery. Total numbers and details of claims coded by NHS resolution in cardiothoracic surgery from 2004 to 2017 were requested under the Freedom of Information Act 2000. The data provided in successful claims is further breakdown into damages paid to the claimant, defence cost, claimant cost paid and the sum of the three. In contrast, unsuccessful claims only include the defence cost. Moreover, data provided also includes further analysis of primary causes and primary injuries for Claims Closed/Settled with damages paid. There were 753 claims recorded from 2004 to 2017, of which 415 (55.11%) were successful. The number of claims has been steadily increasing since 2004, with two significant raises from 2009/10 to 2010/11 (37‐55, 48.64% raise) and 2012/13 to 2013/14 (49‐69, 40.82% raise). The mean successful claim ratio was 69.58% (range, 47.56%‐ 83.33%) There is also a steady increase in the successful ratio from 2004 to 2017. In summary, this is the first study published in relation to litigation claims on cardiothoracic surgery in the United Kingdom. The results have provided insight on claims made against cardiothoracic surgery.  相似文献   
149.
It is well known that a meta-analysis of randomized controlled trials aims to increase the power and precision of the estimated intervention effects. However, when a meta-analysis includes a limited number of patients and a small number of events, overestimation of intervention effect estimates may occur and could cause spurious results. Although many biases can cause the overestimation, random error may be the most common cause. Trial sequential analysis (TSA) can explore the independent effect of random error on intervention effect estimates in meta-analyses and protect meta-analyses against overestimation due to random error.  相似文献   
150.
ABSTRACT

Tryptophan (Trp) is not only a nutrient enhancer but also has systemic effects. Trp metabolites signaling through the well-known aryl hydrocarbon receptor (AhR) constitute the interface of microbiome-gut-brain axis. However, the pathway through which Trp metabolites affect central nervous system (CNS) function have not been fully elucidated. AhR participates in a broad variety of physiological and pathological processes that also highly relevant to intestinal homeostasis and CNS diseases. Via the AhR-dependent mechanism, Trp metabolites connect bidirectional signaling between the gut microbiome and the brain, mediated via immune, metabolic, and neural (vagal) signaling mechanisms, with downstream effects on behavior and CNS function. These findings shed light on the complex Trp regulation of microbiome-gut-brain axis and add another facet to our understanding that dietary Trp is expected to be a promising noninvasive approach for alleviating systemic diseases.  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