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   7460篇
  免费   556篇
  国内免费   217篇
耳鼻咽喉   63篇
儿科学   132篇
妇产科学   66篇
基础医学   790篇
口腔科学   107篇
临床医学   717篇
内科学   929篇
皮肤病学   62篇
神经病学   519篇
特种医学   212篇
外国民族医学   1篇
外科学   1946篇
综合类   806篇
一般理论   3篇
预防医学   776篇
眼科学   44篇
药学   372篇
  2篇
中国医学   398篇
肿瘤学   288篇
  2024年   27篇
  2023年   169篇
  2022年   235篇
  2021年   373篇
  2020年   269篇
  2019年   326篇
  2018年   273篇
  2017年   233篇
  2016年   224篇
  2015年   243篇
  2014年   414篇
  2013年   532篇
  2012年   370篇
  2011年   380篇
  2010年   266篇
  2009年   352篇
  2008年   290篇
  2007年   237篇
  2006年   304篇
  2005年   227篇
  2004年   201篇
  2003年   194篇
  2002年   168篇
  2001年   185篇
  2000年   134篇
  1999年   110篇
  1998年   133篇
  1997年   132篇
  1996年   116篇
  1995年   102篇
  1994年   116篇
  1993年   97篇
  1992年   84篇
  1991年   97篇
  1990年   79篇
  1989年   68篇
  1988年   74篇
  1987年   66篇
  1986年   52篇
  1985年   60篇
  1984年   47篇
  1983年   29篇
  1982年   22篇
  1981年   39篇
  1980年   30篇
  1979年   21篇
  1978年   8篇
  1977年   14篇
  1975年   4篇
  1974年   3篇
排序方式: 共有8233条查询结果,搜索用时 421 毫秒
1.
2.
吴祎培  张羽  陈曦  冯希平 《口腔医学》2020,40(3):239-243
目的通过检查有龋及无龋母亲的口腔卫生状况,并通过随访收集其婴儿1个月(1月龄)及6个月(6月龄)的唾液样本测序分析,观察母亲患龋情况对其婴儿口腔微生物多样性的影响。方法通过筛查收集1月龄婴儿的唾液样本;于首次采样时记录母亲的口腔卫生状况,根据母亲患龋情况将婴儿分为母亲有龋组(简称有龋组)和母亲无龋组(简称无龋组),跟踪随访至婴儿6个月时再次收集唾液样本。通过高通量测序的方法,分析婴儿不同月龄微生物多样性的变化。结果本研究随访受试者10例(男6例,女4例),其中有龋组7例,无龋组3例,各组间的微生物群落多样性Shannon指数均无显著性差异(P>0.05)。无龋组婴儿1月龄至6月龄时微生物群落的物种组成有较大变化;有龋组婴儿在1月龄和6月龄时组内各样本间物种组成均差异较大;1月龄时两组微生物群落较相似,而至6月龄时两组婴儿唾液的物种组成已开始发生变化。结论有龋组婴儿口腔内菌群多样性总体高于无龋组,在1月龄至6月龄间婴儿口腔内微生物物种的多样性及丰度均有了不同程度的提高。  相似文献   
3.
4.
目的 利用筛选出十堰的天师栗中高多态性SSR位点评价天师栗种质资源的遗传多样性,结合有效药用成分含量,构建十堰地区天师栗核心种质库。方法 收集十堰地区114份天师栗种质资源,以七叶树基因组为参考,采用荧光毛细管电泳筛选出高多态性SSR位点,对天师栗种质资源进行遗传多样性分析。利用HPLC测定不同种质干燥娑罗子中七叶皂苷的含量。采用最小距离逐步聚类取样策略(LDSS),根据遗传多样性保留程度初步筛选出核心种质,并对该核心种质与原始种质的遗传多样性参数进行T检验,选择与原种质差异不显著的核心种质为最佳核心种质。结果 筛选出13对高多态性SSR分子标记,遗传多样性评价结果表明十堰地区天师栗种质资源遗传多样性较高,遗传分化较小,存在着较大的基因流,114份种质资源未分为不同的亚群,周家坝和辽叶居群间具有较近的遗传亲缘关系,且周家坝居群娑罗子中的七叶皂苷A及七叶皂苷B含量普遍较高。最终筛选出的核心种质共23份,占总种质资源的20.17%,其中周家坝12份样本、辽叶6份样本、普龄5份样本。结论 将SSR分子标记与主要有效药用成分结合,采用LDSS取样策略构建十堰地区天师栗种质资源核心种质库的方法具有可行性,能够有效的保存与管理天师栗种质资源,也为当地天师栗品种改良、新品种选育研究等提供了研究基础。  相似文献   
5.
Since the start of the COVID-19 pandemic, few studies have reported anaesthetic outcomes in parturients with SARS-CoV-2 infection. We reviewed the labour analgesic and anaesthetic interventions utilised in symptomatic and asymptomatic parturients who had a confirmed positive test for SARS-CoV-2 across 10 hospitals in the north-west of England between 1 April 2020 and 31 May 2021. Primary outcomes analysed included the analgesic/anaesthetic technique utilised for labour and caesarean birth. Secondary outcomes included a comparison of maternal characteristics, caesarean birth rate, maternal critical care admission rate along with adverse composite neonatal outcomes. A positive SARS-CoV-2 test was recorded in 836 parturients with 263 (31.4%) reported to have symptoms of COVID-19. Neuraxial labour analgesia was utilised in 104 (20.4%) of the 509 parturients who went on to have a vaginal birth. No differences in epidural analgesia rates were observed between symptomatic and asymptomatic parturients (OR 1.03, 95%CI 0.64–1.67; p = 0.90). The neuraxial anaesthesia rate in 310 parturients who underwent caesarean delivery was 94.2% (95%CI 90.6–96.0%). The rates of general anaesthesia were similar in symptomatic and asymptomatic parturients (6% vs. 5.7%; p = 0.52). Symptomatic parturients were more likely to be multiparous (OR 1.64, 95%CI 1.19–2.22; p = 0.002); of Asian ethnicity (OR 1.54, 1.04–2.28; p = 0.03); to deliver prematurely (OR 2.16, 95%CI 1.47–3.19; p = 0.001); have a higher caesarean birth rate (44.5% vs. 33.7%; OR 1.57, 95%CI 1.16–2.12; p = 0.008); and a higher critical care utilisation rate both pre- (8% vs. 0%, p = 0.001) and post-delivery (11% vs. 3.5%; OR 3.43, 95%CI 1.83–6.52; p = 0.001). Eight neonates tested positive for SARS-CoV-2 while no differences in adverse composite neonatal outcomes were observed between those born to symptomatic and asymptomatic mothers (25.8% vs. 23.8%; OR 1.11, 95%CI 0.78–1.57; p = 0.55). In women with COVID-19, non-neuraxial analgesic regimens were commonly utilised for labour while neuraxial anaesthesia was employed for the majority of caesarean births. Symptomatic women with COVID-19 are at increased risk of significant maternal morbidity including preterm birth, caesarean birth and peripartum critical care admission.  相似文献   
6.

Objective

To examine the experience of interracial anxiety among health professionals and how it may affect the quality of their interactions with patients from racially marginalized populations. We explored the influence of prior interracial exposure—specifically through childhood neighborhoods, college student bodies, and friend groups—on interracial anxiety among medical students and residents. We also examined whether levels of interracial anxiety change from medical school through residency.

Data Source

Web-based longitudinal survey data from the Medical Student Cognitive Habits and Growth Evaluation Study.

Study Design

We used a retrospective longitudinal design with four observations for each trainee. The study population consisted of non-Black US medical trainees surveyed in their 1st and 4th years of medical school and 2nd and 3rd years of residency. Mixed effects longitudinal models were used to assess predictors of interracial anxiety and assess changes in interracial anxiety scores over time.

Principal Findings

In total, 3155 non-Black medical trainees were followed for 7 years. Seventy-eight percent grew up in predominantly White neighborhoods. Living in predominantly White neighborhoods and having less racially diverse friends were associated with higher levels of interracial anxiety among medical trainees. Trainees' interracial anxiety scores did not substantially change over time; interracial anxiety was highest in the 1st year of medical school, lowest in the 4th year, and increased slightly during residency.

Conclusions

Neighborhood and friend group composition had independent effects on interracial anxiety, indicating that premedical racial socialization may affect medical trainees' preparedness to interact effectively with diverse patient populations. Additionally, the lack of substantial change in interracial anxiety throughout medical training suggests the importance of providing curricular tools and structure (e.g., instituting interracial cooperative learning activities) to foster the development of healthy interracial relationships.  相似文献   
7.
8.

Background and objective

Erector spinae plane block is a valid technique to provide simultaneously analgesia for combined thoracic and abdominal surgery.

Case report

A patient underwent open esophagectomy followed by reconstructive esophagogastroplasty but refused thoracic epidural analgesia; a multi‐modal analgesia with a multiple erector spinae plane block was then planned. Three erector spinae plane catheters (T5 and T10 on the right side and T9 on the left side) for continuous analgesia were placed before surgery. During the first 48 h pain was never reported in the thoracic area but the patient reported multiple times to feel a pain well localized in epigastrium, but never localized in any other abdominal quadrant.

Discussion

Erector spinae plane block is a valid technique to provide analgesia simultaneously for combined thoracic and abdominal surgery and could be a valid alternative strategy if the use of epidural analgesia is contraindicated.  相似文献   
9.
10.
The porcine circovirus type 2 (PCV2) is a swine infectious viral pathogen of great significance in global swine herds. It was recently detected at another Province of South Africa sequel to the first detection of North American‐like strain (PCV2a) at Gauteng about two decades ago, but there is a dearth of information about the genomic features and diversity of the viral strains in circulation within the country and the entire sub‐Saharan Africa region. To date, only one complete genome of the virus from South Africa is available on global data base. This current effort is therefore geared towards the full‐genome characterization of the circulating PCV2 strains in the pigs of Eastern Cape Province. With the use of conventional polymerase chain reaction method, fifteen complete PCV2 genomes were successfully amplified, sequenced and assembled from field samples obtained from non‐vaccinated pigs in the region. Neighbor Joining and Maximum Likelihood phylogenetic analyses of the ORF2 gene and full genomes unanimously showed that most of the assembled genomes (11) belong to genotype PCV2b. Furthermore, three of the characterized sequences formed clade with other reference mutant PCV2b and PCV2b subtype 1C (i.e. PCV2d) strains from the USA, China and South Korea. The last sequence, however, clustered with other reference strains belonging to PCV2 intermediate clade 2 (PCV2‐IM2), recently identified in a global PCV2 strains phylogenetic analysis. This study reports the first complete genome sequences of PCV2b, PCV2d and PCV2‐IM2 in pigs from South Africa, and it gives a possible insight into the genetic characteristics and variability of the viral strains presently in circulation within the country. It further emphasizes the need for more stringent measures in curtailing the introduction and spread of transboundary swine pathogens in the country and entire Southern African region.  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