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   410006篇
  免费   27192篇
  国内免费   4857篇
耳鼻咽喉   5459篇
儿科学   8552篇
妇产科学   10409篇
基础医学   56062篇
口腔科学   12298篇
临床医学   34341篇
内科学   81785篇
皮肤病学   8927篇
神经病学   28402篇
特种医学   14843篇
外国民族医学   101篇
外科学   63085篇
综合类   17351篇
一般理论   68篇
预防医学   19926篇
眼科学   10207篇
药学   34714篇
  40篇
中国医学   4221篇
肿瘤学   31264篇
  2021年   3532篇
  2020年   2919篇
  2019年   3493篇
  2018年   5186篇
  2017年   4357篇
  2016年   4240篇
  2015年   5470篇
  2014年   7791篇
  2013年   9398篇
  2012年   12924篇
  2011年   13333篇
  2010年   8572篇
  2009年   7774篇
  2008年   11632篇
  2007年   12407篇
  2006年   12246篇
  2005年   10982篇
  2004年   9835篇
  2003年   9462篇
  2002年   8992篇
  2001年   28856篇
  2000年   29347篇
  1999年   24186篇
  1998年   5369篇
  1997年   4496篇
  1996年   3944篇
  1995年   3717篇
  1994年   3317篇
  1993年   2954篇
  1992年   16167篇
  1991年   14920篇
  1990年   14234篇
  1989年   14008篇
  1988年   12651篇
  1987年   12117篇
  1986年   11137篇
  1985年   10348篇
  1984年   6931篇
  1983年   5615篇
  1982年   2727篇
  1979年   5482篇
  1978年   3345篇
  1977年   2963篇
  1975年   2632篇
  1974年   3062篇
  1973年   2862篇
  1972年   2823篇
  1971年   2763篇
  1970年   2507篇
  1969年   2540篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Post-induction hypotension is common and associated with postoperative complications. We hypothesised that pneumatic leg compression reduces post-induction hypotension in elderly patients undergoing robot-assisted laparoscopic prostatectomy. In this double-blind randomised study, patients were allocated randomly to the pneumatic leg compression group (n = 50) or control (n = 50). In the intervention group, pneumatic leg compression was initiated before induction of anaesthesia. In the control group, pneumatic leg compression was initiated 20 min after anaesthesia induction. The primary outcome was the incidence of post-induction hypotension in these groups. Post-induction hypotension was defined as systolic blood pressure < 90 mmHg during the first 20 min after induction. Haemodynamic variables and area under the curve of post-induction systolic blood pressure over time were assessed. Complications associated with pneumatic leg compression were recorded, including: peripheral neuropathy; compartment syndrome; extensive bullae beneath the leg sleeves; and pulmonary thromboembolism. The incidence of post-induction hypotension decreased in the pneumatic leg compression group compared with that in the control group; 5 (10%) vs. 29 (58%), respectively, p < 0.001. In the pneumatic leg compression group, the lowest systolic, diastolic and mean blood pressures 20 min after induction of anaesthesia were significantly greater than the control group. Pneumatic leg compression resulted in an increased area under the curve of systolic blood pressure in the first 20 min after induction, p = 0.001. There were no pneumatic leg compression-related complications. Pneumatic leg compression reduced post-induction hypotension in elderly patients undergoing robot-assisted laparoscopic prostatectomy, suggesting that it is an effective and safe intervention to prevent post-induction hypotension among elderly patients undergoing general anaesthesia.  相似文献   
2.
目的 探讨壮族居民生命早期饥荒经历与成年后中心型肥胖的关系。方法 将1 279名在1959—1961年经历饥荒的研究对象分为未经历组(1963年之后出生)、胎儿期经历组(1959—1962年出生)、儿童期经历组(1949—1958年出生)、青春期经历组(1941—1948年出生),采用二分类logistic回归模型评估壮族居民生命早期饥荒暴露与成年后中心型肥胖的关系。结果 壮族居民成年后中心型肥胖的发生率为30.88%。与未经历暴露人群相比,胎儿期暴露(OR=3.527,95%CI:1.877~6.627)和儿童期暴露(OR=2.863,95%CI:1.3297~6.167)的壮族居民成年后中心型肥胖的风险较高。结论 壮族居民生命早期经历饥荒是成年后中心型肥胖的危险因素。经历饥荒的广西壮族居民,应关注中心型肥胖发生情况,预防其他相关慢性病。  相似文献   
3.
目的研究2型糖尿病(T2DM)患者发生慢性肾脏病(CKD)的危险因素,并着重分析肥胖与CKD发生的关系。方法纳入2009年1月至2019年6月在南京鼓楼医院就诊的18至75岁诊断为T2DM的患者,收集一般资料包括性别、年龄、体重指数(BMI)、收缩压、舒张压、糖尿病病程以及实验室指标包括血红蛋白(Hb)、白蛋白、丙氨酸转氨酶(ALT)、天冬氨酸氨基转移酶(AST)、总胆红素(TBIL)、尿酸、空腹血糖(FPG)、糖化血红蛋白(HbA1c)、甘油三酯(TG)、总胆固醇(TC)、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C)、尿白蛋白/肌酐比值和估算的肾小球滤过率。肥胖定义为BMI≥28 kg/m2,超重定义为24 kg/m2≤BMI<28 kg/m2。根据是否合并CKD,将研究对象分为合并CKD组和不合并CKD组。在不合并CKD的T2DM患者中,选取至少随访一次,随访时间超过12个月且随访数据完整的患者,按是否发生CKD分为发生CKD组和未发生CKD组。两组间各指标的比较采用t检验、非参数检验以及χ2检验。采用单因素及多因素logistic回归分析法分析T2DM患者发生CKD的危险因素,采用Cox比例风险模型分析随访的T2DM患者CKD发生的危险因素。采用限制性立方样条(RCS)拟合Cox回归模型来评估不同的BMI截点与CKD的关系。结果共纳入3194例T2DM患者,其中合并CKD组620例,不合并CKD组2574例。与不合并CKD组相比,合并CKD组T2DM患者BMI明显增高(P=0.005)。单因素logistic回归分析结果显示,性别、肥胖、收缩压、舒张压、Hb、白蛋白、TG、TC、FPG及HbA1c为T2DM患者发生CKD的影响因素(均P<0.05),将上述指标作为自变量,进行多因素logistic回归分析,结果显示,肥胖(OR=1.058,95%CI 1.079~2.018),收缩压增高(OR=1.027,95%CI 1.018~1.035),TG增加(OR=1.087,95%CI 1.008~1.171),FPG增高(OR=1.042,95%CI 1.003~1.083)是T2DM患者发生CKD的影响因素(均P<0.05)。不合并CKD组中随访时间超过12个月且随访数据完整的T2DM患者共753例,其中,发生CKD组182例,未发生CKD组571例。Cox比例风险模型分析结果显示,在校正年龄、糖尿病病程、收缩压、AST、TG及FPG后,超重为发生CKD的危险因素(OR=1.95,95%CI 1.05~3.61)。RCS拟合Cox回归模型结果显示,T2DM患者BMI与CKD发生风险呈非线性关系,BMI在28~31 kg/m2的T2DM患者CKD的发生风险增加(均P<0.05)。结论T2DM患者肥胖与CKD密切相关,肥胖的T2DM患者,特别是BMI在28~31 kg/m2,容易发展为CKD。  相似文献   
4.
目的分析乙酰半胱氨酸泡腾片合用噻托溴铵吸入剂对慢性阻塞性肺疾病(COPD)患者的临床疗效。 方法选择2018年4月至2020年10月我院收治的COPD患者124例,分为观察组63例,对照组61例。给予对照组噻托溴铵吸入剂及其它常规治疗,观察组在对照组的治疗基础上加用乙酰半胱氨酸泡腾片治疗。比较两组治疗前及治疗3个月时的肺功能指标值、血气指标值及血清炎性因子水平;比较两组治疗3个月时的气流受限严重程度及呼吸困难程度。 结果治疗3个月时,两组患者的FEV1、FVC、FEV1/FVC值较治疗前提高,观察组高于对照组(P<0.05),两组血清IL-6、INF-γ、TNF-α水平较治疗前降低;观察组治疗3个月时的PaO2值高于对照组,PaCO2低于对照组,组间比较差异有统计学意义(P<0.05);治疗3个月时的气流受限程度两组间比较差异有统计学意义(P<0.05)。 结论乙酰半胱氨酸泡腾片联合噻托溴铵吸入剂治疗COPD具有较好临床疗效。  相似文献   
5.
目的:探讨近视儿童配戴多区正向光学离焦镜片后的主观视觉质量,并与角膜塑形镜、单焦点镜 片相比较。方法:前瞻性临床研究。收集2020年7—10月在南宁爱尔眼科医院视光中心配戴多区 正向光学离焦镜片31例(31眼)(DIMS组)、OK镜32例(32眼)(OK镜组)、单焦点镜片30例(30眼) (SV组)共93例(93眼)近视患者。配戴矫正镜片1个月后,采用Oculus视功能检查仪对3组进行全 程视力、对比敏感度、中间视觉、眩光、立体视等主观视觉质量检查。数据采用单因素方差分析、 卡方检验、秩和检验、Spearman相关性分析等方法进行分析。结果:3组患儿戴镜后近、远视力相 对于基线期变化值的差异均无统计学意义。在近、远立体视锐度当中3组差异无统计学意义,3组 在600″~200″立体视视锐度的人数分别都是最少的。3 组之间的对比敏感度差异有统计学意义 (F=17.96, P<0.001),合格例数最多的DIMS组有20例(65%)被检者对比敏感度≤15%。DIMS组在 有无眩光情况下,对比度等级(1:2.7、1:2.0)的通过率均高于OK镜组、SV组,且1:2.0对比度等级更 为明显,差异均有统计学意义(均P<0.001)。立体视锐度与年龄呈负相关(r=-0.30, P=0.008),与 屈光度数无相关性。眩光与对比敏感度间呈正相关(r=0.64, P<0.001),与性别、年龄、屈光度分析 均无相关性。结论:多区正向光学离焦镜片相对于角膜塑形镜及单焦点镜片而言,可提供更好的主 观视觉质量,有好的舒适性和安全性。  相似文献   
6.
Background

Vaccination prevents severe morbidity and mortality from COVID-19 in the general population. The immunogenicity and efficacy of SARS-CoV-2 vaccines in patients with antibody deficiency is poorly understood.

Objectives

COVID-19 in patients with antibody deficiency (COV-AD) is a multi-site UK study that aims to determine the immune response to SARS-CoV-2 infection and vaccination in patients with primary or secondary antibody deficiency, a population that suffers from severe and recurrent infection and does not respond well to vaccination.

Methods

Individuals on immunoglobulin replacement therapy or with an IgG less than 4 g/L receiving antibiotic prophylaxis were recruited from April 2021. Serological and cellular responses were determined using ELISA, live-virus neutralisation and interferon gamma release assays. SARS-CoV-2 infection and clearance were determined by PCR from serial nasopharyngeal swabs.

Results

A total of 5.6% (n?=?320) of the cohort reported prior SARS-CoV-2 infection, but only 0.3% remained PCR positive on study entry. Seropositivity, following two doses of SARS-CoV-2 vaccination, was 54.8% (n?=?168) compared with 100% of healthy controls (n?=?205). The magnitude of the antibody response and its neutralising capacity were both significantly reduced compared to controls. Participants vaccinated with the Pfizer/BioNTech vaccine were more likely to be seropositive (65.7% vs. 48.0%, p?=?0.03) and have higher antibody levels compared with the AstraZeneca vaccine (IgGAM ratio 3.73 vs. 2.39, p?=?0.0003). T cell responses post vaccination was demonstrable in 46.2% of participants and were associated with better antibody responses but there was no difference between the two vaccines. Eleven vaccine-breakthrough infections have occurred to date, 10 of them in recipients of the AstraZeneca vaccine.

Conclusion

SARS-CoV-2 vaccines demonstrate reduced immunogenicity in patients with antibody deficiency with evidence of vaccine breakthrough infection.

  相似文献   
7.
8.
Recent epidemiological studies suggested that proton pump inhibitor (PPI) use was associated with an increased risk of biliary tract cancer (BTC), however, confounders were not adequately controlled. Our study aimed to evaluate PPI use and subsequent risk of BTC and its subtypes in three well-established cohorts. We conducted a pooled analysis of the subjects free of cancers in UK Biobank (n = 463 643), Nurses' Health Study (NHS, n = 80 235) and NHS II (n = 95 869). Propensity score weighted Cox models were used to estimate marginal HRs of PPIs use on BTC risk, accounting for potential confounders. We documented 284 BTC cases in UK Biobank (median follow-up: 7.6 years), and 91 cases in NHS and NHS II cohorts (median follow-up: 15.8 years). In UK biobank, PPI users had a 96% higher risk of BTC compared to nonusers in crude model (HR 1.96, 95% CI 1.44-2.66), but the effect was attenuated to null after adjusting for potential confounders (HR 0.95, 95% CI 0.60-1.49). PPI use was not associated with risk of BTC in the pooled analysis of three cohorts (HR 0.93, 95% CI 0.60-1.43). We also observed no associations between PPI use with risk of intrahepatic (HR 1.00, 95% CI 0.49-2.04), extrahepatic bile duct (HR 1.09, 95% CI 0.52-2.27) and gallbladder cancers (HR 0.66, 95% CI 0.26-1.66) in UK Biobank. In summary, regular use of PPIs was not associated with the risk of BTC and its subtypes.  相似文献   
9.
The aim of this safety study in mice was to determine in vivo toxicity and biodistribution potential of a single and multiple doses of L-glutamic acid-g-p(HEMA) polymeric nanoparticles as a drug delivery system. The single dose did not cause any lethal effect, and its acute oral LD50 was >2.000 mg/kg body weight (bw). Multiple doses (25, 50, or 100 mg/kg bw) given over 28 days resulted in no significant differences in body and relative organ weights compared to control. These results are supported by biochemical and histological findings. Moreover, nanoparticle exposure did not result in statistically significant differences in micronucleus counts in bone marrow cells compared to control. Nanoparticle distribution was time-dependent, and they reached the organs and even bone marrow by hour 6, as established by ex vivo imaging with the IVIS® spectrum imaging system. In conclusion, L-glutamic acid-g-p(HEMA) polymeric nanoparticles appear biocompatible and have a potential use as a drug delivery system.KEY WORDS: biocompatibility, blood biochemistry, genotoxicity, histology, in vivo toxicity, micronucleus test, polymers  相似文献   
10.
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