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   267404篇
  免费   21517篇
  国内免费   10049篇
耳鼻咽喉   1266篇
儿科学   8949篇
妇产科学   2303篇
基础医学   23078篇
口腔科学   3653篇
临床医学   27332篇
内科学   68049篇
皮肤病学   2848篇
神经病学   26350篇
特种医学   8378篇
外国民族医学   19篇
外科学   23256篇
综合类   39380篇
现状与发展   46篇
一般理论   9篇
预防医学   20391篇
眼科学   2418篇
药学   20189篇
  218篇
中国医学   14000篇
肿瘤学   6838篇
  2024年   814篇
  2023年   5368篇
  2022年   9663篇
  2021年   13606篇
  2020年   12861篇
  2019年   9910篇
  2018年   9833篇
  2017年   10125篇
  2016年   10794篇
  2015年   10166篇
  2014年   18541篇
  2013年   20158篇
  2012年   15399篇
  2011年   16800篇
  2010年   13237篇
  2009年   12733篇
  2008年   12737篇
  2007年   12486篇
  2006年   11448篇
  2005年   9454篇
  2004年   7917篇
  2003年   6860篇
  2002年   5861篇
  2001年   5127篇
  2000年   4253篇
  1999年   3631篇
  1998年   3453篇
  1997年   3027篇
  1996年   2736篇
  1995年   2454篇
  1994年   2265篇
  1993年   1914篇
  1992年   1822篇
  1991年   1577篇
  1990年   1291篇
  1989年   1090篇
  1988年   1003篇
  1987年   890篇
  1986年   774篇
  1985年   901篇
  1984年   755篇
  1983年   474篇
  1982年   558篇
  1981年   471篇
  1980年   374篇
  1979年   321篇
  1978年   261篇
  1977年   222篇
  1976年   215篇
  1975年   82篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Immune defenses provide resistance against infectious disease that is critical to survival. But immune defenses are costly, and limited resources allocated to immunity are not available for other physiological or developmental processes. We propose a framework for explaining variation in patterns of investment in two important subsystems of anti-pathogen defense: innate (non-specific) and acquired (specific) immunity. The developmental costs of acquired immunity are high, but the costs of maintenance and activation are relatively low. Innate immunity imposes lower upfront developmental costs, but higher operating costs. Innate defenses are mobilized quickly and are effective against novel pathogens. Acquired responses are less effective against novel exposures, but more effective against secondary exposures due to immunological memory. Based on their distinct profiles of costs and effectiveness, we propose that the balance of investment in innate versus acquired immunity is variable, and that this balance is optimized in response to local ecological conditions early in development. Nutritional abundance, high pathogen exposure and low signals of extrinsic mortality risk during sensitive periods of immune development should all favor relatively higher levels of investment in acquired immunity. Undernutrition, low pathogen exposure, and high mortality risk should favor innate immune defenses. The hypothesis provides a framework for organizing prior empirical research on the impact of developmental environments on innate and acquired immunity, and suggests promising directions for future research in human ecological immunology.  相似文献   
62.
HER2-positive breast cancer is an aggressive subtype identified in the 1980s. The development of therapies targeting the HER2 has improved outcomes. The current standard of care, established in 2012 is dual blockade with trastuzumab + pertuzumab as first-line followed by TDM-1 as second-line. Several suboptimal choices are available in third-line or more. In 2019 the presentation of several trials evaluating new drugs and regimens in third-line has re-opened questions about sequencing, treatment of triple positive disease and treatment choice after exposure to TDM-1. These include tucatinib, neratinib and trastuzumab-deruxtecan. Other agents – including other antibody drug conjugates and bispecific antibodies as well as combinations - will lead to further changes in coming years. Additionally, should the numerous putative biomarkers thus identified ever come into use at the clinic, choice of treatment and response evaluation may be substantially changed.  相似文献   
63.
林娟 《北方药学》2020,(2):30-31
目的:探讨美托洛尔(β1受体阻滞剂)用于老年COPD合并冠心病史治疗的临床疗效。方法:选取2018年6月—2019年6月在我院接受治疗的60岁以上(包括60岁)COPD合并冠心病史老年患者,分为对照组与观察组。对照组给予接受布地奈德福莫特罗粉吸入剂治疗,观察组在使用布地奈德福莫特罗粉吸入剂治疗的基础上口服琥珀酸美托洛尔缓释片治疗,观察对比两组治疗效果。结果:观察组临床治疗效果优于对照组,观察组住院时长以及并发症的发生率低于对照组(P<0.05),差异具有统计学意义。结论:老年COPD合并冠心病史接受美托洛尔治疗,可有效缩短住院时长、用药效果明显、有效提升用药安全性,值得临床推广。  相似文献   
64.
Vascular-related gene polymorphism can affect the susceptibility of coronary heart disease. In current study, we aimed to evaluate the contribution of four vascular-related gene CpG-SNPs to coronary heart disease (CHD). A total of 784 angiography-proven CHD patients and 746 non-CHD controls were included in the current association study. The four CpG-SNPs (including VEGFA rs1005230, ACE rs4316, CST3 rs3827143 and AGTR1 rs275653) were genotyped using the Sequenom MassARRAY platform. All genotype distribution of four SNPs met HWE. Among the four CpG-SNPs, none was found to be associated with CHD on both genotype and allele levels. Further subgroup tests by age or gender were unable to observe any significant associations of them with CHD. Our case-control study showed that none of four CpG-SNPs in the vascular-related genes was associated with the risk of CHD in Han Chinese, although we could not exclude other genetic variants of these vascular-related genes with contribution to CHD.  相似文献   
65.
66.
ObjectiveThe beneficial effects of carnitine supplementation on nonalcoholic fatty liver disease are unclear. We conducted a systematic review and meta-analysis to evaluate the effects of carnitine supplementation on liver function, lipid profile, body mass index, body weight, and homeostasis model assessment of insulin resistance in patients with nonalcoholic fatty liver disease.MethodsA comprehensive search of PubMed, Web of Science, Scopus, Cochrane Library, and Google Scholar databases were performed. Only randomized placebo-controlled human studies that examined the effects of carnitine supplementation on liver function, lipid profile, body mass index, body weight, and homeostasis model assessment of insulin resistance up to September 2019 were included. Fixed effects or random-effects models were applied to compute the pooled effect size. Heterogeneity assessments were performed using Cochran’s Q test and I-squared statistics. The quality of the studies was assessed using the Jaded scale.ResultsA total of 5 articles were selected, including 334 individuals (167 in control and 167 in intervention groups). The results demonstrated that carnitine supplementation significantly reduced homeostasis model assessment of insulin resistance (HOMA-IR) (WMD: −0.91; 95 % CI: −1.11, −0.72; p < 0.001, I2 = 0.0 %) and the levels of aspartate aminotransferase (AST) (WMD: −16.62; 95 % CI: −28.11, −5.14; IU/l; p = 0.005, I2 = 93.5 %), alanine aminotransferase (ALT) (WMD: -33.39; 95 % CI: −45.13, −21.66; IU/l; p < 0.001, I2 = 93.4 %), and triglycerides (TG) (WMD: −22.13; 95 % CI: −38.91, −5.34; mg/dl; p = 0.01; I2 = 0.0 %). However, the results of the pooled effect size did not show any significant effect of carnitine supplementation on body mass index (BMI) (WMD: 0.07; 95 % CI: −0.15, 0.29; p = 0.55; I2 = 0.0 %), body weight (WMD: −0.28; 95 % CI: −2.23, 1.68; p = 0.78; I2 = 45.7 %), the levels of gamma-glutamyl transferase (γGT) (WMD: −11.31; 95 % CI: −24.35, 1.73; IU/l; p = 0.09, I2 = 61.1 %), cholesterol (WMD: −13.58; 95 % CI: −46.77, 19.60; mg/dl; p = 0.42; I2 = 94.9 %), high-density lipoprotein-cholesterol (HDL-C) (WMD: 1.36; 95 % CI: −0.96, 3.68; mg/dl; p = 0.25; I2 = 64.7 %), and low density lipoprotein-cholesterol (LDL-C) (WMD: −14.85; 95 % CI: −45.43, 15.73; mg/dl; p = 0.34; I2 = 96.4 %).ConclusionsThis analysis shows that carnitine supplementation for patients with nonalcoholic fatty liver disease demonstrates a reduction in AST, ALT, TG levels and HOMA-IR. However, no significant effect of carnitine supplementation was observed on BMI, body weight, the levels of γGT, TC, HDL-cholesterol and LDL-cholesterol.  相似文献   
67.
68.
69.
目的:探究原发性肝癌患者手术切除术后早期复发影响因素分析。方法:对广州市番禺区中医院2017年2月-2019年2月收治的原发性肝癌患者98例进行回顾性分析,依据各项临床指标分析手术切除术后早期复发的影响因素。结果:原发性肝癌患者经由手术切除后出现复发的可能性较高,同时手术切缘有残留、包膜不完整、肿瘤结节、心理因素、甲胎蛋白、血管侵犯、肝硬化及肿瘤直径等均是影响原发性肝癌手术期后再复发的高危因素。结论:原发性肝癌通常具有术后复发的生物学特性,依据对手术切除术之后早期复发因素的分析,对手术风险与治疗方案进行充分评估,同时要求患者进行定期复查及随访等工作,可对患者手术成功以及并发症的防治等均具有积极意义。  相似文献   
70.
目的:探究替米沙坦对冠心病合并糖尿病肾病患者疗效的影响情况。方法:56例探究目标对象均为某院接收的冠心病合并糖尿病肾病患者,挑选时间2018年6月~2019年6月。将"计算机表法"作为分组的参考,分配为参照组(n=28例)执行依那普利治疗,探究组(n=28例)执行替米沙坦治疗。结果:探究组的LVEF、LVEDd、肌酐、24h尿蛋白4项指标与参照组相比,差异有统计学意义(P<0.05);收缩压、舒张压、空腹血糖、餐后2h血糖4项指标与参照组相比,差异没有统计学意义(P>0.05)。结论:冠心病合并糖尿病肾病患者选择替米沙坦治疗后,心室功能的重构以及肾脏预后结局均得到改善,且临床效果比依那普利好,值得借鉴。  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