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   15359篇
  免费   937篇
  国内免费   681篇
耳鼻咽喉   49篇
儿科学   140篇
妇产科学   73篇
基础医学   1715篇
口腔科学   946篇
临床医学   995篇
内科学   2494篇
皮肤病学   178篇
神经病学   1941篇
特种医学   292篇
外国民族医学   3篇
外科学   1380篇
综合类   2069篇
预防医学   793篇
眼科学   168篇
药学   2989篇
  5篇
中国医学   521篇
肿瘤学   226篇
  2023年   143篇
  2022年   165篇
  2021年   356篇
  2020年   301篇
  2019年   278篇
  2018年   300篇
  2017年   322篇
  2016年   317篇
  2015年   407篇
  2014年   719篇
  2013年   1024篇
  2012年   684篇
  2011年   716篇
  2010年   695篇
  2009年   664篇
  2008年   672篇
  2007年   669篇
  2006年   698篇
  2005年   645篇
  2004年   564篇
  2003年   541篇
  2002年   525篇
  2001年   489篇
  2000年   444篇
  1999年   404篇
  1998年   377篇
  1997年   417篇
  1996年   356篇
  1995年   335篇
  1994年   296篇
  1993年   229篇
  1992年   241篇
  1991年   228篇
  1990年   182篇
  1989年   212篇
  1988年   168篇
  1987年   132篇
  1986年   130篇
  1985年   183篇
  1984年   133篇
  1983年   112篇
  1982年   100篇
  1981年   102篇
  1980年   67篇
  1979年   63篇
  1978年   47篇
  1977年   32篇
  1976年   27篇
  1975年   19篇
  1973年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
BackgroundCalcium, one of the most abundant minerals in the human body, has a pivotal role in human physiology. However, only a few studies have examined the association of dietary calcium intake with mortality in a population with low calcium intake.ObjectiveThe aim of this study was to examine the association of dietary calcium intake with risk of all-cause and cause-specific mortality among Korean adults with low calcium intake.DesignThis study was a prospective cohort study.Participants/settingThe analysis was conducted using data from 44,327 eligible Korean adults aged 19 years and older who participated in the Korea National Health and Nutrition Examination Survey 2007-2015. Dietary calcium intake was assessed using 1-day 24-hour recall data.Main outcome measuresThe main outcomes of this study were mortality from all causes, cancer, cardiovascular disease, respiratory disease, and all other causes combined. The outcome was ascertained through linkage to the death registry compiled by Statistics Korea with the use of the resident registration number.Statistical analyses performedWeighted Cox proportional hazard models were used to estimate the hazard ratios and 95% CIs of the all-cause and cause-specific mortality according to dietary calcium intake.ResultsDuring a mean follow-up of 7.28 person-years, 1,889 deaths were ascertained. After multivariable adjustment, the hazard ratios for all-cause mortality for the second quintile to the highest quintile of dietary calcium intake, respectively, compared with the first quintile were 0.86 (95% CI 0.73 to 1.00), 0.82 (95% CI 0.69 to 0.98), 0.85 (95% CI 0.69 to 1.03), and 0.78 (95% CI 0.64 to 0.96) (P for trend from the lowest to the highest quintile = .04). There were no statistically significant associations between dietary calcium intake and risk of mortality from cancer, cardiovascular, or respiratory disease.ConclusionsIn this large prospective cohort study of Korean adults, lower dietary calcium intake was associated with a higher risk of all-cause mortality.  相似文献   
2.
《Dental materials》2022,38(2):397-408
ObjectivesComposite restorations with calcium fluoride nanoparticles (nCaF2) can remineralize tooth structure through F and Ca ion release. However, the persistence of ion release is limited. The objectives for this study were to achieve long-term remineralization by developing a rechargeable nCaF2 nanocomposite and investigating the F and Ca recharge and re-release capabilities.MethodsThree nCaF2 nanocomposites were formulated: (1) BT-nCaF2:Bisphenol A glycidyl dimethacrylate (BisGMA) and triethylene glycol dimethacrylate (TEGDMA); (2) PE-nCaF2:Pyromellitic glycerol dimethacrylate (PMGDM) and ethoxylated bisphenol A dimethacrylate (EBPADMA); (3) BTM-nCaF2:BisGMA, TEGDMA, and Bis[2-(methacryloyloxy)ethyl] phosphate (Bis-MEP). All formulations contained 15% nCaF2 and 55% glass particles. Initial flexural strength and elastic modulus, F and Ca ion release, recharge and re-release were tested and compared to three commercial fluoride-containing materials.ResultsBT and BTM nCaF2 composites were 3–4 times stronger and had elastic modulus 2 times that of resin-modified glass ionomer controls. PE-nCaF2 had comparable strength to RMGIs. All nCaF2 composites had significant F and Ca ion release and ion rechargeability. In F and Ca recharging cycles, PE-nCaF2 had the highest ion recharging capability among nCaF2 groups, followed by BT-nCaF2 and BTM-nCaF2 (p < 0.05). For all recharge cycles, ion release maintained similar levels, demonstrating long-term ion release was possible. Furthermore, after the final recharge cycle, nCaF2 nanocomposites provided continuous ion release for 42 days without further recharge.SignificanceNovel nCaF2 rechargeable nanocomposites exhibited significant F and Ca ion release over multiple recharge cycles, demonstrating continuous long-term ion release. These nanocomposites are promising restorations with lasting remineralization potential.  相似文献   
3.
目的分析低分子肝素钙抗凝对多囊卵巢综合征(PCOS)所致不孕症患者来曲唑诱导排卵疗效的影响。方法选取2014年1月—2019年1月九江市第三人民医院和彭泽县妇幼保健院收治的156例PCOS所致不孕症患者,采用随机数字表分成两组,每组78例。对照组口服来曲唑治疗,观察组采取口服来曲唑联合低分子肝素钙注射液治疗。比较两组的疗效、子宫内膜容受性、凝血功能指标、促排卵结局及不良反应。结果观察组总有效率[94.87%(74/78)]显著高于对照组[80.77%(63/78)],差异有统计学意义(χ2=7.252,P=0.007)。治疗后,观察组子宫内膜厚度、子宫动脉搏动指数(PI)及阻力指数(RI)分别为(9.75±1.03)mm、(1.30±0.26)及(0.58±0.12),对照组子宫内膜厚度、PI及RI分别为(7.48±0.95)mm、(1.71±0.33)及(0.66±0.11),两组比较差异均有统计学意义(t=14.308,8.619,4.340,均P<0.05)。治疗后,两组凝血功能指标比较差异均有统计学意义(均P<0.05)。观察组妊娠率[52.56%(41/78)]显著高于对照组[32.05%(25/78)],自然流产率[2.44%(1/41)]显著低于对照组[16.00%(4/25)],差异均有统计学意义(均P<0.05)。观察组不良反应发生率[16.67%(13/78)]与对照组[12.82%(10/78)]比较差异无统计学意义(χ2=0.459,P=0.498)。结论PCOS所致不孕症患者在应用来曲唑诱导排卵的同时联合低分子肝素钙抗凝治疗能有效改善患者的凝血-纤溶状态,明显提高患者的子宫内膜容受性,改善促排卵结局。  相似文献   
4.
BackgroundGrossman described the ideal properties of root canal sealers. The International Organization for Standardization and American National Standards Institute and American Dental Association have codified some of his requirements in ISO 6876 and ANSI/ADA 57, respectively. In this narrative review, the authors combined the ideal Grossman properties and requirements of these standards, emphasizing the newer tricalcium silicate cement sealers. This chemical matrix for such sealers was developed on the basis of the success of bioactive mineral trioxide aggregate–type (tricalcium silicate cement) materials for enhanced sealing and bioactivity.MethodsThe authors searched the internet and databases using Medical Subject Heading terms and then conducted a narrative review of those articles involving the tricalcium silicate cement endodontic sealers.ResultsNinety-four articles were identified that discussed tricalcium silicate cement sealers. Tricalcium silicate cement sealers are partially antimicrobial and have bioactivity, which may presage improved biological sealing of the root canal system. Most other properties of tricalcium silicate cement sealers are comparable with traditional root canal sealers.ConclusionsWithin the limitations of this review, tricalcium silicate cement endodontic sealers met many of the criteria for ideal properties, such as placement, antimicrobial properties, and bioactivity, but limitations were noted in solubility, dimensional stability (shrinkage and expansion), and retrievability.Practical ImplicationsTricalcium silicate–based cements have been commercialized as bioactive, bioceramic endodontic sealers. Warm, cold, and single-cone obturation techniques are usable, depending on the commercial product. Some sealers can cause discoloration and are not easily retrievable, particularly when used to completely obturate a canal.  相似文献   
5.
Astrocytes, the multi-functional glial cells with the most abundant population in the brain, integrate information across their territories to regulate neuronal synaptic and cerebrovascular activities. Astrocytic calcium (Ca2+) signaling is the major readout of cellular functional state of astrocytes. The conventional two-photon in vivo imaging usually focuses on a single horizontal focal plane to capture the astrocytic Ca2+ signals, which leaves >80% spatial information undetected. To fully probe the Ca2+ activity across the whole astrocytic territory, we developed a pipeline for imaging and visualizing volumetric astrocytic Ca2+ time-lapse images. With the pipeline, we discovered a new signal distribution pattern from three-dimensional (3D) astrocytic Ca2+ imaging data of mice under isoflurane anesthetic states. The tools developed in this study enable a better understanding of the spatiotemporal patterns of astrocytic activity in 3D space.  相似文献   
6.
7.
8.
9.
10.
目的探讨在关节镜清理术基础上载抗生素硫酸钙置入治疗原发性膝关节感染的临床效果。方法回顾性分析2017-06—2020-06在郑州大学第一附属医院骨科行关节镜清理术治疗的95例原发性膝关节感染患者的临床资料,按照处理方法分为载抗生素硫酸钙组(观察组,40例)和持续冲洗组(对照组,55例)。比较2组患者的基线资料、术中情况和术后临床指标。结果2组患者的基线资料、术中出血量、术后第1天时炎症指标、术后第3个月时Lysholm评分等应用比较,差异均无统计学意义(P>0.05)。观察组住院时间、住院费用、术后第3天和第6天的炎症指标、术后第6天时Lysholm评分、并发症发生率和感染复发率等指标均优于对照组,但手术时间长于对照组。上述差异均有统计学意义(P<0.05)。结论在关节镜清理术基础上应用载抗生素硫酸钙置入治疗原发性膝关节感染,可明显缩短患者的住院时间、术后炎症指标下降快、有利于膝关节功能尽早恢复。  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