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   1583篇
  免费   131篇
  国内免费   71篇
耳鼻咽喉   12篇
儿科学   39篇
妇产科学   6篇
基础医学   231篇
口腔科学   22篇
临床医学   137篇
内科学   240篇
皮肤病学   4篇
神经病学   283篇
特种医学   40篇
外科学   60篇
综合类   202篇
预防医学   59篇
眼科学   21篇
药学   249篇
中国医学   164篇
肿瘤学   16篇
  2023年   19篇
  2022年   27篇
  2021年   100篇
  2020年   74篇
  2019年   49篇
  2018年   65篇
  2017年   56篇
  2016年   77篇
  2015年   70篇
  2014年   112篇
  2013年   121篇
  2012年   92篇
  2011年   105篇
  2010年   71篇
  2009年   70篇
  2008年   63篇
  2007年   73篇
  2006年   60篇
  2005年   49篇
  2004年   39篇
  2003年   29篇
  2002年   30篇
  2001年   31篇
  2000年   25篇
  1999年   27篇
  1998年   22篇
  1997年   24篇
  1996年   17篇
  1995年   19篇
  1994年   14篇
  1993年   16篇
  1992年   14篇
  1991年   15篇
  1990年   9篇
  1989年   12篇
  1988年   8篇
  1987年   10篇
  1986年   12篇
  1985年   10篇
  1984年   16篇
  1983年   3篇
  1982年   4篇
  1981年   6篇
  1980年   8篇
  1979年   2篇
  1978年   2篇
  1977年   2篇
  1976年   2篇
  1971年   1篇
  1970年   1篇
排序方式: 共有1785条查询结果,搜索用时 31 毫秒
101.
目的:优选清脉颗粒的醇沉工艺。方法:选取药液相对密度,醇沉浓度及醇沉时间为考察因素,以干浸膏得率,薯蓣皂苷元苷含量为考察指标,采用正交试验优选醇沉工艺。结果:优选的醇沉工艺为药液浓缩至相对密度1.13 - 1.18 g·;ml-1,加乙醇至乙醇体积分数为60%,醇沉24 h。结论:优选的工艺稳定可行,为清脉颗粒的临床应用提供试验依据。  相似文献   
102.
优选复方参芪软胶囊的醇沉工艺。方法:采用正交试验设计,以药液中总多糖的含量和干膏得率为指标,考察浓缩液的相对密度、醇沉浓度、静置时间、醇沉温度对醇沉效果的影响。结果:最佳醇沉工艺为药液浓缩至相对密度1.10,加95%乙醇至含醇量为60%,室温下静置48h。结论:优选的复方参芪软胶囊醇沉工艺简便易行,适用于实际生产配制。  相似文献   
103.
Context: Traditionally, the content of total phenolics (flavonoid phenolics (FP) and non-flavonoid phenolics (NFP)) and flavonoids (flavone/flavonol and flavonone/dihydroflavonol) in propolis has been determined by different methodologies. Until now, the percentage of total phenolic (TP) compounds that corresponds to FP and NFP, expressed in the same units by a spectrophotometric method, has not been determined.

Objective: The current study proposes a quick and simple methodology that separates FP and NFP in propolis samples and determines TP, FP, and NFP by the same method.

Materials and methods: Propolis samples from five Argentine provinces (Tucumán, Santiago del Estero, Salta, Misiones, and Jujuy) were used. Extraction of TP from the propolis samples was carried out by maceration with 80% ethanol and quantified by Folin–Ciocalteu reagent (FC-R). Then, FP was precipitated with formaldehyde in acid medium. After centrifugation, NFP were determined in the supernatant using FC-R. FP content was calculated as the difference between the content of TP and NFP. The method was also validated using commercial flavonoids and chalcones.

Results: FP recovery in all experiments was between 85.95% and 98.29%. Propolis from Tucumán had significantly higher amounts of total phenols than propolis from other provinces. SE5 showed higher content of FP (81.52%) followed by SA1 (74.75%). The propolis from TUC4, SA4, SE3, and MI showed the lowest FP content and highest content of NFP.

Conclusions: This method provides a simple, reliable, and specific spectrophotometric assay to estimate the content of NFP, FP, and TP in propolis samples.  相似文献   

104.
105.
李涛 《临床肺科杂志》2012,17(11):1995-1996
目的探讨阻塞性睡眠呼吸暂停低通气综合征病人呼吸阻抗力的临床意义。方法选取70例OSAHS和肺通气功能检测正常的病人为研究对象,按照呼吸暂停低通气指数(AHI)分成轻、中、重度,探讨两组病人呼吸阻抗力的差异。结果两组病人采用4 Hz和16 Hz两个振荡频率进行比较,发现中重度组病人阻力增加较为显著,但差异无显著性(P>0.05),但是采用8 Hz时显示两者差异具有显著性(P<0.05)。结论研究示OSAHS病人肺功能正常时,其小气道可有病变。脉波振荡肺功能(IOS)对于诊断OSAHS具有临床意义。  相似文献   
106.
The effects of anisotropic interfacial properties and heterogeneous elasticity on the growth and ripening of plate-like θ′-phase (Al2Cu) in Al-1.69 at.% Cu alloy are studied. Multi-phase-field simulations are conducted and discussed in comparison with aging experiments. The precipitate/matrix interface is considered to be anisotropic in terms of its energy and mobility. We find that the additional incorporation of an anisotropic interfacial mobility in conjunction with the elastic anisotropy result in substantially larger aspect ratios of the precipitates closer to the experimental observations. The anisotropy of the interfacial energy shows comparably small effect on the precipitate’s aspect ratio but changes the interface’s shape at the rim. The effect of the chemo-mechanical coupling, i.e., the composition dependence of the elastic constants, is studied as well. We show that the inverse ripening phenomenon, recently evidenced for δ’ precipitates in Al-Li alloys (Park et al. Sci. Rep. 2019, 9, 3981), does not establish for the θ′ precipitates. This is because of the anisotropic stress fields built around the θ′ precipitates, stemming from the precipitate’s shape and the interaction among different variants of the θ′ precipitate, that disturb the chemo-mechanical effects. These results show that the chemo-mechanical effects on the precipitation ripening strongly depend on the degree of sphericity and elastic isotropy of the precipitate and matrix phases.  相似文献   
107.
This geographical study aimed to show natural or water-processing-related factors of faecal contamination incidents (FCIs) of drinking water in continental France. We defined a FCI as the occurrence of at least 20 colony-forming Escherichia coli or enterococci among all the 100 mL samples collected for regulatory purpose within one day from a given drinking water supply zone (SZ). We explored correlations between the standardized number of FCIs per département (N_Pols) and various indicators related to weather, land cover, topography, geology and water management for three SZ size sub-classes. In 2003–2004, 2,739 FCIs occurred in SZs supplying fewer than 2,000 people, mainly with simply disinfected groundwater. N_Pols correlates with four covariates: (1) precipitation; (2) the extension of the karst outcrops; (3) the extent of disinfection; and (4) catchment protection. One hundred millimetres of yearly excess in precipitation increases the pollution risk by 28–37%, depending on the sub-class. A 10% extension of the karst areas, a 10% increase of unprotected resources, or of SZs with no disinfection, could entail a higher risk of FCI by about 10%. The correlations are reproducible over the three sub-classes and corroborate expert appraisals. These results encourage the ongoing effort to generalize disinfection and catchment protection.  相似文献   
108.
109.
目的:研究超低频电磁场对硝普钠诱导的SD大鼠肋骨骨骺软骨细胞凋亡的影响。方法:不同浓度硝普钠诱导软骨细胞凋亡,检测不同时间软骨细胞半数致死量(LD50)的硝普钠浓度;观察超低频电磁场对软骨细胞凋亡的影响。结果:半数软骨细胞致死的硝普钠浓度呈时间依赖性下降;经超低频电磁场和硝普钠同时作用后的细胞凋亡率明显低于单纯硝普钠作用的细胞凋亡率(P<0.05);单纯硝普钠诱导的细胞在超微结构上有典型的凋亡改变,超低频电磁场能在一定程度上恢复软骨细胞的正常结构。结论:超低频电磁场能抑制硝普钠诱导体外培养的大鼠软骨细胞的凋亡。  相似文献   
110.
Objective To evaluate standardized lung recruitment strategy during both high frequency oscillation (HFO) and volume-targeted conventional ventilation (CV+V) in spontaneously breathing piglets with surfactant washout on pathophysiologic and inflammatory responses.Design Prospective animal study.Setting Research laboratory.Subjects Twenty-four newborn piglets.Interventions We compared pressure support and synchronized intermittent mandatory ventilation, both with targeted tidal volumes, (PSV+V, SIMV+V) to HFO. Animals underwent saline lavage to produce lung injury, received artificial surfactant and were randomized to one of the three treatment groups (each n=8). After injury and surfactant replacement, lung volumes were recruited in all groups using a standard protocol. Ventilation continued for 6 h.Measurements and main results Arterial and central venous pressures, heart rates, blood pressure and arterial blood gases were continuously monitored. At baseline, post lung injury and 6 h we collected serum and bronchoalveolar lavage samples for proinflammatory cytokines: IL 6, IL 8 and TNF-, and performed static pressure-volume (P/V) curves. Lungs were fixed for morphometrics and histopathologic analysis. No physiologic differences were found. Analysis of P/V curves showed higher opening pressures after lung injury in the HFO group compared to the SIMV+V group (p<0.05); no differences persisted after treatment. We saw no differences in change in proinflammatory cytokine levels. Histopathology and morphometrics were similar. Mean airway pressure (Paw) was highest in the HFO group compared to SIMV+V (p<0.002).Conclusions Using a standardized lung recruitment strategy in spontaneously breathing animals, CV+V produced equivalent pathophysiologic outcomes without an increase in proinflammatory cytokines when compared to HFO.This study was supported in part by a grant from the Research and Education Fund of Childrens Hospitals and Clinics–St. Paul, Minnesota. Dräger Babylog supplied by Dräger Critical Care Systems, Survanta provided by Ross laboratories.  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