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   840篇
  免费   59篇
  国内免费   4篇
耳鼻咽喉   12篇
儿科学   28篇
妇产科学   25篇
基础医学   124篇
口腔科学   58篇
临床医学   53篇
内科学   195篇
皮肤病学   13篇
神经病学   37篇
特种医学   26篇
外科学   95篇
综合类   12篇
预防医学   101篇
眼科学   6篇
药学   51篇
肿瘤学   67篇
  2023年   11篇
  2022年   18篇
  2021年   31篇
  2020年   22篇
  2019年   33篇
  2018年   37篇
  2017年   37篇
  2016年   36篇
  2015年   37篇
  2014年   35篇
  2013年   47篇
  2012年   58篇
  2011年   67篇
  2010年   41篇
  2009年   40篇
  2008年   54篇
  2007年   40篇
  2006年   41篇
  2005年   32篇
  2004年   23篇
  2003年   20篇
  2002年   23篇
  2001年   10篇
  2000年   9篇
  1999年   10篇
  1998年   6篇
  1997年   8篇
  1996年   2篇
  1995年   3篇
  1994年   2篇
  1993年   6篇
  1992年   3篇
  1991年   4篇
  1990年   4篇
  1989年   6篇
  1988年   4篇
  1987年   7篇
  1986年   3篇
  1985年   3篇
  1984年   3篇
  1982年   3篇
  1981年   2篇
  1979年   2篇
  1978年   3篇
  1973年   2篇
  1966年   2篇
  1959年   1篇
  1954年   1篇
  1952年   1篇
  1940年   1篇
排序方式: 共有903条查询结果,搜索用时 15 毫秒
91.
This work describes an efficient micropropagation protocol for Verbena litoralis and the study of the antinociceptive and antioxidant activities in extracts of this species. For the establishment in vitro, surface-sterilization procedures and PVPP showed high efficiency in fungal-bacterial contamination and phenol oxidation controls. Nodal segments cultivation in MS medium supplemented with 6-benzyladenine (7.5 μM)/α-naphthaleneacetic acid (NAA; 0.005 μM) induced multiple shoots. Elongated shoots were rooted with IAA (0.2 μM). Acclimatization rates were elevated and the plants showed the typical features of this species. The hexanic fraction (HF) of powdered leaves presented a radical scavenging activity with IC(50) = 169.3 μg mL(-1). HF showed a non-dose dependent analgesic activity in the writhing test; its antinociceptive activity in the hot plate test was restricted to 500 mg kg(-1), which is the highest dose. The results of this study showed the potential of tissue culture on conservation and large scale multiplication and confirmed the traditional folk medicine use of V. litoralis.  相似文献   
92.
93.

Purpose

Previously, sleep in chronic obstructive pulmonary disease (COPD) has been objectively investigated only by lab-based polysomnography. The main purpose of this study was to evaluate sleep quality in COPD patients in their home environment using actigraphy. We also investigated the factors associated with sleep impairment and the relationship between objective and subjective sleep quality and daytime somnolence in these patients.

Methods

Twenty-six patients with moderate to very severe COPD and 15 controls were studied by actigraphy for at least 5 days. Subjective sleep quality was evaluated by the Pittsburgh Sleep Quality Index and daytime sleepiness by the Epworth Sleepiness Scale (ESS). Dyspnea was quantified by the modified Medical Research Council (MMRC) scale.

Results

COPD patients showed increased sleep latency (p?=?0.003), mean activity (p?=?0.003), and wake after sleep onset (p?=?0.003) and reduced total sleep time (TST; p?=?0.024) and sleep efficiency (p?=?0.001), as compared to controls. In patients, severity of dyspnea was correlated with sleep activity (r?=?0.41; p?=?0.04) and TST (r?=??0.46; p?=?0.02) and multiple regression analysis showed that MMRC score was the best predictor of TST (p?=?0.02) and sleep efficiency (p?=?0.03). Actigraphy measures during daytime were not significantly different between patients and controls. Subjective sleep quality was poorer in patients than controls (p?=?0.043). ESS scores were not significantly different between the two groups. Actigraphy measures were not correlated with subjective sleep quality or daytime somnolence in both groups.

Conclusions

Nocturnal sleep is markedly impaired in stable COPD patients studied by actigraphy in their home environment and this impairment is related to severity of dyspnea.  相似文献   
94.
95.
96.
Purpose:Incisions in cataract surgery can be modified in various ways in terms of size, shape, and axis to reduce or tailor astigmatism. This study was conducted to examine the effect of site (superior vs, temporal) and shape (frown vs. V-shaped, chevron) of scleral incisions for cataract surgery on corneal curvature.Methods:The prospective study was carried out on 200 consecutive patients with senile cataract and who were planned for surgery at a tertiary eye hospital in north India. The placement of the incision was decided by the steeper corneal meridian—whether superior or temporal—and then patients of these two groups were randomized for frown and V-shaped incision; in this way, four groups of 50 patients each were formed. Follow-up was done on day 1, at 2 weeks, 4 weeks, 8 weeks, and 12 weeks. At each follow-up, post-operative keratometry with routine postoperative examination was done. The results were statistically analyzed by using student’s t-test, Chi-squared test, and the Pearson correlation coefficient.Results:In all the four groups, the difference of preoperative astigmatism and surgically-induced astigmatism was statistically highly significant. The analysis of uncorrected visual acuity (UCVA) was statistically significant (P < 0.05) on postoperative day 1 and at 2, 4, and 12 postoperative weeks; it was statistically insignificant (P > 0.05) at postoperative week 8.Conclusion:Temporal incisions result in lesser postoperative surgically induced astigmatism (SIA) than superior incisions. Chevron incisions result in minimal change in corneal curvature. This effect can be utilized to tailor the postoperative astigmatism.  相似文献   
97.
Journal of Molecular Medicine - Although ependymoma (EPN) molecular subgroups have been well established by integrated high-throughput platforms, low- and middle-income countries still need...  相似文献   
98.
OBJECTIVE: This study evaluates the effect of shade and thickness of porcelain in light transmission. METHODS: One hundred and twenty-eight disks of Duceram porcelain were made to combine four different thicknesses (1.5; 2.0; 3.0; 4.0 mm) and eight shades (A(1); A(4); B(1); B(4); C(1); C(4); D(2); D(4)). A digital power meter (Newport Optical Power Meter was used to measure light transmission. The porcelain transmission coefficient was calculated using Lambert-Beer law, t(c)=Ce(-alphad), where t(c) is the transmission coefficient, C the contribution factor of the reflection coefficient, e a constant, alpha the absorption coefficient and d is the sample thickness. RESULTS: The transmission coefficients did not vary statistically in relation to the two visible light-curing units studied. From all the samples, the colors A(1) and D(2), thickness 1.5 mm, presented the highest percentages of transmission (8%) and the shades, A(4), B(4) and C(4), thickness 4 mm, the lowest (0.5%). The relationship between the Naperian logarithm of the transmission coefficient and the samples thickness followed the Lambert-Beer law. The linear adjustment of the experimental points of the two variables, showed the absorption coefficient (alpha) and the constant value related to the reflection (C) of each porcelain shade. The reflection coefficient values of all shades did not vary statistically among themselves. SIGNIFICANCE: For most shades there was a significant decrease in light transmission as the sample porcelain thickness increased. For the same thickness most shades presented statistical difference between the transmission coefficients. However, the larger the thickness, the higher the number of shades which, statistically, showed no difference.  相似文献   
99.
100.
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