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   388956篇
  免费   36839篇
  国内免费   24485篇
耳鼻咽喉   2925篇
儿科学   4990篇
妇产科学   4233篇
基础医学   42676篇
口腔科学   6417篇
临床医学   54561篇
内科学   52276篇
皮肤病学   4255篇
神经病学   19152篇
特种医学   14062篇
外国民族医学   224篇
外科学   34697篇
综合类   71619篇
现状与发展   86篇
一般理论   32篇
预防医学   28349篇
眼科学   10991篇
药学   41542篇
  521篇
中国医学   25413篇
肿瘤学   31259篇
  2025年   312篇
  2024年   6412篇
  2023年   7508篇
  2022年   15187篇
  2021年   19708篇
  2020年   15720篇
  2019年   12726篇
  2018年   12355篇
  2017年   11914篇
  2016年   11046篇
  2015年   17024篇
  2014年   21142篇
  2013年   19226篇
  2012年   28549篇
  2011年   32024篇
  2010年   21619篇
  2009年   17597篇
  2008年   21496篇
  2007年   21230篇
  2006年   20267篇
  2005年   19348篇
  2004年   12791篇
  2003年   12326篇
  2002年   10095篇
  2001年   8597篇
  2000年   8377篇
  1999年   8458篇
  1998年   5352篇
  1997年   5128篇
  1996年   3993篇
  1995年   3742篇
  1994年   3157篇
  1993年   2042篇
  1992年   2433篇
  1991年   2132篇
  1990年   1799篇
  1989年   1559篇
  1988年   1289篇
  1987年   1194篇
  1986年   956篇
  1985年   679篇
  1984年   371篇
  1983年   271篇
  1982年   142篇
  1981年   169篇
  1980年   118篇
  1979年   154篇
  1978年   73篇
  1977年   53篇
  1974年   42篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
Lin  Hua  Li  Muwei  Zhan  Yang  Lin  Li  Yang  Kun  Hu  Shimin  Han  Ying 《Brain imaging and behavior》2021,15(4):1739-1747

The ε4 allele of the APOE gene is thought to increase risk from amnestic mild cognitive impairment (aMCI) to Alzheimer’s disease. Cognitive decline in the condition is increasingly considered to worsen functional disconnections in brain network composed of gray matter and white matter. Nevertheless, Whether APOEε4 targets specific white matter functional connectivity in patients with aMCI remains mostly unexplored, mainly due to the challenges of detecting BOLD signals in white matter. Here, we applied a novel approach to investigate APOEε4-related specific bundles and cortical area alterations in aMCI subjects, in order to characterize white matter-gray matter functional connectivity differences throughout the brain. We analyzed 75 patients with aMCI and 76 demographically matched normal controls. The aMCI APOEε4 carriers showed decreased functional connectivity located at left corticospinal tract, bilateral posterior limb of internal capsule, and right temporopolaris, which was different from the regions of aMCI-related changes. We further found that recognition scores were positively associated with the right temporopolaris in aMCI APOEε4 carriers. Collectively, the data provide new evidence that APOEε4 genotype exerts a negative impact on neural activity in both gray and white matter in aMCI, which potentially contributes to functional disconnection and memory decline. A novel method provides full-scale measuring effect of disease conditions on functional architecture throughout the brain. Trial registration: https://www.ClinicalTrials.gov (Identifier: NCT02225964). Registered January 2014.

  相似文献   
13.
李玉清  杨春霞 《北京中医药》2006,25(11):643-645
目的 研究补肺活血法治疗慢性阻塞性肺疾病缓解期的临床疗效和对肺功能的影响.方法 将125例患者随机分为治疗组85例和对照组40例,两组均经缓解期常规基础治疗,治疗组加用中药汤剂口服.两组均以2周为1个疗程,连续治疗4个疗程后统计疗效.结果 治疗组总有效率为94.1%,对照组总有效率为90.0%,两组相比,P<0.05;两组的主要症状和体征均改善,但治疗组对咳嗽、咳痰、喘促、气短以及肺部罗音等症状体征改善均优于对照组(P<0.01);治疗组的肺功能的改善优于对照组(P<0.05);治疗组的发病次数明显少于对照组(P<0.05).结论 补肺活血法能有效改善慢性阻塞性肺疾病缓解期患者的临床症状、体征、肺功能,减少患者发病次数,并提高其生活质量.  相似文献   
14.
增生性瘢痕是皮肤遭遇创伤后,因细胞外基质异常沉积、过度纤维化造成的皮肤病理现象。对于瘢痕诊断、临床疗效判定及比较研究,临床上使用的客观且可靠的瘢痕评判方法具有关键作用。我们就增生性瘢痕的评估、测量方式及工具的研究进展进行综述。  相似文献   
15.
Three new diketopiperazine derivatives (DKPs), saroclazines A–C (13) along with three known DKPs (46) were isolated from mangrove-derived fungi Sarocladium kiliense HDN11-84. Saroclazines A–B (1 and 2) possessed a free amide structure, which was first found in sulfur-containing aromatic DKPs. Their structures were elucidated by NMR, HRESIMS and X-ray. The cytotoxic activity of new compounds (13) was tested against HeLa cell lines, among which compound 2 showed an IC50 value of 4.2 µM.  相似文献   
16.
17.
18.
An accurate dosage determination is required in neonates when antibiotics are used. The adult data cannot be simply extrapolated to the pediatric population due to significant individual differences. We aimed to identify factors impacting ceftazidime exposure in neonates and to provide drug dosing guidance to clinicians. Forty-three neonates aged less than 60 days with proven or suspected infections were enrolled in this study. After intravenous administration, blood samples were collected, and plasma ceftazidime concentration was determined using a HPLC method. Pharmacokinetic data were fitted using a nonlinear mixed-effects model approach. One-compartmental model could nicely characterize the ceftazidime in vivo behavior. The covariate test found that the postmenstrual age (day) was strongly associated with systemic drug clearance (L/h), and the effect of body weight (kg) was identified as the covariate on distribution volume (L). Compared with the base model, the addition of covariates improved the goodness-of-fit of the final model. Model validation (bootstrap, visual predictive check, and prediction-corrected visual predictive check) suggested a robust and reliable pharmacokinetic model was developed. Personalized dosage regimens were provided based on model simulations. The intravenous dose should be adjusted according to postmenstrual age, body weight, and minimum inhibitory concentration.  相似文献   
19.
It is important to address the periodontitis-associated bacteria in the residual subgingival plaque after scaling and root planing to successfully treat periodontitis. In this study, we explored the possibility of exploiting the ion pairing/complexation of minocycline, Ca2+, and sulfate/sulfonate-bearing biopolymers to develop an intrapocket delivery system of minocycline as an adjunct to scaling and root planing. Minocycline-calcium-dextran sulfate complex microparticles were synthesized from minocycline, CaCl2, and dextran sulfate. They were characterized using Fourier-transform infrared spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. An in vitro release study was conducted to evaluate the release kinetics of minocycline from these microparticles. Agar disk diffusion assays and biofilm-grown bacteria assays were used to assess antibacterial capability. High loading efficiency (96.98% ± 0.12%) and high loading content (44.69% ± 0.03%) for minocycline were observed for these complex microparticles. Mino-Ca-DS microparticles achieved sustained release of minocycline for at least 9 days at pH 7.4 and 18 days at pH 6.4 in phosphate-buffered saline, respectively. They also demonstrated potent antimicrobial effects against Streptococcus mutans and Aggregatibacter actinomycetemcomitans in agar disk diffusion and biofilm assays. These results suggested that the ion pairing/complexation of minocycline, Ca2+, and sulfonate/sulfate-bearing biopolymers can be exploited to develop complex microparticles as local delivery systems for periodontitis treatment.  相似文献   
20.
Aim To investigate the effect of squalene on LDLR expression in HepG2 cells and its mechanism of down-regulated cholesterol. Methods The proliferation of HepG2 cells exposed to squalene at different concentrations was measured by MTT assay. The effect of squalene on the expression of LDLR in HepG2 cells was measured by flow cytometry and fluorescence mi-croscopy. The effect of different concentrations of squalene on the interaction between SCAP and Insig2, two key protein molecules of SREBP pathway, was assayed by FRET technology. Results MTT results showed that squalene had inhibitory effect on the proliferation of HepG2 cells in a dose-dependent manner. Flow cytometry and fluorescence microscopy results showed that squalene enhanced LDLR expression in HepG2 cells compared with the control group. The results of FRET technology revealed that compared with model control group, the YFP fluorescence value in Squalene group dramatically declined, and the YFP fluorescence value of each drug group decreased with the range of 5-25 |xmol L1 squalene concentration. Conclusions Squalene may promote the expression of LDLR in HepG2 cells through inhibiting the interaction between SCAP and Insig2 proteins in SREBP pathway, which may confirm that squalene is a potential novel drug for the down-regulation of cholesterol level. © 2018 Publication Centre of Anhui Medical University. All rights reserved.  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