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   2462篇
  免费   135篇
  国内免费   11篇
耳鼻咽喉   58篇
儿科学   188篇
妇产科学   160篇
基础医学   221篇
口腔科学   174篇
临床医学   213篇
内科学   550篇
皮肤病学   32篇
神经病学   159篇
特种医学   118篇
外科学   315篇
综合类   43篇
一般理论   1篇
预防医学   73篇
眼科学   89篇
药学   131篇
中国医学   4篇
肿瘤学   79篇
  2024年   4篇
  2023年   37篇
  2022年   65篇
  2021年   114篇
  2020年   66篇
  2019年   78篇
  2018年   99篇
  2017年   82篇
  2016年   95篇
  2015年   108篇
  2014年   125篇
  2013年   153篇
  2012年   179篇
  2011年   210篇
  2010年   96篇
  2009年   85篇
  2008年   178篇
  2007年   177篇
  2006年   143篇
  2005年   144篇
  2004年   133篇
  2003年   84篇
  2002年   77篇
  2001年   25篇
  2000年   26篇
  1999年   8篇
  1998年   3篇
  1997年   3篇
  1996年   2篇
  1995年   4篇
  1994年   1篇
  1993年   2篇
  1992年   1篇
  1990年   1篇
排序方式: 共有2608条查询结果,搜索用时 296 毫秒
91.
92.
A new, fast, sensitive and simple voltammetric method is established for the direct determination of carnosic acid (CA). And the electroreduction of carnosic acid (CA) was studied using electrochemical methods. The number of electrons transferred in electrode mechanisms were calculated for reversible and adsorption-controlled electrochemical reduction of CA at 17 mV versus Ag/AgCl at pH 7.0 in Britton–Robinson buffer (BR) on a hanging mercury drop electrode. Square-wave voltammetry was developed and validated for direct determination of CA. Square-wave parameters were optimized as accumulation potential = 0.0 mV, accumulation time = 5 s, frequency = 50 Hz, pulse amplitude = 50 mV, and staircase step potential = 5 mV. The developed method displays three linear responses from 2 to 9 μM, 10 to 30 and 40 to 90 μM for carnosic acid with a correlation coefficient of 0.996, 0.999 and 0.999. The detection limits were found to be 1.5 μM, 4.0 μM and 40.1 μM, respectively. The interference effect of most common organic and inorganic species was investigated. Proposed method was successfully applied for determination of CA in natural extract of rosemary and the average content was determined as 11.9 ± 1.0 (μg CA/1 g rosemary). The results were in agreement with that obtained by HPLC-UV comparison method. The developed method can be widely used in routine quality control of herbal materials as well as other in foods, medicinal, pharmaceutical and environmental analysis.  相似文献   
93.
The hypothesis, a relationship between gingival tissue platelet activating factor (PAF) levels and healing after periodontal surgery, was tested by measuring PAF levels in gingival tissues collected from sites that had undergone flap surgery and guided tissue regeneration (GTR) or flap surgery alone. Using a split-mouth design, 20 intrabony defects were randomly assigned to treatment with flap surgery and GTR (group 1) or with flap surgery alone (group 2). Gingival tissue samples were obtained at surgery (baseline) and at 6-month follow-up evaluation visit. One half of each sample was used for analysis of PAF levels by high-performance liquid chromatography, and the other half of the sample was used for histomorphometric analysis that included measurements of number and diameter of blood vessels. PAF levels and diameter of blood vessels were significantly decreased (p < 0.01), and the number of blood vessels was significantly increased (p < 0.05) in both groups after 6 months compared to the baseline values. Postoperative number of blood vessels were significantly higher in group 1 (p < 0.05), whereas there was no significant difference in postoperative PAF levels between the two groups (p > 0.05). Based on the reported results, it is suggested that a decrease in gingival PAF levels might be found after conventional and regenerative periodontal surgery.  相似文献   
94.
Guided tissue regeneration is based on preventing the more rapidly proliferating epithelium from growing into the periodontal defect after surgical procedures incorporating barrier membranes. The aim of this study was to compare the proliferative activity of gingival epithelium using proliferating cell nuclear antigen (PCNA) as a marker of cell proliferation after surgical treatments with bioactive glass graft material and bioabsorbable membrane. Using split mouth design, 20 intrabony defects were randomly assigned treatments with bioactive glass (BG group) or bioabsorbable membrane (BM group). Gingival biopsies were taken at preoperative and postoperative 12 weeks. After histological processing, the number of the inflammatory cells was measured in hematoxylin and eosin-stained sections; PCNA expression was determined in immunohistochemically-stained sections. At postoperative 12 weeks, the number of the inflammatory cells was significantly decreased (p < 0.01), PCNA expression was significantly increased (p < 0.001) in both treatment groups compared to baseline data. There was no significant difference in PCNA expression between baseline values of two groups (p > 0.05), while at postoperative 12 weeks, increase in BG group was significantly greater than that in BM group (p < 0.001). These results suggest that epithelial cell proliferation is more prominent after treatment of intrabony defects with bioactive glass compared to the treatment with bioabsorbable membrane.  相似文献   
95.
96.
Purpose:Given the increased risk of accidents in patients with attention deficit and hyperactivity dis-order(ADHD)or maternal anxiety/depression,we aimed to investigate the frequency of the two diseases in children with penetrating eye injury(PEI).Methods:Altogether 79 children,39 with PEIs and 40 healthy individuals(control group),aged 5-15 years,underwent a complete ophthalmologic examination.Afterwards,schedule for affective disorders and schizophrenia for school-aged children was conducted to assess the psychiatric diagnosis of all children.Turgay diagnostic and statistical manual of mental disorders(DSM-Ⅳ)-based child and adolescent behavior disorders screening and rating scale(T-DSM-Ⅳ-S)was flled by parents to evaluate the severity of ADHD symptoms.The depression and anxiety levels of mothers of each group were evaluated by two self-report measures:the Beck depression scale and the state-trait anxiety inventory(STAI),respectively.Data were analyzed by IBM SPSS version 22.0.The Chi-square and Fisher's exact test were used to determine whether there is a significant difference between qualitative variables while independent sample t and Mann-Whitney U tests to compare quantitative variables.Results:The only diagnostic difference was a significantly higher frequency of ADHD among patients with PEIs(48.7%in PEI vs.17.5%in control group,χ^2=7.359,p=0.007).The total scores of the T-DSM-Ⅳ-S(attention subscale U=418.000,p=0.006;hyperactivity subscale U=472.000,p=0.022)and maternal state-trait anxiety inventory(maternal STAI-state U=243.00,p=0.003;maternal STAl-trait U=298.000,p=0.021)were significantly higher in the PEI group than in control group.In logistic regression,children with PEI had a tendency to have a 3.5-fold increased risk for ADHD(OR=3.538,CI=0.960-13.039,p=0.058).Conclusion:ADHD was detected almost 1 in 2 children with PEls.Besides,the maternal anxiety level was significantly higher in the PEI group than in the control group.This association should be further explored via a future prospective longitudinal study.Since a proper treatment of ADHD in children and anxiety treatment in mothers may prevent vision loss following PEIs in children.  相似文献   
97.
The objective of this study was to determine the optimum concentrations of rainbow trout seminal plasma (RTS) supplemented extenders for goat semen quality at post-thaw and after incubation. Five sexually mature Saanen goat (Capra aegagrus hircus) were used for semen collection. Pooled semen was diluted with soybean lecithin-based extender without RTS (control) or supplemented with different concentrations of RTS (1%, 2%, 4% or 8%), at a final concentration of 150 × 106 spermatozoon/ml. Sperm motility, plasma membrane functional integrity (HOST), damaged acrosome (PSA-FITC), mitochondrial activity (rhodamine123) and DNA integrity (TUNEL) were evaluated. Spermatological parameters were evaluated at post-thaw and after 6 hr incubation. RTS8 group preserved sperm motility, acrosomal integrity, plasma membrane functional integrity and mitochondrial function better than the control group (p < .05). The study demonstrated that RTS supplemented lecithin-based extenders have useful effects on goat spermatozoa. In addition, the results of the current study represented the positive effect of using 8% RTS supplemented extender.  相似文献   
98.
Purpose: The purpose of this study is to evaluate the management of limbal stem cell deficiency (LSCD) secondary to chemical ocular burns.

Materials and methods: The charts of 48 eyes of 40 patients with grade 2 or higher chemical injury were evaluated retrospectively. Subjects with follow-up longer than 1 year were included. Medical treatment, surgical correction of abnormalities of ocular adnexial structures, limbal stem cell transplantation from patient’s fellow eye, from living relatives or from cadaveric donor, amniotic membrane transplantation, conjunctival epitheliectomy, chelation with ethylenediaminetetraacetic acid and penetrating keratoplasty were the treatment modalities. Outcome measures were ocular surface stability and corrected distance visual acuity (CDVA). Failure was defined as the appearance of persistent epithelial defect (nonhealing epithelial defect for more than 2 weeks) with progressive corneal conjunctivalization/vascularization and thinning, and also progression of conjunctivalization to the central 6?mm of the cornea in eyes with subsequent keratoplasty.

Results: The mean age of 31 male and 9 female patients were 32.32?±?12.6 years. LSCD was bilateral in 8 cases. The mean follow-up was 77.2?±?35.1 months. The presentations were in acute phase in 37.5%, in subacute phase in 32.5% and in chronic phase in 30% of the patients. Only 13 of 48 (27.1%) eyes obtained sufficient ocular surface stability through medical treatment; however, only 5 of these eyes achieved CDVA of less than 0.7 logMAR. Limbal stem cell transplantation was performed in 26 eyes as conjunctival limbal autograft, living-related conjunctival limbal allograft and keratolimbal allograft or as a combination of these transplantations. At the last visit, 30 eyes (62.5%) had an intact and stable ocular surface. Clear cornea was achieved in 11 (78.6%) of 14 eyes with grade 2 injury, in 9 (60%) of 15 eyes with grade 3 injury, in 5 (50%) of 10 eyes with grade 4 injury, in 1 (16.6%) of 6 eyes with grade 5 injury and in 1 (33.3%) of 3 eyes with grade 6 injury. The CDVA that was 1.66?±?0.99 logMAR initially improved to 0.87?±?0.85 logMAR at the last visit (p?Conclusion: While patients with low-grade chemical injury seem to benefit quite well from the medical treatment, amniotic membrane transplantation, limbal graft transplantation and subsequent keratoplasty; patients with severe injuries seem to be more prone to failure after all of the available treatment modalities.  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