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   5424篇
  免费   265篇
  国内免费   25篇
耳鼻咽喉   78篇
儿科学   138篇
妇产科学   230篇
基础医学   691篇
口腔科学   289篇
临床医学   495篇
内科学   1268篇
皮肤病学   80篇
神经病学   583篇
特种医学   121篇
外科学   766篇
综合类   23篇
一般理论   1篇
预防医学   212篇
眼科学   108篇
药学   273篇
中国医学   11篇
肿瘤学   347篇
  2023年   25篇
  2022年   69篇
  2021年   124篇
  2020年   81篇
  2019年   128篇
  2018年   167篇
  2017年   121篇
  2016年   137篇
  2015年   159篇
  2014年   216篇
  2013年   286篇
  2012年   411篇
  2011年   425篇
  2010年   263篇
  2009年   219篇
  2008年   352篇
  2007年   354篇
  2006年   369篇
  2005年   297篇
  2004年   252篇
  2003年   257篇
  2002年   238篇
  2001年   73篇
  2000年   40篇
  1999年   46篇
  1998年   51篇
  1997年   56篇
  1996年   37篇
  1995年   33篇
  1994年   24篇
  1993年   25篇
  1992年   38篇
  1991年   29篇
  1990年   27篇
  1989年   30篇
  1988年   23篇
  1987年   15篇
  1986年   16篇
  1985年   15篇
  1984年   20篇
  1983年   16篇
  1982年   16篇
  1981年   13篇
  1980年   14篇
  1979年   7篇
  1978年   12篇
  1977年   11篇
  1976年   10篇
  1975年   7篇
  1974年   12篇
排序方式: 共有5714条查询结果,搜索用时 0 毫秒
91.
Background: With increase in the incidence of resistance to antibiotics, probiotics are emerging as a promising adjunctive periodontal therapy. The authors of this study evaluate the influence of probiotic (PROB) supplementation on ligature‐induced periodontitis (LIP) and intestinal morphology in rats. Methods: Thirty‐two rats were randomly divided into four groups: control (C), LIP, PROB, and LIP/PROB. In groups PROB and LIP/PROB, the PROB was administered orally by addition to the drinking water of the animals for 44 days. In groups LIP and LIP/PROB, the mandibular right first molar of the animals received a cotton ligature that was left in the same position for 14 days. All animals were euthanized 44 days after the start of the PROB supplementation. The jaws were resected and histomorphometric analyses were performed. The measurements included evaluation of attachment loss (AL) and alveolar bone level (ABL) on the distal root of the mandibular first molar. Samples of the duodenum, jejunum, and ileum were also dissected from each animal to evaluate the villous height (VH) and crypt depth (CD). The data obtained were subjected to statistical analyses (analysis of variance, Tukey; P <0.05). Results: Mean values of AL and ABL were significantly higher in group LIP compared with group LIP/PROB (AL: 3.05 ± 0.57 mm and 1.78 ± 0.63 mm, respectively; ABL: 4.21 ± 0.42 mm and 3.38 ± 0.17 mm, respectively). In group LIP/PROB, the mean values of VH and CD of the jejunum were significantly higher than the ones from group LIP (VH: 672.1 ± 83.3 µm and 528.0 ± 51.7 µm, respectively; CD: 463.8 ± 100.9 µm and 269.0 ± 48.4 µm, respectively). Conclusions: It can be concluded that PROB supplementation 1) reduces AL and alveolar bone loss in rats with LIP and 2) can protect the small intestine from reactive changes induced by LIP.  相似文献   
92.

Objective

The aim of this study is to assess whether C1772T and G1790A hypoxia-inducible factor-1 (HIF-1)α polymorphisms are associated with risk of oral lichen planus (OLP).

Material and methods

Restriction fragment length polymorphism analysis was used to investigate HIF-1α C1779T and G1790A polymorphisms in 32 OLP and 88 individuals without OLP.

Results

The frequency of the CC, TT, GA, and AA genotypes was higher in patients with OLP. Notably, individuals carrying the C and A, and T and A haplotypes showed a significant association OLP risk.

Conclusions

Our study demonstrated that the C1772T and G1790A polymorphisms of HIF-1α gene increased the risk of OLP. C1772T and G1790A polymorphisms of HIF-1α gene had differing patterns of allelic imbalance in the normal samples and subsequent chronic lesions. Further studies are necessary to elucidate the HIF-1α pathway in OLP, which would facilitate the development of novel therapeutic strategies for the prevention and treatment of OLP.

Clinical relevance

These results, in conjunction with previous studies, suggest that HIF-1α may play important roles in the chronicity of oral mucosa lesions of OLP patients. Taken together, we suggest that HIF-1α polymorphisms enhance its target genes, thereby altering the microenvironment and supporting sequential release of inflammatory mediators or cellular events in OLP. It appears unlikely that inhibition of a single proinflammatory mediator will prove useful in clinical practice, but several ways to reprogram mediators engaged in a wide array of roles simultaneously are encouraging.  相似文献   
93.

Background

We evaluated external ventricular drain placement for factors associated with placement accuracy. Data were acquired using an electronic health record data requisition tool.

Method

Medical records of all patients who underwent ventriculostomy from 2003 to 2010 were identified and evaluated. Patient demographics, diagnosis, type of guidance and number of catheter passes were searched for and recorded. Post-procedural hemorrhage and/or infection were identified. A grading scale was used to classify accuracy of catheter placements. A multiple logistic regression model was developed to assess features associated with accurate catheter placement.

Results

One hundred nine patients who underwent 111 ventriculostomies from 2003 to 2010 were identified. Patient diagnoses were classified into vascular (63 %), tumor (21 %), trauma (14 %), and cyst (2 %). Procedures were performed freehand in 90 (81 %), with the Ghajar guide in 17 (15 %), and with image guidance in 4 (4 %) patients. Eighty-eight (79 %) catheters were placed in the correct location. Trauma patients were more likely to have catheters misplaced (p?=?0.007) whereas patients in other diagnostic categories were not significantly associated with misplaced catheters. Post-procedural hemorrhage was noted in 2 (1.8 %) patients on post-procedural imaging studies. Five (4.5 %) definite and 6 (5.4 %) suspected infections were identified.

Conclusions

External ventricular drain placement can be performed accurately in most patients. Patients with trauma are more likely to have catheters misplaced. Further development is required to identify and evaluate procedure outcomes using an electronic health record repository.  相似文献   
94.
A bactericidal effect has been reported by the use of near-infrared laser light on both Gram-positive and Gram-negative bacteria. The aim of this study was to evaluate the effect of Nd:YAG laser on Actinomyces israelii, filamentous bacteria causing cervicofacial actinomycosis. Experiments were realized on bacterial cells in saline suspension or streaked on Mueller–Hinton (MH) agar plates with or without India ink. Laser application was performed in Eppendorf tubes with different powers and frequencies for 40 s; bacterial suspensions were then streaked on agar plates and incubated at 35 °C in proper conditions for 5 days before colony enumeration. A reduction of colony number variable from 60.13 to 100 % for powers of 2, 4, and 6 W at 25–50 Hz of frequency was observed in comparison with growth control. For agar plates, laser application was performed with different powers at 50 Hz for 60 s. A growth inhibition was observed after 5 days of incubation on MH plates with powers of 6 W and on MH–ink plates with all applied powers. This preliminary study showed a bactericidal effect caused by Nd:YAG laser application worthy to be evaluated in further experiments in vivo.  相似文献   
95.
96.
Human herpesvirus type 6-(HHV-6) has been associated with morbidity after liver transplantation.ObjectiveThe aim of this study was to determine the HHV-6 seroprevalence among donorrecipient pairs, analyze the incidence of early active infection, its clinical manifestation, interaction with CMV, and the related morbidity in the first year after kidney transplantation.Methods46 donor-recipient pairs had IgG evaluated by ELISA before transplantation: HHV-6-(Pambio – USA) and CMV-(Roche – USA). A frozen whole blood sample collected weekly (from the 1st to the 6th week) was retrospectively tested for HHV-6 viral load (VL) determination by real time quantitative PCR (qPCR, Nanogen – Italy). Patients were preemptively surveyed for CMV by pp65 antigenemia (Ag, APAAP, immunohistochemistry, Biotest – Germany) from the 4th to the 12th week after transplantation. Active infection was defined as qPCR-HHV6+ (viral-load/mL-VL) and Ag+ (+cells/100.000 granulocytes), for HHV-6 and CMV, respectively. DCMV was defined as simultaneous positive antigenemia and suggestive signs/symptoms. Concerning +qPCR-HHV6, associated factors, clinical manifestation, interaction with CMV and morbidity were searched.ResultsPre-transplant HHV-6 seroprevalence was significantly higher among kidney recipients compared to their donors (82.6×54.8%; p = 0.005 [3.9 (1.4–10.4)]). Active infection by this virus occurred in 26.1% (12/46), with no association with previous IgG (p = 0.412). Median VL was 125 copies/mL (53–11.264), and the median Ag was 21 +cells (2–740). There was no association between HHV-6 and CMV activation after transplantation (p = 0.441), neither concerning DCMV (p = 0.596). Median highest Ag+ and days of ganciclovir treatment were similar between qPCR-HHV6 + or ? (p = 0.206 and p = 0.124, respectively). qPCR-HHV6+ was associated with higher incidence of bacterial (p = 0.009) and fungal (p = 0.001) infections, and higher number (p = 0.001) of hospital admission and longer duration of hospitalization over the first 6 and 12 months post-transplantation (p = 0.033 and p = 0.001).ConclusionLatent HHV-6 infection is more common among recipients than donors before transplantation. Early active infection by this pathogen after transplantation does not increase DCMV incidence or severity during the first 3 months of follow-up. However, early HHV-6 replication is associated with other infections and hospitalizations in the first year.  相似文献   
97.
The efficacy of everolimus with reduced cyclosporine in de novo heart transplant patients has been demonstrated convincingly in randomized studies. Moreover, everolimus-based immunosuppression in de novo heart transplant recipients has been shown in two randomized trials to reduce the increase in maximal intimal thickness based on intravascular ultrasound, indicating attenuation of cardiac allograft vasculopathy (CAV). Randomized trials of everolimus in de novo heart transplantation have also consistently shown reduced cytomegalovirus infection versus antimetabolite therapy. In maintenance heart transplantation, conversion from calcineurin inhibitors to everolimus has demonstrated a sustained improvement in renal function. In de novo patients, a renal benefit may only be achieved if there is an adequate reduction in exposure to calcineurin inhibitor therapy. Delayed introduction of everolimus may be appropriate in patients at high risk of wound healing complications, e.g. diabetic patients or patients with ventricular assist device. The current evidence base suggests that the most convincing reasons for use of everolimus from the time of heart transplantation are to slow the progression of CAV and to lower the risk of cytomegalovirus infection. A regimen of everolimus with reduced-exposure calcineurin inhibitor and steroids in de novo heart transplant patients represents a welcome addition to the therapeutic armamentarium.  相似文献   
98.
99.
ObjectivesConsidering the enamel chemical structure, especially carbonate band, which has a major role in the caries prevention, the objective of the present study was to assess the chemical alterations on the enamel irradiated with CO2 laser by means of FTIR spectroscopy and SEM analysis.DesignThe enamel surfaces were analysed on a spectrometer for acquisition of the absorption spectrum relative to the chemical composition of the control sample. The irradiation was conducted with a 10.6-μm CO2 laser (0.55 W, 660 W/cm2). The carbonate absorption band at 1600–1291 cm?1 as well as the water absorption band at 3793–2652 cm?1 was measured in each sample after the irradiation. The water band was measured again 24-h after the irradiation. The band area of each chemical compound was delimited, the background was subtracted, and the area under each band was integrated. Each area was normalized by the phosphate band (1190–702 cm?1).ResultsThere was a statistically significant decrease (p < 0.05) in the water content after irradiation (control: 0.184 ± 0.04; irradiated: 0.078 ± 0.026), which increased again after rehydration (0.145 ± 0.038). The carbonate/phosphate ratio was measured initially (0.112 ± 0.029) and its reduction after irradiation indicated the carbonate loss (0.088 ± 0.014) (p < 0.05).ConclusionThe 10.6-μm CO2 laser irradiation diminishes the carbonate and water contents in the enamel after irradiation.  相似文献   
100.
We examined the hypothesis that predictive gaze during observation of other people's actions depends on the activation of corresponding action plans in the observer. Using transcranial magnetic stimulation and eye-tracking technology we found that stimulation of the motor hand area, but not of the leg area, slowed gaze predictive behavior (compared to no TMS). This result shows that predictive eye movements to others' action goals depend on a somatotopical recruitment of the observer's motor system. The study provides direct support for the view that a direct matching process implemented in the mirror-neuron system plays a functional role for real-time goal prediction.  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