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   4731篇
  免费   246篇
  国内免费   187篇
耳鼻咽喉   68篇
儿科学   90篇
妇产科学   95篇
基础医学   637篇
口腔科学   112篇
临床医学   502篇
内科学   804篇
皮肤病学   155篇
神经病学   325篇
特种医学   279篇
外科学   590篇
综合类   66篇
一般理论   3篇
预防医学   248篇
眼科学   70篇
药学   637篇
中国医学   113篇
肿瘤学   370篇
  2023年   33篇
  2022年   115篇
  2021年   190篇
  2020年   93篇
  2019年   120篇
  2018年   147篇
  2017年   110篇
  2016年   143篇
  2015年   201篇
  2014年   262篇
  2013年   290篇
  2012年   391篇
  2011年   408篇
  2010年   235篇
  2009年   178篇
  2008年   271篇
  2007年   338篇
  2006年   234篇
  2005年   204篇
  2004年   167篇
  2003年   141篇
  2002年   110篇
  2001年   113篇
  2000年   81篇
  1999年   90篇
  1998年   48篇
  1997年   33篇
  1996年   34篇
  1995年   23篇
  1994年   16篇
  1993年   15篇
  1992年   35篇
  1991年   39篇
  1990年   27篇
  1989年   37篇
  1988年   21篇
  1987年   20篇
  1986年   14篇
  1985年   17篇
  1984年   6篇
  1983年   10篇
  1979年   6篇
  1978年   8篇
  1976年   7篇
  1974年   8篇
  1972年   5篇
  1971年   8篇
  1969年   6篇
  1968年   14篇
  1967年   5篇
排序方式: 共有5164条查询结果,搜索用时 15 毫秒
61.
Angiogenesis is an essential process in the development, growth, and metastasis of malignant tumors including lung cancer. DNA sequence variations in the vascular endothelial growth factor (VEGF) gene may lead to altered VEGF production and/or activity, thereby causing interindividual differences in the susceptibility to lung cancer via their actions on the pathways of tumor angiogenesis. To test this hypothesis, we investigated the potential association between three VEGF polymorphisms (-460T > C, +405C > G, and 936C > T)/haplotypes and the risk of lung cancer in a Korean population. VEGF genotypes were determined in 432 lung cancer patients and 432 healthy controls that were frequency matched for age and sex. VEGF haplotypes were predicted using Bayesian algorithm in the phase program. Compared with the combined +405 CC and CG genotype, the +405 GG genotype found associated with a significantly decreased risk of small cell carcinoma [SCC; adjusted odds ratio (OR), 0.36; 95% confidence interval (95% CI), 0.17-0.78]. The 936 CT genotype and the combined 936 CT and TT genotype were also associated with a significantly decreased risk of SCC compared with the 936 CC genotype (adjusted OR, 0.47; 95% CI, 0.26-0.85 and adjusted OR, 0.44; 95% CI, 0.24-0.80, respectively). Haplotype CGT was associated with a significantly decreased risk of SCC (adjusted OR, 0.39; 95% CI, 0.18-0.87), whereas haplotype TCC conferred a significantly increased risk of SCC (adjusted OR, 1.63; 95% CI, 1.14-2.33). None of the VEGF polymorphisms studied significantly influenced the susceptibility to lung cancer except SCC. However, haplotypes TCT and TGT were significantly associated with the risk of overall lung cancer, respectively (adjusted OR, 0.38; 95% CI, 0.25-0.60 and adjusted OR, 3.94; 95% CI, 2.00-7.76, respectively). These effects of haplotypes TCT and TGT on lung cancer risk were observed in three major histologic types of lung cancer. These results suggest that the VEGF gene may be contribute to an inherited predisposition to lung cancer.  相似文献   
62.
63.
Gut microbiota dysbiosis is strongly associated with psychiatric disorders and inflammatory bowel disease (IBD). Herein, we examined whether the fecal microbiota of IBD patients with depression (IBDD) and their gut microbiota culture (iGm) could cause depression and colitis in mice and anti-inflammatory probiotics could mitigate depression in iGm-transplanted or immobilization stress (IS)-exposed mice. Fecal microbiota transplantation (FMT) from IBDD patients, which exhibited Enterobacteriaceae-rich gut microbiota, and its gut microbiota culture (iGm) increased depression-like behaviors in mice. Their treatments heightened the blood lipopolysaccharide (LPS) level and colonic IL-1β and IL-6 expression. However, FMT from healthy volunteers or sulfasalazine treatment alleviated cGm-induced depressive-like behaviors and hippocampal and colonic inflammation in mice. Moreover, oral administration of Lactobacillus plantarum NK151, Bifidobacterium longum NK173, and Bifidobacterium bifidum NK175, which inhibited LPS-induced IL-6 expression in macrophages, alleviated cGm-induced depression-like behaviors, hippocampal NF-κB+Iba1+ cell numbers and IL-1β and IL-6 expression, blood LPS, IL-6, and creatinine levels, and colonic NF-κB+CD11c+ number and IL-1β and IL-6 expression in mice. Treatment with NK151, NK173, or NK175 mitigated immobilization stress (IS)-induced depressive-like behaviors, neuroinflammation, and gut inflammation in mice. NK151, NK173, or NK175 also decreased IS-induced blood LPS, IL-6, and creatinine levels. The transplantation of Enterobacteriaceae-rich gut microbiota can cause depression and colitis, as IS exposure, and anti-inflammatory NK151, NK173, and NK175, may alleviate stress-induced fatigue, depression, and colitis by regulating the expression of proinflammatory and anti-inflammatory cytokines through the suppression of gut bacterial LPS.  相似文献   
64.

Ethnopharmacological relevance

Clematis mandshurica Ruprecht root is widely used in Asia as an analgesic and anti-inflammatory agent. This research investigated the anti-inflammatory effects of Clematis mandshurica Ruprecht root extract (CRE) using RAW 264.7 macrophage cells and carrageenan- (CA-) induced rat paw edema.

Materials and methods

Production of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, IL-6, nitric oxide (NO) and prostaglandin E2 (PGE2) in the culture supernatant, mRNA expression of TNF-α, IL-1β, IL-6, iNOS and COX-2, protein expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), nuclear factor-kappa B (NF-κB) and mitogen-activated protein kinases (MAPKs) in the extract were assayed. In addition, the effect of CRE on acute inflammation in vivo was observed using CA-induced rat hind paw edema assay. The changes on the histopathology and histomorphometry of hind paw skins—dorsum and ventrum pedis were observed using CA-treated rats.

Results

Treatment with CRE (0.25, 0.5, and 1 mg/mL) resulted in inhibited levels of protein expression of lipopolysaccharide- (LPS-) induced iNOS, COX-2, NF-κB, and MAPKs (ERK, JNK, and p38) as well as production of TNF-α, IL-1β, IL-6, NO, and PGE2 induced by LPS. Consistent with these results, CRE reduced the LPS-induced expressions of these cytokines, iNOS and COX-2 at the mRNA levels in a dose-dependent manner. In particular, results of the CA-induced rat hind paw edema assay showed an anti-edema effect of CRE. In addition, treatment with CRE resulted in dose-dependent inhibition of CA-induced increases of skin thickness, mast cell degranulation, and infiltrated inflammatory, TNF-α, IL-1β, iNOS, and COX-2-positive cells in both dorsum and ventrum pedis skin, respectively.

Conclusions

These results demonstrate that CRE exhibits anti-inflammatory activities via decreasing production of pro-inflammatory mediators through suppression of the pathways of NF-κB and MAPKs in LPS-induced macrophage cells. In addition, results of the CA-induced rat hind paw edema assay show an anti-edema effect of CRE. Our findings also support the traditional use of CRE in the inflammatory symptoms of rheumatic arthritis and acute icteric hepatitis. Thus, CRE may have therapeutic potential for a variety of inflammation-mediated diseases and may be developed into potent anti-inflammatory drugs.  相似文献   
65.

Study Objective

To assess clinical pregnancy rate (CPR) and live birth rate (LBR) in the presence of non–cavity-deforming intramural myomas in single fresh blastocyst transfer cycles.

Design

Retrospective cohort study (Canadian Task Force classification II-2).

Setting

Academic fertility center.

Patients

A total of 929 fresh single blastocyst transfer cycles were included, 94 with only non–cavity-distorting intramural myomas and 764 without myomas. Cleavage embryo transfers were excluded to reduce bias based on embryo quality.

Interventions

None.

Measurements and Main Results

CPR and LBR were assessed. There were no differences noted in gravidity, parity, or body mass index between patients with myomas and those without myomas. Women with myomas required higher doses of gonadotropins (mean, 2653?±?404?IU vs 2350?±?1368?IU; p?=?.04) than women without myomas. However, the total number of mature oocytes collected and the total number of blastocysts created were similar. CPR (47% vs 32%; p?=?.005) and LBR (37.8% vs 25.5%; p?=?.02) were lower in patients who had intramural myomas compared with those without myomas. CPR and LBR were significantly reduced in the presence of even 1 myoma (odds ratio [OR], 0.53; 95% confidence interval [CI], 0.33–0.83 and OR, 0.56; 95% CI, 0.35–0.92, respectively). In patients with myomas >1.5?cm, LBR was also significantly reduced, even after adjusting for age, smoking, quality of embryo transferred, antral follicle count, and dose of gonadotropins (OR, 0.53; 95% CI, 0.29–0.97). This LBR finding was not significant if all myomas were included (including those <1.5?cm in diameter), but CPR was still significantly reduced.

Conclusion

Relatively small (>1.5?cm) non–cavity-distorting intramural myomas negatively affect CPR and LBR in in vitro fertilization cycles, even in the presence of only 1 myoma.  相似文献   
66.
Background/AimsWe examined the efficacy and safety of tegoprazan as a part of first-line triple therapy for Helicobacter pylori eradication.MethodsA randomized, double-blind, controlled, multicenter study was performed to evaluate whether tegoprazan (50 mg)-based triple therapy (TPZ) was noninferior to lansoprazole (30 mg)-based triple therapy (LPZ) (with amoxicillin 1 g and clarithromycin 500 mg; all administered twice daily for 7 days) for treating H. pylori. The primary endpoint was the H. pylori eradication rate. Subgroup analyses were performed according to the cytochrome P450 (CYP) 2C19 genotype, the minimum inhibitory concentration (MIC) of amoxicillin and clarithromycin, and underlying gastric diseases.ResultsIn total, 350 H. pylori-positive patients were randomly allocated to the TPZ or LPZ group. The H. pylori eradication rates in the TPZ and LPZ groups were 62.86% (110/175) and 60.57% (106/175) in an intention-to-treat analysis and 69.33% (104/150) and 67.33% (101/150) in a per-protocol analysis (non-inferiority test, p=0.009 and p=0.013), respectively. Subgroup analyses according to MICs or CYP2C19 did not show remarkable differences in eradication rate. Both first-line triple therapies were well-tolerated with no notable differences.ConclusionsTPZ is as effective as proton pump inhibitor-based triple therapy and is as safe as first-line H. pylori eradication therapy but does not overcome the clarithromycin resistance of H. pylori in Korea (ClinicalTrials.gov identifier NCT03317223).  相似文献   
67.
ObjectiveAlthough full-endoscopic lumbar interbody fusion (Endo-LIF) has been tried as the latest alternative technique to minimally invasive transforaminal lumbar interobody fusion (MIS-TLIF) since mid-2010, the evidence is still lacking. We compared the clinical outcome and safety of Endo-LIF to MIS-TLIF for lumbar degenerative disease. MethodsWe systematically searched electronic databases, including PubMed, EMBASE, and Cochrane Library to find literature comparing Endo-LIF to MIS-TLIF. The results retrieved were last updated on December 11, 2020. The perioperative outcome included the operation time, blood loss, complication, and hospital stay. The clinical outcomes included Visual analog scale (VAS) of low back pain and leg pain and Oswestry disability index (ODI), and the radiological outcome included pseudoarthosis rate with 12-month minimum follow-up. ResultsFour retrospective observational studies and one prospective observational study comprising 423 patients (183 Endo-LIF and 241 MIS-TLIF) were included, and the pooled data analysis revealed low heterogeneity between studies in our review. Baseline characteristics including age and sex were not different between the two groups. Operation time was significantly longer in Endo-LIF (mean difference [MD], 23.220 minutes; 95% confidence interval [CI], 10.669–35.771; p=0.001). However, Endo-LIF resulted in less perioperative blood loss (MD, -144.710 mL; 95% CI, 247.941–41.478; p=0.023). Although VAS back pain at final (MD, -0.120; p=0.586), leg pain within 2 weeks (MD, 0.005; p=0.293), VAS leg pain at final (MD, 0.099; p=0.099), ODI at final (MD, 0.141; p=0.093) were not different, VAS back pain within 2 weeks was more favorable in the Endo-LIF (MD, -1.538; 95% CI, -2.044 to -1.032; p<0.001). On the other hand, no statistically significant group difference in complication rate (relative risk [RR], 0.709; p=0.774), hospital stay (MD, -2.399; p=0.151), and pseudoarthrosis rate (RR, 1.284; p=0.736) were found. ConclusionRelative to MIS-TLIF, immediate outcomes were favorable in Endo-LIF in terms of blood loss and immediate VAS back pain, although complication rate, mid-term clinical outcomes, and fusion rate were not different. However, the challenges for Endo-LIF include longer operation time which means a difficult learning curve and limited surgical indication which means patient selection bias. Larger-scale, well-designed study with long-term follow-up and randomized controlled trials are needed to confirm and update the results of this systematic review.  相似文献   
68.
A rotating body consisting of a rotating shaft and bearings inevitably generates voltage and current. The potential difference between the bearing and the shaft is the main cause of electrical corrosion, which causes motor failure, shortened bearing life, and many safety issues. To prevent corrosion, passive shaft-grounding devices use conductive materials and brushes; however, these devices cannot be completely grounded, so there is a difference in local potential, and brush friction generates a shaft current. The cumulative effect causes electrical corrosion; therefore, in this study, an electrical corrosion protection device for the rotating power supply shaft was developed. It detected current and potential difference and established a feedback system on the rotating shaft. It also energized the rotating shaft using an external power supply to eliminate the potential difference on the shaft and reduce electrical corrosion. The result was prolonged motor life and improved stability, operating efficiency, and operability of related equipment. In this study, a rotating-shaft test rig was set up, and a constant current was applied to simulate the potential difference and verify the performance of the anti-corrosion device. Gradually, the design scheme was optimized; the potential difference on the rotating shaft was accurately quantified; and the goal of controlling the potential difference within 2 mV was achieved. Finally, the electrical corrosion protection device was applied to the rotating shaft of a merchant ship, and the current and potential difference on the rotating shaft were monitored for 30 days. The results showed that the device had excellent performance in reducing the potential difference on the rotating shaft and preventing electrical corrosion.  相似文献   
69.
The mechanisms of cadmium-induced toxicity may include oxidative stress, altered redox homeostasis, and injuries to organelles. The current study was designed to study the effect of decreased cellular glutathione (GSH) content by sulfur amino acid deprivation on cadmium toxicity and to identify the signaling pathways responsible for the cytotoxicity. GSH content was increased by cadmium in H4IIE cells prior to cell death, which was prevented by excess GSH or cysteine. Cell viability, however, was not improved by GSH or cysteine complexation of cadmium. Cadmium-induced cytotoxicity was 40-fold potentiated in cells with decreased GSH by sulfur amino acid deprivation. Cadmium in combination with decreased GSH markedly increased apoptotic cell death. Mitogen-activated protein kinases including extracellular signal-regulated kinase 1/2, p38 kinase and c-Jun N-terminal kinase (JNK) were all activated 1-12 hr after sulfur amino acid deprivation. U0126 (1,4-diamino-2,3-dicyano-1,4-bis[2-aminophenylthio]butadiene), which inhibited activation of extracellular signal-regulated kinase1/2 and p38 kinase in cells under sulfur amino acid deprivation, completely prevented potentiation in Cd-induced cytotoxicity and apoptosis. Potentiation of cadmium toxicity by sulfur amino acid deprivation was prevented in part by either PD98059 or SB203580, or in cells stably expressing dominant negative mutant of JNK1, and to greater extents by PD98059 in combination with either SB203580 or JNK1(-) transfection. These results demonstrated that decreased cellular GSH content potentiated cytotoxicity induced by cadmium at the level of human exposure, and that the potentiation of cytotoxicity resulted from activation of extracellular signal-regulated kinase1/2 in conjunction with p38 kinase or JNK.  相似文献   
70.
Voice outcomes of polyacrylamide hydrogel injection laryngoplasty   总被引:1,自引:0,他引:1  
Lee SW  Son YI  Kim CH  Lee JY  Kim SC  Koh YW 《The Laryngoscope》2007,117(10):1871-1875
OBJECTIVES: Polyacrylamide hydrogel (PAAG, Aquamid) is widely used as permanent facial tissue filler during facial plastic surgery. In this study, we examined the long-term effects and safety aspects of PAAG as a vocal fold augmentation material for patients with permanent unilateral vocal cord paralysis. STUDY DESIGN: Prospective clinical trials. METHODS: PAAG injection laryngoplasty was performed in 34 consecutive patients with permanent unilateral vocal cord paralysis. Percutaneous injection was performed under local anesthesia into the vocalis muscle using disposable 25 gauge long needles. Of the 34 patients, 16 completed acoustic, perceptual, stroboscopic, and subjective evaluations prior to the injection and at 6 and 12 months after the injection. RESULTS: Acoustic and perceptual parameters (GRBAS [Overall grade of dysphonia, Roughness, Breathiness, Aesthenia, Strain], Maximal phonation time [MPT], jitter, and shimmer) were significantly improved (P < .05) after injection and remained stable over 12 months. The grades of mucosal waves and glottic closure were also significantly improved (P < .01). The voice handicap index (VHI), as well as the visual analogue scale (VAS) of hoarseness and aspiration significantly improved over 12 months. No adverse effects were observed except for a decrease in the mucosal wave of one patient, after injection into a superficial area of the vocal fold. CONCLUSION: Based on the preliminary results of this trial, PAAG appears to be a long-lasting and safe injection material that is suitable for the treatment of glottal insufficiency caused by permanent unilateral vocal cord paralysis.  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