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   23612篇
  免费   1287篇
  国内免费   257篇
耳鼻咽喉   472篇
儿科学   301篇
妇产科学   266篇
基础医学   4293篇
口腔科学   555篇
临床医学   1877篇
内科学   4483篇
皮肤病学   886篇
神经病学   1799篇
特种医学   1317篇
外科学   2925篇
综合类   133篇
现状与发展   1篇
一般理论   5篇
预防医学   1064篇
眼科学   448篇
药学   2078篇
中国医学   284篇
肿瘤学   1969篇
  2023年   148篇
  2022年   509篇
  2021年   810篇
  2020年   402篇
  2019年   567篇
  2018年   641篇
  2017年   527篇
  2016年   729篇
  2015年   1080篇
  2014年   1289篇
  2013年   1424篇
  2012年   2155篇
  2011年   2040篇
  2010年   1154篇
  2009年   1036篇
  2008年   1445篇
  2007年   1323篇
  2006年   1138篇
  2005年   1003篇
  2004年   862篇
  2003年   751篇
  2002年   644篇
  2001年   568篇
  2000年   469篇
  1999年   391篇
  1998年   153篇
  1997年   113篇
  1996年   83篇
  1995年   93篇
  1994年   60篇
  1993年   45篇
  1992年   142篇
  1991年   148篇
  1990年   108篇
  1989年   122篇
  1988年   101篇
  1987年   108篇
  1986年   94篇
  1985年   86篇
  1984年   63篇
  1983年   58篇
  1982年   38篇
  1981年   38篇
  1980年   30篇
  1979年   48篇
  1978年   49篇
  1977年   42篇
  1976年   32篇
  1974年   30篇
  1973年   34篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
The intestinal flora has long been thought to play a role either in initiating or in exacerbating the inflammatory bowel diseases (IBD). Host defenses, such as those mediated by the Toll-like receptors (TLR), are critical to the host/pathogen interaction and have been implicated in IBD pathophysiology. To explore the association of genetic variation in TLR pathways with susceptibility to IBD, we performed a replication study and pooled analyses of the putative IBD risk alleles in NFKB1 and TLR4, and we performed a haplotype-based screen for association to IBD in the TLR genes and a selection of their adaptor and signaling molecules. Our genotyping of 1539 cases of IBD and pooled analysis of 4805 cases of IBD validates the published association of a TLR4 allele with risk of IBD (odds ratio (OR): 1.30, 95% confidence interval (CI): 1.15-1.48; P=0.00017) and Crohn's disease (OR: 1.33, 95% CI: 1.16-1.54; P=0.000035) but not ulcerative colitis. We also describe novel suggestive evidence that TIRAP (OR: 1.16, 95% CI: 1.04-1.30; P=0.007) has a modest effect on risk of IBD. Our analysis, therefore, offers additional evidence that the TLR4 pathway - in this case, TLR4 and its signaling molecule TIRAP - plays a role in susceptibility to IBD.  相似文献   
993.
PURPOSE: This study focused on local communities and the factors influencing injuries requiring hospital admission that affect the quality of life for Koreans. MATERIALS AND METHODS: This study used data collected from 4,400 households during the 2001 Korea National Health and Nutrition Examination Survey (KNHANES). A stratified multistage probability sampling method was applied and the final sample included 7,924 subjects over 20 years old who had completed the questionnaire regarding factors influencing injuries requiring hospital admission. Multiple logistic regression analysis was used to estimate the risk factors influencing injuries. RESULTS: The incidence of injuries requiring hospital admission in Koreans was higher in men than in women at 2.3% (95% CI: 1.8-2.8) and 1.7% (95% CI: 1.3-2.1), respectively. Statistically significant factors affecting the occurrence of injuries requiring hospital admission were marital status (OR: 2.60, 95% CI: 2.22- 5.56), state of health (OR: 0.63, 95% CI: 0.43-0.92), frequency of heavy drinking (OR: 1.96, 95% CI: 1.01-3.79), normal physical activities (OR: 1.68, 95% CI: 1.07-2.65), and sleep (OR: 1.54, 95% CI: 1.01-2.35). CONCLUSION: The results of this study can be used to develop measures to prevent fatal injuries and be used as basic data for community health programs.  相似文献   
994.

Background/Aims

We compared the cirrhosis-prediction accuracy of an ultrasonographic scoring system (USSS) combining six representative sonographic indices with that of liver stiffness measurement (LSM) by transient elastography, and prospectively investigated the correlation between the USSS score and LSM in predicting cirrhosis.

Methods

Two hundred and thirty patients with chronic liver diseases (187 men, 43 women; age, 50.4±9.5 y, mean±SD) were enrolled in this prospective study. The USSS produces a combined score for nodularity of the liver surface and edge, parenchyma echogenicity, presence of right-lobe atrophy, spleen size, splenic vein diameter, and abnormality of the hepatic vein waveform. The correlations of the USSS score and LSM with that of a pathological liver biopsy (METAVIR scoring system: F0-F4) were evaluated.

Results

The mean USSS score and LSM were 7.2 and 38.0 kPa, respectively, in patients with histologically overt cirrhosis (F4, P=0.017) and 4.3 and 22.1 kPa in patients with fibrotic change without overt cirrhosis (F0-F3) (P=0.025). The areas under the receiver operating characteristic (ROC) curves of the USSS score and LSM for F4 patients were 0.849 and 0.729, respectively. On the basis of ROC curves, criteria of USSS ≥6: LSM ≥17.4 had a sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of 89.2%:77.6%, 69.4%:61.4%, 86.5%:83.7%, 74.6%:51.9% and 0.83:0.73, respectively, in predicting F4.

Conclusions

The results indicate that this USSS has comparable efficacy to LSM in the diagnosis of cirrhosis.  相似文献   
995.
Incomplete Kawasaki disease (iKD) is considered to be a less complete form of Kawasaki disease (cKD), and several differences in the laboratory presentations of iKD and cKD have been noted. We investigated serum procalcitonin levels in patients with iKD, cKD, and other febrile diseases (a control group). Seventy-seven patients with cKD, 24 with iKD, and 41 controls admitted to our hospital from November 2009 to November 2011 were enrolled in the present study. We obtained four measurements of serum procalcitonin levels and those of other inflammatory markers from each patient. Samples were taken for analysis on the day of diagnosis (thus before treatment commenced; D0) and 2 (D2), 14 (D14), and 56 days (D56) after intravenous immunoglobulin infusion. We obtained control group data at D0. The mean D0 serum procalcitonin levels of cKD patients (0.71 ± 1.36 ng/mL) and controls (0.67 ± 1.06 ng/mL) were significantly higher than those of iKD patients (0.26 ± 0.26 ng/mL) (P = 0.014 and P = 0.041, resp.). No significant difference in mean procalcitonin level was evident among groups at any subsequent time. In conclusion, the serum procalcitonin level of patients with acute-stage cKD was significantly higher than that of iKD patients.  相似文献   
996.

Purpose

Due to their comorbidities, dialysis patients have many chances to undergo radiologic procedures using iodinated contrast media. We aimed to assess time-sequenced blood oxidative stress level after contrast exposure in hemodialysis (HD) patients compared to those in the non-dialysis population.

Materials and Methods

We included 21 anuric HD patients [HD-coronary angiography (CAG) group] and 23 persons with normal renal function (nonHD-CAG group) scheduled for CAG, and assessed 4 oxidative stress markers [advanced oxidation protein products (AOPP); catalase; 8-hydroxydeoxyguanosine; and malondialdehyde] before and after CAG, and subsequently up to 28 days.

Results

In the nonHD-CAG group, only AOPP increased immediately after CAG and returned to baseline within one day. However, in the HD-CAG group, all four oxidative stress markers were significantly increased starting one day after CAG, and remained elevated longer than those in the nonHD-CAG group. Especially, AOPP level remained elevated for a month after contrast exposure.

Conclusion

Our study showed that iodinated contrast media induces severe and prolonged oxidative stress in HD patients.  相似文献   
997.
Wegener''s granulomatosis (WG) is a systemic vasculitis affecting small and medium-sized vessels with granulomatous formation. Though it is known for respiratory tract and kidney involvement, neurologic manifestation has been also reported. Herein we report a patient who suffered pansinusitis with multiple lower cranial nerve palsies but reached remission by immunosuppressant after the diagnosis of WG. A 54-yr-old female visited with headache, hearing difficulty, and progressive bulbar symptoms. She experienced endoscopic sinus surgeries due to refractory sinusitis. Neurologic examination revealed multiple lower cranial nerve palsies. Vasculitic markers showed no abnormality. Nasal biopsy revealed granulomatous inflammation and vasculitis involving small vessels. Given cyclophosphamide and prednisolone, her symptoms were prominently improved. WG should be considered in the patient with multiple cranial nerve palsies, especially those with paranasal sinus disease. Because WG can be lethal if delayed in treatment, prompt immunosuppressant is warranted after the diagnostic tissue biopsy.  相似文献   
998.
An effective paradigm for transplanting large numbers of neural stem cells after central nervous system (CNS) injury has yet to be established. Biomaterial scaffolds have shown promise in cell transplantation and in regenerative medicine, but improved scaffolds are needed. In this study we designed and optimized multifunctional and biocompatible chitosan-based films and microspheres for the delivery of neural stem cells and growth factors for CNS injuries. The chitosan microspheres were fabricated by coaxial airflow techniques, with the sphere size controlled by varying the syringe needle gauge and the airflow rate. When applying a coaxial airflow at 30 standard cubic feet per hour, ~300 μm diameter spheres were reproducibly generated that were physically stable yet susceptible to enzymatic degradation. Heparin was covalently crosslinked to the chitosan scaffolds using genipin, which bound fibroblast growth factor-2 (FGF-2) with high affinity while retaining its biological activity. At 1 μg ml?1 approximately 80% of the FGF-2 bound to the scaffold. A neural stem cell line, GFP + RG3.6 derived from embryonic rat cortex, was used to evaluate cytocompatibility, attachment and survival on the crosslinked chitosan–heparin complex surfaces. The MTT assay and microscopic analysis revealed that the scaffold containing tethered FGF-2 was superior in sustaining survival and growth of neural stem cells compared to standard culture conditions. Altogether, our results demonstrate that this multifunctional scaffold possesses good cytocompatibility and can be used as a growth factor delivery vehicle while supporting neural stem cell attachment and survival.  相似文献   
999.
For spinal-fixation applications, implants should have a high Young’s modulus to reduce springback during operations, though a low Young’s modulus is required to prevent stress shielding for patients after surgeries. In the present study, Ti–29Nb–13Ta–4.6Zr alloy (TNTZ) with a low Young’s modulus was modified by adding Cr to obtain a higher deformation-induced Young’s modulus in order to satisfy these contradictory requirements. Two newly designed alloys, TNTZ–8Ti–2Cr and TNTZ–16Ti–4Cr, possess more stable β phases than TNTZ. These alloys consist of single β phases and exhibit relatively low Young’s moduli of <65 GPa after solution treatment. However, after cold rolling, they exhibit higher Young’s moduli owing to a deformation-induced ω-phase transformation. These modified TNTZ alloys show significantly less springback than the original TNTZ alloy based on tensile and bending loading–unloading tests. Thus, the Cr-added TNTZ alloys are beneficial for spinal-fixation applications.  相似文献   
1000.

Purpose

In Korea, tree pollens are known to be prevalent in spring, grass pollens in summer and weed pollens in autumn. However, few studies have revealed their seasonal specificity for allergic rhinitis symptoms. An ARIA (Allergic Rhinitis and its Impact on Asthma) classification of allergic rhinitis was recently introduced and its clinical validation has not been well proved. The aim of this study was to evaluate the seasonal specificity of seasonal allergens and to validate the ARIA classification with the conventional seasonal and perennial allergic rhinitis (SAR/PAR) classification.

Methods

Two hundred twenty six patients with allergic rhinitis were included in this study. The patients were classified according to the sensitized allergens and the ARIA classifications. A questionnaire survey was performed and the data on the seasonal symptom score, the severity of symptoms and the SNOT (sinonasal outcome test)-20 score was obtained and the data was analyzed and compared between the conventional SAR/PAR classification and the ARIA classification.

Results

Seasonal pollens (tree, grass, weed) were not specific to the pollen peak season and the patients'' symptoms were severe during spring and autumn regardless of the offending pollens. More than 60% of the patients with SAR showed persistent symptoms and 33% of the patients with perennial allergic rhinitis (PAR) had intermittent symptoms, showing the lack of association between the SAR/PAR/PAR+SAR classification and the ARIA classification. The ARIA classification showed better association not only with the symptomatic score, but also with the SNOT-20 score, which showed better validity than the conventional SAR/PAR classifications.

Conclusions

Seasonal pollens were not specific to their season of prevalence in terms of the severity of symptoms, and the ARIA classification showed better representation of allergic symptoms and quality of life (SNOT-20 score) than did the SAR/PAR classification.  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