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   26705篇
  免费   1350篇
  国内免费   154篇
耳鼻咽喉   274篇
儿科学   559篇
妇产科学   623篇
基础医学   3404篇
口腔科学   1040篇
临床医学   1946篇
内科学   7176篇
皮肤病学   697篇
神经病学   2007篇
特种医学   496篇
外科学   4353篇
综合类   174篇
一般理论   3篇
预防医学   1935篇
眼科学   446篇
药学   1466篇
中国医学   122篇
肿瘤学   1488篇
  2023年   208篇
  2022年   436篇
  2021年   955篇
  2020年   439篇
  2019年   889篇
  2018年   1029篇
  2017年   575篇
  2016年   588篇
  2015年   752篇
  2014年   1098篇
  2013年   1381篇
  2012年   2184篇
  2011年   2239篇
  2010年   1317篇
  2009年   1142篇
  2008年   1806篇
  2007年   1863篇
  2006年   1716篇
  2005年   1530篇
  2004年   1412篇
  2003年   1346篇
  2002年   1239篇
  2001年   158篇
  2000年   130篇
  1999年   168篇
  1998年   192篇
  1997年   146篇
  1996年   145篇
  1995年   124篇
  1994年   99篇
  1993年   83篇
  1992年   75篇
  1991年   53篇
  1990年   50篇
  1989年   37篇
  1988年   43篇
  1987年   35篇
  1986年   20篇
  1985年   38篇
  1984年   36篇
  1983年   40篇
  1982年   47篇
  1981年   45篇
  1980年   44篇
  1979年   18篇
  1978年   24篇
  1977年   26篇
  1975年   22篇
  1974年   21篇
  1973年   18篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Objective. The analysis of genetic markers of rheumatoid arthritis (RA) in a population in which the DR4 serotype is not strongly associated with the disease. Methods. Chilean RA patients (56 seropositive and 22 seronegative) and 141 controls were studied by serotyping. Southern blot analysis of Bam HI restriction fragment length polymorphism (RFLP) was done in genomic DNA from 46 patients with seropositive RA, 17 patients with seronegative RA, and 45 controls, using a complementary DNA probe specific for DRB1 genes. Results. The prevalence of the HLA—DR9 haplotype was strikingly higher in seropositive RA patients (21%) than in controls (3%) (Pcorr < 0.0008, by Fisher's exact test; relative risk [RR] = 9.34). The prevalence of DR4 and DR1 haplotypes, although slightly increased, did not achieve a significant preponderance. The simultaneous presence of two Bam HI fragments (3.6 kb and 4.5 kb) was found with higher prevalence in seropositive patients (83%; RR = 9; Pcorr < 0.00002) than in controls (36%), and seemed higher in seronegative RA patients as well (71%; RR = 4). Furthermore, its prevalence remained increased in comparisons of DR4 positive controls (36%) with DR4 positive seropositive patients (100%; RR = 67; Pcorr < 0.0002) and DR4 positive seronegative patients (100%; RR = 36; Pcorr < 0.006), even after excluding the DR9 positive individuals. A tendency toward higher association with DR1 seropositive RA patients (67%; RR = 12), a group with no DR4 or DR9 positive individuals, than in DR1 positive controls (14%), was also observed. Conclusion. The HLA—DR9 haplotype was definitively consolidated as a very strong genetic marker exclusively for seropositive RA in Chilean patients, as suggested by our previous observations. RFLP analysis showed that the simultaneous presence of 3.6-kb and 4.5-kb Bam HI fragments constituted a better RA marker than did any of the heretofore studied haplotypes. These fragments together would be linked to RA independently of the DR1, DR4, and DR9 haplotypes. The overall evidence indicates that Chilean seropositive RA patients display a genetic background that is different from that underlying RA susceptibility in other populations and suggests the existence of common, as well as distinct, genetic elements predisposing to seronegative and seropositive RA.  相似文献   
992.
Open in a separate windowOBJECTIVESProlonged air leak (PAL; >5 days) following lung resection is associated with postoperative morbidity. We investigated factors associated with PAL and PAL requiring intervention.METHODSRetrospective review of all patients undergoing lobectomy, segmentectomy or wedge resection from 2016 to 2019 at our institution. Bronchoplastic reconstructions and lung-volume reduction surgeries were excluded. Incidence and risk factors for PAL and PAL requiring intervention were evaluated.RESULTSIn total, 2384 patients were included. PAL incidence was 5.4% (129/2384); 22.5% (29/129) required intervention. PAL patients were more commonly male (56.6% vs 39.7%), older (mean age 69 vs 65 years) and underwent lobectomy or thoracotomy (all P < 0.001). Patients with PAL had longer length of stay (9 vs 3 days), more discharge needs and increased odds of complication (all P < 0.050).Twenty-nine patients required intervention (9 chest tubes; 4 percutaneous drains; 16 operations). In 50% of operative interventions, an air leak source was identified; however, the median time from intervention to resolution was 13 days. Patients requiring intervention had increased steroid use, lower diffusion capacity for carbon monoxide and twice the length of stay versus PAL patients (all P < 0.050).On univariable analysis, forced expiratory volume in 1 s (FEV1) <40%, diffusion capacity for carbon monoxide <50%, steroid use and albumin <3 had increased odds of intervention (P < 0.050).CONCLUSIONSAge, gender and operative technique were related to PAL development. Patients with worse forced expiratory volume in 1 s or diffusion capacity for carbon monoxide, steroid use or poor nutrition were less likely to heal on their own, indicating a population that could benefit from earlier intervention.  相似文献   
993.
Candidate gene studies have analyzed the effect of specific vitamin D pathway genes on vitamin D availability; however, it is not clear whether genetic variants also affect overall bone metabolism. This study evaluated the association between genetic polymorphisms in GC, CYP2R1 and CYP24A1 and serum levels of total 25(OH)D, iPTH and other mineral metabolism biomarkers (albumin, total calcium and phosphorus) in a sample of 273 older Spanish adults. We observed a significant difference between CYP2R1 rs10741657 codominant model and total 25(OH)D levels after adjusting them by gender (p = 0.024). In addition, the two SNPs in the GC gene (rs4588 and rs2282679) were identified significantly associated with iPTH and creatinine serum levels. In the case of phosphorus, we observed an association with GC SNPs in dominant model. We found a relationship between haplotype 2 and 25(OH)D levels, haplotype 4 and iPTH serum levels and haplotype 7 and phosphorus levels. In conclusion, genetic variants in CYP2R1 and GC could be predictive of 25(OH)D and iPTH serum levels, respectively, in older Caucasian adults. The current study confirmed the role of iPTH as one of the most sensitive biomarkers of vitamin D activity in vivo.  相似文献   
994.
Recurrent respiratory papillomatosis can be a devastating condition for a child, with severe consequences. Currently, there is no proven successful medical treatment. We describe the use of systemic bevacizumab to treat two children affected by aggressive recurrent respiratory papillomatosis. Respiratory symptoms and quality of life improved dramatically in both patients, without observing any toxicity. The only complication was mild proteinuria. Systemic bevacizumab is a promising adjuvant treatment in aggressive recurrent respiratory papillomatosis in children. It is effective and well tolerated. Further studies are needed to establish the optimal dosing frequency and duration of therapy. Laryngoscope, 129:1001–1004, 2019  相似文献   
995.
996.
Introduction and objectivesInadequate auditory feedback in prelingually deaf children alters the articulation of consonants and vowels.The purpose of this investigation was to compare vowel production in Spanish-speaking deaf children with cochlear implantation, and with hearing-aids with normal-hearing children by means of acoustic analysis of formant frequencies and vowel space.MethodsA total of 56 prelingually deaf children (25 with cochlear implants and 31 wearing hearing-aids) and 47 normal-hearing children participated. The first 2 formants (F1 and F2) of the five Spanish vowels were measured using Praat software. One-way analysis of variance (ANOVA) and post hoc Scheffé test were applied to analyze the differences between the 3 groups. The surface area of the vowel space was also calculated.ResultsThe mean value of F1 in all vowels was not significantly different between the 3 groups. For vowels /i/, /o/ and /u/, the mean value of F2 was significantly different between the 2 groups of deaf children and their normal-hearing peers.ConclusionBoth prelingually hearing-impaired groups tended toward subtle deviations in the articulation of vowels that could be analyzed using an objective acoustic analysis programme.  相似文献   
997.
Introduction and objectivesPerceptual rating of overall voice quality and other more specific perceptual dimensions is difficult, as such judgments depend on the listener's subjectivity. Thus, finding objective, valid, and accessible clinical measures to include in comprehensive voice evaluation protocols is a priority.The purposes of this study were to 1) determine the diagnostic accuracy of a single acoustic measure, smoothed cepstral peak prominence (CPPS), to predict voice disorder status from sustained vowels and connected speech samples using the software Praat; 2) to determine the relationship between measures of CPPS and perceptual ratings of vocal quality; and 3) describe the normative values of CPPS.MethodMeasures of CPPS were obtained from connected speech and sustained vowel recordings of 72 Spanish-speaking subjects with voice disorders and 52 nondysphonic Spanish-speaking subjects with no vocal disorders using freely downloadable Praat software. IBM SPSS Statistics software version 23 was used to complete the statistical analyses.Resultsresults revealed a 70% sensitivity rate, a specificity rate of 85%. Estimated severity for sustained vowels and connected speech were strongly correlated and significantly associated with listener ratings of dysphonia severity.ConclusionsA single acoustic measure of CPPS was highly predictive of voice disorder status using Praat software. Clinicians may consider using CPPS to complement clinical voice evaluation and screening protocols.  相似文献   
998.
999.
1000.
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