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   14505篇
  免费   1171篇
  国内免费   41篇
耳鼻咽喉   425篇
儿科学   456篇
妇产科学   401篇
基础医学   2083篇
口腔科学   326篇
临床医学   1305篇
内科学   3030篇
皮肤病学   248篇
神经病学   1707篇
特种医学   394篇
外科学   1489篇
综合类   185篇
一般理论   19篇
预防医学   1339篇
眼科学   241篇
药学   1042篇
中国医学   20篇
肿瘤学   1007篇
  2023年   108篇
  2022年   193篇
  2021年   381篇
  2020年   216篇
  2019年   338篇
  2018年   384篇
  2017年   257篇
  2016年   293篇
  2015年   380篇
  2014年   429篇
  2013年   599篇
  2012年   894篇
  2011年   902篇
  2010年   529篇
  2009年   426篇
  2008年   766篇
  2007年   722篇
  2006年   728篇
  2005年   727篇
  2004年   631篇
  2003年   595篇
  2002年   490篇
  2001年   320篇
  2000年   369篇
  1999年   314篇
  1998年   163篇
  1997年   115篇
  1996年   104篇
  1995年   104篇
  1994年   89篇
  1993年   84篇
  1992年   201篇
  1991年   167篇
  1990年   217篇
  1989年   187篇
  1988年   195篇
  1987年   189篇
  1986年   180篇
  1985年   164篇
  1984年   131篇
  1983年   114篇
  1982年   80篇
  1981年   82篇
  1980年   72篇
  1979年   106篇
  1978年   77篇
  1977年   74篇
  1975年   72篇
  1973年   69篇
  1972年   61篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Although accurate in the identification of Mycobacterium species, partial 16S rRNA gene sequencing does not distinguish Mycobacterium chelonae from M. abscessus. Thus, we designed a SmartCycler PCR assay targeting the 16S-to-23S internal transcribed spacer (ITS) region with use of MGB Eclipse probes to distinguish each species. Comparison with PCR-restriction enzyme analysis of a 441-bp fragment of the hsp65 gene resulted in 100% correlation with 25 isolates of M. chelonae and 25 isolates of M. abscessus. ITS PCR performed on 90 consecutive isolates identified by partial 16S rRNA gene sequencing (26 isolates of the M. chelonae-M. abscessus complex and 64 remaining isolates, including Mycobacterium species, Nocardia species, and other aerobic actinomycetes) showed 100% specificity and sensitivity. The ITS PCR assay is accurate and specific, easy to perform, and a good supplemental test when using partial 16S rRNA gene sequencing to identify M. chelonae and M. abscessus.  相似文献   
122.
BACKGROUND. Variation in the management of depression may be linked to doctors' attitudes to depression. AIM. A study was undertaken comparing the attitudes to depression between general practitioners and psychiatrists. METHOD. A sample of 74 general practitioners and 65 psychiatrists in Wales was surveyed by postal questionnaire. Attitudes were assessed by the depression attitude questionnaire and patient management was assessed by a questionnaire on prescribing practice. RESULTS. General practitioners differed significantly from psychiatrists in attitudes, particularly in areas covering professional ease in dealing with patients with depression and identification of depression. Those general practitioners who reported use of low antidepressant doses were significantly more likely than general practitioners prescribing standard doses to believe in psychotherapeutic treatments. Users of short-term continuation therapy expressed a lack of therapeutic optimism and comfort in dealing with depressed patients. CONCLUSION. General practitioners and psychiatrists differ significantly in their attitudes to depression. The attitudes which vary among general practitioners reflect practice. The depression attitude questionnaire may prove useful in indicating how educational initiatives to improve primary care detection and management should be directed.  相似文献   
123.
The impact of the insertion (I)/deletion (D) (I/D) polymorphism in the angiotensin 1-converting enzyme (ACE) gene on the extent of white matter myelin loss (ML) was investigated in four regions of the cerebral cortex in an autopsy-confirmed series of 93 patients with Alzheimer's disease (AD). The possible influence of APO E epsilon4 allele acting in concert with ACE D allele was assessed. The extent of ML did not differ between D/D, I/D and I/I genotype groups when data from all four brain regions were combined. However, separate analysis showed that the frontal and temporal cortex tended to be affected more severely by ML in patients with D/D genotype compared to those with I/D and I/I genotypes. Stratification according to APO E epsilon4 allele revealed a greater overall ML in patients bearing at least one copy of ACE D allele and one APO E epsilon4 allele, especially in individuals homozygous for both. The APO E epsilon4 allele may therefore act synergistically in patients with AD (and other subjects) bearing ACE D/D genotype to increase the risk of ML, perhaps through transient ischaemic episodes consequent upon poor cardiac output associated with coronary atherosclerosis in patients with the APO E epsilon4 allele.  相似文献   
124.
BACKGROUND: Subjective memory impairment (SMI) is common in older populations but its aetiology and clinical significance is uncertain. Depression has been reported to be strongly associated with SMI. Associations with objective cognitive impairment are less clear cut. Other factors suggested to be associated with SMI include poor physical health and the apolipoprotein E (APOE) epsilon4 allele. Studies of SMI have been predominantly confined to white Caucasian populations. METHOD: A community study was carried out in a UK African-Caribbean population aged 55-75, sampled from primary care lists. Twenty-three per cent were classified with SMI. Depression was defined using the 10-item Geriatric Depression Scale. Other aetiological factors investigated were education, objective cognitive function, APOE genotype, disablement and vascular disease/risk. The principal analysis was restricted to 243 participants scoring > 20 on the Mini-Mental State Examination (85%). A second analysis included all 290 participants. RESULTS: Depression, self-reported physical impairment and APOE epsilon4 were associated with SMI. The association between SMI and physical impairment was not explained by depression, vascular disease/risk, or disability/handicap. The association between epsilon4 and SMI increased as MMSE scores decreased and was particularly strong in those with depression. The epsilon4 allele was present in 69% (95% CI 41-89%) of those with depression and SMI compared with 28% (20-36%) of those with neither. CONCLUSIONS: Depression may not be a sufficient explanation for subjective memory complaints. Memory complaints in the presence of depression are associated with high prevalence of epsilon4 and therefore, presumably, a raised risk of subsequent dementia.  相似文献   
125.
We describe a rare case of malignant gastrointestinal stromal tumor (GIST) of the esophagus presenting in an HIV-positive man. Not only did the tumor arise from an unusual anatomic site for GIST, namely, the esophagus, but it also had a predominant epithelioid cell morphology that is uncommon and preferentially associated with aggressive behavior. Exhaustive immunohistochemical studies showed strong reactivities to the classic GIST marker, CD34, and to the current more sensitive and more specific GIST marker, CD117/ c-kit protein. This immunophenotype corresponded to that of stromal tumors arising in the more common sites like stomach and small intestine as well as to that of a reported series of esophageal GISTs in the general population. Mutations of the c-kit protein was detected in the tumor, confirming previous observations. This further documents that esophageal GIST and the more common benign esophageal spindle cell lesions are pathologically distinct entities and despite its rarity, esophageal GIST should be recognized by pathologists and clinicians. The occurrence of this tumor in an HIV-positive patient is coincidental, and it resulted in an extremely unusual metastatic site that has not been reported for GISTs.  相似文献   
126.
The Williams-Beuren syndrome (WBS) is a complex developmental disorder with multisystemic manifestations including supravalvular aortic stenosis (SVAS), a so-called elfin face, a hoarse voice, and a specific cognitive phenotype. Most WBS patients have a >1 Mb deletion on one of their chromosomes 7 in q11 but except for elastin, whose haploinsufficiency causes the cardiovascular malformations, it is unknown which genes in the deletion area contribute to the phenotype. We have investigated a family with a cytogenetically balanced translocation t(7;16)(q11.23;q13) in which affected individuals manifested a broad spectrum of clinical phenotypes ranging from a hoarse voice as the only feature to the full WBS phenotype. Molecular cytogenetic and DNA sequence analyses of the translocation breakpoint showed that the cytogenetic rearrangement disrupts the elastin gene locus within intron 5 in the exact same manner in all translocation carriers. The recently described large inversion of the 7q11.23 region was not present in this family. Our data demonstrate that disruption of the elastin gene by a translocation breakpoint may cause classical WBS, atypical WBS, SVAS, or no recognisable phenotype, and provide a clear example for extensive phenotypic variability associated with a position effect in humans.  相似文献   
127.
The efficacy of lodoxamide tromethamine in the treatment of asthma was studied in a 16-week double-blind, placebo-controlled study of 68 perennial allergic subjects with asthma. Patients received either lodoxamide tromethamine, 0.25 mg four times daily, or placebo, administered by metered-dose inhaler. Response to treatment was assessed by analyzing changes in asthma symptoms, inhaled bronchodilator requirements, and pulmonary function when compared to a 2-week baseline period. Patients treated with lodoxamide tromethamine demonstrated an improvement in daytime breathing difficulty, cough, sputum production, and sleep (p less than 0.01 to 0.05), but improvement was not significantly different from that demonstrated by placebo-treated patients. Patients from both treatment groups were able to reduce their inhaled bronchodilators (p less than 0.01), but again no significant difference was apparent between lodoxamide tromethamine and placebo treatment, nor were there any differences in peak expiratory flow rate or FEV1 between the two groups. Seven patients who received lodoxamide tromethamine withdrew because of a sensation of heat and gastrointestinal symptoms. Thus, although lodoxamide tromethamine possesses potent mast cell-stabilizing activity in vitro, we have failed to demonstrate any useful long-term effect in the treatment of mild allergic asthma.  相似文献   
128.
129.
Leukemic peripheral blood lymphocytes from individuals infected with the human T-cell leukemia/lymphoma virus (HTLV) were found to express little or no viral RNA before being put into tissue culture. Within 24-48 hr, viral RNA expression increased at least four- to eightfold. Established HTLV-infected cell lines constitutively express viral RNA. Southern blots of DNA from HTLV-infected cells digested with the methylation-sensitive restriction enzyme HpaII showed that the proviral DNA was methylated in all of the uncultured peripheral blood cells tested. In contrast, no proviral methylation was detected in any of the cell lines examined, suggesting a functional correlation between methylation and viral RNA expression. However, DNA from HTLV-infected lymphocytes cultured for 48 hr (by which time increases in viral RNA expression are evident) did not differ detectably with respect to proviral DNA methylation from uncultured cells, suggesting that the increase in viral RNA expression after short-term culture is mediated by mechanisms independent of changes in DNA methylation.  相似文献   
130.
A synthesis of psychological interventions for the bereaved   总被引:1,自引:0,他引:1  
Several interventions have been implemented to address the adverse psychological and physical consequences associated with bereavement. In this review, we summarize four major theories of bereavement, present a qualitative review of bereavement intervention studies, and assess the overall effectiveness of bereavement intervention studies in a quantitative meta-analysis. Summaries of the theories are drawn from published theoretical works. The qualitative and quantitative reviews were based on searches of Medline, PsychINFO, and Dissertation Abstracts International databases using the keywords "bereaved" and "bereavement." Overall, the interventions were largely methodologically flawed, rarely specified what theory of bereavement they were testing, and slowed surprisingly weak effect sizes. Possible interpretations for the small effect sizes are discussed, and future directions are outlined.  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