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   2822篇
  免费   209篇
  国内免费   3篇
耳鼻咽喉   7篇
儿科学   85篇
妇产科学   76篇
基础医学   503篇
口腔科学   42篇
临床医学   277篇
内科学   462篇
皮肤病学   38篇
神经病学   260篇
特种医学   104篇
外科学   284篇
综合类   79篇
一般理论   1篇
预防医学   300篇
眼科学   66篇
药学   211篇
肿瘤学   239篇
  2023年   19篇
  2022年   37篇
  2021年   75篇
  2020年   50篇
  2019年   48篇
  2018年   77篇
  2017年   57篇
  2016年   60篇
  2015年   90篇
  2014年   99篇
  2013年   113篇
  2012年   186篇
  2011年   205篇
  2010年   126篇
  2009年   113篇
  2008年   166篇
  2007年   162篇
  2006年   147篇
  2005年   147篇
  2004年   135篇
  2003年   125篇
  2002年   105篇
  2001年   43篇
  2000年   34篇
  1999年   37篇
  1998年   31篇
  1997年   20篇
  1996年   24篇
  1995年   28篇
  1994年   17篇
  1993年   20篇
  1992年   43篇
  1991年   27篇
  1990年   19篇
  1989年   21篇
  1988年   22篇
  1987年   22篇
  1986年   16篇
  1985年   19篇
  1984年   24篇
  1983年   12篇
  1982年   11篇
  1980年   12篇
  1979年   13篇
  1977年   14篇
  1976年   15篇
  1975年   9篇
  1973年   12篇
  1969年   9篇
  1966年   9篇
排序方式: 共有3034条查询结果,搜索用时 18 毫秒
71.
Between 1963 and 1980, one or more posterior-lateral foraminotomies were performed for simple cervical radiculopathy as the sole operative procedure for 736 patients. One hundred three patients (14%) required a second posterior procedure, but only 24 (3%) cases represented true recurrent radiculopathy. There were 13 minor complications (1.5%) and no deaths or detectable incidence of air embolism. All operations were done with the patient in the sitting position. Central venous pressure monitoring was used only infrequently. There was a 96% incidence of relief of significant arm pain and/or paresthesia and a 98% incidence of resolution of preoperatively present motor deficit. Eight hundred twenty-eight procedures (98%) were preceded by Pantopaque cervical myelography. There was a 71.5% incidence of correlation between preoperative clinical findings (both sensory and motor) and operative findings. In 13% of the cases, two spaces were thought by the operating surgeon to be equally involved by the spondylotic process. Most (91.5%) of the patients describe themselves as either "good or excellent" postoperatively. There was no significant difference postoperatively regarding results or recurrence between patients with suspected soft or hard disc protrusions and those with strictly spondylotic radiculopathy. Nor was there any statistical difference in results among the three patient population groups ("private" vs. compensation vs. liability). The mean length of time to return to work or other "normal" activities was 9.4 weeks. The mean length of follow-up time was 146 weeks (2.8 years). There was an associated incidence of significant lumbar disc and/or foraminal disease requiring operation of 33.4%.  相似文献   
72.
73.
正To the editor:We read with great interest the article entitled Comparative study of the effects of terlipressin versus splenectomy on liver regeneration after partial hepatectomy in rats by Ulmer et al.[1].The aim of this study was to analyse the impact of terlipressin ver-  相似文献   
74.
Sleep problems increase with ageing. Increasing evidence suggests that sleep problems are not only a consequence of age‐related processes, but may independently contribute to developing vascular or neurodegenerative brain disease. Yet, it remains unclear what mechanisms underlie the impact sleep problems may have on brain health in the general middle‐aged and elderly population. Here, we studied sleep's relation to brain functioning in 621 participants (median age 62 years, 55% women) from the population‐based Rotterdam Study. We investigated cross‐sectional associations of polysomnographic and subjectively measured aspects of sleep with intrinsic neural activity measured with resting‐state functional magnetic resonance imaging on a different day. We investigated both functional connectivity between regions and brain activity (blood‐oxygen‐level‐dependent signal amplitude) within regions, hierarchically towards smaller topographical levels. We found that longer polysomnographic total sleep time is associated with lower blood‐oxygen‐level‐dependent signal amplitude in (pre)frontal regions. No objective or subjective sleep parameters were associated with functional connectivity between or within resting‐state networks. The findings may indicate a pathway through which sleep, in a ‘real‐life’ population setting, impacts brain activity or regional brain activity determines total sleep time.  相似文献   
75.
Background: Ablation of atrial autonomic inputs exerts antifibrillatory effects. However, because ablation destroys both myocardium and nerve cells, the effect of autonomic withdrawal alone remains unclear. We therefore examined the effects of pharmacologic autonomic blockade (PAB) on frequency and fractionation in patients with atrial fibrillation (AF). Methods: Esmolol and atropine were administered and electrograms were recorded simultaneously from both atria and the coronary sinus. In 17 patients, AF was recorded for 5 minutes and dominant frequency (DF) and continuous activity (CA) were compared before and during PAB. Results: Examination of the pooled data (537 sites, 17 patients) revealed a statistically significant decrease in mean DF (5.61–5.43Hz, P < 0.001) during PAB. Site‐by‐site analysis showed that 67% of sites slowed (0.45 ± 0.59 Hz), whereas 32% accelerated (0.49 ± 0.59Hz). Fractionation was reduced: median CA decreased from 31% to 26% (P < 0.001). In patient‐by‐patient analysis, mean DF/median CA decreased in 13 of 17 patients and increased in four. The spatial heterogeneity of DF decreased in nine of 17 patients (spatial coefficient of variation of DF at “nondriver sites” decreased by a mean of 2%). Conclusion: PAB decreases DF and CA in the majority of sites. Given the complexity of interactions between atrial cells during AF, the effects of PAB on DF and fractionation are more heterogeneous than the effects of PAB on isolated cells. (PACE 2011; 34:1460–1467)  相似文献   
76.
Surgical transection of the posterior connections of the medial basal hypothalamus is much more effective in producing hyperphagia and obesity in female than in male rats. The hyperphagia of female rats can be attenuated by daily injections of estradiol. When starved to the weight of control animals, previously obese female rats with cuts through the posterior hypothalamus showed only mild hyperphagia but quickly returned to their elevated body weights. The results indicated that hormonal and metabolic disturbance are important factors in determining food intake and body weight following damage to the ventromedial hypothalamus.  相似文献   
77.
78.
Diagnosis of chronic Q fever is difficult. PCR and culture lack sensitivity; hence, diagnosis relies mainly on serologic tests using an immunofluorescence assay (IFA). Optimal phase I IgG cutoff titers are debated but are estimated to be between 1:800 and 1:1,600. In patients with proven, probable, or possible chronic Q fever, we studied phase I IgG antibody titers at the time of positive blood PCR, at diagnosis, and at peak levels during chronic Q fever. We evaluated 200 patients, of whom 93 (46.5%) had proven, 51 (25.5%) had probable, and 56 (28.0%) had possible chronic Q fever. Sixty-five percent of proven cases had positive Coxiella burnetii PCR results for blood, which was associated with high phase I IgG. Median phase I IgG titers at diagnosis and peak titers in patients with proven chronic Q fever were significantly higher than those for patients with probable and possible chronic Q fever. The positive predictive values for proven chronic Q fever, compared to possible chronic Q fever, at titers 1:1,024, 1:2,048, 1:4,096, and ≥1:8,192 were 62.2%, 66.7%, 76.5%, and ≥86.2%, respectively. However, sensitivity dropped to <60% when cutoff titers of ≥1:8,192 were used. Although our study demonstrated a strong association between high phase I IgG titers and proven chronic Q fever, increasing the current diagnostic phase I IgG cutoff to >1:1,024 is not recommended due to increased false-negative findings (sensitivity < 60%) and the high morbidity and mortality of untreated chronic Q fever. Our study emphasizes that serologic results are not diagnostic on their own but should always be interpreted in combination with clinical parameters.  相似文献   
79.
Both hereditary and nonhereditary retinoblastoma (Rb) are commonly initiated by loss of both copies of the retinoblastoma tumor suppressor gene (RB1), while additional genomic changes are required for tumor initiation and progression. Our aim was to determine whether there is genomic heterogeneity between different clinical Rb subtypes. Therefore, 21 Rb tumors from 11 hereditary patients and 10 nonhereditary Rb patients were analyzed using high‐resolution single nucleotide polymorphism (SNP) arrays and gene losses and gains were validated with Multiplex Ligation‐dependent Probe Amplification. In these tumors only a few focal aberrations were detected. The most frequent was a focal gain on chromosome 2p24.3, the minimal region of gain encompassing the oncogene MYCN. The genes BAZ1A, OTX2, FUT8, and AKT1 were detected in four focal regions on chromosome 14 in one nonhereditary Rb. There was a large difference in number of copy number aberrations between tumors. A subset of nonhereditary Rbs turned out to be the most genomic unstable, while especially very young patients with hereditary Rb display stable genomes. Established Rb copy number aberrations, including gain of chromosome arm 1q and loss of chromosome arm 16q, turned out to be preferentially associated with the nonhereditary Rbs with later age of diagnosis. In contrast, copy number neutral loss of heterozygosity was detected mainly on chromosome 13, where RB1 resides, irrespective of hereditary status or age. Focal amplifications and deletions and copy number neutral loss of heterozygosity besides chromosome 13 appear to be rare events in retinoblastoma. © 2013 Wiley Periodicals, Inc.  相似文献   
80.
Inter-subject variability in therapeutic drug response and drug toxicity is a major problem in clinical practice. In this field genetic polymorphisms of drug metabolizing enzymes play an important role. In a multicenter study supported by the German Federal Institute for Drugs and Medical Devices (BfArM, Z 12.01-68502-201) adverse drug reactions (ADRs) leading to hospital admission to departments of internal medicine have been registered and evaluated. The aim of the presented part of the study was to look for evident differences in genotypes for polymorphic drug metabolizing enzymes between adverse drug reaction cases and controls. All cases found in the local area – Jena and Weimar – were genotyped for N-acetyl-transferase 2 (NAT2), cytochrom P450 (CYP) 2D6 and 2C19 in comparison to a control population of the same region. The investigation on genotype was carried out for about 2 years (2000–2002). 254 blood samples from patients of the ADR study were analyzed. The genotype of drug metabolizing enzymes was determined by means of polymerase chain reaction using allel specific primers or restriction enzyme analysis. Within all ADRs cases genotyped, no exceptional frequencies for slow acetylators or poor metabolizers (PM) of CYP2D6 or CYP2C19 were found. About 65% of the individuals with ADR genotypically displayed a slow acetylator state. 6.3% PM for CYP2D6, including CYP2D6*3, *4 and *6 alleles, and 2.0% PM frequency for CYP2C19 (*2) have been found in ADR cases. A direct connection between PM genotype and the ADR observed may be assumed only in few of them. Further investigations on genotype and ADR-associated drugs require a much larger sample of patients to obtain more data allowing to focus an association on specific drugs, ADR and polymorphisms genotype of drug metabolizing enzymes might be useful.  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