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   3696篇
  免费   238篇
  国内免费   4篇
耳鼻咽喉   31篇
儿科学   60篇
妇产科学   54篇
基础医学   524篇
口腔科学   65篇
临床医学   309篇
内科学   904篇
皮肤病学   95篇
神经病学   400篇
特种医学   81篇
外科学   441篇
综合类   10篇
一般理论   3篇
预防医学   297篇
眼科学   25篇
药学   237篇
中国医学   8篇
肿瘤学   394篇
  2023年   23篇
  2022年   72篇
  2021年   154篇
  2020年   62篇
  2019年   133篇
  2018年   149篇
  2017年   89篇
  2016年   80篇
  2015年   88篇
  2014年   146篇
  2013年   194篇
  2012年   289篇
  2011年   285篇
  2010年   171篇
  2009年   145篇
  2008年   206篇
  2007年   177篇
  2006年   188篇
  2005年   183篇
  2004年   148篇
  2003年   142篇
  2002年   142篇
  2001年   79篇
  2000年   61篇
  1999年   61篇
  1998年   29篇
  1997年   34篇
  1996年   19篇
  1995年   21篇
  1994年   22篇
  1993年   15篇
  1992年   54篇
  1991年   46篇
  1990年   30篇
  1989年   28篇
  1988年   21篇
  1987年   15篇
  1986年   23篇
  1985年   18篇
  1984年   11篇
  1982年   5篇
  1981年   5篇
  1979年   12篇
  1977年   6篇
  1976年   5篇
  1975年   4篇
  1973年   4篇
  1972年   4篇
  1971年   5篇
  1933年   4篇
排序方式: 共有3938条查询结果,搜索用时 15 毫秒
31.
Heat shock protein 60 (HSP60) from Chlamydia pneumoniae was described to trigger in vitro inflammatory and cytokine responses including TNF and IL-12p40. Although it can be found in atherosclerotic plaques of patients, the stimulatory potential of chlamydial and other HSP60 in vivo is unclear. We now report that chlamydial HSP60 fails to induce TNF expression in vivo, and significant serum levels of IL-12p40 are only found upon intraperitoneal injection of high doses of HSP60 or after intravenous application. Upon purification of chlamydial HSP60 with polymyxin B-agarose columns, its ability to induce TNF secretion in vitro is much reduced. However, purified chlamydial HSP60 causes increased serum levels of the CXC chemokines KC and MIP2 in vivo, as well as a strong accumulation of polymorphonuclear neutrophils (PMN) in the peritoneal cavity upon intraperitoneal challenge. With respect to PMN accumulation, chlamydial HSP60 is more potent than endotoxin or the CpG oligonucleotide 1668. The responses observed are completely abolished in Toll-like receptor (TLR)2/4-double-deficient mice, while single-deficient mice respond almost normally. Furthermore, KC induction and PMN accumulation are largely dependent on MyD88. In conclusion, HSP60 from C. pneumoniae triggers inflammatory responses in vivo that differ from responses induced by endotoxin or CpG oligonucleotides and are dependent on TLR2 and 4.  相似文献   
32.
Marfan Syndrome (MfS) is an autosomal dominant inherited connective tissue disorder with variable phenotypic expression of cardiovascular, skeletal and ocular manifestations. Cardiovascular complications, such as aortic aneurysm and dissection drastically reduce life expectancy of individuals with MfS, whereas preventive surgery substantially improves the prognosis of these patients. A number of mutations in the fibrillin 1 (FBN1) gene associated with MfS have been identified to date, demonstrating considerable molecular heterogeneity. One region, however, located around exon 24, exhibits a striking clustering of mutations, which are associated with a severe, socalled neonatal form of MfS. Here we report the first mutation (G2950A) in exon 24 of the neonatal region of the FBN1 gene, associated with a classic MfS phenotype. The mutation leads to the subsitution of valin by isoleucin (V984I), both uncharged amino acids, which only differ in a single methyl group. This defect was identified in a proband with cardiovascular manifestations of MfS by SSCP analysis of PCR-amplified genomic DNA, direct PCR sequencing and RFLP analysis. The substitution was neither detected in the unaffected 4-year old daughter of the proband, nor in 3 of his healthy family members nor in 108 allels from control individuals, suggesting that this mutation is causative for MfS in the patient. Since no other family member of the proband is affected by MfS, the defect described is sporadic. In summary, we identified a novel defect in exon 24 of the neonatal region of the FBN1 gene in a patient with a classic phenotype of MfS, suggesting that conservative substitutions in this region may lead to a less severe phenotype of the disease. This finding further demonstrates the remarkable phenotypic heterogeneity associated with FBN1 mutations and stresses the significance of modifying genes and individual alterations in protein function for the pheontypic expression of the disease.  相似文献   
33.
The immunological mechanisms that contribute to resistance versus susceptibility to bacterial and parasitic infection are central to the development of improved prophylactic and therapeutic strategies. The delineation of two subsets of CD4+ T cells in the mouse that regulate these responses has provided a tremendous advance in understanding disease pathogenesis. The elucidation of protective immune mechanisms distinct from those that cause tissue damage should lead to the development of appropriate vaccines against these devastating illnesses.  相似文献   
34.
TNF inhibits malaria hepatic stages in vitro via synthesis of IL-6   总被引:5,自引:0,他引:5  
We examined the capacity of murine recombinant tumor necrosis factor (rmTNF) to induce an inhibitory effect at the hepatic stage on malaria induced by Plasmodium yoelii sporozoites. When injected three times, 1.0 micrograms of rmTNF was found to protect 78% of mice against a sporozoite challenge. In contrast, whatever the dose and the schedule of administration, no inhibition was observed when purified hepatocyte cultures were infected with P. yoelii. The addition of non-parenchymal hepatic cells to hepatocyte cultures restored the capacity of TNF to modulate hepatic stage development, leading to up to 44% inhibition. Antibodies to interleukin 6 reversed the anti-parasite activity in the co-culture system.  相似文献   
35.
We aimed to differentiate gut microbiota composition of overweight/obese and lean subjects and to determine its association with clinical variables and dietary intake. A cross-sectional study was performed with 96 overweight/obese subjects and 32 lean subjects. Anthropometric parameters were positively associated with Collinsella aerofaciens, Dorea formicigenerans and Dorea longicatena, which had higher abundance the overweight/obese subjects. Moreover, different genera of Lachnospiraceae were negatively associated with body fat, LDL and total cholesterol. Saturated fatty acids (SFAs) were negatively associated with the genus Intestinimonas, a biomarker of the overweight/obese group, whereas SFAs were positively associated with Roseburia, a biomarker for the lean group. In conclusion, Dorea formicigenerans, Dorea longicatena and Collinsella aerofaciens could be considered obesity biomarkers, Lachnospiraceae is associated with lipid cardiovascular risk factors. SFAs exhibited opposite association profiles with butyrate-producing bacteria depending on the BMI. Thus, the relationship between diet and microbiota opens new tools for the management of obesity.  相似文献   
36.
IntroductionRobotic surgery has become a safe and effective approach for the treatment of pulmonary surgical pathology. However, the adoption of new surgical techniques requires the evaluation of the learning curve. The objective of this study is to analyze the learning curve of robotic anatomical lung resections.MethodsRetrospective analysis of all robotic anatomical lung resections performed by the same surgeon between June 2018 and March 2020. The learning curve was evaluated using CUSUM charts to estimate trend changes in surgical time, surgical failure and the occurrence of post-operative cardiorespiratory complications throughout the sequence of cases.ResultsThe study included a total of 73 cases. The median duration of all complications was 120 min (interquartile range: 90-150 min), the prevalence of surgical failure was 23.29%, while 4/73 patients had any postoperative cardiorespiratory complication. Based on the CUSUM analysis, the learning curve was divided into 3 different phases: phase i (from the first to the 14th intervention), phase ii (between the 15th and 30th intervention) and phase iii (from the 31st intervention).ConclusionsThe learning curve for robotic anatomical lung resections can be divided into 3 phases. The technical competence that guarantees satisfactory perioperative outcomes was achived in phase iii from the 31st intervention.  相似文献   
37.
38.
We have measured the humoral response to messenger RNA (mRNA) vaccines in COVID-19 naïve and convalescent individuals. Third doses of mRNA COVID-19 vaccines induced a significant increase in potency and breadth of neutralization against SARS-CoV-2 variants of concern (VoC) including Omicron subvariants BA.1, BA.2, and BA.2.12.1, that were cross-neutralized at comparable levels and less for BA.4/5. This booster effect was especially important in naïve individuals that only after the third dose achieved a level that was comparable with that of vaccinated COVID-19 convalescents except for BA.4/5. Avidity of RBD-binding antibodies was also significantly increased in naïve individuals after the third dose, indicating an association between affinity maturation and cross neutralization of VoC. These results suggest that at least three antigenic stimuli by infection or vaccination with ancestral SARS-CoV-2 sequences are required to induce high avidity cross-neutralizing antibodies. Nevertheless, the circulation of new subvariants such as BA.4/5 with partial resistance to neutralization will have to be closely monitored and eventually consider for future vaccine developments.  相似文献   
39.
The results of the prospective application of Horn's Severity of Illness Index in a teaching hospital during 1987, 1989, and 1990 constitute the basis of the present report. The average overall severity of illness scores for the three years were 1.42 in 1987, 1.65 in 1989, and 1.46 in 1990. Most of the processes evaluated in the three periods showed an overall distribution among severity levels 1 and 2, both overall and when the seven dimensions of the severity of illness index were analyzed. A statistically significant correlation between the overall severity of illness and average length of stay was found for patients in 1989 and 1990. The length of stay differed significantly in the different severity levels. When the four levels of the seven dimensions of the severity of illness index for 1987, 1989, and 1990 were compared, it was observed that figures were not uniformly distributed. There was a statistically significant association between severity of illness for hospital service and pharmacy charges per hospital stay for both 1989 and 1990, as well as a statistically significant inverse relationship between severity of illness and the number of claims per hospital service in both periods of time. Case-mix methods that account for the severity of patients constitute a useful indicator of quality for the management of different hospital services and of the hospital as a whole.  相似文献   
40.
Fever and infection early after ischemic stroke   总被引:7,自引:0,他引:7  
Previous studies showed that elevated body temperature early after ischemic stroke is associated with severe neurological deficit and a poor outcome. The aim of this study was to analyse the prevalence and putative etiology of febrile body temperature (>/=38.0 degrees C) early after stroke and to investigate the association between body temperature, stroke severity and outcome. We investigated 119 consecutive patients who were admitted within 24 h after ischemic stroke. Patients were examined for infection before ischemia using a standardized questionnaire and received daily clinical examination after stroke. In case of fever, standardized radiological and microbiological examinations were performed. Fever within 48 h after stroke was observed in 30 (25.2%) patients. The probable cause of fever was infective or chemical aspiration pneumonia (n=12), other respiratory tract infection (n=7), urinary tract infection (n=4), viral infections (n=3) or insufficiently defined (n=5). (One patient had two potential causes of fever.) In thirteen of these patients, infection was most probably acquired before stroke. Fever newly developed more often during day 1 to 2 than day 3 to 7 after stroke (P=0.016). Fever was associated with a more severe deficit on admission independent from age, vascular diseases and risk factors (odds ratio 9.6; 95% confidence interval 3.1-29). Fever is a frequent complication early after stroke and in the majority of cases, it can be explained by infection or chemical aspiration pneumonia. In about half of the infected patients, infection was most probably acquired before stroke. Fever was associated with a more severe neurological deficit on admission.  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