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   5627篇
  免费   341篇
  国内免费   2篇
耳鼻咽喉   165篇
儿科学   316篇
妇产科学   87篇
基础医学   685篇
口腔科学   197篇
临床医学   540篇
内科学   977篇
皮肤病学   53篇
神经病学   779篇
特种医学   155篇
外科学   731篇
综合类   19篇
一般理论   5篇
预防医学   424篇
眼科学   104篇
药学   279篇
中国医学   1篇
肿瘤学   453篇
  2023年   20篇
  2022年   33篇
  2021年   64篇
  2020年   61篇
  2019年   61篇
  2018年   106篇
  2017年   81篇
  2016年   141篇
  2015年   104篇
  2014年   131篇
  2013年   275篇
  2012年   311篇
  2011年   338篇
  2010年   178篇
  2009年   184篇
  2008年   372篇
  2007年   369篇
  2006年   349篇
  2005年   406篇
  2004年   383篇
  2003年   356篇
  2002年   345篇
  2001年   143篇
  2000年   166篇
  1999年   98篇
  1998年   66篇
  1997年   60篇
  1996年   48篇
  1995年   56篇
  1994年   49篇
  1993年   51篇
  1992年   42篇
  1991年   31篇
  1990年   32篇
  1989年   22篇
  1988年   21篇
  1987年   11篇
  1986年   30篇
  1985年   28篇
  1984年   27篇
  1983年   36篇
  1982年   46篇
  1981年   21篇
  1980年   36篇
  1979年   23篇
  1978年   21篇
  1977年   18篇
  1976年   20篇
  1975年   13篇
  1974年   16篇
排序方式: 共有5970条查询结果,搜索用时 31 毫秒
41.
Well-trained subjects (n=6) were studied before and after losing a mean 3.0%–4.3% of body mass to determine whether muscle performance could be maintained or even enhanced by dietary creatine supplementation. During a 5-day period of loss of mass the subjects were randomly assigned to a creatine or placebo supplemented diet. All the subjects were measured before and after loss of mass on both supplements for isokinetic peak torque (PT) and work at peak torque (W PT) of knee extensors, also for intermittent high intensity working capacity of the same muscle group. The latter test consisted of submaximal isokinetic knee extensions at an angular velocity of 1.57 rad?·?s?1 for 45 s at the rate of 30 contractions each min (submaximal work, W s max ) followed by 15-s maximal effort (maximal work, W max ). Total duration of the test was 3 min. Haematocrit was measured and haemoglobin, ammonia, lactate, glucose and urea concentrations were analysed in blood samples obtained at rest and after cessation of muscle performance tests. The results indicated that creatine supplementation in comparison with placebo treatment during rapid body mass reduction may help to maintain muscle PT and W PT at high angular velocities, not influencing W max and the rate of fatigue development during W max , but affecting adversely W s max . Within the limitations of the present study the reasons for the partially detrimental effect of creatine administration remain obscure, but it is suggested that impaired creatine uptake in muscle during body mass loss as well as creatine induced changes in muscle glucose and glycogen metabolism may be involved.  相似文献   
42.
43.
Tenascin-C is an extracellular matrix glycoprotein that is spatially expressed during organogenesis, in inflammatory and fibrotic disorders, and in neoplasms. The aim of this study was to analyze its expression in developing human lung tissues during pseudoglandular, canalicular, saccular, and alveolar periods corresponding to Weeks 12 to 40. Lung tissues were obtained at autopsy from 34 nonmalformed cases. An immunohistochemical analysis and a messenger RNA (mRNA) in situ hybridization method combined with light microscopy were used. The extent of tenascin-C immunoreactivity was scored as absent, low, moderate, or strong in and around different types of pulmonary cells. The immunohistochemical expression for tenascin-C was strong beneath the airway epithelium, especially at the sites of airway subdivision during Weeks 12 to 23, whereas its expression was moderate or weak underneath alveolar and bronchiolar epithelia between Weeks 24 and 40. The expression for tenascin-C was strong in the intima of veins, especially in the canalicular period, i.e., Weeks 17 to 28. A moderate or strong immunoreactivity for tenascin-C was also observed around chondrocytes in every case studied during all periods. The increased expression of tenascin-C mRNA was most often seen in the cells below the airway epithelium. Taken together, tenascin-C is expressed in human lung during all developmental periods, and its expression is especially strong below the airway epithelium at the sites of airway subdivision.  相似文献   
44.
Neuropathological diagnostic criteria for Creutzfeldt-Jakob disease (CJD) and other human transmissible spongiform encephalopathies (prion diseases) are proposed for the following disease entities: CJD - sporadic, iatrogenic (recognised risk) or familial (same disease in 1st degree relative): spongiform encephalopathy in cerebral and/or cerebellar cortex and/or subcortical grey matter; or encephalopathy with prion protein (PrP) immuno-reactivity (plaque and/or diffuse synaptic and/or patchy/perivacuolar types). Gerstmann-Sträussler-Scheinker disease (GSS) (in family with dominantly inherited progressive ataxia and/or dementia): encephalo(myelo)pathy with multicentric PrP plaques. Familial fatal insomnia (FFI) (in member of a family with PRNP178 mutation): thalamic degeneration, variable spongiform change in cerebrum. Kuru (in the Fore population). Without PrP data, the crucial feature is the spongiform change accompanied by neuronal loss and gliosis. This spongiform change is characterised by diffuse or focally clustered small round or oval vacuoles in the neuropil of the deep cortical layers, cerebellar cortex or subcortical grey matter, which might become confluent. Spongiform change should not be confused with non-specific spon-giosis. This includes status spongiosus (“spongiform state”), comprising irregular cavities in gliotic neuropil following extensive neuronal loss (including also lesions of “burnt-out” CJD), “spongy” changes in brain oedema and metabolic encephalopathies, and artefacts such as superficial cortical, perineuronal, or perivascular vacuolation; focal changes indistinguishable from spongiform change may occur in some cases of Alzheimer's and diffuse Lewy body diseases. Very rare cases might not be diagnosed by these criteria. Then confirmation must be sought by additional techniques such as PrP immunoblotting, preparations for electron microscopic examination of scrapie associated fibrils (SAF), molecular biologic studies, or experimental transmission.  相似文献   
45.
Genetic carrier testing of children is usually not recommended. However, there are no data concerning long-term psychological consequences, experience, and satisfaction of those tested as well as their recall of the test results. We evaluated these items retrospectively 10–24 years after carrier testing performed in childhood. Study material comprised 25 families with aspatylglucosaminuria (AGU), an autosomal recessive disorder, with 35 healthy sibs from all parts of Finland tested for carriership during childhood between 1973 and 1987. Of these sibs, 25 participated in our study. The questionnaire comprised multiple-choice and open-ended questions. The psychosocial well-being of the study subjects measured by the RAND 36 item Health Survey 1.0 (RAND) was, in general, at least as good as that of controls, and showed no significant differences between carriers and non-carriers (p>0.154). All tested individuals were satisfied with the fact that they had been tested and stated that the decision to perform carrier testing on a child can be made by the parents. Of the 25 tested, 23 knew and understood their test result correctly at the time of our study. Most of the tested individuals (60%) stated that the best time for carrier testing would be in the childhood or in the teen years.
This study indicates that carrier testing in childhood for an autosomal recessive disorder (AGU) had caused no measurable disturbance of quality of life in adulthood, and those tested reported being satisfied. However, we do not recommend testing in childhood, as the result is not needed prior to the time for reproductive decisions.  相似文献   
46.
A real-time PCR method was developed and used to detect Aspergillus fumigatus mitochondrial DNA (mtDNA) in bronchoalveolar lavage (BAL) fluids and tissue biopsy specimens. The analytical sensitivity of the assay was one A. fumigatus conidium per reaction, and the assay was linear at least over 4 orders of magnitude above the detection limit. BAL fluids from 66 immunocompromised patients at risk of invasive pulmonary aspergillosis (IPA) and 33 immunocompetent controls and tissue biopsy specimens from 10 immunocompromised patients were analyzed. The results were related to the clinical diagnosis established according to recently published consensus criteria. A. fumigatus mtDNA positivity was encountered in 16 of 81 (20%) BAL fluid specimens from patients at risk and 1 of 33 (3%) specimens from immunocompetent controls. PCRs were positive in six of seven, two of four, and four of five of the patients with proven, probable, and possible IPA, respectively, as well as in four patients at risk but without any other evidence of IPA. With qualitative detection, the diagnostic sensitivity of PCR was 73%, specificity was 93%, and predictive values of positive (PPV) and negative (NPV) results were 73 and 95%, respectively. Using a threshold cycle of <35 as a limit for positive PCR, the specificity and PPV of PCR in the diagnosis of invasive aspergillosis were 100%, but its sensitivity was only 45% and NPV was 92%. PCR was positive in tissue biopsy specimens from all patients with invasive aspergillosis caused by A. fumigatus. Semiquantitative detection of A. fumigatus mtDNA in BAL fluid may be helpful in the diagnosis of IPA. PCR is well suited for the verification of the presence of A. fumigatus in tissue biopsy specimens.  相似文献   
47.
48.
49.
PurposeCompletely displaced distal radius fractures in children have been traditionally reduced and immobilized with a cast or pin fixed. Cast immobilization leaving the fracture displaced in the bayonet position has been recently suggested as a non-invasive and effective treatment alternative. This is a pilot comparative study between reduction and no reduction.MethodsWe assessed subjective, functional and radiographic outcome after a minimum 2.5-year follow-up in 12 children under ten years of age who had sustained a completely displaced metaphyseal radius fracture, which had been immobilized leaving the fracture in an overriding position (shortening 3 mm to 9 mm). A total of 12 age-matched patients, whose similar fractures were reduced and pin fixed, were chosen for controls. ResultsAt follow-up none of the 24 patients had visible forearm deformity and the maximal angulation in radiographs was 5° Forearm and wrist movement was restored (< 10° of discrepancy) in all 24 patients. Grip strength ratio was normal in all but three surgically treated patients. All patients had returned to their previous activities. One operatively treated boy who was re-operated on reported of pain (visual analogue scale 2).ConclusionThe results of this study do not demonstrate the superiority of reduction and pin fixation over cast immobilization in the bayonet position of closed overriding distal metaphyseal radius fractures in children under ten years with normal neurovascular findings.Level of evidenceIII  相似文献   
50.
Immunohistochemical expression of neuronal (n), endothelial (e), and inducible (i) NOS and their association with the type, grade, apoptotic index, proliferation of tumors and the survival of patients were investigated in 89 biopsies of non-small cell lung carcinoma (NSCLC). In tumor cells, expression of iNOS was detected in 35/89 (40%) cases, while 79/89 (89%) and 72/89 (81%) cases showed weak to intense positivity for eNOS and nNOS, respectively. Strong eNOS staining was seen significantly more often in adenocarcinomas than in squamous cells carcinomas (p=0.016), and iNOS immunoreactivity was seen more often in grade I-II tumors than in grade III tumors (p=0.024). There was no significant difference between the low and high apoptotic indexes or between the low and high proliferation rates of tumors in any instance of NOS staining. The patients with tumors showing high nNOS expression tended to have better survival than the others (p=0.06, log-rank; p=0.04, Bresow; p=0.048, Tarone-Ware). Similarly, the patients with tumors showing high expression of iNOS, eNOS and nNOS, as determined by a combined sum index, had a better survival than those with a low sum index for these enzymes (p<0.05). The results show intense expression of eNOS and nNOS, and moderate expression of iNOS in tumor cells of non-small cell carcinoma. Intense NOSs expression seems to be a favorable prognostic sign in non-small cell lung carcinoma.  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