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   13028篇
  免费   732篇
  国内免费   26篇
耳鼻咽喉   100篇
儿科学   385篇
妇产科学   199篇
基础医学   1647篇
口腔科学   406篇
临床医学   1375篇
内科学   2569篇
皮肤病学   160篇
神经病学   1243篇
特种医学   352篇
外科学   2069篇
综合类   102篇
一般理论   9篇
预防医学   859篇
眼科学   307篇
药学   1028篇
中国医学   19篇
肿瘤学   957篇
  2023年   104篇
  2022年   132篇
  2021年   241篇
  2020年   223篇
  2019年   313篇
  2018年   298篇
  2017年   279篇
  2016年   311篇
  2015年   302篇
  2014年   434篇
  2013年   672篇
  2012年   884篇
  2011年   890篇
  2010年   476篇
  2009年   474篇
  2008年   805篇
  2007年   844篇
  2006年   793篇
  2005年   712篇
  2004年   699篇
  2003年   667篇
  2002年   604篇
  2001年   135篇
  2000年   105篇
  1999年   146篇
  1998年   171篇
  1997年   159篇
  1996年   126篇
  1995年   105篇
  1994年   113篇
  1993年   82篇
  1992年   89篇
  1991年   96篇
  1990年   95篇
  1989年   89篇
  1988年   82篇
  1987年   79篇
  1986年   77篇
  1985年   91篇
  1984年   74篇
  1983年   61篇
  1982年   91篇
  1981年   54篇
  1980年   51篇
  1979年   57篇
  1978年   42篇
  1977年   42篇
  1976年   38篇
  1975年   29篇
  1974年   28篇
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
61.
Acyclovir treatment was used in a randomized, double-blind, placebo-controlled clinical trial with parallel groups to test the hypothesis that herpes virus infections are involved in the pathogenesis of multiple sclerosis (MS). Sixty patients with the relapsing-remitting form of MS were randomized to either oral treatment with 800 mg acyclovir or placebo tablets three times daily for 2 years. The clinical effect was investigated by an extensive test battery consisting of neurological examinations, neuro-ophthalmological and neuropsychological tests, and evoked potentials. Results were based on intent-to-treat data and the primary outcome measure was the exacerbation rate. In the acyclovir group (n = 30), 62 exacerbations were recorded during the treatment period, yielding an annual exacerbation rate of 1.03. The placebo group (n = 30) had 94 exacerbations and an annual exacerbation rate of 1.57. Thus, 34% fewer exacerbations were encountered during acyclovir treatment. This difference in exacerbation rate between the treatment groups was not significant (P = 0.083). However, this trend to a lower disease activity in acyclovir-treated patients was supported in subsequent data analysis. If the patients were grouped according to exacerbation frequencies, i.e. into low (0–2), medium (3–5) and high (6–8) rate groups, the difference between acyclovir and placebo treatment was significant (P = 0.017). Moreover, in a subgroup of the population with a duration of the disease of at least 2 years providing an exacerbation rate base-line before entry, individual differences in exacerbation rates were compared between the 2-year pre-study period and the study period in acyclovir-treated (n = 19) and placebo (n = 20) patients and acyclovir-treated patients showed a significant reduction of exacerbations (P = 0.024). Otherwise, neurological parameters were essentially unaffected by acyclovir treatment and there were no convincing signs of reduced neurological deterioration in the acyclovir group. This study indicates that acyclovir treatment might inhibit the triggering of MS exacerbations and thus suggests that acyclovir-susceptible viruses might be involved in the pathogenesis of MS. This possibility warrants further investigation.  相似文献   
62.
63.
The objective of the present study was to assess the relationship between the amount of lactate accumulated during complete ischaemia and the ensuing changes in extra- and intracellular pH (pHe and pHi, respectively). The preischaemic plasma glucose concentration of anaesthetized rats was varied by administration of glucose or insulin, pHe was determined in neocortex with ion-sensitive microelectrodes, and tissue lactate and CO2 contents were measured, tissue CO2 tension being known from separate experiments. The experiments were carried out in both normocapnic [arterial CO2 tension (PaCO2) approximately 40 mm Hg] and hypercapnic (PaCO2 approximately 80 mm Hg) animals. Irrespective of the preischaemic CO2 tension, DeltapHe was linearly related to tissue lactate content. Depending on the preischaemic glucose concentration, DeltapHe varied from <0.4 to >1.4 units. The results thus fail to confirm previous results that the changes in pHe describe two plateau functions (DeltapHe approximately 0.5 and 1.1, respectively), with a transition zone at tissue lactate contents of 17 - 20 mmol kg-1. Changes in pHi given in this study are based on the assumption of a uniform intracellular space. The pHi changed from a normal value of approximately 7.0 to 6.5, 6.1 and 5.8 at tissue lactate contents of 10, 20 and 30 mmol kg-1. The intrinsic (non-bicarbonate) buffer capacity, derived from these figures, was 23 mmol kg-1 pH-1. Some differences in pH and in HCO3- concentration between extra- and intracellular fluids persisted in the ischaemic tissue. These differences were probably caused by a persisting membrane potential in the ischaemic cells.  相似文献   
64.
PURPOSE: The purpose is to evaluate relationships between objectively assessed exercise capacity and subjectively assessed scoring of physical functioning and well-being after erythropoietin treatment in cancer patients on palliative care. EXPERIMENTAL DESIGN: Unselected cancer patients (n = 108) who experienced progressive cachexia were randomized to receive either anti-inflammatory treatment alone (indomethacin) or recombinant erythropoietin plus indomethacin to prevent the appearance of disease-induced anemia and thereby protect patients' exercise capacity. Follow-up investigations of nutritional status, exercise capacity, and health-related quality of life assessed by SF-36 and the European Organization for Research and Treatment of Cancer QLQ-C30 were compared. RESULTS: Effective treatment by erythropoietin on top of basal whole body anti-inflammatory treatment was confirmed and indicated by time course changes of biochemical, physiologic, and nutritional objectives, whereas individual self-reported scoring of physical functioning and general health did not indicate a clear-cut effectiveness, particularly at moderately subnormal hemoglobin levels. CONCLUSIONS: Discrepancies between objective and subjective self-reported measures may be either fundamental or indicate scoring limitations for evaluation of therapeutic results. Present results demonstrate a clinical benefit of erythropoietin treatment in cancer patients with subnormal to normal hemoglobin levels, whereas the patients' own subjective scoring was insufficient to sense such improvements. The discrepancy may be either fundamental or methodological but emphasizes the importance to document therapeutic outcome in both subjective and objective perspectives in palliative care of cancer patients.  相似文献   
65.
Long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency is a recently discovered disorder affecting the mitochondrial-oxidation of fatty acids. There have been few reports of the pathologic findings in-oxidation defects. We examined pathologic specimens from 16 patients with this disorder (11 patients were homozygous for the common mutation G1528C, 5 patients were siblings with a similar clinical presentation). Autopsies were performed on all 15 patients who died, and liver biopsy specimens were available from 8 patients. Hepatomegaly and steatosis of the liver, found in every patient, were often combined with fibrosis or cirrhosis. Cardiomegaly and accumulation of fat in the myocardium, renal tubules, and skeletal muscle were found in many patients. A detailed neuropathologic examination was performed on six patients, and brain specimens obtained at autopsy were examined in four others. In general, neuropathologic findings were mild and unspecific, but vacuolization was detected in the deep gray matter and in the cerebellum and brain stem nuclei of five patients. In one patient the vacuolization was prominent; in the other four it was milder and more focal. The vacuoles seemed to be either in the neuropil or associated with swollen hydropic cells. The uniform pattern of histopathologic changes facilitates the diagnostics in this severe disorder, allowing opportunities for therapy and prenatal diagnosis.  相似文献   
66.
Numerous theories have been presented that attempt to explain the frequent recurrences of pharyngotonsillitis caused by Streptococcus pyogenes; these recurrences occur after seemingly adequate antibiotic treatment. We previously have demonstrated that S pyogenes can survive for up to 7 days intracellularly in immortalized human respiratory epithelial cells grown in an antibiotic supplemented medium. Viable S pyogenes were externalized and established an extracellular infection, whenever the extracellular antibiotic was removed. We have investigated the presence of intracellular S pyogenes in two in vivo studies using respiratory epithelial cells collected from patients with tonsillitis and the tonsils of asymptomatic carriers. Electron microscopy and immunohistochemistry demonstrated intracellular S pyogenes in pharyngeal epithelial cells in 13 of 14 patients with tonsillitis (93%). Furthermore, intracellular S pyogenes were found in macrophage-like cells in eight (73%) and in epithelial cells in four (36%) tonsils from 11 asymptomatic S pyogenes carriers. These in vivo data strongly support the hypothesis that intracellular S pyogenes can constitute a reservoir of bacteria with the potential to cause reinfections  相似文献   
67.
Fibrosarcoma is a rare tumour in children. The potential of malignancy has been questioned. We present three cases of fibrosarcoma in children. The follow-up periods range from 10 to 37 years. The first patient had pulmonary metastases at the time of diagnosis in 1958. The primary tumour in fossa ischio-rectalis was resected in 1960. Lung metastases were resected in 1960 and 1989. Radiotherapy was given in 1992. He is still alive with metastases 37 years after the first manifestation of disease. The second patient had a primary tumour and several local recurrences in the mandible. He is alive without evidence of disease 4 years after resection of pulmonary metastases and 21 years after resection of the primary tumour. The third patient has no signs of recurrence or metastasic spread 10 years after a wide excision of subcutanous tumours of the left upper arm. The cases demonstrate a special tumour-entity of low-grade malignancy, which show a good prognosis and a wide spectrum of biological behaviour.  相似文献   
68.
69.
70.
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