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   165278篇
  免费   13403篇
  国内免费   2547篇
耳鼻咽喉   725篇
儿科学   4798篇
妇产科学   3630篇
基础医学   11222篇
口腔科学   3035篇
临床医学   33457篇
内科学   24707篇
皮肤病学   1661篇
神经病学   5308篇
特种医学   1860篇
外国民族医学   11篇
外科学   10580篇
综合类   16878篇
现状与发展   9篇
一般理论   65篇
预防医学   28039篇
眼科学   829篇
药学   22364篇
  156篇
中国医学   3028篇
肿瘤学   8866篇
  2024年   447篇
  2023年   3886篇
  2022年   6269篇
  2021年   8309篇
  2020年   7537篇
  2019年   7421篇
  2018年   7079篇
  2017年   6449篇
  2016年   6452篇
  2015年   6642篇
  2014年   11957篇
  2013年   13938篇
  2012年   10246篇
  2011年   10857篇
  2010年   8210篇
  2009年   8008篇
  2008年   7727篇
  2007年   7665篇
  2006年   6537篇
  2005年   5568篇
  2004年   4666篇
  2003年   3606篇
  2002年   2859篇
  2001年   2564篇
  2000年   2208篇
  1999年   1936篇
  1998年   1545篇
  1997年   1354篇
  1996年   1151篇
  1995年   930篇
  1994年   885篇
  1993年   721篇
  1992年   628篇
  1991年   534篇
  1990年   451篇
  1989年   401篇
  1988年   345篇
  1987年   355篇
  1986年   279篇
  1985年   420篇
  1984年   343篇
  1983年   221篇
  1982年   268篇
  1981年   201篇
  1980年   196篇
  1979年   154篇
  1978年   129篇
  1977年   129篇
  1976年   135篇
  1975年   123篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
The role of Chlamydia pneumoniae in 110 Sudanese children with signs of acute lower respiratory tract infections (ALRI) was investigated. Four (3.6%) had evidence of C. pneumoniae infection, of whom 3 were culture-positive, while 1 had an antibody response suggesting a recent infection. IgG antibodies at a titer of ≥1:32 to C. pneumoniae, Chlamydia psittaci and Chlamydia trachomatis were detected in 27 (24.5%), 27 (24.5%) and 7 (6.4%) of the 110 ALRI cases, respectively. C. pneumoniae, C. trachomatis or C. psittaci were not detected in nasopharyngeal secretions from any of 110 patients when fluorescence-labeled specific monoclonal antibodies were used. In a seroepidemiological survey, 318 healthy Sudanese persons aged between 1 month and 67 years were studied for C. pneumoniae antibodies.  相似文献   
82.
Summary: Oral administration of carbamazepine (CBZ)(15, 10, or 5 mg/kg) to mice significantly decreased both humoral and cellular immune responses evaluated by enumeration of direct and indirect plaque-forming spleen cells (PFC) and delayed–type hypersensitivity reaction (DTH) against sheep red blood cells (SRBC) as compared with those observed in normal control animals. Moreover, spleen T cells obtained from CBZ–treated donor mice were capable of decreasing both PFC and DTH responses of normal spleen cells transferred into lethally irradiated recipient animals. The immunodepressor effect of CBZ was observed even though administration of CBZ induced augmentation of spleen cellularity.  相似文献   
83.
Measurements of respiratory mechanics are frequently made in ventilated infants and children. Esophageal pressure measurements (Pes using a balloon on a catheter have been used to partition the respiratory mechanics into lung and chest wall components. Appropriate positioning of this balloon is crucial to obtain accurate estimates of pleural pressure. Traditionally, in spontaneously breathing subjects the balloon position is assessed with an occlusion test. In ventilated subjects, it is not always possible to perform an occlusion test prior to paralysis, and even if such a test is performed it may not be relevant under conditions of positive pressure ventilation. We have assessed a positive pressure occlusion test that is suitable for paralyzed subjects. By occluding the airway opening and applying gentle pressure to the abdomen or rib cage, positive swings in pressure can be measured by both Pes and airway opening pressure (Pao). We compared traditional occlusion tests measured in 16 spontaneously breathing puppies to the positive pressure occlusion test performed after paralysis. In 2 pups we were unable to obtain a reasonable traditional occlusion test (>15% difference between Pes and Pao) but we obtained 10 traditional occlusion tests in each of the remaining 14 pups (2.1–14 kg). In 11 of these animals Ape, was within 10% of Pao. This compared well to positive pressure occlusion test using abdominal pressure performed after paralysis, where Apes was within 10% of ΔPao in 10 animals. In 9 of these pups occlusion tests were also performed by applying pressure on the rib cage, where ΔPes was within 10% of ΔPao in 6 animals. These results suggest that it is possible to perform accurate occlusion tests in paralyzed subjects by abdominal or rib cage compression with the airway occluded. Pediatr Pulmonol. 1994; 17:56–62. © 1994 Wiley-Liss, Inc.  相似文献   
84.
A marked proportion of primary care patients have mental disorders and problems that remain unrecognized by the patients and their general practitioners. There is furthermore a great variation in the physicians’ ability to detect mental disorders. The aim of the present study was to find out the overall prevalence of mental disorders among patients receiving primary health care. The material consisted of 1000 randomly selected adult patients attending primary care facilities in Turku. The mental disorders were assessed by using the Symptom Checklist (SCL-25) and by general practitioners. According to the SCL-25, one fourth of the sample had a mental disorder. Only two fifths of them could be identified by the general practitioners.  相似文献   
85.
Summary: Some of the properties of 4–bromobenzalde-hyde semicarbazone (compound IV), a prototype molecule of a new class of anticonvulsants, aryl semicarbazones, are described. Compound IV demonstrated activity in the maximal electroshock (MES) and subcutaneous pentylenetetrazol (scPTZ) tests in mice, with low neurotoxicity. When given orally to rats, it displayed high potency in the MES test and very low neurotoxicity, resulting in a high protective index (PI). Compound IV displayed no proconvulsant properties, and development of rapid tolerance was not noted. When administered intraperitoneally (i.p.) at doses of 100, 300, or 600 mg/kg to rats, compound IV had no effect on levels of γ-aminobu-tyric acid (GABA) or on GABA-T activity in whole brain. When tested in vitro, compound IV had no effect on rat brain GABA-T at a drug concentration of 100 μM. Although the activities of certain drug-metabolizing enzymes were increased after oral administration of compound IV to rats, these effects were less prominent than those of phenytoin (PHT) and carbamazepine (CBZ). The principal mode of action of compound IV does not appear to be an interaction with the GABAA receptor complex, and other mechanisms, involving excitatory amino acid neurotransmission, will have to be considered in future investigations of the anticonvulsant activity of this compound.  相似文献   
86.
The characteristics of all the paediatric admissions made to a district general hospital over a three-year period were analysed in this study. Paediatric admissions averaged 23 per year (10% of the total admissions to the unit over that time). The mean age was six years, median age was four years. Sixty-two per cent were medical admissions and 38% surgical. Forty-seven per cent of the surgical admissions involved head injuries. Seventy-four per cent of medical admissions were directly related to upper and lower airway problems. Mean total admission time was six days, with a median of two days. Fifty-nine per cent (40) of all cases required intubation for a mean period of five days (median = three days). All cases were PRISM scored (Pollack, Ruttimann & Getson 1988). The mean score was 8. Ninety-four percent of admissions surviving to go home. There were a total of four deaths over the three-year period. The PRISM scores of those who died had a mean of 30, which was significantly different (P < 0.05) from the survivors who had a mean PRISM score of six and a median of four. The organs of one of the nonsurvivors were transplanted. Currently there is considerable interest in the feasibility of transferring all paediatric intensive care patients to a regional centre, the consequences of such a policy must be carefully assessed if its implementation is to be a success.  相似文献   
87.
Abstract Economic factors in diagnosis and treatment planning in periodontology may be considered from several points of view. A first perspective is that of government responsibility. Because of the explosion in health care expenditure in the last decade, public funding of dental care programmes may become static or even reduced. Most governments try to curb the ever growing public health expenditure. Consequently, terms like effectiveness, efficiency and accountability are now becoming common words also in relation to periodontal health care. Moreover, private insurance companies, which have entered this area, may be individual patient who, explicitly or implicitly, would like to consider the services individual patient, who explicitly or implicitly, would like to consider the sendees rendered in periodontal therapy and prevention as cost-effective. Features of supply of and demand for care on an individual basis should also be considered. Finally, the periodontist or general practitioner has to consider economic factors. In professional life, there should be a balance between good working conditions providing satisfactory care, and the demands and priorities of individual patients and the community at large.  相似文献   
88.
The effect of acute and sequential volaemic changes on the gastroduodenal flow of saline was assessed in 23 anaesthetized dogs following two different experimental protocols. Hypervolaemia, by i. v. infusion of saline, induced a gradual decrease on gastroduodenal flow which amounted to 76% below control values (P < 0.001) when volaemic expansion attained 5% of body weight. This effect was volume dependent (17% increase on gastroduodenal flow per volume of infused saline equivalent to 0.5% of body weight, P < 0.001), lasted for at least 90 minutes after infusion was completed and was also obtained by expanding previously bled animals. Hypovolaemia due to bleeding was followed by an increase on gastroduodenal flow of about 88% above control values (P < 0.05) when haemorrhage was equal to 3% of body weight. This effect was also volume dependent (23 % increase on gastroduodenal flow per volume of blood shed equivalent to a 0.5% of body weight, P < 0.01) and was reversed after blood volume was restored. These modifications in the resistance of the gastroduodenal segment to the flow of liquid due to acute volaemic changes suggest that the extracellular fluid volume modulates the contractile activity of the gastroduodenal portion of the gut possibly to set a gastroduodenal handling of liquid adequate to cope with volaemic imbalances.  相似文献   
89.
AIMS: Metabolic responses to manipulation of the plasma free fatty acid (FFA) concentration were assessed in six healthy men via cross-over design to determine whether FFAs independently influence insulin sensitivity. METHODS: Intramyocellular lipid (IMCL) was measured by proton magnetic resonance spectroscopy and insulin sensitivity via frequently sampled intravenous glucose tolerance test (IVGTT) after 67 h of two identical low carbohydrate/high fat (LC) diets which were used to elevate IMCL and plasma FFAs. To uncouple the influence of FFAs and IMCL on insulin sensitivity, FFAs were suppressed 30 min prior to and during IVGTT in one treatment [LC + nicotinic acid (NA)] by NA ingestion. RESULTS: Vastus lateralis IMCL was significantly elevated in LC (13.3 +/- 1.1 x 10(-3)) and LC + NA (13.5 +/- 1.1 x 10(-3)) (P < 0.01 for both), but was not different between conditions (P > 0.05). Plasma FFAs were raised in LC (0.79 +/- 0.08 mmol/l) and LC + NA (0.80 +/- 0.11 mmol/l) (P < 0.01 for both) and were significantly reduced by NA ingestion prior to (0.36 +/- 0.05 mmol/l, P < 0.01) and during IVGTT (P < 0.05) in LC + NA. Despite marked differences in plasma FFA availability, insulin sensitivity and glucose tolerance were not different between LC and LC + NA (P > 0.05 for both). CONCLUSIONS: Plasma FFAs appear to exert no immediate effect on insulin sensitivity/glucose tolerance independent of their action on intracellular lipid moieties. Further research is required to elucidate the duration of FFA suppression required to restore insulin sensitivity following lipid-induced insulin resistance.  相似文献   
90.
Pulsed Nd-YAG laser irradiation of bacteria has been suggested as a possible means of treating contaminated intra-oral sites although relatively few studies have been conducted. In this investigation, the antimicrobial activity of a pulsed Nd-YAG laser was assessed in vitro for a range of oral bacteria using several pulse energies and exposure durations. Pure cultures of each organism were lased in saline suspensions followed by standard colony counting techniques for test and control samples. Microbial inhibition was found to be organism-dependent and varied with energy dose and pulse energy. For all nine test species 120-mJ laser pulses proved more efficient than 80-mJ pulses, with 99.9% kills compared with around 90% kills after exposure to 1800 pulses. These killing activity levels compare favourably with those achieved with other lasers in vitro.  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