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   8677篇
  免费   1039篇
  国内免费   268篇
耳鼻咽喉   50篇
儿科学   135篇
妇产科学   90篇
基础医学   664篇
口腔科学   245篇
临床医学   682篇
内科学   910篇
皮肤病学   96篇
神经病学   481篇
特种医学   208篇
外国民族医学   1篇
外科学   514篇
综合类   1300篇
预防医学   2887篇
眼科学   164篇
药学   822篇
  3篇
中国医学   258篇
肿瘤学   474篇
  2024年   27篇
  2023年   143篇
  2022年   236篇
  2021年   387篇
  2020年   388篇
  2019年   303篇
  2018年   321篇
  2017年   337篇
  2016年   372篇
  2015年   335篇
  2014年   513篇
  2013年   642篇
  2012年   501篇
  2011年   534篇
  2010年   407篇
  2009年   402篇
  2008年   414篇
  2007年   439篇
  2006年   377篇
  2005年   320篇
  2004年   332篇
  2003年   246篇
  2002年   219篇
  2001年   201篇
  2000年   157篇
  1999年   168篇
  1998年   144篇
  1997年   114篇
  1996年   102篇
  1995年   88篇
  1994年   88篇
  1993年   91篇
  1992年   112篇
  1991年   86篇
  1990年   81篇
  1989年   71篇
  1988年   66篇
  1987年   32篇
  1986年   32篇
  1985年   42篇
  1984年   19篇
  1983年   19篇
  1982年   21篇
  1981年   6篇
  1980年   13篇
  1979年   8篇
  1978年   7篇
  1977年   7篇
  1976年   4篇
  1974年   3篇
排序方式: 共有9984条查询结果,搜索用时 15 毫秒
81.
本文报告了湘西吉首地区1159名3~6岁幼儿(男640,女519)的身长和胸骨长的均值,身长与胸骨长的比值,身长胸骨长指数;对胸骨长与身长两者之间进行了相关和回归分析,并提出了由胸骨长推算身长的回归方程.  相似文献   
82.
BACKGROUND: The evaluation and interpretation of the results from blood tests measuring specific immunoglobulin E (IgE) antibody concentration is currently made using the dichotomized result from the test despite a quantitative result is obtained. It has been shown that different levels of IgE antibodies, assessed by blood test and skin prick test, may have a relation to presence of symptoms, implying that there is more information in a quantitative result than in the dichotomous--positive or negative. OBJECTIVE: To investigate the clinical utility of quantification of IgE antibodies in the diagnosis of allergic patients and whether such procedure has any advantage to the presently dichotomously used sensitivity and specificity at a fixed cut-off. METHODS: Data from a previously published study (R. Paganelli, I.J. Ansoteugi, J. Sastre, C.-E. Lange, M.H.W.M. Roovers, H. de Groot, N.B. Lindholm, P.W. Ewan, Allergy, 1998; 53) analysing diagnosis of allergic patients in four different clinics were re-evaluated. In the original study consecutive patients with suspected IgE-mediated allergy had been examined and evaluated according to the clinical routine at each clinic, using case history, physical examination, skin tests and laboratory tests, except the test to be evaluated, and given a "doctors' allergen-specific diagnosis" as positive or negative. In the present study the relation between "doctors' allergen-specific diagnosis", expressed as pos/neg, and the quantitative levels of specific IgE antibody concentration was analysed using a logistic regression model. This presentation of results was also compared with the more common characteristics of sensitivity and specificity, and also with Receiver-operator characteristics (ROC) curves. RESULTS: The used logistic model described the relationship between allergen-specific diagnosis in each study and the levels of IgE antibodies. The shape of the curve illustrated the physicians' disposition for a positive diagnose in the study, in relation to the specific IgE antibody level. Differences in the shape of the curve was found both between allergens within clinics and between clinics for the same allergen. No association could be demonstrated between prevalence and shape of the curve. CONCLUSIONS: Conventional sensitivity/specificity figures or ROC concepts only use the qualitative statement of whether IgE is present or not. A risk assessment using the quantitative level of IgE antibody to an allergen increases the utility of the information in clinical context compared with a qualitative statement of whether IgE is present or not. The quantification demonstrated the link between specific IgE antibodies and allergic reactions. The use of objective, well performing quantitative tests should help improve diagnostic accuracy and might provide a way for the patient to understand and manage his or her daily situation and risk for reactions.  相似文献   
83.
独立成分分析是一种新的信号处理统计方法。被广泛用于各个领域。在信号分析中面临的难题是:源信号的不同特性(既包括超高斯信号又包括亚高斯信号);未知的独立源数目;传感器信号受到较大的加性噪声污染。针对以上难题,本文提出了一种独立成分分析的鲁棒算法。该方法先对观测数据作预处理,将包含噪声的高维传感器观测信号降维分解到信号子空间和噪声子空间。利用交叉验证法估计出独立源的数目(解决了独立成分分析本身不能确定源数目的缺陷);然后利用快速稳定的FastICA算法分离独立成分。通过人工合成的数据和实际的脑磁图数据分析。验证了这种方法的功效。  相似文献   
84.
Spontaneous histopathological regression of cancer has been reported. The involvement of the immune system in such regression has been advocated, leading to the theory of immunological surveillance against cancer. A prediction of this theory is that common tumour antigens can be recognized upon repeated exposure by cell-mediated immunity, which leads to tumour regression and the subsequent appearance of tumour antigen-loss variants. However, no direct evidence has been provided in non-viral-induced experimental animal models of primary malignancy or in human primary cancer. This study examined two groups of melanoma patients where histopathological regression of the primary tumour was observed. Many of the 23 patients with multiple (> or =3) primary melanomas showed significant regression of their last melanoma (median 33%, mean 40) compared with matched melanomas from patients with a single primary melanoma (median 0%, mean 12) (p=0.0080), or compared with their first primary melanoma (p=0.0013). Regression was consistent with an 'immunization effect' seen in murine tumour transplantation studies, where inoculation with > or =3 asynchronous tumours induces transplantation rejection on subsequent challenge. A significant decrease in the expression of the melanoma common tumour antigen MART-1 in the last primary tumour from multiple melanoma patients (median 8%, mean 24) versus matched single melanoma patients (median 79%, mean 68) (p=0.0041) and in the last versus first tumour in multiple primary patients was found (p=0.0083). Metastases from 17 patients whose primary skin melanomas had completely regressed (occult primary melanoma) also showed significant MART-1 loss (median 0%, mean 11) compared with matched metastases from patients with non-regressing primary melanoma (median 51%, mean 50) (p=0.0013). MART-1 antigen-loss variants observed in the multiple primary and occult primary patients correlated with the presence of peripheral blood MART-1-specific cytotoxic T lymphocytes (CTLs) (p=0.03). No similar effects were observed with two other melanoma antigens, gp100 and CD63. Thus, in two groups of human melanoma patients, evidence is provided for histopathological tumour regression associated with cancer immune surveillance.  相似文献   
85.
BACKGROUND: Environmental control has been put forward as an integral part of the management of house dust mite (HDM) allergy in sensitized patients. To validate this statement allergic disorders involved in HDM allergy--allergic asthma, rhinitis and atopic eczema/dermatitis syndrome (AEDS)--should be taken together and studied in terms of the efficacy of environmental control. Because a generic quality of life questionnaire exceeds the border of disease, this may be used as major outcome parameter. RESEARCH OBJECTIVE: To study the effects of bedding encasings in HDM allergic patients with asthma, rhinitis and AEDS. MATERIAL AND METHODS: A total of 224 adult HDM allergic patients with rhinitis and/or asthma and/or dermatitis were randomly allocated impermeable or nonimpermeable encasings for mattress, pillow and duvet. Short form 36 (SF-36) was filled in at baseline and after 12 months. Results: Lower physical (P = 0.01) and emotional (P < 0.001) sumscores were seen in females. Also, the presence of asthma resulted in lower physical sumscore (P = 0.01). However, no effect was seen of encasings on either sumscore. CONCLUSION: Bedding encasings do not improve quality of life in a mixed population of subjects with combinations with rhinitis, asthma and atopic dermatitis and sensitized to HDMs.  相似文献   
86.
Summary Psychotropic drug intake by a random sample of citizens of the city of Munich aged 30–69 years has been assessed. A 1-week prevalence of 9.3% for all psychotropic drug users was found, benzodiazepines accounting for approximately two-thirds (6.6%) of the users. Two-thirds of drug users were women. Drug use in both sexes increased with age. The doses of benzodiazepines prescribed in most cases were less than 10 mg diazepam equivalent per day. Intake of benzodiazepines in combination with analgesics or alcohol (40 g/day) did not appear to represent a major problem. Multiple logistic regression analysis showed that the number of chronic diseases was the strongest predictor of benzodiazepine intake in men, whereas stress and age determined intake in women. Long-term use seemed to be relatively rare at 11% of all benzodiazepine users, so it was not considered to be a severe public health problem.  相似文献   
87.
Radiographic quantification of alveolar bone level changes   总被引:3,自引:0,他引:3  
The "random burst" theory has recently been proposed as an explanation of the pattern of periodontal disease progression. The theory predicts that the progression of bone loss at individual sites is not dependent upon previous bone loss and age. A longitudinal radiographic study was designed to test this hypothesis, and to describe the changes in bone level over 2 years in a group of 180 subjects (18-68 years of age) who were not under systematic periodontal treatment. The results indicated that 94% of the sites did not show significant changes in the alveolar bone level during the observation period. The mean annual bone loss for the total population was 0.11 mm. By regressing longitudinal bone loss upon age, it was shown that the rate of bone loss increased rapidly between 33 and 56 years of age while a different pattern was shown for the age intervals 18-32 and 57-68 years. Also, the rate of bone loss increased with increasing initial bone loss. This was less evident in the oldest age group. It was concluded that the progression of bone loss in the present material is consistent with a "burst" theory. However, the progression did not occur randomly with regard to previous loss of alveolar bone and time.  相似文献   
88.
Previous studies have shown that xenobiotic compounds such as the environmental pollutant -hexa-chlorocyclohexane (-HCH) and the synthetic sex steroid cyproterone acetate (CPA) induce growth of rat liver by hypertrophy and hyperplasia. After withdrawal of the growth stimuli, liver hypertrophy was usually found to be readily reversible. Conflicting observations were made concerning the fate of liver hyperplasia: hepatic hyperplasia persisted when induced by -HCH but was found to be partially reversible when induced by CPA. The present study confirms the reversibility of hepatic hyperplasia induced by CPA in rats: about 30% of liver DNA present at maximal liver enlargement disappeared within 6 days after cessation of CPA treatment. Simultaneously, a dramatic increase in the rate of cell elimination by apoptosis was found. Glutamate-pyruvate transaminase and alkaline phosphatase in serum did not show major increases, suggesting that cell death was not due to lytic membrane damage. Furthermore, if treatment with CPA was continued or resumed, the enhanced DNA content persisted and the number of apoptotic bodies was greatly reduced. These observations suggest that the occurrence of cell death is due to withdrawal of the growth stimulus CPA. It may reflect a regulatory phenomenon serving to maintain homeostasis of cell number.Further studies showed that CPA is rapidly eliminated from rat liver and serum: t 1/2 in the liver is about 11 h. In contrast, -HCH was previously found to be eliminated more slowly: t 1/2 approximately 144 h. The present study revealed that -HCH, CPA and nafenopin lower the number of apoptotic bodies. This suggests that inducers of liver growth can inhibit hepatocellular death by apoptosis. It is concluded that the regression of hyperplasia after CPA withdrawal may be due to its rapid elimination. On the other hand the relatively long persistence of -HCH may result in inhibition of cell death and thereby stabilize hepatic hyperplasia.Abbreviations CPA cyproterone acetate - -HCH -hexachlorocyclohexane - PB phenobarbital - NAF nafenopin - AB apoptotic body - b.w. body weight - p. admin. post-administration - GPT glutamate-pyruvate transaminase - ALP alkaline phosphatase Dedicated to Professor W. Koransky on the occasion of his 65th birthday  相似文献   
89.
目的 探究血糖与性别之间的交互作用对噪声性听力损失(noise-included hearing loss, NIHL)的影响。 方法 采用病例对照研究,询问调查噪声作业工人一般资料、职业史、既往史等资料以及职业健康监护资料,进行单因素分析,然后采用logistic回归模型分析NIHL的影响因素,再进行乘法交互作用分析。 结果 调查的1 628例噪声作业工人NIHL 616人(37.84%),NIHL的危险因素有血糖偏高(OR=1.960,95%CI:1.345~2.855)、男性(OR=4.346,95%CI:2.866~6.590)、高环境噪声强度(OR=1.036,95%CI:1.016~1.056)、单核细胞计数偏高(OR=8.522,95%CI:3.054~23.776)、血小板偏低(OR=0.997,95%CI:0.994~0.999)。血糖偏高人员的NIHL风险是血糖正常的1.960倍(P<0.01),男性NIHL的风险是女性的4.346倍(P<0.01),环境噪声强度每增加一个单位,NIHL风险提高1.036倍。血糖偏高与男性对NIHL的加法交互作用有统计学意义,两者同时存在时OR值为8.962,交互作用指数值为2.123。 结论 有必要考虑将空腹血糖检查纳入噪声作业人员常规检查项目,加强男性噪声作业工人血糖水平的监测,筛查出血糖偏高人群并给予一定的控制、干预,必要时调离工作岗位。  相似文献   
90.
周平  陈立 《中国儿童保健杂志》2022,30(11):1208-1211
孤独症谱系障碍(ASD)是一组以不同临床表现为主要特征的神经发育性障碍。近年来,ASD儿童的发育倒退(DR)受到越来越多的关注,并被认为可能是ASD的一种特殊亚型。目前关于ASD儿童DR的影响因素尚不清楚,综合文献分析主要是由遗传、环境及其交互作用共同引起。本文拟从遗传和环境两方面对目前报道的ASD儿童DR影响因素进行总结,为该部分ASD患儿的临床早期识别和干预提供参考。  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