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   125358篇
  免费   10034篇
  国内免费   3144篇
耳鼻咽喉   1353篇
儿科学   7284篇
妇产科学   3812篇
基础医学   13912篇
口腔科学   1743篇
临床医学   14084篇
内科学   21223篇
皮肤病学   2392篇
神经病学   10724篇
特种医学   2848篇
外国民族医学   3篇
外科学   11996篇
综合类   17836篇
现状与发展   16篇
预防医学   7216篇
眼科学   2264篇
药学   6598篇
  68篇
中国医学   11193篇
肿瘤学   1971篇
  2024年   254篇
  2023年   2169篇
  2022年   3470篇
  2021年   6178篇
  2020年   5660篇
  2019年   4504篇
  2018年   4540篇
  2017年   4648篇
  2016年   4748篇
  2015年   4508篇
  2014年   8807篇
  2013年   9124篇
  2012年   7135篇
  2011年   8257篇
  2010年   6417篇
  2009年   6194篇
  2008年   6023篇
  2007年   6123篇
  2006年   5562篇
  2005年   4584篇
  2004年   3902篇
  2003年   3452篇
  2002年   2398篇
  2001年   2182篇
  2000年   1872篇
  1999年   1724篇
  1998年   1421篇
  1997年   1335篇
  1996年   1284篇
  1995年   1250篇
  1994年   1050篇
  1993年   947篇
  1992年   850篇
  1991年   661篇
  1990年   609篇
  1989年   509篇
  1988年   512篇
  1987年   454篇
  1986年   396篇
  1985年   521篇
  1984年   423篇
  1983年   264篇
  1982年   343篇
  1981年   310篇
  1980年   252篇
  1979年   208篇
  1978年   130篇
  1977年   101篇
  1976年   88篇
  1975年   39篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
抗SARS病毒N蛋白单克隆抗体的制备和初步应用   总被引:2,自引:0,他引:2  
目的 制备抗SARS病毒N蛋白的单克隆抗体并研究其初步应用。方法 用基因重组N蛋白免疫小鼠,取免疫后的鼠脾细胞与骨髓瘤细胞融合,筛选分泌抗SAPS病毒N蛋白单克隆抗体细胞株。将阳性细胞株接种小鼠腹腔制备单克隆抗体腹水并对抗体进行纯化,分析纯化抗体的相对亲和力。选择亲和力较高的抗体制备检测SARS病毒抗原的酶联免疫诊断试剂,并对其敏感性和特异性进行分析。结果 共获得11株单克隆抗体细胞株,其中3株单抗与N蛋白具有较高的亲和力,4株纯化单抗与N蛋白反应很弱,其余4株单抗介于两者之间。用亲和力较高的单抗制备检测SARS病毒抗原的诊断试剂,其敏感性可达31PFU/ml,而且与其他呼吸道病毒无交叉反应。结论 该试剂特异性较好,可用于SARS病毒抗原的检测,其敏感性仍需用临床急性期样品进行评价。  相似文献   
992.
Fryns JP, Vogels A, Decock P, Van den Berghe H. The hand-foot-genital syndrome: on the variable expression in affected males.
Clin Genet 1993: 43: 232–234. © Munksgaard, 1993
In this report we document male-to-male transmission in the hand-foot-genital syndrome. An affected father transmitted the syndrome to his three sons. A grade IV hypospadias, which was the most severe genital anomaly in affected males, was present in the youngest, moderately mentally retarded microcephalic male sibling.  相似文献   
993.
During the past three years, an epidemic of acquired immunodeficiency syndromes (AIDS) involving the presence of specific forms of cancer (notably Kaposi's sarcoma) and infection (e.g., pneumocystis carinii) ordinarily seen only in severely immunosuppressed hosts has occurred among active homosexuals, Haitian immigrants, drug users, and hemophiliacs in large cities in the United States and elsewhere. An as yet unidentified viral agent is presumably the cause of the initial immunodeficiency and host genetic factors may influence the subsequent development of different clinical symptoms in different patients. We have previously reported that the HLA antigens DR5 and DR2 are associated with susceptibility to Kaposi's sarcoma (KS) in different Caucasian subpopulations. We now have also noted that AIDS patients with opportunistic infections have a normal frequency of DR2 and DR5 and a significantly increased frequency of DR3 and that the ultimate clinical expression of AIDS in patients with unexplained lymphadenopathy may depend upon genetic factors associated with these particular DR types.  相似文献   
994.
The mechanism of hyperlipidaemia in the nephrotic syndrome has not been fully established. We propose that it results from hypoalbuminaemia due to inhibition of the reaction catalysed by lecithin cholesterol acyltransferase converting cholesterol of high density lipoproteins to cholesterol esters and to an inhibition of high density lipoprotein particle formation from very low density lipoproteins due to reduced activity of lipoprotein lipase.  相似文献   
995.
A luminescence-microscopic study using acridine orange with a short-term culture of human cells showed that DNA melting profiles of the chromatin of intact lymphocytes of healthy donors are curves with maxima (F 530) in the temperature regions of 45, 65, 78, 85, 88, and 92°C (P<0.01). The melting profiles of lymphocytes of patients with Down's syndrome are curves with maxima in the temperature regions of 65, 85, 88, and 92°C (P<0.01). The absence of a decrease in the intensity of fluorescence between 78 and 85°C is evidently due to the greater degree of condensation of certain regions of the chromatin complex of the trisomic cells. The possible mechanisms of the structural changes in the interphase chromatin, of human lymphocytes under the influence of temperature are discussed.Institute of Medical Genetics, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Yudaev.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 6, pp. 672–674, June, 1976.  相似文献   
996.
目的 研究大鼠脾气虚胃溃疡证病结合模型中回肠5-羟色胺 (5-HT)及其受体(5-HTR)、细胞因子IL-2、IL-6的变化,探讨脾虚胃溃疡的发病机制及加味四君子汤治疗脾虚证的机理.方法 采用免疫组织化学技术、图像分析、放射免疫和免疫印迹法.结果 大鼠脾气虚合并胃溃疡模型中5-HT阳性细胞主要分布于回肠黏膜上皮及肠腺细胞;5-HTR免疫反应阳性的细胞主要位于肠绒毛及腺体间结缔组织,在肠壁平滑肌、肌间神经丛也有表达;5-HT及其受体免疫反应阳性产物的含量均增加,免疫印迹法示回肠5-HTR含量增加,且随病程进展,而进一步升高;经过加味四君子汤治疗后,上述异常变化得到纠正.在造模初期,IL-2、IL-6的分泌活性增加,随着脾虚胃溃疡发病的进一步发展,IL-2、IL-6的分泌活性降低.结论 大鼠脾气虚胃溃疡模型中回肠组织5-HT及其受体含量的增高,是大鼠脾虚胃溃疡发病的机理之一,加味四君子汤能通过纠正这些变化而发挥治疗作用.IL-2、 IL-6分泌活性的改变可能与大鼠脾虚胃溃疡的病程发展相关.  相似文献   
997.
Head circumference is considered an important parameter of brain growth and development. Syndrome-specific standards for head circumference in Williams-Beuren syndrome (WBS) are not available to date, although mental retardation is a leading manifestation in the syndrome. Therefore, we investigated head growth in 63 girls (251 measurements) and 88 boys (298 measurements) with WBS between birth and adulthood. Most measurements in both sexes were from the first 4 years of life (n = 162 in girls and n = 189 in boys). Mean (±SD) head circumference at birth was 33.39 ± 1.38 cm and 34.02 ± 1.44 cm for term girls and boys, respectively. Although head growth in WBS girls and boys was at a slower velocity, the pattern of head circumference was similar to that in the normal population. After the age of 3 months, head circumference started to fall below the normal mean in girls (0.5–2 cm). In boys, mean head circumference was below the normal mean already at 1 month of age (2 cm). The deficit increased to 3 cm from 6 months to 4 years. Adult OFC was 52.85 ± 1.75 cm (n = 16) compared to 55.70 ± 1.83 cm (n = 46; P < 0.00001) in WBS women and 55.51 ± 1.68 cm (n = 30) compared to 57.87 ± 1.29 cm (n = 31; P < 0.00001) in WBS men. During development, microcephaly is only seen in about one third of WBS patients. © 1994 Wiley-Liss, Inc.  相似文献   
998.
Seventy-four families of probands with oculoauriculovertebral anomaly were evaluated, including 116 parents and 195 off-spring. Relatives were examined to identify ear malformations, mandibular anomalies, and other craniofacial abnormalities. For segregation analysis using POINTER, selection of the sample was consistent with single as-certainment. Different population liabilities were used for probands and relatives, because affection was narrowly defined for probands and broadly defined for relatives. The hypothesis of no genetic transmission was rejected. The evidence favored autosomal dominant inheritance; recessive and polygenic models were not distinguishable. © 1992 Wiley-Liss, Inc.  相似文献   
999.
Recent reports have suggested that variants in the sortilin-related receptor gene (SORL1) increase the risk of late onset Alzheimer's disease (AD) in Northern European, Hispanic, African–American and Isreali–Arab populations. SORL1 directs trafficking of amyloid precursor protein (APP) and under-expression of SORL1 may lead to over-expression of β amyloid peptides. Adults with Down syndrome (DS) over-express APP and have early onset and high risk for AD. We investigated the relation of seven variants in the gene for SORL1 to age at onset and risk for AD among 208 adults with DS, 45–70 years of age at baseline. Participants were ascertained through the New York State developmental disability service system and followed at 18-month intervals. Information from cognitive assessments, caregiver interviews, medical record review and neurological examination was used to establish the diagnosis of dementia. Homozygosity for the minor T allele in rs556349 and for the minor C allele in rs536360 was associated with later age at onset and reduced risk of AD (HR = 0.26, 95% CI: 0.08–0.86; and HR = 0.40, 95% CI: 0.16–0.98, respectively). Mean age at onset was approximately four years later in individuals who were homozygous for those alleles compared with those who had at least one major allele. These findings indicate a modest association of variants in SORL1 with AD. In addition, we did not observe the same alleles to be associated with AD compared with earlier studies, suggesting that these SNPs are in linkage disequilibrium (LD) with the putative functional variants or that expression of the SORL1 gene and hence its interaction with APP might be modified by the extremely high levels of APP characteristic of Down syndrome. Thus, further studies are needed to identify functional variants that influence risk for AD in this uniquely vulnerable population.  相似文献   
1000.
Cystic fibrosis (CF) is an autosomal recessive disorder with a prevalence at birth estimated at 1/2000-1/2500 livebirths in Caucasian populations. Some 127 CF individuals are known in Saguenay-Lac-St-Jean (SLSJ), a geographically isolated region of Quebec. The prevalence at birth was estimated at 1/902 live borns, and the carrier rate was estimated at 1/15 inhabitants in the SLSJ region. The mean inbreeding coefficient was only slightly elevated in the CF group compared with three control groups, and was due to remote consanguinity. The mean kinship coefficient was 2.4 times higher in the CF group than in the control groups. In SLSJ region, the places of origin of the CF individuals and their parents did not show a clustered nonuniform distribution. Endogamy was not higher in the CF group than in control groups.  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