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   62238篇
  免费   4454篇
  国内免费   2108篇
耳鼻咽喉   499篇
儿科学   1321篇
妇产科学   2351篇
基础医学   8120篇
口腔科学   1337篇
临床医学   5161篇
内科学   6575篇
皮肤病学   894篇
神经病学   4458篇
特种医学   1744篇
外国民族医学   8篇
外科学   4618篇
综合类   9399篇
现状与发展   3篇
一般理论   6篇
预防医学   5428篇
眼科学   1725篇
药学   7329篇
  67篇
中国医学   4703篇
肿瘤学   3054篇
  2024年   163篇
  2023年   854篇
  2022年   1491篇
  2021年   2114篇
  2020年   1950篇
  2019年   1912篇
  2018年   1855篇
  2017年   1838篇
  2016年   1828篇
  2015年   1767篇
  2014年   3374篇
  2013年   4293篇
  2012年   3388篇
  2011年   3831篇
  2010年   3114篇
  2009年   2828篇
  2008年   2797篇
  2007年   2872篇
  2006年   2596篇
  2005年   2388篇
  2004年   2074篇
  2003年   2032篇
  2002年   1605篇
  2001年   1522篇
  2000年   1277篇
  1999年   1218篇
  1998年   1048篇
  1997年   1032篇
  1996年   928篇
  1995年   921篇
  1994年   803篇
  1993年   676篇
  1992年   598篇
  1991年   535篇
  1990年   537篇
  1989年   467篇
  1988年   336篇
  1987年   299篇
  1986年   336篇
  1985年   462篇
  1984年   425篇
  1983年   262篇
  1982年   338篇
  1981年   269篇
  1980年   291篇
  1979年   213篇
  1978年   180篇
  1977年   167篇
  1976年   155篇
  1975年   112篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
The localization of CGRP mRNA in neurons of the rat brain and spinal cord was assessed by in situ hybridization histochemistry (ISH) using a radiolabeled synthetic 57-mer oiigodeoxynucleotide probe complementary to the rat prepro CGRP mRNA. Results were compared with previously published findings of CGRP-immunoreactive (CGRP-IR) cell bodies revealed by an indirect immunofluorescence technique. The highest numbers of CGRP mRNA expressing neurons as well as the greatest intensity of staining were found in the lateral hypothalamic area, the parabrachial nuclei, and among the cranial motor nuclei, especially in the nuclei of the 7th and 12th nerve and the ambiguus nucleus, which is generally in good agreement with findings assessed by immunocytochemistry (ICH). However, some mismatches between the localizaton of the peptide by ICH and the localization of the CGRP mRNA were also observed. Thus, ISH was not able to confirm CGRP-IR in cells of the amygdaloid complex and parts of the medial hypothalamus, the central gray, and the inferior colliculus, but ISH revealed considerably more CGRP mRNA expressing cells in the lateral hypothalamic area, arcuate nucleus, posterior and peripeduncular thalamic nuclei, and all cranial motor nuclei than CGRP-IR containing cells found by ICH. Moreover, ISH also revealed CGRP mRNA synthesis in the nucleus of the lateral olfactory tract and in the perihypoglossal nuclei that were devoid of CGRP-IR. The reasons for the observed mismatches still remain to be elucidated; however, intracerebroventricular colchicine pretreatment used to increase immunocytochemical signals also might have induced or suppressed gene expression in certain brain regions in an unpredictable matter. On the other hand, detection of only the mRNA in a certain region does not necessarily mean that also the active peptide is synthesized there.  相似文献   
72.
豚鼠耳蜗微血管内皮细胞体外通透性的研究   总被引:1,自引:0,他引:1  
目的 研究豚鼠耳蜗微血管内皮细胞的体外通透性特征。方法 在成功建立豚鼠耳蜗微血管内皮细胞体外通透性模型的基础上 ,研究该体外模型跨细胞电阻及对12 5I 牛血清白蛋白的通透性。结果 ①耳蜗微血管内皮细胞在培养增殖过程中其跨细胞电阻呈动态变化过程 ,以 5× 10 4/cm2 的细胞密度接种时 ,7d左右电阻到达峰值 ,其跨细胞电阻峰值大小为 (118 9± 18 5 )Ω/cm2 ;②体外模型中加入12 5I 牛血清白蛋白后 ,其通透性呈上升期抛物线型曲线 ,90min内几乎呈直线。结论 跨细胞电阻及对12 5I 牛血清白蛋白变化曲线能反映体外耳蜗微血管内皮细胞的通透性特征  相似文献   
73.
With the advent of genomics, combinatorial paradigms and high-throughput screen (HTS)-based pharmacological testing, the number of compounds flowing through the discovery pipeline is likely to escalate. At the same time, with increased knowledge of the human drug-metabolizing enzymes and the availability of in vitro absorption-metabolism (AM) models, Preclinical Drug Metabolism is poised to meet the challenges of HTS. In order to be successful, however, a rational HTS strategy (vs. serendipitous HTS) has to be employed. Such a strategy is based on automation, validation and integration of in vitroAM models and database management (AVID). A generalized strategy for rational (AVID-based) HTS in Preclinical Drug Metabolism is described briefly.  相似文献   
74.
目的 研究透明质酸钠玻璃体腔内充填对严重开放性眼球损伤预后的影响。方法 在严重开放性眼球损伤一期手术缝合后玻璃体腔内充填透明质酸钠至眼压Tn。结果 用透明质酸钠在玻璃体腔内充填,眼球萎缩的发生率(6.67%)明显低于用BSS液充填的发生率(70.58%)。结论 透明质酸钠玻璃体腔内充填在严重开放性眼球损伤治疗中的应用对眼球外形维持和视功能恢复有重要作用。  相似文献   
75.
We examined changes in the expression of glial fibrillary acidic protein (GFAP) mRNA during Wallerian degeneration in the corticospinal system of the adult Golden hamster following axotomy. GFAP is the product of a type III intermediate filament (IF) gene that is expressed specifically in mature astrocytes. A well-studied component of a complex response termed reactive astrogliosis that occurs after various types of CNS injury is the increased production of astrocytic processes filled with GFAP-containing IFs. While increased expression of GFAP during reactive astrogliosis has been well established at the protein level, little is known about whether or not changes in GFAP mRNA levels occur after CNS injury. In the present study we used in situ hybridization methods to examine this issue. A 35S-labeled mouse GFAP cDNA probe was used for in situ hybridizations of sections of the brain stem obtained 2, 7, and 14 days after unilateral transections of the corticospinal tract in the caudal medulla. Film as well as emulsion autoradiography showed a dramatic increase in GFAP mRNA labeling associated with the degenerating corticospinal tract. GFAP mRNA levels were already dramatically increased in the injured corticospinal tract by 2 days post axotomy and remained elevated at 14 days. Interestingly, in addition to the robust increase in GFAP mRNA levels specifically associated with the degenerating tract, a diffuse increase in GFAP mRNA labeling was observed throughout the grey matter of the brain stem at 2 days post-axotomy, but not after this time. Immunoblotting and immunocytochemical experiments verified that the increased GFAP mRNA levels in the degenerating corticospinal system were accompanied by an increased expression of the protein. These results demonstrate that an increase in GFAP mRNA levels occurs during Wallerian degeneration in the CNS and suggest that increased expression of the GFAP gene is a major contributor to CNS scarring that results after direct traumatic injury.  相似文献   
76.
Galanin-like immunoreactivity has been visualized in nerve fibers in the islets of Langerhans, suggesting an involvement of galanin in the neural regulation of islet function. In this study, we investigated the effects of galanin on basal and stimulated insulin and glucagon secretion by infusing the peptide at three different dose rates in rats. We also studied the direct effect of galanin on insulin secretion from freshly isolated rat islets. At 320 pmol/kg/min, but not at 20 or 80 pmol/kg/min, galanin lowered basal plasma insulin levels. In contrast, basal plasma glucagon levels were lowered by galanin already at 20 and 80 pmol/kg/min. Furthermore, galanin inhibited both glucose- and arginine-induced insulin release at all three dose levels, whereas arginine-induced glucagon release was not affected by galanin. Glucose-stimulated insulin secretion from isolated rat islets was dose-dependently suppressed by galanin (10-6-10-8M). Therefore, it is concluded that galanin in rats inhibits insulin secretion, both in vivo and in vitro, and that at lower dose levels, the peptide also inhibits basal glucagon release.  相似文献   
77.
This article describes the association between previous infection and/or vaccination and the development of optic neuritis (ON) in 18 children. Ten of these children subsequently developed clinically definite multiple sclerosis (MS), while in 8 patients a clinically definite etiology could not be confirmed. Vaccination preceded the first ON attack in 6 patients, all but one of whom subsequently developed MS. It also preceded subsequent demyelinating events in 6 patients. Ten of the patients had a bacterial or viral infection within the 2 weeks prior to the first symptoms of ON. Intrathecal antibody synthesis against 2 or more viruses could be shown in 5 out of 8 patients studied; 5 out of 6 patients had oligoclonal antibodies in CSF and 12 out of 16 patients a high IgG index. Neither intrathecal antibody synthesis against 2 or more viruses nor elevated IgG indexes could be found in the control patients. Measles and mumps occurred at a significantly later age in the children who subsequently developed MS than in the control children, and these patients had significantly more events that might have impaired the blood-brain barrier than the controls. These results indicate that immunological events leading to MS may be triggered during childhood. Vaccination and infection often precede ON in childhood. Intrathecal viral antibody production can occur already in childhood at the time of the first symptoms of MS.  相似文献   
78.
目的建立人离体骨肉瘤血管亲和筛选模型。方法(1)建立模型。术前对患肢局部行数字减影造影检查,标记肿瘤固有动脉大致走行,术后小心修剪,并连接类似于Langendorff的灌流装置,监控模型血管内的pH值、温度、氧分压等;(2)对噬菌体十二肽库进行筛选。结果28例骨肉瘤离体标本均建模成功,可直接用于灌流实验,并筛选出具有较高特异性的亲和短肽(基序为RLTR),各项指标显示离体骨肉瘤较好模拟了人体内的环境。结论建立人离体骨肉瘤血管亲和筛选模型是可行的,可直接用于对噬菌体随机肽库的亲和筛选,为骨肉瘤的靶向化疗提供参考。  相似文献   
79.
分子生物学技术新进展   总被引:1,自引:0,他引:1  
分子生物技术的发展,衍生出DNA测序、DNA突变以及基因定位和克隆的各种方法.生物芯片则是当代生物技术的最新发展,它对基础研究以及在医学上对疾病分子的探索,开拓了临床新的诊断和治疗手段.该文就这些技术和发展趋势进行综述.  相似文献   
80.
A longitudinal survey (February 1984 - January 1985) on the incidence of acute diarrhea episodes in a sample of 8,164 children (aged 0–12 years) living in southeastern Sicily was carried out by means of weekly telephone interviews with doctors practising in the territory. The incidence rate was 0.479 (0.472–0.485 95% C.I.) per child per year and the frequency of episodes was significantly higher (p < 0.001) in children aged 0–4 years (0.86). Diarrhea was more frequent in industrial areas than in rural ones, and almost half (45.1%) of the total episodes had a mild course. No death from diarrhea occurred and admission to hospital was reported for 8.4% of all cases.Corresponding author.  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