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   5357篇
  免费   293篇
  国内免费   71篇
耳鼻咽喉   124篇
儿科学   41篇
妇产科学   31篇
基础医学   1291篇
口腔科学   465篇
临床医学   191篇
内科学   366篇
皮肤病学   89篇
神经病学   811篇
特种医学   184篇
外科学   506篇
综合类   411篇
预防医学   173篇
眼科学   499篇
药学   219篇
  2篇
中国医学   74篇
肿瘤学   244篇
  2023年   56篇
  2022年   111篇
  2021年   156篇
  2020年   101篇
  2019年   129篇
  2018年   129篇
  2017年   118篇
  2016年   123篇
  2015年   137篇
  2014年   198篇
  2013年   264篇
  2012年   161篇
  2011年   168篇
  2010年   143篇
  2009年   156篇
  2008年   190篇
  2007年   200篇
  2006年   161篇
  2005年   154篇
  2004年   147篇
  2003年   136篇
  2002年   94篇
  2001年   133篇
  2000年   122篇
  1999年   96篇
  1998年   94篇
  1997年   82篇
  1996年   92篇
  1995年   85篇
  1994年   122篇
  1993年   79篇
  1992年   109篇
  1991年   95篇
  1990年   110篇
  1989年   98篇
  1988年   115篇
  1987年   84篇
  1986年   65篇
  1985年   100篇
  1984年   65篇
  1982年   56篇
  1981年   61篇
  1980年   67篇
  1979年   70篇
  1978年   90篇
  1977年   72篇
  1976年   39篇
  1973年   46篇
  1972年   42篇
  1971年   40篇
排序方式: 共有5721条查询结果,搜索用时 109 毫秒
1.
2.
3.
目的了解7~14岁学龄期儿童前房深度发育情况。探索其与屈光度数间的关系。方法收集2012年6月至2014年6月眼科门诊7~14岁儿童为研究对象,共计521例(1042只眼)。采用IOLMaster人工晶状体生物测量仪测量各屈光参数,同时测量身高、体重。散瞳后验光测得静态屈光度。分析前房深度发育情况及不同屈光状态的学龄期儿童前房深度发育情况。结果(1)随着年龄的增长,7~14岁学龄期的儿童前房深度随之增长,差异具有统计学意义(P<0.01)。同一年龄段儿童的左右眼之间的均值相近,且生长发育趋势相近(均P>0.05)。(2)随着年龄的增长,男女的前房深度均逐渐增大,同一年龄段男性前房深度大于女性前房深度(均P<0.01)。(3)儿童前房深度与身高正相关(P<0.01)。(4)前房深度随近视度数增高而增大,低度近视组与中度近视组及高度近视组差异有统计学意义(P<0.05)。结论学龄期儿童的前房深度的发育受到身高、性别及屈光度数的影响,与身高呈正相关,同一年龄段,男性前房深度大于女性。双眼前房深度发育同步。低中度近视的儿童前房深度增大。  相似文献   
4.
目的与方法 采用深刺和浅刺对丙酸睾酮所致前列增生症(BPH)大鼠模型进行干预,研究其作用殊同。结果 针刺组前列腺,膀胱指数明显小于模型组;形态学观察,针刺组较模型组增生明显减轻,腺上皮呈单层柱状,腺体数目明显减少,间质充血,钙化明显减轻,结缔组织无增生,腺腔内分泌物减少。深刺组好于浅刺组。结论 深刺对实验性BPH大鼠的干预作用好于浅刺方法。  相似文献   
5.
Degeneration of neurons in the central nervous system is associated with morphological changes. Previous observations made at the light microscopical level indicated degeneration of serotonin-immunoreactive (IR) fibers in the aged rat brain. In this study, a comparison at the ultrastructural level was made between serotonin-IR normal thin and aberrant swollen varicose fibers in the caudate-putamen complex of the aged rat. Ultrastructural features such as the size and content of the thin varicose fibers resembled those in the caudate-putamen complex of the young rat as reported by others. The aberrant profiles were swollen, reaching a size of 6 microns. Their vesicles varied in size and were no longer uniformly round. Moreover, distorted mitochondria and membrane-filled vacuolelike structures were a common feature of the aberrant profiles. These changes are indicative of a degenerative process and give further evidence that, whereas many serotonergic fibers are preserved at high age, other serotonergic fibers are degenerating in the caudate-putamen complex of the aged rat.  相似文献   
6.
Contradictory results have been reported about the inhibitory input to the medial rectus subdivision of the oculomotor nucleus of the cat. In the present ultrastructural study, we quantified the GABAergic and glycinergic terminals in the various subdivisions of the rabbit oculomotor nucleus with the use of post-embedding immunocytochemistry combined with retrograde tracing of horseradish peroxidase. The density of the GABAergic input to the medial rectus subdivision was as substantial as that to the other subdivisions and the postsynaptic distribution of the GABAergic and glycinergic innervation did not differ among the different oculomotor subdivisions.  相似文献   
7.
报告105例Duchenne型肌营养不良症(DMD),其中男103例,女2例。年龄4~19岁,平均65岁。32例有阳性家族史。文中对DMD的临床表现,血清酶、肌肉病理、组织化学、电镜检查等特点进行了讨论。对其中4例骨骼肌进行肌纤维膜冷冻断裂电镜检查。结果表明,本病肌膜的E面和P面的膜蛋白颗粒密度降低,与2例正常骨骼肌相比有显著性差异,支持本病发病机理中的“膜缺陷”学说。  相似文献   
8.
Masumi Ichikawa   《Brain research》1987,420(2):253-258
The rearrangement of terminations from the bed nucleus of stria terminalis (BST) was examined in the medial amygdaloid nucleus (MAN) at 2 months following the lesion of the accessory olfactory bulb (AOB) using an electron microscopy and degeneration study. At 2 days following a BST lesion, the number of degenerating synapses was 0.7 ± 0.1 (mean±S.E.M.) per unit area (2500 μm2 in the molecular layer, and 3/0 ± 0.3 in the cellular part. At 2 months after an AOB lesion, the degenerating synapses from the AOB had completely disappeared from the MAN. The BST was then lesioned at 2 months after the AOB lesion and, 2 days following this BST lesion, the degenerating synapses were counted in MAN. The numbers observed were 3.3 ± 0.6 per unit area in the molecular layer and 4.5 ± 0.4 in the cellular part. Therefore, the number of these degenerating synapses increased significantly within the molecular layer, though, in the cellular part the number of synapses was not significantly elevated over control. No differences in postsynaptic profiles (ratio of synapses on dendritic spine to dendritic shaft) were observed after the AOB lesion. These results indicate that the BST fibers formed new synapses in the molecular layer following the denervation of AOB fibers. The possibility of new synapse formation by other afferent fibers in addition to the AOB fibers is discussed as is the relationship between lesion induced synaptic reorganization and functional recovery after injury.  相似文献   
9.
Summary The histogenesis of stromal cells in capillary hemangioblastoma has been the subject of debate. The light and electron microscopic studies of hemangioblastomas presented here showed pericytic and leiomyoblastic features in stromal cells. Cells cultured by the monolayer method showed similar features to those of the original tumors. Immunohistochemical studies for glial fibrillary acidic protein and factor VIII/von Willebrand factor indicated that stromal cells were antigenically distinct from astrocytes and endothelial cells. These findings suggest that stromal cells are closely related to pericytes and smooth muscle cells, and support Rhodin's speculation that pericytes serve as a precursor to smooth muscle cells.  相似文献   
10.
We describe a 54-year-old woman with primary pulmonary adenocarcinoma showing a characteristic papillary architecture and prominent cilia formation. Immunohistochemically, the tumor cells were positive for carcinoembryonic antigen (CEA), epithelial membrane antigen (EMA) and Leu Ml, and negative for lactoferrin and surfactant apoprotein. An ultrastructural study also indicated differentiation toward bronchial surface epithelial cells. To our knowledge, this type of neoplasm has not been reported as peripheral-type adenocarcinoma of the lung. Acta Pathol Jpn 42: 745–750, 1992.  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