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   106742篇
  免费   9138篇
  国内免费   4672篇
耳鼻咽喉   1454篇
儿科学   1308篇
妇产科学   1689篇
基础医学   15460篇
口腔科学   2442篇
临床医学   10886篇
内科学   19097篇
皮肤病学   1791篇
神经病学   7011篇
特种医学   4380篇
外国民族医学   27篇
外科学   13257篇
综合类   10136篇
现状与发展   14篇
一般理论   10篇
预防医学   6103篇
眼科学   2665篇
药学   10218篇
  38篇
中国医学   3177篇
肿瘤学   9389篇
  2024年   181篇
  2023年   1062篇
  2022年   2447篇
  2021年   3558篇
  2020年   2528篇
  2019年   2617篇
  2018年   3135篇
  2017年   2683篇
  2016年   2669篇
  2015年   3600篇
  2014年   4326篇
  2013年   4537篇
  2012年   6387篇
  2011年   6575篇
  2010年   4028篇
  2009年   3447篇
  2008年   4767篇
  2007年   4806篇
  2006年   4488篇
  2005年   4020篇
  2004年   3215篇
  2003年   3028篇
  2002年   2680篇
  2001年   5690篇
  2000年   5605篇
  1999年   5009篇
  1998年   1976篇
  1997年   1585篇
  1996年   1074篇
  1995年   920篇
  1994年   827篇
  1993年   627篇
  1992年   2271篇
  1991年   1942篇
  1990年   1782篇
  1989年   1714篇
  1988年   1503篇
  1987年   1367篇
  1986年   1208篇
  1985年   1005篇
  1984年   657篇
  1983年   528篇
  1982年   274篇
  1981年   212篇
  1980年   159篇
  1979年   315篇
  1978年   98篇
  1976年   98篇
  1974年   100篇
  1973年   113篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
目的探讨欧乃影在临床应用中不良反应的发生和预防措施。方法观察2003年10月至2006年7月所作1000例增强扫描者静脉注射欧乃影0.2mL/kg(其量浓度(c)为0.5mol/L)后,不良反应发生的情况。结果1000例患者中,出现不良反应6例,其中,非过敏反应3例,轻度过敏反应3例,无中度及重度过敏反应。结论欧乃影在磁共振增强扫描中不良反应发生率低,临床应用安全。  相似文献   
102.
103.
104.
OBJECTIVE: Studies exploring chronic alcoholism with event-related potentials (ERPs) have shown delayed latency and reduced amplitude of the P300, a long-lasting positive potential reflecting decisional processing. This P300 deficit in alcoholism is generally interpreted as a disturbance in central nervous system inhibition or in memory/attention. The present study aimed at identifying if this electrophysiological deficit is already present on earlier components, and advances a new hypothesis concerning the interpretation of the P300 alteration. METHODS: Patients suffering from alcoholism and matched healthy controls had to detect, in an oddball paradigm, emotional faces among a succession of neutral faces. Behavioral performance and ERP data (recorded from 32 electrodes) were analyzed. RESULTS: In line with previous studies, data showed that alcoholism led to a P300 deficit. Moreover, we observed for the first time that this deficit begins at earlier visual (P100) and face-processing (N170) stages, and we found high positive correlations between P100, N170 and P300 for amplitude and latency values, suggesting cumulative deficits on the cognitive continuum. CONCLUSIONS: We suggest that the P300 deficit observed in chronic alcoholism could be linked to earlier visuo-spatial deficits rather than being an impairment of the specific processes linked to the P300. SIGNIFICANCE: These results call for reconsidering the interpretation of P300 impairments at a fundamental and clinical level, and shows that earlier ERP components must be taken into account in future studies.  相似文献   
105.
In this paper, we address the problem of stable tracking control of a flexible macro-micro manipulator (M(3)) system. A two-layer neural network is utilized to approximate the nonlinear robot dynamic behavior of the M(3) system, and the controllers for the macro and micro arms are developed without any need for prior knowledge of the dynamic model of the controlled M(3) system. A learning algorithm for the neural network using Lyapunov stability theory is derived. It is shown that both the tracking error and the weight-tuning error are uniformly ultimately bounded under this new control scheme. Simulation results are presented and compared to those obtained using a PD controller.  相似文献   
106.
The present study was designed to detect three single nucleotide polymorphisms (SNPs) located on 22q11 that was thought as being of particularly importance for genetic research into schizophrenia. We recruited a total of 176 Chinese family trios of Han descent, consisting of mothers, fathers and affected offspring with schizophrenia for the genetic analysis. The transmission disequilibrium test (TDT) showed that of three SNPs, rs10314 in the 3'-untranslated region of the CLDN5 locus was associated with schizophrenia (chi(2) = 4.75, P = 0.029). The other two SNPs, rs1548359 present in the CDC45L locus centromeric of rs10314 and rs739371 in the 5'-flanking region of the CLDN5 locus, did not show such an association. The global chi-square (chi(2)) test showed that the 3-SNP haplotype system was not associated with schizophrenia although the 1-df test for individual haplotypes showed that the rs1548359(C)-rs10314(G)-rs739371(C) haplotype was excessively non-transmitted (chi(2) = 5.32, P = 0.02). Because the claudin proteins are a major component for barrier-forming tight junctions that could play a crucial role in response to changing natural, physiological and pathological conditions, the CLDN5 association with schizophrenia may be an important clue leading to look into a meeting point of genetic and environmental factors.  相似文献   
107.
In this case report, orthodontic intervention was used to move the gingival margin of a maxillary canine incisally by almost 9 mm to mimic a lateral incisor. Increasing the thickness of the labial plate of bone of the canine and subsequently increasing the thickness of the attached gingiva before extrusion prevented gingival recession at a later stage. In many situations, orthodontic treatment can achieve results that could not be attained by restorations and other means of cosmetic dentistry, especially when dealing with gingival margins and gingival height. A step-by-step approach to achieving these treatment objectives is described.  相似文献   
108.
109.
Several weeks after porcine retinal pigment epithelial (RPE) cell cultures attain confluence, macroscopically visible brown foci appear. The cuboidal cells that form the foci contain numerous phase dark granules that do not exhibit the autofluorescence characteristic of lipofuscin. The data described here indicate that the granules are melanosomes. Electron microscopy revealed three types of electron-dense granules in these cells: simple spheres 0.3-0.5 microns in diameter, large spheres 1-2 microns in diameter, and lysosomal aggregations of the smaller spheres. The matrix of both spheres is composed of 40-nm microvesicles that were also found free in the cytoplasm and aggregated within vacuolar structures. Reversed-phase high-performance liquid chromatography of RPE cells and their media detected melanogens, i.e. intermediates of melanin biosynthesis, including several indole derivatives. The porcine RPE cultures therefore may be a useful system for studying melanogenic regulation.  相似文献   
110.
Neurons in the monkey cerebral cortex containing nicotinamideadenine dinucleotide phosphate-diaphorase (NADPH-d) can he dividedinto two distinct types, both nonpyramidal. Type I neurons havea large soma (diameter 20–50 µm), a dense NADPH-dhistochemical reaction. and are distributed throughout the cortex,but mainly in the subcortical white matter, and are mostly aspiny.Type II cells have a small soma (< 20 µm) with lightNADPH-d reactivity and are distributed primarily in the supragranularlayers, particularly layers II and upper III. The numericaldensity of type II cells is much greater than that of type I.Type I neurons also stain for GABA and a few intracortical typeI cells contain calbindin. All type II cells found here arecolocalized with both GABA and calbindin. Neither type I nortype II cells are stained for parvalbumin. Together with previous observations that almost all corticalNADPH-d cells in various subprimates are like type I cells,we suggest that type II cells may form a group of NADPH-d-richneurons differentiated in higher mammalian cortex from a subpopulationof calbindin-containing GABAergic interneurons, and these nitricoxide-synthesizing cells may play a role in control of intracorticalneuronal activity characteristic of higher cerebral functionsin advanced mammals.  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