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   218789篇
  免费   18760篇
  国内免费   4873篇
耳鼻咽喉   3466篇
儿科学   4204篇
妇产科学   3587篇
基础医学   18697篇
口腔科学   7319篇
临床医学   19948篇
内科学   20701篇
皮肤病学   2465篇
神经病学   12292篇
特种医学   6629篇
外国民族医学   11篇
外科学   20535篇
综合类   34037篇
现状与发展   9篇
一般理论   24篇
预防医学   29002篇
眼科学   2206篇
药学   20667篇
  338篇
中国医学   27111篇
肿瘤学   9174篇
  2024年   1007篇
  2023年   4369篇
  2022年   8226篇
  2021年   10774篇
  2020年   10433篇
  2019年   11655篇
  2018年   10342篇
  2017年   8949篇
  2016年   8012篇
  2015年   7493篇
  2014年   14589篇
  2013年   15111篇
  2012年   13081篇
  2011年   14094篇
  2010年   11325篇
  2009年   9830篇
  2008年   9189篇
  2007年   9193篇
  2006年   7870篇
  2005年   6672篇
  2004年   5548篇
  2003年   4929篇
  2002年   3844篇
  2001年   3190篇
  2000年   2827篇
  1999年   2322篇
  1998年   1870篇
  1997年   1693篇
  1996年   1377篇
  1995年   1345篇
  1994年   1221篇
  1993年   1100篇
  1992年   969篇
  1991年   908篇
  1990年   759篇
  1989年   755篇
  1988年   686篇
  1987年   614篇
  1986年   552篇
  1985年   1819篇
  1984年   2082篇
  1983年   1313篇
  1982年   1728篇
  1981年   1196篇
  1980年   1030篇
  1979年   913篇
  1978年   744篇
  1977年   564篇
  1976年   702篇
  1975年   479篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
971.
为了研究β-1,4-半乳糖基转移酶 和 (β-1,4-Gal T- and )蛋白表达的亚细胞结构定位 ,本实验构建了β-1,4-Gal T- 和 融合绿色荧光蛋白 (GFP)表达质粒 ,分别将构建的质粒转染到 PC12细胞和肝癌 772 1细胞中 ,在荧光显微镜下观察β-1,4-Gal T- 和 在其中表达的亚细胞结构定位。发现 ,β-1,4-Gal T- 和 主要表达在这两种细胞的细胞核旁的 Golgi复合体 ,说明它们主要分布在 Golgi复合体上。提示它们可能是在 Golgi复合体参与蛋白质的糖链修饰  相似文献   
972.
This paper describes the development of a digitized, real-time, microcomputer-based signal processing system which records the following variables: systolic and diastolic blood pressure, heart rate, pulse transit time, blood volume pulse, and R-, S-, and T-wave amplitudes of EKG signals. Forty-eight healthy subjects participated in a three-task stress response study in order to gather initial data for evaluating the reliability and validity of this monitoring system. The three tasks represented replications of earlier studies: 1) reading aloud of a monotonous neutral text (Reading Only, RO); 2) mental arithmetic without vocalization (Arithmetic Quiet, AQ); and 3) mental arithmetic with vocalization (Arithmetic Aloud, AA). The findings provided support for the reliability and validity of the new monitoring system given that few data were lost, and resting values as well as differential task responses were found to be comparable with earlier data sets derived via similar experimental protocols.  相似文献   
973.
The diagnosis of light chain deposition nephropathy is based on the immunohistochemical demonstration of monoclonal light chain deposits within connective tissue matrix and on the presence at the ultrastructural level of electron-dense granular deposits along glomerular and tubular basement membranes. A nodular glomerulopathy characterized by amorphous periodic acid-Schiff-positive and argyrophilic widened mesangium and nodules is described in three patients with light chain deposition nephropathy. Light microscopic examination did not allow discrimination between the glomerular changes found in these specimens and the nodular glomerulosclerosis described in four patients with well-documented diabetes mellitus. Electron microscopic examination revealed microtubular fibrils 10 to 12 nm thick in mesangial areas in both groups. Such microfibrils could be glycoproteins. Immunofluorescence localization of matrix proteins, by staining with affinity-purified antibodies to types I, III, IV, and V (A, B) collagens, fibronectin, laminin, and heparan sulfate-containing proteoglycans, showed similar distributions in the two conditions. The mechanism of this abnormal accumulation of mesangial and glomerular basement membrane matrix proteins in two different conditions remains unknown.  相似文献   
974.
Organ spectrophotometry has been applied to analyze cytochrome redox changes in brain slice preparations. An interface-chamber method for maintaining metabolism of brain slice tissues was devised to reduce noise on recording traces of spectrophotometric signals, and then used for continuous monitoring and simultaneous recording of electrical and optical signals from brain slices. With this method, the noise level during the recording of redox states of cytochromes was decreased to 0.0004 A unit.  相似文献   
975.
To identify Fc epsilon receptors on human cell lines and peripheral blood lymphocytes, we developed a new method which relies on the binding of constructed immune complexes to Fc epsilon receptor-positive cells. Cell suspensions from either cell lines or peripheral blood lymphocytes were incubated with complexes of human myeloma IgE and murine monoclonal anti-human IgE at various ratios prior to cytocentrifugation. The complexes bound to the cells were subsequently visualized by immunoperoxidase staining. The specificity of this assay to detect cell surface Fc epsilon receptors was shown by the ability of human myeloma IgE to block the binding of the IgE complexes, resulting in unstained cells, whereas IgM, IgG, and IgA were unable to block the binding of the complexes (stained cells). This method is reproducible, allows quantification of a single sample at different times, and provides a record of the results. It can also be adapted to identify any cell surface receptor for which the ligand is known.  相似文献   
976.
977.
Summary Detailed examination is made of the responses of visual cortical cells (area 17, border 17–18 and adjacent area 18) in the anaesthetized cat to stationary flashing bars and to bars (lines) and edges moving at their optimal velocities. Particular attention is given to the receptive field organization of cells in the simple family. While there is good general agreement between the main receptive field subregions revealed by stationary and moving stimuli, the responses to moving light and dark bars, supplemented by the responses to moving light and dark edges, provide a much more rapid, accurate and complete guide to the spatial organization of the receptive fields than do the response profiles to a stationary flashing bar. Moving light and dark bars between them generally reveal more subregions in the receptive fields of simple cells than is evident from the response profiles to a stationary flashing bar, particularly when the receptive fields have many subregions. In addition the responses to moving edges provide a rapid guide to spatial summation across the width of a subregion and the possible antagonistic effects of the next subregion in sequence.Two subclasses of cells in the simple family have been recognized: ordinary simple and fast simple cells. Two cell classes (A-cells and silent periodic cells) having properties intermediate between simple and complex types are discriminated and their properties described.  相似文献   
978.
Male albino Wistar rats were injected bilaterally with 4 micrograms of 6-hydroxydopamine into the dorsal noradrenergic bundle to deplete forebrain noradrenaline to less than 5% of control values. Acquisition learning of a fixed interval schedule or a continuously reinforced schedule was not altered but resistance to extinction was seen after food reinforced training on either schedule but not after water reinforced training. A possible increase in food motivation was tested by the use of preloading with free food prior to a fixed interval session but both control and lesioned rats reacted similarly to this manipulation thus appearing to exclude an increase in food motivation. An attentional explanation is proposed and tested by the demonstration that resistance to extinction does not occur after a partially (variable ratio 4), as opposed to a continuously, reinforced schedule. Further evidence in favour of an attentional mechanism comes from the finding that on both a fixed interval and a continuously reinforced schedule the lesion has to be present during the acquisition phase to result in subsequent resistance to extinction. Intact animals trained on either schedule and subsequently subjected to the lesion failed to show an increased resistance to extinction.  相似文献   
979.
Mixed epithelial and stromal tumor of the kidney is a rare biphasic tumor composed of cysts and tubules embedded in the spindle cell stroma. Although the histogenesis of this tumor is unknown, it has been proposed that both components of the tumor, i.e., stromal and epithelial, are neoplastic. The authors report preliminary immunohistochemical and electron microscopic studies of the epithelial component from one case of a typical, benign, mixed epithelial, and stromal tumor of the kidney. In this study, some tubules showed positivity for proximal, while others showed positivity for distal, nephron immunomarkers. By electron microscopy, some tubules had features of proximal tubular epithelium, while other tubules had features of the loop of Henle (thin segments). The authors believe that in a benign tumor such morphologic heterogeneity is inconsistent with neoplastic proliferation. Therefore, they postulate that in mixed epithelial and stromal tumor of the kidney the tubules are entrapped rather than neoplastic. Additional studies are needed to address this issue and electron microscopy should play a significant role in this process.  相似文献   
980.
睡眠信念与态度量表在失眠患者健康教育中的应用   总被引:3,自引:0,他引:3  
目的: 采用睡眠个人信念与态度量表探索患者睡眠障碍与哪些歪曲的信念有关,针对歪曲的信念进行睡眠实践教育,达到促进睡眠的目的.方法: 连续收集62例以失眠为主诉的患者,随机分成试验组与对照组,各31例,两组均在药物治疗及心理治疗基础上进行睡眠健康教育.试验组针对患者自身存在的歪曲信念态度进行健康教育,而对照组只进行常规的健康宣教.入组前及入组后每周,应用睡眠个人信念与态度量表(Dysfunctional Beliefs and Attitudes about Sleep Scale,DBAS)、匹茨堡睡眠指数量表(Pittsburgh Sleep Quality Index,PSQI)对两组进行测评,同时让患者评价睡眠时间、睡眠质量、睡眠效果和对健康教育接受程度.结果: 健康教育4周后试验组和对照组DBAS得分均高于人组时[(111.0±8.7)vs.(88.9±12.3)、(93.5±17.2)vs.(81.3±19.2),P:0.001、0.010],而PSQI得分均低于入组时[(5.5±2.1)vs.(10.9±4.4)、(9.0 ±2.1)vs.(11.5±3.6),均P=0.001];健康教育4周后对照组的DBAS得分低于实验组,而PSQI得分高于实验组.健康教育后试验组对睡眠时间、睡眠质量、睡眠效果满意的比例均明显提高,睡眠时间满意的比例由18/31到30/31,对睡眠质量满意比例由8/31变为23/31,对睡眠效果满意比例由8/31到21/31(均P<0.05).试验组对睡眠时间满意的比例明显高于对照组(30/31 vs.14/31,P<0.01),对健康教育的接受程度也明显高于对照组(18/31 vs.5/31,P<0.05).结论: 试验组健康教育后患者的睡眠信念有了明显的改善,睡眠质量有了提高.  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