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   244139篇
  免费   19922篇
  国内免费   9103篇
耳鼻咽喉   2895篇
儿科学   3724篇
妇产科学   2917篇
基础医学   31618篇
口腔科学   5297篇
临床医学   26529篇
内科学   38223篇
皮肤病学   5136篇
神经病学   15894篇
特种医学   12161篇
外国民族医学   45篇
外科学   28484篇
综合类   24839篇
现状与发展   29篇
一般理论   33篇
预防医学   15924篇
眼科学   6231篇
药学   24318篇
  104篇
中国医学   9826篇
肿瘤学   18937篇
  2024年   428篇
  2023年   2272篇
  2022年   5967篇
  2021年   10198篇
  2020年   6742篇
  2019年   6668篇
  2018年   7565篇
  2017年   6891篇
  2016年   7484篇
  2015年   10748篇
  2014年   13134篇
  2013年   14432篇
  2012年   21057篇
  2011年   21135篇
  2010年   14010篇
  2009年   11747篇
  2008年   14905篇
  2007年   14413篇
  2006年   13254篇
  2005年   12006篇
  2004年   9853篇
  2003年   9046篇
  2002年   7575篇
  2001年   5961篇
  2000年   5002篇
  1999年   3994篇
  1998年   1946篇
  1997年   1751篇
  1996年   1256篇
  1995年   1195篇
  1994年   989篇
  1993年   698篇
  1992年   1155篇
  1991年   1023篇
  1990年   919篇
  1989年   811篇
  1988年   661篇
  1987年   647篇
  1986年   503篇
  1985年   457篇
  1984年   318篇
  1983年   233篇
  1982年   164篇
  1981年   189篇
  1980年   146篇
  1979年   239篇
  1978年   168篇
  1976年   140篇
  1974年   149篇
  1973年   132篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Social Psychiatry and Psychiatric Epidemiology - The negative effect of catastrophic financial loss on suicide risk is widely perceived but hardly studied in-depth because of various difficulties...  相似文献   
2.
3.
Amacrine cells of the retina are conspicuously variable in their morphologies, their population demographics, and their ensuing functions. Vesicular glutamate transporter 3 (VGluT3) amacrine cells are a recently characterized type of amacrine cell exhibiting local dendritic autonomy. The present analysis has examined three features of this VGluT3 population, including their density, local distribution, and dendritic spread, to discern the extent to which these are interrelated, using male and female mice. We first demonstrate that Bax-mediated cell death transforms the mosaic of VGluT3 cells from a random distribution into a regular mosaic. We subsequently examine the relationship between cell density and mosaic regularity across recombinant inbred strains of mice, finding that, although both traits vary across the strains, they exhibit minimal covariation. Other genetic determinants must therefore contribute independently to final cell number and to mosaic order. Using a conditional KO approach, we further demonstrate that Bax acts via the bipolar cell population, rather than cell-intrinsically, to control VGluT3 cell number. Finally, we consider the relationship between the dendritic arbors of single VGluT3 cells and the distribution of their homotypic neighbors. Dendritic field area was found to be independent of Voronoi domain area, while dendritic coverage of single cells was not conserved, simply increasing with the size of the dendritic field. Bax-KO retinas exhibited a threefold increase in dendritic coverage. Each cell, however, contributed less dendrites at each depth within the plexus, intermingling their processes with those of neighboring cells to approximate a constant volumetric density, yielding a uniformity in process coverage across the population.SIGNIFICANCE STATEMENT Different types of retinal neuron spread their processes across the surface of the retina to achieve a degree of dendritic coverage that is characteristic of each type. Many of these types achieve a constant coverage by varying their dendritic field area inversely with the local density of like-type neighbors. Here we report a population of retinal amacrine cells that do not develop dendritic arbors in relation to the spatial positioning of such homotypic neighbors; rather, this cell type modulates the extent of its dendritic branching when faced with a variable number of overlapping dendritic fields to approximate a uniformity in dendritic density across the retina.  相似文献   
4.
5.
目的 借助网络药理学的方法,探究两组王琦教授新冠肺炎预防方(简称预防方)预防新型冠状病毒肺炎(COVID-19)的分子靶点和机制。方法 通过TCMSP数据库检索并筛选其活性成分及其作用靶点,通过Uniprot数据库进行蛋白标准化处理。从Genecards数据库中以“Novel coronavirus pneumonia”为关键词搜索获取COVID-19的靶标,构建相交靶点韦恩图。通过cytoscape3.7.2构建PPI蛋白互作网络,寻找富集数目最多的靶点。通过R语言对预防方治疗COVID-19的靶点进行GO和KEGG富集分析,并绘制气泡图。结果 预防方与新冠肺炎相关靶点涉IL-6、TNF、CXCL8、VEGFA、MMP9;GO功能富集分析分别获得53、57条通路;27、29条KEGG相关信号通路。结论 王琦教授新冠肺炎预防方中的主要活性成分为槲皮素、山奈酚、木犀草素、β-谷甾醇、植物甾醇等,可能通过作用于IL-6、TNF、CXCL8、VEGFA、MMP9、CXCL8、IL10、CCL2、IL1B等靶点和介导TNF信号通路、T细胞受体信号通路、Toll样受体信号通路等发挥作用,从而促进免疫反应、炎症反应及细菌防御反应,预防COVID-19。  相似文献   
6.
7.
Comprehensive evidence regarding the treatment of non-anaemic iron deficiency in patients undergoing valvular heart surgery is lacking. This study aimed to investigate the association between non-anaemic iron deficiency and postoperative outcomes in these patients. We retrospectively analysed 321 patients of which 180 (56%) had iron deficiency (defined as serum ferritin < 100 ng.ml-1 or < 300 ng.ml-1 with transferrin saturation < 20%). While the iron-deficient group had lower pre-operative haemoglobin levels than the non-iron deficient group (median (IQR [range]) 134 (127–141 [120–172]) g.l-1, 143 (133–150 [120–179]) g.l-1, p = 0.001), there was no between-group difference in allogeneic red blood cell transfusion. Median (IQR [range]) days alive and out of hospital at postoperative day 90 was 1 day shorter in the iron-deficient group (80 (77–82 [9–85]) days vs. 81 (79–83 [0–85]) days, p = 0.026). In multivariable analysis, only cardiopulmonary bypass duration (p = 0.032) and intra-operative allogeneic red blood cell transfusion (p = 0.011) were significantly associated with reduced days alive and out of hospital at postoperative day 90. Iron deficiency did not exert any adverse influence on secondary outcomes except length of hospital stay. Our findings indicate that non-anaemic iron deficiency alone is not associated with adverse effects in patients undergoing valvular heart surgery when it does not translate into an increased risk of allogeneic transfusion.  相似文献   
8.
Post-induction hypotension is common and associated with postoperative complications. We hypothesised that pneumatic leg compression reduces post-induction hypotension in elderly patients undergoing robot-assisted laparoscopic prostatectomy. In this double-blind randomised study, patients were allocated randomly to the pneumatic leg compression group (n = 50) or control (n = 50). In the intervention group, pneumatic leg compression was initiated before induction of anaesthesia. In the control group, pneumatic leg compression was initiated 20 min after anaesthesia induction. The primary outcome was the incidence of post-induction hypotension in these groups. Post-induction hypotension was defined as systolic blood pressure < 90 mmHg during the first 20 min after induction. Haemodynamic variables and area under the curve of post-induction systolic blood pressure over time were assessed. Complications associated with pneumatic leg compression were recorded, including: peripheral neuropathy; compartment syndrome; extensive bullae beneath the leg sleeves; and pulmonary thromboembolism. The incidence of post-induction hypotension decreased in the pneumatic leg compression group compared with that in the control group; 5 (10%) vs. 29 (58%), respectively, p < 0.001. In the pneumatic leg compression group, the lowest systolic, diastolic and mean blood pressures 20 min after induction of anaesthesia were significantly greater than the control group. Pneumatic leg compression resulted in an increased area under the curve of systolic blood pressure in the first 20 min after induction, p = 0.001. There were no pneumatic leg compression-related complications. Pneumatic leg compression reduced post-induction hypotension in elderly patients undergoing robot-assisted laparoscopic prostatectomy, suggesting that it is an effective and safe intervention to prevent post-induction hypotension among elderly patients undergoing general anaesthesia.  相似文献   
9.
孙莉  赵毅 《现代肿瘤医学》2019,(13):2420-2424
三阴性乳腺癌(triple negative breast cancer,TNBC)是雌激素受体(estrogen receptor,ER)、孕激素受体(progesterone receptor,PR)及人类表皮生长因子受体(human epidermal growth factor-2,HER-2)均不表达的乳腺癌。按其功能特征可归纳为5类分子分型:以DNA修复缺陷或生长因子为途径的基底细胞样三阴性乳腺癌;以上皮-间充质转化和肿瘤干细胞为特征的间质样三阴性乳腺癌;免疫调节型三阴性乳腺癌;雄激素受体过表达的管腔/分泌型三阴性乳腺癌;HER-2富集型三阴性乳腺癌。三阴性乳腺癌恶性程度高且异型性较大,其治疗困难且预后较差,内分泌治疗及靶向治疗不敏感。目前很多学者对于三阴性乳腺癌的治疗各有研究,并有临床试验证实下述治疗有效。  相似文献   
10.
Metformin, a drug for type 2 diabetes mellitus, has shown therapeutic effects for various cancers. However, it had no beneficial effects on the survival rate of human malignant mesothelioma (HMM) patients. The present study was performed to elucidate the underlying mechanism of metformin resistance in HMM cells. Glucose‐starved HMM cells had enhanced resistance to metformin, demonstrated by decreased apoptosis and autophagy and increased cell survival. These cells showed abnormalities in mitochondria, such as decreased ATP synthesis, morphological elongation, altered mitochondrial permeability transition pore and hyperpolarization of mitochondrial membrane potential (MMP). Intriguingly, Mdr1 was significantly upregulated in mitochondria but not in cell membrane. The upregulated mitochondrial Mdr1 was reversed by treatment with carbonyl cyanide m‐chlorophenyl hydrazone, an MMP depolarization inducer. Furthermore, apoptosis and autophagy were increased in multidrug resistance protein 1 knockout HMM cells cultured under glucose starvation with metformin treatment. The data suggest that mitochondrial Mdr1 plays a critical role in the chemoresistance to metformin in HMM cells, which could be a potential target for improving its therapeutic efficacy.  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