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   9677篇
  免费   804篇
  国内免费   181篇
耳鼻咽喉   100篇
儿科学   183篇
妇产科学   394篇
基础医学   1229篇
口腔科学   205篇
临床医学   999篇
内科学   1965篇
皮肤病学   175篇
神经病学   634篇
特种医学   361篇
外科学   1402篇
综合类   396篇
现状与发展   1篇
一般理论   2篇
预防医学   453篇
眼科学   189篇
药学   980篇
  4篇
中国医学   194篇
肿瘤学   796篇
  2023年   92篇
  2022年   145篇
  2021年   285篇
  2020年   184篇
  2019年   285篇
  2018年   322篇
  2017年   219篇
  2016年   205篇
  2015年   313篇
  2014年   382篇
  2013年   510篇
  2012年   681篇
  2011年   782篇
  2010年   496篇
  2009年   395篇
  2008年   560篇
  2007年   553篇
  2006年   531篇
  2005年   496篇
  2004年   446篇
  2003年   365篇
  2002年   322篇
  2001年   260篇
  2000年   221篇
  1999年   185篇
  1998年   88篇
  1997年   75篇
  1996年   64篇
  1995年   79篇
  1994年   58篇
  1993年   67篇
  1992年   124篇
  1991年   99篇
  1990年   86篇
  1989年   66篇
  1988年   57篇
  1987年   75篇
  1986年   39篇
  1985年   51篇
  1984年   47篇
  1983年   33篇
  1982年   33篇
  1981年   27篇
  1980年   23篇
  1979年   25篇
  1978年   19篇
  1977年   20篇
  1976年   22篇
  1975年   24篇
  1972年   17篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
目的:研究复方中药艾迪注射液对白血病耐药细胞株K562/ADM细胞体外生长和增殖周期的影响。方法:采用细胞体外培养技术,台盼兰染色计数法观察活细胞数量变化并绘制细胞生长曲线,细胞集落形成实验,MTT法检测生长抑制率,光学显微镜、透射电镜观察细胞形态变化.流式细胞仪测定细胞增殖周期。结果:艾迪注射液对KS62/ADM细胞生长和增殖活力均有明显的抑制作用,作用随艾迪注射液剂量和作用时间的增加而增加,呈量效、时效关系,与对照组比较,P〈0.05。流式细胞分析显示它能抑制细胞周期,减少G1期的比例,增加S期和G2期的比例,并能明显诱导细胞凋亡,尤以中、高剂量组和联合用药组为明显,在光镜、透射电镜下观察到较为典型的细胞凋亡形态。结论:艾迪注射液有明显的抗肿瘤活性,能抑制K562/ADM细胞的生长和增殖,调控细胞增殖周期并诱导凋亡。  相似文献   
153.
目的:观察二乙酰基莲心碱拮抗氯化钾、乙酰胆碱(Ach)和组胺(His)所致猪冠状动脉条收缩的作用.方法:离体平滑肌实验方法,观察二乙酰基莲心碱对氯化钾,Ach,His所致猪冠状动脉条收缩曲线的影响以及在无钙克氏液中,对His引起猪冠状动脉条第一相收缩和钙引起第二相收缩的影响.结果:不同剂量二乙酰基莲心碱可使氯化钾,Ach,His所致冠脉条收缩量效曲线呈非竞争性拮抗作用,对冠脉条第一相和第二相收缩都有明显的抑制作用结论:二乙酰基莲心碱具有扩张冠脉的作用,此作用与拮抗细胞内钙的释放和抑制外钙内流有关.  相似文献   
154.
155.
156.
157.
The aim of this study was to evaluate the change of breast density in the normal breast of patients receiving neoadjuvant chemotherapy (NAC). Forty‐four breast cancer patients were studied. MRI acquisition was performed before treatment (baseline), and 4 and 12 weeks after treatment. A computer‐algorithm‐based program was used to segment breast tissue and calculate breast volume (BV), fibroglandular tissue volume (FV), and percent density (PD) (the ratio of FV over BV × 100%). The reduction of FV and PD after treatment was compared with baseline using paired t‐tests with a Bonferroni–Holm correction. The association of density reduction with age was analyzed. FV and PD after NAC showed significant decreases compared with the baseline. FV was 110.0 ml (67.2, 189.8) (geometric mean (interquartile range)) at baseline, 104.3 ml (66.6, 164.4) after 4 weeks (p < 0.0001), and 94.7 ml (60.2, 144.4) after 12 weeks (comparison with baseline, p < 0.0001; comparison with 4 weeks, p = 0.016). PD was 11.2% (6.4, 22.4) at baseline, 10.6% (6.6, 20.3) after 4 weeks (p < 0.0001), and 9.7% (6.2, 17.9) after 12 weeks (comparison with baseline, p = 0.0001; comparison with 4 weeks, p = 0.018). Younger patients tended to show a higher density reduction, but overall correlation with age was only moderate (r = 0.28 for FV, p = 0.07, and r = 0.52 for PD, p = 0.0003). Our study showed that breast density measured from MR images acquired at 3T MR can be accurately quantified using a robust computer‐aided algorithm based on non‐parametric non‐uniformity normalization (N3) and an adaptive fuzzy C‐means algorithm. Similar to doxorubicin and cyclophosphamide regimens, the taxane‐based NAC regimen also caused density atrophy in the normal breast and showed reduction in FV and PD. The effect of breast density reduction was age related and duration related. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
158.
Healthy food distribution programs that allow small retailers to purchase fresh fruits and vegetables at wholesale prices may increase the profitability of selling produce. While promising, little is known about how these programs affect the availability of fresh fruits and vegetables in underserved communities. This study examined the impacts of a healthy food distribution program in Los Angeles County over its first year of operation (August 2015–2016). Assessment methods included: (1) a brief survey examining the characteristics, purchasing habits, and attitudes of stores entering the program; (2) longitudinal tracking of sales data examining changes in the volume and variety of fruits and vegetables distributed through the program; and (3) the collection of comparison price data from wholesale market databases and local grocery stores. Seventeen stores participated in the program over the study period. One-fourth of survey respondents reported no recent experience selling produce. Analysis of sales data showed that, on average, the total volume of produce distributed through the program increased by six pounds per week over the study period (95% confidence limit: 4.50, 7.50); trends varied by store and produce type. Produce prices offered through the program approximated those at wholesale markets, and were lower than prices at full-service grocers. Results suggest that healthy food distribution programs may reduce certain supply-side barriers to offering fresh produce in small retail venues. While promising, more work is needed to understand the impacts of such programs on in-store environments and consumer behaviors.  相似文献   
159.
Tsai J‐H, Huang W‐C, Kuo K‐T, Yuan R‐H, Chen Y‐L & Jeng Y‐M
(2012) Histopathology
S100P immunostaining identifies a subset of peripheral‐type intrahepatic cholangiocarcinomas with morphological and molecular features similar to those of perihilar and extrahepatic cholangiocarcinomas Aims: S100P is a calcium‐binding protein that is frequently expressed in pancreatic adenocarcinoma and perihilar cholangiocarcinoma. The aim of this study was to investigate the pathological significance of the expression of S100P in peripheral intrahepatic cholangiocarcinoma (ICC). Methods and results: Immunohistochemical staining was used to investigate S100P expression in 112 cases of peripheral ICC. The results were compared with those for perihilar and extrahepatic cholangiocarcinomas. Patients with S100P‐positive peripheral ICC were more likely to have elevated serum levels of carcinoembryonic antigen (CEA) and CA19‐9 than those with S100P‐negative peripheral ICCs. All cases of peripheral ICC associated with intrahepatic lithiasis and all cases with intraductal/periductal growth patterns were positive for S100P. S100P‐positive peripheral ICCs were highly associated with ‘bile duct’ morphology rather than cholangiolar differentiation. Nearly all cases of perihilar and extrahepatic cholangiocarcinoma were positive for S100P. Similarly to perihilar and extrahepatic cholangiocarcinomas, S100P‐positive peripheral ICCs showed more frequent expression of CEA and MUC2, and were more likely to be N‐cadherin‐negative, than S100P‐negative cases. Notably, K‐RAS mutations were only detected in S100P‐positive peripheral ICCs, with a frequency similar to that in perihilar and extrahepatic cholangiocarcinomas. Patients with S100P‐positive peripheral ICC were more likely to have poor prognoses than those with S100P‐negative tumours. Conclusions: S100P immunostaining identifies a subset of peripheral ICC that probably originates from larger bile ducts. This subset of peripheral ICCs shares common morphological and molecular features with perihilar and extrahepatic cholangiocarcinomas.  相似文献   
160.
Aging is the most important risk factor in cardiovascular disease (CVD), which is the leading causes of death worldwide and the second major cause of death in Taiwan. The major factor in heart failure during aging is heart remodeling, including long-term stress-induced cardiac hypertrophy and fibrosis. Exercise is good for aging heart health, but the impact of exercise training on aging is not defined. This study used 3-, 12- and 18-month-old rats and randomly divided each age group into no exercise training control groups (C3, A12 and A18) and moderate gentle swimming exercise training groups (E3, AE12 and AE18). The protocol of exercise training was swimming five times weekly with gradual increases from the first week from 20 to 60 min for 12 weeks. Analyses of protein from rat heart tissues and sections revealed cardiac inflammation, hypertrophy and fibrosis pathway increases in aged rat groups (A12 and A18), which were improved in exercise training groups (AE12 and AE18). There were no heart injuries in young rat hearts in exercise group E3. These data suggest that moderate swimming exercise training attenuated aging-induced cardiac inflammation, hypertrophy and fibrosis injuries of rat hearts.  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