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   102659篇
  免费   9880篇
  国内免费   3199篇
耳鼻咽喉   823篇
儿科学   1167篇
妇产科学   975篇
基础医学   12000篇
口腔科学   3656篇
临床医学   10645篇
内科学   10731篇
皮肤病学   1290篇
神经病学   6555篇
特种医学   3164篇
外国民族医学   11篇
外科学   7060篇
综合类   15028篇
现状与发展   8篇
一般理论   3篇
预防医学   17084篇
眼科学   1207篇
药学   13814篇
  128篇
中国医学   5822篇
肿瘤学   4567篇
  2024年   448篇
  2023年   1943篇
  2022年   4050篇
  2021年   5062篇
  2020年   4818篇
  2019年   4215篇
  2018年   3783篇
  2017年   4054篇
  2016年   4106篇
  2015年   4026篇
  2014年   7051篇
  2013年   7567篇
  2012年   6788篇
  2011年   7116篇
  2010年   5331篇
  2009年   4966篇
  2008年   4731篇
  2007年   4706篇
  2006年   4011篇
  2005年   3519篇
  2004年   2911篇
  2003年   2670篇
  2002年   2086篇
  2001年   1972篇
  2000年   1547篇
  1999年   1349篇
  1998年   1292篇
  1997年   1167篇
  1996年   1008篇
  1995年   912篇
  1994年   879篇
  1993年   678篇
  1992年   643篇
  1991年   543篇
  1990年   467篇
  1989年   479篇
  1988年   413篇
  1987年   363篇
  1986年   284篇
  1985年   374篇
  1984年   289篇
  1983年   174篇
  1982年   199篇
  1981年   154篇
  1980年   153篇
  1979年   114篇
  1978年   76篇
  1977年   51篇
  1976年   72篇
  1974年   41篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
21.
We have developed a guar wholemeal bread and tested its physiological efficacy and sensory qualities. The objective of the study was to estimate the optimum concentration of guar in bread required to reduce postprandial glycaemia and insulinaemia without adversely affecting the quality of the bread. Following overnight fasts, 15 normal weight, non-diabetic subjects consumed meals of wholemeal bread alone (controls) and supplemented with guar at three different concentrations (5, 10 and 15% replacement of wheat flour). Blood samples for glucose and insulin analysis were taken preprandially, and at 30 and 60 min after the start of each meal. The acceptability of the wholemeal control and guar breads was assessed using a hedonic scaling method. A significantly lower blood glucose rise at 30 min was found after the 15% guar bread meal compared to the control. Plasma insulin responses at 30 and 60 min were significantly lower after the 10 and 15% guar bread meals compared to the controls. Hedonic scores indicated that the subjects found the 5 and 10% guar breads acceptable and in the case of the 5% variety the mean score was identical to the control. We suggest that a guar concentration of between 5 and 10% replacement of wheat flour (wholemeal or white) should be used for the baking of guar wholemeal bread but further work is needed to define the precise quantity of guar required.  相似文献   
22.
A sample enriched for familial combined hyperlipidemia (FCHL) was examined for evidence of an association between genotype at an apolipoprotein B (apoB) elevating locus defined by complex segregation analysis and FCHL. Complex segregation analysis detected a locus with a large effect on plasma apoB levels and was used to compute the most probable genotype of family members. None of the 35 normolipidemic adults carried a copy of the allele associated with elevated apoB levels, yet 58% of the 109 adults with FCHL carried 1 (29%) or 2 (28%) copies. Two of 28 (7%) normal children had 1 copy of this allele and none had 2 copies, while 88 of 182 (48%) children with FCHL had 1 (26%) or 2 (22%) copies. Further, 4l of 48 (85%) individuals classified as having hyperapobetalipoproteinemia did not carry a copy of this “elevated apoB” allele. Therefore, the presence of the allele associated with elevation of apoB level is highly predictive of FCHL and this association cannot be explained solely by the presence of elevated apoB levels in FCHL, suggesting that the locus controlling apoB levels may play an etiologic role in FCHL. © 1993 Wiley-Liss, Inc.  相似文献   
23.
24.
When the distance between linked loci is expressed in terms of the correlation between the identity-by-descent (idb) values of the loci, then a path model may be used to order loci with data on sib-pairs and their parents. The relationship between the recombination fraction and the correlation coefficient is developed and a method for fitting a covariance matrix predicted by a specific ordering of loci to an observed covariance matrix is proposed. © 1993 Wiley-Liss. Inc.  相似文献   
25.
Perimetry suffers from considerable variability of results. A new technique for estimating individual criterion levels in normal subjects exposes the important role of psychological variables. The analysis depends on features peculiar to acuity perimetry. It can be accommodated in the regular examination. The results can be used to compensate for practice effects in serial examinations and to tighten the range of normal limits. The reduction in variation between normal subjects amounted to 57 per cent.  相似文献   
26.
The pronounced susceptibility effect of macrovessels in MR bolus-tracking studies induces spots of artificially high blood flow and volume in perfusion parameter images. These high-intensity regions impede the detection of perfusion changes and lead to elevated perfusion parameters in adjacent tissues. The purpose of this work was to explore postprocessing methods to reduce the influence of macrovessel signal in dynamic MRI. After data reduction was performed with the use of a principal component analysis (PCA), an independent component analysis (ICA) was applied to separate signal components of different compartments. Based on this decomposition, the dynamic time series were reconstructed with minimized contributions of macrovessel signal and noise. The influence of the temporal resolution and signal-to-noise ratio (SNR) of the source data were investigated by means of a simulation study. A region-of-interest (ROI)-based analysis of corrected and uncorrected in vivo data demonstrated that the influence of arteries and veins was reduced at least by 50%, while gray matter (GM) and white matter (WM) tissues were nearly unaffected by the correction process. Hemodynamic parameter images of the cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) were calculated from corrected and uncorrected scans. The corrected parameter images showed a clearly reduced macrovessel signal and an improved perceptibility of microvascular perfusion changes compared to the uncorrected ones.  相似文献   
27.
马瑛  靳学婷 《中国新药杂志》2007,19(11):991-994
目的:运用药物经济学的方法对在我院应用的6种中药注射液进行成本-效果分析。方法:271例急性脑梗死患者依据药物治疗方案不同分为6组,即血塞通组、舒血宁组、苦碟子组、疏血通组、川芎嗪组、丹红组,分别观察疗效,并运用药物经济学的方法进行成本-效果分析。结果:疏血通组的成本为3 419.90元,总有效率最高(91.84%),6组间增量成本-效果最低。因此疏血通组是较为合理、经济的方案。  相似文献   
28.
左双腔支气管导管管端位置与吸气峰压变化的关系   总被引:13,自引:3,他引:10  
目的 观测无隆突钩双腔支气管导管(DLT)管端位置与吸气峰压(Ppeak)以及肺顺应性环形状改变的关系,探讨用Ppeak和顺应性环的变化评估DLT管端位置的可行性。方法 拟行右侧剖胸手术的成年患者32例,静脉诱导后插入左Mallinckrodt DLT,吸入氧化亚氮和地氟醚维持麻醉。按纤维支气管镜(FOB)确认DLT管端位置和通气方式将观测过程分为四个阶段:第一阶段(S1),管端位置正确的双肺通气;第二阶段(S2),管端位置正确的左侧单肺通气;第三阶段(S3),管端插入左下支气管(置管过深)的左侧单肺通气;第四阶段(S。),管端处在左支气管开口(置管偏浅)的左侧单肺通气。每阶段均机械通气15min。结果 回归方程预计插管深度与FOB检查符合者占71.9%。S2时Ppeak值比S1时增加50.8%,肺顺应性(Cdyn)值减少36.2%;S3时Ppeak值比S1时增加87.4%,Cdyn值减少56.8%。PV环曲线斜率向右明显移位,环体显著延长。结论 用无隆突钩DLT行肺隔离,在无FOB定位的条件时,联合应用听诊法、回归方程预计插管深度、动态监测气道峰压和P-V环的变化综合评估,可提高DLT管端的正确到位率。单肺通气的气道峰压超过双肺通气时的1.65倍,且气道峰压超过25cm H2O.应高度怀疑DLT管端发生过深移位。  相似文献   
29.
Dual-energy X-ray absorptiometry (DXA) and quantitative ultrasound (QUS) are the accepted modalities for the evaluation of fracture risk in the clinical setting. However, neither method provides a direct measurement of bone mechanics. In this study, we investigated a prototype device, known as a mechanical response tissue analyzer (MRTA), which provides direct mechanical measurements of mechanical properties of bone. A total of 56 healthy volunteers (20 men and 36 women) between the ages of 18 and 83 were recruited. The MRTA was used to measure the cross-sectional bending stiffness (EI) of the ulna bone. Axial speed of sound (SOS) at the ulna bone was determined by QUS; bone mineral content (BMC) and bone mineral density (BMD) were determined by DXA. Correlations, regression analysis, and analyses of variance (ANOVAs) were used to compare the three modalities. These analyses revealed that although there are strong linear relationships among the data collected by the various technologies, the bone properties reflected by MRTA are not fully explained by DXA and QUS. We conclude that the total information conveyed by MRTA measurements is unique. Further research is needed to delineate the different qualities of bone strength that are captured by MRTA, but not by DXA or QUS.  相似文献   
30.
一次和多次住院精神分裂症患者再住院分析   总被引:9,自引:0,他引:9  
目的 :比较 1次和≥ 2次住院精神分裂症患者出院后的再住院率 ,初步探讨影响再住院的相关因素。 方法 :1999年度出院的 833例住院精神分裂症患者纳入调查 ,使用自制的再住院及其相关因素调查表 ,于 2 0 0 3年 12月底前电话或入户调查出院后至少 4 8个月的情况。 结果 :6 6 4例完成调查 ,分为 1次住院组 (333例 )和多次住院组 (331例 )。用生存分析 (Kaplan Meier公式 )比较两组未再住院率 ,12个月末 (分别为 6 7 0 %和 6 1 6 % )、2 4个月末 (5 6 2 %和 4 8 9% )、36个月末 (4 6 0和 35 1% )和 4 8个月末 (4 1 1%和 2 8 7% )。Cox回归风险比例模型分析影响再住院的相关因素显示 ,与药物依从性、生活事件、自知力和家庭照顾相关 (P <0 0 5 ) ,药物依从性对再住院的贡献值 (1 719)最大。 结论 :1次住院精神分裂症患者出院后的再住院率较多次住院者低。药物依从性是影响再住院的主要因素  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