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   3340篇
  免费   286篇
  国内免费   236篇
耳鼻咽喉   16篇
儿科学   32篇
妇产科学   43篇
基础医学   414篇
口腔科学   84篇
临床医学   446篇
内科学   439篇
皮肤病学   18篇
神经病学   186篇
特种医学   125篇
外国民族医学   1篇
外科学   332篇
综合类   480篇
一般理论   1篇
预防医学   240篇
眼科学   96篇
药学   381篇
  3篇
中国医学   183篇
肿瘤学   342篇
  2024年   9篇
  2023年   31篇
  2022年   118篇
  2021年   159篇
  2020年   96篇
  2019年   110篇
  2018年   128篇
  2017年   105篇
  2016年   79篇
  2015年   136篇
  2014年   167篇
  2013年   175篇
  2012年   232篇
  2011年   267篇
  2010年   163篇
  2009年   162篇
  2008年   153篇
  2007年   173篇
  2006年   200篇
  2005年   211篇
  2004年   122篇
  2003年   149篇
  2002年   103篇
  2001年   98篇
  2000年   83篇
  1999年   86篇
  1998年   62篇
  1997年   52篇
  1996年   47篇
  1995年   40篇
  1994年   24篇
  1993年   13篇
  1992年   22篇
  1991年   7篇
  1990年   12篇
  1989年   13篇
  1988年   20篇
  1987年   10篇
  1986年   9篇
  1985年   2篇
  1984年   7篇
  1983年   3篇
  1982年   2篇
  1979年   1篇
  1963年   1篇
排序方式: 共有3862条查询结果,搜索用时 15 毫秒
91.
我们运用自拟“强心益君汤”,结合西药治疗慢性心力衰竭58例,并与单用西药治疗的58例对照,取得了显著疗效,现总结如下。  相似文献   
92.
护士长心理压力调查   总被引:4,自引:1,他引:4  
[目的]调查护士长焦虑、抑郁的程度和由此导致的心理压力及其原因,探讨应对策略。[方法]采用集中问卷方式对43名在职护士长的焦虑、抑郁症状及产生原因进行调查。[结果]护士长这一特殊群体普遍存在较严重的焦虑、抑郁症状,焦虑总分平均44.2分,远远高于常模上限;抑郁自评量表得分平均为0,51,属轻度抑郁水平。焦虑、抑郁的主要原因为经济报酬不合理、护理纠纷增加、后勤支持系统援助不足、社会地位低、个人发展空间小等。[结论]必须高度重视护士长群体的身心状况,采取积极有效措施,缓解他们的精神和心理压力。  相似文献   
93.
Recent advances in understanding CD4+ T‐cell differentiation suggest that previous models of a few distinct, stable effector phenotypes were too simplistic. Although several well‐characterized phenotypes are still recognized, some states display plasticity, and intermediate phenotypes exist. As a framework for reexamining these concepts, we use Waddington's landscape paradigm, augmented with explicit consideration of stochastic variations. Our animation program “LAVA” visualizes T‐cell differentiation as cells moving across a landscape of hills and valleys, leading to attractor basins representing stable or semistable differentiation states. The model illustrates several principles, including: (i) cell populations may behave more predictably than individual cells; (ii) analogous to reticulate evolution, differentiation may proceed through a network of interconnected states, rather than a single well‐defined pathway; (iii) relatively minor changes in the barriers between attractor basins can change the stability or plasticity of a population; (iv) intrapopulation variability of gene expression may be an important regulator of differentiation, rather than inconsequential noise; (v) the behavior of some populations may be defined mainly by the behavior of outlier cells. While not a quantitative representation of actual differentiation, our model is intended to provoke discussion of T‐cell differentiation pathways, particularly highlighting a probabilistic view of transitions between states.  相似文献   
94.
目的:评价用银汞合会、町乐丽菲露AP-X复合树脂及Beautifil氟化玻璃聚合体对恒磨牙邻面龋进行充填治疗的临床效果。方法:选择58-71岁门诊患者176例416颗恒磨牙邻面龋患牙,按龋损部位分为龈缘组和龈上组,每组随机分为3组,分别用银汞合金、可乐丽菲露AP-X及Beautifil氟化玻璃聚合体按各闩洞型制备要求备涧后进行充填。银汞合金组深龋用聚羧酸锌水门汀垫底后充填;可乐丽菲露AP-X组及Beautifil氟化玻璃聚合体组深龋用Ionosit-Baseliiler垫底后充填。随访18-24个月观察治疗效果。结果:患者复查回访率为86.93%。龈缘组中,银汞合金组成功率92.31%;可乐丽菲露AP-X组成功率92.65%;Beautifil氟化玻璃聚合体组成功率87.76%。经χ2检验,3组差异均兀显著性。龈上组中,银汞合金组成功率91.30%;町乐丽菲露AP—X组成功率97.44%;Beautifil氟化玻璃聚合体组成功率95.77%。经χ2检验,3组差异均无显著性。结论:银汞合金、可乐丽菲露AP-X及Beautifil氟化玻璃聚合体修复恒磨牙邻面龋的临床嫂果良好,3组之间无明显茺异。  相似文献   
95.
目的:构建含编码嵌合体SBR-CTΔA1基因的转基因盐藻防龋疫苗.方法:观察野生型盐藻对除草剂草丁膦的敏感性,确定合适的筛选浓度;采用超声法将含编码嵌合体SBR-CTΔA1基因的植物表达质粒pROSB转化盐藻细胞,PCR法和Southern杂交技术筛选转基因盐藻,RT-PCR检测外源基因转录情况.结果:①野生型盐藻对草丁膦具有敏感性,固体培养基中浓度为8 mg/L的草丁膦和液体培养基中浓度为6 mg/L的草丁膦可以抑制盐藻的生长,是合适的筛选浓度;②获得转基因藻株,提取基因组DNA进行PCR分析,得到1.9 kb片段;进行Southern杂交分析,获得阳性信号条带;提取总RNA进行RT-PCR分析,部分藻株获得1.9 kb条带.结论:获得整合有目的基因且可以正常转录的转基因盐藻藻株,为研制安全、经济、高效的防龋疫苗提供工作基础.  相似文献   
96.
OBJECTIVE: To examine the association between abnormal exercise electrocardiographic (E-ECG) test results and mortality (all-cause and that resulting from coronary heart disease [CHD] or cardiovascular disease [CVD]) in a large population of asymptomatic men with metabolic syndrome (MetS).PATIENTS AND METHODS: A total of 9191 men (mean age, 46.9 years) met the criteria of having MetS. All completed a maximal E-ECG treadmill test (May 14, 1979, through April 9, 2001) and were without a previous CVD event or diabetes at baseline. Main outcomes were all-cause mortality, mortality due to CHD, and mortality due to CVD. Cox regression analysis was used to quantify the mortality risk according to E-ECG responses.RESULTS: During a follow-up of 14 years, 633 deaths (242 CVD and 150 CHD) were identified. Mortality rates and hazard ratios (HRs) across E-ECG responses were the following: for all-cause mortality: HR, 1.36; 95% confidence interval (CI), 1.09-1.70 for equivocal responses and HR, 1.41; 95% CI, 1.12-1.77 for abnormal responses (Ptrend<.001); for mortality due to CVD: HR, 1.29; 95% CI, 0.88-1.88 for equivocal responses and HR, 2.04; 95% CI, 1.46-2.84 for abnormal responses (Ptrend<.001); and for mortality due to CHD: HR, 1.62; 95% CI, 1.02-2.56 for equivocal responses and HR, 2.45; 95% CI, 1.62-3.69 for abnormal responses (Ptrend<.001). A positive gradient for CHD, CVD, and all-cause mortality rates across E-ECG categories within 3, 4, or 5 MetS components was observed (P<.001 for all).CONCLUSION: Among men with MetS, an abnormal E-ECG response was associated with higher risk of all-cause, CVD, and CHD mortality. These findings underscore the importance of E-ECG tests to identify men with MetS who are at risk of dying.ACLS = Aerobics Center Longitudinal Study; CHD = coronary heart disease; CI = confidence interval; CRF = cardiorespiratory fitness; CVD = cardiovascular disease; DM = diabetes mellitus; ECG = electrocardiography; E-ECG = exercise ECG; HR = hazard ratio; MET = metabolic equivalent; MetS = metabolic syndrome; NDI = National Death Index; SRI = stress-recovery indexMetabolic syndrome (MetS) is a clustering of cardiovascular disease (CVD) risk factors,1 including abdominal obesity, atherogenic dyslipidemia, elevated blood pressure, and insulin resistance,2 that currently affects nearly 25% of Americans and is a growing concern because of increasing rates of obesity and hypertension.3 Because many of the components of MetS are associated with an increased risk of CVD and death, a noninvasive diagnosis of subclinical CVD in patients with MetS is important and may optimize secondary preventive interventions in this high-risk population.We showed earlier that abnormal exercise electrocardiographic (E-ECG) results during maximal exercise testing was associated with an elevated risk of incident coronary heart disease (CHD), CVD, and all-cause mortality in 2854 men with diabetes mellitus (DM).4 Thus, although DM is considered a CHD risk equivalent, important additional information for risk stratification can be obtained from exercise testing. We also showed that exercise testing can be used to identify women with impaired fasting glucose, a predecessor to DM and MetS, who are at high risk of all-cause mortality.5 Callaham et al6 studied 1747 US veterans with DM and showed that exercise-induced ST-segment depression was associated with more CVD events during a mean follow-up of 2 years than was observed in participants without ST-segment depression. In a study of 45 patients with exercise-induced silent ischemia, Weiner et al7 reported that patients with DM had worse outcomes in terms of CVD events than persons without DM.Currently, no known studies have evaluated the association between abnormal E-ECG responses and all-cause, CHD, and CVD mortality risk in men with MetS. Although sparse, some studies have examined the association between E-ECG responses and CHD risk in men with components of MetS. Ekelund et al8 reported that positive findings on E-ECG was an independent predictor of CVD events in men with hypercholesterolemia. Laukkanen et al9 reported that exercise-induced ischemia was associated with a higher risk of adverse outcomes in persons at high risk of CHD. Bigi et al10 suggested that the stress-recovery index (SRI) predicts all-cause mortality in persons with hypertension.Therefore, our study primarily aimed to evaluate the association between abnormal E-ECG test results and mortality (all-cause and that due to CHD or CVD) in a large population of asymptomatic men with MetS. We showed earlier that a maximal E-ECG test performed in asymptomatic men free of CVD can predict future risk of CHD death,11 and that an abnormal test result was a more powerful predictor of risk in those with DM than those without the diagnosis.4 The current study will expand this earlier report and focus on men with MetS.  相似文献   
97.
98.
We aimed to investigate alterations in functional brain networks and assess the relationship between functional impairment and topological network changes in cerebral small vessel disease (CSVD) patients with and without cerebral microbleeds (CMBs). We constructed individual whole‐brain, region of interest (ROI) level functional connectivity (FC) networks for 24 CSVD patients with CMBs (CSVD‐c), 42 CSVD patients without CMBs (CSVD‐n), and 36 healthy controls (HCs). Then, we used graph theory analysis to investigate the global and nodal topological disruptions between groups and relate network topological alterations to clinical parameters. We found that both the CSVD and control groups showed efficient small‐world organization in FC networks. However, compared to CSVD‐n patients and controls, CSVD‐c patients exhibited a significantly decreased clustering coefficient, global efficiency, and local efficiency and an increased shortest path length, indicating a disrupted balance between local specialization and global integration in FC networks. Although both the CSVD and control groups showed highly similar hub distributions, the CSVD‐c group exhibited significantly altered nodal betweenness centrality (BC), mainly distributed in the default mode network (DMN), attention, and visual functional areas. There were almost no global or regional alterations between CSVD‐n patients and controls. Furthermore, the altered nodal BC of the right anterior/posterior cingulate gyrus and left cuneus were significantly correlated with cognitive parameters in CSVD patients. These results suggest that CSVD patients with and without CMBs had segregated disruptions in the topological organization of the intrinsic functional brain network. This study advances our current understanding of the pathophysiological mechanisms underlying CSVD.  相似文献   
99.
目的 通过hMeDIP-chip技术,在全基因组范围内分析尿毒症患者的5-羟甲基胞嘧啶(5-hmC)状态.方法 采用hMeDIP-chip技术筛选出5-hmC水平差异显著的目的基因,并用QRT-PCR验证hMeDIP-chip结果可靠性.结果 实验筛选得到3个目的基因:HMGCR、THBD、STAT3,其结果与hMeDIP-chip结果相符,证明hMeDIP-chip结果可靠.结论 尿毒症患者DNA 5-hmC状态有很大变化,这些变化或许可以进一步揭示尿毒症的发病机制,5-hmC或可作为尿毒症的潜在生物标志物和治疗靶点.  相似文献   
100.
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