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   845篇
  免费   60篇
  国内免费   23篇
耳鼻咽喉   4篇
儿科学   38篇
妇产科学   10篇
基础医学   105篇
口腔科学   65篇
临床医学   84篇
内科学   198篇
皮肤病学   18篇
神经病学   51篇
特种医学   99篇
外科学   66篇
综合类   19篇
预防医学   45篇
眼科学   17篇
药学   65篇
中国医学   1篇
肿瘤学   43篇
  2021年   15篇
  2020年   7篇
  2019年   6篇
  2018年   14篇
  2017年   6篇
  2015年   10篇
  2014年   17篇
  2013年   22篇
  2012年   30篇
  2011年   27篇
  2010年   34篇
  2009年   19篇
  2008年   23篇
  2007年   48篇
  2006年   25篇
  2005年   31篇
  2004年   21篇
  2003年   18篇
  2002年   25篇
  2001年   17篇
  2000年   17篇
  1999年   25篇
  1998年   19篇
  1997年   28篇
  1996年   17篇
  1995年   17篇
  1994年   11篇
  1993年   17篇
  1992年   16篇
  1991年   17篇
  1990年   23篇
  1989年   43篇
  1988年   40篇
  1987年   27篇
  1986年   30篇
  1985年   18篇
  1984年   15篇
  1983年   8篇
  1982年   9篇
  1981年   5篇
  1980年   5篇
  1979年   7篇
  1978年   7篇
  1977年   16篇
  1976年   14篇
  1974年   8篇
  1973年   9篇
  1972年   6篇
  1969年   4篇
  1968年   6篇
排序方式: 共有928条查询结果,搜索用时 78 毫秒
61.
Although the introduction of angiotensin-converting enzyme (ACE) inhibitors and β-adrenergic blockers has resulted in significant improvements in the management of heart failure (HF), morbidity and mortality remain high. Therefore, additional approaches have been sought to discover newer agents that might add incremental benefit. Although not all of these approaches have been successful, there have been some notable new approaches to therapy that have shown benefit or may be promising in terms of additional benefit. Most of these agents are targeted to achieve a more global neurohormonal blockade aiming to reduce or potentially reverse the ventricular remodeling process that occurs in HF. Some of the newer approaches aim for targets other than neurohormonal systems, eg, effects on myocardial metabolism or the vasculature. This article reviews the latest advances in pharmacologic therapy in HF, looking at several trials that may have a significant impact on the treatment of HF. We also discuss several newer agents with promising potential in HF management.  相似文献   
62.
63.
Augmentation index (AI), a measure of enhanced wave reflection, has been proposed as a bedside measure of aortic stiffness. However, because AI is potentially sensitive to various factors other than vessel wall stiffness, the utility of AI as a stiffness indicator may be limited. To assess relations between AI and vascular properties, we used arterial tonometry and aortic Doppler flow to evaluate trough (24 hours) and peak (4 hours) pulsatile hemodynamics and pulse wave velocity in 159 individuals with systolic hypertension at the completion of a 12-week period of monotherapy with the vasopeptidase inhibitor omapatrilat (80 mg; n=75) or the converting enzyme inhibitor enalapril (40 mg; n=84). Characteristic impedance (Zc) was calculated from the ratio of change in carotid pressure and aortic flow in early systole. Systolic ejection period (SEP), timing of wave reflection, and AI were assessed from the carotid waveform. Comparable acute reductions in mean pressure were associated with greater reductions in peripheral resistance with enalapril, whereas neither drug had an acute effect on Zc. Both drugs reduced AI, but neither drug altered the timing of wave reflection. Both drugs increased heart rate and shortened SEP. Multiple regression analysis demonstrated that the acute reduction in AI was most affected by reductions in SEP and peripheral resistance. Change in AI was inversely related to change in Zc and pulse wave velocity did not enter the model. Our findings indicate that AI is a complex surrogate marker that is inversely related to changes in proximal aortic stiffness in systolic hypertension.  相似文献   
64.
65.
This study was designed primarily to evaluate the effectiveness of landscape coverings to reduce the potential for exposure to lead-contaminated soil in an urban neighborhood. Residential properties were randomized in to three groups: application of ground coverings/barriers plus placement of a raised garden bed (RB), application of ground coverings/barriers only (no raised bed, NRB), and control. Outcomes evaluated soil lead concentration (employing a weighting method to assess acute hazard soil lead [areas not fully covered] and potential hazard soil lead [all soil surfaces regardless of covering status]), density of landscape coverings (6 = heavy, > 90% covered; 1 = bare, < 10% covered), lead tracked onto carpeted entryway floor mats, and entryway floor dust lead loadings. Over 1 year, the intervention groups had significantly reduced acute hazard soil lead concentration (median change: RB, -478 ppm; NRB, -698 ppm; control, +52 ppm; Kruskal-Wallis, P = 0.02), enhanced landscape coverings (mean change in score: RB, +0.6; NRB, +1.5; control, -0.6; ANOVA, P < 0.001), and a 50% decrease in lead tracked onto the floor mats. The potential hazard soil lead concentration and the entryway floor dust lead loading did not change significantly. Techniques evaluated by this study are feasible for use by property owners but will require continued maintenance. The long-term sustainability of the method needs further examination.  相似文献   
66.
Excessive sebum production is a central aspect of the pathophysiology of acne vulgaris. Sebaceous gland function is under androgen control and it is hypothesized that dihydrotestosterone is formed by the action of 5 alpha-reductase. Type I is the controlling isoenzyme. This study describes a 3-month, multicenter, randomized, placebo-controlled clinical trial with a potent, selective inhibitor of type I 5 alpha-reductase used alone and in combination with systemic minocycline. Inhibition of type I 5 alpha-reductase was not associated with clinical improvement of acne when used alone and did not enhance the clinical benefit of systemic minocycline. These results indicate the need for further work at the molecular level to better understand the action of androgens on sebaceous gland function.  相似文献   
67.
Radiotherapy with external beam radiation or brachytherapy is an established therapeutic modality for prostate cancer. Approximately 30% of patients with localised prostate cancer relapse at the irradiated site. Secondary effects of ionising radiation (IR), for example, bowel and bladder complications, are common. Thus, the search for biological response modifiers that could potentiate the therapeutic effects of radiation and limit the occurrence of serious side effects is an important task in prostate cancer therapy. 1alpha,25-Dihydroxyvitamin D(3) (calcitriol), the active metabolite of vitamin D, and its analogues are under investigation for the treatment of several malignancies including prostate cancer. Here, we report that 1alpha,25-dihydroxyvitamin D(3) and its less calcaemic analogue 19-nor-1alpha,25-(OH)(2)D(2) (Zemplar) act synergistically with IR to inhibit the growth of the human prostate cancer cells in vitro. 1alpha,25-dihydroxyvitamin D(3) potentiated IR-induced apoptosis of LNCaP cells, and nanomolar doses of 1alpha,25-dihydroxyvitamin D(3) and 19-nor-1alpha,25-(OH)(2)D(2) showed synergistic inhibition of growth of LNCaP cells at radiobiologically relevant doses of IR (1-2 Gy). At higher doses of IR, the combination of 1alpha,25-dihydroxyvitamin D(3) and IR or 19-nor-1alpha,25-(OH)(2)D(2) and IR resulted in moderate antagonism. The synergistic effect at radiobiologically relevant doses of radiation suggests that a combination of 1alpha,25-dihydroxyvitamin D(3) or 19-nor-1alpha,25-(OH)(2)D(2) with IR could permit a reduction in the dose of radiation given clinically and thus potentially reduce treatment-related morbidity.  相似文献   
68.
Id proteins in cell growth and tumorigenesis   总被引:8,自引:0,他引:8  
Since the gene encoding Id1 was cloned in 1990, Id proteins have been implicated in regulating a variety of cellular processes, including cellular growth, senescence, differentiation, apoptosis, angiogenesis, and neoplastic transformation. The development of knockout and transgenic animal models for many members of the Id gene family has been particularly useful in sorting out the biologic relevance of these genes and their expression during normal development, malignant transformation, and tumor progression. Here we review the current understanding of Id gene function, the biologic consequences of Id gene expression, and the implications for Id gene regulation of cell growth and tumorigenesis.  相似文献   
69.
A novel alpha-tocomonoenol 3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyl-12-tridecenyl )-2H-1- benzopyran-6-ol[ having an unusual methylene unsaturation at the isoprenoid-chain terminus of alpha-tocopherol was isolated from the lipophilic fraction of chum salmon eggs. The structure of this marine-derived tocopherol (MDT) was established by spectral analyses. The peroxyl radical-trapping activities of MDT and alpha-tocopherol were compared in aqueous phosphatidylcholine liposomal suspension and in methanolic solution at 37 degrees C. The antioxidant activity of MDT was found to be identical to that of alpha-tocopherol under the experimental conditions of measurement.  相似文献   
70.
筛窦癌发病率低,就诊时病期晚,5年无瘤生存率为30%~50%。由于解剖部位的限制以及局部浸润,放射和手术均有一定难度。作者回顾性分析皇家Margret医院1976~1994年收治的29例浸润性筛窦癌根治性放射治疗的疗效和影响预后因素。男性24例,女性4例,中位年龄62岁,中位随访时间4年。常有鼻出血、鼻塞、疼痛及视力改变等。起病到确诊的平均时间为9个月。27例吸烟,10例从事伐木或镍的开采与提炼。  治疗前均经临床及影像学检查。仅3例局限于筛窦,余侵犯鼻腔、蝶窦、眼眶、上颌窦、额窦及脑内等。T1…  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