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   1364篇
  免费   110篇
  国内免费   2篇
耳鼻咽喉   27篇
儿科学   60篇
妇产科学   14篇
基础医学   163篇
口腔科学   12篇
临床医学   166篇
内科学   253篇
皮肤病学   34篇
神经病学   128篇
特种医学   118篇
外科学   132篇
综合类   26篇
预防医学   187篇
眼科学   14篇
药学   83篇
中国医学   5篇
肿瘤学   54篇
  2023年   5篇
  2022年   5篇
  2021年   16篇
  2020年   11篇
  2019年   17篇
  2018年   20篇
  2017年   27篇
  2016年   21篇
  2015年   16篇
  2014年   34篇
  2013年   59篇
  2012年   53篇
  2011年   47篇
  2010年   52篇
  2009年   61篇
  2008年   45篇
  2007年   47篇
  2006年   47篇
  2005年   55篇
  2004年   38篇
  2003年   57篇
  2002年   47篇
  2001年   27篇
  2000年   29篇
  1999年   29篇
  1998年   30篇
  1997年   45篇
  1996年   33篇
  1995年   28篇
  1994年   29篇
  1993年   25篇
  1992年   29篇
  1991年   20篇
  1990年   22篇
  1989年   45篇
  1988年   34篇
  1987年   38篇
  1986年   38篇
  1985年   29篇
  1984年   20篇
  1983年   15篇
  1982年   14篇
  1981年   12篇
  1980年   8篇
  1979年   9篇
  1978年   9篇
  1977年   14篇
  1976年   11篇
  1975年   13篇
  1969年   5篇
排序方式: 共有1476条查询结果,搜索用时 0 毫秒
61.
62.
Perhaps the most significant link in achieving the nation's immunization objectives is the extent of parental knowledge. Admittedly, this is a weak link. The 1990 federal objectives calling for an official format using common guidelines for completion of immunizations, though well-conceived, has not been used exclusively by health care givers. The lack of accord has permitted the proliferation of many different immunization records that are not only confusing to parents, but also to health care providers at times. A standard national immunization record could be an essential element in strengthening the weak link of parental knowledge of immunizations and stressing the importance of preserving such a record for a lifetime.  相似文献   
63.
OBJECTIVE: We tested the hypothesis that subjects randomized to the 6 mL/kg predicted body weight tidal volume study group of the National Institutes of Health Acute Respiratory Distress Syndrome (ARDS) Network study had higher levels of intrinsic positive end-expiratory pressure (PEEP) than subjects randomized to the 12 mL/kg predicted body weight tidal volume study group. DESIGN: Secondary analysis of a subgroup from a randomized controlled trial. SETTING: Hospitals located in San Francisco, CA, and Seattle, WA. PATIENTS: Eighty-four patients enrolled in the ARDS Network tidal volume trial in San Francisco, CA, and Seattle, WA, with records of measurement of intrinsic PEEP. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Intrinsic PEEP was assessed a median of six times over the first 48 hrs of ARDS Network protocol ventilation in study subjects, with no significant difference in number of measurements between subjects randomized to the tidal volume protocol of 6 mL/kg compared with 12 mL/kg. We found that intrinsic PEEP was higher among subjects randomized to the 6 mL/kg protocol, with a median intrinsic PEEP of 1.3 cm H2O (interquartile range, 0-3.1 cm H2O), compared with a median intrinsic PEEP of 0.5 cm H2O (interquartile range, 0-1.5 cm H2O) among subjects randomized to 12 mL/kg (p = .029). There was no difference in total PEEP between the study groups. CONCLUSIONS: In a subgroup of ARDS Network subjects, intrinsic PEEP was statistically significantly higher in subjects randomized to the 6 mL/kg protocol than those in the 12 mL/kg study group. The amount of intrinsic PEEP was very low in both study groups, and difference of median intrinsic PEEP between the groups was <1 cm H2O. It is unlikely that the difference in intrinsic PEEP between the study groups was clinically important in the ARDS Network study of low tidal volume ventilation.  相似文献   
64.
The antinociceptive profile of selected histamine H(2) and histamine H(3) receptor antagonists led to the discovery of improgan, a non-brain-penetrating analgesic agent which does not act on known histamine receptors. Because no chemical congener of improgan has yet been discovered which has both antinociceptive and brain-penetrating properties, the present study investigated the antinociceptive effects of a series of chemical compounds related to zolantidine, a brain-penetrating histamine H(2) receptor antagonist. The drugs studied presently contain the piperidinomethylphenoxy (PMPO) moiety, hypothesized to introduce brain-penetrating characteristics. Following intracerebroventricular (i.c.v.) dosing in rats, six of eight drugs produced dose- and time-related antinociception on both the tail flick and hot plate tests over a nearly eight-fold range of potencies. Ataxia and other motor side effects were observed after high doses of these drugs, but two of the compounds (SKF94674 and loxtidine) produced maximal antinociception at doses which were completely devoid of these motor effects. Consistent with the hypothesis that PMPO-containing drugs are brain-penetrating analgesics, SKF94674 and another derivative (JB-9322) showed dose-dependent antinociceptive activity 15 to 30 min after systemic dosing in mice, but these effects were accompanied by seizures and death beginning 45 min after dosing. Other drugs showed a similar pattern of antinociceptive and toxic effects. In addition, loxtidine produced seizures without antinociception, whereas zolantidine produced neither effect after systemic dosing in mice. Although several of the drugs tested have histamine H(2) receptor antagonist activity, neither the antinociception nor the toxicity was correlated with histamine H(2) receptor activity. The present results are the first to demonstrate the existence of brain-penetrating antinociceptive agents chemically related to zolantidine and improgan, but further studies are needed to understand the mechanisms of both the pain relief and toxicity produced by these agents.  相似文献   
65.
We examined the mother–child adjustment and child behavior problems in Arab Muslim immigrant families residing in the U.S.A. The sample of 635 mother–child dyads was comprised of mothers who emigrated from 1989 or later and had at least one early adolescent child between the ages of 11 and 15 years old who was also willing to participate. Arabic speaking research assistants collected the data from the mothers and children using established measures of maternal and child stressors, coping, and social support; maternal distress; parent–child relationship; and child behavior problems. A structural equation model (SEM) was specified a priori with 17 predicted pathways. With a few exceptions, the final SEM model was highly consistent with the proposed model and had a good fit to the data. The model accounted for 67% of the variance in child behavior problems. Child stressors, mother–child relationship, and maternal stressors were the causal variables that contributed the most to child behavior problems. The model also accounted for 27% of the variance in mother–child relationship. Child active coping, child gender, mother's education, and maternal distress were all predictive of the mother–child relationship. Mother–child relationship also mediated the effects of maternal distress and child active coping on child behavior problems. These findings indicate that immigrant mothers contribute greatly to adolescent adjustment, both as a source of risk and protection. These findings also suggest that intervening with immigrant mothers to reduce their stress and strengthening the parent–child relationship are two important areas for promoting adolescent adjustment.  相似文献   
66.
Histamine-synthesizing neurons in the brain may play an important role in cognition, and a histaminergic deficit has been found in Alzheimer's disease (AD). The AD medication tacrine was previously shown to inhibit some forms of rodent histamine-N-methyltransferase (HNMT), but the effects of AD drugs have not been investigated on human HNMT activity. Presently, the effects of tacrine and galanthamine (another AD medication) were studied on the activity of several forms of human and rat HNMT. Tacrine (0.01-10 microM) inhibited both human and rat HNMT activity in a concentration-dependent manner, but was less potent on both human embryonic kidney and recombinant human brain HNMT than on rat kidney HNMT (IC50 values were 0.46 and 0.70 microM vs. 0.29 microM, respectively). Galanthamine (up to 10 microM) did not influence the activity of rat kidney or human HNMT. Tacrine, but not galanthamine, may achieve brain levels sufficient to influence histamine metabolism in some patients treated for AD.  相似文献   
67.

Background and Purpose

The Ca2+-permeable cation channel TRPV4 is activated by mechanical disturbance of the cell membrane and is implicated in mechanical hyperalgesia. Nerve growth factor (NGF) is increased during inflammation and causes mechanical hyperalgesia. 4α-phorbol 12,13-didecanoate (4αPDD) has been described as a selective TRPV4 agonist. We investigated NGF-induced hyperalgesia in TRPV4 wild-type (+/+) and knockout (–/–) mice, and the increases in [Ca2+]i produced by 4αPDD in cultured mouse dorsal root ganglia neurons following exposure to NGF.

Experimental Approach

Withdrawal thresholds to heat, von Frey hairs and pressure were measured in mice before and after systemic administration of NGF. Changes in intracellular Ca2+ concentration were measured by ratiometric imaging with Fura-2 in cultured DRG and trigeminal ganglia (TG) neurons during perfusion of TRPV4 agonists.

Key Results

Administration of NGF caused a significant sensitization to heat and von Frey stimuli in TRPV4 +/+ and –/– mice, but only TRPV4 +/+ mice showed sensitization to noxious pressure. 4αPDD stimulated a dose-dependent increase in [Ca2+]i in neurons from +/+ and –/– mice, with the proportion of responding neurons and magnitude of increase unaffected by the genotype. In contrast, the selective TRPV4 agonist GSK1016790A failed to stimulate an increase in intracellular Ca2+ in cultured neurons. Responses to 4αPDD were unaffected by pretreatment with NGF.

Conclusions and Implications

TRPV4 contributes to mechanosensation in vivo, but there is little evidence for functional TRPV4 in cultured DRG and TG neurons. We conclude that 4αPDD activates these neurons independently of TRPV4, so it is not appropriate to refer to 4αPDD as a selective TRPV4 agonist.  相似文献   
68.
Despite the wide array of antihypertensive agents and the availability of national guidelines regarding treatment for hypertension, the disease remains uncontrolled in nearly 50% of affected patients. Furthermore, the number of patients with resistant hypertension continues to increase. For patients with resistant hypertension, the American Heart Association has advocated for clinical studies to determine appropriate pharmacologic treatment strategies. One proposed strategy involves ambulatory measurement of plasma renin activity (PRA) to guide the selection of antihypertensive therapy. Patients with low PRA would be prescribed natriuretic volume-mediated therapies (e.g., diuretics and calcium channel blockers), whereas those with high PRA would receive antirenin system therapies (e.g., β-blockers, angiotensin-converting enzyme inhibitors, and angiotensin II receptor blockers). This review focuses on the principles of PRA-guided therapy, its historical development, alternative approaches to classifying patients into categories of response to antihypertensive agents, and recent data supporting the use of plasma renin activity-guided hypertension management.  相似文献   
69.
Multiple sources of resistance are present in the healthcare environment to comprehensive assessment and intervention efforts in regard to sexuality. The authors survey both the diversity of needs and values presented by consumers, and encourage providers to equip themselves educationally, emotionally and ethically so that they can deliver relevant, holistic services to consumers.  相似文献   
70.

Background  

To determine differences among persons who provided blood specimens for HIV testing compared with those who did not among those interviewed for the population-based Zimbabwe Young Adult Survey (YAS).  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