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   911篇
  免费   78篇
  国内免费   6篇
耳鼻咽喉   4篇
儿科学   36篇
妇产科学   8篇
基础医学   80篇
口腔科学   35篇
临床医学   87篇
内科学   238篇
皮肤病学   12篇
神经病学   14篇
特种医学   250篇
外科学   93篇
综合类   17篇
预防医学   32篇
眼科学   16篇
药学   27篇
肿瘤学   46篇
  2023年   6篇
  2022年   6篇
  2021年   7篇
  2020年   15篇
  2019年   2篇
  2018年   14篇
  2017年   21篇
  2016年   17篇
  2015年   18篇
  2014年   31篇
  2013年   26篇
  2012年   33篇
  2011年   28篇
  2010年   42篇
  2009年   34篇
  2008年   17篇
  2007年   25篇
  2006年   13篇
  2005年   17篇
  2004年   16篇
  2003年   5篇
  2002年   9篇
  2001年   6篇
  2000年   4篇
  1999年   8篇
  1998年   46篇
  1997年   57篇
  1996年   53篇
  1995年   48篇
  1994年   46篇
  1993年   30篇
  1992年   13篇
  1991年   11篇
  1990年   11篇
  1989年   20篇
  1988年   31篇
  1987年   15篇
  1986年   40篇
  1985年   36篇
  1984年   17篇
  1983年   21篇
  1982年   18篇
  1981年   10篇
  1980年   10篇
  1979年   2篇
  1978年   7篇
  1977年   11篇
  1976年   16篇
  1975年   4篇
  1969年   1篇
排序方式: 共有995条查询结果,搜索用时 31 毫秒
101.
The new U.S. National Osteoporosis Foundation Clinician's Guide to Prevention and Treatment of Osteoporosis includes criteria for recommending pharmacologic treatment based on history of hip or vertebral fracture, femoral neck (FN), or spine BMD T‐scores ≤?2.5 and presence of low bone mass at the FN or spine plus a 10‐yr risk of hip fracture ≥3% or of major osteoporotic fracture ≥20%. The proportion of women who would be recommended for treatment by these guidelines is not known. We applied the NOF criteria for treatment to women participating in the Study of Osteoporotic Fractures (SOF). To determine how the SOF population differs from the general U.S. population of white women ≥65 yr of age, we compared women in SOF with women who participated in the National Health and Nutrition Examination Survey (NHANES) III on criteria included in the NOF treatment guidelines that were common to both cohorts. Compared with NHANES III, women in SOF had higher FN BMD and were younger. Application of NOF guidelines to SOF data estimated that at least 72% of U.S. white women ≥65 yr of age and 93% of those ≥75 yr of age would be recommended for drug treatment. Application of the new NOF Guidelines would result in recommending a very large proportion of white women in the United States for pharmacologic treatment of osteoporosis.  相似文献   
102.
Platelets have a central role in the development of arterial thrombosis and subsequent cardiovascular events. An appreciation of this complex process has made antiplatelet therapy the cornerstone of cardiovascular disease management. However, numerous patients will experience a recurrent atherothrombotic vascular event despite adequate antiplatelet therapy. Individual differences in the rate of platelet activation and reactivity markedly influence normal hemostasis and the pathological outcome of thrombosis. Such an individual variability is largely determined by environmental and genetic factors. These are known to either hamper platelets' response to agonists, and thereby mimic the pharmacological modulation of platelet function or mask therapy effect and sensitize platelets. In this article, we reviewed the antiplatelet mechanisms of aspirin and clopidogrel and the possible role of different polymorphisms, which may affect the efficacy of antiplatelet therapy. Heterogeneity in the way patients respond to aspirin and clopidogrel may in part reflect variation in cyclooxygenase (COX)-1, COX-2, glycoprotein (GP) Ib alpha, GP Ia/IIa, GP IIb/IIIa, UGT1A6*2, P2Y1, P2Y12, CYP2C9, CYP3A4 and CYP3A5 genotypes.  相似文献   
103.
104.
105.

Background

Sarcopenia, a reduction in skeletal muscle mass and function, is a condition that contributes to functional decline and disability in older adults. Although research on this geriatric condition has developed rapidly in recent years, little work has been done to document whether practicing physicians are incorporating sarcopenia into their clinical practice.

Methods

An online survey of 253 practicing U.S. physicians assessed knowledge of sarcopenia, use of the term in practice, motivation for screening patients, and diagnostic and treatment approaches. They were board certified in four practice areas: internal medicine (n = 69), family medicine (n = 69), geriatrics (n = 40), or physical medicine and rehabilitation (PM&R) (n = 75).

Results

Less than 20% of internists and family medicine physicians reported being very familiar with the term sarcopenia, with substantially higher familiarity at this level reported among geriatricians (70%) and among PM&R specialists (41%). Two additional findings pointed to deficiencies in sarcopenia knowledge and practice: participants substantially overestimated the prevalence of sarcopenia in older adults (44% of participants reported an expected prevalence of >25%) compared to findings from published studies (indicating 10% of older adults experience sarcopenia); over 75% reported not typically using specific diagnostic criteria or being unsure if their approach utilized any specific criteria. When asked what terminology they use in a medical chart for a patient presenting with significant loss of muscle mass and strength, only 8% said sarcopenia.

Conclusions

Sarcopenia, a condition that can have a major impact on older adults as they age, has not been fully incorporated into the knowledge base and practices of active physicians. The survey data suggest that improving physician familiarity with sarcopenia and having universal agreement on criteria for diagnosis may increase the screening for and treatment of sarcopenia.  相似文献   
106.
Experiments were designed to determine the effect of CRL 41034, a buflomedil analogue, on the adrenergic responsiveness of canine veins. Rings of saphenous vein (without endothelium) were suspended for isometric tension recording in modified Krebs-Ringer bicarbonate solution at 37 degrees C. CRL 41034 produced a concentration-dependent inhibition of the contractions evoked by the alpha adrenergic agonists norepinephrine, phenylephrine and UK 14304 which was insensitive to the blockade of neuronal uptake by cocaine. CRL 41034 was more potent in inhibiting the concentration-dependent contractions evoked by UK 14304 than those by phenylephrine and the antagonism it caused against the response to UK 14304 fulfilled the criteria for competitivity. CRL 41034, at 10(-5) M significantly depressed, and at 10(-4) M abolished the contractions induced by electrical stimulation of the adrenergic nerves and those evoked by the indirect sympathomimetic amine tyramine. Strips of canine saphenous vein were superfused after incubation with [3H] norepinephrine. During sympathetic nerve activation, CRL 41304 increased the stimulation-evoked overflow of [3H] norepinephrine and 3-methoxy-4-dihydroxyphenylglycol; in the presence of rauwolscine the compound only increased the stimulation-evoked overflow of 3,4-dihydroxyphenylglycol. These experiments suggest that the major vascular effects of CRL 41034 in canine veins are blockade of alpha 2-adrenoceptors on vascular smooth muscle, and inhibition of prejunctional alpha 2-adrenoceptors on adrenergic nerve endings.  相似文献   
107.
Summary— Oxidative modifications of low density lipoproteins (LDL) are now recognised as one of the major processes in atherogenesis. Various drugs, as well as a number of natural products, have been proposed to inhibit such processes. Among the naturally-occurring constituents of plants which appear to possess antioxidant activity are polyphenolic compounds such as flavonoids. The aqueous extract of Vaccinium myrtillus is rich in such molecules. In this report, we describe the in vitro antioxidative potential of this extract on human LDL. The copper-induced oxidative modification of these lipoproteins was assessed using 1) measurement of oxidative resistance as determined by the lag-phase preceding conjugated diene formation; 2) quantification of the amount of lipoperoxides and thiobarbituric acid-reactive substances generated, and measurement of the modification in the net negative electrical charge of the lipoproteins, over a 7-hour time course experiment. Trace amounts of V myrtillus extract (15 to 20 μg/mL) induce statistically significant changes in the oxidation behaviour of LDL, which include 1) prolongation of the lag-phase of conjugated diene production ( P < 0.01); 2) reduction in the formation of lipoperoxides and of thiobarbituric acid-reactive substances up to 7 hours and especially between 1 and 5 hours ( P < 0.01); and 3) inhibition of modification in the net negative charge of LDL. These results demonstrate that V myrtillus extract exerts potent protective action on LDL particles during in vitro copper-mediated oxidation. Calculation of IC50 values indicates that, on a molar basis, this extract may indeed be more potent than either ascorbic acid or butylated hydroxytoluene in the protection of LDL particles from oxidative stress.  相似文献   
108.

Background  

Computer tailoring may be a promising technique for prevention of overweight in adolescents. However, very few well-developed, evidence-based computer-tailored interventions are available for this target group. We developed and evaluated a computer-tailored intervention for adolescents targeting energy balance-related behaviours: i.e. consumption of snacks, sugar-sweetened beverages, fruit, vegetables, and fibre, physical activity, and sedentary behaviours. This paper describes the planned development of a school-based computer-tailored intervention aimed at improving energy balance-related behaviours in order to prevent excessive weight gain in adolescents, and the protocol for evaluating this intervention.  相似文献   
109.
Summary— Free radical species have been implicated as important agents involved in myocardial ischemic and reperfusion injuries. Superoxide is capable of mobilizing iron from ferritin and the released iron can cause hydroxyl formation from H2O2. The aim of this study was to evaluate the time-dependent increase in lipid peroxidation assessed by plasma thiobarbituric acid reactive substances (TBARS) and the relationship between lipid-peroxidation and the iron status. Peripheral venous blood samples were obtained from 17 men with acute myocardial infarction (AMI) before thrombolytic treatment (T0***) and 1, 2, 3, 4, 8, 12, 16, 20, 24 and 48 hours after commencing fibrinolytic treatment. The concentration of TBARS, the parameters of iron metabolism, serum myoglobin, creatine kinase, and creatine kinase-MB were measured. Early reperfusion was judged by regression of sinus tachycardia (ST) elevation and reduction of chest pain. Recanalization of coronary artery was evaluated by a late coronary angiography 24–96 hours after thrombolysis. After thrombolytic therapy, the TBARS level was raised from 2.98 ± 0.80 (T0***) to 4.57 ± 1.24 (peak), and decreased to 2.96 ± 0.40 nmol/mL plasma at T48 (T0 vs peak: P < 0.001, peak vs T48: P < 0.001, TO vs T48: NS). The mean time of the peak was observed at 9.7 ± 7.5 hours. The iron increased significantly from 0.67 ± 0.34 (T0) to 1.15 ± 0.52 mg/L (peak), and returned to the pre-reperfusion to levels: 0.53 ± 0.28 UI/L at T48 (T0 vs peak: P < 0.001, peak vs T48: P < 0.001, TO vs T48: NS). The mean time of the peak was observed at 9.4 ± 7.3 hours. In return, no correlation was found between the increase of plasma creatine-kinase activity, myoglobin and iron or between the biochemical markers and time of fibrinolytic therapy. The results confirmed the importance of the temporal relationship between lipid peroxidation and iron status after thrombolytic therapy. Our results are in agreement with the concept that antioxidant agents used in association with thrombolytic therapy might be useful.  相似文献   
110.
Abstract We tested the hypothesis that the febrile stress of routine vaccination would increase central apnoea in normal infants. Twenty-one normal infants had continuous overnight breathing and temperature recorded at home, before and after 58 routine vaccination episodes. Central apnoea, of at least 5 sec duration, was detected by computer algorithm and confirmed by human inspection. The longest recorded apnoea was 16 sec ( n = 1) during 3629 h of sleep. Overnight rectal temperature increased after vaccination (median 0.52°C, 95% CI 0.40, 0.65). Apnoea density reduced on 46/53 vaccination nights (median -29%, 95% CI -20, -37) followed by an increase on subsequent nights (median +10%, 95% CI +1%, +21%). Overall, apnoea density was similar during the 3 nights preceding and 4 nights following vaccination (median +1%, 95% CI +9,-6). The febrile stress of routine vaccination did not increase central apnoea in normal infants.  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