全文获取类型
收费全文 | 8484篇 |
免费 | 1087篇 |
国内免费 | 100篇 |
专业分类
耳鼻咽喉 | 69篇 |
儿科学 | 219篇 |
妇产科学 | 156篇 |
基础医学 | 642篇 |
口腔科学 | 718篇 |
临床医学 | 652篇 |
内科学 | 1971篇 |
皮肤病学 | 60篇 |
神经病学 | 341篇 |
特种医学 | 51篇 |
外科学 | 371篇 |
综合类 | 454篇 |
预防医学 | 1787篇 |
眼科学 | 53篇 |
药学 | 1121篇 |
中国医学 | 27篇 |
肿瘤学 | 979篇 |
出版年
2024年 | 2篇 |
2023年 | 84篇 |
2022年 | 98篇 |
2021年 | 250篇 |
2020年 | 254篇 |
2019年 | 305篇 |
2018年 | 311篇 |
2017年 | 356篇 |
2016年 | 328篇 |
2015年 | 325篇 |
2014年 | 490篇 |
2013年 | 926篇 |
2012年 | 388篇 |
2011年 | 422篇 |
2010年 | 378篇 |
2009年 | 410篇 |
2008年 | 463篇 |
2007年 | 395篇 |
2006年 | 388篇 |
2005年 | 346篇 |
2004年 | 301篇 |
2003年 | 277篇 |
2002年 | 268篇 |
2001年 | 232篇 |
2000年 | 196篇 |
1999年 | 161篇 |
1998年 | 135篇 |
1997年 | 157篇 |
1996年 | 129篇 |
1995年 | 117篇 |
1994年 | 94篇 |
1993年 | 81篇 |
1992年 | 82篇 |
1991年 | 74篇 |
1990年 | 65篇 |
1989年 | 61篇 |
1988年 | 42篇 |
1987年 | 49篇 |
1986年 | 35篇 |
1985年 | 29篇 |
1984年 | 41篇 |
1983年 | 26篇 |
1982年 | 26篇 |
1981年 | 16篇 |
1980年 | 18篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1975年 | 5篇 |
排序方式: 共有9671条查询结果,搜索用时 31 毫秒
101.
Gerhard Scherer 《Psychopharmacology》1999,145(1):1-20
Rationale: Compensation or compensatory smoking, accurately defined, deals with the question of whether switching to cigarette brands
with different smoke yields is associated with a change in smoke uptake proportional to the change in machine-derived yields.
The issue of compensation is important because it bears on whether switching to ”lighter” brands means lower overall smoke
intake or not. Objectives: The present review investigated whether and to what extend low yield cigarettes are smoked more intensively. In addition,
published data on whether nicotine, ”tar”, or any other smoke constituent or property influence compensational smoking are
summarized. Methods: The studies on compensation were classified as follows: (1) studies on smoking behaviour in relation to cigarette yields
(with and without brand switching); (2) studies on compensation for nicotine (switching between cigarettes which differ ”only”
in their nicotine yield, nicotine supplementation, manipulation of renal nicotine excretion, administration of nicotine agonists
or antagonists); (3) studies on compensation for other factors (influence of tar, taste, irritation, draw resistance). In
order to quantify the degree of compensation, an index is defined and applied to selected brand switching studies. This compensation
index determines, in relative units, the degree to which a smoker responds to a change in smoke yields with a change in smoke
uptake measured by suitable biomarkers. The role of vent blocking is also briefly discussed. Results: Most of the studies which compare the smoking behaviour when smoking cigarettes with different smoke yields supply evidence
for ”partial” compensation, suggesting that cigarettes with lower yields are smoked more intensively than those with higher
yields. These studies also show that a change in the daily number of cigarettes is not a common mechanism of compensation.
Effective vent blocking during smoking is a rare event and can therefore also be regarded as an uncommon mechanism of compensation.
Evaluation of a suitable subset of brand-switching studies revealed an average compensation of 50–60% of the nicotine yield.
Compensation tended to be more complete when changing to cigarettes with higher yields than when changing to cigarettes with
lower yields. In general, brand-switching studies do not supply information on the underlying causal factors responsible for
compensatory smoking. Results of the nicotine supplementation studies are not conclusive: some report evidence of nicotine
titration, others do not. A general problem with this type of investigation is that continuous nicotine application does not
mimic the spike-wise application with cigarette smoking, and may lead to nicotine tolerance. There is limited evidence that
cigarettes were smoked more intensively when the urinary clearance of nicotine was increased. A small number of studies provide
some evidence that smoking intensity increased after smokers were administered a nicotine antagonist. Several reports indicate
that tar, taste and sensory properties of the smoke as well as the draw resistance of the cigarette may play a role in compensatory
smoking. Low-yield cigarettes usually have reduced pressure drops which smoke researchers have suggested leads to increased
puff volume. This effect seems to be independent of the smoke yield of the cigarette. There is also some evidence that some
smokers maintain a consistent pattern of smoking which works independent of any changes in nicotine or tar yields, taste or
design features of the cigarette (”functional autonomy”). Conclusions: The available data suggest that smokers partially compensate for a different smoke yield. While the factors and their interaction
responsible for compensational smoking are not fully understood, there are data suggesting that a subgroup of smokers may
partially compensate for nicotine. Even in this subgroup of smokers, however, the relative importance of the pharmacological
versus the sensory effects of nicotine in smoke remains to be determined.
Received: 4 January 1999 / Final version: 22 March 1999 相似文献
102.
Lam T. H.; Jiang C. Q.; Liu W. W.; Zhang W. S.; He J. M.; Zhu C. Q. 《Occupational medicine (Oxford, England)》1996,46(5):351-355
This cross-sectional study aimed to describe the pattern ofsmoking in relation to occupational hazard exposure in a workingpopulation in Guangzhou, China. In 1994, data on smoking andoccupational hazard exposure from occupational health recordsof 8,304 subjects aged 35 years or older from 47 randomly selectedfactories were studied. About 49% of the men and 55% of thewomen were exposed to dust, chemicals or other hazards. Theprevalence of smoking was 56.1% in men and in women. The prevalenceof smoking in men was higher in those who were younger, withprimary education or who were workers. In women, those who wereolder, with primary education or in management jobs had highersmoking prevalence. In men and women, subjects who were exposedto occupational hazards had higher smoking prevalence: the highest(71.6%) was found in male workers exposed to dust. Urgent tobaccocontrol measures are needed to prevent the epidemic of smoking-relatedand occupation-related diseases in the workplace in China. 相似文献
103.
This article presents findings from a survey of programmes available for tobacco and alcohol users working in 455 of Australia's top 600 companies. Companies were twice as likely to have programmes for smokers (43%) as for problem drinkers (24%) and these programmes were more apparent in large companies. The majority of programmes for smoking were delivered within a health promotion context which included other life-style issues, such as nutrition, exercise, weight management and stress management. Although Employee Assistance Programs (EAPs) were the most commonly available type of work-place programme for excessive drinkers and other drug users, followed by Alcoholics Anonymous and local hospital clinics, only 6% had an EAP for alcohol. Only 21% of programmes for smokers and 12% for excessive alcohol users were evaluated. Around one-quarter of companies knew the costs of smoking programmes, and 9% reported costs of conducting programmes for excessive alcohol consumers. 相似文献
104.
In a telephone survey of 455 of the top 600 companies in Australia, around three-quarters reported the existence of restrictions on both smoking and alcohol in the workplace. Forty-six percent of companies had a total ban on smoking at work, 31% had designated limited areas where employees were permitted to smoke, and 23% had no policy on smoking. Seventy-seven percent of companies encouraged a total alcohol-free work environment. The larger the company, the more likely it was to have restrictions on smoking in the work-place, but there was no relationship between the size of the company and alcohol restrictions. Government organizations were more likely to have restrictions on smoking than nongovernment organizations, but this difference was not apparent for alcohol restrictions. The major reasons given for smoking restrictions were related to health and comfort, while those for alcohol were related to work productivity and safety. 相似文献
105.
Summary
- ? The aim of this small-scale study was to assess the feasibility and impact of an individualized smoking cessation intervention among clients admitted to a coronary care unit with severe angina or a first time myocardial infarction.
- ? The intervention involved in-depth nursing assessment interviews related to client beliefs, motivation and experiences of smoking, culminating in an individualized cessation plan. Participants were offered follow up support during the first year post-intervention.
- ? The findings are highly encouraging with a 77% smoking cessation rate for surviving clients within the intervention group at the end of the first year, and with 75% continued successful smoking cessation amongst surviving clients 2 years post-intervention.
106.
E. D. Srivastava M. A. H. Russell C. Feyerabend J. G. Masterson J. Rhodes 《Psychopharmacology》1991,105(1):63-68
We studied the responses of smokers and life-long non-smokers to transdermal nicotine patches over 24 h in three groups of
subjects: non-smokers on a 15 mg patch (n=8), non-smokers on a 30 mg patch (n=8) and smokers on a 30 mg patch (n=8). Unexpectedly, the non-smokers appeared to absorb nicotine more rapidly. The increase in blood nicotine concentrations
of non-smokers over the first 2 h of patch use was double that of the smokers, with mean increases of 4.5 (SD=3.7), 10.9 (SD=4.2)
and 4.1 (SD=2.7) ng/ml in the three groups, respectively (P<0.005). The smokers had no pleasant or unpleasant effects from the 30 mg patch (
Cmax 13.9 ng/ml, SD=4.9; Tmax 8.75 h) but all eight non-smokers experienced mild nausea and lightheadedness (P<0.01) within the first hour, and seven dropped out (P<0.01) at 3–8 h due mainly to severe nausea, vomiting or headache (
Cmax 18.4 ng/ml, SD=4.9; Tmax 5.25 h). Only one non-smoker dropped out on the 15 mg patch, but five had transient nausea in the first hour (
Cmax 7.9 ng/ml, SD=3.0; Tmax 8.0). Our study provides evidence of chronic pharmacodynamic nicotine tolerance in smokers, but does not address whether
this is acquired or innate. The higher rate of transdermal nicotine absorption in non-smokers is unexplained and requires
replication. 相似文献
107.
The reasons why older people smoke have not been examined in the literature. This paper attempted to examine the differences in motivation and maintenance factors of elderly and young smokers using the Horn-Waingrow Why do you smoke questionnaire. One hundred and thirteen clinical patients and 112 non-patient controls were used in this study. The clinical group was divided into an elderly group (n = 58) and a younger group (n = 55). The results of a discriminant analysis showed that patients significantly differed from non-patients on 'automatic habit and stimulation', and 'crutch/tension reduction' factors. Elderly patients were found to be significantly differentiated from both younger patients and the control group on the 'pleasurable relaxation' factor. These findings offer support for the US Surgeon Generals' report that elderly smokers do have different motivating factors for their smoking behaviours from younger smokers. 相似文献
108.
Diego Serraino Silvia Franceschi Renato Talamini Sergio Frustaci Carlo La Vecchia 《Cancer causes & control : CCC》1991,2(3):157-164
The role of socioeconomic and anthropometric indicators, tobacco, alcohol consumption, dietary habits, and medical history in the etiology of soft-tissue sarcoma (STS) was examined in a hospital-based case-control study, conducted in the Friuli-Venezia Giulia region of northeast Italy, between 1985 and 1990. A total of 88 STS cases (53 males and 35 females; median age: 52 years) and of 610 controls (306 males and 304 females; median age: 54 years) were interviewed. There were significant excess risks associated with a history of herpes zoster infection (odds ratio [OR]=2.4,95 percent confidence interval [CI]=1.1–5.3), chicken pox (OR=2.2, CI=1.2–4.3) and mumps in childhood (OR=2.0, CI=1.1–3.9). History of diabetes was also linked to a nonsignificant increase in STS risk (OR=1.8, CI=0.6–5.4), whereas exposure to radiation for diagnostic or therapeutic purposes was not related to the probability of developing STS. None of the investigated socioeconomic and anthropometric indicators seemed to affect STS risk; neither did tobacco smoking, nor consumption of alcohol, coffee, and tea beverages. Conversely, among the dietary habits investigated, a significant positive association emerged with an increasing frequency of consumption of dairy products (% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiiYdd9qrFfea0dXdf9vqai-hEir8Ve% ea0de9qq-hbrpepeea0db9q8as0-LqLs-Jirpepeea0-as0Fb9pgea% 0lrP0xe9Fve9Fve9qapdbaqaaeGacaGaaiaabeqaamaabaabcaGcba% Gaae4XdmaaCaaaleqabaGaaGOmaaaaaaa!3DA2!\[{\rm{\chi }}^2\]for trend=6.8, P<0.01) and oil (% MathType!MTEF!2!1!+-% feaafeart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXafv3ySLgzGmvETj2BSbqefm0B1jxALjhiov2D% aebbfv3ySLgzGueE0jxyaibaiiYdd9qrFfea0dXdf9vqai-hEir8Ve% ea0de9qq-hbrpepeea0db9q8as0-LqLs-Jirpepeea0-as0Fb9pgea% 0lrP0xe9Fve9Fve9qapdbaqaaeGacaGaaiaabeqaamaabaabcaGcba% Gaae4XdmaaCaaaleqabaGaaGOmaaaaaaa!3DA2!\[{\rm{\chi }}^2\]for trend=4.3, P<0.05), while a negative association was seen for intake of whole grain bread and pasta (OR for highest cf lowest tertile=0.4, CI=0.2–0.9).Support for this project was contributed by the Italian Association for Cancer Research, Milan, and the Italian National Research Council (CNR Applied Project Oncology, Contract 87.01544.44). 相似文献
109.
P. Brunel X. Girerd S. Laurent B. Pannier M. Safar 《European journal of clinical pharmacology》1992,42(2):143-146
Summary The aim of the present study was to examine the effect of cigarette smoking in healthy non-smokers on blood pressure and forearm haemodynamics after acute oral administration of non-selective -adrenoceptor blockers with and without intrinsic sympathomimetic activity, viz. pindolol 15 mg and propranolol 80 mg. A preliminary study was done to compare cigarette smoking and sham smoking to evaluate the time-course of the haemodynamic effects of cigarette smoking. The second experiment was then carried out in the same six volunteers, according to a double-blind randomized placebo-controlled crossover design, to evaluate the possible effect of pre-treatment with -adrenoceptor blockers on blood pressure, heart rate and forearm haemodynamics (forearm blood flow, brachial artery diameter and brachio-radial pulse-wave velocity) measured at baseline, during smoking and every five minutes up to 1 h afterwards.No major difference from placebo in blood pressure or forearm haemodynamics was found and pre-treatment with beta-blockers did not prevent the acute vascular effects of cigarette smoking. 相似文献
110.
Summary Changes in catecholamine, c-AMP and lactate concentrations in the coronary circulation of man, during smoking, were studied in 12 patients. The heart rate increased from 63±2 beats/min (control) to 74±3 (smoking) (P<0.01), falling to 70±2 (10 min after smoking) (0.05>P>0.01), whilst coronary sinus c-AMP concentrations rose from 11±0.7 nmol/l (smoking) to 11.9±0.8 nmol/l (after smoing) (0.05>P>0.01; one tailed t test). There was no significant change in blood pressure, catecholamine or lactate concentrations. The study was repeated in eight of the patients following intravenous oxprenolol. Coronary sinus catecholamine concentrations increased from 4.1±0.7 nmol/l (control) to 5.5±1.1 nmol/l (after smoking) (0.05>P>0.01; one tailed t test), but heart rate and c-AMP concentrations remained unchanged, confirming that smoking-induced tachycardia is a result of a -adrenergic mechanism, at least part of which is due to a release of cardiac catecholamines. Arterial lactate concentrations increased only following oxprenolol from 0.74±0.07 mmol/l (control) to 0.83±0.09 mmol/l (smoking). 相似文献