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   23338篇
  免费   1838篇
  国内免费   559篇
耳鼻咽喉   145篇
儿科学   774篇
妇产科学   202篇
基础医学   1965篇
口腔科学   551篇
临床医学   2066篇
内科学   2311篇
皮肤病学   313篇
神经病学   2421篇
特种医学   629篇
外国民族医学   7篇
外科学   1240篇
综合类   2658篇
现状与发展   3篇
一般理论   3篇
预防医学   2720篇
眼科学   346篇
药学   4434篇
  20篇
中国医学   1495篇
肿瘤学   1432篇
  2024年   69篇
  2023年   353篇
  2022年   567篇
  2021年   761篇
  2020年   829篇
  2019年   750篇
  2018年   728篇
  2017年   868篇
  2016年   892篇
  2015年   807篇
  2014年   1478篇
  2013年   2055篇
  2012年   1232篇
  2011年   1281篇
  2010年   931篇
  2009年   1012篇
  2008年   1007篇
  2007年   1009篇
  2006年   889篇
  2005年   834篇
  2004年   688篇
  2003年   683篇
  2002年   549篇
  2001年   440篇
  2000年   380篇
  1999年   292篇
  1998年   306篇
  1997年   296篇
  1996年   255篇
  1995年   245篇
  1994年   227篇
  1993年   205篇
  1992年   243篇
  1991年   217篇
  1990年   205篇
  1989年   196篇
  1988年   193篇
  1987年   194篇
  1986年   172篇
  1985年   197篇
  1984年   212篇
  1983年   118篇
  1982年   166篇
  1981年   124篇
  1980年   117篇
  1979年   110篇
  1978年   73篇
  1977年   77篇
  1976年   62篇
  1975年   39篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The Italian mental health reform nine years on   总被引:2,自引:0,他引:2  
It is 9 years since the mental health reform was passed by the Italian Parliament. The author presents a data-based evaluation of the effects of the Italian mental health reform. There are still many problems to be resolved: More than 30,000 inpatients are still in psychiatric hospitals and little is known of the fate of those discharged in recent years. District mental health services are still lacking, especially in the south of the country; Psychiatric units in the general hospital function much the same way as the "old" psychiatric hospitals. The pattern of mental health services consumers have changed: They are younger with less severe psychiatric diagnosis and come from a higher social background.  相似文献   
92.
Summary A behavioural test involving potentiation of the effects of an acute injection of -phenylethylamine (10 mg kg–1 i.p.) was used to assess the time-course of type-B MAO inhibition after administration of (–)deprenyl (5 mg kg–1 i.p.) and of MD 240928 (20 mg kg–1 i.p.) respectively. Potentiation of the effects of -phenylethylamine was observed 1 h after injection of (–)deprenyl or MD 240928. This effect was still evident 120 h after administration of (–)deprenyl but not 24 h after administration of MD 240928. Comparisons of ex vivo estimates of MAO activity yielded a corresponding time-course for the recovery of this enzyme. The extent of MAO inhibition required for potentiation of the effects of -phenylethylamine was inferred from a comparison of the behavioural test results and the ex vivo MAO activity observed after (–)deprenyl administration. These comparisons indicate a significant underestimation of MD 240928-induced MAO inhibition using ex vivo measures. This underestimation is interpreted as evidence fordilution effects in the ex vivo assay of MAO inhibition. The potentiation of effects of -phenylethylamine under the present conditions is proposed as a useful and simple test for effects of reversible type-B MAO inhibitors.  相似文献   
93.
Summary The phorbol ester 12-O-tetradecanoyl phorbol-13-acetate (TPA) was used to examine the hypothesis that phosphoinositide turnover is involved in the regulation of myocardial contractility mediated by stimulation of alpha-adrenoceptors in the mammalian cardiac muscle. Exposure of the isolated rabbit papillary muscle electrically driven at a rate of 1 Hz at a temperature of 37°C to TPA in concentrations of 10–1000 nmol/l for 30 min did not affect the basal force of contraction. The concentration-response curve for the positive inotropic effect of (–)-phenylephrine mediated by stimulation of alpha-adrenoceptors in the presence of (±)-bupranolol (100 nmol/1) was shifted to the right and downward by TPA in concentrations of 30–1000 nmol/l, while the effect of (–)-phenylephrine mediated by stimulation of beta-adrenoceptors in the presence of prazosin (100 nmol/l) was not decreased, but slightly enhanced by exposure of the muscle to relatively low concentrations of TPA (10–100 nmol/l). Incubation of the membrane fraction isolated from the rabbit ventricular muscle with TPA in vitro under the same condition as employed in the physiological experiments decreased the specific binding of [3H]prazosin but not that of [3H]CGP-12177, while the non-tumor promoting phorbol ester, PDD, was ineffective. These results indicate that activation of protein kinase C by TPA does not mimic the positive inotropic effect of catecholamines mediated by activation of myocardial alpha-adrenoceptors. on the other hand, the specific interaction of alpha-adrenoceptor-mediated processes with TPA in the rabbit papillary muscle is in line with the view that the facilitation of phosphoinositide turnover and subsequent activation of protein kinase C may play a certain role in the coupling of alpha-adrenoceptor occupation by agonists to the process leading to the positive inotropic action. Send offprint requests to M. Endoh  相似文献   
94.
目的:探究Her2阴性晚期胃癌患者采用阿帕替尼进行治疗的疗效及毒副作用。方法:按照不同治疗方法将本院就诊的Her2阴性晚期胃癌患者分为阿帕替尼组(AP组)和替吉奥组(TI组),各46例,分析比较两组患者的临床疗效、生活质量、毒副作用及远期疗效。结果:治疗后,AP组11例、TI组6例患者出现部分缓解,AP组患者RR、DCR数值明显比TI组高(P<0.05);AP组患者生活质量明显优于TI组(P<0.05)。AP组和TI组患者均出现血小板减少、蛋白尿、肝功能异常等不良反应,但未出现Ⅳ级毒副作用,其中AP组患者高血压、血小板减少的发病率分别为63.52%、76.73%,TI组患者发病率分别为62.45%、78.11%, AP组出现毒副作用的患者人数与TI组比较无明显差异(P>0.05)。随访3年结果显示,AP组患者3年生存率为10.86%,TI组患者为0,AP组患者总生存率明显高于TI组(P<0.05)。结论:阿帕替尼对Her2阴性晚期胃癌患者的临床疗效及远期治疗效果较佳,虽然治疗后也会出现一定的毒副作用,但与替吉奥治疗后出现的毒副作用相近,且患者身体承受程度较佳。阿...  相似文献   
95.
The purpose of this study was to describe the role played by the ability to estimate caries depth in successfully deciding to treat dentin caries when making use of bitewing radiographs as a diagnostic test. A 10% random sample (n = 444) of Dutch dental practitioners was sent a two-wave questionnaire concerning radiographic caries diagnosis and restorative treatment decision making. The second wave consisted of simulated bitewing radiographs of 105 tooth surfaces with and without dentin caries according to two measuring standards: (a) a micro-radiographic "gold" standard and (b) a norm of expert observers. The dentists were asked to diagnose caries at 4 depths of penetration using a 5-point certainty scoring system to measure diagnostic ability; and to make a treatment decision for each surface. The overall response was 61% (273). A regression analysis was carried out using the chance per dentist of correctly deciding to treat dentin caries as the dependent variable. The degree of agreement with the experts' diagnosis of radiographic caries depth was used to create variables measuring diagnostic ability. Five significant (P less than 0.05) variables explained 60% (R2 = 0.60) of the variation in decision making. The best diagnostic ability variable explained 47% of the variation while the treatment criterion reportedly used explained 3%. We conclude that the ability of practitioners to interpret radiographs plays a major role in treatment decision making and that their reported treatment decision making criteria should not be taken at face value.  相似文献   
96.
Summary The present experiments were carried out to investigate the cardiovascular effects of endothelin 1 (ET) in pithed spontaneously hypertensive (SH) rats and to evaluate its mechanism of action. The results show that ET (0.1 – 3 nmol/kg i.v.) is a powerful vasoconstrictor agent in the pithed rat. However, at a dose of 3 nmol/kg i.v. all the pithed animals died following a gradual decrease in mean arterial blood pressure and pulse pressure and changes in the form of the electrocardiogram (ECG). The predominant feature of the change in the ECG was a progressive decrease in the amplitude of the T wave resulting in a depression of the curve representing repolarization. Investigations in isolated perfused SH rat hearts showed that ET powerfully reduces coronary flow concentration-dependently (IC50 2.1 ±0.3 nM) an effect associated with sinus bradycardia and a decrease in coronary pressure amplitude. No overt ECG changes were seen. Control experiments with mechanical flow restriction suggest that bradycardia is a consequence of reduced coronary flow and that the ECG changes observed in vivo can be explained on the basis of coronary insufficiency and resulting myocardial hypoxia. Vasoconstrictor responses to angiotensin II (0.4 g/kg i.v.), phenylephrine (8 g/kg i.v.) and ET (0.5 nmol/kg i.v.) were antagonised by around 70% by isradipine (0.03 mg/kg i.a.). The results suggest that endothelin-induced vasoconstriction may involve receptor operated channel activation and opening of voltage sensitive Ca2+ channels.Send offprint requests to A. K. Mir at the above address  相似文献   
97.
Summary The clinical tolerance and pharmacokinetics of FCE 22101 (sodium (5R, 6S)-6-[(1R)-hydroxyethyl]-2-carbamoyloxymethyl-2-penem-3-carboxylate), a new penem antibiotic, have been studied after giving a single i.v. dose of 4 mg·kg–1 to ten healthy male volunteers. The pharmacokinetics was estimated according to a two-compartment open model. The peak plasma concentration (Cmax) was 15.5 (1.08) µg·ml–1, mean (SEM). FCE 22101 was rapidly cleared from the systemic circulation [ =44.2 (4.2) min; CL=7.21 (0.47) ml·kg–1·min–1]. The mean apparent volume of distribution at steady-state was 246 (16.9) ml·kg–1. The mean residence time relative to the 10 min infusion was 39.4 (1.5)min. Urinary recovery of FCE 22101 showed wide inter-subject variation, ranging from 10.2 to 53.6% of the dose. No subject complained of adverse effects.  相似文献   
98.
The influence of the pre- and postweaning maternal environment on the offspring's phenotype was examined in 5-HT1A and 5-HT1B receptor knockout mice (KO1A and KO1B, respectively). We have previously shown that, when born to and raised by homozygous dams of the same genotype, adult KO1A are more anxious than wild-type (WT) mice, and adult KO1B are hyperactive and slightly less anxious than WT mice. We extend our studies here to the behavioral results of the offspring's own genotype, when the dam's genotype is constant, and the effects of the dam's genotype when the offspring's genotype is constant. In Experiments 1 and 2, KO1A-/- pups produced less ultrasonic vocalizations (USV) than controls in an isolation test on postnatal Day 7 when born to and reared by KO1A dams, either -/- or +/-. Heterozygous F1 pups reared by KO1A-/- dams produced more USV and were less anxious in the plus-maze at 2 to 3 months of age than F1 pups born to and reared by WT dams (Experiment 3). F1 pups reared by KO1B-/- dams produced less USV and were more anxious in the plus-maze than F1 pups reared by WT dams (Experiment 4). The results support a role for maternal effects that may comprise direct effects such as the dam's behavior and nutritional care of the pup, and possibly more complex indirect effects through the establishment of idiosyncratic dam-pup dyadic interactions. We recommend that breeding techniques that rely on same genotype (mutant-mutant or WT-WT) breeding pairs not be used to generate offspring when the focus of research is the study of gene function, but rather when familial effects need to be studied.  相似文献   
99.
There is no method available to compare the fit of two non-hierarchical non-linear mixed effects models, although the common practice is to select the model with the lower objective function. Bootstrapping the log-likelihood differences (LLDs) of non-hierarchical models and constructing a bootstrap confidence interval on the LLDs is proposed for comparing the goodness-of-fit of such models. This is illustrated with different parameterizations of clearance models for an anti-infective agent in a longitudinal pharmacokinetic study which are compared. Additive and exponential models of creatinine clearance as a predictor of clearance are used as examples.  相似文献   
100.
It has been reported that sodiumnitroprusside (SNP) decreases mean systemic pressure and simultaneously increases pressure pulse amplification towards the iliac periphery (Kenner and van Zwieten 1982). This unexpected finding was suggested to be due to a decrease in iliac peripheral resistance but an increase in iliac differential resistance. In order to investigate this apparent contradiction, the iliac periphery was hemodynamically isolated from the rest of the circulation and perfused with the dog's own blood by means of a pump. Perfusion pressure (P) and flow (F), femoral venous pressure (Pv), systemic pressure (Ps) and cardiac output (CO) were measured. Steady state pressure-flow relations of the isolated bed were obtained during control and during various i.v. infusion rates of SNP and adenosine (ADS) and were found to be straight (meanr=0.99). Their slope (P/F) was defined as differential resistance (Rd). Peripheral resistance (Rp) of the iliac bed was defined as Rp=(P-Pv)/F, calculated at the flow value where perfusion pressure equalled the prevailing systemic pressure. Total peripheral resistance (TPR) was defined as TPR=Ps/CO. The changes of Rd, Rp, Ps, CO and TPR with respect to control show that during low SNP infusion rates Rd and Rp were both increased while TPR was decreased. During all infusion rates of SNP CO did not change while Ps decreased. During low infusion rates of adenosine CO increased while Ps, Rd and Rp did not change and TPR decreased. During high infusion rates of ADS CO decreased again, Rd, Rp and Ps decreased, and TPR remained constant but at a decreased level.It is concluded that: (1) the suggestion of Kenner and van Zwieten is not supported, since SNP (as well as ADS) affects iliac peripheral and iliac differential resistance in a similar way; (2) SNP (as well as ADS) affects iliac peripheral resistance and total peripheral resistance in a differentiated way, and even in an opposite way during low infusion rates of SNP; (3) it is this opposite effect that explains the paradoxical observations of Kenner and van Zwieten; (4) for comparable reductions of TPR, CO is better maintained during infusion of SNP, while Ps is better maintained during infusion of ADS.  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