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   762篇
  免费   14篇
  国内免费   4篇
耳鼻咽喉   22篇
儿科学   3篇
妇产科学   6篇
基础医学   131篇
口腔科学   1篇
临床医学   32篇
内科学   63篇
皮肤病学   7篇
神经病学   89篇
特种医学   10篇
外科学   20篇
综合类   44篇
预防医学   139篇
眼科学   38篇
药学   157篇
中国医学   11篇
肿瘤学   7篇
  2023年   13篇
  2022年   17篇
  2021年   17篇
  2020年   20篇
  2019年   24篇
  2018年   10篇
  2017年   14篇
  2016年   10篇
  2015年   8篇
  2014年   29篇
  2013年   54篇
  2012年   32篇
  2011年   44篇
  2010年   26篇
  2009年   30篇
  2008年   40篇
  2007年   33篇
  2006年   21篇
  2005年   22篇
  2004年   12篇
  2003年   17篇
  2002年   11篇
  2001年   8篇
  2000年   8篇
  1999年   14篇
  1998年   5篇
  1997年   11篇
  1996年   6篇
  1993年   7篇
  1992年   6篇
  1990年   5篇
  1988年   6篇
  1987年   5篇
  1986年   5篇
  1985年   11篇
  1984年   16篇
  1983年   6篇
  1982年   8篇
  1981年   9篇
  1980年   8篇
  1979年   10篇
  1978年   11篇
  1977年   11篇
  1976年   11篇
  1975年   10篇
  1974年   22篇
  1973年   11篇
  1972年   9篇
  1971年   8篇
  1969年   10篇
排序方式: 共有780条查询结果,搜索用时 15 毫秒
1.
石杉碱甲和乙促进小鼠的空间辨别学习和记忆   总被引:1,自引:0,他引:1  
朱晓东  唐希灿 《药学学报》1987,22(11):812-817
石杉碱甲和乙是从石杉科石杉属植物蛇足石杉[Huperzia scrrata(Thunb.)Trev.]中分得的二个新生物碱。“Y”迷宫实验表明,ip Hup-A 0.075~0.125 mg/kg或Hup-B 0.4~0.8mg/kg,均能明显促进小鼠的空间辨别学习,并能显著预防CO2产生的短时识别障碍,促进记忆保持和记忆再现。ig Hup-A 0.1~0.3 mg/kg或Hup-B 0.8 mg/kg也有促进学习的作用。促进作用Hup-A>Phys>Hup-B。剂量与效应曲线呈倒U型。  相似文献   
2.
目的:编制一套适用于四-六年级学生的学习能力倾向测验,并对条目的质量和测验的信度进行检验。方法:采用理论和工作分析相结合的方法构建测验,并将测验分为A卷和B卷两个大致平行的题本;以难度、区分度检验条目质量,以重测信度、内部一致性信度、平行信度检验测验的稳定性。结果:①各分测验平均难度指数介于0.42加.51之间;鉴别指数在0.2以上的条目所占比例为92.04%(A卷)或95.45%(B卷);②各分测验的重测相关为0.67加.78(A卷)或0.65~0.80(8卷):各分量表重测相关为0.67~0.82(A卷)或0.65-0.82(B卷);总量表重测相关为0.86(A卷)或0.87(B卷);③各分测验的Cronbach's α系数为0.62-0.76(A卷)或0.61加.85(B卷);两卷的语文、数理分量表Cronbach’s α系数均在0.8以上,总量表Cronbach's α系数则在0.9左右;④A卷与B卷各分测验相关系数在0.42-0.70之间,分量表相关系数在0.54~0.72之间,总量表相关系数为0.77。结论:大部分条目的难度和区分度符合要求,各信度指数为良好或可以接受;两个题本尚未达到平行的要求。  相似文献   
3.
 The suppression of food intake observed following naloxone administration has often been ascribed to palatability or taste. Unfortunately, many confounds become apparent when attempts are made to isolate such factors in the investigation of ingestive behaviors. In the present study, rats (two groups) were trained to discriminate either a 10% or 5% sucrose solution from water (0.1 ml). These mildly food deprived subjects (95% of free-feeding weight) were trained to press the appropriate lever in a two-lever operant chamber following sampling of sucrose or water; successful responding was reinforced by delivery of a 45 mg grain food pellet. Following random exposure to reduced sucrose concentrations tested under extinction, a sucrose concentration gradient (1.0, 0.5, 0.1, 0.05, 0.01 and 0.005% sucrose solution) was established for both training groups under IP saline administration. Data collected under IP saline were then compared to those collected following random IP naloxone administration (3.0, 1.0, 0.3 and 0.1 mg/kg). No significant differences were observed between the sucrose concentration gradients obtained under saline and those obtained under naloxone, suggesting that the anorectic effect of naloxone is not primarily determined by discrimination of sweet taste. Received: 4 September 1996 / Final version: 16 October 1996  相似文献   
4.
A series of experiments examined the effects of lesions of the dorsal noradrenergic bundle (DNAB), induced by 6-hydroxydopamine (6-OHDA), on the behavioural response to systemic and intra-accumbens amphetamine, using a rat analogue of Leonard's 5-choice serial reaction time task for humans. Although the 6-OHDA DNAB lesion produced a profound depletion of cortical noradrenaline (NA) (to around 5% of control levels) it did not impair any aspect of performance on this task. Both systemic and intra-accumbens amphetamine increased behavioural measures of impulsivity of responding, but neither impaired discriminative accuracy in the sham-operated control rats. However, the DNAB lesioned rats did show a discriminative impairment following both low doses of systemic amphetamine, and intra-accumbens amphetamine. The latter effect was antagonised by systemic administration of the specific dopaminergic (DA) antagonist alpha-flupenthixol. The DNAB lesion did not alter the effect of amphetamine on any other behavioural measure, including speed and impulsivity of responding. These results suggest that although DA and NA participate in qualitatively different behavioural processes, the effects of DNAB lesions on attentional processes depend on the level of DA activity within the nucleus accumbens.  相似文献   
5.
侧脑室注射东莨菪碱和酚妥拉明对幼兔分辨学习的影响   总被引:3,自引:1,他引:2  
目的 探讨东莨菪碱和酚妥拉明对幼兔分辨学习的影响。方法 将30只比利时纯种幼兔从生后13日龄随机分为三组:东莨菪碱组、酚妥拉明组和生理盐水对照组,观察不同日龄各组幼兔的分辨学习能力。结果 幼兔分辨学习的正确反应一般始于生后15日龄。侧脑室注射东莨菪碱对16日龄以前幼兔分辨学习无明显影响,对17日龄以后幼兔分辨学习产生明显抑制作用。侧脑室注射酚妥拉明对13—23日龄幼兔分辨学习均有明显抑制作用。结论 幼兔生后发育过程中学习能力的发展具明显的阶段性,其原因可能与神经递质系统的发育成熟有关。  相似文献   
6.
【摘要】
目的 调查与静止性脑梗死(silent brain infarction,SBI)相关的独立影响因素,构建SBI风险预测量
表并验证。
方法 在单中心横断面研究中,前瞻性连续纳入无神经系统疾病既往史的体检者,收集其人口学
信息,高血压、糖尿病等血管危险因素,血脂、糖化血红蛋白、血浆同型半胱氨酸等化验结果录入数
据库。采用标准影像学操作规范进行头颅MRI扫描,并由影像学医师盲法判读,将受试者分为SBI组
和无SBI组。将所有受试者按照3∶1比例随机分为训练集和验证集,在训练集中采用单因素和多因素
Logistic回归分析SBI的独立影响因素,构建SBI预测量表。在训练集和验证集中应用ROC曲线检验量表
的区分度,应用Hosmer-Lemeshow分析检验量表的校准度。
结果 共有633例研究对象纳入研究,平均年龄52.0±10.5岁,女性272例(43.0%)。训练集(475
例)和验证集(158例)两个样本集合的基线特征均衡。校正混杂因素后多因素分析显示,年龄≥45
岁(OR 8.37,95%CI 1.12~62.80,P =0.039),高血压(OR 2.30,95%CI 1.08~4.90,P =0.032),同型半
胱氨酸(Q2~Q3:OR 6.89,95%CI 0.89~53.10,P =0.064;Q4:OR 13.6,95%CI 1.74~105.87,P =0.013)
与SBI风险独立相关。根据OR 值构建SBI危险评分(SBI risk score,SBI-RS)量表,量表赋值为:年龄
≥45岁赋值8分;有高血压赋值2分;同型半胱氨酸根据四分位分层分别赋值为0分、7分和14分。SBIRS
在训练集和验证集中ROC曲线显示曲线下面积分别为0.77(95%CI 0.69~0.84,P<0.001)和0.76
(95%CI 0.63~0.88,P<0.001),区分度良好。Hosmer-Lemeshow相关分析提示SBI-RS具有较好的校准度
(P>0.05)。
结论 在健康体检人群中,SBI -RS具有较好的区分度和校准度,可以帮助识别SBI高危人群。  相似文献   
7.
Nicotine’s discriminative stimulus effects may be critical to understanding reinforcement of tobacco smoking. It is not known whether regular nicotine exposure produces tolerance or sensitivity to these effects. In this study, male and female smokers (n = 11) and never-smokers (n = 10) were trained to discriminate 20 μg/kg nicotine by nasal spray from placebo (0) on day 1. On day 2, both groups were tested on generalization of this discrimination across intermittent presentations of 0, 3, 6, 12, and 20 μg/kg nicotine in random order. Quantitative and quantal behavioral discrimination tasks, used in previous research, were employed. On day 3, subjects were instructed to self-administer sprays from the 20 μg/kg nicotine versus 0 bottles in a concurrent-choice procedure. All but one subject (female smoker) learned reliably to discriminate 20 μg/kg nicotine from placebo (≥ 80% correct) on day 1. Nicotine-appropriate responding on day 2 was attenuated in smokers versus never-smokers at 20 μg/kg on the quantitative task and at 12 μg/kg on the quantal task, suggesting tolerance. There was no difference in responding at other doses. Smokers also showed attenuated responses on the subjective measure of “head rush”, which was associated with discrimination responding in both groups. Nicotine self-administration was significantly greater in smokers versus never-smokers, who self-administered nicotine below chance levels, and was inversely related to discrimination behavior in never-smokers but unrelated in smokers. Women smokers showed less change in nicotine-appropriate responding across generalization doses, reported less confidence in discriminating training doses during acquisition on day 1, and tended to self-administer less nicotine on day 3. These results indicate that smokers may become tolerant to the discriminative stimulus effects of nicotine, perhaps promoting increased use. Received: 1 October 1996/Final version: 28 January 1997  相似文献   
8.
The role of the ethanol training dose on the ability of the selective 5-HT1 agonist TFMPP (m-trifluoromethylphenylpiperazine) to produce ethanol-like discriminative stimulus effects was evaluated in three groups of rats trained to discriminate 1.0 g/kg (n=5), 1.5 g/kg (n=6) or 2.0 g/kg (n=7) ethanol (IG) from water using a two-lever procedure with food reinforcement available under a fixed ratio 20 (FR 20) schedule. Ethanol generalization gradients were comparable in the three groups, indicating few potency differences in the ethanol stimulus across training dose. However, the ability of TFMPP (0.1–1.7 mg/kg; IP) to substitute for ethanol was dependent on the training dose. TFMPP resulted in partial substitution in the 1.0 g/kg group, complete substitution for 1.5 g/kg group and no substitution in the 2.0 g/kg ethanol training group. The results indicate a serotonergic component to the discriminative stimulus effects of an intermediate dose of ethanol that is not prominent as the dose of ethanol is raised. These data add further support for the hypothesis that ethanol produces a mixed discriminative cue, the components of which are not uniformly amplified when the dose of ethanol is increased.  相似文献   
9.
Twenty male Sprague-Dawley rats were trained to discriminate pentylenetetrazole (PTZ, 15 mg/kg, intraperitoneally) from saline (SAL) under a drug discrimination procedure. Test sessions were conducted with 10 randomly selected subjects. Tests with various doses of PTZ resulted in a dose-dependent increase in the percentage of total session responses emitted on the PTZ-appropriate lever without a significant change in response rates across a wide range of test PTZ doses. Rats did not generalize the PTZ stimulus to ethanol (ETOH) up to ETOH test doses that completely suppressed responding. High acute ETOH doses (2, 3, and 4 g/kg) administered at various time points prior to discrimination test sessions engendered responding on the PTZ-appropriate level in a quantitative fashion, that was dose- and time-dependent. This acute ETOH delayed effect from these high doses replicates our previously published study using a Drug 1-Drug 2 discrimination task with Chlordiazepoxide and PTZ. More importantly, we suggest that the present behavioral assay may be a sensitive animal analogue of human "hangover" phenomena.  相似文献   
10.
中学生学业能力倾向测验的初步编制   总被引:2,自引:1,他引:2  
目的:编制一个适用于中学生的学业能力倾向测验。方法:采用理论与工作分析相结合的编制策略而成的中学生学业能力倾向测验包括A、B两个复本,均由三个分量表含七个分测验组成,分别测量语文.数理及图形等能力。研究样本由河北省石家庄市1424名中学生组成,并对其中468人分别进行信效度检验。结果:①各分测验原始分基本随年级升高而增长;②各分测验难度在0.46~0.54。鉴别指数在0.38~0.52;③各分量表及总分的重测相关系数在0.68~0.92,α系数在0.64~0.89.G系数在0.64~0.92;④探索性因素分析表明各分测验对基本能力因子均有中度以上的负荷,抽取的三个因子解释了总方差的72.18%(A式)和73.53%(B式);⑤测验分数与长一鞍团体智力测验、与教师评价均呈显著正相关。测验分数在不同年级之间存在显著差异。学习成绩的回归分析可见,测验分数与考试成绩显著正相关,语文及数理分量表进入考试总成绩的回归方程。结论:中学生学业能力倾向测验的条目质量及信效度符合心理测量学的基本要求。  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