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   9378篇
  免费   591篇
  国内免费   173篇
耳鼻咽喉   43篇
儿科学   202篇
妇产科学   247篇
基础医学   1737篇
口腔科学   165篇
临床医学   400篇
内科学   1751篇
皮肤病学   89篇
神经病学   1553篇
特种医学   199篇
外科学   455篇
综合类   721篇
现状与发展   2篇
预防医学   1507篇
眼科学   119篇
药学   757篇
  2篇
中国医学   121篇
肿瘤学   72篇
  2024年   10篇
  2023年   118篇
  2022年   340篇
  2021年   486篇
  2020年   339篇
  2019年   233篇
  2018年   251篇
  2017年   224篇
  2016年   254篇
  2015年   302篇
  2014年   441篇
  2013年   571篇
  2012年   462篇
  2011年   479篇
  2010年   385篇
  2009年   421篇
  2008年   409篇
  2007年   421篇
  2006年   343篇
  2005年   322篇
  2004年   357篇
  2003年   315篇
  2002年   274篇
  2001年   192篇
  2000年   156篇
  1999年   148篇
  1998年   157篇
  1997年   159篇
  1996年   146篇
  1995年   119篇
  1994年   103篇
  1993年   127篇
  1992年   103篇
  1991年   94篇
  1990年   103篇
  1989年   73篇
  1988年   78篇
  1987年   65篇
  1986年   76篇
  1985年   68篇
  1984年   64篇
  1983年   42篇
  1982年   62篇
  1981年   43篇
  1980年   42篇
  1979年   29篇
  1978年   32篇
  1977年   30篇
  1976年   28篇
  1973年   12篇
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
91.
Modern Mind-Brain Reading: Psychophysiology, Physiology, and Cognition   总被引:17,自引:0,他引:17  
This paper reviews the actual and potential benefits of a marriage between cognitive psychology and psychophysiology. Psychophysiological measures, particularly those of the event-related brain potential, can be used as markers for psychological events and physiological events. Thus, they can serve as "windows" on the mind and as "windows" on the brain. These ideas are illustrated in the context of a series of studies utilizing the lateralized readiness potential, a measure of electrical brain activity that is related to preparation for movement. This measure has been used to illuminate presetting processes that prepare the motor system for action, to demonstrate the presence of the transmission of partial information in the cognitive system, and to identify processes responsible for the inhibition of responses. The lateralized readiness potential appears to reflect activity in motor areas of cortex. Thus, this measure, along with other psychophysiological measures, can be used to understand how the functions of the mind are implemented in the brain.  相似文献   
92.
Miniature end-plate currents (m.e.p.c.s) were recorded from frog neuromuscular junctions using a two-electrode voltage clamp. The m.e.p.c. frequency was temporarily elevated following 10 s iontophoretic applications of acetylcholine (ACh) when the junctions were clamped at 100 mV. This post-ACh burst of quanta was also observed at unclamped junctions. At –100 mV, the intensity of the burst was proportional to the amount of current flowing across the end-plate during ACh iontophoresis, but usually did not reach its peak until the end-plate receptor channels were almost completely closed. Addition of 0.5 M TTX to the Ringer's solution, or total replacement of sodium with quanidine, lithium, or methylamine did not inhibit the burst. No burst was observed in Ca2+-free, EGTA solutions, or in Ca2+-free solutions containing 2 mM Mn2+. Sr2+ effectively substituted for Ca2+. Addition of 2 mM Co2+ or Mn2+ to normal Ringer's did not inhibit the burst. Presynaptic muscarinic receptors did not obviously contribute to the burst, since it was not blocked by atropine, nor produced by oxotremorine or pilocarpine. The ACh analogs carbachol and acetyl--methylcholine also produced the burst. The burst was highly dependent on the muscle membrane potential during the period of ACh iontophoresis, becoming more intense at potentials negative to –100 mV and disappearing at –60 mV. The critical importance of the post-synaptic membrane potential suggests that the burst may be due to an action of the muscle end-plate on the motor nerve terminal, possibly by the movement of an anionic substance through open end-plate receptor channels, but this hypothesis does not account for the delay of the burst until near the end of the ACh-induced end-plate current.  相似文献   
93.
With the investigations on pregnant women and newbornsinfected withToxoplasma, rubella virus, cytomegalovirus,herpes simplex virus (TORCH), it was found that humanparvovirus B19 (B19 virus), which belongs to the familyParvoviridae and the genus Erythrovir…  相似文献   
94.
目的研究不同方法注射乙肝免疫球蛋白(HBIG)对HBsAg伴HBeAg双阳性孕妇的乙肝病毒(HBV)宫内感染阻断作用。方法将137例双阳性孕妇分为4组:A组从孕16周起注射HBIG,B组从孕20周起注射HBIG,C组从孕28周起注射HBIG,A、B、C 3组孕妇每次均注射HBIG200IU,并间隔4周1次,直至临产;D组作为对照组,不注射HBIG;出生后4组所有新生儿均于16h内和生后2周注射HBIG200IU,满月起按1、2、7月龄分别接种乙肝疫苗,并定期随访。结果新生儿出生时外周血测得HBsAg,A组与B组无显著性差别(P>0.05),A、B 2组与C组、D组以及C组与D组均有显著性差别(P均<0.05);经随访A、B、C、D 4组HBV宫内感染率分别为5.6%、5.3%、19.4%和48.5%,母婴传播阻断率A组与B组无显著差异(P>0.05),A组和B组均显著高于C组和D组、C组显著高于D组(P均<0.05)。结论对HBsAg伴HBeAg双阳性孕妇,选择孕20周开始注射HBIG比较合适,阻断率最高,能有效减少HBV宫内感染的发生率。  相似文献   
95.
Effect of blocking N-methyl-D-aspartic acid (NMDA) and non-NMDA-glutamatergic receptors on performance in the plus-maze was studied in male rats bilaterally cannulated into the nucleus accumbens (Acc). Rats were divided into seven groups that received either 1 microl injections of saline, (+/-)2-amino-7-phosphonoheptanoic acid (AP-7, 0.2, 0.5, or 1 microg) or 2,3 dioxo-6-nitro-1,2,3,4,tetrahydrobenzo-(f)quinoxaline-7-sulphonamide disodium (NBQX, 0.2, 0.5, or 1 microg) 15 min before testing. Time spent in open arm, time per entry, end arrivals, open, closed, and total arm entries, relationship between open-, closed-, and total arm entries, rearing, face-, head-, and body grooming, and number of fecal boli were recorded. Time spent in the open arm increased under AP-7 (0.5 and 1 microg; P<.01) and NBQX (1 microg; P<.05) treatment, whereas time per entry was increased only with AP-7 (1 microg; P<.05). Open arm entries were increased by the intermediate doses of AP-7 (0.5 microg; P<.01) and NBQX (0.5 microg; P<.05); end arrivals were increased by the intermediate dose of AP-7 (0.5 microg/1 microl, P<.05). The frequency of rearing, grooming, and closed arm entries was not affected by the treatment. We conclude that NMDA and non-NMDA-glutamatergic blockade in the Acc lead to a behavioral disinhibition of cortical influences with the median doses, but that at higher doses the blockers have an anxiolytic-like effect.  相似文献   
96.
Israel has no official prevention policy at present against perinatal and horizontal transmission of hepatitis B virus (HBV) infection in newborns and children at risk. The present study was designed to assess the prevalence of HBV carrier state in a population of 11,123 pregnant women at term. Among this population (mean age 29.7 +/- 5.9), 98 women (0.88%) were found to be asymptomatic HBsAg+ carriers, and 97% of these carriers were anti-HBe+. Evidence for HBV replication, as determined by serum HBV-DNA, was established in 6.6% of the HBsAg+/anti-HBe+ population. The HBsAg carrier rate was strongly influenced by religion, continent, and country of birth of the carrier mothers. The highest relative carrier rate was found among women of Moslem origin (4.3%), as compared to Jewish women (0.67%). Most carrier women were born in Israel (56.1%) to mothers who had emigrated from regions with intermediate or high endemicity of HBV, such as North Africa or the Middle East. In these groups, the HBsAg carrier rate ranged between 1.2 and 3.0%. Ninety-three percent of newborns receiving passive/active vaccination against HBV developed protective levels of anti-HBs. Finally, evidence for horizontal transmission of HBV was found in 19.3% of 83 non-vaccinated children in families of HBsAg carriers. The present study therefore establishes HBsAg prevalence rates in specific risk groups of women at term and confirms the need for an official policy on immunization against HBV in Israel. Since over 50% of women at term belong to the defined risk groups, universal active vaccination of the entire newborn population each year is suggested as the most rational and needed policy in Israel.  相似文献   
97.
目的 探讨KCNN3基因1137~1140的4个碱基缺失所致移码突变与精神分裂症的关系。方法 95个核心家系共289名家庭成员,包含107例精神分裂症患者纳入本研究。精神分裂症采用CCMD-Ⅱ-R诊断标准。KCNN3基因1137~1140的4个碱基缺失基因型检测使用PCR技术和限制性内切酶DdeI消化方法。精神分裂症与KCNN3基因1137~1140缺失4个碱基的关联分析采用基于单倍型的单倍型相对风险率和传递/不平衡检验。结果 患者组与正常父母组比较,KCNN3基因1137~1140的4个碱基缺失的基因型频数和等位基因频率分布差异无统计学意义(χ^2=0.253,P〉0.05和χ^2=0.010,P〉0.05)。基于单倍型的单倍型相对风险分析发现父母传递与不传递给患者的KCNN3基因等位基因之间差异无统计学意义(χ^2=0.042,P〉0.05)。传递不平衡检验结果发现KCNN3基因等位基因传递不存在连锁不平衡(χ^2=3.000,P=0.0833)。结论 本组研究对象中,KCNN3基因第1外显子1137~1140的4个碱基缺失的发生率少;分析结果提示KCNN3基因第1外显子1137~1140的4个碱基缺失的等位基因与精神分裂症无关联。  相似文献   
98.
Human papillomavirus types in anogenital warts of children   总被引:3,自引:0,他引:3  
Tissue from anogenital warts of 25 children, 10 of whom were suspected of being victims of sexual abuse, was investigated by dot blot and Southern blot techniques for human papillomavirus (HPV) types. HPV DNA was detected in 22 children, two of whom had double infections. The genital HPV types 6 and/or 11 were detected in 20 children, and in three children other HPV types were found. One had HPV 18 (as well as 11); in a second child a possible skin type, HPV 2, was detected; and the third child was infected with an unidentified type. In three cases genital wart material was available from one of the parents, and in all three the HPV type was the same as that of the child. For nine other children one or both parents were reported to have genital warts. The source of infection appeared to be the adult genital tract, but sexual contact might not be the only means of transmission.  相似文献   
99.
早、中、晚孕期胎盘因子体外抗HIV-1的研究   总被引:1,自引:0,他引:1  
目的 探讨早、中、晚孕期胎盘因子(PF)体外抗人免疫缺陷病毒-1(HIV-1)及在HIV-1垂直传播中的作用.方法 荧光染料Calcien-AM标记的H9/HIV-1ⅢB分别与早、中、晚孕期不同稀释浓度的PF作用后,与MT2细胞培养,荧光显微镜下观察合胞休的形成;用HIV-1ⅢB感染MT2细胞,并分别与早、中、晚孕期不同稀释浓度的PF作用后,用MTT法检测HIV-1感染细胞的存活率,用ELISA方法检测细胞培养上清中p24抗原水平.结果 各孕期PF并不能抑制MT2和H9/HIV-1ⅢB细胞的融合,但可以增加HIV-1感染细胞的存活率及减少HIV-1 p24抗原的表达,且效应以早孕期PF最大,中孕期PF其次晚孕期PF最小,并与剂量呈正相关.结论 PF在体外具有抗HIV-I的作用,并呈现孕期和剂量相关性,可能在阻断HIV-1垂直传播中具有一定作用.  相似文献   
100.
Summary Optic fibers of retinal origin terminate in the lateral geniculate body exclusively in the so called glomerular synapses. They can be recognized on the basis of their unusually large irregular mitochondria having very few cristae. In the cat the structure of the optic terminal profiles is rather dense. The majority of terminals in most glomeruli originate from axons of other source. Relatively large axon terminal profiles of unusually light structure cannot be brought to degeneration by any interference with extraneous pathways. From Golgi information it becomes obvious that they originate from local Golgi 2nd type neurons. Small rather dense axonal profiles of the glomeruli can occasionally be traced back by degeneration to the occipital cortex (parastriate), although most of the descending cortical afferents of the lateral geniculate body terminate outside the glomeruli on more proximal parts of the dendrites. — Axo-axonic synapses are very frequent. If an optic terminal is involved, it appears that by structural standards it is presynaptic to the non optic. As judged, however, from the numerous axoaxonic contacts persisting after enucleation, many of the contacts are established between non optic axon terminals. — The progress of secondary degeneration and particularly the removal from the glomeruli of degeneration fragments is unexpectedly rapid. — The possible functional significance of these findings, especially also with regards to presynaptic inhibition, is discussed.  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