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   47056篇
  免费   3358篇
  国内免费   1454篇
耳鼻咽喉   280篇
儿科学   912篇
妇产科学   445篇
基础医学   7109篇
口腔科学   600篇
临床医学   2490篇
内科学   6227篇
皮肤病学   955篇
神经病学   4896篇
特种医学   669篇
外国民族医学   4篇
外科学   4056篇
综合类   4519篇
现状与发展   2篇
预防医学   2242篇
眼科学   549篇
药学   9900篇
  6篇
中国医学   1665篇
肿瘤学   4342篇
  2024年   107篇
  2023年   989篇
  2022年   2004篇
  2021年   1954篇
  2020年   1518篇
  2019年   1907篇
  2018年   1728篇
  2017年   1583篇
  2016年   1264篇
  2015年   1465篇
  2014年   2248篇
  2013年   2738篇
  2012年   2168篇
  2011年   2644篇
  2010年   2244篇
  2009年   2133篇
  2008年   2196篇
  2007年   2031篇
  2006年   1853篇
  2005年   1566篇
  2004年   1507篇
  2003年   1340篇
  2002年   987篇
  2001年   757篇
  2000年   819篇
  1999年   685篇
  1998年   703篇
  1997年   636篇
  1996年   552篇
  1995年   512篇
  1994年   443篇
  1993年   428篇
  1992年   420篇
  1991年   370篇
  1990年   317篇
  1989年   295篇
  1988年   240篇
  1987年   244篇
  1986年   231篇
  1985年   490篇
  1984年   596篇
  1983年   390篇
  1982年   447篇
  1981年   401篇
  1980年   346篇
  1979年   320篇
  1978年   273篇
  1977年   184篇
  1976年   165篇
  1975年   132篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
目的 :生长抑素 (SS)结合氟尿嘧啶 (5 - Fu)治疗晚期壶腹部周围癌的疗效评价。方法 :2 8例晚期壶腹部周围癌患者均采用静脉插管及随身携带微型输注泵 ,SS/ 5 - Fu持续静脉滴注 (civ法 )。结果 :经 2周期治疗后 ,临床症状缓解 (DRSI)为 89.3% (2 5 / 2 8) ;肿瘤完全缓解 (CR)占 3.7% ,部分缓解 (PR) ,占 2 8.6 % ,稳定 (NC)占 4 6 .4 % ,有效率为 32 .1%。结论 :SS/ 5 - Fu化学治疗效果稳定 ,毒副作用轻微 ,是治疗晚期壶腹部周围癌的有效手段之一。  相似文献   
82.
防风化学成分的研究   总被引:11,自引:2,他引:9  
从防风甲醇提取物中分离得到11个结晶,分别鉴定为β-谷甾醇,香柑内酯,亥茅酚,胡萝卜甙,sec-O-glncosylhamaudol,5-O-甲基维斯阿米醇,升麻素,蔗糖,4-O-β-glucopyranosyl-5-O-methylvisamminol,prim-O-glucosylcimifugin,甘露醇。  相似文献   
83.
Neurons of in vitro guinea pig and rat auditory cortex receive a complex synaptic pattern of afferent information. As many as four synaptic responses to a single-stimulus pulse to the gray or white matter can occur; an early-EPSP followed, sequentially, by an early-IPSP, late-EPSP, and late-IPSP. Paired pulse stimulation and pharmacological studies show that the early-IPSP can modify information transmission that occurs by way of the early-EPSP. Each of these four synaptic responses differed in estimated reversal potential, and each was differentially sensitive to antagonism by pharmacological agents. DNQX (6,7-dinitroquinoxaline-2,3-dione), a quisqualate/kainate receptor antagonist, blocked the early-EPSP, and the late-EPSP was blocked by the NMDA receptor antagonist APV (D-2-amino-5-phosphonovalerate). The early-IPSP was blocked by the GABA-a receptor antagonist bicuculline, and the late-IPSP by the GABA-b receptor antagonists 2-OH saclofen or phaclofen. Presentation of stimulus trains, even at relatively low intensities, could produce a long-lasting APV-sensitive membrane depolarization. Also discussed is the possible role of these synaptic potentials in auditory cortical function and plasticity.  相似文献   
84.
To study the phenotypic specificity of S-100 beta and insulin-like growth factor II (IGF-II) for developing monoamine neurons, serotonin (5-HT) neurons from the embryonic day 14 (E14) rostral raphe or dopamine (TH) neurons from the substantia nigra/ventral tegmental area were cultured for 3 days in vitro (3 DIV) in the presence of these factors. Neuronotrophic effects were analyzed by computer-assisted morphometry of 5-HT and TH-immunoreactive neurons. S-100 beta and IGF-II differentially regulated the growth of 5-HT and TH neurons but did not affect their survival. S-100 beta significantly increased several parameters of neurite outgrowth by 5-HT neurons but inhibited the spatial extent (field area) of TH neurites. IGF-II promoted growth of cell bodies of both phenotype, but only stimulated neurite outgrowth by TH neurons. S-100 beta and IGF-II differentially affected the number of GFAP immunoreactive cells from raphe and substantia nigra, but these effects did not correlate with the specificity of neuronotrophic effects. S-100 beta and IGF-II immunoreactivities were expressed in glial cultures derived from the same brain regions, raising the possibility that these factors have autocrine effects on glia as well as paracrine actions on neurons. The results of this study suggest that specificity of neurotrophic factors for particular embryonic neurons may be correlated with their neurotransmitter phenotype.  相似文献   
85.
86.
目的腹内侧前额叶皮质在随意运动的起始和控制、情感以及认知中具有重要作用。然而,黑质-纹状体通路变性后腹内侧前额叶皮质的神经活动和5-HT_(1A)受体的作用仍不清楚。本研究观察了6-羟基多巴胺(6- hydroxydopamine,6-OHDA)损毁黑质致密部(substantia nigra pars compacta,SNc)后大鼠腹内侧前额叶皮质神经活动的变化和体循环给予选择性5-HT_(1A)受体拮抗剂WAY-100635后神经元活动的改变。方法采用在体玻璃微电极细胞外记录方法,记录正常大鼠和SNc单侧损毁大鼠的腹内侧前额叶皮质神经元的活动。结果6-OHDA损毁SNc大鼠的腹内侧前额叶皮质神经元放电频率显著增加,放电形式没有明显改变。体循环给予WAY-100635 (0.1 mg/kg,i.v.)不改变正常大鼠腹内侧前额叶皮质神经元的平均放电频率和放电形式,而显著降低了SNc损毁大鼠前额叶皮质神经元的平均放电频率。结论黑质-纹状体通路的变性可导致腹内侧前额叶皮质神经活动增强,5-HT_(1A)受体拮抗剂WAY-100635可以抑制这种活动增强,提示可能存在腹内侧前额叶皮质5-HT_(1A)受体功能失调。  相似文献   
87.
BACKGROUND: Selective serotonin reuptake inhibitors (SSRIs) effectively treat various anxiety disorders, although symptoms of anxiety are often exacerbated during early stages of treatment. We previously reported that acute treatment with the SSRI citalopram enhances the acquisition of auditory fear conditioning, which is consistent with the initial anxiogenic effects reported clinically. Here, we extend our findings by assessing the effects of acute SSRI treatment on the expression of previously acquired conditioned fear. METHODS: Rats underwent fear conditioning drug-free. Tone-evoked fear responses were tested after drug treatment the following day. This protocol more closely resembles the clinical setting than pre-conditioning treatment, because it evaluates effects of treatment on a pre-existing fear rather than on the formation of a new fear memory. RESULTS: A single pre-testing injection of the SSRIs citalopram or fluoxetine significantly increased fear expression. There was no effect of the antidepressant tianeptine or the norepinephrine reuptake inhibitor tomoxetine, indicating that this effect is specific to SSRIs. The SSRI-induced enhancement in fear expression was not blocked by tropisetron, a 5-HT(3) receptor antagonist, but was blocked by SB 242084, a specific 5-HT(2C) receptor antagonist. CONCLUSIONS: Enhanced activation of 5-HT(2C) receptors might be a mechanism for the anxiogenic effects of SSRIs observed initially during treatment.  相似文献   
88.
Dengue is a mosquito-borne viral disease caused by four antigenically distinct serotypes of dengue viruses (DENVs). This disease, which is prevalent in over a hundred tropical and sub-tropical countries of the world, represents a significant global public health problem. A tetravalent dengue vaccine capable of protecting against all four DENV serotypes has been elusive so far. Current efforts are focused on producing a tetravalent vaccine by mixing four monovalent vaccine components. In this work, we have utilized a discrete carboxy-terminal region of the major DENV envelope (E) protein, known as domain III (EDIII), which mediates virus entry into target cells and contains multiple serotype-specific neutralizing epitopes, to create a chimeric tetravalent antigen. This antigen derived by in-frame fusion of the EDIII-encoding sequences of the four DENV serotypes was expressed using a replication-defective recombinant human adenovirus type 5 (rAdV5) vaccine vector. This rAdV5 vector induced cell-mediated immune responses and virus-neutralizing antibodies specific to each of the four DENVs in mice. Interestingly, anti-AdV5 antibodies did not suppress the induction of DENV-specific neutralizing antibodies. We observed that anti-AdV5 antibodies in the sera of immunized mice could promote uptake of a rAdV5-derived reporter vector into U937 cells, suggesting that pre-existing immunity to AdV5 may in fact facilitate the uptake of rAdV5 vectored vaccines into antigen presenting cells. This work presents an alternative approach to developing a single component tetravalent vaccine that bypasses the complexities inherent in the currently adopted four-in-one physical mixture approach.  相似文献   
89.
恐惧应激对大鼠睾丸中Annexin5表达的影响   总被引:1,自引:0,他引:1  
目的观察大鼠应激条件下睾丸组织中Annexin5表达的变化。方法建立SD大鼠的恐惧应激模型,分别取急性应激、急性对照、慢性应激、慢性对照SD大鼠睾丸,免疫组织化学和Western blotting分析Annexin5免疫定位和蛋白表达。结果急性应激组与对照组相比,免疫组化显示Annexin5都定位在间质细胞、支持细胞和成熟的精子头部,Western blotting分析发现Annexin5的表达降低了10.8%;慢性应激组与对照组相比,免疫组化结果显示Annexin5在精子头部的定位逐渐减少,应激1w和2w组,未见到Annexin5定位于精子头部,到了应激的3w和4w,发现Annexin5重新定位于精子的头部,而在间质细胞和支持细胞上的定位模式没有显著变化。Western blotting分析发现Annexin5的表达降低了17.4%。结论大鼠睾丸Annexin5参与了应激过程,急性应激条件下Annexin5表达降低。随着应激时间的延长,在慢性应激条件下,Annexin5的表达由减少之后而开始有缓慢增加。  相似文献   
90.
目的:应用血清1,5-脱水葡糖醇(1,5AG)的酶动力学法,探讨其在糖尿病诊断中的应用价值。方法:应用全自动生化分析仪,采用全酶法测定健康人和糖尿病患者血清1,5AG的含量。结果:该法测定血清1,5AG精密度好,高、低值混合血清的CV分别为1.47%和1.70%;回收率分别为98.28%、101.32%和97.64%、103.36%,平均回收率为100.15%;在1,5-AG浓度为360μmol/L内呈良好的线性;60例糖尿患者血清1,5AG(5.38-59.54μmol/L)明显低于健康人(60.89~269.79μmol/L),P<0.01。结论:该方法重复性好,准确度高,工作试剂在2 d内稳定,适合常规实验室开展;血清1,5AG测定有助于糖尿病的诊断和治疗过程的监控。  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