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   68788篇
  免费   4881篇
  国内免费   2486篇
耳鼻咽喉   304篇
儿科学   945篇
妇产科学   1008篇
基础医学   11836篇
口腔科学   949篇
临床医学   3716篇
内科学   10733篇
皮肤病学   1062篇
神经病学   10293篇
特种医学   833篇
外国民族医学   20篇
外科学   4073篇
综合类   7474篇
现状与发展   7篇
预防医学   1631篇
眼科学   613篇
药学   13135篇
  5篇
中国医学   1456篇
肿瘤学   6062篇
  2024年   81篇
  2023年   757篇
  2022年   1154篇
  2021年   2028篇
  2020年   1747篇
  2019年   1779篇
  2018年   1867篇
  2017年   1885篇
  2016年   1957篇
  2015年   2295篇
  2014年   3816篇
  2013年   5068篇
  2012年   3817篇
  2011年   4417篇
  2010年   3679篇
  2009年   3747篇
  2008年   4072篇
  2007年   3656篇
  2006年   3189篇
  2005年   2718篇
  2004年   2555篇
  2003年   2370篇
  2002年   1891篇
  2001年   1621篇
  2000年   1473篇
  1999年   1300篇
  1998年   1486篇
  1997年   1375篇
  1996年   1251篇
  1995年   987篇
  1994年   900篇
  1993年   808篇
  1992年   602篇
  1991年   555篇
  1990年   412篇
  1989年   352篇
  1988年   298篇
  1987年   272篇
  1986年   288篇
  1985年   342篇
  1984年   285篇
  1983年   178篇
  1982年   234篇
  1981年   188篇
  1980年   131篇
  1979年   80篇
  1978年   54篇
  1977年   41篇
  1976年   32篇
  1975年   30篇
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
81.
目的 探讨慢性非细菌性前列腺炎(CNP)和前列腺痛(PD)的治疗方法。方法 应用体外短波热疗联合前列腺灸及α1A-肾上腺素能受体阻滞剂哈乐治疗CNP和PD患者26例,疗程8周。观察治疗前后前列腺炎症状评分(CPSI)与最大尿流率(MFR)变化。结果 有效率为80.8%。治疗前后CPSI和MFR均有显著改善(P〈0.05)。结论 体外短波热疗联合前列腺灸及哈乐治疗CNP和PD安全有效。  相似文献   
82.
湖北人群Toll样受体4基因多态性研究   总被引:5,自引:0,他引:5  
目的 研究湖北人群Toll样受体4(TLR4)Asp299Gly和Thr399Ile基因多态性分布特征。方法 采用等位基因特异性聚合酶链反应(ASPCR)-限制酶片断长度多态性(RFLP)检测TLR4 Asp299Gly和Thr399 Ile基因多态性。结果 在所有的253例中国湖北人群样本中,没有检测到TLR4 Asp299Gly和Thr399Ile基因多态性存在。结论 TLR4基因多态性在不同地区和人群发生的频率是不同的,与白种人相比,中国湖北人群的TLR4Asp299G1y和Thr399Ile的基因多态性非常罕见。  相似文献   
83.
Interaction with adenosine A1 receptors is a possible contributory mechanism to the anticonvulsant effects of carbamazepine (CBZ) and the dihydropyridine calcium antagonists. We measured the binding of [3H]cyclohexyladenosine to adenosine A1 receptors in mouse brain stem, cerebellum, and cortex after oral administration of nifedipine, nimodipine (NMD), and CBZ for 7 days and compared the results with binding in control mice. Equilibrium dissociation constant (Kd) and receptor numbers (Bmax) were calculated using Scatchard and saturation isotherm analyses. Mean Kds (SEM) in control brain stem, cerebellum, and cortex were 2.09 (0.31), 2.39 (0.2), and 3.12 (0.28) nM, respectively. Results of Bmax for the same areas were 188 (26), 280 (24), and 449 (54) fmol/mg protein. Nifedipine (p less than 0.005) and NMD (p less than 0.02) raised the Kd of A1 receptors only in the cerebellum, and CBZ increased cerebellar Bmax (p less than 0.05). These minor effects on A1 receptors in CF1 mice, when given in doses previously shown to have anticonvulsant properties in these animals, do not suggest that alteration in A1 receptor activity is an important mechanism for the anticonvulsant effects of these drugs.  相似文献   
84.
Targeted imaging requires site-specific accumulation of a contrast agent (CA), and the properties of that agent must be selected according to the abundance of the target to obtain a signal above the detection limit of the instrument. However, numerical estimates of receptors per cell are rarely found in the literature. Integrin receptors would be particularly promising targets because of their accessibility from the blood stream and expression on activated neovascular endothelial cells. We systematically estimated the number of integrin receptors of cell lines and primary cells by flow cytometry analysis. Since integrin receptors are heterodimeric molecules, and alpha(v) forms complexes with various beta subunits, the numbers of alpha(v) and beta(3) subunits are therefore dissimilar. The observed values are 3 . 10(3)-1.4 . 10(4)/cell for alpha(v), and 5.3 . 10(2)-1.1 . 10(4)/cell for beta(3). Despite the low number of exposed receptors, we show that up to single-cell MR visualization can be achieved with the use of iron oxide beads complexed with antibodies as CAs.  相似文献   
85.
目的探讨性别差异对脓毒症大鼠肝脏组织Toll样受体4(TLR4)和髓样分化蛋白- 2(MD-2)基因表达的影响。方法以脂多糖(LPS)按5 mg/kg体重由大鼠腹腔注射制作脓毒症动物模型,注射后2 h留取肝脏组织检测TLR4、MD-2和肿瘤坏死因子-α(TNF-α)基因表达,同时测定各组大鼠血浆中丙氨酸氨基转移酶(ALT)及雌二醇含量。结果正常雌雄性大鼠肝脏组织均可表达少量TLR4、MD-2、TNF-α基因,其中雌性组分别为0.175±0.034、0.211±0.044、0.201±0.068; 雄性组分别为0.205±0.061、0.243±0.049、0.243±0.063,两组数据差异无统计学意义(P> 0.05),但LPS刺激后雌性大鼠肝脏组织上述指标分别为0.615±0.089、0.708±0.181、0.730± 0.118,血浆中ALT含量为(81.07±10.72)U/L;雄性组分别为0.723±0.091、1.123±0.272、 0.881±0.156,ALT含量为(106.39±14.21)U/L,雌性组各项指标均明显低于雄性大鼠(P< 0.05)。相关分析表明雌性及雄性脓毒症大鼠肝脏组织TLR4及TNF-α基因表达与相应性别大鼠血浆中雌二醇含量呈显著负相关(P<0.05)。结论 LPS刺激后大鼠肝脏组织TLR4、MD-2及 TNF-α基因表达存在性别差异,内源性雌激素的作用可能导致雌性脓毒症大鼠肝脏组织损伤较雄性轻。  相似文献   
86.
High cord blood immunoglobulin E (cbIgE) is known to be associated with increased risks of atopic diseases in childhood. The relationship between genetic polymorphisms and high cbIgE has not been well documented. A cross-sectional study was conducted to assess the association between cbIgE and genetic polymorphisms of interleukin (IL)-4 -590C/T, the beta-subunit of the high-affinity receptor for IgE (FcepsilonRI-beta) E237G, lymphotoxin (LT)-alphaNcoI alleles, and tumor necrosis factor (TNF)-alpha -308G/A. A total of 320 mother-neonate pairs were recruited from four maternity hospitals from different locations of Taiwan. Cord blood was obtained and assayed for cbIgE. Polymerase chain reaction followed by restriction fragment length polymorphism was used to assess the genotypes. Three hundred pairs of mothers and neonates were included in the final analysis. Infants with IL-4 -590 C allele were found to have higher risk of elevated cbIgE (> or =0.35 IU/ml, 24.3%) (p = 0.004). After adjusting for gender, birth order, maternal age, and history of allergic disease in maternal and paternal families, odds ratios for CC and CT genotypes were 4.41 and 3.16 (95% confidence interval 0.78-22.67, and 1.66-6.13), respectively, using TT genotype as reference. The genotypes of FcepsilonRI-beta, LT-alpha, and TNF-alpha were not associated with cbIgE before or after the adjustment. Our finding suggested a significant association of cbIgE with genetic polymorphism of IL-4 -590C/T, but not with the genotypes of FcepsilonRI-beta, LT-alpha, and TNF-alpha.  相似文献   
87.
BACKGROUND: To understand the immunopathological features of oral lichen planus (OLP), we analyzed the expression of chemokines in the epithelial cell layers. Methods: Epithelia from OLP or healthy gingiva were collected by laser microdissection. The chemokine and chemokine receptor expressions in the epithelia were analyzed by DNA microarray. RESULTS: High levels of MIP-3alpha/LARC/CCL20 and its receptor CCR6 were expressed in the lesional epithelia. Furthermore, DC-CK1/CCL18, ELC/CCL19, SDF-1/CXCL12 and CXCR4 expressions were also increased. Immunohistologial analysis showed that high numbers of Langerhans cells (LCs) were present in the epithelia of OLP. Lesional epithelia also expressed high levels of the ligands specific for CXCR3 (e.g. MIG/CXCL9, IP-10/CXCL10 and I-TAC/CXCL11) and CCR5 (e.g. RANTES/CCL5). CONCLUSIONS: Infiltration of LCs is orchestrated by CCR6. Further, LCs residing in the lesional epithelia may be a mature phenotype. Moreover, infiltration of T cells in OLP could be mediated by signaling pathways through CXCR3 and CCR5.  相似文献   
88.
AIM: To investigate the participation of adenosine receptors in the adenosine 5'-triphosphate (ATP)-induced relaxation in the corpus cavernosum penis (CCP) of rabbits. METHODS: The ATP-induced relaxation was assessed on the noradrenaline precontracted CCP of rabbits in the presence and absence of 8-(3-chlorostyryl)caffeine (CSC); an adenosine A(2A) receptor antagonist; alloxazine and MRS1754; adenosine A(2B) receptor antagonists; and ARL67156, an inhibitor of ecto-nucleoside triphosphate diphosphohydrolases. RESULTS: Adenosine and ATP relaxed the noradrenaline precontracted CCP of rabbits in a concentration-dependent manner. The adenosine- and ATP-induced relaxations were suppressed by alloxazine and MRS1754, but not by 8-(3-chlorostyryl)caffeine. ARL67156 potentiated the ATP-induced relaxation but not the adenosine-induced one. MRS1754 suppressed the ATP-induced relaxation potentiated by ARL67156. CONCLUSIONS: The above results suggest that, in the CCP of rabbits, the adenosine receptor mediating adenosine-induced relaxation is of the A(2B) receptor and the ATP directly causes relaxation through the A(2B) receptor on the CCP.  相似文献   
89.
目的构建大鼠维生素D受体(VDR)蛋白表达载体,测定并分析遗传性高钙尿性结石(GHS)大鼠VDRcDNA序列。方法采用半定量逆转录-聚合酶链反应(RT—PCR)方法扩增含VDR蛋白编码基因序列,将扩增产物克隆至真核表达载体pcDNA3.1/Zero(+),对5只GHS大鼠和4只正常尿钙对照(NC)大鼠十二指肠VDRcDNA序列进行测序分析。结果琼脂糖凝胶电泳示PCR扩增产物碱基数目与目的片段大小一致。对重组质粒的分析表明,插入片段的序列与发表的VDR基因编码序列相同。5只GHS鼠和4只NC鼠肠VDR cDNA序列均有3个相同的位点不同于已公布的大鼠肠VDR cDNA序列:在256bp位点:C取代G;569bp位点:G代替A;1658位点:A替代G。另外,GHS鼠在1795bp位点发生改变,G取代A,而NC鼠则无改变。结论大鼠维生素D受体蛋白编码序列被成功地克隆至表达载pcDNA3.1/Zero(+)上。GHS大鼠基因编码区的序列组成同NC大鼠相一致,但GHS鼠1795bp位点的碱基改变未见于NC鼠。  相似文献   
90.
Audiogenic seizures can be induced in DBA/2J mice following intense auditory stimulation. A number of neurotransmitters, including 5-hydroxytryptamine (5-HT), are believed to be involved in mediating this effect since it has been shown previously that depletion of 5-HT or blockade of 5-HT receptors protects DBA/2J mice from these audiogenic seizures. The present study was undertaken to determine whether antagonism of the newly identified 5-HT7 receptor may protect DBA/2J mice from audiogenic seizures by attempting to correlate in vivo potency of compounds with their affinity at the 5-HT7 receptor. All compounds used in the correlation were shown to be antagonists at the 5-HT7 receptor and a statistically significant correlation was observed between 5-HT7 affinity and doses for half-maximal response (ED50) for protection of DBA/2J mice from sound-induced seizures (r = 0.80; P < 0.05). No significant correlation was observed between in vivo activity and affinity at either 5-HT1A, 5-HT2A or 5-HT2C receptors. It is also unlikely that interactions between the 5-ht5 receptor will protect DBA/2J mice from audiogenic seizures since metergoline and mesulergine which are both active in this in vivo model have no affinity for the 5-ht5 receptor. There are similarities between the pharmacology of the 5-HT7 receptor and that of the 5-HT1A receptor, however the correlation between the in vivo potency in DBA/2J mice and 5-HT1A affinity was not significant. Furthermore, the 5-HT1A receptor antagonist WAY 100135 did not protect DBA/2J mice from audiogenic seizures at doses that antagonise 5-HT1A receptor-mediated effects in mice. These data suggest that antagonism of 5-HT7 receptors may protect against audiogenic seizures in DBA/2J mice although a definitive conclusion must await studies with selective 5-HT7 antagonists. Received: 20 March 1997 / Accepted: 10 August 1997  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