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   31901篇
  免费   2902篇
  国内免费   2401篇
耳鼻咽喉   235篇
儿科学   265篇
妇产科学   331篇
基础医学   3758篇
口腔科学   491篇
临床医学   4701篇
内科学   4655篇
皮肤病学   250篇
神经病学   1714篇
特种医学   1079篇
外国民族医学   21篇
外科学   2911篇
综合类   5405篇
现状与发展   5篇
一般理论   2篇
预防医学   1824篇
眼科学   1193篇
药学   3569篇
  26篇
中国医学   1893篇
肿瘤学   2876篇
  2024年   114篇
  2023年   565篇
  2022年   1475篇
  2021年   1769篇
  2020年   1358篇
  2019年   1219篇
  2018年   1115篇
  2017年   1155篇
  2016年   998篇
  2015年   1586篇
  2014年   1850篇
  2013年   1522篇
  2012年   2318篇
  2011年   2536篇
  2010年   1512篇
  2009年   1181篇
  2008年   1576篇
  2007年   1564篇
  2006年   1609篇
  2005年   1817篇
  2004年   994篇
  2003年   854篇
  2002年   779篇
  2001年   675篇
  2000年   651篇
  1999年   760篇
  1998年   542篇
  1997年   504篇
  1996年   391篇
  1995年   367篇
  1994年   304篇
  1993年   214篇
  1992年   233篇
  1991年   213篇
  1990年   195篇
  1989年   146篇
  1988年   149篇
  1987年   106篇
  1986年   103篇
  1985年   69篇
  1984年   31篇
  1983年   25篇
  1982年   17篇
  1981年   22篇
  1980年   12篇
  1979年   8篇
  1976年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Renal function in relation to three candidate genes in a Chinese population   总被引:3,自引:0,他引:3  
We recently found in a white population that the genes encoding angiotensin-converting enzyme (ACE, I/D polymorphism), -adducin (Gly460Trp), and aldosterone synthase (–344C/T) jointly influence renal function. We therefore investigated in a Chinese population the associations between the serum concentrations of creatinine and uric acid and these three genetic polymorphisms. We genotyped 471 ethnic Han Chinese subjects from 125 nuclear families recruited in northern China via random population sampling (75%) and at specialized hypertension clinics (25%). We performed population-based and family-based association analyses using generalized estimating equations (GEE) and quantitative transmission disequilibrium test (QTDT), respectively, while controlling for covariables. The participants were 39.7 years old and included 235 women (49.9%). The blood pressure measured at the subjects homes averaged 126/80 mmHg. Mean values were 71 µmol/l for serum creatinine, 111 ml min–1 1.73 m–2 for calculated creatinine clearance, and 236 µmol/l for serum uric acid. With adjustment for covariables, GEE analyses of single genes demonstrated that serum uric acid, but not serum creatinine, was positively associated with the ACE D allele. Serum uric acid concentrations were 15.8 µmol/l (95% confidence interval 3.3–28.2) and 25.7 µmol/l (11.1–40.2) higher in DD homozygotes than in ID and II subjects, respectively. Further GEE analyses of the three genes combined showed that the association between serum uric acid and the ACE polymorphism was confined to carriers of the -adducin Gly and/or aldosterone synthase C alleles. Sensitivity analyses in parents and offspring separately as well as QTDT analyses were confirmatory. Among 114 informative offspring carrying the -adducin Gly allele serum uric acid was significantly and positively associated with the transmission of the ACE D allele (=20.7 µmol/l). In conclusion, the present study extends our previous findings on the combined effects of the three candidate genes and supports the concept that these genetic polymorphisms jointly influence renal function.  相似文献   
992.
Li ZH  Zhou XP  Zhang X  Xie Y 《Archives of virology》2004,149(9):1721-1732
Summary. The importance of diseases of tomato caused by begomoviruses is increasing worldwide. Here, we report that several begomoviruses are associated with tomato leaf curl disease in Yunnan province, China. 14 tomato samples showing leaf curl symptoms were collected in three districts in Yunnan, and they fell into four groups according to their reaction with a panel of 16 monoclonal antibodies in TAS-ELISA. Comparison of partial DNA-A sequences amplified with degenerate primers confirmed the existence of several types of begomoviruses. The complete DNA-A sequences of 4 isolates (Y25, Y41, Y72, Y161), corresponding to the four groups, were determined. Sequence comparisons and phylogenetic analysis revealed that they corresponded to four previously identified begomoviruses. Groups I, II and IV are most closely related to Tomato yellow leaf curl China virus (TYLCCNV), Tobacco curly shoot virus (TbCSV) and Tobacco leaf curl Yunnan virus (TbLCYNV), respectively, while Group III shows close relationships with Tomato yellow leaf curl Thailand virus (TYLCTHV). In addition, all isolates in Groups I and III were found to be associated with DNA molecules, while satellite DNA was not found in virus isolates in Groups II and IV. The complete DNA sequences of three isolates from Group III (Y72, Y77, Y79) were determined. Sequence analysis showed that Y72, Y77 and Y79 seem to be different from other characterised DNA, sharing the highest nucleotide sequence identity with DNA of TbCSV.  相似文献   
993.
目的 探讨奥氮平治疗首发精神分裂症的临床疗效、不良反应。方法 将 3 6例符合 CCMD-2 -R诊断标准的首发精神分裂症病人予奥氮平治疗 8周 ,用阳性与阴性症状量表 ( PANSS)和副反应量表 ( TESS)评定其疗效和不良反应。结果 完成 8周治疗的 3 6例首发精神分裂症病人 ,基本痊愈 1 0例 ( 2 7.8% ) ,显进 1 2例 ( 3 3 .3 % ) ,进步 8例 ( 2 2 .2 % ) ,无效 6例( 1 6.7% ) ,总有效率为 83 .3 % ,不良反应少。结论 奥氮平治疗首发精神分裂症安全有效。  相似文献   
994.
Xie YF  Wang J  Huo FQ  Jia H  Tang JS 《Neuroscience》2004,126(3):717-726
The present study was designed to investigate the roles of different subtypes of opioid receptors in ventrolateral orbital cortex (VLO) opioid-evoked antinociception in formalin test by using an automatic detection system for recording the nociceptive behavior (agitation) and a manual method for detecting the duration of licking the injected paw in the conscious rat. Formalin (5%, 50 microl) s.c. injected into the hindpaw produced a biphasic agitation response or lengthening duration of licking. Morphine (5 microg) microinjected unilaterally into VLO significantly inhibited the agitation response and the licking time, and these effects were blocked by pre-administration of the non-selective opioid receptor antagonist naloxone (1.0 microg) into the same site. Microinjection of endomorphin-1 (5 microg), a selective micro-receptor agonist, and [D-Ala2, D-Leu5]-enkephalin (DADLE, 10 microg), a delta-/micro-receptor agonist also inhibited the nociceptive behaviors, and both the effects were blocked by selective mu-receptor antagonist beta-funaltrexamine hydrochloride (beta-FNA; 3.75 microg), but the DADLE-evoked inhibition was not influenced by the selective delta-receptor antagonist naltrindole (5 microg). Microinjection of selective kappa-receptor agonist (+/-)-trans-U-50488 methanesulfonate salt (1.5 microg) failed to alter the nociceptive behaviors induced by formalin injection. The beta-FNA and naloxone applied into VLO and morphine into the adjacent regions ventral and dorsal to VLO had no effect on the formalin-evoked nociceptive behaviors. These results suggest that mu- but not delta- or kappa-opioid receptor is involved in the VLO opioid-evoked antinociception in formalin test rat.  相似文献   
995.
Feng ML  Guo XJ  Zhang JY  Xie JH  Chen L  Lu Q  Yang JH  Ji Y  Qian KC 《Tissue antigens》2004,64(3):281-285
The purpose of this study was to investigate the genetic polymorphisms and haplotypes of microsatellite locus in exon 5 of the MICA gene and intron 1 of the MICB gene and human leukocyte antigen-B (HLA-B) gene based on 106 samples of the Guangzhou Han population through means of polymerase chain reaction and the fluorescent technique (6-FAM). The corresponding haplotype frequencies, linkage disequilibrium values and relative linkage disequilibrium values were estimated based on population data. The results show that the genotype distributions of MICA and MICB microsatellite and HLA-B satisfy the Hardy-Weinberg equilibrium. In total, five alleles of MICA microsatellite locus and 14 alleles of MICB microsatellite locus were observed. MICA A5 was the most common allele (0.2877), whereas A4 was the least common (0.1321). MICB CA14 was the most common allele (0.3255), and CA19 and CA28 were the two least common (0.0047). CA27 was not observed at all. Five kinds of MICA-MICB haplotypes, 18 kinds of MICA-HLA-B haplotypes and 12 kinds of MICB-HLA-B haplotypes occurred at frequencies of more than 1%. The common haplotypes of MICA-MICB, MICA-HLA-B and MICB-HLA-B were A5-CA14, A5.1-CA18, A4-CA26, A9-CA15, A5-B*15(62), A5.1-B*1301/1302, A4-B*1301/1302, A6-B*51, A6-B*4403, A9-B*3802, CA14-B*4601, CA18-B*1301/1302 and CA26-B*1301/1302, and these haplotypes showed strong linkage disequilibrium. The polymorphisms and haplotype distributions of MICA and MICB microsatellite and HLA-B locus in the Guangzhou Han population have their own distinct genetic characteristics. The microsatellite locus of exon 5 of the MICA gene and intron 1 of the MICB gene could therefore be used as genetic markers in the studies of anthropology, gene linkage analysis in genetic diseases, individual identification and paternity testing in forensic medicine.  相似文献   
996.
Accumulation of amyloid beta-peptides (Abeta) in the brain has been linked with memory loss in Alzheimer's disease and its animal models. However, the synaptic mechanism by which Abeta causes memory deficits remains unclear. We previously showed that acute application of Abeta inhibited long-term potentiation (LTP) in the hippocampal perforant path via activation of calcineurin, a Ca2+ -dependent protein phosphatase. This study examined whether Abeta could also inhibit Ca2+/calmodulin dependent protein kinase II (CaMKII), further disrupting the dynamic balance between protein kinase and phosphatase during synaptic plasticity. Immunoblot analysis was conducted to measure autophosphorylation of CaMKII at Thr286 and phosphorylation of the GluR1 subunit of AMPA receptors in single rat hippocampal slices. A high-frequency tetanus applied to the perforant path significantly increased CaMKII autophosphorylation and subsequent phosphorylation of GluR1 at Ser831, a CaMKII-dependent site, in the dentate area. Acute application of Abeta1-42 inhibited dentate LTP and associated phosphorylation processes, but was without effect on phosphorylation of GluR1 at Ser845, a protein kinase A-dependent site. These results suggest that activity-dependent CaMKII autophosphorylation and AMPA receptor phosphorylation are essential for dentate LTP. Disruption of such mechanisms could directly contribute to Abeta-induced deficits in hippocampal synaptic plasticity and memory.  相似文献   
997.
A new approach, short-oligonucleotide-ligation assay on DNA chip (SOLAC), is developed to detect mutations in rifampin-resistant Mycobacterium tuberculosis. The method needs only four common probes to detect 15 mutational variants of the rpoB gene within 12 h. Fifty-five rifampin-resistant M. tuberculosis isolates were analyzed, resulting in 87.3% accuracy and 83.6% concordance relative to DNA sequencing.  相似文献   
998.
The effect of membrane stretch on voltage-activated Ba2+ current (I Ba) was studied in antral circular myocytes of guinea-pig using the whole- cell patch-clamp technique. The changes in cell volume were elicited by superfusing the myocytes with anisosmotic solutions. Hyposmotic superfusate (202 mosmol/l) induced cell swelling and increased peak values of I Ba at 0 mV (from −406.6 ± 45.5 pA to −547.5 ± 65.6 pA, mean ± SEM, n = 8) and hyperosmotic superfusate (350 mosmol/l) induced cell shrinkage and decreased peak values of I Ba at 0 mV (to −269.5 ± 39.1 pA, n = 8). Such changes were reversible and the extent of change was dependent on the osmolarity of superfusate. The values of normalized I Ba at 0 mV were 1.43 ± 0.04, 1.30 ± 0.06, 1.23 ± 0.04, 1.19 ± 0.04, 1 and 0.68 ± 0.06 at 202, 220, 245, 267, 290 and 350 mosmol/l, respectively (n = 8). I Ba was almost completely blocked by nicardipine (5 μM) under hyposmotic conditions. The values of steady-state half-inactivation voltage (−37.7 ± 3.3 and −36.5 ± 2.6 mV, under control and hyposmotic conditions, respectively) or the half-activation voltage (−13.6 ± 2.3 and −13.9 ± 1.9 mV) of I Ba were not significantly changed (P > 0.05, n = 6). Cell membrane capacitance was slightly increased from 50.00 ± 2.86 pF to 50.22 ± 2.82 pF by a hyposmotic superfusate (P < 0.05, n = 6). It is suggested that cell swelling increases voltage-operated L-type calcium channel current and that such a property is related to the response of gastric smooth muscle to mechanical stimuli. Received: 14 November 1995/Received after revision and accepted: 8 January 1996  相似文献   
999.
用整肺灌洗法复制兔RDS模型,系统观察了灌洗液磷脂和蛋白质含量、血气、潮气量、肺顺应性、生命体征、X线胸片和病理形态学指标。结果显示:整肺灌洗法可迅速导致严重呼吸窘迫,其病理特征主要是PS系统功能急剧缺乏和肺损伤,用猪肺表面活性物质治疗后可获得明显改善。表明该模型病理性质介于ARDS和NRDS之间,用我们研制的猪肺表面活性物质替代治疗有较满意的疗效。  相似文献   
1000.
本文采用造血祖细胞体外培养技术观察了阵发性睡眠性血红蛋白尿(PNH)病人骨髓红系祖细胞(BFU一E和CFU一E)和粒一单系祖细胞(CFU一GM)的增殖能力;骨髓细胞经酸化AB型血清处理后的BFU一E,CFU一E和CFU一GM的增殖能力;以及BFU一E、CFU一E对红细胞生成素(Epo)和(CFU一GM对粒一单系集落刺激因子(GM一CSF)的反应能力,发现PNH病人骨髓BFU一E,CFU一E和CFU一GM集落数明显低于正常;骨髓细胞经新鲜酸化AB型血清处理后培养的BFU一E、CFU一E和CFU一GM集落数明显低于经热灭活酸化AB型血清处理后培养的集落数;以及BFU一E,CFU一E对Epo和CFU一GM对GM一CSF的剂量反应曲线低平。因此认为PNH病人骨髓红系和粒一单系祖细胞有以下特点:1.增殖能力降低:2.在酸性条件下对补体的敏感性增加;3.对造血因子的敏感性降低。  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