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   33921篇
  免费   3055篇
  国内免费   2508篇
耳鼻咽喉   239篇
儿科学   268篇
妇产科学   346篇
基础医学   3882篇
口腔科学   494篇
临床医学   4956篇
内科学   4868篇
皮肤病学   256篇
神经病学   1756篇
特种医学   1154篇
外国民族医学   21篇
外科学   3008篇
综合类   6060篇
现状与发展   5篇
一般理论   2篇
预防医学   2070篇
眼科学   1226篇
药学   3749篇
  27篇
中国医学   2117篇
肿瘤学   2980篇
  2024年   114篇
  2023年   571篇
  2022年   1493篇
  2021年   1789篇
  2020年   1365篇
  2019年   1231篇
  2018年   1138篇
  2017年   1191篇
  2016年   1013篇
  2015年   1632篇
  2014年   1925篇
  2013年   1621篇
  2012年   2521篇
  2011年   2814篇
  2010年   1724篇
  2009年   1376篇
  2008年   1824篇
  2007年   1782篇
  2006年   1824篇
  2005年   1999篇
  2004年   1080篇
  2003年   895篇
  2002年   804篇
  2001年   709篇
  2000年   679篇
  1999年   762篇
  1998年   536篇
  1997年   500篇
  1996年   390篇
  1995年   369篇
  1994年   303篇
  1993年   214篇
  1992年   231篇
  1991年   212篇
  1990年   191篇
  1989年   143篇
  1988年   146篇
  1987年   106篇
  1986年   101篇
  1985年   66篇
  1984年   29篇
  1983年   24篇
  1982年   11篇
  1981年   19篇
  1980年   9篇
  1979年   8篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
雌激素对去卵巢大鼠基底前脑NOS及Nestin阳性神经元的影响   总被引:5,自引:0,他引:5  
目的 观察雌激素替代对去卵巢大鼠基底前脑一氧化氮合酶(NOS)及巢蛋白(Nestin)阳性神经元的影响。方法 将28只健康成年雄性SD大鼠随机分为4个处理组:去势24 h雌激素替代组、去势2周雌激素替代组、去势植物油替代组及假手术组。用组织化学及免疫组织化学染色方法观察基底前脑的内侧隔核(MS)、斜角带垂直支(vDB)及水平支(hDB)的NOS和Nestin阳性神经元数的变化。结果 去势行植物油替代可使MS、vDB的NOS阳性神经元数明显下降(P<0.01);去势24 h或2周行雌激素替代均可使以上亚区的NOS阳性神经元数明显升高至正常水平(P<0.01)。去势行植物油替代或雌激素替代对hDB的:Nestin阳性神经元数的影响趋势与NOS阳性神经元的相似(P<0.01),但对MS及vDB的Nestin阳性神经元数影响不大(P>0.05)。结论 去卵巢行雌激素替代可选择性地使基底前脑不同亚区NOS、Nestin阳性神经元数升高,这可能与雌激素高调了NOS和Nestin的表达有关。  相似文献   
992.
腓总神经与腓骨颈的关系及其小腿各肌支的解剖学研究   总被引:2,自引:0,他引:2  
目的明确腓总神经与腓骨颈的关系以及小腿各肌支的解剖学特征。方法取成人下肢标本40例,在肉眼及放大镜下解剖,观察腓总神经与腓骨颈的关系以及腓总神经各肌支的数目及走行,以腓骨头最突出点为测量起点,测量腓总神经绕腓骨颈处至腓骨头最突出点的距离;测量各肌支的发出点、入肌点的高度,并作统计学分析。结果腓总神经绕腓骨颈处至腓骨头最突出点的距离,左、右侧分别为(1.64±0.36)cm和(1.58±0.34)cm。各肌支的数目不等,其中胫骨前肌支数目最多,腓骨短肌支和跗长伸肌支的数目较少。40例标本中,腓总神经均穿行于腓骨颈部骨一筋膜管。结论腓总神经在绕腓骨颈处均穿行于骨一筋膜管。提示:这可能是导致腓总神经卡压综合征的主要原因之一;不同肌肉的神经肌支数目差别较大,与其所支配肌肉的结构、功能有关。  相似文献   
993.
目的比较股骨粗隆间骨折两种治疗方法.方法共手术治疗31例,其中以改良Gamma钉固定8例,Richard's钉固定23例,对两组手术治疗的优良率进行分析比较,并做统计学处理.结果优良率Gamma钉组100%,Richard's钉组82.6%.两组有显著性差异(P<0.01).结论股骨粗隆间骨折,尤其是不稳定型/粉碎骨折的手术方式以Gamma钉治疗为宜,可以早期负重,减少并发症.  相似文献   
994.
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   
995.
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   
996.
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   
997.
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   
998.
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   
999.
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   
1000.
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   
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