全文获取类型
收费全文 | 408篇 |
免费 | 29篇 |
国内免费 | 32篇 |
专业分类
469篇 |
出版年
2022年 | 8篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 9篇 |
2018年 | 8篇 |
2017年 | 5篇 |
2016年 | 7篇 |
2015年 | 6篇 |
2014年 | 12篇 |
2013年 | 7篇 |
2012年 | 23篇 |
2011年 | 20篇 |
2010年 | 10篇 |
2009年 | 14篇 |
2008年 | 20篇 |
2007年 | 22篇 |
2006年 | 14篇 |
2005年 | 20篇 |
2004年 | 15篇 |
2003年 | 17篇 |
2002年 | 16篇 |
2001年 | 9篇 |
2000年 | 11篇 |
1999年 | 14篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 11篇 |
1988年 | 7篇 |
1987年 | 5篇 |
1986年 | 10篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 3篇 |
1979年 | 3篇 |
1978年 | 7篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1974年 | 10篇 |
1973年 | 9篇 |
1972年 | 3篇 |
1971年 | 6篇 |
1970年 | 3篇 |
1969年 | 8篇 |
1968年 | 4篇 |
1967年 | 4篇 |
1965年 | 3篇 |
排序方式: 共有469条查询结果,搜索用时 15 毫秒
61.
Claudia G Petersen Fabiana C Massaro Ana L Mauri Joao BA Oliveira Ricardo LR Baruffi Jose G FrancoJr 《Reproductive biology and endocrinology : RB&E》2010,8(1):149
Background
The present study aimed to evaluate the efficacy of the hyaluronic acid (HA) binding assay in the selection of motile spermatozoa with normal morphology at high magnification (8400x). 相似文献62.
VLJ Whitehall TD Dumenil DM McKeone CE Bond ML Bettington RL Buttenshaw L Bowdler GW Montgomery LF Wockner BA Leggett 《Epigenetics》2014,9(11):1454-1460
The CpG Island Methylator Phenotype (CIMP) is fundamental to an important subset of colorectal cancer; however, its cause is unknown. CIMP is associated with microsatellite instability but is also found in BRAF mutant microsatellite stable cancers that are associated with poor prognosis. The isocitrate dehydrogenase 1 (IDH1) gene causes CIMP in glioma due to an activating mutation that produces the 2-hydroxyglutarate oncometabolite. We therefore examined IDH1 alteration as a potential cause of CIMP in colorectal cancer. The IDH1 mutational hotspot was screened in 86 CIMP-positive and 80 CIMP-negative cancers. The entire coding sequence was examined in 81 CIMP-positive colorectal cancers. Forty-seven cancers varying by CIMP-status and IDH1 mutation status were examined using Illumina 450K DNA methylation microarrays. The R132C IDH1 mutation was detected in 4/166 cancers. All IDH1 mutations were in CIMP cancers that were BRAF mutant and microsatellite stable (4/45, 8.9%). Unsupervised hierarchical cluster analysis identified an IDH1 mutation-like methylation signature in approximately half of the CIMP-positive cancers. IDH1 mutation appears to cause CIMP in a small proportion of BRAF mutant, microsatellite stable colorectal cancers. This study provides a precedent that a single gene mutation may cause CIMP in colorectal cancer, and that this will be associated with a specific epigenetic signature and clinicopathological features. 相似文献
63.
Juan YS Hydery T Mannikarottu A Kogan B Schuler C Leggett RE Lin WY Huang CH Levin RM 《Molecular and cellular biochemistry》2008,311(1-2):73-80
Purpose Ischemia, reperfusion, and free radical generation have been recently implicated in the progressive bladder dysfunction.
Coenzyme Q10 (CoQ10) is a pro-vitamin like substance that appears to be efficient for treatment of neurodegenerative disorders
and ischemic heart disease. Our goal was to investigate the potential protective effect of CoQ10 in a rabbit model of in vivo
bilateral ischemia and ischemia/reperfusion (I/R). Material and Methods Six groups of four male New Zealand White rabbits each were treated with CoQ10 (3 mg/kg body weight/day—dissolved in peanut
oil) (groups 1–3) or vehicle (peanut oil) (groups 4–6). Groups 1 and 4 (ischemia-alone groups) had clamped bilateral vesical
arteries for 2 h; in groups 2 and 5 (I/R groups), bilateral ischemia was similarly induced and the rabbits were allowed to
recover for 2 weeks. Groups 3 and 6 were controls (shams) and were exposed to sham surgery. The effects on contractile responses
to various stimulations and biochemical studies such as citrate synthase (CS), choline acetyltransferase (ChAT), superoxide
dismutase (SOD), and catalase (CAT) were evaluated. The protein peroxidation indicator, carbonyl group, and nitrotyrosine
contents were analyzed by Western blotting. Results Ischemia resulted in significant reductions in the contractile responses to all forms of stimulation in vehicle-fed rabbits,
whereas there were no reductions in CoQ10-treated rabbits. Contractile responses were significantly reduced in vehicle-treated
I/R groups, but significantly improved in CoQ10-treated rabbits. Protein carbonylation and nitration increased significantly
in ischemia-alone and I/R bladders; CoQ10 treatment significantly attenuated protein carbonylation and nitration. CoQ10 up-regulated
SOD and CAT activities in control animals; the few differences in CoQ10-treated animal in SOD and CAT after ischemia and in
general increase CAT activities following I/R. Conclusions CoQ10 supplementation provides bladder protection against I/R injury. This protection effect improves mitochondrial function
during I/R by repleting mitochondrial CoQ10 stores and potentiating their antioxidant properties. 相似文献
64.
65.
目的观察血液磁极化疗法(简称血磁治疗)对糖尿病(DM)的治疗效果和对胰岛功能的影响。方法制备了四氧嘧啶DM兔模型20只,随机分为两组,即DM模型血磁治疗组及DM模型未治疗组,同时设立正常对照组10只,分别测定治疗前后空腹血糖(FPG)、糖化血红蛋白(HbA1c)、胰岛素(INS)及C-肽(C-P),并于观察期结束后处死动物取胰腺组织常规石蜡包埋切片,行HE及Mallory三色法特殊染色观察3组胰岛形态学变化。结果血磁治疗显著降低DM兔的FPG(P<0.001)。DM治疗组INS及C-P水平较治疗前明显升高(P<0.01),与未治疗组相比差异显著(P<0.05)。胰岛病理改变可见治疗组β细胞数量明显多于DM未治疗组,提示血磁疗法具有促进胰岛修复,改善胰岛功能的作用。结论血磁疗法能够促进DM时受损胰岛组织的修复,改善胰岛β细胞分泌功能,降血糖作用明显。 相似文献
66.
犬MC1R基因T105A基因座多态性及 与毛色性状相关性的研究The 总被引:2,自引:2,他引:2
为了检测犬MC1R基因T105A基因座的多态性,并分析该多态性与犬毛色表型的相关性,抽取111只外科手术学实验用杂种犬血液并提取DNA,记录毛色表型。采用PCR-RFLP技术,对MC1R基因T105A基因座进行基因多态性分析,并对该基因座DNA进行克隆测序;用二元变量相关分析的统计学方法分析基因座多态性与毛色性状之间的相关性。经PCR-RFLP分析结果表明,T105A基因座序列具有多态性,表现为A、B二个等位基因和AA、AB及BB 3种基因型。A、B等位基因频率分别为72.97%和27.03%,基因杂合度(H)为0.39。基因型AA频率为55.86%,BB为9.91%,AB为34.23%。对T105A多态性片段DNA克隆测序后发现,MC1R基因在编码第105位氨基酸的密码子第一个碱基存在由G到A的单碱基突变,该突变导致第105位氨基酸发生由丙氨酸向苏氨酸的改变。统计分析结果表明MC1R基因T105A基因座的多态性与毛色性状不存在显著的相关性,这可能是由于外科手术学实验用犬是杂种犬,其遗传背景不同所致,尚须在纯种犬群体中进一步研究MC1R基因对毛色的影响。
Abstract: In order to detect the polymorphism of T105A in MC1R gene in dogs and to analyze the relationship between the genetic polymorphisms and phenotypes of dog coat color, the blood samples of 111 cross-breed dogs were taken and their genomic DNAs were extracted. The phenotypes of dog coat color were recorded. The T105A locus of MC1R gene in the canine was detected through the technology of PCR-RFLP. Furthermore, the polymorphic fragments at T105A were sequenced. The relationships between the polymorphism of T105A and coat color trait were analyzed by the statistical methods of bivarate correlation analysis. By the method of PCR-RFLP, the T105A polymorphism was found with two alleles A and B and three genotypes AA, AB and BB. The frequencies of two alleles were 72.97% and 27.03%, respectively. The heterozygosity of T105A locus was 0.39. The frequencies of three genotypes were 55.86%, 34.23% and 9.91%, respectively. According to the results of sequencing, one base change from G to A at the position 105 was found at T105A locus and it altered amino acid at the position 105 from alanine to threonine. According to the statistical analysis, no significant association between the polymorphism of MC1R gene and the coat color was found and the result may be due to the differences of genetic background. Further research on MC1R gene should be done in pure breed dogs. 相似文献
67.
莲藕干物质和氮磷钾养分的累积与分配研究 总被引:1,自引:0,他引:1
连续2年采用盆栽试验研究了莲藕(Nelumbo nucifera Gaertn)干物质和氮磷钾养分的累积与分配规律。结果表明:莲藕苗期以叶片生长并积累光合产物为主,膨大根状茎成型后,叶片、叶柄和根状茎中的干物质不断运输并贮存到膨大根状茎中,以产量形成为主,干物质累积总量增长呈"慢-快-稳定"的变化趋势;氮磷钾累积量与干物质累积量变化趋势一致,并与之呈极显著正相关,莲藕氮磷钾养分累积总量之比为1∶0.12∶1.31。移栽后97-160 d是莲藕产量形成的关键时期,不仅叶片、叶柄和根状茎中的氮磷钾随同干物质运输并贮存到膨大根状茎中,根系还从土壤中吸收更多的氮磷钾直接运输并贮存到膨大根状茎中,后者分别占同期氮磷钾累积量的69.8%、79.2%和75.0%。160 d膨大根状茎中干物质、氮、磷和钾累积量分别平均占植株总累积量的81.1%、85.2%、88.8%和80.2%。 相似文献
68.
69.
Data for the historical years 1970 and 1995 and the FAO-Agriculture Towards 2030 projection are used to calculate N inputs (N fertilizer, animal manure, biological N fixation and atmospheric deposition) and the N export from the field in harvested crops and grass and grass consumption by grazing animals. In most industrialized countries we see a gradual increase of the overall N recovery of the intensive agricultural production systems over the whole 1970-2030 period. In contrast, low N input systems in many developing countries sustained low crop yields for many years but at the cost of soil fertility by depleting soil nutrient pools. In most developing countries the N recovery will increase in the coming decades by increasing efficiencies of N use in both crop and livestock production systems. The surface balance surplus of N is lost from the agricultural system via different pathways, including NH3 volatilization, denitrification, N2O and NO emissions, and nitrate leaching from the root zone. Global NH3-N emissions from fertilizer and animal manure application and stored manure increased from 18 to 34 Tg·yr-1 between 1970 and 1995, and will further increase to 44 Tg·yr-1 in 2030. Similar developments are seen for N2O-N (2.0 Tg·yr-1 in 1970, 2.7 Tg·yr-1 in 1995 and 3.5 Tg·yr-1 in 2030) and NO-N emissions (1.1 Tg·yr-1 in 1970, 1.5Tg·yr-1 in 1995 and 2.0 Tg·yr-1 in 2030). 相似文献
70.