全文获取类型
收费全文 | 5758篇 |
免费 | 373篇 |
国内免费 | 360篇 |
出版年
2024年 | 12篇 |
2023年 | 81篇 |
2022年 | 167篇 |
2021年 | 304篇 |
2020年 | 170篇 |
2019年 | 209篇 |
2018年 | 235篇 |
2017年 | 176篇 |
2016年 | 226篇 |
2015年 | 358篇 |
2014年 | 389篇 |
2013年 | 494篇 |
2012年 | 552篇 |
2011年 | 430篇 |
2010年 | 277篇 |
2009年 | 244篇 |
2008年 | 252篇 |
2007年 | 250篇 |
2006年 | 240篇 |
2005年 | 219篇 |
2004年 | 141篇 |
2003年 | 118篇 |
2002年 | 117篇 |
2001年 | 118篇 |
2000年 | 90篇 |
1999年 | 119篇 |
1998年 | 50篇 |
1997年 | 63篇 |
1996年 | 53篇 |
1995年 | 29篇 |
1994年 | 36篇 |
1993年 | 31篇 |
1992年 | 41篇 |
1991年 | 35篇 |
1990年 | 29篇 |
1989年 | 23篇 |
1988年 | 19篇 |
1987年 | 13篇 |
1986年 | 18篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 4篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1969年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有6491条查询结果,搜索用时 15 毫秒
151.
Wenjing Song Huwei Sun Jiao Li Xianpo Gong Shuangjie Huang Xudong Zhu Yali Zhang Guohua Xu 《Annals of botany》2013,112(7):1383-1393
Background and Aims
Although ammonium (NH4+) is the preferred form of nitrogen over nitrate (NO3−) for rice (Oryza sativa), lateral root (LR) growth in roots is enhanced by partial NO3− nutrition (PNN). The roles of auxin distribution and polar transport in LR formation in response to localized NO3− availability are not known.Methods
Time-course studies in a split-root experimental system were used to investigate LR development patterns, auxin distribution, polar auxin transport and expression of auxin transporter genes in LR zones in response to localized PNN in ‘Nanguang’ and ‘Elio’ rice cultivars, which show high and low responsiveness to NO3−, respectively. Patterns of auxin distribution and the effects of polar auxin transport inhibitors were also examined in DR5::GUS transgenic plants.Key Results
Initiation of LRs was enhanced by PNN after 7 d cultivation in ‘Nanguang’ but not in ‘Elio’. Auxin concentration in the roots of ‘Nanguang’ increased by approx. 24 % after 5 d cultivation with PNN compared with NH4+ as the sole nitrogen source, but no difference was observed in ‘Elio’. More auxin flux into the LR zone in ‘Nanguang’ roots was observed in response to NO3− compared with NH4+ treatment. A greater number of auxin influx and efflux transporter genes showed increased expression in the LR zone in response to PNN in ‘Nanguang’ than in ‘Elio’.Conclusions
The results indicate that higher NO3− responsiveness is associated with greater auxin accumulation in the LR zone and is strongly related to a higher rate of LR initiation in the cultivar ‘Nanguang’. 相似文献152.
153.
Haiyan Chu Qinghong Zhao Shizhi Wang Meilin Wang Ming Xu Yan Gao Dewei Luo Yongfei Tan Weida Gong Zhengdong Zhang Dongmei Wu 《Gene》2013
ERCC4 plays an essential role in the nucleotide excision repair (NER) pathway, which is involved in the removal of a wide variety of DNA lesions. To determine whether the ERCC4 tagging SNPs (tSNPs) are associated with risk of gastric cancer, we conducted a hospital-based case-control study of 350 cases and 468 cancer-free controls. In the logistic regression (LR) analysis, we found a significantly decreased risk of gastric cancer associated with the rs744154 GC/CC genotypes [adjusted odds ratio (OR) = 0.56, 95% confidence interval (CI) = 0.42–0.75, false discovery rate (FDR) P = 0.003] compared with the wild-type GG genotype. Haplotype-based association study revealed that the CGC haplotype that containing the rs744154 C allele can decrease the risk of gastric cancer compared with the most common haplotype GGT (adjusted OR = 0.61, 95% CI = 0.46–0.81). Using the multifactor dimensionality reduction (MDR) analysis, we identified that the SNP rs744154 and smoking status were the best two predictive factors for gastric cancer with a testing accuracy of 55.76% and a perfect cross-validation consistency (CVC) of 10 (P = 0.001). Furthermore, the smokers with the rs744154 GC/CC genotypes showed a decreased risk of gastric cancer (adjusted OR = 0.55, 95% CI = 0.35–0.85) compared with the smokers with the GG genotype using multivariate LR analysis. The above findings consistently suggested that genetic variants in the ERCC4 gene may play a protective role in the etiology of gastric cancer, even in the smokers. 相似文献
154.
前期研究脑表明,脑胶质瘤干细胞(glioma stem cells,GSCs)是胶质瘤发生和发展的重要因素,探索靶向干预GSCs生长有可能成为脑胶质瘤治疗的有效途径之一。该研究旨在阐明两种药物ATRA和Y-分泌酶抑制剂DAPT协同抑制GSCs自我更新的生物学效应。通过用台盼蓝排染法、克隆球形成试验和免疫印迹分析了两种药物的单独使用或联用对GSC样细胞PGCl和PGC2生长、成球能力和自我更新以及干细胞标志物表达的影响。结果发现,单独使用ATRA对PGCl生长有一定的抑制作用,而对PGC2生长几乎没有影响;DAPT对PGCs的生长抑制作用明显强于ATRA。高浓度ATRA(80μmol/L)能诱导PGCs的分化,降低PGCs成球大小,且成球效率降至5%~8%,而正常对照组为32%~35%;同样,DAPT(40μmol/L)也能降低PGCs成球大小,且成球效率降至2%~3%;低浓度ATRA(20μmol/L)和DAPT(5gmol/L)对PGCs自我更新能力和干性没有明显影响,而联合使用后其明显降低PGCs的成球大小,且成球效率降至3%~5%,促进细胞凋亡,并且明显抑制了干细胞标志物Nestin、CDl33、Sox2、Oct4的表达,提高了分化标志物GFAP的表达。该研究证明了低浓度的ATRA和DAPT能协同抑制脑胶质瘤干细胞PGCs的自我更新。研究结果将为脑胶质瘤的临床研究提供实验依据。 相似文献
155.
156.
Li-nian Huang Dong-sheng Wang Yu-qing Chen Cheng-ling Zhao Bei-lei Gong An-bang Jiang Wei Jia Feng-dan Hu 《Molecular biology reports》2013,40(2):917-924
Among new biological markers that could become useful prognostic factors for non-small cell lung cancer (NSCLC). Survivin is one of the most commonly over-expressed oncogenes, however, its role in NSCLC remains controversial. We performed a systematic review of the literature with meta-analysis to clarify this issue. Electronic databases were used to identify published studies before August 2011. Pooled hazard ratio (HR) with 95 % confidence interval (95 % CI) was used to estimate the strength of the association of survivin expression with survival of NSCLC patients. Heterogeneity and publication bias were also assessed. Overall 29 relevant published studies including 2,517 lung cancer patients were identified from electronic databases. We found that overexpression of survivin in NSCLC patients might be a poor prognostic factor for survival 1.95 (95 % CI: 1.65-2.29; P < 0.001). Heterogeneity testing indicated that there was heterogeneity among studies. When stratified by histology types, the heterogeneity was absent. We should point out that the publication bias may partly account for the result, but the conclusion might not be affected deeply by the publication bias. When we accounted for publication bias using the trim and fill method, the results remained significant (HR = 1.71, 95 % CI: 1.44–2.02, P < 0.001), suggesting the stability of our results. Therefore, our study suggested that survivin overexpression had a poor prognosis value in patients with NSCLC. 相似文献
157.
158.
Biao Cheng Hao Gong Xiaochao Li Yue Sun Hong Chen Xin Zhang Qian Wu Ling Zheng Kun Huang 《Proteins》2013,81(4):613-621
The misfolding of human islet amyloid polypeptide (hIAPP) is regarded as one of the causative factors of type 2 diabetes mellitus (T2DM). Salvia miltiorrhiza (Danshen), one of the most commonly used of traditional Chinese medicines, is often used in Compound Recipes for treating diabetes, however with unclear mechanisms. Since salvianolic acid B (SalB) is the most abundant bioactive ingredient of salvia miltiorrhiza water‐extract. In this study, we tested whether SalB has any effect on the amyloidogenicity of hIAPP. Our results clearly suggest that SalB can significantly inhibit the formation of hIAPP amyloid and disaggregate hIAPP fibrils. Furthermore, photo‐crosslinking based oligomerization studies suggest SalB significantly suppresses the toxic oligomerization of hIAPP monomers. Cytotoxicity protection effects on pancreatic INS‐1 cells by SalB were also observed using MTT‐based assays, potentially due to the inhibition on the membrane disruption effects and attenuated mitochondria impairment induced by hIAPP. These results provide evidence that SalB may further be studied on the possible pharmacological treatment for T2DM. Proteins 2013. © 2012 Wiley Periodicals, Inc. 相似文献
159.
160.