全文获取类型
收费全文 | 35652篇 |
免费 | 3236篇 |
国内免费 | 5262篇 |
专业分类
44150篇 |
出版年
2024年 | 123篇 |
2023年 | 507篇 |
2022年 | 1180篇 |
2021年 | 1885篇 |
2020年 | 1368篇 |
2019年 | 1747篇 |
2018年 | 1591篇 |
2017年 | 1230篇 |
2016年 | 1668篇 |
2015年 | 2424篇 |
2014年 | 2927篇 |
2013年 | 3025篇 |
2012年 | 3634篇 |
2011年 | 3294篇 |
2010年 | 2112篇 |
2009年 | 1877篇 |
2008年 | 2104篇 |
2007年 | 1890篇 |
2006年 | 1652篇 |
2005年 | 1351篇 |
2004年 | 1105篇 |
2003年 | 1037篇 |
2002年 | 871篇 |
2001年 | 547篇 |
2000年 | 474篇 |
1999年 | 437篇 |
1998年 | 286篇 |
1997年 | 259篇 |
1996年 | 233篇 |
1995年 | 183篇 |
1994年 | 181篇 |
1993年 | 123篇 |
1992年 | 135篇 |
1991年 | 106篇 |
1990年 | 78篇 |
1989年 | 76篇 |
1988年 | 61篇 |
1987年 | 40篇 |
1986年 | 51篇 |
1985年 | 60篇 |
1984年 | 23篇 |
1983年 | 29篇 |
1982年 | 29篇 |
1981年 | 23篇 |
1980年 | 10篇 |
1979年 | 20篇 |
1978年 | 9篇 |
1974年 | 8篇 |
1973年 | 11篇 |
1971年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
SPOP Promotes Nanog Destruction to Suppress Stem Cell Traits and Prostate Cancer Progression 总被引:1,自引:0,他引:1
82.
Jafar A. Mammadov Wei Chen Ruihua Ren Reetal Pai Wesley Marchione Feyruz Yalçin Hanneke Witsenboer Thomas W. Greene Steven A. Thompson Siva P. Kumpatla 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2010,121(3):577-588
The duplicated and the highly repetitive nature of the maize genome has historically impeded the development of true single
nucleotide polymorphism (SNP) markers in this crop. Recent advances in genome complexity reduction methods coupled with sequencing-by-synthesis
technologies permit the implementation of efficient genome-wide SNP discovery in maize. In this study, we have applied Complexity
Reduction of Polymorphic Sequences technology (Keygene N.V., Wageningen, The Netherlands) for the identification of informative
SNPs between two genetically distinct maize inbred lines of North and South American origins. This approach resulted in the
discovery of 1,123 putative SNPs representing low and single copy loci. In silico and experimental (Illumina GoldenGate (GG)
assay) validation of putative SNPs resulted in mapping of 604 markers, out of which 188 SNPs represented 43 haplotype blocks
distributed across all ten chromosomes. We have determined and clearly stated a specific combination of stringent criteria
(>0.3 minor allele frequency, >0.8 GenTrainScore and >0.5 Chi_test100 score) necessary for the identification of highly polymorphic
and genetically stable SNP markers. Due to these criteria, we identified a subset of 120 high-quality SNP markers to leverage
in GG assay-based marker-assisted selection projects. A total of 32 high-quality SNPs represented 21 haplotypes out of 43
identified in this study. The information on the selection criteria of highly polymorphic SNPs in a complex genome such as
maize and the public availability of these SNP assays will be of great value for the maize molecular genetics and breeding
community. 相似文献
83.
Combinatorial signals of activin/nodal and bone morphogenic protein regulate the early lineage segregation of human embryonic stem cells 总被引:2,自引:0,他引:2
Wu Z Zhang W Chen G Cheng L Liao J Jia N Gao Y Dai H Yuan J Cheng L Xiao L 《The Journal of biological chemistry》2008,283(36):24991-25002
Cell fate commitment of pre-implantation blastocysts, to either the inner cell mass or trophoblast, is the first step in cell lineage segregation of the developing human embryo. However, the intercellular signals that control fate determination of these cells remain obscure. Human embryonic stem cells (hESCs) provide a unique model for studying human early embryonic development. We have previously shown that Activin/Nodal signaling contributes to maintaining pluripotency of hESCs, which are derivatives of the inner cell mass. Here we further demonstrate that the inhibition of Activin/Nodal signaling results in the loss of hESC pluripotency and trophoblast differentiation, similar to BMP4-induced trophoblast differentiation from hESCs. We also show that the trophoblast induction effect of BMP4 correlates with and depends on the inhibition of Activin/Nodal signaling. However, the activation of BMP signaling is still required for trophoblast differentiation when Activin/Nodal signaling is inhibited. These data reveal that the early lineage segregation of hESCs is determined by the combinatorial signals of Activin/Nodal and BMP. 相似文献
84.
85.
Inhibition of mitochondrial complex I improves glucose metabolism independently of AMPK activation 下载免费PDF全文
Wo‐Lin Hou Jun Yin Miriayi Alimujiang Xue‐Ying Yu Li‐Gen Ai Yu‐qian Bao Fang Liu Wei‐Ping Jia 《Journal of cellular and molecular medicine》2018,22(2):1316-1328
Accumulating evidences showed metformin and berberine, well‐known glucose‐lowering agents, were able to inhibit mitochondrial electron transport chain at complex I. In this study, we aimed to explore the antihyperglycaemic effect of complex I inhibition. Rotenone, amobarbital and gene silence of NDUFA13 were used to inhibit complex I. Intraperitoneal glucose tolerance test and insulin tolerance test were performed in db/db mice. Lactate release and glucose consumption were measured to investigate glucose metabolism in HepG2 hepatocytes and C2C12 myotubes. Glucose output was measured in primary hepatocytes. Compound C and adenoviruses expressing dominant negative AMP‐activated protein kinase (AMPK) α1/2 were exploited to inactivate AMPK pathway. Cellular NAD+/NADH ratio was assayed to evaluate energy transforming and redox state. Rotenone ameliorated hyperglycaemia and insulin resistance in db/db mice. It induced glucose consumption and glycolysis and reduced hepatic glucose output. Rotenone also activated AMPK. Furthermore, it remained effective with AMPK inactivation. The enhanced glycolysis and repressed gluconeogenesis correlated with a reduction in cellular NAD+/NADH ratio, which resulted from complex I suppression. Amobarbital, another representative complex I inhibitor, stimulated glucose consumption and decreased hepatic glucose output in vitro, too. Similar changes were observed while expression of NDUFA13, a subunit of complex I, was knocked down with gene silencing. These findings reveal mitochondrial complex I emerges as a key drug target for diabetes treatment. Inhibition of complex I improves glucose homoeostasis via non‐AMPK pathway, which may relate to the suppression of the cellular NAD+/NADH ratio. 相似文献
86.
千山油松年轮宽度年表的建立及其与气候的关系 总被引:5,自引:0,他引:5
以千山油松为样本,建立了年轮宽度标准化年表、差值年表和自回归年表.结果表明,油松年轮宽度与5—7和9—11月温度指标的相关性较高,且与低温呈正相关,其中与7月的极端最低温、9月的平均最低温显著相关.3种年表与上年12月和当年1月的极端最低温、1月的平均最低温呈显著相关,且其与全年、上年12月、当年5月的降水量显著相关,与4月的降水量极显著相关.油松与水汽压、相对湿度的月和年指标均有较强的相关性.蒸发的年指标和绝大部分月指标对油松生长具有负效应,其中4—7月最明显.油松年表的窄化突变佐证了1800年以来的30次主要的旱灾年历史记录.千山油松的生长受全球或半球尺度气候变化的影响.年表与太阳活动存在显著的11、23和50年左右的公共周期,与地磁指标在10、20和45年左右存在共同的周期变化. 相似文献
87.
西藏中部退化土壤在不同培肥措施下的肥力特征 总被引:1,自引:1,他引:1
于西藏中部春播条件下就不同培肥方式对退化土壤物理、化学和生物性质的影响以及土壤肥力因子间的相互关系进行了研究。结果表明 ,化肥、有机肥 ,特别是有机 -无机肥配合施用在协调土壤环境 ,促进以细菌为主导的土壤微生物繁殖以及土壤有机质、土壤团粒结构形成和土壤养分转化等方面具有重要作用 ;退化土壤物理、化学和生物性质呈现出变化特征的相对一致性 ,并在总体上呈现出较为明显的恢复态势 ,突出地反映了高原高寒以及干旱、半干旱条件下退化土壤所具有的在相对较短的时间内实现肥力恢复及结构重建的可能性及其潜力。石灰性土壤条件下 ,耕层土壤有机质以及不同土层全氮、有效氮、全磷、有效磷的绝对增长量较大。同时 ,不同培肥方式对不同土层土壤真菌、固氮菌以及耕层土壤放线菌的繁殖普遍具有不同程度的抑制作用 ;不同土层土壤固氮菌与纤维素分解菌均呈负相关。 相似文献
88.
89.
Loren P. Albert Natalia Restrepo‐Coupe Marielle N. Smith Jin Wu Cecilia Chavana‐Bryant Neill Prohaska Tyeen C. Taylor Giordane A. Martins Philippe Ciais Jiafu Mao M. Altaf Arain Wei Li Xiaoying Shi Daniel M. Ricciuto Travis E. Huxman Sean M. McMahon Scott R. Saleska 《Global Change Biology》2019,25(11):3591-3608
Plant phenology—the timing of cyclic or recurrent biological events in plants—offers insight into the ecology, evolution, and seasonality of plant‐mediated ecosystem processes. Traditionally studied phenologies are readily apparent, such as flowering events, germination timing, and season‐initiating budbreak. However, a broad range of phenologies that are fundamental to the ecology and evolution of plants, and to global biogeochemical cycles and climate change predictions, have been neglected because they are “cryptic”—that is, hidden from view (e.g., root production) or difficult to distinguish and interpret based on common measurements at typical scales of examination (e.g., leaf turnover in evergreen forests). We illustrate how capturing cryptic phenology can advance scientific understanding with two case studies: wood phenology in a deciduous forest of the northeastern USA and leaf phenology in tropical evergreen forests of Amazonia. Drawing on these case studies and other literature, we argue that conceptualizing and characterizing cryptic plant phenology is needed for understanding and accurate prediction at many scales from organisms to ecosystems. We recommend avenues of empirical and modeling research to accelerate discovery of cryptic phenological patterns, to understand their causes and consequences, and to represent these processes in terrestrial biosphere models. 相似文献
90.
基于人抗菌肽VIP(Vasoactive intestinal peptide)基因序列,按照毕赤酵母密码子偏好性设计引物;用SOE-PCR法扩增目的基因;然后将目的基因克隆至毕赤酵母分泌型表达载体pPICZαA上,构建VIP分泌表达菌株GS115-p PICZαA-vip。用甲醇诱导96 h收集上清,用质谱进行鉴定,结果显示分泌表达产物与人抗菌肽VIP理论值(3 326.82 Da)完全一致,表明人抗菌肽VIP成功得到分泌表达。琼脂糖凝胶扩散法实验结果显示,重组VIP对大肠杆菌Escherichia coli ATCC25922和金黄色葡萄球菌Staphylococcus aureus ATCC25923都有很强的抗菌活性,MIC(Minimal inhibitory concentration)分别为8 mmol/L和16 mmol/L。进一步细胞毒性和溶血性实验结果显示,重组VIP对正常细胞NCM460和IPEC-J2没有毒性,其对SD大鼠红细胞不具有溶血活性。通过透射电镜观察了VIP的抗菌机制,结果显示VIP主要通过破坏细胞膜的方式抑杀细菌。本研究为人抗菌肽VIP的开发应用和大量生产奠定了基础。 相似文献