全文获取类型
收费全文 | 10798篇 |
免费 | 906篇 |
国内免费 | 1018篇 |
出版年
2024年 | 22篇 |
2023年 | 170篇 |
2022年 | 222篇 |
2021年 | 661篇 |
2020年 | 480篇 |
2019年 | 524篇 |
2018年 | 517篇 |
2017年 | 353篇 |
2016年 | 500篇 |
2015年 | 760篇 |
2014年 | 819篇 |
2013年 | 887篇 |
2012年 | 997篇 |
2011年 | 863篇 |
2010年 | 565篇 |
2009年 | 464篇 |
2008年 | 568篇 |
2007年 | 490篇 |
2006年 | 423篇 |
2005年 | 335篇 |
2004年 | 280篇 |
2003年 | 256篇 |
2002年 | 191篇 |
2001年 | 175篇 |
2000年 | 151篇 |
1999年 | 168篇 |
1998年 | 91篇 |
1997年 | 84篇 |
1996年 | 75篇 |
1995年 | 75篇 |
1994年 | 94篇 |
1993年 | 48篇 |
1992年 | 52篇 |
1991年 | 69篇 |
1990年 | 42篇 |
1989年 | 48篇 |
1988年 | 32篇 |
1987年 | 26篇 |
1986年 | 34篇 |
1985年 | 25篇 |
1984年 | 16篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1978年 | 4篇 |
1973年 | 4篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1968年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
101.
102.
103.
104.
Bao Yang Jianwu Li Jiayu Yan Ke Zhang Zhewen Ouyang Yefei Lu Huili Wei Qing Li Xuan Yao Shaoping Lu Yueyun Hong Xuemin Wang Liang Guo 《植物学报(英文版)》2023,65(11):2421-2436
Phosphorus is a major nutrient vital for plant growth and development, with a substantial amount of cellular phosphorus being used for the biosynthesis of membrane phospholipids. Here, we report that NON-SPECIFIC PHOSPHOLIPASE C4 (NPC4) in rapeseed (Brassica napus) releases phosphate from phospholipids to promote growth and seed yield, as plants with altered NPC4 levels showed significant changes in seed production under different phosphate conditions. Clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated nuclease 9 (Cas9)-mediated knockout of BnaNPC4 led to elevated accumulation of phospholipids and decreased growth, whereas overexpression (OE) of BnaNPC4 resulted in lower phospholipid contents and increased plant growth and seed production. We demonstrate that BnaNPC4 hydrolyzes phosphosphingolipids and phosphoglycerolipids in vitro, and plants with altered BnaNPC4 function displayed changes in their sphingolipid and glycerolipid contents in roots, with a greater change in glycerolipids than sphingolipids in leaves, particularly under phosphate deficiency conditions. In addition, BnaNPC4-OE plants led to the upregulation of genes involved in lipid metabolism, phosphate release, and phosphate transport and an increase in free inorganic phosphate in leaves. These results indicate that BnaNPC4 hydrolyzes phosphosphingolipids and phosphoglycerolipids in rapeseed to enhance phosphate release from membrane phospholipids and promote growth and seed production. 相似文献
105.
通过分析珍稀濒危植物峨眉含笑(Michelia wilsonii)种子与果实的表型性状特征,研究其变异规律和空间自相关性,为峨眉含笑天然种群的保护利用工作提供依据。以雅安周公山的峨眉含笑为研究对象,测定12项种实表型性状指标,采用变异系数和半方差函数,探究峨眉含笑种实的空间变异特征。结果显示:(1)峨眉含笑种实表型性状的平均变异系数为27.59%,种实的形态变异程度最小,种子性状的变异程度比果实性状更为丰富。(2)聚合果下部的种子败育率与蓇葖败育率最高,分别为18.32%和38.22%;中部的败育率最低,分别为15.05%和23.45%。(3)半方差函数模型以指数和球状模型为主,呈聚集分布。除果实长、种子纵径和种子败育率外,其余9项指标具有中高等强度的空间自相关性。(4)9项指标的各向异性比接近于1,空间异质性表现为各向同性。因此,峨眉含笑种实表型性状在中等尺度的空间范围内具有丰富的变异性。 相似文献
106.
Shao-Jun Ling Xiao-Lan Yao Juli Caujapé-Castells Jordi López-Pujol Ke Tan Ming-Xun Ren 《植物分类学报:英文版》2023,61(6):1020-1035
Disjunct distribution is a key issue in biogeography and ecology, but it is often difficult to determine the relative roles of dispersal vs. vicariance in disjunctions. We studied the phylogeographic pattern of the monotypic Conandron ramondioides (Gesneriaceae), which shows Sino-Japanese disjunctions, with ddRAD sequencing based on a comprehensive sampling of 11 populations from mainland China, Taiwan Island, and Japan. We found a very high degree of genetic differentiation among these three regions, with very limited gene flow and a clear Isolation by Distance pattern. Mainland China and Japan clades diverged first from a widespread ancestral population in the middle Miocene, followed by a later divergence between mainland China and Taiwan Island clades in the early Pliocene. Three current groups have survived in various glacial refugia during the Last Glacial Maximum, and experienced contraction and/or bottlenecks since their divergence during Quaternary glacial cycles, with strong niche divergence between mainland China + Japan and Taiwan Island ranges. Thus, we verified a predominant role of vicariance in the current disjunction of the monotypic genus Conandron. The sharp phylogenetic separation, ecological niche divergence among these three groups, and the great number of private alleles in all populations sampled indicated a considerable time of independent evolution, and suggests the need for a taxonomic survey to detect potentially overlooked taxa. 相似文献
107.
Teng Man Zhu Zhi-Jian Yao Yongxiu Nair Venugopal Zhang Gai-Ping Luo Jun 《中国科学:生命科学英文版》2023,66(2):251-268
Science China Life Sciences - Over the past two decades, numerous non-coding RNAs (ncRNAs) have been identified in different biological systems including virology, especially in large DNA viruses... 相似文献
108.
P P Yao Y W Li Y Z Ding F He 《Journal of hygiene, epidemiology, microbiology, and immunology》1992,36(1):31-36
Using HPLC, the authors had investigated the three metabolites of deltamethrin (DM) in the urine of spraymen and one suicide, namely: dibromovinyl-dimethylcyclopropane carboxylic acid (Br2A), 3-phenoxybenzyl-hydroxy-ethyl acetate (PHE) and 3-phenoxyl-benzoic acid (BA). Br2A was chosen as the biological monitoring parameter for DM exposed people, and the urine samples of one suicide and 11 farmers sprayed DM or DM plus methamidophos were examined for Br2A quantitatively which was detected in 8 of 11 sprayers and in the suicide case. 相似文献
109.
110.
以小米(Setaria italica)为材料,克隆了含有叶绿体psbA基因的2.2kb EcoRⅠ片段,测定了该基因5'末端非编码区的核苷酸序列。序列分析显示psbA基因5'末端非编码区存在着与原核类似的启动子结构,其“-10”区的序列为TATACT,与原核生物“-10”共有基序(Consensus motif)仅相差一个核苷酸;其“-35”区的序列为TTGACA,与原核生物“-35”共有基序完全相同。另外,在“-10”区和“-35”区之间还存在着一个类似真核启动子结构的“TATATA”保守序列。这些结果表明小米psbA基因的启动子既具有原核的特征又具有真核的特征。小米psbA基因的mRNA前导序列长87bp,与高粱完全一致,而比水稻多出了“CTATTTT”7个核苷酸,比小麦、大麦和黑麦多出了“TTTT”4个核苷酸。因此推测在禾本科的C_3和C_4植物之间,psbA基因mRNA前导序列区的差异可能具有普遍性。计算机分析结果显示,以上6种植物的psbA基因mRNA前导序列区内均能形成小的茎环结构,而且这段“CTATTTT”额外序列恰好位于茎环结构中,造成了6种植物间茎环大小的差异。这一小的二级结构可能对psbA基因的表达调控有一定的影响。 相似文献