全文获取类型
收费全文 | 239495篇 |
免费 | 154424篇 |
国内免费 | 40408篇 |
出版年
2022年 | 3263篇 |
2021年 | 8662篇 |
2020年 | 6537篇 |
2019年 | 9572篇 |
2018年 | 8900篇 |
2017年 | 7115篇 |
2016年 | 9335篇 |
2015年 | 12816篇 |
2014年 | 15051篇 |
2013年 | 15613篇 |
2012年 | 18839篇 |
2011年 | 17822篇 |
2010年 | 13418篇 |
2009年 | 17089篇 |
2008年 | 13112篇 |
2007年 | 12296篇 |
2006年 | 10277篇 |
2005年 | 8879篇 |
2004年 | 7884篇 |
2003年 | 6932篇 |
2002年 | 6928篇 |
2001年 | 7422篇 |
2000年 | 5028篇 |
1999年 | 9393篇 |
1998年 | 10219篇 |
1997年 | 10391篇 |
1996年 | 9594篇 |
1995年 | 9741篇 |
1994年 | 9158篇 |
1993年 | 8541篇 |
1992年 | 8973篇 |
1991年 | 8781篇 |
1990年 | 9352篇 |
1989年 | 8561篇 |
1988年 | 7715篇 |
1987年 | 6742篇 |
1986年 | 6258篇 |
1985年 | 5656篇 |
1984年 | 4275篇 |
1983年 | 3509篇 |
1982年 | 3747篇 |
1981年 | 3359篇 |
1980年 | 3271篇 |
1979年 | 3417篇 |
1978年 | 3069篇 |
1977年 | 2986篇 |
1976年 | 2820篇 |
1974年 | 2581篇 |
1972年 | 2919篇 |
1971年 | 2662篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
Photosynthesis,Transpiration, and Water Use Efficiency of Vegetative and Reproductive Shoots of Grassland Species from North-Eastern China 总被引:2,自引:0,他引:2
The differences in net photosynthetic rate (P
N), transpiration rate (E), and water use efficiency (WUE) between the vegetative and reproductive shoots of three native grass species from the grassland of northeastern China [grey-green and yellow green populations of Leymus chinensis (Trin.) Tzvel., Puccinellia tenuiflora (Griseb) Scrib & Merr, Puccinellia chinampoensis Ohwi] were compared. The two type shoots experienced similar habitats, but differed in leaf life-span and leaf area. The leaf P
N and WUE for the vegetative shoots were significantly higher than those for the reproductive shoots in the grasses, while their E were remarked lower in the dry season. Relative lower leaf P
N and WUE for the reproductive shoots of grassland grasses may explain the facts of lower seed production and the subordinate role of seed in the grassland renewal in north-eastern China. 相似文献
84.
85.
86.
87.
88.
Zhaolin Wang Cara Fraley Adam R. Mezo 《Bioorganic & medicinal chemistry letters》2013,23(5):1253-1256
The neonatal Fc receptor, FcRn, prolongs the half-life of IgG in the serum and represents a potential therapeutic target for the treatment of autoimmune disease. Small molecules that block the protein–protein interactions of human IgG–human FcRn may lower pathogenic autoantibodies and provide effective treatment. A novel class of quinoxalines has been discovered as antagonists of the IgG:FcRn protein–protein interaction through optimization of a hit derived from a virtual ligand-based screen. 相似文献
89.
Abstract The potentiation of the biological effects of recombinant porcine growth hormone (pGH) by immunologic manipulation was investigated. A monoclonal antibody (mAb), designated PS‐7.6, was raised against pGH and repeatedly shown to enhance the responsiveness of hypophysectomized (hypox) rats to pGH. As a result, animals receiving a combination treatment of pGH and mAb PS‐7.6 together gained significantly more weight than those receiving the same doses of pGH alone. The enhancing action of the mAb was a rapid process and its effective doses ranged from 0.1 to 2 mg/injection. The ability of the antibody to augment the hormonal activity persisted beyond the 5‐day treatment period and the differences in net weight gain between treated and control animals remained significant for 28 days. Results from treatment frequency studies further suggested that pGH when complexed with mAb PS‐7.6 required fewer injections and produced a greater efficacy than being administered alone. Therefore, present findings suggest that mAb PS‐7.6 may prove useful for not only improving the efficiency of pGH, but also developing a novel formulation for sustained pGH release. 相似文献
90.
Bing Xia Haiping Ke Wei Jiang Masayori Inouye 《The Journal of biological chemistry》2002,277(8):6005-6011
The 5'-end region of cspA mRNA contains a Cold Box sequence conserved among several cold-shock mRNAs. This region forms a stable stem-loop structure followed by an AU-rich sequence. Here we show that the Cold Box region is essential for the normal scale of cspA mRNA induction after cold shock because a deletion of the stem-loop significantly destabilizes the mRNA and reduces the cold shock-induced cspA mRNA amount by approximately 50%. The AU-rich track, however, slightly destabilizes the mRNA. The integrity of the stem is essential for the stabilizing function, whereas that of the loop sequence is less important. Overexpression of a mutant cspA mRNA devoid of both the AUG initiation codon and the coding sequence results in a severe growth inhibition at low temperature along with a derepression of the chromosomal cspA expression. Furthermore, the overexpressed RNA is stably associated with the 30 S and 70 S ribosomes. Our results demonstrate that the AUG initiation codon and the coding region containing the downstream box are not required for cspA mRNA to bind ribosomes and that the 5'-untranslated region by itself has a remarkable affinity to ribosomes at low temperature. 相似文献