全文获取类型
收费全文 | 260912篇 |
免费 | 23703篇 |
国内免费 | 1439篇 |
出版年
2021年 | 2751篇 |
2019年 | 2341篇 |
2018年 | 3389篇 |
2017年 | 3128篇 |
2016年 | 4206篇 |
2015年 | 4677篇 |
2014年 | 5840篇 |
2013年 | 7942篇 |
2012年 | 8690篇 |
2011年 | 9242篇 |
2010年 | 6194篇 |
2009年 | 5519篇 |
2008年 | 7698篇 |
2007年 | 7775篇 |
2006年 | 7263篇 |
2005年 | 6896篇 |
2004年 | 6717篇 |
2003年 | 6501篇 |
2002年 | 6270篇 |
2001年 | 12234篇 |
2000年 | 12165篇 |
1999年 | 9358篇 |
1998年 | 2825篇 |
1997年 | 2871篇 |
1996年 | 2810篇 |
1995年 | 2582篇 |
1994年 | 2524篇 |
1993年 | 2401篇 |
1992年 | 7270篇 |
1991年 | 7069篇 |
1990年 | 7106篇 |
1989年 | 6895篇 |
1988年 | 6395篇 |
1987年 | 6040篇 |
1986年 | 5375篇 |
1985年 | 5688篇 |
1984年 | 4485篇 |
1983年 | 3876篇 |
1982年 | 2675篇 |
1981年 | 2497篇 |
1979年 | 4110篇 |
1978年 | 3134篇 |
1977年 | 2881篇 |
1976年 | 2826篇 |
1975年 | 3268篇 |
1974年 | 3496篇 |
1973年 | 3524篇 |
1972年 | 3058篇 |
1971年 | 2842篇 |
1970年 | 2530篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
962.
963.
964.
965.
Summary A local isolate of Bacillus thuringiensis (B.t.81) produced crystal protein which was identified as a cry I gene of Class I. The synthesis and assembly of crystal complements were investigated at intervals throughout the growth cycle. Incubation temperature had a marked effect on toxin synthesis; production being the highest at 25°C and the lowest at 42°C. The mutants of B. t. 81, unable to synthesize crystal protein complements, have also been described. 相似文献
966.
967.
968.
N. Maaranen C. Stantis A. Kharobi S. Zakrzewski H. Schutkowski C. Doumet-Serhal 《American journal of physical anthropology》2023,182(3):428-439
Objectives
The Levantine Middle Bronze Age (MBA, circa 2000–1500 BCE) marks a period of increased trade and regional interaction, spurred on by technological developments. In light of previous research exhibiting limited mobility in Sidon, further investigation was conducted using biodistance analysis to understand local population history and site development.Materials and Methods
Dental nonmetric traits, a proxy for genetic information, were explored using ASUDAS on a sub-sample of primary inhumations (n = 35). The biodistance matrix was generated using Gower distance measures, and further tested using PERMDISP, PERMANOVA, Mantel test and hierarchical cluster analysis. The data was also contrasted to 87Sr/86Sr and δ18O as well as δ13C and δ15N values.Results
There were no significant diachronic differences in isotopes values, and there was biological continuity (n = 35, Mantel test r = 0.11, p = 0.02, comparing local phases and biodistance). The analysis also suggested of a sub-group of individuals with biological proximity shared a more limited range of mobility and dietary habits.Conclusions
The isotopes (87Sr/86Sr, δ18O, δ13C, δ15N) and biodistance analysis conducted on the Sidon College site skeletal assemblage exhibits stability and continuity of the people, despite the site's increasing role in the maritime network. This continuity may have been a key factor in Sidon's success, allowing it to accumulate wealth and resources for centuries to come.969.
Xingyu Zhu Qianqian Gao Genhua Zhao Heng Wang Ling Liu Zhipeng Chen Yijun Chen Li Wu Zisheng Xu Weidong Li 《Biological trace element research》2018,184(1):136-147
To evaluate and compare the effect of raw and processed pyritum on tibial defect healing, 32 male Sprague Dawley rats were randomly divided into four groups. After tibial defect, animals were produced and grouped: sham and control group were orally administrated with distilled water (1 mL/100 g), while treatment groups were given aqueous extracts of raw and processed pyritum (1.5 g/kg) for successive 42 days. Radiographic examination showed that bone defect healing effect of the treatment groups was obviously superior compared to that of the control group. Bone mineral density of whole tibia was increased significantly after treating with pyritum. Inductively coupled plasma-optical emission spectrometry showed that the contents of Ca, P, and Mg in callus significantly increased in the treatment groups comparing with the control. Moreover, serological analysis showed that the concentration of serum phosphorus of the treatment groups significantly increased compared with that of the control group. By in vitro study, we have evaluated the effects of drug-containing serum of raw and processed pyritum on osteoblasts. It was manifested that both the drug-containing sera of raw and processed pyritum significantly increased the mRNA levels of alkaline phosphatase and collagen type I. Protein levels of phosphorylated Smad2/3 also increased. The mRNA levels of osteocalcin and transforming growth factor β (TGF-β) type I and II receptors, as well as the protein levels of TGF-β1 in the processed groups, were higher than those in the control. In summary, both raw and processed pyritum-containing sera exhibited positive effects on osteoblasts, which maybe via the TGF-β1/Smad signaling pathway. Notably, the tibia defect healing effect of pyritum was significantly enhanced after processing. 相似文献
970.
Short peptide domains target proteins to plant vacuoles. 总被引:18,自引:0,他引:18