全文获取类型
收费全文 | 9702篇 |
免费 | 873篇 |
国内免费 | 7篇 |
出版年
2021年 | 126篇 |
2020年 | 93篇 |
2019年 | 86篇 |
2018年 | 134篇 |
2017年 | 117篇 |
2016年 | 192篇 |
2015年 | 288篇 |
2014年 | 378篇 |
2013年 | 508篇 |
2012年 | 497篇 |
2011年 | 548篇 |
2010年 | 385篇 |
2009年 | 346篇 |
2008年 | 496篇 |
2007年 | 511篇 |
2006年 | 462篇 |
2005年 | 474篇 |
2004年 | 425篇 |
2003年 | 405篇 |
2002年 | 434篇 |
2001年 | 191篇 |
2000年 | 169篇 |
1999年 | 178篇 |
1998年 | 159篇 |
1997年 | 132篇 |
1996年 | 128篇 |
1995年 | 112篇 |
1994年 | 109篇 |
1993年 | 108篇 |
1992年 | 118篇 |
1991年 | 139篇 |
1990年 | 116篇 |
1989年 | 125篇 |
1988年 | 110篇 |
1987年 | 93篇 |
1986年 | 97篇 |
1985年 | 90篇 |
1984年 | 82篇 |
1983年 | 69篇 |
1982年 | 87篇 |
1981年 | 78篇 |
1980年 | 71篇 |
1979年 | 66篇 |
1978年 | 61篇 |
1977年 | 56篇 |
1976年 | 53篇 |
1975年 | 73篇 |
1974年 | 78篇 |
1972年 | 50篇 |
1971年 | 59篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
1.
2.
Nathalie Le Floc'h Céline Deblanc Roland Cariolet Anne V. Gautier-Bouchardon Elodie Merlot Ga?lle Simon 《PloS one》2014,9(8)
As nutritional status and inflammation are strongly connected, feeding and nutritional strategies could be effective to improve the ability of pigs to cope with disease. The aims of this study were to investigate the impact of a feed restriction on the ability of pigs to resist and be tolerant to a coinfection with Mycoplasma hyopneumoniae (Mhp) and the European H1N1 swine influenza virus, and the consequences for nutrient metabolism, with a focus on amino acids. Two groups of specific pathogen-free pigs were inoculated with Mhp and H1N1 21 days apart. One group was fed ad libitum, the other group was subjected to a two-week 40% feed restriction starting one week before H1N1 infection. The two respective mock control groups were included. Three days post-H1N1 infection, 200 g of feed was given to pigs previously fasted overnight and serial blood samples were taken over 4 hours to measure plasma nutrient concentrations. Throughout the study, clinical signs were observed and pathogens were detected in nasal swabs and lung tissues. Feed-restricted pigs presented shorter hyperthermia and a positive mean weight gain over the 3 days post-H1N1 infection whereas animals fed ad libitum lost weight. Both infection and feed restriction reduced postprandial glucose concentrations, indicating changes in glucose metabolism. Post-prandial plasma concentrations of the essential amino acids histidine, arginine and threonine were lower in co-infected pigs suggesting a greater use of those amino acids for metabolic purposes associated with the immune response. Altogether, these results indicate that modifying feeding practices could help to prepare animals to overcome an influenza infection. Connections with metabolism changes are discussed. 相似文献
3.
James F. Richards Kulgite Lit Roland Fuca Catherine Bourgeault 《Biochemical and biophysical research communications》1981,99(4):1461-1467
Several species of ornithine decarboxylase were separated by chromatography of rat thymus and kidney extracts on DEAE-Sepharose CL-6B. One major and one minor species were absent from thymus of rats two hours after hormone treatment but otherwise, the elution profile was identical to thymus from control animals. The elution patterns of ODC activity in kidneys of rats treated 2.5 or 5 hours before sacrifice with dexamethasone differ from that of control kidney and from each other. Enzyme from kidneys early after hormone treatment is eluted earlier than enzyme from control tissue, while at 5 hours, the enzyme is eluted much later than in the control. This suggests that the hormone-induced activity is subsequently modified. 相似文献
4.
R.J. Ulvik I. Romslo F. Roland R.R. Crichton 《Biochimica et Biophysica Acta (BBA)/General Subjects》1981,677(1):50-56
Mitochondria mobilize iron from ferritin by a mechanism that depends on external FMN. With rat liver mitochondria, the rate of mobilization of iron is higher from rat liver ferritin than from horse spleen ferritin. With horse liver mitochondria, the rate of iron mobilization is higher from horse spleen ferritin than from rat liver ferritin. The results are explained by a higher affinity between mitochondria and ferritins of the same species. The mobilization of iron increases with the iron content of the ferritin and then levels off. A maximum is reached with ferritins containing about 1 200 iron atoms per molecule. The results represent further evidence that ferritin may function as a direct iron donor to the mitochondria. 相似文献
5.
The morphology and innervation of the six oculomotor muscles in the gobiid fishTridentiger trigonocephalus are described. Every rectus muscle is composed of two types of muscle fibres. Muscles attach onto the cartilaginous or fibrous
sclerotica. Oblique muscles attach onto the ethmoidal plate; recti muscles attach onto the parasphenoid or a thick fibrous
membrane. There is no myodome. The common oculomotor nerve is composed of four bundles, the trochlear and the externus of
two. The two kinds of fibres of the lateral rectus and the two distinct bundles of the nerve VI suggest a possible homology
between this muscle in fishes and the lateral rectus+retractor bulbi in mammals. 相似文献
6.
Edward Harrison 《BMJ (Clinical research ed.)》1916,1(2888):645-647
7.
8.
Robert Blake II Elizabeth A. Shute James Waskovsky Arthur P. Harrison JR. 《Geomicrobiology journal》2013,30(3-4):173-192
Abstract Microorganisms capable of aerobic respiration on ferrous ions are spread throughout eubacterial and archaebacterial phyla. Phylogenetically distinct organisms were shown to express spectrally distinct redox‐active biomolecules during autotrophic growth on soluble iron. A new iron‐oxidizing eubacterium, designated as strain Funis, was investigated. Strain Funis was judged to be different from other known iron‐oxidizing bacteria on the bases of comparative lipid analyses, 16S rRNA sequence analyses, and cytochrome composition studies. When grown autotrophically on ferrous ions, Funis produced conspicuous levels of a novel acid‐stable, acid‐soluble yellow cytochrome with a distinctive absorbance peak at 579 nm in the reduced state. Stopped‐flow spectrophotometric kinetic studies were conducted on respiratory chain components isolated from cell‐free extracts of Thiobacillus ferrooxidans. Experimental results were consistent with a model where the primary oxidant of ferrous ions is a highly aggregated c‐type cytochrome that then reduces the periplasmic rusticyanin. The Fe(II)‐dependent, cytochrome c‐catalyzed reduction of the rusticyanin possessed three kinetic properties in common with corresponding intact cells that respire on iron: the same anion specificity, a similar dependence of the rate on the concentration of ferrous ions, and similar rates at saturating concentrations of ferrous ions 相似文献
9.
10.