全文获取类型
收费全文 | 9523篇 |
免费 | 880篇 |
国内免费 | 5篇 |
出版年
2022年 | 66篇 |
2021年 | 148篇 |
2020年 | 83篇 |
2019年 | 120篇 |
2018年 | 118篇 |
2017年 | 116篇 |
2016年 | 215篇 |
2015年 | 399篇 |
2014年 | 404篇 |
2013年 | 459篇 |
2012年 | 614篇 |
2011年 | 559篇 |
2010年 | 367篇 |
2009年 | 358篇 |
2008年 | 477篇 |
2007年 | 506篇 |
2006年 | 470篇 |
2005年 | 473篇 |
2004年 | 424篇 |
2003年 | 396篇 |
2002年 | 381篇 |
2001年 | 199篇 |
2000年 | 138篇 |
1999年 | 154篇 |
1998年 | 104篇 |
1997年 | 89篇 |
1996年 | 77篇 |
1995年 | 94篇 |
1994年 | 69篇 |
1993年 | 66篇 |
1992年 | 100篇 |
1991年 | 85篇 |
1990年 | 91篇 |
1989年 | 87篇 |
1988年 | 72篇 |
1987年 | 103篇 |
1986年 | 77篇 |
1985年 | 89篇 |
1984年 | 100篇 |
1983年 | 60篇 |
1982年 | 84篇 |
1981年 | 65篇 |
1980年 | 61篇 |
1979年 | 81篇 |
1978年 | 59篇 |
1976年 | 63篇 |
1975年 | 52篇 |
1974年 | 67篇 |
1973年 | 55篇 |
1972年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Shallow-water vegetated estuarine habitats, notably seagrass, mangrove and saltmarsh, are known to be important habitats for
many species of small or juvenile fish in temperate Australia. However, the movement of fish between these habitats is poorly
understood, and yet critical to the management of the estuarine fisheries resource. We installed a series of buoyant pop nets
in adjacent stands of seagrass, mangrove and saltmarsh in order to determine how relative abundance of fishes varied through
lunar cycles. Nets were released in all habitats at the peak of the monthly spring tide for 12 months, and in the seagrass
habitat at the peak of the neap tide also. The assemblage of fish in each habitat differed during the spring tides. The seagrass
assemblage differed between spring and neap tide, with the neap tide assemblage showing greater abundances of fish, particularly
those species which visited the adjacent habitats when inundated during spring tides. The result supports the hypothesis that
fish move from the seagrass to the adjacent mangrove and saltmarsh during spring tides, taking advantage of high abundances
of zooplankton, and use seagrass as a refuge during lower tides. The restoration and preservation of mangrove and saltmarsh
utility as fish habitat may in some situations be linked to the proximity of available seagrass. 相似文献
23.
Longitudinal studies of the rhesus monkey reveal a syndrome of diabetes mellitus in those that become middle-aged and obese. The sequence of events in the development of the disease progresses from normoinsulinemia with normoglycemia through stages of hyperinsulinemia followed by below normal insulin levels with hyperglycemia and glycosuria. We believe the rhesus to be an excellent nonhuman primate model for maturity-onset diabetes in humans. 相似文献
24.
Edward Hamilton 《BMJ (Clinical research ed.)》1890,2(1559):1149-1150
25.
26.
Zhenbo Cao Suraj Subramaniam Neil J. Bulleid 《The Journal of biological chemistry》2014,289(9):5490-5498
Typical 2-Cys peroxiredoxins are required to remove hydrogen peroxide from several different cellular compartments. Their activity can be regulated by hyperoxidation and consequent inactivation of the active-site peroxidatic cysteine. Here we developed a simple assay to quantify the hyperoxidation of peroxiredoxins. Hyperoxidation of peroxiredoxins can only occur efficiently in the presence of a recycling system, usually involving thioredoxin and thioredoxin reductase. We demonstrate that there is a marked difference in the sensitivity of the endoplasmic reticulum-localized peroxiredoxin to hyperoxidation compared with either the cytosolic or mitochondrial enzymes. Each enzyme is equally sensitive to hyperoxidation in the presence of a robust recycling system. Our results demonstrate that peroxiredoxin IV recycling in the endoplasmic reticulum is much less efficient than in the cytosol or mitochondria, leading to the protection of peroxiredoxin IV from hyperoxidation. 相似文献
27.
28.
Neil E. Klepeis Suzanne C. Hughes Rufus D. Edwards Tracy Allen Michael Johnson Zohir Chowdhury Kirk R. Smith Marie Boman-Davis John Bellettiere Melbourne F. Hovell 《PloS one》2013,8(8)
Interventions are needed to protect the health of children who live with smokers. We pilot-tested a real-time intervention for promoting behavior change in homes that reduces second hand tobacco smoke (SHS) levels. The intervention uses a monitor and feedback system to provide immediate auditory and visual signals triggered at defined thresholds of fine particle concentration. Dynamic graphs of real-time particle levels are also shown on a computer screen. We experimentally evaluated the system, field-tested it in homes with smokers, and conducted focus groups to obtain general opinions. Laboratory tests of the monitor demonstrated SHS sensitivity, stability, precision equivalent to at least 1 µg/m3, and low noise. A linear relationship (R2 = 0.98) was observed between the monitor and average SHS mass concentrations up to 150 µg/m3. Focus groups and interviews with intervention participants showed in-home use to be acceptable and feasible. The intervention was evaluated in 3 homes with combined baseline and intervention periods lasting 9 to 15 full days. Two families modified their behavior by opening windows or doors, smoking outdoors, or smoking less. We observed evidence of lower SHS levels in these homes. The remaining household voiced reluctance to changing their smoking activity and did not exhibit lower SHS levels in main smoking areas or clear behavior change; however, family members expressed receptivity to smoking outdoors. This study established the feasibility of the real-time intervention, laying the groundwork for controlled trials with larger sample sizes. Visual and auditory cues may prompt family members to take immediate action to reduce SHS levels. Dynamic graphs of SHS levels may help families make decisions about specific mitigation approaches. 相似文献
29.
30.