全文获取类型
收费全文 | 4093篇 |
免费 | 416篇 |
国内免费 | 1篇 |
出版年
2023年 | 22篇 |
2022年 | 27篇 |
2021年 | 64篇 |
2020年 | 45篇 |
2019年 | 53篇 |
2018年 | 53篇 |
2017年 | 60篇 |
2016年 | 102篇 |
2015年 | 153篇 |
2014年 | 185篇 |
2013年 | 207篇 |
2012年 | 286篇 |
2011年 | 270篇 |
2010年 | 178篇 |
2009年 | 144篇 |
2008年 | 219篇 |
2007年 | 245篇 |
2006年 | 202篇 |
2005年 | 211篇 |
2004年 | 177篇 |
2003年 | 163篇 |
2002年 | 181篇 |
2001年 | 83篇 |
2000年 | 79篇 |
1999年 | 69篇 |
1998年 | 64篇 |
1997年 | 38篇 |
1996年 | 41篇 |
1995年 | 37篇 |
1994年 | 31篇 |
1993年 | 37篇 |
1992年 | 44篇 |
1991年 | 46篇 |
1990年 | 49篇 |
1989年 | 52篇 |
1988年 | 48篇 |
1987年 | 30篇 |
1986年 | 30篇 |
1985年 | 42篇 |
1984年 | 29篇 |
1983年 | 34篇 |
1982年 | 28篇 |
1981年 | 22篇 |
1979年 | 34篇 |
1977年 | 19篇 |
1976年 | 31篇 |
1974年 | 17篇 |
1973年 | 24篇 |
1971年 | 22篇 |
1970年 | 22篇 |
排序方式: 共有4510条查询结果,搜索用时 203 毫秒
1.
2.
3.
Steven J. Tucker David McClelland Kristina Sep?i? Roderick H. Scott 《生物化学与生物物理学报:生物膜》2003,1614(2):171-181
The ability of two alkyl pyridinium sponge toxin preparations (poly-APS and halitoxin) to form transient pores/lesions in cell membranes and allow transfection of plasmid cDNA have been investigated using HEK 293 cells. Poly-APS and halitoxin preparations caused a collapse in membrane potential, reductions in input resistance and increased Ca2+ permeability. At least partial recovery was observed after poly-APS application but recovery was more rarely seen with halitoxin. The transfection with plasmid cDNAs for an enhanced green fluorescent protein (EGFP) and human tumour necrosis factor receptor 2 (TNFR2) was assessed for both toxin preparations and compared with lipofectamine. Stable transfection was achieved with poly-APS although it was less efficient than lipofectamine. These results show that viable cells transfected with alien cDNA can be obtained using novel transient pore-forming alkyl pyridinium sponge toxins and a simple pre-incubation protocol. This provides the first proof of principle that pore-forming alkyl pyridinium compounds can be used to deliver cDNA to the intracellular environment without permanently compromising the plasma membrane. 相似文献
4.
Myriam R. Hirt Marlee Tucker Thomas Müller Benjamin Rosenbaum Ulrich Brose 《Ecology and evolution》2020,10(14):7094-7105
- Realized trophic niches of predators are often characterized along a one‐dimensional range in predator–prey body mass ratios. This prey range is constrained by an “energy limit” and a “subdue limit” toward small and large prey, respectively. Besides these body mass ratios, maximum speed is an additional key component in most predator–prey interactions.
- Here, we extend the concept of a one‐dimensional prey range to a two‐dimensional prey space by incorporating a hump‐shaped speed‐body mass relation. This new “speed limit” additionally constrains trophic niches of predators toward fast prey.
- To test this concept of two‐dimensional prey spaces for different hunting strategies (pursuit, group, and ambush predation), we synthesized data on 63 terrestrial mammalian predator–prey interactions, their body masses, and maximum speeds.
- We found that pursuit predators hunt smaller and slower prey, whereas group hunters focus on larger but mostly slower prey and ambushers are more flexible. Group hunters and ambushers have evolved different strategies to occupy a similar trophic niche that avoids competition with pursuit predators. Moreover, our concept suggests energetic optima of these hunting strategies along a body mass axis and thereby provides mechanistic explanations for why there are no small group hunters (referred to as “micro‐lions”) or mega‐carnivores (referred to as “mega‐cheetahs”).
- Our results demonstrate that advancing the concept of prey ranges to prey spaces by adding the new dimension of speed will foster a new and mechanistic understanding of predator trophic niches and improve our predictions of predator–prey interactions, food web structure, and ecosystem functions.
5.
6.
7.
Se-Chan Kim Alexander Ghanem Heidi Stapel Klaus Tiemann Pascal Knuefermann Andreas Hoeft Rainer Meyer Christian Grohé Anne A Knowlton Georg Baumgarten 《BMC physiology》2007,7(1):5
Backgound
It has been reported that Toll-like receptor 4 (TLR4) deficiency reduces infarct size after myocardial ischemia/reperfusion (MI/R). However, measurement of MI/R injury was limited and did not include cardiac function. In a chronic closed-chest model we assessed whether cardiac function is preserved in TLR4-deficient mice (C3H/HeJ) following MI/R, and whether myocardial and systemic cytokine expression differed compared to wild type (WT). 相似文献8.
Osmotic Transport across Cell Membranes in Nondilute Solutions: A New Nondilute Solute Transport Equation 总被引:1,自引:0,他引:1
The fundamental physical mechanisms of water and solute transport across cell membranes have long been studied in the field of cell membrane biophysics. Cryobiology is a discipline that requires an understanding of osmotic transport across cell membranes under nondilute solution conditions, yet many of the currently-used transport formalisms make limiting dilute solution assumptions. While dilute solution assumptions are often appropriate under physiological conditions, they are rarely appropriate in cryobiology. The first objective of this article is to review commonly-used transport equations, and the explicit and implicit assumptions made when using the two-parameter and the Kedem-Katchalsky formalisms. The second objective of this article is to describe a set of transport equations that do not make the previous dilute solution or near-equilibrium assumptions. Specifically, a new nondilute solute transport equation is presented. Such nondilute equations are applicable to many fields including cryobiology where dilute solution conditions are not often met. An illustrative example is provided. Utilizing suitable transport equations that fit for two permeability coefficients, fits were as good as with the previous three-parameter model (which includes the reflection coefficient, σ). There is less unexpected concentration dependence with the nondilute transport equations, suggesting that some of the unexpected concentration dependence of permeability is due to the use of inappropriate transport equations. 相似文献
9.
10.