全文获取类型
收费全文 | 3805篇 |
免费 | 263篇 |
专业分类
4068篇 |
出版年
2023年 | 21篇 |
2022年 | 23篇 |
2021年 | 41篇 |
2020年 | 25篇 |
2019年 | 55篇 |
2018年 | 112篇 |
2017年 | 89篇 |
2016年 | 147篇 |
2015年 | 258篇 |
2014年 | 191篇 |
2013年 | 340篇 |
2012年 | 293篇 |
2011年 | 216篇 |
2010年 | 214篇 |
2009年 | 160篇 |
2008年 | 179篇 |
2007年 | 151篇 |
2006年 | 164篇 |
2005年 | 138篇 |
2004年 | 133篇 |
2003年 | 102篇 |
2002年 | 111篇 |
2001年 | 84篇 |
2000年 | 83篇 |
1999年 | 63篇 |
1998年 | 34篇 |
1997年 | 26篇 |
1996年 | 19篇 |
1995年 | 30篇 |
1994年 | 22篇 |
1993年 | 17篇 |
1992年 | 52篇 |
1991年 | 42篇 |
1990年 | 37篇 |
1989年 | 32篇 |
1988年 | 27篇 |
1987年 | 34篇 |
1986年 | 27篇 |
1985年 | 27篇 |
1984年 | 17篇 |
1983年 | 16篇 |
1982年 | 11篇 |
1980年 | 11篇 |
1975年 | 11篇 |
1974年 | 13篇 |
1973年 | 16篇 |
1972年 | 20篇 |
1970年 | 16篇 |
1968年 | 11篇 |
1965年 | 20篇 |
排序方式: 共有4068条查询结果,搜索用时 8 毫秒
1.
Valentina Isetta Josep M. Montserrat Raquel Santano Alison J. Wimms Dinesh Ramanan Holger Woehrle Daniel Navajas Ramon Farré 《PloS one》2016,11(3)
Bench testing is a useful method to characterize the response of different automatic positive airway pressure (APAP) devices under well-controlled conditions. However, previous models did not consider the diversity of obstructive sleep apnea (OSA) patients’ characteristics and phenotypes. The objective of this proof-of-concept study was to design a new bench test for realistically simulating an OSA patient’s night, and to implement a one-night example of a typical female phenotype for comparing responses to several currently-available APAP devices. We developed a novel approach aimed at replicating a typical night of sleep which includes different disturbed breathing events, disease severities, sleep/wake phases, body postures and respiratory artefacts. The simulated female OSA patient example that we implemented included periods of wake, light sleep and deep sleep with positional changes and was connected to ten different APAP devices. Flow and pressure readings were recorded; each device was tested twice. The new approach for simulating female OSA patients effectively combined a wide variety of disturbed breathing patterns to mimic the response of a predefined patient type. There were marked differences in response between devices; only three were able to overcome flow limitation to normalize breathing, and only five devices were associated with a residual apnea-hypopnea index of <5/h. In conclusion, bench tests can be designed to simulate specific patient characteristics, and typical stages of sleep, body position, and wake. Each APAP device behaved differently when exposed to this controlled model of a female OSA patient, and should lead to further understanding of OSA treatment. 相似文献
2.
3.
4.
5.
Background
With increasing computer power, simulating the dynamics of complex systems in chemistry and biology is becoming increasingly routine. The modelling of individual reactions in (bio)chemical systems involves a large number of random events that can be simulated by the stochastic simulation algorithm (SSA). The key quantity is the step size, or waiting time, τ, whose value inversely depends on the size of the propensities of the different channel reactions and which needs to be re-evaluated after every firing event. Such a discrete event simulation may be extremely expensive, in particular for stiff systems where τ can be very short due to the fast kinetics of some of the channel reactions. Several alternative methods have been put forward to increase the integration step size. The so-called τ-leap approach takes a larger step size by allowing all the reactions to fire, from a Poisson or Binomial distribution, within that step. Although the expected value for the different species in the reactive system is maintained with respect to more precise methods, the variance at steady state can suffer from large errors as τ grows. 相似文献6.
The cell cycle modulated glycoprotein GP115 is one of the major yeast proteins containing glycosylphosphatidylinositol 总被引:11,自引:0,他引:11
The cell cycle modulated protein gp115 (115 kDa, isoelectric point about 4.8-5) of Saccharomyces cerevisiae undergoes various post-translational modifications. It is N-glycosylated during its maturation along the secretory pathway where an intermediary precursor of 100 kDa (p100), dynamically related to the mature gp115 protein, is detected at the level of endoplasmic reticulum. Moreover, we have shown by the use of metabolic labeling with [35S]methionine, [3H]palmitic acid and myo-[3H]inositol combined with high resolution two-dimensional gel electrophoresis and immunoprecipitation with a specific antiserum, that gp115 is one of the major palmitate- and inositol-containing proteins in yeast. These results, and the susceptibility of gp115 to phosphatidylinositol-specific phospholipase C treatment strongly indicate that gp115 contains the glycosylphosphatidylinositol (GPI) structure as membrane anchor domain. The two-dimensional analysis of the palmitate- and inositol-labeled proteins has also allowed the characterization of other polypeptides which possibly contain a GPI structure. 相似文献
7.
8.
9.
Rosa Agudo Ciro Rico Carles Vilà Fernando Hiraldo José Antonio Donázar 《BMC evolutionary biology》2010,10(1):384
Background
Anthropogenic habitat modifications have led to the extinction of many species and have favoured the expansion of others. Nonetheless, the possible role of humans as a diversifying force in vertebrate evolution has rarely been considered, especially for species with long generation times. We examine the influence that humans have had on the colonization and phenotypic and genetic differentiation of an insular population of a long-lived raptor species, the Egyptian vulture (Neophron percnopterus). 相似文献10.
Distinct effects of climate warming on populations of silver fir (Abies alba) across Europe 下载免费PDF全文