全文获取类型
收费全文 | 195篇 |
免费 | 22篇 |
专业分类
217篇 |
出版年
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 12篇 |
2013年 | 8篇 |
2012年 | 7篇 |
2011年 | 8篇 |
2010年 | 8篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 12篇 |
2006年 | 9篇 |
2005年 | 6篇 |
2004年 | 8篇 |
2003年 | 2篇 |
2002年 | 5篇 |
2001年 | 9篇 |
2000年 | 6篇 |
1999年 | 5篇 |
1998年 | 11篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有217条查询结果,搜索用时 15 毫秒
101.
102.
Vincent Ranwez Frédéric Delsuc Sylvie Ranwez Khalid Belkhir Marie-Ka Tilak Emmanuel JP Douzery 《BMC evolutionary biology》2007,7(1):241
Background
Molecular sequence data have become the standard in modern day phylogenetics. In particular, several long-standing questions of mammalian evolutionary history have been recently resolved thanks to the use of molecular characters. Yet, most studies have focused on only a handful of standard markers. The availability of an ever increasing number of whole genome sequences is a golden mine for modern systematics. Genomic data now provide the opportunity to select new markers that are potentially relevant for further resolving branches of the mammalian phylogenetic tree at various taxonomic levels. 相似文献103.
Alexander Kotrschal Eva JP Lievens Josefin Dahlbom Andreas Bundsen Svetlana Semenova Maria Sundvik Alexei A Maklakov Svante Winberg Pertti Panula Niclas Kolm 《Evolution; international journal of organic evolution》2014,68(4):1139-1149
Animal personalities range from individuals that are shy, cautious, and easily stressed (a “reactive” personality type) to individuals that are bold, innovative, and quick to learn novel tasks, but also prone to routine formation (a “proactive” personality type). Although personality differences should have important consequences for fitness, their underlying mechanisms remain poorly understood. Here, we investigated how genetic variation in brain size affects personality. We put selection lines of large‐ and small‐brained guppies (Poecilia reticulata), with known differences in cognitive ability, through three standard personality assays. First, we found that large‐brained animals were faster to habituate to, and more exploratory in, open field tests. Large‐brained females were also bolder. Second, large‐brained animals excreted less cortisol in a stressful situation (confinement). Third, large‐brained animals were slower to feed from a novel food source, which we interpret as being caused by reduced behavioral flexibility rather than lack of innovation in the large‐brained lines. Overall, the results point toward a more proactive personality type in large‐brained animals. Thus, this study provides the first experimental evidence linking brain size and personality, an interaction that may affect important fitness‐related aspects of ecology such as dispersal and niche exploration. 相似文献
104.
105.
Solveig Tangedal Marianne Aanerud Louise JP Persson Karl A Brokstad Per S Bakke Tomas M Eagan 《Respiratory research》2014,15(1)
Background
Sputum induction is a non-invasive method for obtaining measurements of inflammation in the airways. Whether spontaneously sampled sputum can be a valid surrogate is unknown. The aim of this study was to compare levels of six inflammatory markers in sputum pairs consisting of induced and spontaneous sputum sampled on the same consultation either in a stable state or during exacerbations of chronic obstructive pulmonary disease (COPD).Methods
433 COPD patients aged 40–76, Global initiative for chronic Obstructive Lung Disease (GOLD) stage II-IV were enrolled in 2006/07 and followed every six months for three years. 356 patients were followed for potential exacerbations. Interleukin-6, interleukin-8, interleukin-18, interferon gamma-inducible protein-10, monokine induced by gamma interferon and tumor necrosis factor-alpha (IL-6, IL-8, IL-18, IP-10, MIG and TNF-α) were measured by bead based multiplex immunoassay in 60 paired sputum samples from 45 patients. Albumin was measured by enzyme immunoassay, for concentration correction. Culturing for bacterial growth was performed on 24 samples. Bland-Altman plots were used to assess agreement. The paired non-parametric Wilcoxon signed-rank test, the non-parametric Spearman’s rank correlation test and Kruskal-Wallis test were used for statistical analyses. For all analyses, a p-value < 0.05 was considered significant.Results
Agreement between the two measurements was generally low for all six markers. TNF-α was significantly higher in spontaneous sputum at exacerbations (p = 0.002) and trending higher at the steady state (p = 0.06). Correlation coefficients between the levels of markers in induced and spontaneous sputum varied between 0.58 (IL-18) to 0.83 (IP-10). In spontaneous sputum IL-18 and MIG were higher in ex-smokers (p < 0.05). The levels of all markers were higher in GOLD stage III & IV except for IL-6 in spontaneous sputum and IL-18 in induced sputum, compared with GOLD stage II, although not statistically significant. In spontaneous sputum the levels of IL-6 were significantly higher if Haemophilus influenzae (HI) was not cultured.Conclusion
We observed a low agreement and significant differences in inflammatory markers between induced and spontaneous sputum, both at steady state and exacerbations. We recommend considering sampling method when reporting on inflammatory markers in sputum. 相似文献106.
The non-acidic polygalacturonases produced by Aspergillus kawachii in a glucose/tryptone medium were adsorbed to a glass fiber microfilter that was used to clarify the fermentation broth.
Maximum adsorption occurred at pH 3 under low ionic strength conditions. The adsorbed activity could be readily released with
a buffer solution at pH 5. Based upon these observations, a separation process was developed which enabled the broth to be
clarified and, at the same time, the non-acidic polygalacturonases to be concentrated 20-fold and purified 100-fold in a unique
filtration step. The practical advantage of recovering polygalacturonases by a filtration process lies in the simplicity and
efficiency of the operation involved.
Received 27 July 2005; Revisions requested 24 August 2005; Revisions received 16 November 2005; Accepted 16 November 2005 相似文献
107.
A direct mass spectrometric investigation of nerve homologs of the abdominal perisympathetic organs was employed to reveal the first and complete sequences of CAPA peptides from a hemipteran species, the southern green stinkbug Nezara viridula. Side-chain fragmentations allowed the assignment of internal Leu/Ile; on-plate acetylation was used to distinguish between the mass-related Lys and Gln. The following sequences were obtained: DQLFPFPRV-NH(2) (CAPA-PVK-1), EQLIPFPRV-NH(2) (CAPA-PVK-2), and NGSAGNGGLWFGPRL/I-NH(2) (CAPA-PK). CAPA-PVKs are associated with the regulation of diuresis in insects, and identification of those native to a hemipteran will provide the experimental basis to better understand regulation of water balance in this family of insects. 相似文献
108.
109.
Magnetic material in the body parts of the stingless bee Schwarziana quadripunctata, heads, pairs of antennae, thorax and abdomens, were investigated by SQUID magnetometry and Ferromagnetic Resonance (FMR).
The saturation, Js and remanent, Jr, magnetizations and coercive field Hc are determined from the hysteresis curves. From Hc and Jr/Js the magnetic particle sizes are estimated. The Js and the FMR spectral absorption areas yield 23±3%, 45±5%, 15±2% and 19±4% magnetic material contributions of head, pair of
antennae, thorax and abdomen, respectively, similar to those observed in the migratory ant Pachycondyla marginata. This result is discussed in light of the hypothesis of antennae as a magnetosensor structure. 相似文献
110.
Thymulin is a well-characterized thymic hormone that exists as a nonapeptide coupled to equimolar amounts of Zn2+. Thymulin is known to have multiple biological roles, including T cell differentiation, immune regulation, and analgesic functions. It has been shown that thymulin is produced by the reticulo-epithelial cells of the thymus, and it circulates in the blood from the moment of birth, maintain its serum level until puberty diminishing thereafter in life. To study the localization of this hormone, we prepared polyclonal and monoclonal antibodies against the commercial peptide and utilized immunocytochemical techniques for visualization. The results indicate that thymulin stains the thymic reticular cells, the outer layers of Hassall's corpuscles and a large round cellular type, which is keratin-negative and does not show affinity for the common leukocyte antigen (CD-45). In mice, this thymulin-positive cell remains in the thymus throughout life and even appears in relatively increased numbers in old involuted thymi. It also appears in thymus-dependent areas of the spleen and lymph nodes, demonstrating that at least one of the thymus cells containing this peptide can be found in peripheral lymphoid tissue. 相似文献