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排序方式: 共有163条查询结果,搜索用时 15 毫秒
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Constantí Stefanescu Ferran Páramo Susanne Åkesson Marta Alarcón Anna Ávila Tom Brereton Jofre Carnicer Louis F. Cassar Richard Fox Janne Heliölä Jane K. Hill Norbert Hirneisen Nils Kjellén Elisabeth Kühn Mikko Kuussaari Matti Leskinen Felix Liechti Martin Musche Eugenie C. Regan Don R. Reynolds David B. Roy Nils Ryrholm Heiko Schmaljohann Josef Settele Chris D. Thomas Chris van Swaay Jason W. Chapman 《Ecography》2013,36(4):474-486
Long‐range, seasonal migration is a widespread phenomenon among insects, allowing them to track and exploit abundant but ephemeral resources over vast geographical areas. However, the basic patterns of how species shift across multiple locations and seasons are unknown in most cases, even though migrant species comprise an important component of the temperate‐zone biota. The painted lady butterfly Vanessa cardui is such an example; a cosmopolitan continuously‐brooded species which migrates each year between Africa and Europe, sometimes in enormous numbers. The migration of 2009 was one of the most impressive recorded, and thousands of observations were collected through citizen science programmes and systematic entomological surveys, such as high altitude insect‐monitoring radar and ground‐based butterfly monitoring schemes. Here we use V. cardui as a model species to better understand insect migration in the Western Palaearctic, and we capitalise on the complementary data sources available for this iconic butterfly. The migratory cycle in this species involves six generations, encompassing a latitudinal shift of thousands of kilometres (up to 60 degrees of latitude). The cycle comprises an annual poleward advance of the populations in spring followed by an equatorward return movement in autumn, with returning individuals potentially flying thousands of kilometres. We show that many long‐distance migrants take advantage of favourable winds, moving downwind at high elevation (from some tens of metres from the ground to altitudes over 1000 m), pointing at strong similarities in the flight strategies used by V. cardui and other migrant Lepidoptera. Our results reveal the highly successful strategy that has evolved in these insects, and provide a useful framework for a better understanding of long‐distance seasonal migration in the temperate regions worldwide. 相似文献
3.
Experimental evidence shows that site fertility is a key modulator underlying plant community changes under climate change. Communities on fertile sites, with species having fast dynamics, have been found to react more strongly to climate change than communities on infertile sites with slow dynamics. However, it is still unclear whether this generally applies to high‐latitude plant communities in natural environments at broad spatial scales. We tested a hypothesis that vegetation of fertile sites experiences greater changes over several decades and thus would be more responsive under contemporary climate change compared to infertile sites that are expected to show more resistance. We resurveyed understorey communities (vascular plants, bryophytes, and lichens) of four infertile and four fertile forest sites along a latitudinal bioclimatic gradient. Sites had remained outside direct human disturbance. We analyzed the magnitude of temporal community turnover, changes in the abundances of plant morphological groups and strategy classes, and changes in species diversity. In agreement with our hypothesis, temporal turnover of communities was consistently greater on fertile sites compared to infertile sites. However, our results suggest that the larger turnover of fertile communities is not primarily related to the direct effects of climatic warming. Furthermore, community changes in both fertile and infertile sites showed remarkable variation in terms of shares of plant functional groups and strategy classes and measures of species diversity. This further emphasizes the essential role of baseline environmental conditions and nonclimatic drivers underlying vegetation changes. Our results show that site fertility is a key determinant of the overall rate of high‐latitude vegetation changes but the composition of plant communities in different ecological contexts is variously impacted by nonclimatic drivers over time. 相似文献
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Koivula T Ekman M Leitner T Löfdahl S Ghebremicahel S Mostowy S Behr MA Svenson SB Källenius G 《Microbes and infection / Institut Pasteur》2004,6(3):272-278
In a previous study of Mycobacterium tuberculosis complex isolates from Guinea-Bissau in West Africa, we identified a unique group of strains, designated here as the Guinea-Bissau family of strains, which, although genotypically closely related, phenotypically demonstrated a considerable heterogeneity. We conducted here a detailed genotypic analysis of a subset (n = 35) of these isolates. Based on the data obtained, and by comparison of known corresponding genes in mycobacteria outside the M. tuberculosis complex, we propose that the Guinea-Bissau strains belong to a unique branch of the M. tuberculosis complex tree in between classical M. tuberculosis and classical M. bovis. These observations are discussed in their significance in M. tuberculosis complex classification. 相似文献
6.
Lätti S Leskinen M Shiota N Wang Y Kovanen PT Lindstedt KA 《Journal of cellular physiology》2003,195(1):130-138
Degranulated mast cells are present in the subendothelial space of eroded (de-endothelialized) coronary atheromas. Upon degranulation, mast cells secrete into the surrounding tissue an array of preformed and newly synthesized mediators, including proapoptotic molecules, such as chymase and TNF-alpha. In a co-culture system involving rat serosal mast cells and rat cardiac (microvascular) endothelial cells, we could show, by means of competitive RT-PCR, immunoblotting, immunocytochemistry, annexin staining, flow cytometry, and DNA-laddering, that stimulation of mast cells with ensuing degranulation rapidly (within 30 min) down-regulated the expression of both bcl-2 mRNA and protein, with subsequent induction of apoptosis in the endothelial cells. The major effect of bcl-2 down-regulation resided in the exocytosed granule remnants, a minor effect also being present in the granule remnant-free supernatant. No significant changes were observed in the expression levels of the pro-apoptotic protein, bax. The mast cell-mediated apoptotic effect was partially (70%) dependent on the presence of TNF-alpha and involved the translocation of cytochrome C from mitochondria into cytoplasm. These results are the first to show that one of the cell types present in the atherosclerotic plaques, namely the mast cell, by releasing both granule-remnant-bound and soluble TNF-alpha, may contribute to the erosion of atherosclerotic plaques by inducing apoptosis in adjacent endothelial cells. Published 2003 Wiley-Liss, Inc. 相似文献
7.
Liukkonen-Anttila T Honkanen H Peltokangas P Pelkonen O Hohtola E 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2003,134(1):69-77
We examined hepatic cytochrome P450 activity in wild and hand-reared grey partridges (Perdix perdix), capercaillies (Tetrao urogallus) and ring-necked pheasants (Phasianus colchicus), as well as the enzyme activity in a variety of tissues of hand-reared Japanese quails (Coturnix coturnix japonica) and pigeons (Columba livia). Post-mortem decrease in hepatic enzyme activity in the grey partridge was measured. Hepatic 7-ethoxyresorufin-O-deethylase activity was similar in wild and hand-reared grey partridges and pheasants, but the activity was significantly lower in wild than in hand-reared capercaillies, probably resulting from their phenolic-rich diet. In the tissues of both quails and pigeons 7-ethoxycoumarin-O-deethylase exhibited the highest and 7-pentoxyresorufin-O-deethylase the lowest activity. Hepatic enzyme activity was significantly higher than that in other tissues. In the small intestine some activity could be found, reflecting some intestinal detoxication capacity. Enzyme activity decreased by 34-69% during the 30-min sampling period, which confirmed the importance of equalising sampling time to obtain comparable data. Because the hand-reared birds in this study were fed the same commercial diets, we assumed that the enzyme activity values detected reflect species differences without any induction by dietary secondary compounds. 相似文献
8.
Jougasaki M Leskinen H Larsen AM Luchner A Cataliotti A Tachibana I Burnett JC 《Peptides》2003,24(6):889-892
Both cardiotrophin-1 (CT-1) and B-type or brain natriuretic peptide (BNP) are activated by cardiomyocyte stretch, and gene expression of CT-1 and BNP are augmented in the heart in experimental and human congestive heart failure (CHF). The goal of this study was to define cardiac gene expression of CT-1 and BNP by Northern blot analysis in normal (n=5), early left ventricular dysfunction (ELVD, n=5) and overt CHF dogs (n=5), in which ventricular function is progressively decreased. CT-1 mRNA was detected in both atria and ventricles in normal dogs. Ventricular CT-1 mRNA production increased in ELVD, and it further increased in overt CHF. Ventricular BNP mRNA remained below or at the limit of detection in normal and ELVD models, and it markedly increased in overt CHF. This study reports differential regulation of gene expression of CT-1 and BNP in the heart during the progression of CHF, and demonstrates that ventricular CT-1 gene activation precedes ventricular BNP gene activation. 相似文献
9.
Cryopreservation of embryogenic cultures of Scots pine 总被引:7,自引:2,他引:5
Häggman Hely M. Ryynänen Leena A. Aronen Tuija S. Krajnakova Jana 《Plant Cell, Tissue and Organ Culture》1998,54(1):45-53
The aim of the study was to develop an effective cryopreservation method for Scots pine (Pinus sylvestris L.) embryogenic
cultures. Altogether nine cell lines derived from three mother trees were cryopreserved after cold hardening using dimethylsulfoxide
or two different mixtures of polyethyleneglycol 6000, glucose and dimethylsulfoxide as cryoprotectants. Seventy-eight percent
of the cell lines remained viable after cryostorage, the best cryoprotectant treatment being 10% polyethyleneglycol 6000,
10% glucose, and 10% dimethylsulfoxide in water. This treatment resulted in significantly better regrowth of the embryogenic
cultures than with the other cryoprotectants or with the controls. According to microscopical observations, the cells that
retained their viability and regrowth ability after cryopreservation were the embryonal head cells, as well as some elliptic
suspensor cells close to the embryonal head cell area. When proliferation growth of the frozen cultures had started, their
morphological appearance was the same as the non-frozen cultures. In addition, the RAPD assays suggested that the cryostorage
treatment used here preserved the genetic fidelity of the Scots pine embryogenic cultures.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
10.
Jukka Bisi Tuija Liukkonen Sakari Mykrä Mari Pohja-Mykrä Sami Kurki 《European Journal of Wildlife Research》2010,56(5):771-779
This article focuses on the roots of the Finnish wolf conflict by using stakeholder evaluations of the wolf as a tool. The
recent growth of the wolf population has highlighted stakeholders’ contradictory objectives and revealed a conflict between
the two main stakeholders, conservationists and hunters, in wolf management. The question of hunting emerges as the core of
the conflict. The negative evaluation of the wolf by hunters reflects a competitive situation, which is typical of the historical
development of wolf management in Finland. In areas with the most abundant wolf populations, hunters view the wolf most negatively.
This study clearly demonstrates that the Finnish wolf conflict is rooted in the values of modern society and carries a long
historical, practical and ecological background in which humans and wolves compete over resources, mainly the moose. The conflict
between hunters and conservationists in wolf management is connected to the appreciation of moose as game and stems from competition
between humans and wolves over their prey and the historical presence or absence of the wolf. 相似文献