全文获取类型
收费全文 | 366篇 |
免费 | 33篇 |
国内免费 | 1篇 |
出版年
2023年 | 2篇 |
2021年 | 4篇 |
2020年 | 17篇 |
2019年 | 40篇 |
2018年 | 29篇 |
2017年 | 4篇 |
2016年 | 8篇 |
2015年 | 7篇 |
2014年 | 7篇 |
2013年 | 23篇 |
2012年 | 8篇 |
2011年 | 1篇 |
2010年 | 11篇 |
2009年 | 5篇 |
2008年 | 15篇 |
2007年 | 16篇 |
2006年 | 17篇 |
2005年 | 11篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 9篇 |
2001年 | 14篇 |
2000年 | 6篇 |
1999年 | 12篇 |
1998年 | 16篇 |
1997年 | 7篇 |
1996年 | 19篇 |
1995年 | 15篇 |
1994年 | 5篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 4篇 |
1990年 | 3篇 |
1989年 | 12篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有400条查询结果,搜索用时 35 毫秒
61.
A journey through time: exploring temporal patterns amongst digitized plant specimens from Australia
MD. Mohasinul Haque David A. Nipperess John B. Baumgartner Linda J. Beaumont 《分类学与生物多样性》2018,16(6):604-613
Online access to species occurrence records has opened new windows into investigating biodiversity patterns across multiple scales. The value of these records for research depends on their spatial, temporal, and taxonomic quality. We assessed temporal patterns in records from the Australasian Virtual Herbarium, asking: (1) How temporally consistent has collecting been across Australia? (2) Which areas of Australia have the most reliable records, in terms of temporal consistency and inventory completeness? (3) Are there temporal trends in the completeness of attribute information associated with records? We undertook a multi-step filtering procedure, then estimated temporal consistency and inventory completeness for sampling units (SUs) of 50?km ×?50?km. We found temporal bias in collecting, with 80% of records collected over the period 1970–1999. South-eastern Australia, the Wet Tropics in north-east Queensland, and parts of Western Australia have received the most consistent sampling effort over time, whereas much of central Australia has had low temporal consistency. Of the SUs, 18% have relatively complete inventories with high temporal consistency in sampling. We also determined that 25% of digitized records had missing attribute information. By identifying areas with low reliability, we can limit erroneous inferences about distribution patterns and identify priority areas for future sampling. 相似文献
62.
63.
MD Mahafizur Rahman Elias Flory Hans-Werner Koyro Zainul Abideen Adam Schikora Christian Suarez Sylvia Schnell Massimiliano Cardinale 《Systematic and applied microbiology》2018,41(4):386-398
The importance of the plant microbiome for host fitness has led to the concept of the “plant holobiont”. Seeds are reservoirs and vectors for beneficial microbes, which are very intimate partners of higher plants with the potential to connect plant generations. In this study, the endophytic seed microbiota of numerous barley samples, representing different cultivars, geographical sites and harvest years, was investigated. Cultivation-dependent and -independent analyses, microscopy, functional plate assays, greenhouse assays and functional prediction were used, with the aim of assessing the composition, stability and function of the barley seed endophytic bacterial microbiota. Associations were consistently detected in the seed endosphere with Paenibacillus, Pantoea and Pseudomonas spp., which were able to colonize the root with a notable rhizocompetence after seed germination. In greenhouse assays, enrichment with these bacteria promoted barley growth, improved mineral nutrition and induced resistance against the fungal pathogen Blumeria graminis. We demonstrated here that barley, an important crop plant, was consistently associated with beneficial bacteria inside the seeds. The results have relevant implications for plant microbiome ecology and for the holobiont concept, as well as opening up new possibilities for research and application of seed endophytes as bioinoculants in sustainable agriculture. 相似文献
64.
Bourinbaiar AS Borkowsky W Krasinski KM Fruhstorfer EC 《Journal of biomedical science》1997,4(4):162-168
Although placental trophoblasts, the only fetal cells in direct contact with infectious maternal blood, can be infected with HIV, the precise cause for the low transmission rate of virus across the placental barrier is unknown. One of the most common conjectures is that maternal anti-HIV antibodies (Abs) contribute to the protection of the fetus. This hypothesis has been tested in vitro by infecting the CD4-negative placental trophoblast line, BeWo, with HIV-1IIIB in the presence of serial dilutions of neutralizing monoclonal Abs against the V3 loop (No. 694) or CD4-binding conformational domain (No. 588). The results, based on measurement of p24 production from virus-exposed cells, reveal that the titers of Abs, adequate in preventing the infection of control MT-4 T lymphocytes, were less effective in protecting trophoblasts. Furthermore, PCR analysis of HIV DNA formed after a single round of infection has shown no significant decrease in the number of viral copies in Ab-protected BeWo cells. An anti-HIV serum from a pregnant woman did also have no effect. Although our in vitro observations do not necessarily apply to the in vivo situation, the results suggest that the humoral immune response sustained by neutralizing Abs may be able to protect T lymphocytes, but not placental trophoblasts. The findings are consistent with recent clinical studies demonstrating a lack of correlation between the presence of neutralizing anti-HIV Abs in pregnant women and HIV transmission in utero. 相似文献
65.
P. R. Y. Backwell MD . Jennions J. H. Christy & N. I. Passmore 《Ethology : formerly Zeitschrift fur Tierpsychologie》1999,105(5):415-421
In the fiddler crab, Uca annulipes, males attract receptive females into their burrows by waving their greatly enlarged major claw. We have previously shown that males clustered around a female wave in close synchrony. Females may have a preference for leading signals and synchronised waving may arise as an epiphenomenon of competition between males to signal first. Indeed, the males in clusters that females approach and visit in their burrows are more likely to produce leading waves than are their neighbours. Here we document two other differences in the waving behaviour of visited males and their neighbours. First, visited males complete the downward component of the wave more rapidly than their neighbours. Second, the interval between the end of one wave and the start of the next is shorter for visited males. How can waving be synchronous if visited males wave faster than their neighbours? While only 9% (40/431) of waves by neighbours did not overlap those of the visited male, 22% (110/501) of visited male waves did not overlap the wave of a focal neighbour (111 visited male-neighbour dyads). Hence, while overlapping waves are nearly synchronous, visited males produce additional, ‘nonoverlapping’ waves that result in a higher wave rate than that of their neighbours. 相似文献
66.
Photosynthetic activity of developing leaves of Zea mays is less affected by heat stress than that of developed leaves 总被引:9,自引:0,他引:9
Various physiological and biochemical characters of a leaf change with stages of its ontogeny. It is likely that the photosynthetic functions of leaves of different ontogeny have different levels of heat tolerance. This study was initiated to analyze the photosynthetic heat tolerance of fully-developed, nearly-developed (more than 2/3 expanded) and developing (10–12 cm visible) leaves of two maize genotypes, F223 and F250. The results indicate that the photosynthetic CO2 assimilation rate (Pn ) of developing leaves was less affected by heat stress (42°C in the dark for 90 min) than that of developed leaves. The impaired Pn recovered within 24 h in the developing leaves, while the Pn of developed and nearly-developed leaves did not reach the non-stress level, even after 72 h. The Pn of the developed leaves of genotype F250 was less affected by heat stress than that of genotype F223. After heat stress, the slightly affected Pn of the developing leaf was associated with the almost unchanged photochemical efficiency of photosystem II (Fv /Fm ) and the quantum yield of photosystem II electron transport. The chlorophylls a and b were degraded by heat stress; the degradation was pronounced in the developed leaves. As a result of heat stress, the antheraxanthin and zeaxanthin of the xanthophyll cycle accumulated in both the nearly-developed and developed leaves but not in the developing leaves. Injury to the plasma membrane due to heat stress was much less severe in developing leaves than that in the developed leaves. From the physiological characters which we determined it would appear that the Pn functions of the developing leaves are more resistant to heat stress than those of nearly-developed and developed leaves. 相似文献
67.
Naeem Khan Asghari Bano Muhammad Adnan Shahid Wajid Nasim MD Ali Babar 《Biologia》2018,73(11):1083-1098
Drought is one of the key restraints to agricultural productivity worldwide and is expected to increase further. Drought stress accompanied by reduction in precipitation pose major challenges to future food safety. Strategies should be develop to enhance drought tolerance in crops like chickpea and wheat, in order to enhance their growth and yield. Drought tolerance strategies are costly and time consuming however, recent studies specify that plant growth promoting rhizobacteria (PGPR) and plant growth regulators (PGRs) can help plants to withstand under harsh environmental condition and enable plants to cope with drought stress. PGPR can act as biofertilizer and bioenhancer for different legumes and non-legumes. The use of PGPR and symbiotic microorganisms, may be valuable in developing strategies to assist water conservation in plants. The use of PGPR has been confirmed to be an ecologically sound way of enhancing crop yields by facilitating plant growth through direct or indirect mechanism. The mechanisms of PGPR for water conservation include secretion of exopolysaccharides, biofilm formation, alternation in phytohormone content, improvement in sugar concentration, enhancing availability of micro- and macronutrients and changes in plant functional traits. Similarly, plant growth regulators (PGRs) are specially noticed in actively growing tissues under stress conditions and have been associated in the control of cell division, embryogenesis, root formation, fruit development and ripening, and reactions to biotic and abiotic stresses and upholding water conservation status in plants. Previous studies also suggest that plant metabolites interact with plant physiology under stress condition and impart drought tolerance. Metabolites like, sugars, amino acids, organic acid and polyols play a key role in drought tolerance of crop plants grown under stress condition. It is concluded from the present study that PGRs in combination with PGPR consortium can be an effective formulation to promote plant growth and maintenance of plant turgidity under drought stress. This review is a compilation of the effect of drought stress on crop plants and described interactions between PGPR/PGRs and plant development, knowledge of water conservation and stress release strategies of PGPR and PGRs and the role of plant metabolites in drought tolerance of crop plants. This review also bridges the gaps that summarizes the mechanism of action of PGPR for drought tolerance of crop plants and sustainability of agriculture and applicability of these beneficial rhizobacteria in different agro-ecosystems under drought stress. 相似文献
68.
69.
Primary familial brain calcification with a novel SLC20A2 mutation: Analysis of PiT‐2 expression and localization
下载免费PDF全文
![点击此处可从《Journal of cellular physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
70.
Gax suppresses chemerin/CMKLR1‐induced preadipocyte biofunctions through the inhibition of Akt/mTOR and ERK signaling pathways
下载免费PDF全文
![点击此处可从《Journal of cellular physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yunqi Jiang MD Ping Liu MD PhD Wenlin Jiao MD Juan Meng MD Jinbo Feng MD 《Journal of cellular physiology》2018,233(1):572-586
Adipose tissue is closely associated with angiogenesis and vascular remodeling. Chemerin is involved in inflammatory reaction and vascular dysfunction. However, the mechanisms of chemerin participating in vascular remodeling and whether Growth arrest‐specific homeobox (Gax) can effectively intervene it remain obscured. Here, 3T3‐F442A preadipocytes were cultured, injected into athymic mice to model fat pads, and treated respectively with Ad‐chemerin, Ad‐Gax, or specific inhibitors in vitro and in vivo. MTT, flow cytometry, Western blotting, and imunohisto(cyto)‐chemistry analyses showed that chemerin enhanced the expression of FABP4 and VEGF, activated Akt/mTOR and ERK pathways, increased the cell percent of S phase, decreased the percent of G0‐G1 phase and apoptotic cells, and augmented neovascular density in fat pads. Inversely, Gax suppressed the expression of these adipogenic and vasifactive markers and these signaling proteins, decreased the percent of S phase cells, and increased those of G0‐G1 phase and apoptotic cells, and reduced the neovascular density. Our results indicate that chemerin‐CMKLR1 activates Akt/mTOR and ERK pathways and facilitates preadipocyte proliferation, adipogenesis, and angiogenesis. Contrarily, Gax weakens the effect of chemerin on preadipocyte biofunctions. 相似文献