全文获取类型
收费全文 | 212篇 |
免费 | 24篇 |
专业分类
236篇 |
出版年
2016年 | 5篇 |
2015年 | 2篇 |
2013年 | 2篇 |
2012年 | 2篇 |
2011年 | 5篇 |
2010年 | 4篇 |
2009年 | 3篇 |
2007年 | 2篇 |
2006年 | 5篇 |
2004年 | 4篇 |
2003年 | 4篇 |
2002年 | 2篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1983年 | 3篇 |
1981年 | 4篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1972年 | 5篇 |
1969年 | 3篇 |
1959年 | 3篇 |
1958年 | 4篇 |
1957年 | 12篇 |
1956年 | 10篇 |
1955年 | 8篇 |
1954年 | 3篇 |
1953年 | 8篇 |
1952年 | 7篇 |
1951年 | 9篇 |
1950年 | 7篇 |
1949年 | 8篇 |
1948年 | 5篇 |
排序方式: 共有236条查询结果,搜索用时 0 毫秒
101.
102.
103.
104.
F Özdal-Kurt I Tuğlu HS Vatansever S Tong BH Şen SI Deliloğlu-Gürhan 《Biotechnic & histochemistry》2016,91(6):412-422
We investigated the effects of different implant biomaterials on cultured canine bone marrow stromal cells (BMSC) undergoing differentiation into osteoblasts (dBMSC). BMSC were isolated from canine humerus by marrow aspiration, cultured and differentiated on calcium phosphate scaffold (CPS), hydroxyapatite, hydroxyapatite in gel form and titanium mesh. We used the MTT method to determine the effects of osteogenic media on proliferation. The characteristics of dBMSC were assessed using alizarin red (AR), immunocytochemistry and osteoblastic markers including alkaline phosphatase/von Kossa (ALP/VK), osteocalcin (OC) and osteonectin (ON), and ELISA. The morphology of dBMSC on the biomaterials was investigated using inverted phase contrast microscopy and scanning electron microscopy. We detected expression of ALP/VK, AR, OC and ON by day 7 of culture; expression increased from day 14 until day 21. CPS supported the best adhesion, cell spreading, proliferation and differentiation of BMSCs. The effects of the biomaterials depended on their surface properties. Expression of osteoblastic markers showed that canine dBMSCs became functional osteoblasts. Tissue engineered stem cells can be useful clinically for autologous implants for treating bone wounds. 相似文献
105.
Young, A. J., Collins, J. C. and Russell, G. 1987. Ecotypicvariation in the osmotic responses of Enteromorpha intestinalis(L.) Link.J. exp. Bot. 38: 13091324. The physiological basis for salt tolerance has been studiedin the euryhaline marine alga Enteromorpha intestinalis. Adaptationto dilute and concentrated seawaters has been investigated inthree separate populations of this alga: marine, rock pool andestuarine. Internal K+, Na+ and Cl levels have been determined usingtracer efflux analyses. K+ has been shown to be the major osmoticsolute within this alga. Cellular levels of Cl and, inparticular, Na+ are low although levels in the cell wall arehigh. Levels of these ions varied considerably between the separateplants; K+ levels within marine plants of E. intestinalis aretwo to four times those found in the other populations. Thetertiary sulphonium compound ß-dimethylsulphonio-propionateis maintained at relatively high levels, although it remainsfairly insensitive to change in the external salinity. Changes in the tissue water content and cell volume are large,particularly within the estuarine plants. The thin cell wallsof these plants allow large changes in volume in the diluteconditions experienced in an estuary, while low turgor preventscell rupture. Thicker cell walls and small cells of the marineand rock pool plants assist in tolerating high and low externalosmotic potentialthe estuarine plants respond poorlyto concentrated seawater. Key words: Enteromorpha, osmoregulation, ecotypes 相似文献
106.
Pupae of the Queensland fruit fly or Q‐fly Bactrocera tryoni (Froggatt) are irradiated routinely to induce reproductive sterility in adults for use in sterile insect technique programmes. Previous studies suggest that adult sexual performance and survival under nutritional and crowding stress are compromised by the current target dose of radiation for sterilization (70–75 Gy), and that improved mating propensity and survival under stress by irradiated males may be achieved by reducing the target sterilization dose without reducing the level of induced sterility. This raises the question of the amount by which the irradiation dose can be reduced before residual fertility becomes unacceptable. The present study measures the levels of residual fertility in male and female irradiated Q‐flies at different irradiation doses (20, 30, 40, 50, 60 and 70 Gy), and investigates the possibility that fecundity and fertility increase between 10–15 and 30–35 days post emergence. Male flies require a higher dose than females to induce sterility, with no residual fertility found in females irradiated at doses of 50 Gy or above, and no residual fertility found in males irradiated at doses of 60 Gy or above. Irradiated females are more fecund at 30–35 days post emergence than at 10–15 days. However, fertility does not increase between 10 and 15 days post emergence and 30–35 days, even at doses below 50 Gy. The present study shows that there is scope to reduce the target sterilization dose for Q‐flies below that of the current dose range (70–75 Gy) at the same time as retaining an adequate safety margin above radiation doses at which residual fertility can be expected. 相似文献
107.
Young, A. J., Collins, J. C. and Russell, G. 1987. Solute regulationin the euryhaline marine alga Enteromorpha prolifera (O. F.Mll) J. Ag.J. exp. Bot. 38: 12981308. The physiological basis for salt tolerance has been studiedin the euryhaline alga Enteromorpha prolifera. Levels of inorganicions and organic (compatible) solutes have been measured. K+makes the major contribution towards the internal osmotic potentialof the cell, while Cl and, in particular, Na+ contentsare low. Levels of the organic solute ß-dimethylsulphonio-propionate(DMSP) are high but are fairly insensitive to changes in theexternal salinity. Levels of amino-acids, calcium, phosphateand sulphate contribute relatively little towards the internalosmotic potential of the alga. As salinity is altered there are marked changes in the tissuewater content and volume. These changes directly affect theconcentration of the osmotic solutes within the cell. In diluteseawaters there is an increase in turgor as there is littlechange in the internal solute content of the cell compared tovalues in normal sea water. Inorganic ions, in particular K+,and organic solutes are accumulated in concentrated seawaters,although concentrations greater than 2·00 x seawaterresult in a reduction in the internal osmotic potential of thecell, mainly through loss of K+. Key words: Enteromorpha, salinity, osmoregulation 相似文献
108.
Yeast hydrolysate supplement increases starvation vulnerability of Queensland fruit fly 总被引:1,自引:0,他引:1
PHILLIP W. TAYLOR MAHFUZA KHAN SAMUEL R. COLLINS OLIVIA L. REYNOLDS 《Physiological Entomology》2013,38(4):337-343
Post‐teneral diets containing yeast hydrolysate are reported to increase longevity, reproductive development and sexual performance of Queensland fruit fly (‘Q‐fly’) Bactrocera tryoni Froggatt (Diptera: Tephritidae). Consequently, diets including yeast hydrolysate are recommended for sterile Q‐flies before release in sterile insect technique (SIT) programmes. However, in some tephritids, diets including yeast hydrolysate are associated with an increased vulnerability to starvation. In the present study, the effects of yeast hydrolysate supplementation before release are considered with respect to the longevity of released Q‐fly when food becomes scarce. Experiments are carried out in three settings of varying resemblance to field conditions: 5‐L laboratory cages, 107‐L outdoor cages and 14 140‐L field cages containing potted citrus trees. In all experimental settings, compared with flies that received only sucrose, male and female Q‐flies that are provided with yeast hydrolysate during the first 2 days of adult life have a significantly shorter survival when subsequently deprived of food. Yeast supplementation appears to commit Q‐flies to a developmental trajectory that renders them more vulnerable to starvation. The practical significance of these findings for SIT depends on how often the releases are carried out under conditions in which Q‐flies experience extreme food shortages in the field. 相似文献
109.
Robert HS Kraus Anne Zeddeman Pim van Hooft Dmitry Sartakov Sergei A Soloviev Ronald C Ydenberg Herbert HT Prins 《BMC genetics》2011,12(1):1-15
Background
Yami and Ivatan islanders are Austronesian speakers from Orchid Island and the Batanes archipelago that are located between Taiwan and the Philippines. The paternal genealogies of the Yami tribe from 1962 monograph of Wei and Liu were compared with our dataset of non-recombining Y (NRY) chromosomes from the corresponding families. Then mitochondrial DNA polymorphism was also analyzed to determine the matrilineal relationships between Yami, Ivatan, and other East Asian populations.Results
The family relationships inferred from the NRY Phylogeny suggested a low number of paternal founders and agreed with the genealogy of Wei and Liu (P < 0.01). Except for one Y short tandem repeat lineage (Y-STR), seen in two unrelated Yami families, no other Y-STR lineages were shared between villages, whereas mtDNA haplotypes were indiscriminately distributed throughout Orchid Island. The genetic affinity seen between Yami and Taiwanese aborigines or between Ivatan and the Philippine people was closer than that between Yami and Ivatan, suggesting that the Orchid islanders were colonized separately by their nearest neighbors and bred in isolation. However a northward gene flow to Orchid Island from the Philippines was suspected as Yami and Ivatan peoples both speak Western Malayo-Polynesian languages which are not spoken in Taiwan. Actually, only very little gene flow was observed between Yami and Ivatan or between Yami and the Philippines as indicated by the sharing of mtDNA haplogroup B4a1a4 and one O1a1* Y-STR lineage.Conclusions
The NRY and mtDNA genetic information among Yami tribe peoples fitted well the patrilocal society model proposed by Wei and Liu. In this proposal, there were likely few genetic exchanges among Yami and the Philippine people. Trading activities may have contributed to the diffusion of Malayo-Polynesian languages among them. Finally, artifacts dating 4,000 YBP, found on Orchid Island and indicating association with the Out of Taiwan hypothesis might be related to a pioneering stage of settlement, as most dating estimates inferred from DNA variation in our data set ranged between 100-3,000 YBP. 相似文献110.
Robert HS Kraus Hindrik HD Kerstens Pim Van Hooft Richard PMA Crooijmans Jan J Van Der Poel Johan Elmberg Alain Vignal Yinhua Huang Ning Li Herbert HT Prins Martien AM Groenen 《BMC genomics》2011,12(1):150