全文获取类型
收费全文 | 954篇 |
免费 | 89篇 |
出版年
2024年 | 2篇 |
2023年 | 8篇 |
2022年 | 30篇 |
2021年 | 46篇 |
2020年 | 22篇 |
2019年 | 23篇 |
2018年 | 38篇 |
2017年 | 26篇 |
2016年 | 38篇 |
2015年 | 58篇 |
2014年 | 69篇 |
2013年 | 67篇 |
2012年 | 112篇 |
2011年 | 82篇 |
2010年 | 54篇 |
2009年 | 53篇 |
2008年 | 55篇 |
2007年 | 36篇 |
2006年 | 43篇 |
2005年 | 36篇 |
2004年 | 35篇 |
2003年 | 21篇 |
2002年 | 36篇 |
2001年 | 5篇 |
2000年 | 4篇 |
1999年 | 9篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1941年 | 1篇 |
1938年 | 1篇 |
1937年 | 2篇 |
1928年 | 1篇 |
1926年 | 2篇 |
排序方式: 共有1043条查询结果,搜索用时 15 毫秒
1.
2.
E. Janchen A. Ginzberger K. Redinger Elise Hofmann B. Schussnig Fr. Knoll 《Plant Systematics and Evolution》1937,86(3):227-238
Ohne Zusammenfassung 相似文献
3.
We hypothesized that manganese deficient animals fed high vs moderate levels of polyunsaturated fat would either manifest
evidence of increased oxidative stress or would experience compensatory changes in antioxidant enzymes and/or shifts in manganese
utilization that result in decreased endogenous gut manganese losses. Rats (females in Study 1, males in Study 2,n = 8/treatment) were fed diets that contained 5 or 20% corn oil by weight and either 0.01 or 1.5 μmol manganese/g diet. In
study 2,54Mn complexed to albumin was injected into the portal vein to assess gut endogenous losses of manganese. The manganese deficient
rats:
Gut endogenous losses of manganese tended to account for a smaller proportion of absorbed manganese in rats fed high-fat diets;
otherwise fat intake had few effects on tissue manganese concentrations. 相似文献
1. | Had 30–50% lower liver, tibia, kidney, spleen, and pancreas manganese concentrations than manganese adequate rats; |
2. | Conserved manganese through ≈70-fold reductions in endogenous fecal losses of manganese; |
3. | Had lower heart manganese superoxide dismutase (MnSOD) activity; and |
4. | Experienced only two minor compensatory changes in the activity of copper-zinc superoxide dismutase (CuZnSOD) and catalase. |
4.
Pedro F. P. Brandão-Dias Daniel M. C. Hallack Elise D. Snyder Jennifer L. Tank Diogo Bolster Sabrina Volponi Arial J. Shogren Gary A. Lamberti Kyle Bibby Scott P. Egan 《Molecular ecology resources》2023,23(4):756-770
Environmental DNA (eDNA) analysis is a powerful tool for remote detection of target organisms. However, obtaining quantitative and longitudinal information from eDNA data is challenging, requiring a deep understanding of eDNA ecology. Notably, if the various size components of eDNA decay at different rates, and we can separate them within a sample, their changing proportions could be used to obtain longitudinal dynamics information on targets. To test this possibility, we conducted an aquatic mesocosm experiment in which we separated fish-derived eDNA components using sequential filtration to evaluate the decay rate and changing proportion of various eDNA particle sizes over time. We then fit four alternative mathematical decay models to the data, building towards a predictive framework to interpret eDNA data from various particle sizes. We found that medium-sized particles (1–10 μm) decayed more slowly than other size classes (i.e., <1 and > 10 μm), and thus made up an increasing proportion of eDNA particles over time. We also observed distinct eDNA particle size distribution (PSD) between our Common carp and Rainbow trout samples, suggesting that target-specific assays are required to determine starting eDNA PSDs. Additionally, we found evidence that different sizes of eDNA particles do not decay independently, with particle size conversion replenishing smaller particles over time. Nonetheless, a parsimonious mathematical model where particle sizes decay independently best explained the data. Given these results, we suggest a framework to discern target distance and abundance with eDNA data by applying sequential filtration, which theoretically has both metabarcoding and single-target applications. 相似文献
5.
Elise Flipse Marja G. M. Schippers Elly M. Janssen Evert Jacobsen Richard G. F. Visser 《Molecular breeding : new strategies in plant improvement》1996,2(3):211-218
Theamylose-free (amf) potato mutant can easily be complemented through introduction of the wild-type gene coding for granule-bound starch synthase (GBSS). After iodine staining the starch of theamf mutant is red whereas that of the wild type and the complementedamf mutant is blue. The level of complementation of selected transformants and their sexual off-spring after backcrossing withamf was investigated using sporophytic tuber cells and gametophytic microspore cells. Two diploid and two tetraploid transformants with full complementation demonstrated the expected segregation patterns of 1:1 (one active insert) or 3:1 (two independently segregating active inserts) in the microspores and in the F1 offspring based on staining of tubers. All expected genotypes in the F1 generation were found, based on microspore segregation patterns of the individual F1 plants. Two transformants with partial complementation (mixed phenotypes) were investigated. One of them, B1, was tetraploid and duplex for the GBSS insert, which had originated through mitotic doubling of the transformed diploid cells. In the F1 generation three phenotypic classes were found:amf, fully complemented and partially complemented. The latter two classes exist independently of a simplex or duplex gene status. The second transformant with partial complementation, B10, appeared to have a complex molecular composition. One cluster of five transgenes caused the partial complementation. Fully and partially complemented phenotypic classes were found after crossing B10 with theamf mutant. Indications were found that the ploidy level of the tissue in which the genes were introduced and expressed played an important role. Firstly, partial complementation was found after transformation of the diploid and not of the tetraploidamf genotypes. Secondly, the level of complementation was higher in tissue with lower ploidy levels, as illustrated by the colour of the starch inin vitro tubers (2x–4x cells) versus field-grown tubers (16x–64x). 相似文献
6.
Sylvain Biquand Véronique Biquand-Guyot Ahmed Boug Jean-Pierre Gautier 《International journal of primatology》1992,13(5):533-543
Papio hamadryas was surveyed throughout its range in Saudi Arabia and was observed at altitudes ranging from 0 to 2300 m.
Wild populations occur along the whole range of altitude, while commensal populations are only found above 850 m altitude.
No variation in group size was found with altitude. Comparison of wild and commensal populations showed the following. (1)
Their composition in terms of age and sex classes, overall adult sex ratios, and group size does not significantly differ.
(2) Groups of both populations include, in similar proportions, three types of parties: one-male units (>70%), two-male units
(>13%), and a few other units of variable composition. (3) The mean size of commensal parties is significantly larger than
in the wild population; specifically one-male units are larger in the commensal population due to a larger number of females
per male. Thus, female distribution in commensal groups is more inequitable than that in wild groups. (4) Finally, the number
of females included in two-male units increases with altitude. These differences are discussed in terms of food availability
and predator pressure and are compared with results obtained on other Arabian and Ethiopian populations. 相似文献
7.
The distribution ofPapio hamadryas in Saudi Arabia: Ecological correlates and human influence 总被引:1,自引:0,他引:1
Sylvain Biquand Véronique Biquand-Guyot Ahmed Boug Jean-Pierre Gautier 《International journal of primatology》1992,13(3):223-243
We describe the distribution ofPapio hamadryas in Saudi Arabia in relation to ecological constraints and recent changes in human activities and land use. Baboons are present
only in the Sarawat and southern Hijaz mountains, which border the Red Sea in the southwestern region of the country. Our
distribution data confirms that their range, described as of 1981, should be extended 200 km northward, from 21°40N (Taif)
to 23°20N (Al Akhal). This new limit of range is not due to recent deployment of the baboons, but instead corrects inaccurate
surveys by previous reporters. Ecological factors that affect baboon distribution include low annual rainfall (less than 100
mm per yr), which limits baboon range in the north and east, and the absence of suitable sleeping cliffs in the coastal plain,
which limits their range in the west. Relative abundance is discussed in relation to vegetation and predator distribution.
Human influence is also significant: commensal troops persist near urban centers, while agricultural development reduces baboon
numbers in some regions. Habitat characteristics are discussed in comparison with similar data on the range of hamadryas in
Ethiopia. 相似文献
8.
Cointet Eva Séverin Elise Couzinet-Mossion Aurélie Méléder Vona Gonçalves Olivier Wielgosz-Collin Gaëtane 《Journal of applied phycology》2021,33(4):2093-2103
Journal of Applied Phycology - In recent years diatoms have emerged as a major algal source for the production of bioactive compounds. Marine diatoms grow quickly and can store high amount of... 相似文献
9.