全文获取类型
收费全文 | 911篇 |
免费 | 98篇 |
出版年
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 13篇 |
2018年 | 12篇 |
2016年 | 24篇 |
2015年 | 24篇 |
2014年 | 21篇 |
2013年 | 43篇 |
2012年 | 46篇 |
2011年 | 36篇 |
2010年 | 20篇 |
2009年 | 21篇 |
2008年 | 36篇 |
2007年 | 30篇 |
2006年 | 25篇 |
2005年 | 22篇 |
2004年 | 23篇 |
2003年 | 36篇 |
2002年 | 28篇 |
2001年 | 27篇 |
2000年 | 22篇 |
1999年 | 13篇 |
1998年 | 9篇 |
1997年 | 11篇 |
1996年 | 15篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 17篇 |
1991年 | 16篇 |
1990年 | 18篇 |
1989年 | 15篇 |
1988年 | 30篇 |
1987年 | 17篇 |
1986年 | 21篇 |
1985年 | 22篇 |
1984年 | 15篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1974年 | 9篇 |
1973年 | 11篇 |
1972年 | 7篇 |
1971年 | 7篇 |
1969年 | 6篇 |
1967年 | 8篇 |
排序方式: 共有1009条查询结果,搜索用时 15 毫秒
181.
182.
183.
184.
185.
186.
187.
D. Craig Sheppard G. Larry Newton Sidney A. Thompson Stan Savage 《Bioresource technology》1994,50(3):275-279
A manure management system for laying hens using the black soldier fly, Hermetia illucens (L.) converted manure to a 42% protein, 35% fat feedstuff, reduced manure accumulation by at least 50% and eliminated house fly breeding. No extra facility or added energy was required. Mature larvae self-harvested producing a feedstuff as they attempted to pupate. Optimal feedstuff to manure dry matter yield was 7·8%. This insect occurs worldwide in tropical and warm-temperature regions and can digest many biological wastes. 相似文献
188.
Ian G. Kinahan Alex K. Baranowski Elizabeth R. Whitney Suzanne K. Savage Chad M. Rigsby Emma E. Shoemaker Colin M. Orians Evan L. Preisser 《Ecological Entomology》2020,45(3):416-422
1. Interactions between invertebrate herbivores with different feeding modes are common on long-lived woody plants. In cases where one herbivore facilitates the success of another, the consequences for their shared host plant may be severe. Eastern hemlock (Tsuga canadensis), a canopy-dominant conifer native to the eastern U.S., is currently threatened with extirpation by the invasive stylet-feeding hemlock woolly adelgid (Adelges tsugae). The effect of adelgid on invasive hemlock-feeding folivores remains unknown. 2. This study evaluated the impact of feeding by hemlock woolly adelgid on gypsy moth (Lymantria dispar) larval preference for, and performance on, eastern hemlock. To assess preference, 245 field-grown hemlocks were surveyed for gypsy moth herbivory damage and laboratory paired-choice bioassays were conducted. To assess performance, gypsy moth larvae were reared to pupation on adelgid-infested or uninfested hemlock foliage, and pupal weight, proportional weight gain, and larval period were analysed. 3. Adelgid-infested hemlocks experienced more gypsy moth herbivory than did uninfested control trees, and laboratory tests confirmed that gypsy moth larvae preferentially feed on adelgid-infested hemlock foliage. Gypsy moth larvae reared to pupation on adelgid-infested foliage gained more weight than larvae reared on uninfested control foliage. 4. These results suggest that the synergistic effect of adelgid and gypsy moth poses an additional threat to eastern hemlock that may increase extirpation risk and ecological impact throughout most of its range. 相似文献
189.
A breeding colony of cotton-top tamarins is described where 91% of the breeding females are from the first and second laboratory-born generations, and whose infants have a one year survival rate of 62%. Mortality is greatest in the first week of life, and mortality rate is greater for a female's first litter than for subsequent litters. Females without early experience in caring for other infants have a higher infant mortality rate than females with such experience. No seasonal birth patterns have been observed. Large complex cages with food, water and runways located in the upper half of the cage, high protein diets and reduced handling of animals are suggested as additional variables affecting breeding success. 相似文献
190.
Stability of enterocytes and certain enzymatic activities in suspensions of cells from the villous tip to the crypt of Lieberkühn of the mouse small intestine. 下载免费PDF全文
A series of studies in this laboratory have focused on how an indigenous microbiota influences the activities of alkaline phosphatase, phosphodiesterase I, and thymidine kinase in the enterocytes of the upper small intestine of mice. To draw conclusions about the role of the microflora in determining levels of enzymatic activity, we found it necessary to develop a procedure by which cell suspensions could be obtained containing enterocytes isolated sequentially from the villous tip to the crypt of Lieberkühn. The procedure was modified from the one developed for rats by Weiser (J. Biol. Chem. 248:2536-2541, 1973), involved a minimum number of interfering factors (e.g., proteolytic enzymes and mechanical agitation), and worked reproducibly for mice. During development of the procedure, some variables affecting the assays of the enzymes known to be present in enterocytes were also explored. Rods to which were tied everted segments of gut were incubated in a series of tubes containing a solution of EDTA the concentration of which was changed from 1.5 to 5.0 mM, thus giving a greater yield of enterocytes at every step. The cells incubating in the chelating solution were most stable when 0.23 M sucrose was included in the EDTA solutions. Success in assaying enzymatic activities in the cell suspensions depended on (i) how the cells were isolated, (ii) the assay procedure for thymidine kinase, and (iii) whether cellular suspensions or extracts were assayed. 相似文献