全文获取类型
收费全文 | 530篇 |
免费 | 68篇 |
专业分类
598篇 |
出版年
2019年 | 11篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 13篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 22篇 |
2012年 | 18篇 |
2011年 | 14篇 |
2010年 | 9篇 |
2009年 | 13篇 |
2008年 | 14篇 |
2007年 | 15篇 |
2006年 | 13篇 |
2005年 | 16篇 |
2004年 | 15篇 |
2003年 | 12篇 |
2002年 | 14篇 |
2001年 | 18篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 11篇 |
1996年 | 5篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 14篇 |
1992年 | 11篇 |
1991年 | 10篇 |
1990年 | 17篇 |
1989年 | 10篇 |
1988年 | 19篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 12篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 16篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1974年 | 9篇 |
1973年 | 11篇 |
1972年 | 10篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1968年 | 5篇 |
1966年 | 6篇 |
排序方式: 共有598条查询结果,搜索用时 0 毫秒
591.
A Lactobacillus sp. was consistently isolated from dead and moribund postspawning brood stock rainbow trout. Pathology was characterized by massive chronic inflammation throughout the abdominal cavity and formation of pseudomembranes. The bacteria were most abundant in spent testes. Repeated handling was considered to be the major stressor leading to this infection and subsequent high mortality. 相似文献
592.
Synchronous cultures of the fission yeast Schizosaccharomyces pombe 972 h−1 are most sensitive to killing by 15 min, 49 °C pulses during a stage stretching from nuclear division through short G1 and S phases to a point early in G2. In this work the cell cycle position of the S phase has been altered by growing the cells in the presence of 2-phenylethanol. The heat sensitivity of these cells was greater at all stages of the cell cycle compared with the cells grown without 2-phenylethanol. However, the position of the most heat sensitive stage in the cell cycle was unaltered. This heat sensitive stage did not include S phase in the cells grown with 2-phenylethanol. 相似文献
593.
The chromatographic behavior of the rabbit uterine progesterone receptor interaction on several different hydrophobic matrices was characterized. Receptor, prepared in 0.6 M NaCl, exhibited a progressive retardation of elution, followed by retention, on a series of alkyl agarose columns as the length of the alkyl chain [(CH2)nH-] increased (n = 0-10), reflecting the presence of hydrophobic regions on the protein. Adsorption did not occur directly at the steroid binding site of the molecule and did not require activation to the DNA-binding form. Elution could be achieved by a decrease in the ionic strength of the buffer or the addition of glycerol, resulting in partial purification of receptor. Receptor bound tightly to phenyl agarose, although elution of the receptor under mild conditions (decreasing salt gradient, increasing glycerol gradient) resulted in poor yield and only modest purification. Passage of the non-activated progesterone receptor over Reactive Blue Sepharose effectively removed albumin, presumably by a hydrophobic interaction, although receptor was not retained. In the activated form, approximately 25% of receptor was bound to Reactive Blue Sepharose, reflecting an interaction of the Cibacron Blue dye with the polynucleotide binding site of the receptor. Hydrophobic chromatography may be an important adjunct to methods for purification of the progesterone receptor. 相似文献
594.
Intra-population patterns of phenotypic variation in biomass allocation to flower parts are analyzed for the treeIpomoea wolcottiana, and the effects of this variation on fruit production are evaluated in two consecutive years. Significant variation among individuals was found for biomass of both sexual and attractive structures. Repeatability values showed that variation in these structures could be heritable. Analyses of phenotypic natural selection indicated a positive directional selection for both, gynoecium and petals mass in both years. These results suggest that floral resource allocation can be modified by phenotypic natural selection. To our knowledge this is the first paper that reports phenotypic natural selection in floral characteristics of a tropical tree species. 相似文献
595.
596.
Stephen H. Bullock 《International journal of biometeorology》1997,41(1):13-16
Seasonal drought may limit primary productivity in most of the tropics, but the determinants of tree growth are not well
known. A 10-year study of the deciduous trees Cochlospermum vitifolium (Willd.) Spreng. (Cochlospermaceae) and Cnidoscolus spinosus Lundell (Euphorbiaceae) in southwestern México showed radial growth to be highly correlated (both r>0.85) only with precipitation during an interval of <2 months in the mid-wet season. Growth was not affected by total annual
precipitation or by an early starting or late ending of the wet season, or by heavy rainfall in the dry season. Annual mean
girth increments ranged from 0.03 to 3.31 cm and −0.1 to 2.01 cm, respectively. The best model for growth (r
2>0.85) was a linear combination of mid-summer precipitation (positive coefficient) and total precipitation over the previous
2 years (negative coefficient). Comparison with other species showed heterogeneous responses of wood production to climate
variation, and suggests that the range of functional types of dry forest trees is still unknown.
Received: 9 September 1996 / Accepted: 4 March 1997 相似文献
597.
598.