全文获取类型
收费全文 | 860篇 |
免费 | 71篇 |
国内免费 | 1篇 |
出版年
2023年 | 11篇 |
2022年 | 16篇 |
2021年 | 21篇 |
2020年 | 13篇 |
2019年 | 12篇 |
2018年 | 16篇 |
2017年 | 13篇 |
2016年 | 28篇 |
2015年 | 48篇 |
2014年 | 57篇 |
2013年 | 69篇 |
2012年 | 83篇 |
2011年 | 62篇 |
2010年 | 40篇 |
2009年 | 27篇 |
2008年 | 64篇 |
2007年 | 44篇 |
2006年 | 48篇 |
2005年 | 40篇 |
2004年 | 40篇 |
2003年 | 41篇 |
2002年 | 30篇 |
2001年 | 14篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 9篇 |
1994年 | 6篇 |
1993年 | 5篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1976年 | 2篇 |
1975年 | 4篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1966年 | 2篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1961年 | 1篇 |
1955年 | 1篇 |
1944年 | 1篇 |
1926年 | 1篇 |
排序方式: 共有932条查询结果,搜索用时 31 毫秒
921.
The Bougner-Lambert law for the attenuation of solar energy was examined for selected wave bands in the visible portion of the solar spectrum: 700, 655, 610, 575, 500, 445 and 400 mµ. The energy reaching the earth's surface for these wave bands was found to follow the law. However, an analysis of the results showed considerable variability in the transmission coefficients even on clear days. This indicates that daily variations in the atmospheric constituents, presumably in the aerosal content, induces a real difference in light quality. When precise estimates of the spectral properties of solar energy are required by biologists, it will be necessary to obtain direct measurements. 相似文献
922.
Alfred W Boyle Victoria K Knight Max M Häggblom Lily Y Young 《FEMS microbiology ecology》1999,29(1):105-113
923.
924.
925.
Arthur B. Schneider Kirsten Fleischmann Lily Chu 《Biochimica et Biophysica Acta (BBA)/General Subjects》1985,838(3):329-334
In previous work we demonstrated that circulating thyroglobulin contains very little or no iodine. We have now characterized circulating thyroglobulin following administration of thyrotropin (TSH) to determine whether its iodine content remains low or increases after stimulation. The iodine content of circulating thyroglobulin was estimated from its density determined by equilibrium density gradient (isopycnic) centrifugation. TSH stimulated thyroglobulin from 182 ± 28 ng/ml to 571 ± 83 ng/ml at 8–14 h. Circulating thyroglobulin in the basal state had a density consistent with very little or no iodine. Its density increased following TSH to a maximum at 8–14 h which was nearly the same as the density of thyroglobulin extracted directly from the thyroid. To determine whether selective peripheral metabolism, based on the degree of iodination, could account for the density shift, purified rat thyroid thyroglobulin was injected into thyroidectomized rats. The density of thyroglobulin remained unchanged for 25 h during which time it was metabolized by more than 97%. Therefore, selective metabolism of thyroglobulin based on iodine content did not occur. We conclude that TSH causes a marked increase in the iodine content of circulating thyroglobulin. It is most likely that in the basal state circulating thyroglobulin comes from selective release of poorly iodinated molecules, while after TSH, it comes from release of previously synthesized, iodinated and stored molecules. 相似文献
926.
Mahapatra S. S. Navathe S. Mishra V. K. Chand R. 《Russian Journal of Plant Physiology》2021,68(6):1265-1275
Russian Journal of Plant Physiology - Spot blotch of wheat is an emerging threat that causes an annual yield loss of ~17%. The progression of the disease is believed to be dependent on the stage of... 相似文献
927.
The relative binding affinity in terms of ΔΔG bind-cald value of the antimalarial compound artemisinin-quinine hybrid is primarily
derived and is discussed in this article with reference to the ΔG bind-cald values of two known inhibitors Pepstatin-A and KNI-10006
complexed with HAP enzyme. The ΔG bind-cald value for KNI-10006 and Pepstatin-A is -14.10 kcal/mol and -13.09 kcal/mol
respectively. The MM-GB/SA scoring results in the relative binding energy (ΔΔG bind-cald) of the hybrid molecule with respect to
Pepstatin-A as 2.43 kcal/mol and 3.44 kcal/mol against KNI-10006. The overall binding mode of Art-Qui-OH resembles that of
Pepstatin-A binding in HAP active site. We suggest here that the ΔΔG bind-cald value & proposed binding mode of the Art-Qui-OH
for HAP enzyme should be considered for further structure-based drug design effort. 相似文献
928.
Lily Lee Salcedo Carl Franzblau 《In vitro cellular & developmental biology. Plant》1981,17(2):114-120
Summary This study describes the ability of aortic smooth muscle cells to synthesize and accumulate collagen with time in culture.
Inasmuch as smooth muscle cell cultures multilayer and continue to divide, albeit slowly, and can be maintained in the same
vessels where seeded for extended periods of time, a long-term aging study from a single subcultivated population of cells
was carried out. This is different from the usual cell-culture aging achieved by an increase in cell population doublings
obtained by repeated subcultivations. The latter process, which is trypsin induced, involves a changing cellular environment
including the extracellular matrix that is produced by the cells in culture.
Second subcultures of weanling rabbit, aortic media, smooth muscle cells maintained for different periods of time up to 14
wk displayed decreasing hydroxyproline formation with time. Proline hydroxylation was determined by pulsing these second-passage
cells with [14C]proline for 24 h at various times during the 14 wk period. The cell layer and medium were evaluated separately for radioactive
proline and hydroxyproline and the medium for bacterial collagenase-susceptible protein as well. The percent of hydroxylation
in the medium decreased from >31% within 1 wk after plating to 15.2% after 14 wk in culture. The percent of collagenase-susceptible
protein in the medium decreased in a comparable manner. The DNA levels increased during the entire period although initially
somewhat more rapidly. Accumulation of protein in the extracellular matrix continued during the 14-wk span. The accumulation
of hydroxyproline in the extracellular matrix also continued to increase throughout the culture period, but it did slow down
significantly. Yet the cells appear not to have lost their ability to accumulate connective tissue and protein in the insoluble
cell layer. The data suggest clearly that the percent collagen synthesis relative to total protein synthesis decreases in
the older cultures; total protein synthesis also decreases as expected.
This study was supported by NIH Program Projects AG00001 and HL 13262. 相似文献
929.
930.
Examination of the Harderian gland structure of the Black Sea bottlenose dolphin, Tursiops truncatus ponticus, at macroscopic, microscopic, and electron microscopic levels shows significant sexual dimorphism. The epithelial cells of male and female glands are different cell types, capable of producing chemically different products. Secretory cells in both sexes contain secretion granules that produce a secretion consisting mainly of proteins and carbohydrates, but thought to be sex-specific in composition. The female glands also contain lipid secretion granules. It is suggested that in the bottlenose dolphin the Harderian gland functions to produce sexually distinct pheromones and may have other physiological activities, e.g., participating in local immunological or endocrine-related reactions. © 1994 Wiley-Liss, Inc. 相似文献