全文获取类型
收费全文 | 4189篇 |
免费 | 397篇 |
出版年
2021年 | 42篇 |
2020年 | 33篇 |
2018年 | 38篇 |
2016年 | 45篇 |
2015年 | 68篇 |
2014年 | 103篇 |
2013年 | 136篇 |
2012年 | 162篇 |
2011年 | 142篇 |
2010年 | 95篇 |
2009年 | 82篇 |
2008年 | 132篇 |
2007年 | 139篇 |
2006年 | 126篇 |
2005年 | 146篇 |
2004年 | 153篇 |
2003年 | 117篇 |
2002年 | 106篇 |
2001年 | 119篇 |
2000年 | 119篇 |
1999年 | 108篇 |
1998年 | 51篇 |
1997年 | 55篇 |
1996年 | 56篇 |
1995年 | 39篇 |
1994年 | 54篇 |
1993年 | 61篇 |
1992年 | 112篇 |
1991年 | 95篇 |
1990年 | 82篇 |
1989年 | 84篇 |
1988年 | 76篇 |
1987年 | 70篇 |
1986年 | 74篇 |
1985年 | 82篇 |
1984年 | 70篇 |
1983年 | 47篇 |
1982年 | 54篇 |
1981年 | 37篇 |
1980年 | 53篇 |
1979年 | 67篇 |
1978年 | 56篇 |
1977年 | 58篇 |
1976年 | 55篇 |
1975年 | 45篇 |
1974年 | 37篇 |
1973年 | 45篇 |
1972年 | 33篇 |
1969年 | 31篇 |
1966年 | 34篇 |
排序方式: 共有4586条查询结果,搜索用时 296 毫秒
161.
M E Watson 《Nucleic acids research》1984,12(13):5145-5164
162.
163.
Simultaneous RNA and DNA estimations were carried out during the cell cycle of EMT6/M/CC cells growing in vitro following synchronization by mitotic selection. the determinations were performed with a flow cytofluorimeter on individual cells stained with acridine orange. It was found that the RNA content increased during G1 then remained virtually constant between early and mid S phase, but a second increase occurred during late S. the rate of uptake of tritiated uridine paralleled these changes in RNA levels, and it was also found that the rate of uptake in metaphase and anaphase was virtually zero, but a rapid increase occurred in telophase. the increase in DNA during S was approximately linear, and the intermitotic phase and cycle durations were very similar to previously reported results. 相似文献
164.
Cell surface topography of Candida and Leucosporidium yeasts as revealed by scanning electron microscopy. 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The cell surface topography of the following yeast strains was examined by scanning electron microscopy: Candida slooffii, C. lipolytica, Leucosporidium frigidum, and L. nivalis. Multipolar and lateral budding were observed in the Candida yeasts in contrast to bipolar budding in the Leucosporidium species. The cell surface topography and the morphology of the bud and birth scars in these yeasts differed markedly. Apart from the bud and birth scars, the cells of C. slooffii showed a relatively smooth topography. The bud scars were seen as a circular ridge of wall material surrounding a markedly convex scar plug. Birth scars were raised, rounded structures, which appeared to distend upon cell growth. In contrast, bud scars of C. lipolytica were platelike, lacked a distinct annulus of wall material, and were much less protuberent than those of C. slooffii. Birth scars were a more permanent feature of these cells. The topography of Leucosporidium yeasts was characterized by the presence of numerous protrusions on the cell surface. In some cases, the entire cell surface was covered by these protrusions. There appeared to be some correlations between the age of the cell and the extent of surface protrusions and degree of surface convolution... 相似文献
165.
Possible mitochondrial involvement in mechanism of cytoplasmic male sterility in maize (Zea mays L.) 总被引:1,自引:0,他引:1
The mechanism of cytoplasmic male sterility was investigated in maize by isolating mitochondria from seedlings and various anther stages and analyzing cytochrome oxidase and succinic dehydrogenase biochemically and electrophoretically. Sterile anthers exhibited a lack of biochemical activity and fewer isozymatic bands for cytochrome oxidase. No apparent differences were detected biochemically or electrophoretically between fertile and sterile anthers for succinate dehydrogenase. 相似文献
166.
In mouse parotid acini both cholinergic and beta-adrenergic agonists increased intracellular levels of cyclic-GMP (c-GMP) as well as amylase release. The derivative of c-GMP, 8-bromo-c-GMP, mimicked the effects of cholinergic and beta-adrenergic stimulation on amylase release. Nitroprusside (NP), hydroxylamine (HA) and sodium azide (NaA) increased c-GMP levels and also enhanced amylase release in a dose-dependent manner; cyclic-AMP (c-AMP) levels were not affected. The phosphodiesterase inhibitor 3-isobutyl-1-methyl-xanthine (MIX) enhanced the effects of carbachol on both c-GMP accumulation and amylase release. These results suggest that c-GMP may mediate the actions of cholinergic agonists and at least partially mediate the actions of beta-adrenergic agonists on mouse parotid enzyme release. 相似文献
167.
168.
Leaves of greenhouse grown grasses had free protein amino acid contents of generally less than 5 % total amino acids, while field collected grasses averaged 14.7 % free protein amino acid contents. Taxonomic patterns are detectable in the total leaf amino acid profiles of grasses from both sources, those of pooids being distinguishable from those of chloridoids and panicoids, and those of danthonioids showing an intermediate pattern. Leaf profiles of Oryza, Stipeae, and Ehrharteae resemble one another, and are more like those of pooids than those of panicoids. Variations in Thr and Leu are apparently associated with differences in photosynthetic pathway. Grass leaves are generally low in total amino acid contents (2.2 ? 1.0 g % fr. wt), with Ile, Val and Met + Cys identified as the limiting essential amino acids. However, the nutritional ‘chemical scores’ of grass leaf proteins are high (75 %, based on the WHO scoring pattern). 相似文献
169.
An indirect estimate of the extent of branching of the olivary axons in the cerebellum in a marsupial (Trichosurus vulpecula) was carried out. The cells in the inferior olivary nuclear complex (IOC) of both sides were estimated (mean = 57,200), as were the cerebellar Purkinje cells (mean = 881,300). Assuming that all climbing fibers arise from IOC cells and that each Purkinje cell receives a climbing fiber input, each IOC cell sends climbing fiber terminals to 15 Purkinje cells. 相似文献
170.