全文获取类型
收费全文 | 1502篇 |
免费 | 166篇 |
出版年
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 12篇 |
2019年 | 15篇 |
2018年 | 22篇 |
2017年 | 25篇 |
2016年 | 17篇 |
2015年 | 51篇 |
2014年 | 54篇 |
2013年 | 68篇 |
2012年 | 66篇 |
2011年 | 70篇 |
2010年 | 54篇 |
2009年 | 56篇 |
2008年 | 67篇 |
2007年 | 69篇 |
2006年 | 59篇 |
2005年 | 61篇 |
2004年 | 64篇 |
2003年 | 63篇 |
2002年 | 44篇 |
2001年 | 51篇 |
2000年 | 47篇 |
1999年 | 27篇 |
1998年 | 23篇 |
1997年 | 21篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 19篇 |
1993年 | 18篇 |
1992年 | 32篇 |
1991年 | 23篇 |
1990年 | 26篇 |
1989年 | 24篇 |
1988年 | 29篇 |
1987年 | 29篇 |
1986年 | 26篇 |
1985年 | 21篇 |
1984年 | 16篇 |
1983年 | 21篇 |
1982年 | 19篇 |
1981年 | 16篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1977年 | 19篇 |
1976年 | 11篇 |
1974年 | 17篇 |
1973年 | 19篇 |
1972年 | 12篇 |
1971年 | 9篇 |
排序方式: 共有1668条查询结果,搜索用时 15 毫秒
61.
Summary HLA A and B antigens have been determined in 2740 adult responders to a population health survey in Busselton, Western Australia. HLA A B and C antigens have been determined in 481 schoolchildren. The antigen frequencies are generally close to those obtained elsewhere for subjects of British origin, but there are some differences from the frequencies found in North American Caucasians. The frequencies were not affected by the inclusion of genetically related individuals in the sample. Seventeen HLA A-B haplotypes, six A-C haplotypes and six B-C haplotypes had frequencies above 1%. A total of 1071 distinct phenotypes were identified out of the 5069 which are theoretically possible for the HLAA-B model used in the study. The most frequent phenotype was A2, B12 which occurred in 2.5% of the sample. 相似文献
62.
Shirley E. Hawkins 《Journal of theoretical biology》1976,62(2):299-313
Progress on various aspects of nucleic acids and protein synthesis in amoebae has been reviewed. The RNA molecules involved in the character changes seen after micro-injection of non-homologous cytoplasmic fractions have been isolated after polyacrylamide gel electrophoresis, and their approximate molecular weights calculated. Injection of these RNA molecules was shown to alter the response of recipient cells to growth in streptomycin and neomycin.The relative molecular weights of cytoplasmic ribosomal RNAs have been estimated using both aqueous and formamide gel electrophoresis. Some attempts to characterize the nuclear RNAs seen on aqueous polyacrylamide gels, and to evaluate this data with that published by other workers have been made. Results from assays of DNA- and RNA-directed DNA polymerase activity are considered in relation to those from other eukaryotes.Problems arising after attempts to use rabbit globin messenger RNA to direct globin synthesis in amoebae, and the possibilities of using minature gel systems and small cell numbers to identify proteins and RNAs after various experimental treatments are discussed. 相似文献
63.
The injection of non-homologous cytoplasm into any strain of large free-living amoebae leads to a 60% inhibition of division amongst recipient cells. When the post-microsomal supernatant fraction of Amoeba discoides was injected into A. proteus, this inhibition of division was as high as 95%. The incorporation of tritiated precursors, either [3H]uridine or 3H-amino acids, into these inhibited amoebae was studied at various times after the injection of the inhibitory material using autoradiography. When cells were grown in [3H]uridine, autoradiographs indicated that RNA synthesis had ceased 2 days after the injection of non-homologous material. However, if [3H]uridine was injected into the inhibited cells, some synthesis of RNA could be detected up to 4 days after the injection of inhibitor. These results suggested that uptake of [3H]uridine was impaired and that one site of action of the inhibitory molecules was RNA synthesis for membrane components. Experiments with a variety of 3H-amino acids suggested that protein synthesis continued for at least 9 days after the injection of non-homologous cytoplasm, and that in these cells some informational RNA molecules were long-lived. There seemed to be accumulation of material containing [3H]lysine in the nuclei of control cells taken at random from cultures, and this was seen in the nuclei of inhibited cells 1 day after injection. However, 2 days after the injection of inhibitor, no accumulation of [3H]lysine-containing material was found in the nuclei. 相似文献
64.
Agar gel electrophoresis and ultracentrifugation on continuous sucrose gradients revealed the presence of a 4S estradiol 'receptor' in cytosols of samples of human benign hyperplastic prostate tissue. High affinity (charcoal stability) and saturability (disappearance with excess competitor) binding characteristics of the molecular species concerned facilitated its clear distinction from similarly migrating serum albumin-steroid complexes. Our data, obtained with human serum, purified human albumin and albumin-enriched cytosol strongly suggest that agar gel electrophoresis, when used alone, may lack specificity for the quantification of estrogen 'receptors'. Radioligand binding to these molecules may be obscured by similarly migrating albumin-steroid complexes which fail to dissociate during electrophoresis. We advocate the inclusion of competitor experiments to improve the specificity of the method. 相似文献
65.
66.
Raquel Santos Jorge Troy R. Hawkins Edgar G. Hertwich 《The International Journal of Life Cycle Assessment》2012,17(1):9-15
Purpose
The purpose of this study is to provide life cycle inventory data and results for components of electrical grids to the larger community of life cycle assessment practitioners. This article is the first in a series of two, each focusing on different components of power grids. In part 1, the objects under scope are power lines and cables. Systems for overhead, underground, and subsea transmission are modeled here, including HVDC systems used in long-distance transmission. 相似文献67.
G Griziotis C Hawkins A G Mackinlay R H Crozier 《Australian journal of biological sciences》1987,40(2):171-180
Mitochondrial (mt) DNAs from 17 aboriginal Australians, predominantly from the coastal region of the Northern Territory were isolated and digested with four four-base restriction endonucleases, two of which revealed variation between samples. The observed fragment patterns were used directly in parsimony analyses of phylogenetic relationships between the samples, and were also converted to estimates of the number of substitutions per nucleotide position between samples (delta), which estimates were then used in distance analyses of phylogeny. The inferred fragment patterns of the completely sequenced 'Cambridge' human mtDNA were also included in these analyses. No strong evidence of geographic variation was found, consistent with previous findings of Australian aborigines and other humans generally, although the most divergent sample was one of two from Sydney, indicating that further work is desirable. The estimate of mean difference between samples (diversity), 0.0017 +/- 0.0003 (mean +/- 95% confidence interval), is significantly lower than that reported previously for humans generally. 相似文献
68.
Hollis J. Hawkins Alan G.E. Wilson Marshall W. Anderson Thomas E. Eling 《Prostaglandins & other lipid mediators》1977,14(2):251-259
We have investigated the uptake and subsequent metabolism of the prostaglandins (PGs) PGE1, PGA1, and PGB1 by rat, guinea pig and rabbit isolated perfused lungs (IPL). Significant species differences were not observed in the uptake or metabolism of any PG on passage through the IPL. However, differences in the uptake of PGA1 and PGB1 and in the metabolism of PGA1 were observed with a given species when the composition of the perfusion medium was varied. The IPL removed minimal amounts (<20% of the supply rate) of PGA1 and PGB1 from the circulation when the perfusate contained 4.5% bovine serum albumin (BSA). In the absence of BSA, however, both PGA1 and PGB1 were substantially removed from circulation (~53% of the supply rate) and PGA1 was also metabolized. The composition of the perfusate had no effect on the uptake and metabolism of PGE1 which was always taken up and metabolized to a greater extent than was PGA1 and PGB1. Thus, the apparent species differences previously reported for the pulmonary biotransformation of PGA can result from differences in the perfusion medium used. Our data suggest that both plasma protein binding and a transport system play important roles in determining the selectivity of the uptake of PGs by the lung. 相似文献
69.
70.
Popper Arthur N. Hawkins Anthony D. Jacobs Fred Jacobson Paul T. Johnson Peter Krebs Justin 《Reviews in Fish Biology and Fisheries》2020,30(4):605-622
Reviews in Fish Biology and Fisheries - Downstream movements of some freshwater fishes, including eels, are adversely affected by the presence of hydroelectric structures and other anthropic... 相似文献