全文获取类型
收费全文 | 313篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
系统科学 | 2篇 |
理论与方法论 | 4篇 |
现状及发展 | 232篇 |
研究方法 | 6篇 |
综合类 | 68篇 |
自然研究 | 3篇 |
出版年
2018年 | 3篇 |
2017年 | 5篇 |
2013年 | 3篇 |
2012年 | 4篇 |
2011年 | 12篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 8篇 |
2004年 | 6篇 |
2003年 | 14篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1992年 | 3篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 11篇 |
1978年 | 4篇 |
1977年 | 13篇 |
1976年 | 5篇 |
1975年 | 5篇 |
1974年 | 4篇 |
1973年 | 5篇 |
1972年 | 9篇 |
1971年 | 13篇 |
1970年 | 12篇 |
1969年 | 9篇 |
1968年 | 7篇 |
1967年 | 11篇 |
1966年 | 10篇 |
1965年 | 7篇 |
1964年 | 6篇 |
1963年 | 4篇 |
1961年 | 7篇 |
1960年 | 3篇 |
1959年 | 5篇 |
1958年 | 4篇 |
1957年 | 3篇 |
1956年 | 2篇 |
1955年 | 2篇 |
1954年 | 4篇 |
1948年 | 2篇 |
1947年 | 7篇 |
1946年 | 6篇 |
1945年 | 4篇 |
排序方式: 共有315条查询结果,搜索用时 15 毫秒
61.
Ch. P. F. Redfern 《Cellular and molecular life sciences : CMLS》1986,42(3):307-309
Summary Brain-ring glands fromDrosophila larvae reared on a defined diet containing campesterol (24-methyl-cholesterol) as the major sterol, secreted-in addition to ecdysone-a compound identified previously as a 24-methyl analogue, 20-deoxy-makisterone A. Using ergosterol or cholesterol as the sterol component of the diet, only ecdysone was detectable in cultures of brain-ring glands. 相似文献
62.
63.
W. Scherrer Ch. J. Bernard A. M. Monnier 《Cellular and molecular life sciences : CMLS》1946,2(11):463-465
64.
M. R. Michel M. Elgizoli H. Koblet Ch. Kempf 《Cellular and molecular life sciences : CMLS》1988,44(3):199-203
Summary Using the suspension cell line P3X63 Ag8 we have studied the impact of the composition of the diffusion medium on cellular protein synthesis under standard electroporation conditions in TBS-Na. This buffer contains the high saline concentration usually present in electroporation-mediated DNA transfection. Electroporation in the presence of TBS-Na resulted in an immediate shut-off of protein synthesis, even though both FITC-dextran (Mr 40 kD) and Semliki Forest virus core protein (Mr 33 kD) were incorporated efficiently into the cytoplasm across the electropores at 0°C. Subsequent resealing of the pores was completed after a 5-min incubation at 37°C. When compared with control cells, overall protein synthesis of electroporated cells recovered slowly to resume a 30% activity after 1 h of incubation at 37°C. We have determined optimal conditions for diffusion loading (which necessitates the presence of ATP, GTP, amino acids, K+, Mg2+, and Ca2+) and resealing (in the presence of K+, Mg2+, and Ca2+), leading to a full and lasting recovery of protein synthesis within 5 min after pore closure. 相似文献
65.
Chronic oral exposure of mice to Cd++ inhibits cell-mediated immunity of delayed type hypersensitivity induced by sheep red blood cells (SRBC). No effect was detected on humoral immune response to SRBC. Spleen cells derived from mice exposed to Cd++ showed in vitro enhanced response to T and B cell mitogens. These results demonstrate that Cd++ exposure alters the immune system of mice. 相似文献
66.
Analysis of one million base pairs of Neanderthal DNA 总被引:1,自引:0,他引:1
Green RE Krause J Ptak SE Briggs AW Ronan MT Simons JF Du L Egholm M Rothberg JM Paunovic M Pääbo S 《Nature》2006,444(7117):330-336
Neanderthals are the extinct hominid group most closely related to contemporary humans, so their genome offers a unique opportunity to identify genetic changes specific to anatomically fully modern humans. We have identified a 38,000-year-old Neanderthal fossil that is exceptionally free of contamination from modern human DNA. Direct high-throughput sequencing of a DNA extract from this fossil has thus far yielded over one million base pairs of hominoid nuclear DNA sequences. Comparison with the human and chimpanzee genomes reveals that modern human and Neanderthal DNA sequences diverged on average about 500,000 years ago. Existing technology and fossil resources are now sufficient to initiate a Neanderthal genome-sequencing effort. 相似文献
67.
Proteome survey reveals modularity of the yeast cell machinery 总被引:4,自引:0,他引:4
Gavin AC Aloy P Grandi P Krause R Boesche M Marzioch M Rau C Jensen LJ Bastuck S Dümpelfeld B Edelmann A Heurtier MA Hoffman V Hoefert C Klein K Hudak M Michon AM Schelder M Schirle M Remor M Rudi T Hooper S Bauer A Bouwmeester T Casari G Drewes G Neubauer G Rick JM Kuster B Bork P Russell RB Superti-Furga G 《Nature》2006,440(7084):631-636
Protein complexes are key molecular entities that integrate multiple gene products to perform cellular functions. Here we report the first genome-wide screen for complexes in an organism, budding yeast, using affinity purification and mass spectrometry. Through systematic tagging of open reading frames (ORFs), the majority of complexes were purified several times, suggesting screen saturation. The richness of the data set enabled a de novo characterization of the composition and organization of the cellular machinery. The ensemble of cellular proteins partitions into 491 complexes, of which 257 are novel, that differentially combine with additional attachment proteins or protein modules to enable a diversification of potential functions. Support for this modular organization of the proteome comes from integration with available data on expression, localization, function, evolutionary conservation, protein structure and binary interactions. This study provides the largest collection of physically determined eukaryotic cellular machines so far and a platform for biological data integration and modelling. 相似文献
68.
Essential role for the peroxiredoxin Prdx1 in erythrocyte antioxidant defence and tumour suppression 总被引:2,自引:0,他引:2
Neumann CA Krause DS Carman CV Das S Dubey DP Abraham JL Bronson RT Fujiwara Y Orkin SH Van Etten RA 《Nature》2003,424(6948):561-565
Reactive oxygen species are involved in many cellular metabolic and signalling processes and are thought to have a role in disease, particularly in carcinogenesis and ageing. We have generated mice with targeted inactivation of Prdx1, a member of the peroxiredoxin family of antioxidant enzymes. Here we show that mice lacking Prdx1 are viable and fertile but have a shortened lifespan owing to the development beginning at about 9 months of severe haemolytic anaemia and several malignant cancers, both of which are also observed at increased frequency in heterozygotes. The haemolytic anaemia is characterized by an increase in erythrocyte reactive oxygen species, leading to protein oxidation, haemoglobin instability, Heinz body formation and decreased erythrocyte lifespan. The malignancies include lymphomas, sarcomas and carcinomas, and are frequently associated with loss of Prdx1 expression in heterozygotes, which suggests that this protein functions as a tumour suppressor. Prdx1-deficient fibroblasts show decreased proliferation and increased sensitivity to oxidative DNA damage, whereas Prdx1-null mice have abnormalities in numbers, phenotype and function of natural killer cells. Our results implicate Prdx1 as an important defence against oxidants in ageing mice. 相似文献
69.
Compartments revealed in food-web structure 总被引:1,自引:0,他引:1
Compartments in food webs are subgroups of taxa in which many strong interactions occur within the subgroups and few weak interactions occur between the subgroups. Theoretically, compartments increase the stability in networks, such as food webs. Compartments have been difficult to detect in empirical food webs because of incompatible approaches or insufficient methodological rigour. Here we show that a method for detecting compartments from the social networking science identified significant compartments in three of five complex, empirical food webs. Detection of compartments was influenced by food web resolution, such as interactions with weights. Because the method identifies compartmental boundaries in which interactions are concentrated, it is compatible with the definition of compartments. The method is rigorous because it maximizes an explicit function, identifies the number of non-overlapping compartments, assigns membership to compartments, and tests the statistical significance of the results. A graphical presentation reveals systemic relationships and taxa-specific positions as structured by compartments. From this graphic, we explore two scenarios of disturbance to develop a hypothesis for testing how compartmentalized interactions increase stability in food webs. 相似文献
70.