全文获取类型
收费全文 | 1006篇 |
免费 | 140篇 |
国内免费 | 1篇 |
出版年
2021年 | 12篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 12篇 |
2016年 | 15篇 |
2015年 | 29篇 |
2014年 | 31篇 |
2013年 | 40篇 |
2012年 | 46篇 |
2011年 | 44篇 |
2010年 | 35篇 |
2009年 | 20篇 |
2008年 | 36篇 |
2007年 | 44篇 |
2006年 | 39篇 |
2005年 | 43篇 |
2004年 | 44篇 |
2003年 | 34篇 |
2002年 | 45篇 |
2001年 | 31篇 |
2000年 | 29篇 |
1999年 | 33篇 |
1998年 | 11篇 |
1997年 | 12篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 13篇 |
1993年 | 14篇 |
1992年 | 29篇 |
1991年 | 29篇 |
1990年 | 14篇 |
1989年 | 17篇 |
1988年 | 24篇 |
1987年 | 31篇 |
1986年 | 25篇 |
1985年 | 29篇 |
1984年 | 10篇 |
1983年 | 23篇 |
1982年 | 13篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1979年 | 14篇 |
1978年 | 19篇 |
1977年 | 10篇 |
1976年 | 8篇 |
1975年 | 12篇 |
1974年 | 13篇 |
1973年 | 10篇 |
1971年 | 6篇 |
1970年 | 10篇 |
排序方式: 共有1147条查询结果,搜索用时 15 毫秒
61.
Extracellular siderophores of rapidly growing Aspergillus nidulans and Penicillium chrysogenum 下载免费PDF全文
G Charlang R M Horowitz P H Lowy B Ng S M Poling N H Horowitz 《Journal of bacteriology》1982,150(2):785-787
The highly active extracellular siderophores previously detected in young cultures of Aspergillus nidulans and Penicillium chrysogenum have been identified as the cyclic ester fusigen (fusarinine C), and its open-chain form, fusigen B (fusarinine B). 相似文献
62.
Paul M. Horowitz 《Analytical biochemistry》1978,86(2):751-753
A new method for isolating crystalline bovine liver thiosulfate sulfurtransferase has been developed which relies on the selective binding of the enzyme to agarose-immobilized Cibacron Blue F3GA. This preparation has the advantages of simplicity, reproducibility, and rapidity. It is also suggested that the introduction of a binding and elution step will materially aid previously published procedures. 相似文献
63.
Isolation and identification of the conidial germination factor of Neurospora crassa. 总被引:9,自引:5,他引:4 下载免费PDF全文
The germination-essential substance (germination factor [GF]) that is lost from conidia of Neurospora crassa on exposure to solutions of low water activity has been isolated and identified as a group of iron-transport compounds, or siderochromes. The principal siderochrome of conidia is ferricrocin, a cyclic hexapeptide. A closely related substance, ferrichrome C, is tentatively identified as a minor constituent. The same substances are also present in extracts of mycelium along with small amounts of a third siderochrome, which has not been identified. The GF activity of culture filtrates is due to coprogen, the only siderochrome previously identified with N. crassa. 相似文献
64.
E.R. Berman J. Horowitz N. Segal S. Fisher L. Feeney-Burns 《Biochimica et Biophysica Acta (BBA)/General Subjects》1980,630(1):36-46
The kinetic properties and subcellular distribution of an esterifying enzyme in the pigment epithelium of bovine retina have been studied using both [1-3H]retinol and [3H]retinol bound to cellular retinol-binding protein as substrates. The most active esterifying fraction in pigment epithelial cell preparations was the microsomes, but the lysosome plus mitochondria fraction also showed some activity, probably due to endoplasmic reticulum present as an impurity. The microsomal enzyme showed optimum activity at pH 7.5, and the reaction was linear up to 30 μg protein and for the first 10–15 min. The apparent Km values were 16.6 · 10?6 and 5.5 · 10?6 M for [3H]retinol and bound [3H]retinol, respectively. This is the first time that retinol bound to cellular retinol-binding protein has been shown to undergo metabolic stransformation. The microsomal esterifying activity was destroyed by boiling for 1 min, or after freezing for 2 months. No clear requirement for ATP, CoA or fatty acid could be demonstrated.Of all the other tissues examined under the same experimental conditions as those used for the pigment epithelium, onlt intestine showed measurable activity. With larger amounts of tissue protein and longer incubation periods, activity was also detectable in microsomes of liver, testis and retina 相似文献
65.
66.
Ami Ketley Anne Warren Emily Holmes Martin Gering A. Aziz Aboobaker J. David Brook 《PloS one》2013,8(6)
The importance of microRNAs in development is now widely accepted. However, identifying the specific targets of individual microRNAs and understanding their biological significance remains a major challenge. We have used the zebrafish model system to evaluate the expression and function of microRNAs potentially involved in muscle development and study their interaction with predicted target genes. We altered expression of the miR-30 microRNA family and generated phenotypes that mimicked misregulation of the Hedgehog pathway. Inhibition of the miR-30 family increases activity of the pathway, resulting in elevated ptc1 expression and increased numbers of superficial slow-muscle fibres. We show that the transmembrane receptor smoothened is a target of this microRNA family. Our results indicate that fine coordination of smoothened activity by the miR-30 family allows the correct specification and differentiation of distinct muscle cell types during zebrafish embryonic development. 相似文献
67.
68.
69.
70.
Lucas K. Smith Evgenia Verovskaya Gregor Bieri Alana M. Horowitz Saskia N. I. von Ungern‐Sternberg Karin Lin Peter Seizer Emmanuelle Passegu Saul A. Villeda 《Aging cell》2020,19(8)
The aged systemic milieu promotes cellular and cognitive impairments in the hippocampus. Here, we report that aging of the hematopoietic system directly contributes to the pro‐aging effects of old blood on cognition. Using a heterochronic hematopoietic stem cell (HSC) transplantation model (in which the blood of young mice is reconstituted with old HSCs), we find that exposure to an old hematopoietic system inhibits hippocampal neurogenesis, decreases synaptic marker expression, and impairs cognition. We identify a number of factors elevated in the blood of young mice reconstituted with old HSCs, of which cyclophilin A (CyPA) acts as a pro‐aging factor. Increased systemic levels of CyPA impair cognition in young mice, while inhibition of CyPA in aged mice improves cognition. Together, these data identify age‐related changes in the hematopoietic system as drivers of hippocampal aging. 相似文献