全文获取类型
收费全文 | 1186篇 |
免费 | 146篇 |
出版年
2021年 | 11篇 |
2020年 | 7篇 |
2019年 | 14篇 |
2018年 | 16篇 |
2017年 | 9篇 |
2016年 | 16篇 |
2015年 | 45篇 |
2014年 | 34篇 |
2013年 | 78篇 |
2012年 | 90篇 |
2011年 | 55篇 |
2010年 | 48篇 |
2009年 | 37篇 |
2008年 | 52篇 |
2007年 | 63篇 |
2006年 | 69篇 |
2005年 | 60篇 |
2004年 | 63篇 |
2003年 | 46篇 |
2002年 | 52篇 |
2001年 | 19篇 |
2000年 | 21篇 |
1999年 | 22篇 |
1998年 | 17篇 |
1997年 | 12篇 |
1996年 | 20篇 |
1995年 | 17篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 15篇 |
1991年 | 19篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 13篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 14篇 |
1984年 | 16篇 |
1983年 | 15篇 |
1982年 | 13篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 11篇 |
1977年 | 16篇 |
1976年 | 8篇 |
1974年 | 16篇 |
1973年 | 10篇 |
1972年 | 10篇 |
1971年 | 11篇 |
1970年 | 7篇 |
排序方式: 共有1332条查询结果,搜索用时 31 毫秒
951.
952.
Linda Olsvig-Whittaker Piet Schipper Ignas Heitkonig Yonat Magal Reuven Ortal Eyal Shy Karle Sýkora 《应用植被学》1999,2(1):125-130
Abstract. Conservation management has significant gaps between (1) collection and storage of biological data, (2) data analysis, and (3) application of results. In order to improve management decision-making, it is necessary to bridge these gaps. One of the most promising approaches uses computer-based decision support systems (DSS): interactive models of the system in question—for example, a nature reserve. One kind of DSS is scenario modeling: spatially-based models which (1) use expert opinion and data on vegetation, geology, hydrology, and management, (2) to project changes in landscape through time, (3) on the basis of changes in driving environmental factors. Scenario models are essentially graphic hypotheses, predicting changes in landscape with a specified change in driving factors, which can then be verified or falsified by monitoring. This paper presents an application of this approach to an Israeli nature reserve, the En Afeq Reserve in western Galilee. Our project tests the possibility of improving Israeli conservation management by using methods now standard for nature reserves in the Netherlands. 相似文献
953.
Cloning of the Human Cytomegalovirus (HCMV) Genome as an Infectious Bacterial Artificial Chromosome in Escherichia coli: a New Approach for Construction of HCMV Mutants 总被引:4,自引:0,他引:4
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Eva-Maria Borst Gabriele Hahn Ulrich H. Koszinowski Martin Messerle 《Journal of virology》1999,73(10):8320-8329
We have recently introduced a novel procedure for the construction of herpesvirus mutants that is based on the cloning and mutagenesis of herpesvirus genomes as infectious bacterial artificial chromosomes (BACs) in Escherichia coli (M. Messerle, I. Crnkovic, W. Hammerschmidt, H. Ziegler, and U. H. Koszinowski, Proc. Natl. Acad. Sci. USA 94:14759-14763, 1997). Here we describe the application of this technique to the human cytomegalovirus (HCMV) strain AD169. Since it was not clear whether the terminal and internal repeat sequences of the HCMV genome would give rise to recombination, the stability of the cloned HCMV genome was examined during propagation in E. coli, during mutagenesis, and after transfection in permissive fibroblasts. Interestingly, the HCMV BACs were frozen in defined conformations in E. coli. The transfection of the HCMV BACs into human fibroblasts resulted in the reconstitution of infectious virus and isomerization of the reconstituted genomes. The power of the BAC mutagenesis procedure was exemplarily demonstrated by the disruption of the gpUL37 open reading frame. The transfection of the mutated BAC led to plaque formation, indicating that the gpUL37 gene product is dispensable for growth of HCMV in fibroblasts. The new procedure will considerably speed up the construction of HCMV mutants and facilitate genetic analysis of HCMV functions. 相似文献
954.
Mette Mauritzen Piet. J. M. Bergers Harry P. Andreassen Harry Bussink Rutger Barendse 《Journal of Applied Ecology》1999,36(3):409-421
1. Ditches are often connected to root vole habitat patches (i.e. moist reed patches) in the Netherlands. Due to the linear structure of ditches and because ditch habitat is qualitatively similar to root vole habitat patches, we hypothesized that ditches could function as habitat corridors facilitating dispersal movement of root voles. In order to test this hypothesis, we radiotracked root voles released in a landscape novel to them, consisting of ditches and agricultural meadows.
2. Agricultural meadows often surround the marsh patches inhabited by root voles. As the meadows are mowed regularly, we included the length of the meadow vegetation as an experimental factor in the study.
3. Assuming that ditches function as habitat corridors, we expected root voles in the ditches to move faster and more unidirectionally than root voles in the meadows, and to prefer the ditches to meadows.
4. We found that the ditches did not facilitate faster movements than the meadows. Although the root voles moved back and forth within the ditches, they showed a more directional movement pattern than the root voles in the meadows. Furthermore, the root voles preferred the ditch habitat irrespective of the vegetative cover in the meadow.
5. We conclude that ditches could function as habitat corridors for root voles, as they preferred to move in ditches when in unfamiliar areas. 相似文献
2. Agricultural meadows often surround the marsh patches inhabited by root voles. As the meadows are mowed regularly, we included the length of the meadow vegetation as an experimental factor in the study.
3. Assuming that ditches function as habitat corridors, we expected root voles in the ditches to move faster and more unidirectionally than root voles in the meadows, and to prefer the ditches to meadows.
4. We found that the ditches did not facilitate faster movements than the meadows. Although the root voles moved back and forth within the ditches, they showed a more directional movement pattern than the root voles in the meadows. Furthermore, the root voles preferred the ditch habitat irrespective of the vegetative cover in the meadow.
5. We conclude that ditches could function as habitat corridors for root voles, as they preferred to move in ditches when in unfamiliar areas. 相似文献
955.
956.
The fibronectin binding proteins of Staphylococcus aureus are required for adhesion to and invasion of bovine mammary gland cells 总被引:5,自引:0,他引:5
We recently described adhesion to and invasion of bovine mammary gland cells by Staphylococcus aureus in vitro. Here, we show that the levels of adhesion and invasion are dependent on the bacterial growth phase and are controlled by the agr locus. Incubation of exponential growth phase cells of S. aureus with mammary gland cells resulted in bacterial cell clumping. Strains of S. aureus deficient in expression of the fibronectin binding proteins (FnBPA and FnBPB) failed to clump and their ability to adhere to and to invade the bovine mammary gland cells is strongly reduced. This indicates that the fibronectin binding proteins are essential for S. aureus adhesion to and invasion of bovine mammary gland cells. 相似文献
957.
Viktoria Reithofer Jordan Fernndez-Pereira María Alvarado Piet de Groot Lars-Oliver Essen 《PLoS pathogens》2021,17(12)
Candida glabrata is an opportunistic pathogenic yeast frequently causing infections in humans. Though it lacks typical virulence factors such as hyphal development, C. glabrata contains a remarkably large and diverse set of putative wall adhesins that is crucial for its success as pathogen. Here, we present an analysis of putative adhesins from the homology clusters V and VI. First, sequence similarity network analysis revealed relationships between cluster V and VI adhesins and S. cerevisiae haze protective factors (Hpf). Crystal structures of A-regions from cluster VI adhesins Awp1 and Awp3b reveal a parallel right-handed β-helix domain that is linked to a C-terminal β-sandwich. Structure solution of the A-region of Awp3b via single wavelength anomalous diffraction phasing revealed the largest known lanthanide cluster with 21 Gd3+ ions. Awp1-A and Awp3b-A show structural similarity to pectate lyases but binding to neither carbohydrates nor Ca2+ was observed. Phenotypic analysis of awp1Δ, awp3Δ, and awp1,3Δ double mutants did also not confirm their role as adhesins. In contrast, deletion mutants of the cluster V adhesin Awp2 in the hyperadhesive clinical isolate PEU382 demonstrated its importance for adhesion to polystyrene or glass, biofilm formation, cell aggregation and other cell surface-related phenotypes. Together with cluster III and VII adhesins our study shows that C. glabrata CBS138 can rely on a set of 42 Awp1-related adhesins with β-helix/α-crystallin domain architecture for modifying the surface characteristics of its cell wall. 相似文献
958.
Sara Roose Russell W. Avramenko Stephen M. J. Pollo James D. Wasmuth Shaali Ame Mio Ayana Martha Betson Piet Cools Daniel Dana Ben P. Jones Zeleke Mekonnen Arianna Morosetti Abhinaya Venkatesan Johnny Vlaminck Matthew L. Workentine Bruno Levecke John S. Gilleard Peter Geldhof 《PLoS neglected tropical diseases》2021,15(9)
959.
960.
The mitochondrial genome of yeast. 总被引:51,自引:0,他引:51