全文获取类型
收费全文 | 3463篇 |
免费 | 313篇 |
出版年
2023年 | 20篇 |
2022年 | 48篇 |
2021年 | 67篇 |
2020年 | 51篇 |
2019年 | 52篇 |
2018年 | 114篇 |
2017年 | 87篇 |
2016年 | 136篇 |
2015年 | 183篇 |
2014年 | 216篇 |
2013年 | 231篇 |
2012年 | 326篇 |
2011年 | 271篇 |
2010年 | 179篇 |
2009年 | 173篇 |
2008年 | 204篇 |
2007年 | 193篇 |
2006年 | 162篇 |
2005年 | 154篇 |
2004年 | 127篇 |
2003年 | 127篇 |
2002年 | 110篇 |
2001年 | 42篇 |
2000年 | 49篇 |
1999年 | 45篇 |
1998年 | 38篇 |
1997年 | 36篇 |
1996年 | 33篇 |
1995年 | 26篇 |
1994年 | 14篇 |
1993年 | 12篇 |
1992年 | 12篇 |
1991年 | 16篇 |
1990年 | 16篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 11篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 13篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1974年 | 6篇 |
1973年 | 10篇 |
1957年 | 5篇 |
1956年 | 4篇 |
1935年 | 5篇 |
1918年 | 6篇 |
排序方式: 共有3776条查询结果,搜索用时 15 毫秒
21.
22.
C. Schüler J. Biala C. Bruns R. Gottschall S. Ahlers H. Vogtmann 《Journal of Phytopathology》1989,127(3):227-238
In pot experiments under controlled environmental conditions, composted organic household waste showed a suppression of soilborne plant pathogens. The addition of 8 %, 10 % and 30 % compost to the potting material which was artificially infested with Pythium ultimum or Rhizoctonia solani considerably reduced the incidence of disease in different varieties of host plants. It became evident that the degree of protection provided by compost depends upon the amount of compost added and upon the vulnerability of the host plant to infection. In an experiment using increasing levels of inoculum, the compost proved suppressive to the pathogen even under extreme disease conditions. This suppressive effect was still evident in compost which had been stored for prolonged periods. 相似文献
23.
Rolf Wichmann Christian Wandreg Joachim Große-Wiesmann 《Applied microbiology and biotechnology》1990,32(4):373-379
Summary Continuous production ofl-leucine was carried out withCorynebacterium glutamicum, strain ATCC 13032 starting from-ketoisocaproic acid as the precursor, glucose as the carbon source and ammonium sulphate as the nitrogen source, with biotin in a mineral medium. By means of cross-flow microfiltration or centrifugal separation for cell retention in continuous fermentation an increase in cell density was achieved and the product solution was obtained cell-free. The cells were concentrated to over 70 g cell dry mass/1. In experiments of up to 42 days, conversion rates of 85%–99% andl-leucine yields of 85%–93% were achieved. With a substrate residence time of 3.6 h, 114 mmol/1l-leucine was produced with a space-time yield of 97 g/1 per day. A scale-up of the fermentation volume from 4 to 1001 provided comparable results. 相似文献
24.
25.
Maria Reuter Margaretha K. S. Gustafsson Katja Mäntylä Cornelius J. P. Grimmelikhuijzen 《Zoomorphology》1996,116(3):111-122
The organization of the nervous system ofDendrocoelum lacteum (Tricladida, Paludicola, Dendrocelidae) andPolycelis tenuis (Tricladida, Paludicola, Planariidae) was studied by immunocytochemical double staining, using neuropeptide RFamide and serotonin
(5-HT) antisera on cryosections. The study confirmed the status of the main nerve cords (MCs) as the most important and stable
of the longitudinal cords and supported the hypothesis of a common phylogenetic origin of the MCs in flatworms. The ganglion-like
structures along the MCs at the beginning of transverse commissures and laterla branches showed a close contact with ventral
fibres of the submuscular nerve plexus indicating an origin from crossing points of insunken ring commissures. The distributional
pattern and morphology of the RFamide-IR cell bodies inD. lacteum corresponded to that of neurosecretory cells. Most RFamide-IR cells were unipolar and rounded while 5-HT-IR cells were uni-
bi- and multipolar. The neutropile consisted of a dense RFamide-IR and a loose 5-HT-IR network. RFamide dominated in all parts
of the genital plexus. 相似文献
26.
Significance of Ca2+ and K+ for the complex morphogenesis ofMicrasterias, which takes place through multipolar tip growth,was investigated. Studies with different external Ca2+ concentrationsand Ca2+ channel inhibitors LaCl3 and verapamil indicate thatCa2+ and Ca2+ channels are essential in the development, whiletreatments with different K+ concentrations and K+ channel inhibitorTEA demonstrate that potassium or K+ channels are not neededin the process, albeit the existence of K+ channels. K+ is notneeded even for the regulation of turgor pressure, which wasfound to decrease clearly during cell development. The plasmamembrane ATPase inhibitors diethylstilbesterol (DES) and Na-orthovanadatestop morphogenesis and indicate the importance of ion pumpsin the developmental process. Both supraoptimal, external K+and Ca2+ cause abundant Ca2+ precipitate formation in chloroplasts,which shows that chloroplasts are important in regulation ofcytoplasmic Ca2+ metabolism and that K+ activates the uptakeof Ca2+ through Ca2+ channels. (Received June 13, 1995; Accepted September 13, 1996) 相似文献
27.
Peter Salzer Gerhard Hebe Andreas Reith Barbara Zitterell-Haid Harald Stransky Katja Gaschler Achim Hager 《Planta》1996,198(1):118-126
Elicitors released from hyphae or cell walls of the ectomycorrhizal fungus Hebeloma crustuliniforme (Bull. ex Fries.) Quél. induced in suspension-cultured cells of Picea abies (L.) Karst. a set of fast reactions: (i) an immediate efflux of Cl– into the medium, followed by a K+ efflux; (ii) an influx of Ca2+ (measured as accumulation of 45Ca2+ in the cells); (iii) a phosphorylation of a 63-kDa protein and dephosphorylation of a 65-kDa protein (detectable by 4 min after elicitor application); (iv) an alkalinization of the medium, and (v) a transient synthesis of H2O2. The removal of extracellular Ca2+ by EGTA delayed the elicitor-induced alkalinization. A further reduction of this response could be achieved by TMB-8 an inhibitor of Ca2+ release from intracellular stores. Moreover, the inhibition of protein kinase activity by staurosporine prevented the extracellular alkalinization completely. However, the effectiveness of the elicitors in inducing the extracellular alkalinization was strongly impaired by constitutively secreted enzymes of spruce cells which cleaved the elicitors to inactive fragments. It is suggested that in ectomycorrhizae the efficacy of elicitors released from fungal cell walls is controlled by apoplastic enzymes of the host; the plant itself is able to reduce the activity of fungal elicitors on their way through the plant cell wall. But those elicitors which finally reach the plasma membrane of host cells induce reactions that are similar to the early defense reactions in plant-pathogen interactions.Abbreviations DW
dry weight
- FW
fresh weight
- TMB-8
3,4,5 trimethoxybenzoic acid 8-(diethylamino)-octyl ester
We thank Prof. M. Zenk (Universität München, Germany) for providing spruce cell cultures, and Dr. I. Kottke (Universität Tübingen, Germany) for isolates of Hebeloma crustuliniforme Tü 704. We are also thankful to Dr. W. Mayer (Universität Tübingen) for valuble discussions. This work was supported by Deutsche Forschungsgemeinschaft. B. Zitterell-Haid was financed by Graduiertenkolleg Interaktion in Waldökosystemen (supported by Deutsche Forschungsgemeinschaft) and G. Hebe by a scholarship of the Landesgraduiertenförderungsgesetz. 相似文献
28.
29.
R. Kempken A Preißmann W. Berthold 《Journal of industrial microbiology & biotechnology》1995,14(1):52-57
Summary Animal cells from 80-L and 2000-L fed batch fermentations were removed by a prototype disc stack centrifuge in order to achieve a fast and reliable separation of solids from large quantities of cell culture fluids. The clarification capacity was excellent for animal cells but particles remained in the liquid phase and affected further downstream processing of the cell-free harvest fluid. No significant loss of product was observed. A number of parameters were monitored to optimize process conditions for use with animal cells. 相似文献
30.
Different strains of Micrasterias (Chlorophyta, Conjugatophyceae); M. rotata (Grev.) Ralfs ex. Ralfs and M. denticulata Breb. ex. Ralfs var. angulosa (Hantzsch) W. & G. S. West from northern and southern Finland were treated with continuous illumination in order to study the cellular effects of the treatment and whether the tolerance to continuous light of the northern Finnish strains is related to the different daylenght conditions in northern and southern areas. During the growing season the Finnish strains normally live in long-day conditions or even in continuous light (between 60 and 70°N), and they also tolerated continuous illumination in the laboratory. Ultrastructural changes were found especially in the chloroplasts, where formation of calcium precipitates of different forms and sizes and also formation of plastoglobuli containing lipids appeared. However, even in 4-week treatments the ultrastructure of cells of these northern strains was not totally disrupted, contrary to what was found in southern M. torreyi , studied earlier. Southern and northern strains tolerated continuous illumination in different ways. They seem to differ from each other physiologically, and the differences are possibly located in their ionic metabolism and regulation. The injuries sustained during continuous illumination of Micrasterias may largely be caused by the accumulation of Ca2+ in cytoplasm and organelles, especially in the chloroplasts. 相似文献