全文获取类型
收费全文 | 754篇 |
免费 | 64篇 |
出版年
2023年 | 3篇 |
2022年 | 14篇 |
2021年 | 12篇 |
2020年 | 12篇 |
2019年 | 15篇 |
2018年 | 16篇 |
2017年 | 9篇 |
2016年 | 18篇 |
2015年 | 33篇 |
2014年 | 44篇 |
2013年 | 53篇 |
2012年 | 62篇 |
2011年 | 69篇 |
2010年 | 36篇 |
2009年 | 36篇 |
2008年 | 59篇 |
2007年 | 52篇 |
2006年 | 38篇 |
2005年 | 40篇 |
2004年 | 38篇 |
2003年 | 35篇 |
2002年 | 27篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 2篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 1篇 |
1992年 | 6篇 |
1990年 | 8篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1963年 | 2篇 |
1953年 | 1篇 |
排序方式: 共有818条查询结果,搜索用时 46 毫秒
121.
Laurent Schild Estelle Schneeberger Ivan Gautschi Dmitri Firsov 《The Journal of general physiology》1997,109(1):15-26
The amiloride-sensitive epithelial Nachannel (ENaC) is a heteromultimeric channel made of three αβγ subunits. The structures involved in the ion permeation pathway have only been partially identified, and the respective contributions of each subunit in the formation of the conduction pore has not yet been established. Using a site-directed mutagenesis approach, we have identified in a short segment preceding the second membrane-spanning domain (the pre-M2 segment) amino acid residues involved in ion permeation and critical for channel block by amiloride. Cys substitutions of Gly residues in β and γ subunits at position βG525 and γG537 increased the apparent inhibitory constant (K
i) for amiloride by >1,000-fold and decreased channel unitary current without affecting ion selectivity. The corresponding mutation S583 to C in the α subunit increased amiloride K
i by 20-fold, without changing channel conducting properties. Coexpression of these mutated αβγ subunits resulted in a nonconducting channel expressed at the cell surface. Finally, these Cys substitutions increased channel affinity for block by externalZn2+ ions, in particular the αS583C mutant showing a K
i for Zn2+of 29 μM. Mutations of residues αW582L or βG522D also increased amiloride K
i, the later mutation generating a Ca2+blocking site located 15% within the membrane electric field. These experiments provide strong evidence that αβγ ENaCs are pore-forming subunits involved in ion permeation through the channel. The pre-M2 segment of αβγ subunits may form a pore loop structure at the extracellular face of the channel, where amiloride binds within the channel lumen. We propose that amiloride interacts with Na+ions at an external Na+binding site preventing ion permeation through the channel pore. 相似文献
122.
Estelle Villemont Frédéric Dubois Rajbir S. Sangwan Gérard Vasseur Yvan Bourgeois Brigitte S. Sangwan-Norreel 《Planta》1997,201(2):160-172
Chimeric -glucuronidase (GUS) gene expression in an efficientAgrobacterium-mediated transformation system utilising mesophyll cells ofPetunia hybrida synchronized with cell cycle phase-specific inhibitors (mimosine and colchicine) was used to show the absolute requirement of S-phase for transfer and/or integration of the transferred DNA (T-DNA). Flow-cytometric analysis of nuclear DNA content and immunohistological detection of bromodeoxyuridine (BrdUrd) incorporation showed that, prior to phytohormone treatment, most (98%) mesophyll cells were at GO-Gl-phase (quiescent phase) and no cell division was occurring. After 48 h and 72 h of phytohormone treatment, there was a rapid increase in S-G2-M-phase populations (> 75%) and a concomitant decrease (down to 24%) in G0–-G1-phase cells. Assays of GUS showed that maximum transformation (> 95% of explants) also occurred after this period. Our data showed that mimosine and colchicine blocked the mesophyll cells at late Gl-phase and M-phase, respectively. No transformation (= GUS expression) was observed in phytohormone-treated cells inhibited in late G1 by mimosine. However, after removal of mimosine, 82% of the explants were transformed, indicating the non-toxic and reversible effect of the inhibitor. On the other hand, a relatively high transformation frequency (65% of explants) was observed after blocking the cell cycle at M-phase with colchicine. However, only transient, but no stable, gene expression (= kanamycin-resistant callus formation) was observed in colchicine-treated M-phase-arrested cells. Similarly, endoreduplication of nuclear DNA, which occurred during the 48 h of phytohormone treatment in some mesophyll cells and cells located along the minor veins in the leaf explants, resulted in transient GUS expression only. These observations indicate a direct correlation between endoreduplication and transient GUS gene expression. Obviously, for stable GUS gene expression, cell division and proliferation are required, indicating that both DNA duplication (S-phase) and cell division (M-phase) are strongly related to stable transformation. We propose that the present system should facilitate further dissection of the process of T-DNA integration in the host genome and therefore should aid in developing new strategies for transformation of recalcitrant plants.Abbreviations BAP
6-benzylaminopurine
- BM
basal medium
- BrdUrd
bromodeoxyuridine
- GUS
-glucuronidase
- KmR
kanamycin resistant
- T-DNA
transferred DNA 相似文献
123.
124.
Characterization of Shiga Toxin Gene (stx)-Positive and Intimin Gene (eae)-Positive Escherichia coli Isolates from Wastewater of Slaughterhouses in France 下载免费PDF全文
Estelle Loukiadis Monique Krourdan Lothar Beutin Eric Oswald Hubert Brugre 《Applied microbiology》2006,72(5):3245-3251
Wastewater samples from 12 slaughterhouses located in different regions in France were tested for the presence of stx-positive and eae-positive Escherichia coli isolates, and characteristics of the isolates obtained were determined. A total of 224 wastewater samples were collected in wastewater treatment plants at different stages of wastewater processing. Altogether, 5,001 E. coli isolates were obtained by colony counting and screened for the presence of stx and eae genes by multiplex PCR. stx-positive and eae-positive E. coli isolates were detected in 25% of the samples collected; they were found in 13% and 3% of the samples obtained from treated effluent and sludge, respectively, suggesting that they could be spread into the environment. Screening of the samples collected by immunomagnetic separation allowed us to isolate 31 additional E. coli serogroup O157 isolates. Four of these isolates harbored stx and eae genes. All stx-positive and eae-positive E. coli isolates were analyzed for eae and stx genetic variants, as well as for additional virulence factors and serotypes. Our results suggest that the majority of the stx- and eae-positive E. coli isolates from wastewater have low virulence for humans. However, the diversity of the enterohemorrhagic E. coli-associated virulence factors in the strains indicates that the environment may play an important role in the emergence of new pathogenic enterohemorrhagic E. coli strains. 相似文献
125.
Regulation of Flagellar Morphogenesis by Temperature: Involvement of the Bacterial Cell Surface in the Synthesis of Flagellin and the Flagellum 总被引:6,自引:3,他引:3 下载免费PDF全文
The induction of beta-glucosidases (EC 3.2.1.21) was studied in Neurospora crassa. Cellobiase was induced by cellobiose, but other inducers had little effect on this enzyme. Cellobiase activity was very low in all stages of the vegetative life cycle in the absence of di-beta-glucoside inducer. Aryl-beta-glucosidase was semiconstitutive at late stages of culture growth prior to conidiation. At early stages, aryl-beta-glucosidase was induced by cellobiose, laminaribiose, and gentiobiose, and weakly induced by galactose, amino sugars, and aryl-beta-glucosides. The induction properties of the beta-glucosidases are compared with those of the other disaccharidases of Neurospora. The induction of beta-glucosidases was inhibited by glucose, 2-deoxy-d-glucose, and sodium acetate. Sodium phosphate concentrations between 0.01 and 0.1 M stimulated induction of both enzymes, while concentrations above 0.1 M were inhibitory. The optimal condition for induction of both beta-glucosidases was pH 6.0. Cellobiase induction was relatively more inhibited than aryl-beta-glucosidase in the range of pH 6.0 to 8.0. 相似文献
126.
Georges St. Laurent Yuri Vyatkin Denis Antonets Maxim Ri Yao Qi Olga Saik Dmitry Shtokalo Michiel?J.L. de?Hoon Hideya Kawaji Masayoshi Itoh Timo Lassmann Erik Arner Alistair R.R. Forrest The FANTOM consortium Estelle Nicolas Timothy A. McCaffrey Piero Carninci Yoshihide Hayashizaki Claes Wahlestedt Philipp Kapranov 《Nucleic acids research》2016,44(7):3233-3252
127.
The in vitro digestibility of Ulva armoricana proteins by trypsin, chymotrypsin and human intestinal juice was determined
to evaluate their nutritional value. The amino acid composition of the protein fraction and its changes during a sampling
period from October to February were also studied. Some differences in the protein pattern shown by SDS PAGE were found in
different months, such as the presence of a 54 kDa protein in February. The protein fraction is composed mainly of aspartic
and glutamic acids (24–35% of protein fraction, according to season) and the essential amino acids constitute 27–36% of the
total fraction. The efficiencies of trypsin and chymotrypsin in Ulva protein digestion are comparable. Only four proteins
with apparent molecular weights of 86, 68, 40, and 29 KDa are digested by these proteolytic systems. The proteins from the
October sample were more sensitive to chymotrypsin than those from the February sample. For instance, two proteins with apparent
molecular weights of 100 and 67 kDa were weakly digested by chymotrypsin in the February extract, were fully digested in the
October sample. The February sample differed from two others in the presence of glycosylated proteins, most of which have
apparent molecular weights higher than 43 KDa. With the October sample, the activity of human intestinal juice was more effective
than two other proteolytic systems. This is especially evident with a 27 kDa protein, which was only partially digested by
the intestinal liquid and not digested by chymotrypsin or trypsin. However, human intestinal juice in the February apparently
did not attack the 27 kDa protein. These data suggest a change in protein structure making it less sensitive to human intestinal
juice. The glycosylation of protein extract, which was especially marked in February, could explain the differences in behaviour
of U. armoricana proteins in response to the digestive action of human enzymes.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
128.
Laura Moquet Rossana Bacchetta Estelle Laurent Anne-Laure Jacquemart 《Biodiversity and Conservation》2017,26(3):687-702
Modifications of landscape structure and composition can decrease the availability of floral resources, resulting in the decline of many pollinator species, including bumblebees. These declines may have significant ecological consequences, because bumblebees pollinate a large range of plant species. Our study was carried out in heathlands, open semi-natural habitats that have decreased considerably due to human activities. We analysed how floral resources affect bumblebee communities throughout the colony lifetime at three scales: plot scale, heathland patch scale, and landscape scale. Floral density at the plot scale and spruce plantations at the landscape scale influenced bumblebee communities. The abundance of bumblebees on ericaceous species was higher when the landscape included a substantial proportion of unsuitable foraging habitat (i.e., spruce plantations). Both life history traits and colony life cycle stage influenced bumblebee responses to the availability of floral resources. Bumblebees were more affected by floral resources during the colony development phase than during the nest-foundation or mating phases. Moreover, bumblebees of species that form large colonies needed larger quantities of favourable foraging habitat, compared with small-colony bees, and their proportion decreased in habitats dominated by spruce plantations. In conclusion, the conservation of plant–bumblebee interactions will require management at a larger spatial scale than the restricted protected habitats. Moreover, at the landscape scale, both quantity of favourable foraging patches and their ecological continuity are important to conserve both small- and large- colony species. 相似文献
129.
Cendrine Godet Estelle Cateau Blandine Rammaert Marine Grosset Gwenaël Le Moal Guillaume Béraud Jean Philippe Martellosio Xavier Iriart Jacques Cadranel France Roblot 《Mycopathologia》2017,182(7-8):709-713
Invasive fungal infection is a serious complication following allogeneic hematopoietic stem cell transplantation. Pulmonary infection due to Hormographiella aspergillata is an uncommon condition associated with a high mortality rate. The susceptibility of H. aspergillata to available antifungal agents is not well established. We report for the first time a case of H. aspergillata lung infection that responded poorly to conventional treatment with liposomal amphotericin B (LAmB; 3 mg kg?1 of body weight per day) with renal damage at higher posology (5 mg kg?1 of body weight per day), but improved rapidly after addition of nebulized LAmB to intravenous LAmB (3 mg kg?1 of body weight per day). Successful treatment of our patient using nebulized LAmB would be worth evaluating in cases refractory to standard treatment or when the reference treatment may not be extended due to interaction or side effects. 相似文献
130.
Laura Estelle Yêyinou Loko Azize Orobiyi Paterne Agre Alexandre Dansi Manuele Tamò Yves Roisin 《Journal of ethnobiology and ethnomedicine》2017,13(1):64