全文获取类型
收费全文 | 1108篇 |
免费 | 78篇 |
专业分类
1186篇 |
出版年
2023年 | 20篇 |
2022年 | 25篇 |
2021年 | 33篇 |
2020年 | 35篇 |
2019年 | 36篇 |
2018年 | 40篇 |
2017年 | 47篇 |
2016年 | 56篇 |
2015年 | 55篇 |
2014年 | 64篇 |
2013年 | 89篇 |
2012年 | 92篇 |
2011年 | 83篇 |
2010年 | 51篇 |
2009年 | 34篇 |
2008年 | 61篇 |
2007年 | 36篇 |
2006年 | 53篇 |
2005年 | 33篇 |
2004年 | 33篇 |
2003年 | 32篇 |
2002年 | 27篇 |
2001年 | 23篇 |
2000年 | 25篇 |
1999年 | 17篇 |
1998年 | 3篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1960年 | 1篇 |
排序方式: 共有1186条查询结果,搜索用时 0 毫秒
161.
162.
Role of Nγ-Acetyldiaminobutyrate as an Enzyme Stabilizer and an Intermediate in the Biosynthesis of Hydroxyectoine
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
David Cnovas Nuno Borges Carmen Vargas Antonio Ventosa Joaquín J. Nieto Helena Santos 《Applied microbiology》1999,65(9):3774-3779
Strain CHR63 is a salt-sensitive mutant of the moderately halophilic wild-type strain Halomonas elongata DSM 3043 that is affected in the ectoine synthase gene (ectC). This strain accumulates large amounts of Nγ-acetyldiaminobutyrate (NADA), the precursor of ectoine (D. Cánovas, C. Vargas, F. Iglesias-Guerra, L. N. Csonka, D. Rhodes, A. Ventosa, and J. J. Nieto, J. Biol. Chem. 272:25794–25801, 1997). Hydroxyectoine, ectoine, and glucosylglycerate were also identified by nuclear magnetic resonance (NMR) as cytoplasmic organic solutes in this mutant. Accumulation of NADA, hydroxyectoine, and ectoine was osmoregulated, whereas the levels of glucosylglycerate decreased at higher salinities. The effect of the growth stage on the accumulation of solutes was also investigated. NADA was purified from strain CHR63 and was shown to protect the thermolabile enzyme rabbit muscle lactate dehydrogenase against thermal inactivation. The stabilizing effect of NADA was greater than the stabilizing effect of ectoine or potassium diaminobutyrate. A 1H NMR analysis of the solutes accumulated by the wild-type strain and mutants CHR62 (ectA::Tn1732) and CHR63 (ectC::Tn1732) indicated that H. elongata can synthesize hydroxyectoine by two different pathways—directly from ectoine or via an alternative pathway that converts NADA into hydroxyectoine without the involvement of ectoine. 相似文献
163.
164.
165.
Physiological responses to extreme hydrological events in the Pantanal wetland: heterogeneity of a plant community containing super‐dominant species
下载免费PDF全文
![点击此处可从《植被学杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
166.
167.
Zélia Silva Nuno Borges Lígia O. Martins Robin Wait Milton S. da Costa H. Santos 《Extremophiles : life under extreme conditions》1999,3(2):163-172
In this study we propose revised structures for the two major compatible solutes of Rhodothermus marinus. We have also examined the accumulation of compatible solutes by the type strains of the slightly halophilic and thermophilic
species Rhodothermus marinus and Rhodothermus obamensis at several growth temperatures and salinities. The major solutes of R. marinus were identified as α-mannosylglycerate (α-MG) and α-mannosylglyceramide (α-MGA), whereas R. obamensis accumulated only α-mannosylglycerate. The total osmolyte content was higher during the early exponential phase and decreased
abruptly as growth continued into the stationary phase. At low growth temperatures, R. marinus responded to water stress by accumulation of α-mannosylglycerate and its amide, in addition to low levels of trehalose, glutamate,
and glucose. At the highest growth temperature, α-mannosylglycerate was the major compatible solute and α-mannosylglyceramide
was not detected. When both compounds were present, an increase in the salinity of the growth medium favored the accumulation
of α-mannosylglyceramide over α-mannosylglycerate. The absence of α-mannosylglyceramide in R. obamensis at all growth temperatures and salinities constituted the most pronounced difference in the profiles of compatible solute
accumulation by the two strains. Trehalose was also a prominent solute in this organism. Both organisms accumulated higher
levels of α-mannosylglycerate as the temperature was raised. The importance of the two compounds in the mechanisms of thermoadaptation
and osmoadaptation is discussed.
Received: February 10, 1998 / Accepted: January 11, 1999 相似文献
168.
José Roberto Machado Cunha da Silva Laercio Ribeiro Porto-Neto João Carlos Shimada Borges Bernard Ernesto Jensch-Junior 《Polar Biology》2005,28(4):326-328
The germicide capability of the macrophage (MØ) of the Antarctic fish Notothenia coriiceps is demonstrated using fluorescence microscopy for the first time. The MØs were able to kill microorganisms by intracellular mechanism and this killing can be stimulated by oyster-derived glycogen. Although the phagocytosis index is lower than in temperate water fish species, this work demonstrates that non-specific defence mechanism plays an important role in the polar environment. There are some studies on inflammation in N. coriiceps [Silva et al. (1998) Polar Biol 20:206–212], parasite–host relation [Silva et al. (1999) Polar Biol 22:417–424] and phagocytosis [Silva et al. (2002) J Fish Biol 60:466–478]. These previous studies have shown that the MØ were able to identify biotic and abiotic factors. However, it can be of interest to study the activity of MØ in microorganism killing, and this work adds new insights of this fundamental process under Antarctic temperatures. 相似文献
169.
António Onofre Soares Isabel Borges Paulo A. V. Borges Geneviève Labrie Éric Lucas 《BioControl》2008,53(1):127-145
In recent years Harmonia axyridis (Pallas, 1773) (Coleoptera: Coccinellidae) has become a very popular insect among biological control practitioners and scientists, not only for its potential to be an efficient biological control agent but also because it is considered invasive. Individuals of this species were deliberately introduced into several countries for biological control of different arthropods pests. However the predator itself became an invasive species, affecting the dynamics and composition of several guilds through direct or indirect interactions with established species, including intraguild predation. In this paper we discuss the reasons why the species has a high invasiveness and what are the limits to invasion by this species. It is not clear if the invasiveness of the beetle is linked to its biological, ecological and behavioural abilities, or to other factors such as invasibility and interactions between the invaders, the noninvaders, and the habitat, which may in part explain the reasons of its success and help us to answer the question “what will stop the invader?” We also discuss the reason for the absence of the predator in the Azores islands. Despite the intentional introduction of H. axyridis in the Azores and the high number of individuals released, there are no records of this species in the wild, despite recent extensive sampling effort. In this paper we discuss the reasons for the apparent failure or the delay in establishment of the predator. One factor which may hamper the establishment of H. axyridis in some of the Azores islands is the absence of winter environmental conditions, mainly the temperature which is seldom lower than 12°C, essential for the induction of diapause. The lack of success in the establishment could be also related to functional diversity saturation, that is species saturation and competitive exclusion of H. axyridis by other previously established species may be operating. 相似文献
170.
Cruz-Monteagudo M Munteanu CR Borges F Cordeiro MN Uriarte E González-Díaz H 《Bioorganic & medicinal chemistry》2008,16(22):9684-9693
Numerical parameters of the molecular networks, also referred as Topological Indices or Connectivity Indices (CIs), have been used in Bioorganic and Medicinal Chemistry to find Quantitative Structure-Activity, Property or Toxicity Relationship (QSAR, QSPR and QSTR) models. QSPR models generally use CIs as inputs to predict the biological activity of compounds. However, the literature does not evidence a great effort to find QSAR-like models for other biologically and chemically relevant systems. For instance, blood proteome constitutes a protein-rich information reservoir, since the serum proteome Mass Spectra (MS) represents a potential information source for the early detection of Biomarkers for diseases and/or drug-induced toxicities. The concept of mass spectrum network (MS network) for a single protein is already well-known. However, there are no reported results on the use of CIs for a MS network of a whole proteome to explore MS patterns. In this work, we introduced for the first time a novel network representation and the CIs for the MS of blood proteome samples. The new network bases on Randic's Spiral network have been previously introduced for protein sequences. The new MS CIs, called here Spiral Markov Connectivity (SMC(k)) of the MS Spiral graph can be calculated with the software MARCH-INSIDE, combining network and Markov model theory. The SMC(k) values could be used to seek QSAR-like models, called in this work Quantitative Proteome-Property Relationships (QPPRs). We calculate the SMC(k) values for 62 blood samples and fit a QPPR model by discriminating proteome MS, typical of individuals susceptible to suffer drug-induced cardiotoxicity from control samples. The accuracy, sensitivity, and specificity values of the QPPR model were between 73.08% and 87.5% in training and validation series. This work points to QPPR models as a powerful tool for MS detection of biomarkers in proteomics. 相似文献