全文获取类型
收费全文 | 926篇 |
免费 | 71篇 |
国内免费 | 1篇 |
专业分类
998篇 |
出版年
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 17篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 24篇 |
2015年 | 46篇 |
2014年 | 45篇 |
2013年 | 51篇 |
2012年 | 74篇 |
2011年 | 95篇 |
2010年 | 31篇 |
2009年 | 34篇 |
2008年 | 40篇 |
2007年 | 44篇 |
2006年 | 50篇 |
2005年 | 49篇 |
2004年 | 30篇 |
2003年 | 34篇 |
2002年 | 28篇 |
2001年 | 20篇 |
2000年 | 22篇 |
1999年 | 21篇 |
1998年 | 4篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 10篇 |
1994年 | 4篇 |
1993年 | 6篇 |
1992年 | 14篇 |
1991年 | 17篇 |
1990年 | 23篇 |
1989年 | 6篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 7篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 3篇 |
1935年 | 2篇 |
排序方式: 共有998条查询结果,搜索用时 15 毫秒
71.
Boon Chuan Low Catherine Qiurong Pan G.V. Shivashankar Alexander Bershadsky Marius Sudol Michael Sheetz 《FEBS letters》2014
Organ size is controlled by the concerted action of biochemical and physical processes. Although mechanical forces are known to regulate cell and tissue behavior, as well as organogenesis, the precise molecular events that integrate mechanical and biochemical signals to control these processes are not fully known. The recently delineated Hippo-tumor suppressor network and its two nuclear effectors, YAP and TAZ, shed light on these mechanisms. YAP and TAZ are proto-oncogene proteins that respond to complex physical milieu represented by the rigidity of the extracellular matrix, cell geometry, cell density, cell polarity and the status of the actin cytoskeleton. Here, we review the current knowledge of how YAP and TAZ function as mechanosensors and mechanotransducers. We also suggest that by deciphering the mechanical and biochemical signals controlling YAP/TAZ function, we will gain insights into new strategies for cancer treatment and organ regeneration. 相似文献
72.
F Van den Broeck L Meurs J A M Raeymaekers N Boon T N Dieye F A M Volckaert K Polman T Huyse 《Heredity》2014,113(1):32-41
The size, structure and distribution of host populations are key determinants of the genetic composition of parasite populations. Despite the evolutionary and epidemiological merits, there has been little consideration of how host heterogeneities affect the evolutionary trajectories of parasite populations. We assessed the genetic composition of natural populations of the parasite Schistosoma mansoni in northern Senegal. A total of 1346 parasites were collected from 14 snail and 57 human hosts within three villages and individually genotyped using nine microsatellite markers. Human host demographic parameters (age, gender and village of residence) and co-infection with Schistosoma haematobium were documented, and S. mansoni infection intensities were quantified. F-statistics and clustering analyses revealed a random distribution (panmixia) of parasite genetic variation among villages and hosts, confirming the concept of human hosts as ‘genetic mixing bowls'' for schistosomes. Host gender and village of residence did not show any association with parasite genetics. Host age, however, was significantly correlated with parasite inbreeding and heterozygosity, with children being more infected by related parasites than adults. The patterns may be explained by (1) genotype-dependent ‘concomitant immunity'' that leads to selective recruitment of genetically unrelated worms with host age, and/or (2) the ‘genetic mixing bowl'' hypothesis, where older hosts have been exposed to a wider variety of parasite strains than children. The present study suggests that host-specific factors may shape the genetic composition of schistosome populations, revealing important insights into host–parasite interactions within a natural system. 相似文献
73.
Siele Ceuppens Nico Boon Marc Heyndrickx Mieke Uyttendaele 《Journal of microbiological methods》2010,83(2):202-210
There is an interest to understand the fate and behaviour of the food-borne pathogen Bacillus cereus in the gut, a challenging environment with a high bacterial background. We evaluated the current detection methods to select an appropriate strategy for B. cereus monitoring during gastrointestinal experiments. Application of quantitative real-time PCR (qPCR) in a gastrointestinal matrix required careful selection of the qPCR reaction and elaborate optimization of the DNA extraction protocol. Primer competition and depletion problems associated with qPCR reactions targeting general 16S rRNA gene can be avoided by the selection of a target sequence that is unique for and widespread among the target bacteria, such as the toxin gene nheB in the case of pathogenic B. cereus. Enumeration of B. cereus during the ileum phase was impossible by plating due to overgrowth by intestinal bacteria, while a carefully optimized qPCR enabled specific detection and quantification of B. cereus. On the other hand, plating allowed the distinction of viable, injured and dead bacteria and the germination of spores, which was not possible with qPCR. In conclusion, both plating and qPCR were necessary to yield the maximal information regarding the viability and physiology of the B. cereus population in various gastrointestinal compartments. 相似文献
74.
75.
Aggregate Size and Architecture Determine Microbial Activity Balance for One-Stage Partial Nitritation and Anammox 总被引:1,自引:0,他引:1
Siegfried E. Vlaeminck Akihiko Terada Barth F. Smets Haydée De Clippeleir Thomas Schaubroeck Selin Bolca Lien Demeestere Jan Mast Nico Boon Marta Carballa Willy Verstraete 《Applied and environmental microbiology》2010,76(3):900-909
Aerobic ammonium-oxidizing bacteria (AerAOB) and anoxic ammonium-oxidizing bacteria (AnAOB) cooperate in partial nitritation/anammox systems to remove ammonium from wastewater. In this process, large granular microbial aggregates enhance the performance, but little is known about granulation so far. In this study, three suspended-growth oxygen-limited autotrophic nitrification-denitrification (OLAND) reactors with different inoculation and operation (mixing and aeration) conditions, designated reactors A, B, and C, were used. The test objectives were (i) to quantify the AerAOB and AnAOB abundance and the activity balance for the different aggregate sizes and (ii) to relate aggregate morphology, size distribution, and architecture putatively to the inoculation and operation of the three reactors. A nitrite accumulation rate ratio (NARR) was defined as the net aerobic nitrite production rate divided by the anoxic nitrite consumption rate. The smallest reactor A, B, and C aggregates were nitrite sources (NARR, >1.7). Large reactor A and C aggregates were granules capable of autonomous nitrogen removal (NARR, 0.6 to 1.1) with internal AnAOB zones surrounded by an AerAOB rim. Around 50% of the autotrophic space in these granules consisted of AerAOB- and AnAOB-specific extracellular polymeric substances. Large reactor B aggregates were thin film-like nitrite sinks (NARR, <0.5) in which AnAOB were not shielded by an AerAOB layer. Voids and channels occupied 13 to 17% of the anoxic zone of AnAOB-rich aggregates (reactors B and C). The hypothesized granulation pathways include granule replication by division and budding and are driven by growth and/or decay based on species-specific physiology and by hydrodynamic shear and mixing.In the last few years, autotrophic nitrogen removal via partial nitritation and anoxic ammonium oxidation (anammox) has evolved from lab- to full-scale treatment of nitrogenous wastewaters with a low biodegradable organic compound content, and this evolution has been driven mainly by a significant decrease in the operational costs compared to the costs of conventional nitrification and heterotrophic denitrification (11, 23). Oxygen-limited autotrophic nitrification and denitrification (OLAND) is one of the autotrophic processes used and is a one-stage procedure; i.e., partial nitritation and anammox occur in the same reactor (30). The “functional” autotrophic microorganisms in OLAND include aerobic ammonium-oxidizing bacteria (AerAOB) and anoxic ammonium-oxidizing bacteria (AnAOB). With oxygen, AerAOB oxidize ammonium to nitrite (nitritation), and with the nitrite AnAOB oxidize the residual ammonium to form dinitrogen gas and some nitrate (anammox). Additional aerobic nitrite oxidation to nitrate (nitratation) by nitrite-oxidizing bacteria (NOB) lowers the nitrogen removal efficiency, but it can, for instance, be prevented at low dissolved oxygen (DO) levels because the oxygen affinity of AerAOB is higher than that of NOB (16). Reactor configurations for the OLAND process can be based on suspended biomass growing in aggregates, like that in a sequencing batch reactor (SBR) (37) or a gas lift or upflow reactor (32). For suspended-growth systems there are two important challenges: biomass retention and equilibrated microbial activities.High biomass retention efficiency is a prerequisite in anammox technologies because of the slow growth of AnAOB (33). In suspended biomass systems, settling properties determine the retention of biomass and are related to the microbial aggregate morphology (floc or granule) and size. Granules can be defined as compact and dense aggregates with an approximately spherical external appearance that do not coagulate under decreased hydrodynamic shear conditions and settle significantly faster than flocs (18). Toh and coworkers calculated a lower sludge volume index for aerobic granules than for aerobic flocs and also showed that there was an increase in the settling velocity with increasing granule size (35). Hence, in terms of physical properties, large granules are preferable for suspended-growth applications.OLAND aggregate size not only influences settling properties but also affects the proportion of microbial nitrite production and consumption; lower AerAOB activity and higher AnAOB activity were observed with larger aggregates (25, 37). Theoretically, a microbial aggregate with equal nitrite production and nitrite consumption can remove ammonium autonomously, because of its independence from other aggregates for acquisition and conversion of nitrite. Hence, with an increasing aggregate size and thus with a decreasing ratio of nitrite production to nitrite consumption, three functional categories of aggregates can be distinguished: nitrite sources, autonomous nitrogen removers, and nitrite sinks. Because minimal nitrite accumulation is one of the prerequisites for high nitrogen removal efficiency in OLAND reactors, the presence of excess small aggregates is undesirable (9, 37).Although large granular aggregates are desirable for biomass retention and activity balance, so far no formation mechanisms have been proposed for OLAND granules, in contrast to the well-studied anaerobic (13) and aerobic (1) granules. In order to determine general and environment-specific determinants for aggregate size and architecture, three suspended-growth OLAND reactors with different inoculation and operation (mixing and aeration) parameters were selected, and these reactors were designated reactors A, B, and C (Table (Table1).1). The first objective of this study was to gain more insight into the relationship between OLAND aggregate size, AerAOB and AnAOB abundance, and the activity balance. The second objective was to propose pathways for aggregation and granulation by relating (dis)similarities in aggregate size distribution, morphology, and architecture to differences in reactor inoculation and operation.
Open in a separate windowaAggregates settling at a rate higher than the minimum settling velocity (MSV) were not washed out of the sequencing batch reactors (SBR). The MSV was calculated by dividing the vertical distance of the water volume decanted per cycle by the settling time.bSupernatant from a municipal sludge digestor.cEffluent from a potato-processing factory pretreated with anaerobic digestion and struvite precipitation.dObtained at the end of a reactor start-up study (37).eObtained at the end of a reactor start-up study (9). 相似文献
TABLE 1.
Overview of the three OLAND reactor systems from which suspended biomass samples were obtainedParameter | Reactor Aa | Reactor Ba | Reactor C |
---|---|---|---|
Reactor type | SBR | SBR | Upflow reactor |
Vol (m3) | 0.002 | 4.1 | 600 |
Reactor ht/diam ratio | 0.9 | 4 | 0.5-0.8 |
Inoculum | OLAND biofilm | Activated sludge | Anammox granules |
Wastewater | Synthetic | Domesticb | Industrialc |
Influent ammonium concn (mg N liter−1) | 230-330 | 800 | 250-350 |
Nitrogen removal rate (g N liter−1 day −1) | 0.45,d 1.1e | 0.65 | 1.3 |
Effluent nitrite concn (mg N liter−1) | 30-40d | 5-10 | 5-10 |
Influent COD/effluent COD (mg liter−1) | 0/0 | 240/220 | 200/150 |
pH | 7.4-7.8 | 7.4-7.6 | 8.0 |
Temp (°C) | 35 | 25 | 30-35 |
DO level (mg O2 liter−1) | 0.4-1.1 | 0.5-1.0 | 2.0-3.0 |
Mixing mechanism | Magnetic stirrer | Bladed impeller | Aeration |
Biomass retention mechanism | MSV, >0.73 m h−1 | MSV, >1.4 m h−1 | Three-phase separator |
Sampling time (months after start-up) | 2d | 8 | 30 |
76.
Boon AC de Mutsert G van Baarle D Smith DJ Lapedes AS Fouchier RA Sintnicolaas K Osterhaus AD Rimmelzwaan GF 《Journal of immunology (Baltimore, Md. : 1950)》2004,172(4):2453-2460
In the present study, the recognition of epitope variants of influenza A viruses by human CTL was investigated. To this end, human CD8(+) CTL clones, specific for natural variants of the HLA-B*3501-restricted epitope in the nucleoprotein (NP(418-426)), were generated. As determined in (51)Cr release assays and by flow cytometry with HLA-B*3501-peptide tetrameric complexes, CTL clones were found to be specific for epitopes within one subtype or cross-reactive with heterosubtypic variants of the epitope. Using eight natural variants of the epitope, positions in the 9-mer important for T cell recognition and involved in escape from CTL immunity were identified and visualized using multidimensional scaling. It was shown that positions 4 and 5 in the 9-mer epitope were important determinants of T cell specificity. The in vivo existence of CD8(+) cells cross-reactive with homo- and heterosubtypic variants of the epitope was further confirmed using polyclonal T cell populations obtained after stimulation of PBMC with different influenza A viruses. Based on the observed recognition patterns of the clonal and polyclonal T cell populations and serology, it is hypothesized that consecutive infections with influenza viruses containing different variants of the epitope select for cross-reactive T cells in vivo. 相似文献
77.
Amelia K. Kivaisi Huub J. M. Op den Camp Henk J. Lubberding Jaap J. Boon Godfried D. Vogels 《Applied microbiology and biotechnology》1990,33(1):93-98
Summary The supernatants of effluents from an artificial rumen reactor degrading barley straw have been shown to contain lignin-derived compounds by UV spectral characteristics and pyrolysis mass spectrometry (PYMS). Most of these compounds were shown to be released by the action of rumen microorganisms. The compounds were quantified by measuring absorbance at 280 nm using bamboo-milled wood lignin as a standard. The concentration of the compounds rose from 0.5 mg·ml–1 at solid and liquid retention times (SRT and HRT) of 60 and 12 h, respectively, and a loading rate (LR) of 25 g total solids (TS)·l–1 per day to 3.5 mg·ml–1 at a SRT of 144 h, an HRT of 20 days and an LR of 15 g TS·1–1 per day. The highest concentration was below the level known to be toxic to rumen microorganisms in vitro. No indications were found for anaerobic lignin degradation in the rumen reactor.
Offprint requests to: H. J. M. Op den Camp 相似文献
78.
Boon Keng Lim 《Hydrobiologia》1997,358(1-3):297-299
Metamorphosis of fiddler crab Ilyoplax pusilla larvaefrom megalopal to first crab stage wasstudied in laboratory experiments under variousconditions of salinity and substratum. The hatchedzoea metamorphose through five stages before reachingmegalopal stage. The megalops were placed in a 20 mlPetri dishes (2–3 megalops/dish), with salinities of10, 20 or 30 . Each salinity level was tested eitherwith or without sandy mud substratum. Thirty to 35megalops were used in each of the six treatments. Theexperiment was carried out at a water temperature of28 ±0.5°C and with daily feeding of the diatomChaetoceros gracilis. Treatment of 20 salinity andsandy mud substratum revealed the highest metamorphicrate (87%), while in contrast no metamorphosis wasobserved at 30 salinity withoutsandy mud substratum. Duration of the metamorphosiswas about 16 days. Numerous malformed juvenile crabswere observed in treatments conductedwithout sandy mud substratum. 相似文献
79.
80.
Joke Duyck Katleen Vandamme Stefanie Krausch-Hofmann Lies Boon Katrien De Keersmaecker Eline Jalon Wim Teughels 《PloS one》2016,11(1)