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101.
Maren Preuss Pilar Díaz-Tapia Heroen Verbruggen Giuseppe C. Zuccarello 《Journal of phycology》2023,59(5):950-962
Parasitic red algae are an interesting system for investigating the genetic changes that occur in parasites. These parasites have evolved independently multiple times within the red algae. The functional loss of plastid genomes can be investigated in these multiple independent examples, and fine-scale patterns may be discerned. The only plastid genomes from red algal parasites known so far are highly reduced and missing almost all photosynthetic genes. Our study assembled and annotated plastid genomes from the parasites Janczewskia tasmanica and its two Laurencia host species (Laurencia elata and one unidentified Laurencia sp. A25) from Australia and Janczewskia verruciformis, its host species (Laurencia catarinensis), and the closest known free-living relative (Laurencia obtusa) from the Canary Islands (Spain). For the first time we show parasitic red algal plastid genomes that are similar in size and gene content to free-living host species without any gene loss or genome reduction. The only exception was two pseudogenes (moeB and ycf46) found in the plastid genome of both isolates of J. tasmanica, indicating potential for future loss of these genes. Further comparative analyses with the three highly reduced plastid genomes showed possible gene loss patterns, in which photosynthetic gene categories were lost followed by other gene categories. Phylogenetic analyses did not confirm monophyly of Janczewskia, and the genus was subsumed into Laurencia. Further investigations will determine if any convergent small-scale patterns of gene loss exist in parasitic red algae and how these are applicable to other parasitic systems. 相似文献
102.
Judith Z. Drexler Isa Woo Christopher C. Fuller Glynnis Nakai 《Restoration Ecology》2019,27(5):1117-1127
Few comparisons exist between vertical accretion (VA) and carbon accumulation rates (CARs) in restored versus historic (i.e. reference) marshes. Here, we compare these processes in a formerly diked, sparsely vegetated, restored salt marsh (Six Gill Slough, SG), whose surface is subsided relative to the tidal frame, to an adjacent, relatively pristine, historic salt marsh (Animal Slough, AS). Six sediment cores were collected at both AS and SG approximately 6 years after restoration. Cores were analyzed for bulk density (BD), % loss of ignition, % organic carbon, and 210Pb. We found that sharp changes in BD in surface layers of SG cores were highly reliable markers for the onset of restoration. The mean VA since restoration at SG (0.79 [SD = 0.29] cm/year) was approximately twice that of AS (0.41 [SD = 0.16] cm/year). In comparison, the VA at AS over 50 years was 0.30 (SD = 0.09) cm/year. VA consisted almost entirely of inorganic sediment at SG whereas at AS it was approximately 55%. Mean CARs at SG were somewhat greater than at AS, but the difference was not significant due to high variability (SG: 81–210 g C m?2 year?1; AS: 115–168 g C m?2 year?1). The mean CAR at AS over the past 50 years was 118 (SD = 23) g C m?2 year?1. This study demonstrates that a sparsely vegetated, restored salt marsh can quickly begin to accumulate carbon and that historic and restored marshes can have similar CARs despite highly divergent formation processes. 相似文献
103.
After a thirty-fold lowering of the orthophosphate concentration of the eutrophic River Meuse, the granular polyphosphate reserve of planktonic algae did not decrease significantly. Although the algal populations were clearly limited by phosphorus, individual cells stored phosphorus but did not use it to increase their biomass. 相似文献
104.
The effect of passively administered immune serum against B. rodhaini has been studied quantitatively. The curve relating the proportion of parasites surviving, to the dose of serum, is sigmoid with a steep middle region. Parasites are killed at a rate proportional to the dose of serum in the early stages of infection, but after about 24 h a residual population of parasites multiplies at a rate only slightly less than that of normal parasites in normal hosts. The slight reduction is attributed to a residual effect of immune serum, and to the induction of an active immune response inadequate to prevent continuing multiplication of parasites.
The relationship between log10 (parasite dose) and ST50 for groups of mice is used to measure the dose of infective parasites. 相似文献
105.
Evaluation of pilot-scale modified A2O processes for the removal of nitrogen compounds from sewage 总被引:1,自引:0,他引:1
Eun-Tae Lim Gwi-Taek Jeong Sung-Hun Bhang Seok-Hwan Park Don-Hee Park 《Bioresource technology》2009,100(24):6149-6154
In this study, pilot-scale experiments for the removal of nitrogen from sewage obtained from a county Y sewer system were performed using modified A2O processes. Using this approach, the total amount of nitrogen discharged during denitrification of the influent was average 38.6 mg/L and a level of average 10.8 mg/L was maintained throughout the denitrification process, which resulted in an average removal efficiency that was greater than 72%. The nitrogen components in the effluent water consisted of 22% ammonia nitrogen, 6% nitrite nitrogen and 72% nitrate nitrogen, reaching a nitrification efficiency of 94%. In conclusion, since these advanced treatment methods, which involve modified A2O processes, were successfully employed to remove nitrogen from sewage discharge, they hold promise for wide spread use by treatment plants. 相似文献
106.
107.
Nitrous oxide emissions from surface flow and subsurface flow constructed wetland microcosms: Effect of feeding strategies 总被引:2,自引:0,他引:2
Wenlin JiaJian Zhang Peizhi LiHuijun Xie Juan Wu Jinhe Wang 《Ecological Engineering》2011,37(11):1815-1821
The effects of continuous and intermittent feeding strategies on nitrogen removal and N2O emission from surface flow and subsurface flow constructed wetlands were evaluated in this study. Microcosm wetlands planted with Phragmites australis were constructed and operated with different feeding strategies for the 4-month experiment. Results showed the intermittent feeding strategy could enhance the removal of ammonium effectively in the subsurface flow constructed wetlands, although it had no significant effect for the surface flow wetlands. And the intermittent feeding mode could promote the emission of N2O. The amount of N2O-N emission from the subsurface flow constructed wetlands with intermittent feeding mode was about 5 times higher than that with continuous feeding strategy and the emission rate ranged from 0.09 ± 0.03 to 7.33 ± 1.49 mg/m2/h. Compared with the surface flow constructed wetlands, the N2O emission in the subsurface flow constructed wetlands was affected significantly by the intermittent feeding mode. 相似文献
108.
We found evidence that a nematode (Skrjabinoclava morrisoni)
adaptivelymanipulates the behavior of its intermediate host (the amphipod
Corophiumvolutator) to increase its likelihood of transmission to
itsfinal host (the semipalmated sandpiper, Calidris pusilla). We
foundthat male and female amphipods parasitized by nematodes increasedtheir
surface activity in the field during daytime, but notduring nighttime hours.
Increased surface activity is knownto increase susceptibility of amphipods to
predation by sandpipersduring the day, but not at night, when sandpipers do
not feedvisually. Also, as predicted by the manipulation hypothesis,only
late-stage (infective) larvae of nematodes were associatedwith behavioral
changes of amphipods. We found no evidence thatparasites were associated with
other amphipod behaviors in thelaboratory, such as trail complexity, distance
traveled, orburrow-probing activity of crawling males as would be expectedif
parasitized hosts altered their own behavior. Survivorshipof amphipods was
also unaffected by parasitism, which may favorparasite transmission. Thus,
behavioral changes of parasitizedhosts were simple, and their expression was
context-dependentand related to likelihood of predation. We argue that
maturationtimes of nematodes in relation to migration schedules of sandpipers
providea narrow window of opportunity and may explain why nematodes
manipulateamphipod behavior. 相似文献
109.
The giant panda is a global symbol of wildlife conservation that is threatened by historic and current habitat loss. Despite
a great deal of research on the physiology, reproductive biology, and diet of pandas in the wild and in captivity, there is
little information on wild panda mortality. Here we integrate previously unavailable data on the mortality of wild pandas.
We report on three recent phases of panda mortality: deaths due to bamboo flowering in the 1970s and 1980s, surprisingly extensive
poaching in the 1980s and 1990s, and a parasitic infection over the past few years. Our analyses suggest that the current
most significant threat to wild panda survival is disease due to extraintestinal migration (visceral larval migrans) by an
ascarid nematode. We demonstrate that the probability of death of wild pandas being caused by this disease increased significantly
between 1971 and 2005 and discuss the possible factors leading to the emergence of this disease.
Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
110.
The goal of this research was to investigate the simultaneous occurrence of nitrification and denitrification by activated sludge exposed to volatile fatty acids (VFAs) during aerobic wastewater treatment using a single-stage reactor. A mixture of VFAs was spiked directly into a continuous-stirred tank reactor (CSTR) to assess subsequent impacts on nitrite removal, nitrate formation, CO(2) fixation, total bacterial density, and dominant nitrite oxidizing bacteria (NOB) concentration (i.e., Nitrospira). The activity of the periplasmic nitrate reductase (NAP) enzyme and the presence of nap gene were also measured. A rapid decrease in the nitrate formation rate (>70% reduction) was measured for activated sludge exposed to VFAs; however, the nitrite removal rate was not reduced. The total bacterial density and Nitrospira concentration remained essentially constant; therefore, the reduction in nitrate formation rate was likely not due to heterotrophic uptake of nitrogen or to a decrease in the dominant NOB population. Additionally, VFA exposure did not impact microbial CO(2) fixation efficiency. The activity of NAP enzyme increased in the presence of VFAs suggesting that nitrate produced as a consequence of nitrite oxidation was likely further reduced to gaseous denitrification products via catalysis by NAP. Little, if any, nitrogen was discharged in the aqueous effluent of the CSTR after exposure to VFAs demonstrating that activated sludge treatment yielded compounds other than those typically produced solely by nitrification. 相似文献