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61.
Summary Streptomycin-resistant Pseudomonas and Arthrobacter were isolated from semi-arid grassland soil and their relative responses in the rhizosphere of blue grama (Bouteloua gracilis) subjected to herbage removal were evaluated. Using plants grown in normal soil, the two bacteria showed differential responses to herbage removal, which were most marked in the rhizoplane, where the Pseudomonas showed a two-log unit increase over a 60 hour period, while Arthrobacter, in contrast, exhibited a one-log unit decrease in viable counts for at least 48 hours after defoliation, responses which are similar to those observed in root exudate medium experiments by earlier workers. These results suggest that the rhizoplane may be a critical environment for interaction of these two types of microorganisms, and that sequential responses of the root-associated soil microorganisms may occur after herbage removal from this important rangeland plant. These responses are most likely associated with increased exudate release following herbage removal, which has been best documented using blue grama grown under sterile conditions. 相似文献
62.
D. Sharp 《Plant Ecology》1976,31(2):103-119
Summary The vegetation of cultivated, fallow and ‘old’ fields of Scotland County, N.C. was both randomly and subjectively sampled
throughout the growing season of 1973. Relevés were placed in each of the above management units, and the data collected in
this relevé analysis were sorted into phytosociological charts, with the aid of the digital computer.
Weed associations delimited in the charts reflected the importance of edaphic factors, time (aspect), and man's agricultural
activities as causal factors in the determination of characteristic assemblages of weeds. Several character and differential
species were denoted, in a tentative classification of the weed associations. The cultivated and fallow stands in the spring
aspect were noted to be dominated by a group of spring annuals. Summer annuals were more prevalent in homologous situations
in the summer. It was determined that perennials, appearing mainly as seedlings in cultivated and fallow fields, attained
dominance in ‘old’ fields, one to five years in age. Within each of the major spheres of management, and in each season, associations
of weeds mainly reflected differences in edaphic factors. Many character species were noted to maintain affinities to an assortment
of soil types that ranged from moist loams to xeric, sterile sands.
A study of roadsides, hedgerows, field margins and other ecotonal areas inhabited by weeds was carried throughout the growing
season of 1973, also. Species presence was documented in each of these habitat types and reported in Sharp (1974).
The weed flora of Scotland County was found to be rich in species. A total of 506 species representing 248 genera and 80 families
were encountered throughout the study. Of the total number of species listed, approximately 25 percent were of foreign origin,
and 28 percent represented additions to the flora of Scotland County.
This paper is the short version of a masters thesis for the Department of Botany, University of North Carolina at Chapel Hill.
The author would like to extend his appreciation and gratitude to Professors H. Lieth, A. E. Radford and J. Hardin for their
generous advice and encouragement extended through the duration of the study. 相似文献
63.
64.
Zusammenfassung Durch eine anaerobe Mischflora aus Ackerboden wurde -Hexachlorcyclohexan (-HCH) in 4–5 Tagen zu 90% abgebaut. Dabei erfolgte eine schnelle Abspaltung des Chlors in Form von Chloridionen und danach eine Freisetzung des C- und H-Anteiles in Form flüchtiger Verbindungen, in denen kein Chlor und auch kein CO2 nachzuweisen war.Die Verwendung von 14C/3H- und 36Cl/3H-doppelmarkiertem -HCH zeigte, daß die Cl- und H-Abspaltung nicht im Verhältnis von 1:1 erfolgte, sondern mehr Cl als H abgespalten wurde. Die flüchtigen Verbindungen enthielten andererseits höhere 14C- als 3H-Anteile. Gaschromatographische Untersuchungen zeigten ebenfalls eine rasche Verminderung des -HCH und die Bildung verschiedener Metabolite. Es wurde jedoch kein -Pentachlorcyclohexen nachgewiesen. Bei steigenden O2-Gehalten in der Gasphase verminderte sich der -HCH-Abbau. Jedoch fanden auch noch bei 5% O2 Chlorabspaltung und die Freisetzung flüchtiger Metabolite statt.-HCH wurde ebenfalls, jedoch langsamer, durch die anaerobe Mischflora abgebaut. Auch hier wurde Chlorid abgespalten, und es traten ebenfalls flüchtige Verbindungen auf, die kein Chlor enthielten.
Degradation of 14C-, 3H- and 36Cl-labelled -hexachlorocyclohexane by anaerobic soil microorganisms
Up to 90% of the -Hexachlorocyclohexane (-HCH) applied to an anaerobic mixed bacterial flora enriched from an arable soil were degraded within 4–5 days. Degradation resulted in a rapid release of chloride and in formation of chlorine-free volatile metabolites. CO2 formation from the molecule was not detected.Investigations with 14C/3H- and 36Cl/3H double-labelled -HCH indicated that the release of Cl and H did not occur in the ratio of 1:1. More Cl than H was split off. The volatile compounds contained more 14C than 3H. Gas chromatographic studies also showed the rapid decrease of -HCH and the formation of several metabolites. -Pentachlorocyclohexene was not detected. Increasing O2-contents in the gas phase of cultures resulted in decreases of the compound's degradation. Release of chloride and of volatile metabolites were observed with O2 contents in the gas phase up to 5%.-HCH was also, but more slowly as with -HCH, degraded by the anaerobic mixed flora. Chloride was released and volatile, chlorine-free metabolites were found.相似文献
65.
Chiranjib Banerjee Rajib Bandopadhyay Pratyoosh Shukla 《Indian journal of microbiology》2012,52(4):710-712
A simple agar diffusion method is developed where pure colony of Chlamydomonas sp. CRP7 was isolated from Chlorella sp. CB4 mixtures by passing through agar migration with a light exposure of 6,000 lux for 7 h. The main concept behind it is that Chlamydomonas has flagella and the rhodopsin pigment is attracted towards light. Thus the above two microalgae species can be separated from the mixtures as eye spot serves as a navigator and flagella serves as a propeller for Chlamydomonas spp. Further the genomic DNA was isolated and purified from the above mentioned two species after the separation from the mixtures. PCR amplification was carried out for ITS1, 5.8S and ITS2 regions. The amplified products were sequenced and the sequence analysis confirmed that they belong to Chlamydomonas sp. and Chlorella sp. This is an important augmentation for isolation and separation of microalgae. 相似文献
66.
We advocate the concept of an arbuscular mycorrhiza (AM) as a temporally and spatially complex symbiosis representing a suite
of hosts and fungi, as against the more traditional "dual organism" view. We use the hierarchical framework presented in Fig. 1
as a basis for organizing many unanswered questions, and several questions that have not been asked, concerning the role of
AM in responses to elevated atmospheric CO2. We include the following levels: plant host, plant population, plant community, functional group and ecosystem. Measurements
of the contributions of AM fungi at the various levels require the use of different response variables. For example, hyphal
nutrient translocation rates or percent AM root infection may be important measures at the individual plant level, but hyphal
biomass or glomalin production and turnover are more relevant at the ecosystem level. There is a discrepancy between our knowledge
of the multifaceted role of AM fungi in plant and ecosystem ecology and most of the current research aimed at elucidating
the importance of this symbiosis in global-change scenarios. Our framework for more integrated and multifactorial research
on mycorrhizal involvement in regulating CO2 responses may also serve to enhance communication between researchers working at different scales on large global-change
ecosystem projects.
Accepted: 12 February 1999 相似文献
67.
Fungal laccases - occurrence and properties 总被引:8,自引:0,他引:8
Baldrian P 《FEMS microbiology reviews》2006,30(2):215-242
Laccases of fungi attract considerable attention due to their possible involvement in the transformation of a wide variety of phenolic compounds including the polymeric lignin and humic substances. So far, more than a 100 enzymes have been purified from fungal cultures and characterized in terms of their biochemical and catalytic properties. Most ligninolytic fungal species produce constitutively at least one laccase isoenzyme and laccases are also dominant among ligninolytic enzymes in the soil environment. The fact that they only require molecular oxygen for catalysis makes them suitable for biotechnological applications for the transformation or immobilization of xenobiotic compounds. 相似文献
68.
So Eun Park Jong Cheol Kim Se Jin Lee Mi Rong Lee Sihyeon Kim Dongwei Li Sehyeon Baek Ji Hee Han Jeong Jun Kim Kyung Bon Koo Tae Young Shin Jae Su Kim 《Journal of Asia》2018,21(4):1102-1109
Entomopathogenic fungi have great potential to control agricultural and horticultural insect pests, however optimizing conidial production systems to demonstrate high productivity and stability still needs additional efforts for successful field application and industrialization. Although many virulent entomopathogenic fungal isolates have been viewed as potential candidates in a laboratory environment, very few of the isolates are being used in practice for application in agricultural fields as commercial products. I. javanicus is an entomopathogenic fungus that is parasitic to various diverse coleopteran and lepidopteran insects and thought good candidate as biopesticdes. In this work, the basic characteristics of two entomopathogenic fungi, I. javanica FG340 and Pf04, were investigated in morphological examinations, genetic identification, and virulence against Thrips palmi, and then the feasibility of various grains substrates for conidial production was assessed, particularly focusing on conidial productivity and thermotolerance. Isaria javanica FG340 and Pf04 conidia were solid-cultured on 12 grains for 14?days in a Petri dish. Of the tested Italian millet, perilla seed, millet and barley-based cultures showed high conidial production. The four-grain media yielded >1?×?109 conidia/g of I. javanica FG340 and Pf04. Pf04 strain had enhanced thermotolerance up to 45?°C when cultured on Italian millet. In application, it was easy to make a conidial suspension using the cultured grains, and several surfactants were tested to release the conidia. This work suggests several possible inexpensive grain substrates by which to promote conidial production combined with enhanced stability against exposure to high temperature. 相似文献
69.
70.
M. Fomina V. S. Podgorsky S. V. Olishevska V. M. Kadoshnikov I. R. Pisanska S. Hillier 《Geomicrobiology journal》2013,30(7-8):643-653
Fungal biogeochemical activity over a long-term scale may have negative environmental consequences for the management of barrier materials used in nuclear waste disposal. Fungal deterioration of barrier concrete was studied in microcosms simulating a heterogeneous environment with an external source of nutrients for the fungi. Fungi successfully colonized barrier concrete, generally avoiding granite aggregates, and biochemically (by excretion of protons and ligands) and biomechanically deteriorated the concrete. Fungi dissolved the cement matrix leaching structural elements and accumulating them within the fungal biofilm and associated microenvironment. Oxalate-excreting Aspergillus niger formed abundant calcium oxalate crystals on the concrete and encrusting fungal hyphae. 相似文献