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991.
Ethnobotanical Knowledge and Crop Diversity in Swidden Fields: A Study in a Native Amazonian Society
Victoria Reyes-García Vincent Vadez Neus Martí Tomás Huanca William R. Leonard Susan Tanner 《Human ecology: an interdisciplinary journal》2008,36(4):569-580
Crop diversity protects food consumption in poor households within developing nations. Here we estimate the association between
crop diversity on swidden fields and ethnobotanical knowledge. We conducted research among 215 male household heads from a
native Amazonian society. Using multivariate regressions, we found higher crop diversity among households that depend on agricultural
production for household consumption. We also found a statistically significant and positive, but low, association between
the ethnobotanical knowledge of the male household head and crop diversity. Doubling the stock of ethnobotanical knowledge
of the male household head is associated with a 9% increase in the number of crops sown by a household. The association remained
after we controlled for the household level of market exposure, but vanished after we controlled for the social capital of
the male household head. Future research should compare the association between ethnobotanical knowledge and crop diversity
across different agricultural systems (i.e., home gardens, fallow fields). 相似文献
992.
Andrés Camou-Guerrero Victoria Reyes-García Miguel Martínez-Ramos Alejandro Casas 《Human ecology: an interdisciplinary journal》2008,36(2):259-272
We used a quantitative ethnobotanical approach to analyze factors influencing the use value of plant species among men and
women of the Rarámuri people in Cuiteco, Chihuahua, Mexico. We constructed a use value index (UV) combining the use frequency
(U) and the quality perception (Q) of useful plant species by local people. We identified all plant species used by the Rarámuri and classified them into 14
general use categories. We interviewed 34 households in the village to compare men and women’s knowledge on the five main
general use categories (and on their respective subcategories and specific uses), to document how they practice gathering
activities and to calculate scores of plants UV. A total of 226 useful plant species were identified, but only 12% of them
had high UV scores for the 42 specific uses defined. When the overall knowledge of plant species was examined, no significant differences
were detected between men and women, but significant differences were identified in general use categories such as medicinal
plants, plants for construction and domestic goods, but not in plants used as food and firewood. We identified a division
of labor in gathering activities associated with gender, with women mainly gathering medicinal and edible plants and being
involved in preparing medicines and food, whereas men were primarily gathering and using plants for manufacturing domestic
goods, firewood, and building materials. Plant species UV associated to gender were significantly different between men and
women at the level of specific uses in the general category of domestic goods and building. Frequency of use is highly associated
with plant species quality perception. 相似文献
993.
The Tsaatan (or Dhuka) peoples of northern-western Mongolia are one of the few remaining reindeer-herding cultural groups in the world. Recently a disease condition that involves sudden death of reindeer and cases involving fever, lethargy, and pale mucous membranes has been reported. Examination of blood smears collected in the 2005 field season resulted in the identification of intra-erythrocytic inclusions resembling Anaplasma spp. in smears from clinically sick animals. Using universal polymerase chain reaction (PCR) primers for the amplification of the 60 kDa chaperonin gene (cpn60, also known as hsp60 or groEL), we detected sequences corresponding to Anaplasma ovis in reindeer blood samples. Species-specific PCR primers for A. ovis were designed and validated and used to screen blood samples from Mongolian reindeer. Screening of 66 blood samples collected in the 2006 field season resulted in the detection of A. ovis in 80% of the samples. Our results indicate a high prevalence of A. ovis in the Tsaatan reindeer herds and an association with clinical disease that is likely to be anaplasmosis. To our knowledge this is the first report of natural A. ovis infection in reindeer. 相似文献
994.
Spatial Heterogeneity of Bacterial Populations in Monomictic Lake Estanya (Huesca,Spain) 总被引:2,自引:0,他引:2
Bacterial population changes were investigated in the monomictic Lake Estanya by combining microscopic analysis and two molecular
methods involving the amplification of 16S rDNA genes using primers for the domain Bacteria and subsequent restriction fragment length polymorphism (PCR–RFLP) and denaturing gradient gel electrophoresis (PCR–DGGE).
Both approaches revealed the vertical distribution of predominant microbial morphotypes and phylotypes in both holomictic
and stratified periods, respectively, and showed that variations in structure and composition of bacterial populations are
occurring in this lake as a function of depth and time. Through principal component analysis (PCA), these shifts could be
related to different physicochemical parameters with temperature, oxygen concentration, and the incident light being of paramount
importance as structuring variables. Comparison of RFLP and DGGE profiles by scoring similarities using the Jaccard coefficient
and then building a multidimensional scaling map (MDS) showed equivalent results. Both techniques revealed that bacterial
populations, present in the whole water column in the holomictic period, showed a high similarity with those located in the
deeper part of the lake in the stratified period, evidencing that other factors, both biotic and abiotic, should also be considered
as a force driving change in the composition of the bacterial community. Furthermore, DGGE analysis showed that sequences
from prominent bands were affiliated to members of four major phyla of the domain Bacteria: Cyanobacteria, Bacteroidetes, Proteobacteria, and Actinobacteria, most of which corresponded to heterotrophic bacterial populations involved in carbon, sulfide, and nitrogen biogeochemical
cycles, which were indistinguishable under the light microscope. 相似文献
995.
Victoria López-Rodas Fernando Marvá Eduardo Costas Antonio Flores-Moya 《Environmental and Experimental Botany》2008,64(1):43-48
At least six species of eukaryotic microalgae inhabit the acidic (pH 2.4–2.7), metal-rich mine waters from ponds in the copper mine district of Mynydd Parys (N Wales, UK). Consequently, these ponds constitute interesting natural laboratories for analysis of adaptation by microalgae to extremely stressful conditions. To distinguish between the pre-selective and post-selective origin of adaptation processes that allow the existence of microalgae in these ponds, a Luria-Delbrück fluctuation analysis was performed with the chlorophycean Dictyosphaerium chlorelloides isolated from non-acidic waters. In this analysis, natural Mynydd Parys pond water (MPW) was used as selective factor. Pre-selective, resistant D. chlorelloides cells appeared with a frequency of 1.6 × 10?6 per cell per generation. MPW-resistant mutants, with a diminished Malthusian fitness, are maintained in non-extreme waters as the result of a balance between new MPW-resistant cells arising by mutation and MPW-resistant mutants eliminated by natural selection (equilibrium at ca. 19 MPW-resistant per 107 wild-type cells). We propose that the microalgae inhabiting these stressful ponds could be the descendents of chance mutants that arrived in the past or are even arriving at the present. 相似文献
996.
Methane vents are of significant geochemical and ecological importance. Notable progress has been made toward understanding anaerobic methane oxidation in marine sediments; however, the diversity and distribution of aerobic methanotrophs in the water column are poorly characterized. Both environments play an essential role in regulating methane release from the oceans to the atmosphere. In this study, the diversity of particulate methane monooxygenase (pmoA) and 16S rRNA genes from two methane vent environments along the California continental margin was characterized. The pmoA phylotypes recovered from methane-rich sediments and the overlying water column differed. Sediments harbored the greatest number of unique pmoA phylotypes broadly affiliated with the Methylococcaceae family, whereas planktonic pmoA phylotypes formed three clades that were distinct from the sediment-hosted methanotrophs and distantly related to established methanotrophic clades. Water column-associated phylotypes were highly similar between field sites, suggesting that planktonic methanotroph diversity is controlled primarily by environmental factors rather than geographical proximity. Analysis of 16S rRNA genes from methane-rich waters did not readily recover known methanotrophic lineages, with only a few phylotypes demonstrating distant relatedness to Methylococcus. The development of new pmo primers increased the recovery of monooxygenase genes from the water column and led to the discovery of a highly diverged monooxygenase sequence which is phylogenetically intermediate to Amo and pMMO. This sequence potentiates insight into the amo/pmo superfamily. Together, these findings lend perspective into the diversity and segregation of aerobic methanotrophs within different methane-rich habitats in the marine environment. 相似文献
997.
Eukaryotic genomes are especially vulnerable to DNA damage during the S phase of the cell cycle, when chromosomes must be duplicated. The stability of DNA replication forks is critical to achieve faithful chromosome replication and is severely compromised when forks encounter DNA lesions. To maintain genome integrity, replication forks need to be protected by the S-phase checkpoint and DNA insults must be repaired. Different pathways help to repair or tolerate the lesions in the DNA, but their contribution to the progression of replication forks through damaged DNA is not well known. Here we show in budding yeast that, when the DNA template is damaged with the alkylating agent methyl methanesulfonate (MMS), base excision repair, homologous recombination and DNA damage tolerance pathways, together with a functional S-phase checkpoint, are essential for the efficient progression of DNA replication forks and the maintenance of cell survival. In the absence of base excision repair, replication forks stall reversibly in cells exposed to MMS. This repair reaction is necessary to eliminate the lesions that impede fork progression and has to be coordinated with recombination and damage tolerance activities to avoid fork collapse and allow forks to resume and complete chromosome replication. 相似文献
998.
Victoria Ng Patrick Tang Frances Jamieson Steven J. Drews Shirley Brown Donald E. Low Caroline C. Johnson David N. Fisman 《EcoHealth》2008,5(4):482-490
Legionella species are increasingly recognized as a cause of both healthcare- and community-acquired pneumonia (so-called “Legionnaire’s
disease”). These pathogens are ubiquitous in the environment, but environmental factors in the occurrence of sporadic legionellosis
remain poorly understood. We analyzed all legionellosis cases identified in the Greater Toronto Area of Ontario from 1978
to 2006, and evaluated seasonal and environmental patterns in legionellosis case occurrence by using both negative binomial
models and case-crossover analysis. A total of 837 cases were reported during the study period. After adjusting for seasonal
effects, changes in the local watershed, rather than weather, were the strongest contributors to legionellosis risk. A 3.6-fold
increase (95% confidence interval (CI), 2.4–5.3) in odds of disease was identified with decreasing watershed levels approximately
4 weeks before case-occurrence. We also found a 33% increase (95% CI, 8–64%) in odds of disease with decreasing lake temperature
during the same period and a 34% increase (95% CI, 14–57%) with increasing humidity 5 weeks before case-occurrence. We conclude
that local watershed ecology influences the risk of legionellosis, notwithstanding the availability of advanced water treatment
capacity in Toronto. Enhancement of risk might occur through direct contamination of water sources or via introduction of
micronutrients or commensal organisms into residential and hospital water supplies. These observations suggest testable hypotheses
for future empiric studies. 相似文献
999.
Biosynthesis of isoprenoids: studies on the mechanism of 2C-methyl-D-erythritol-4-phosphate synthase
2C-Methyl-D-erythritol-4-phosphate synthase, encoded by the ispC gene (also designated dxr), catalyzes the first committed step in the nonmevalonate isoprenoid biosynthetic pathway. The reaction involves the isomerization of 1-deoxy-D-xylulose 5-phosphate, giving a branched-chain aldose derivative that is subsequently reduced to 2C-methyl-D-erythritol 4-phosphate. The isomerization step has been proposed to proceed as an intramolecular rearrangement or a retroaldol-aldol sequence. We report the preparation of (13)C-labeled substrate isotopologs that were designed to optimize the detection of an exchange of putative cleavage products that might occur in the hypothetical retroaldol-aldol reaction sequence. In reaction mixtures containing large amounts of 2C-methyl-D-erythritol-4-phosphate synthase from Escherichia coli, Mycobacterium tuberculosis or Arabidopsis thaliana, and a mixture of [1-(13)C(1)]-2C-methyl-D-erythritol 4-phosphate and [3-(13)C(1)]2C-methyl-D-erythritol 4-phosphate, the reversible reaction could be followed over thousands of reaction cycles. No fragment exchange could be detected by NMR spectroscopy, and the frequency of exchange, if any, is less than 5 p.p.m. per catalytic cycle. Hydroxyacetone, the putative second fragment expected from the retroaldol cleavage, was not incorporated into the enzyme product. In contrast to other reports, IspC did not catalyze the isomerisation of 1-deoxy-D-xylulose 5-phosphate to give 1-deoxy-L-ribulose 5-phosphate under any conditions tested. However, we could show that the isomerization reaction proceeds at room temperature without a requirement for enzyme catalysis. Although a retroaldol-aldol mechanism cannot be ruled out conclusively, the data show that a retroldol-aldol reaction sequence would have to proceed with very stringent fragment containment that would apply to the enzymes from three genetically distant organisms. 相似文献
1000.
RepA, the replication initiator protein from the Pseudomonas plasmid pPS10, regulates plasmid replication and copy number. It is capable of autorepression, in which case it binds as a dimer to the inverted repeat operator sequence preceding its own gene. RepA initiates plasmid replication by binding as a monomer to a series of four adjacent iterons, which contain the same half-repeat as found in the operator sequence. RepA contains two domains, one of which binds specifically to the half-repeat. The other is the dimerization domain, which is involved in protein-protein interactions in the dimeric RepA-operon complex, but which actually binds DNA in the monomeric RepA-iteron complex. Here, detailed fluorescence studies on RepA and an N-(iodoacetyl)aminoethyl-8-naphthylamine-1-sulfonic acid-labeled single-cysteine mutant of RepA (Cys160) are described. Using time-resolved fluorescence depolarization measurements, the global rotational correlation times of RepA free in solution and bound to the operator and to two distinct iteron dsDNA oligonucleotides were determined. These provide indications that, in addition to the monomeric RepA-iteron complex, a stable dimeric RepA-iteron complex can also exist. Further, F?rster resonance energy transfer between Trp94, located in the dimerization domain, and N-(iodoacetyl)aminoethyl-8-naphthylamine-1-sulfonic acid-Cys160, located on the DNA-binding domain, is observed and used to estimate the distance between the two fluorophores. This distance may serve as an indicator of the orientation between both domains in the unbound protein and RepA bound to the various cognate DNA sequences. No major change in distance is observed and this is taken as evidence for little to no re-orientation of both domains upon complex formation. 相似文献