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81.
Plasmid pUCD607 was mobilized into the biocontrol agent Enterobacter cloacae strain E6 by conjugation and the resultant strain, E6(pUCD607), was bioluminescent. Biocontrol of Pythium ultimum by E6(pUCD607) was similar to that of the parent strain, E6. The location of E6(pUCD607) in the soil and in the rhizosphere
of lettuce was readily determined by pressing agar medium against plant roots in a root box, allowing the bacteria to grow
overnight on the medium, and detecting the presence of bioluminescence by autophotography. There was a positive, linear correlation
between population sizes determined by dilution plating and the quantity of light emitted due to bioluminescence. However,
both the intercept and slope of this line varied among experiments possibly due to the differing physiological states of cells
recovered from soils. The amount of light emitted by the bioluminescent strain E6(pUCD607) was not quantitative. This technique
is useful for qualitative determinations of populations and for photographically locating bacteria. 相似文献
82.
From among 125 strains of fluorescent and 52 strains of nonfluorescent bacteria initially screened in the laboratory for their
antibiosis towards the bacterial wilt pathogen, Pseudomonas solanacearum, strain Pfcp of Pseudomonas fluorescens and strains B33 and B36 of Bacillus spp., were chosen and evaluated further in greenhouse and field tests. Pfcp treated banana (Musa balbisiana), eggplant and tomato plants were protected from wilt upto 50, 61 and 95% in greenhouse and upto 50, 49 and 36% respectively
in field. Protection afforded by the Bacillus strains was lower. In bacteria-treated plants which were subsequently inoculated
with P. solanacearum plant height and biomass values increased and were close to those of nontreated and noninoculated control plants. 相似文献
83.
Versieck Jacques Vanballenberghe Lidia Wittoek Ann Vermeir Gerda Vandecasteele Carlo 《Biological trace element research》1990,(1):683-689
A method is described for the determination of mercury in human blood serum and packed blood cells employing neutron activation
analysis. Great attention was devoted to the collection and manipulation of the samples. The accuracy and precision of the
method were tested by analyzing biological reference materials and by comparing the concentrations measured in a number of
serum samples to those obtained by another, independent technique (cold vapor atomic absorption spectrometry) in the same
samples. The article reports the levels measured in blood serum and packed blood cells samples from 15 adult volunteers, as
well as the figures determined in a “second-generation” biological reference material (freeze-dried human serum), prepared
and conditioned at the University of Ghent. 相似文献
84.
Edward J. B. Beeley P. A. Bennett L. G. I. Poland J. S. 《Biological trace element research》1990,(1):53-61
A microcomputer-controlled irradiation and measurement system and a microprocessor-controlled sample changer have been installed
at the SLOWPOKE-2 Facility at the Royal Military College of Canada (RMC). These systems can provide the gamut of instrumental
neutron activation analysis (INAA) techniques for the analyst. Custom software has been created for system control, data acquisition,
and off-line spectral analysis using programs that incorporate Gaussian peak-fitting methods of analysis. The design and use
of the equipment is discussed, and the performance is illustrated with results obtained from the analysis of marine sediment
and biological reference materials. 相似文献
85.
Transformed plants with elevated levels of chloroplastic SOD are not more resistant to superoxide toxicity 总被引:29,自引:0,他引:29
The petunia nuclear gene which encodes the chloroplast isozyme of superoxide dismutase, SOD-1, has been fused with an efficient rbcS promoter fragment and 3 flanking region and introduced into tobacco and tomato cells. Transformed plants carrying this chimeric gene have up to 50-fold the levels of SOD-1 which occur in wild-type plants. However, tobacco plants with 30-to 50-fold the normal SOD-1 activity do not exhibit resistance to the light-activated herbicide paraquat. Similarly, tomato plants with 2-to 4-fold increases in SOD-1 do not exhibit tolerance to photoinhibitory conditions known to increase superoxide levels (high light, low temperatures and low CO2 concentrations). Our data indicate that increasing the chloroplastic SOD level in a plant cell is not sufficient to reduce the toxicity of superoxide. 相似文献
86.
旱地作物生态工程的设计 总被引:1,自引:1,他引:0
旱地作物生态工程是运用生态学和系统科学的原理和方法而设计和组建的旱地作物生产工艺体系。它把作物及其环境作为一个系统,统筹兼顾,相互协调,全面安排,综合利用。其最终目标是建立高效的,相对平衡的旱地作物生态系统。工程的最大特点在于它的整体性和综合性。它是作物先进生产技术的科学组装 相似文献
87.
Following the successful introduction ofEpidinocarsis lopezi (De Santis) for biological control of the cassava mealybug (CM)Phenacoccus manihoti Mat.-Ferr. in southwestern Nigeria in 1981 and 1982, 11 groups of cassava fields were sampled every 2 weeks up to 1988 for
impact assessment. After 1984, CM populations remained mostly below 10 per tip despite the presence of native hyperparasitoids,
demonstrating the long-term success of biological control byE. lopezi in the region. Indigenous polyphagous coccinellids were found only during peak host densities, whereas the specificE. lopezi was common throughout the year. During some periods, percentage parasitism indicated delayed density dependence. Since 89%
of all sampled cassava tips had no CM at all and the parasitisme is very mobile, parasitization rates were also calculated
for individual infested tips (N=4,878). Parasitism increased slightly with host density on tips having between 1 and 10 CM
of the 3rd and 4th instars, indicating positive density dependence. Such tips comprised 64% of all infested tips. At higher host densities,
parasitism rates fell rapidly. The results are discussed in view of different theories on population regulation by biological
control agents.
相似文献
88.
The biology and host specificity of the seed-feeding bruchids,Acanthoscelides quadridentatus (Schaeffer) andA. puniceus Johnson, from Mexico were studied in quarantine facilities in Australia. Distinguishing characters in the genitalia of each
species are illustrated. Oviposition was recorded on 16 of 73 species of plants tested but larvae died without entering pods
or seeds, except onMimosa invisa K. F. P. von Martius andM. pigra L. Larvae entering seeds ofM. invisa died in the first instar. The bruchids were clearly specific toM. pigra and were subsequently released as part of a program for biological control of this weed in the Northern Territory, Australia
in April 1983 and thailand in July 1984.
相似文献
89.
R. C. H. Shepherd 《BioControl》1990,35(4):583-587
Host specificity tests carried out in the laboratory in Australia during 1977, showed thatMicrothrix inconspicuella Ragonot could develop on young apple leaves (Harley
et al., 1979). Field studies in unsprayed apple orchards in South Africa showed that some feeding occurred, but fewer than 40% of
late instar larvae developed to adults when confined in sleeves on apple tree branches. No feeding or survival occurred in
large field cages or in the open. Adults which developed from apple fed larvae were smaller, deformed, occasionally mated
and laid fertile eggs but their progeny did not feed or develop on apple fruit or leaves. In conclusion,M. inconspicuella larvae did not develop on apple fruit or leaves in the field, damage was mainly limited to apples already injured and feeding
on leaves was minimal. Under normal pest control practicesM. inconspicuella populations did not survive on any part of the apple tree or onE. australis growing under the trees.
相似文献
90.
Rearing techniques and results of preliminary host range tests are reported forHadena perplexa (Denis & Schiffermuller) (Lep.: Phalaenidae) a candidate biocontrol agent against the weed bladder campion,Silene vulgaris (Moench) Garcke, in Manitoba, Canada. In the laboratory, it was necessary to pipette a 15% honey solution in water into the
flowers as food for the adult moths. When reared singly to avoid cannibalism, 56% of the 1st instar larvae developed to pupae. Larvae fed on a natural diet for 10 days can then be reared on either one of 2 artificial
diets. Choice oviposition tests and no-choice larval feeding tests were conducted with plant species closely related toS. vulgaris in the generaSilene, Dianthus, Gypsophila, Lychnis, Saponaria. Species in 4 of 5 of these genera were accepted for oviposition, and species in all 5 genera supported the development of
1st instar larvae to the pupal stage.H. perplexa should not be introduced into Canada.
相似文献