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931.
932.
933.
934.
I. Watanabe 《Soil biology & biochemistry》1977,9(2):99-103
Soil samples from field plots that had received annual applications of pentachlorophenol (PCP) for 3 consecutive years were analyzed each year for changes in microbial populations, particularly in PCP-decomposing microorganisms and PCP-tolerant bacteria. Within 6 weeks after an initial application of PCP, PCP-decomposing microorganisms increased by about 3 orders of magnitude; this increased population was still observed the following spring. The number of PCP-decomposing microorganisms in the soils that received PCP for 3 yr reached 105· g?1 soil or more, while that in soils without PCP was 102· g?1. The soils that received PCP were not enriched with tetrachlorophenoldecomposing microorganisms. The microbes enriched by PCP may have been bacterial in nature. In 1972 and 1974, the number of PCP-tolerant bacteria increased immediately after PCP application and continued to increase for 2 weeks, then declined. The 1973 data, however, showed no such decline. The number of PCP-tolerant and of crystal violet-tolerant (Gram-negative) bacteria correlated fairly well except at 2 weeks after PCP application (when PCP-tolerant bacteria were more numerous). 相似文献
935.
The ability of fluorescein isothiocyanate (FITC) labelled lectins extracted from the legumes Aspalathus linearis, Glycine max, Lotononis bainesii, Phaseolus vulgaris and Pisum sativum, respectively, to react with strains of various Rhizobium spp. was studied. With the exception of six out of ten strains of R. phaseoli and two out of ten strains of R. japonicum, none of the Rhizobium strains tested were able to bind lectin from their normal host plants. Many strains of R. leguminosarum, R. trifolii and R. phaseoli bound each of the plant lectins studied with the exception of the P. sativum lectin. This lectin was only bound by two strains of R. meliloti and a slow-growing strain isolated from Macroptilium atropurpureum. These results do not support suggestions by other workers that plant lectins play an important role in Rhizobium specificity. 相似文献
936.
Soybean nodules subjected to water stress showed lowered C2H2 reducing activity and O2 uptake, but enhanced CO2 and ethanol evolution. Similar results were obtained with waterlogged nodules. The effects of stress could be partially or completely overcome by increaseing the O2 supply. It is concluded that both water deficiency and excess may depress nitrogenase activity (C2H2 reduction) by restricting supplies of intermediates from aerobic pathways. At the same time fermentative pathways are stimulated and could lead to inhibitory concentrations of ethanol being produced. Both symbionts possess systems for ethanol production. 相似文献
937.
C J Mirocha S V Pathre J Behrens 《Journal of the Association of Official Analytical Chemists》1976,59(1):221-223
Two substances interfering with the gas-liquid chromatographic (GLC) detection of T-2 mycotoxin were identified as 1-glyceryl-monooleate and 1-glycerylmonolinoleate. These monoglycerides are natural products formed by species of Fusarium growing on cereal grains and are also additives contained in liquid vegetable and animal fats added to the feed mixture. The monoglycerides can be removed from the analytical sample by resolution by thin layer chromatography prior to separation by GLC. Trimethylsilyl ether derivatives of the monoglycerides and T-2 toxin have almost identical retention times on 3% OV-1 columns, whereas the trifluoroacetyl and pentafluoropropionyl derivatives give baseline separation on the same column. The monoglycerides can be misidentified as the T-2 toxin in analyses involbing GLC. 相似文献
938.
Addition of urea to Iowa soils did not induce urease activity, but production of urease activity was observed on addition of glucose and other organic materials that promote microbial activity. The persistence of the urease activity produced on addition of these materials varied with the soil, but, with each soil studied, the urease activity after addition of organic materials eventually was identical to that of the unamended soil. No increase or decrease in urease activity was observed when unamended or urea-treated soils were incubated under aerobic conditions for several months. It is concluded that soil constituents protect urease against microbial degradation and other processes leading to inactivation of enzymes and that every soil has a stable level of urease activity determined by the ability of its constituents to provide this protection. 相似文献
939.
V. Rajaramamohan-Rao 《Soil biology & biochemistry》1976,8(5):445-448
The effect of moisture and (NH4)2SO4 on N2 fixation in a paddy soil was investigated employing C2H2 reduction assay and 15N-tracers. N2 fixation was negligible under nonflooded conditions. Soil submergence accelerated N2 fixation; with a further increase in N2 fixation when the flooded soil was incubated under an Ar atmosphere. Rice straw additions to both moist and flooded soils enhanced N2 fixation. N2-ase activity in the soil decreased with increasing concentration of added N although complete suppression of the activity was not evident even at concentrations as high as 160–320 parts/106 N. A similar trend of inhibition by N was also noticed in soils amended with glucose or cellulose in combination with N. However, the inhibitory effect of N decreased with increased incubation of soil except at 320 parts/106 N. 相似文献
940.
The reactions of five early and five late varieties of perennial ryegrass to stimulation of bulky autumn growth and deferment of harvesting were compared in terms of spring growth and subsequent recovery during three winters. Winterkill was marked in 1971–72, particularly when harvesting was deferred to late November, in early varieties S24 and Presto Pajbjerg and in the late variety S23. Least affected among early varieties were Premo and Barvestra (tetraploid) and among late varieties, Perma and Barpastra (tetraploid). All varieties showed rapid recovery. The results are discussed in terms of the significance of winterkill, and the effects of age of sward, variety susceptibility and deferment of autumn defoliation. It is concluded that the form of winterkill which occurs in the west of Scotland can have serious consequences to farm productivity in severe winters. Autumn growth left standing into November can also lead to winterkill. Under good management, varietal differences are unimportant. In a severe winter, no varieties of perennial ryegrass are reliable. 相似文献