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21.
Impact of biological activity on detritus transported in the lower river Rhine: an exercise in ecosystem analysis 总被引:4,自引:0,他引:4
SUMMARY. 1. Published data are used to construct a tentative carbon budget for the ecosystem of the lower river Rhine and its sedimentation areas in The Netherlands.
2. It is estimated that 287 × 106 kg Cy−1 of particulate organic material is transported by the river Rhine, and 100 × 106 kgCy−1 of this material is deposited in the delta.
3. Phytoplankton and nitrifying bacteria seem to contribute significantly to the carbon budget, by producing c. 78 × 106 kgCy−l .
4. The mineralization in the water (estimated from routine determinations of biological oxygen demand and from in situ diurnal fluctuations of oxygen) and in the bottom (estimated from the denitrification rates in the delta, from the production rate of methane and from overall oxygen consumption) is shown to degrade c. 50% of the carbon input plus autochthonous production.
5. The carbon budget and oxygen regime in the lower Rhine suggest that after decades of severe organic pollution the river has more or less resumed the normal, slightly heterotrophic state of a large lowland river. 相似文献
2. It is estimated that 287 × 10
3. Phytoplankton and nitrifying bacteria seem to contribute significantly to the carbon budget, by producing c. 78 × 10
4. The mineralization in the water (estimated from routine determinations of biological oxygen demand and from in situ diurnal fluctuations of oxygen) and in the bottom (estimated from the denitrification rates in the delta, from the production rate of methane and from overall oxygen consumption) is shown to degrade c. 50% of the carbon input plus autochthonous production.
5. The carbon budget and oxygen regime in the lower Rhine suggest that after decades of severe organic pollution the river has more or less resumed the normal, slightly heterotrophic state of a large lowland river. 相似文献
22.
REINDERS J. E. A.; AS H. VAN; SCHAAFSMA T. J.; DE JAGER P. A.; SHERIFF D. W. 《Journal of experimental botany》1988,39(9):1199-1210
In this paper we demonstrate the study of plant water balanceby the non-invasive measurement of tissue water content andwater flow using proton nuclear magnetic resonance (NMR). Sapvelocity and flux were measured independently in the presenceof an excess of stationary tissue water. The instrumentationdescribed allows automated and unattended measurement of flow-and water content-variables in a well-defined region of theplant over periods of several days, with a time resolution betweensuccessive measurements of c. 5 s. Using this apparatus theeffect of changes in light intensity (day/night rhythm) andrelative humidity on stem tissue water content as well as onthe velocity and flux of xylem sap in the stem were investigatedin a cucumber plant. The results are in agreement with predictionsfrom a simple model for plant water balance, which is basedon water potential, flow rate and resistance to flow. As longas only transpiration is varied, flow rate and water content(or potential) are affected in opposite ways as demonstratedin this paper. In contrast, the model predicts that changesin uptake (resulting from changes in, for example, root resistance)will induce changes in water content and flow in the same direction.An experimental verification of this prediction is given ina subsequent paper, where, in addition, the NMR results arecompared to those obtained with a dendrometer. Key words: Water balance model, Cucumis sativus L., flow, water content, NMR, water balance measurement 相似文献
23.
MURALITHARAN MORLEY S.; CHANDLER STEPHEN F.; VAN STEVENINCK REINHARD F. M. 《Annals of botany》1992,69(5):459-465
Non-selected and Na2SO-, K2SO4- or KCl-selected callus culturesof Vaccinium corymbosum L. cv. Blue Crop were grown on mediasupplemented with 0, 25 and 50 mM Na2SO4 (non-selected and Na2SO(-selectedonly), 0, 25 and 50mMK2SO4 (non-selected and K2SO4-selectedonly) or 0, 50 and 100 mM KCl (non-selected and KCl-selectedonly). On all media, growth of selected callus (on a fresh-weightor dry-weight basis) was greater than that of non-selected callus,and selected callus grew optimally on the level and type ofsalt on which it was selected. Selected callus was friable andmaintained a higher f. wt:d. wt ratio. Tissue water potentialin selected callus was more negative than in non-selected callus. Flame photometry and chloridometry showed Na+, K+ and Claccumulated in callus to concentrations equal to or greaterthan the initial concentration in the medium. Turbidometry showedthat tissue SO42- concentration was lower than the concentrationin the medium. In most cases selected callus accumulated moreNa+, Ksup, SO42 or Cl than non-selected callus.Vacuolar ion concentration was measured by electronprobe X-raymicroanalysis, and on most media selected callus had highervacuolar ion concentrations than non-selected callus. SO42and Cl were accumulated in the vacuoles at concentrationshigher than the external medium, but vacuolar Na+ concentrationdid not reach external concentration on Na2SO4 and on potassiumsalts was maintained between 12 and 17 mM. Vacuolar K+ concentration(approx. 142191 mM on no salt) decreased on Na2SO4 andincreased on K2SO4 and KCl. There was no precise correlation between total or specific ionaccumulation (Na+, K+, SO42 and Cl and fresh-weightyield. Results suggest that selection results in adaptationin response to decreased water potential of the medium. Vaccinium corymbosum, blueberry, electronprobe X-ray microanalysis, callus, in vitro selection, salt tolerance, KCl, K2SO4, Na2SO4 相似文献
24.
CROES A. F.; CREEMERS-MOLENAAR TINEKE; VAN DEN ENDE G.; KEMP ANKE; BARENDSE G. W. M. 《Journal of experimental botany》1985,36(11):1771-1779
Croes, A. F., Creemers-Molenaar, T., van den Ende, G., Kemp,A. and Barendse, G. W. M. 1985. Tissue age as an endogenousfactor controlling in vitro bud formation on explants from theinflorescence of Nicotiana tabacum L.J. exp. Bot. 36:17711779. The in vitro formation of generative buds was studied on explantsfrom flower and fruit stalks and from internodes of the floralramifications of tobacco. A floral gradient was found to existalong the axis of the branch. The gradient concerns the numberof flower buds formed in vitro and is present in both typesof tissues. The number of flower buds is greater on tissuesfrom the apical than from the basal portion of the branch. Thecapacity to generate these buds is largely determined by tissueage at the moment of the excision. Consequently, the gradientmoves along the axis during the outgrowth of the inflorescence. The alternative possibility that some apex-derived stimuluspredetermines the morphogenetic capacity of the tissue priorto excision is excluded by the observation that the gradientremains virtually unaltered if the apex is removed one weekbefore the onset of culturing. Auxin affects the floral gradient Increasing the auxin concentrationin internode tissue culture causes a steeper gradient of flowerbud generation by almost completely abolishing bud formationon older tissues. Key words: Auxin, flower buds, gradient, tissue culture, tobacco 相似文献
25.
J. L. VAN HOUTEN R. SMITH J. WYMER B. PALMER M. DENARO 《The Journal of eukaryotic microbiology》1985,32(4):613-616
Normal Paramecium tetraurelia cells stained with fluorescein-conjugated folate show intense fluorescence that can be reduced to near background autofluorescence with excess K2-folate, but not with excess KCl. Mutant d4–534, which is not attracted to folate and does not specifically bind 3H-folate, shows reduced fluorescence when stained. This method of monitoring specific folate binding to cells can be adapted to a microscale for rapid screening of clones since cells are routinely fixed and stained in microtiter wells. 相似文献
26.
C. G. G. J. VAN STEENIS 《Botanical journal of the Linnean Society. Linnean Society of London》1984,89(4):289-292
From the altitudinal ranges of species recorded for the Malesian mountain flora, in Flora of Java and the 6 or so volumes of Flora Malesiana it was concluded that there are critical altitudes where the floristic composition shows rather abrupt demarcations, namely at 1000, 1500, 2400 and 4000 m altitude. In a generalized way this also holds for the structure and stature of the vegetation. For cultivated plants the altitudes of 1000 and 1500 m are also distinct demarcations. 相似文献
27.
A. H. Havelaar † W. M. Hogeboom V. M. Sekhuis E. H. W. VAN Erne 《Journal of applied microbiology》1987,62(6):555-564
In a 3-year period, four series of simulated water samples containing selected test strains were distributed to more than 50 laboratories in The Netherlands for bacteriological testing. Participating laboratories examined the samples by enrichment or membrane filtration methods, or both, for total coliform organisms, thermotol-erant coliform organisms, faecal streptococci and standard plate counts (37˙ and 22˙C) according to Dutch standard methods. The results were quantitatively satisfactory: the distribution of positive and negative results with subsamples conformed to stochastic variation; the standard deviation of membrane or plate counts was usually in the range which may be expected from a Poisson distribution, and there was good correspondence between average counts in participating laboratories and those expected from controls in the organizing laboratory. Problems of a qualitative nature were frequently encountered, however. Among them were a false positive response with a strain of Enterobacter cloacae in the thermotolerant coliform test; a false positive result with Clostridium perfringens in enrichment tests for total or thermotolerant coliform organisms and false positive results with Micrococcus varians in the faecal streptococcus test by membrane filtration. It is concluded that quality assessment should be a consistent activity in water microbiology laboratories. For this purpose, stable and well characterized reference materials are needed. 相似文献
28.
南瓜雌蕊与自花及远缘花粉的相互作用 总被引:2,自引:0,他引:2
南瓜柱头表面经去垢剂、蛋白酶及Con A处理后花粉不能萌发或花粉管生长受阻,Con A能专一地与柱头表面结合。柱头块加入培养液可促进花粉萌发。不同的远缘花粉授粉后在雌蕊不同部位受阻。在成熟南瓜雌蕊提取液中检测到血凝活性,凝集素可能参与雌蕊对远缘花粉的抑制。 相似文献
29.
KOJI NAKANISHI STEVEN BLOBSTEIN MAKOTO FUNAMIZU NOBUO FURUTACHI GEORGE VAN LEAR DEZIDER GRUNBERGER KARL W. LANKS I. BERNARD WEINSTEIN 《Nature: New biology》1971,234(47):107-109
WE wish to report that reconstituted sperm whale myoglobin prepared by the method of Breslow1 (except that pH 2 was found sufficient to remove all the haem) (I) crystallizes2 in a different habit from those prepared by the method of Rossi-Fanelli et al.3 (II) using haemin of Sigma lot 77B-0220 and our own 57Fe photoporphyrin preparation and the native myoglobin (III). Although all three form type A3 monoclinic prisms, the best developed plane is [001] for II and III, it is [100] for I. There seems to be great interest in reconstituted haemoproteins4,5, so it is important that crystallization habit may be a sensitive test for subtle changes in protein structures. 相似文献
30.
Admissible clustering procedures 总被引:3,自引:0,他引:3