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991.
Growth versus molting time of caterpillars as a function of temperature,nutrient concentration and the phenolic rutin 总被引:1,自引:0,他引:1
Nancy E. Stamp 《Oecologia》1990,82(1):107-113
Summary A factorial experiment tested the effects of varying nutrient concentration (normal versus diluted), presence or absence of the phenolic allelochemical rutin and daytime temperature (20, 25 and 30° C) on growth, molting and food utilization efficiencies of tobacco hornworms (Manduca sexta). Two of the utilization efficiencies (approximate digestibility and efficiency of conversion of ingested food) were unaffected by temperature; the third one, efficiency of conversion of digested food, was affected by temperature but there was no consistent effect. Lower temperatures significantly increased the proportion of the stadium spent molting, with larvae at a daytime temperature of 20° C spending 9% more of the stadium in molting than larvae at 30° C. Growth time was not influenced by nutrient concentration. When temperature was low and rutin absent, molt time and the proportion of the stadium spent molting were affected by nutrient concentration. Addition of the phenolic rutin did not have an appreciable effect on growth time or digestive processes. However, it increased molting time by 7 to 14% and thus increased the duration of the stadium and reduced relative growth rate. These results indicate that the effect of food quality on growth rate is a function of the thermal conditions of insect herbivores. At cooler temperatures, a disproportionate increase in time spent molting, rather than altered food utilization efficiencies, contributed to lower growth rates. The consequences for larval growth of fluctuating temperatures due to diurnal cycles and the presence of predators forcing larvae into thermally suboptimal microhabitats are discussed. 相似文献
992.
993.
A procedure for the culture in vitro of isolated small berries of Vitis vinifera L. cv. Muscat of Alexandria in a Murashige and Skoog basal medium supplemented with N6 -benzyladenine and indoleacetic acid is described. Berries developed well in culture during 60 days and tripled in size, but remained green and smaller than normal berries grown in vivo. Some callus formed on the distal end of the berry, and where major skin damage occurred, callus emerged from the cracked berries. In order to examine their biosynthetic competency, berries which were previously cultured in vitro for 60 days were incubated for 48 h in a Murashige and Skoog medium containing a [14 C]-labelled water-soluble fraction. This fraction was isolated from grape berries located adjacent to a leaf that had been exposed to gaseous 14 CO2 in full sunlight for 5 h. The berries were then recultured for 48 h after which a glycosidic fraction was isolated on a C18 reversed phase column and further separated by thin layer chromatography (TLC). The major labelled band corresponded to the geranyl-β-rutinoside marker, indicating that grape berries have the ability to synthesize monoterpene glycosides. This band also consisted of other monoterpene glycosides as revealed by the gas chromatography-mass spectrometry (GC-MS) analysis of their aglycones (released by enzymatic hydrolysis). 相似文献
994.
The governing factors for soil nitrogen dynamics were identified with a simulation model. In addition, the model was used to interpret measurements from a plot fertilisation experiment in southwest Sweden.Simulated moisture and temperature conditions were the driving variables for the simulation of soil nitrogen dynamics and leaching during a 6-year period. The results of the simulation were compared with monthly observations on two plots with grain crops, one with liquid manure and commercial fertilisers applied and one with commercial fertilisers only.Simulated temporal variations of the nitrate and ammonium storages generally agreed with observations. The dominant role of the crops as a determinant of soil nitrogen conditions was demonstrated. A higher leaching loss from the plot with application of commerical fertilisers only occurred both in simulations and measurements compared to the plot with application of both commercial fertilisers and manure. The main reason was the higher N-application in the former treatment.The effect of water flows in macropores was interpreted as a delay of simulated leaching compared to observed leaching on some occasions in summer and early autumn. No direct effect of the macropores on the yearly rates of leaching could be seen. 相似文献
995.
The effect of phosphorus (P) concentration in barley seed on seedling growth has not been much investigated. Consequently,
two experiments were conducted in the greenhouse to determine the effect of P concentration in barley seed (Hordeum vulgare L., cv. Empress) on the seedlings grown in sand-filled boxes receiving a culture solution without P. Seeds were selected
with three P concentrations: high-P (113.0 mmol P kg−1), medium-P (80.7 mmol P kg−1) and low-P (54.9 mmol P kg−1). At 21 days after sowing, the shoot and root yield or shoot height was the least with seedlings from low-P seed. In the
other experiment, high-P and low-P seeds were wetted with distilled water or with a solution of 25.8 cmol L−1 of NaH2PO4 for 24 h, and then grown for 31 days. Solution P had been imbibed by seeds whether low or high in native P, but only the
imbibed P held by low native P seed benefited seedling dry matter accumulation and shoot elongation. The lack of benefit from
seed-imbibed P on seedlings grown from high-P barley seed was associated with low recovery of the imbibed P in those seedlings. 相似文献
996.
Cortical microtubules (MTs) in protoplasts prepared from tobacco (Nicotiana tabacum L.) BY-2 cells were found to be sensitive to cold. However, as the protoplasts regenerated cell walls they became resistant
to cold, indicating that the cell wall stabilizes cortical MTs against the effects of cold. Since poly-l-lysine was found to stabilize MTs in protoplasts, we examined extensin, an important polycationic component of the cell wall,
and found it also to be effective in stabilizing the MTs of protoplasts. Both extensin isolated from culture filtrates of
tobacco BY-2 cells and extensin isolated in a similar way from cultures of tobacco XD-6S cells rendered the cortical MTs in
protoplasts resistant to cold. Extensin at 0.1 mg·ml−1 was as effective as the cell wall in this respect. It is probable that extensin in the cell wall plays an important role
in stabilizing cortical MTs in tobacco BY-2 cells. 相似文献
997.
998.
Estimation of the effect of photoinhibition on the carbon gain in leaves of a willow canopy 总被引:21,自引:0,他引:21
The occurrence of photoinhibition of photosynthesis in leaves of a willow canopy was examined by measuring the chlorophyll-a fluorescence ratio of F
V/F
M (FM is the maximum fluorescence level of the induction curve, and FV is the variable fluorescence, F
V=F
M–F
0, where F0 is the minimal fluorescence). The majority of the leaves situated on the upper parts of peripheral shoots showed an afternoon inhibition of this ratio on clear days. This was the consequence of both a decrease in F
M and a rise in F
O. In the same leaves the diurnal variation in intercepted photosynthetic photon flux density (PPFD) was monitored using leaf-mounted sensors. Using the multivariate method, partial least squares in latent variables, it is shown that the dose of PPFD, integrated and linearly weighted over the last 6-h period, best predicts photoinhibition. Photoinhibition occurred even among leaves that did not intercept PPFDs above 1000 mol·m–2·s–1. Exposure of leaves to a standard photoinhibitory treatment demonstrated that the depression in the F
V/F
M ratio was paralleled by an equal depression in the maximal quantum yield of CO2 uptake and a nearly equal depression in the rate of bending (convexity) of the light-response curve of CO2 uptake. As a result, the rate of net photosynthesis is depressed over the whole natural range of PPFD. By simulating the daily course in the rate of net photosynthesis, it is estimated that in the order of one-tenth of the potential carbon gain of peripheral willow shoots is lost on clear days as a result of photoinhibition. This applies to conditions of optimal temperatures. Photoinhibition is even more pronounced at air temperatures below 23° C, as judged from measurements of the FV/FM ratio on clear days: the afternoon inhibition of this ratio increased in a curvilinear manner from 15% to 25% with a temperature decrease from 23° to 14° C.Abbreviations and Symbols FO
minimum fluorescence
- FV
variable fluorescence
- FM
maximum fluorescence
- PLS
partial least squares in latent variables
- PPFD
photosynthetic photon flux density
- VPD
water vapour-pressure deficit
This study was supported by the Swedish Natural Science Research Council. We are indebted to Dr. Jerry Leverenz (Department of Plant Physiology, University of Umeå, Sweden) for guidance with the modelling of the photosynthesis data. 相似文献
999.
We studied the effects of various polyamines on bud regeneration in thin-layer tissue explants of vegetative and floweringNicotiana tabacum L. cv. Wisconsin 38, in which application of exogenous spermidine (Spd) to vegetative cultures causes the initiation and
development of some flower buds (Kaur-Sawhney et al. 1988 Planta173, 282). We now show that this effect is dependent on the time and duration of application, Spd being required from the start
of the cultures for about three weeks. Neither putrescine nor spermine is effective in the concentration range tested. Spermidine
cannot replace kinetin (N6-furfurylaminopurine) in cultures at the time of floral bud formation, but once the buds are initiated in the presence of
kinetin, addition of Spd to the medium greatly increases the number of floral buds that develop into normal flowers. Addition
of Spd to similar cultures derived from young, non-flowering plants did not cause the appearance of floral buds but rather
induced a profusion of vegetative buds. These results indicate a morphogenetic role of Spd in bud differentiation.
Dedicated to Professor Hans Mohr on the occasion of his 60th birthday 相似文献
1000.
λ-Glutamylcysteine synthetase in higher plants: catalytic properties and subcellular localization 总被引:1,自引:0,他引:1
λ-Glutamylcysteine synthetase activity (EC 6.3.2.2) was analysed in Sephacryl S-200 eluents of extracts from cell suspension
cultures ofNicotiana tabacum L. cv. Samsun by determination of λ-glutamylcysteine as its monobromobimane derivative. The enzyme has a relative molecular
mass (Mr) of 60000 and exhibits maximal activity at pH 8 (50% at pH 7.0 and pH9.0) and an absolute requirement for Mg2+. With 0.2mM Cd2+ or Zn2+, enzyme activity was reduced by 35% and 19%, respectively. Treatment with 5 mM dithioerythritol led to a heavy loss of activity
and to dissociation into subunits (Mr 34000). Buthionine sulfoximine andl-methionine-sulfoximine, known as potent inhibitors of λ-glutamylcysteine synthetase from mammalian cells, were found to be
effective inhibitors of the plant enzyme too. The apparent Km values forl-glutamate,l-cysteine, and α-aminobutyrate were, respectively, 10.4mM, 0.19 mM, and 6.36 mM. The enzyme was completely inhibited by glutathione
(Ki=0.42 mM). The data indicate that the rate of glutathione synthesis in vivo may be influenced substantially by the concentration
of cysteine and glutamate and may be further regulated by feedback inhibition of λ-glutamylcysteine synthetase by glutathione
itself. λ-Glutamylcysteine synthetase is, like glutathione synthetase, localized in chloroplasts as well as in the cytoplasm.
Chloroplasts fromPisum sativum L. isolated on a Percoll gradient contained about 72% of the λ-glutamylcysteine synthetase activity in leaf cells and 48%
of the total glutathione synthetase activity. In chloroplasts ofSpinacia oleracea L. about 61% of the total λ-glutamylcysteine synthetase activity of the cells were found and 58% of the total glutathione
synthetase activity. These results indicate that glutathione synthesis can take place in at least two compartments of the
plant cell.
Dedicated to Professor A. Prison on the occasion of his 80th birthday 相似文献