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111.
Ceulemans R.; Taylor G.; Bosac C.; Wilkins D.; Besford R.T. 《Journal of experimental botany》1997,48(9):1681-1689
The effects of elevated CO2 were studied on the photosyntheticgas exchange behaviour and leaf physiology of two contrastingpoplar (Populus) hybrids grown and treated in open top chambers(OTCs in Antwerp, Belgium) and in closed glasshouse cabinets(GHCs in Sussex, UK). The CO2 concentrations used in the OTCswere ambient and ambient +350 µmol mol1 while inthe GHCs they were c. 360 µmol mol1 versus 719µmol mol1. Measurements of photosynthetic gas exchangewere made for euramerican and interamerican poplar hybrids incombination with measurements of dark respiration rate and Rubiscoactivity. Significant differences in the leaf anatomy and structure(leaf mass per area and chlorophyll content) were observed betweenthe leaves grown in the OTCs and those grown in the GHCs. ElevatedCO2 stimulated net photosynthesis in the poplar hybrids after1 month in the GHCs and after 4 months in the OTCs, and therewas no evidence of downward acclimation (or down-regulation)of photosynthesis when the plants in the two treatments weremeasured in their growth CO2 concentration. There was also noevidence of down-regulation of Rubisco activity and there wereeven examples of increases in Rubisco activity. Rubisco exerteda strong control over the light-saturated rate of photosynthesis,which was demonstrated by the close agreement between observednet photosynthetic rates and those that were predicted fromRubisco activities and Michaelis-Menten kinetics. After 17 monthsin elevated CO2 in the OTCs there was a significant loss ofRubisco activity for one of the hybrid clones, i.e. Beaupr,but not for clone Robusta. The effect of the CO2 measurementconcentration (i.e. the short-term treatment effect) on netphotosynthesis was always larger than the effect of the growthconcentration in both the OTCs or GHCs (i.e. the longterm growthCO2 effect), with one exception. For the interamerican hybridBeaupr dark respiration rates in the OTCs were not significantlyaffected by the elevated CO2 concentrations. The results suggestthat for rapidly growing tree species, such as poplars, thereis little evidence for downward acclimation of photosynthesiswhen plants are exposed to elevated CO2 for up to 4 months;longer term exposure reveals loss of Rubisco activity. Key words: Elevated CO2, Populus, Rubisco, photosynthesis, chlorophyll content 相似文献
112.
Witold Lasek Anna Wańkowicz Katarzyna Kuc Wojciech Feleszko Jakub Golab Adam Giermasz Wiesŀaw Wiktor-J/cedrzejczak Marek Jakóbisiak 《Cancer immunology, immunotherapy : CII》1995,40(5):315-321
The efficacy of systemic infusion of recombinant human macrophage-colony-stimulating factor (M-CSF) in combination with local treatment with human recombinant tumor necrosis factor (TNF) and mouse recombinant interferon (IFN) was studied in vivo on a subclone of B16 melanoma (MmB16) in mice. Short-term intravenous administration of M-CSF at a dose of 106 units daily had no antitumor effect in vivo. Similarly, local treatment of tumor with TNF (5 g daily) did not produce any therapeutic effect. However, simultaneous administration of the same dose of TNF with IFN (1000 units daily) resulted in a synergistic effects manifested by the retardation of tumor growth. Addition of systemic infusion of M-CSF to the local therapy with TNF and IFN induced further augmentation of antitumor efficacy and delayed progression of MmB16 melanoma. The strengthened antitumor effect of combination therapy including M-CSF, TNF and IFN was most probably due to the increased release of monocytes from the bone marrow, their recruitment into the site of tumor growth and subsequent local stimulation of their antitumor activity. 相似文献
113.
114.
Gracjana Klein Robert Walczak Ewa Krasnowska Adam Blaszczak Barbara Lipiska 《Molecular microbiology》1995,16(4):801-811
We have investigated heat-shock response in a marine bacterium Vibrio harveyi. We have found that 39 C was the highest tempature at which V. harveyi was able to grow steadily. A shift from 30° C to 39° C caused increased synthesis of at least 10 proteins, as judged by SDS-PAGE, with molecular masses of 90, 70, 58, 41, 31, 27, 22, 15, 14.5 and 14kDa. The 70, 58, 41 and 14.5 kDa proteins were immunologically homologous to DnaK, GroEL, DnaJ and GroES heat-shock proteins of Escherichia coli, respectively. V. harveyi GroES protein had a lower molecular mass (14.5 kDa) than E. coli GroES, migrating in SDS-PAGE as 15 kDa protein. We showed that a protein of ~43 kDa, immunologically reactive with antiserum against E. coli sigma 32 subunit (σ32) of RNA polymerase, was induced by heat-shock and co-purified with V. harveyi RNA polymerase. These results suggest that the 43 kDa protein is a heat-shock sigma protein of V. harveyi. Preparation containing the V. harveyi sigma 32 homologue, supplemented with core RNA polymerase of E. coli, was able to transcribe heat-shock promoters of E. coli in vitro. 相似文献
115.
116.
Damage to DNA by bleomycin in vitro is entirely dependent on the presence of an iron salt and molecular oxygen. This same reaction has been used to measure non-protein-bound iron in different bacterial species. Although several of the species examined were insensitive to the toxic effects of bleomycin, they all contained a concentration of non-protein-bound iron which should have been sufficient to allow iron-dependent damage to DNA. Other factors such as permeability or inactivation of the drug must explain their apparent insensitivity. 相似文献
117.
118.
Cross-correlation histograms (CCH) were computed for discharge sequences of pairs of motoneurones which were excited by sinusoidal muscle stretches. These CCH's were compared before and after opening of the recurrent inhibitory loop by Renshaw cell blocking agents. Periodic patterns in the CCH's indicative of specifically timed phase relations between discharges of different motoneurones were enhanced after Renshaw cell blockage. This was confirmed by power spectra computed for the CCH's. They contained power peaks about 50Hz which tended to increase after depression of recurrent inhibition. The correlation was thus due predominantly to line current interference which seemed to act as a common entrainment input at the spinal level. It is concluded that Renshaw cells de-correlate discharge patterns of different motoneurones of the same pool by injecting uncorrelated signals into them. This de-correlation is an important prerequisite for distortion suppression of signal transmission in a multi-channel system, like that of stretch reflex, and for its linearization. 相似文献
119.
An incubator designed for use inside an anaerobic glove box is described. The incubator is made of transparent plastic material, has sliding plastic doors, and can be made in various sizes from readily available materials. 相似文献
120.
In order to determine the significance of the C-6 carboxyl group for the biological activity gibberellin A3, 6-epigibberellin A3, 7-norgibberellin A3, 6-methyl-7-norgibberellin A3, and 7-homogibberellin A3 were studied using dwarf pea, dwarf maize, dwarf rice, dwarf barley and -amylase bioassays. All gibberellin A3(GA3)derivatives tested were considerably less active than GA3. In all biossays, 6-epi-GA3 showed a low activity of the same order, whereas 6-methyl-7-nor-GA3 was inactive. Surprisingly, 7-nor-GA3 had some activity in the dwarf rice (root application), dwarf barley, and -amylase bioassay, in contrary to its low potency in the dwarf pea, dwarf maize, and dwarf rice (micro drop) bioassay. 7-Homo-GA3 was primarily active in the dwarf maize, dwarf barley and dwarf rice bioassay. It also caused antigibberellin effects in dwarf rice. The results demonstrate that the C-6 carboxyl group is not absolutely essential for biological activity of gibberellins. The different activities of 7-nor-GA3 observed in the various test systems may indicate that the C-6 carboxyl group is a structural requirement more for uptake and/or transport processes than for receptor affinity.Abbreviation GA3
gibberellic acid 相似文献