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91.
Insect resistance of transgenic plants that express modified Bacillus thuringiensis cryIA(b) and cryIC genes: a resistance management strategy 总被引:7,自引:0,他引:7
92.
93.
The carotenoid composition of 33 species of green algal lichens and 5 species of blue-green algal lichens was examined and
compared with that of the leaves of higher plants. As in higher plants, green algal lichen species which were found in both
shade and full sunlight exhibited higher levels of the carotenoids involved in photoprotective thermal energy dissipation
(zeaxanthin as well as the total xanthophyll cycle pool) in the sun than in the shade. This was particularly true when thalli
were moist during exposure to high light, or presumably became desiccated in full sunlight. However, the reverse trend in
the carotenoid composition of green algal lichens was also observed in those species which were found predominantly either
in the shade or in full sunlight. In this case sun-exposed lichens often possessed lower levels of zeaxanthin and of the components
of the xanthophyll cycle than lichens which were found in the shade. In contrast to higher plants, the lichens from all habitats
exhibited a relatively high ratio of carotenoids to chlorophylls (more characteristic of sun leaves), very low levels of α-carotene
(similar to that found in sun leaves), and a level of β-carotene similar to that found in shade leaves. Zeaxanthin, but not
the expoxides of the xanthophyll cycle, was also frequently found in blue-green algal lichens. A trend for increasing levels
of zeaxanthin with increasing growth light regime was observed inPeltigera rufescens, the species which was found to occur over the widest range of light environments. The level of zeaxanthin per chlorophylla in these blue-green algal lichens was in a range similar to that per chlorophylla+b in green algal lichens. However, zeaxanthin was also absent in one species,Collema cristatum, in full sunlight. Thus, the zeaxanthin content of the blue-green algal lichens can be similar to that of higher plants,
or it can be rather dissimilar, as was also the case in the green algal lichen species. The presence of large amounts of ketocarotenoids
in blue-green algal lichens is also noteworthy. 相似文献
94.
CO2 exchange rate in relation to thallus water content (WC, % of dry weight) was determined for 22 species of lichens, mainly members of the genera Pseudocyphellaria and Sticta, from a temperate rainforest, Urewere National Park, New Zealand. All data were obtained in the field, either using a standard technique in which the lichens were initially wetted (soaked or sprayed, then shaken) and allowed to slowly dry, or from periodic measurements on samples that were continuously exposed in their natural habitat. A wide range of WC was found, with species varying from 357 to 3360% for maximal WC in the field, and from 86 to 1300% for optimal WC for photosynthesis. Maximal WC for lichens, wetted by the standard technique, were almost always much less than the field maxima, due to the presence of water on the thalli. The relationships between CO2 exchange rate and WC could be divided into four response types based on the presence, and degree, of depression of photosynthesis at high WC. Type A lichens showed no depression, and Type B only a little at maximal WC. Type C had a very large depression and, at the highest WC, CO2 release could occur even in the light. Photosynthetic depression commenced soon after optimal WC was reached. Type D lichens showed a similar depression but the response curve had an inflection so that net photosynthesis was low but almost constant, and never negative, at higher WC. There was little apparent relationship between lichen genus or photobiont type and the response type. It was shown that high WC does limit photosynthetic CO2 uptake under natural conditions. Lichens, taken directly from the field and allowed to dry under controlled conditions, had net photosynthesis rates that were initially strongly inhibited but rose to an optimum, before declining at low WC. The limiting effects of high WC were clearly shown when, under similar light conditions, severe photosynthetic depression followed a brief, midday, rain storm. Over the whole measuring period the lichens were rarely at their optimal WC for photosynthesis, being mostly too wet or, occasionally, too dry. Photosynthetic performance by the lichens exposed in the field was similar to that expected from the relationship between the photosynthetic rate and WC established by the standard procedure. 相似文献
95.
96.
K Lange 《American journal of human genetics》1993,52(2):305-311
The calculation of match probabilities is the most contentious issue dividing prosecution and defense experts in the forensic applications of DNA fingerprinting. In particular, defense experts question the applicability of the population genetic laws of Hardy-Weinberg and linkage equilibrium to racially admixed American populations. Linkage equilibrium justifies the product rule for computing match probabilities across loci. The present paper suggests a method of bounding match probabilities that depends on modeling gene descent from ancestral populations to contemporary populations under the assumptions of Hardy-Weinberg and linkage equilibrium only in the ancestral populations. Although these bounds are conservative from the defendant's perspective, they should be small enough in practice to satisfy prosecutors. 相似文献
97.
The anion channel protein from Clavibacter michiganense ssp. nebraskense (Schürholz, Th. et al. 1991, J. Membrane Biol. 123: 1-8) was analyzed at different concentrations of KCl and KF. At 0.8 M KCl the conductance G(Vm) increases exponentially from 21 pS at 50 mV up to 53 pS at Vm = 200 mV, 20°C. The concentration dependence of G(Vm) corresponds to a Michaelis-Menten type saturation function at all membrane voltage values applied (0-200 mV). The anion concentration K0.5, where G(Vm) has its half-maximum value, increases from 0.12 M at 50 mV to 0.24 M at 175 mV for channels in a soybean phospholipid bilayer. The voltage dependence of the single channel conductance, which is different for charged and neutral lipid bilayers, can be described either by a two-state flicker (2SF) model and the Nernst-Planck continuum theory, or by a two barrier, one-site (2B1S) model with asymmetric barriers. The increase in the number of open channels after a voltage jump from 50 mV to 150 mV has a time constant of 0.8 s. The changes of the single-channel conductance are much faster (<1 ms). The electric part of the gating process is characterized by the (reversible) molar electrical work ΔGθel = ρZgFVm ≈ -1.3 RT, which corresponds to the movement of one charge of the gating charge number |Zg| = 1 across the fraction ρ = ΔVm/Vm = 0.15 of the membrane voltage Vm = 200 mV. Unlike with chloride, the single channel conductance of fluoride has a maximum at about 150 mV in the presence of the buffer PIPES (≥5 mM, pH 6.8) with K0.5 ≈ 1 M. It is shown that the decrease in conductance is due to a blocking of the channel by the PIPES anion. In summary, the results indicate that the anion transport by the Clavibacter anion channel (CAC) does not require a voltage dependent conformation change of the CAC. 相似文献
98.
Gibberellin (GA) biosynthesis in cell-free systems from Cucurbita maxima L. endosperm was reinvestigated using incubation conditions different from those employed in previous work. The metabolism of GA12 yielded GA13, GA43 and 12α-hydroxyGA43 as major products, GA4, GA37, GA39, GA46 and four unidentified compounds as minor products. The intermediates GA15, GA24 and GA25 accumulated at low protein concentrations. The structure of the previously uncharacterised 12α-hydroxyGA43 was inferred from its mass spectrum and by its formation from both GA39 and GA43. Gibberellin A39 and 12α-hydroxyGA43 were formed by a soluble 12α-hydroxylase that had not been detected before. Gibberellin A12-aldehyde was metabolised to essentially the same products as GA12 but with less efficiency. A new 13-hydroxylation pathway was found. Gibberellin A53, formed from GA12 by a microsomal oxidase, was converted by soluble 2-oxoglutarate-dependent oxidases to GA1 GA23, GA28, GA44, and putative 2β-hydroxyGA28. Minor products were GA19, GA20, GA38 and three unidentified GAs. Microsomal 13-hydroxylation (the formation of GA53) was suppressed by the cofactors for 2-oxoglutarate-dependent enzymes. Reinvestigation of the endogenous GAs confirmed the significance of the new metabolic products. In addition to the endogenous GAs reported by Blechschmidt et al. (1984, Phytochemistry 23, 553–558), GA1, GA8, GA25, GA28, GA36, GA48 and 12α-hydroxyGA43 were identified by full-scan capillary gas chromatography-mass spectrometry and Kovats retention indices. Thus both the 12α-hydroxylation and the 13-hydroxylation pathways found in the cell-free system operate also in vivo, giving rise to 12α-hydroxyGA43 and GA1 (or GA8), respectively, as their end products. Evidence for endogenous GA20 and GA24 was also obtained but it was less conclusive due to interference. 相似文献
99.
Ellen A. Meijer Sacco C. de Vries Peter Sterk Dorus W. J. Gadella Jr. Karel W. A. Wirtz Theo Hendriks 《Molecular and cellular biochemistry》1993,123(1-2):159-166
The extracellular protein EP2 was previously identified as non-specific lipid transfer protein based on its cDNA-derived amino acid sequence. Here, the purification of the EP2 protein from the medium of somatic embryo cultures is described. After two cycles of ion-exchange and gel permeation chromatography, a single silver-stained protein band with an apparent molecular mass of 10 kDa was observed on SDS-PAGE. This protein band was recognized by the antiserum raised against a EP2--galactosidase fusion-protein. Employing a fluorescent phospholipid analog, it was shown that the purified EP2 protein is capable of binding phospholipids and is able to enhance their transfer between artificial membranes. Employing a gel permeation assay, it could be demonstrated that the EP2 protein is also capable of binding palmitic and oleic acid as well as oleyl-CoA. Because in plants these fatty acids are used as precursor molecules for cutin, these results are in support of the proposed role of the EP2 protein to transport cutin monomers from their site of synthesis through the cell wall of epidermal cells to sites of cutin polymerization. 相似文献
100.
Marc J. E. C. van der Maarel Peter Quist Lubbert Dijkhuizen Theo A. Hansen 《Archives of microbiology》1993,160(5):411-412
Dimethylsulfoniopropionate, an osmolyte of marine algae, is thought to be the major precursor of dimethyl sulfide, which plays a dominant role in biogenic sulfur emission. The marine sulfate-reducing bacterium Desulfobacterium strain PM4 was found to degrade dimethylsulfoniopropionate to 3-S-methylmercaptopropionate. The oxidation of one of the methyl groups of dimethylsulfoniopropionate was coupled to the reduction of sulfate; this process is similar to the degradation betaine to dimethylglycine which was described earlier for the same strain. Desulfobacterium PM4 is the first example of an anaerobic marine bacterium that is able to demethylate dimethylsulfoniopropionate.Abbreviations DMSP
dimethylsulfoniopropionate
- DMS
dimethyl sulfide
- MMPA
3-S-methylmercaptopropionate 相似文献