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921.
Response to chilling of tomato mesophyll protoplasts 总被引:2,自引:0,他引:2
Freshly isolated protoplasts from tomato leaves show two completely different responses to a chilling treatment of 12 h at 7° C prior to culture at 29° C, depending on the presence or absence of glucose in the medium. In the culture medium with glucose as osmoticum, where the rate of cell divisions under optimal culture conditions is relatively high (about 20% plating efficiency), protoplasts were drastically injured by the chilling procedure and died. In the medium with mannitol as the osmoticum instead of glucose, where the plating efficiency even under optimal conditions is rather low (about 8%), protoplasts withstand the chilling procedure. More-over, after the chilling treatment when the protoplasts were transferred to the optimal culture temperature of 29° C, the plating efficiency was raised to about 20%, which is the same level as in the glucose-containing medium without chilling. This effect was not observed when the medium in which the protoplasts were suspended during the chilling period was replaced with fresh medium. This suggests that under these conditions tomato protoplasts produce and excrete a factor in the cold that improves the vitality of the cells or stimulates cell division. The possible relationship between chilling sensitivity of tomato protoplasts and their ability to divide will be discussed. 相似文献
922.
Roots regulate ion transport in the rhizosphere to counteract reduced mobility in dry soil 总被引:1,自引:0,他引:1
Diffusion of ions in the soil depends on soil moisture content. In a dry soil, transport of nutrients towards the root and the concomitant uptake could be reduced. However, pot and field experiments showed that this is not always the case. The objective of this paper was to investigate possible mechanisms of plants to counteract reduced nutrient supply due to water shortage. A split root system was used to investigate P and K inflow of oat and sugar beet at different soil moisture contents (Θ) without water shortage for the plant. The measured average P and K inflows were compared to model calculations considering diffusion, mass-flow, sorption and uptake processes. In the calculations, soil dryness impeded diffusion and decreased nutrient inflow as expected. Measured K inflow was decreased in a similar way indicating that Θ influences K diffusion. In contrast to this, measured P inflow was not influenced by Θ and under-estimated by the model. Low and high molecular exudates were collected at different water supply levels showing that exudation rate of both compounds was increased at water shortage. Especially the high molecular exudates (i.e. mainly mucilage) from water-stressed plants increased P concentration in soil solution under dry conditions in an incubation experiment. Calculated inflow considering this increased P concentration agreed well with measured P inflow indicating that exudation of mucilage could be a mechanism to overcome nutrient transport problems due to soil dryness. 相似文献
923.
Horst Kunz 《Journal of peptide science》2003,9(9):563-573
Based on structural information reported for the tumour-associated epithelial mucin MUC1, glycopeptides have been synthesized which contain tumour-associated saccharide antigens. such as the Thomsen-Friedenreich (T), TN or sialyl TN antigen. in combination with peptide sequences of the tandem repeat region of MUC1. Solid-phase syntheses have been carried out using N-Fmoc protected O-glycosyl serine and threonine building blocks and an allylic anchor which is stable to basic and acidic conditions, but can be cleaved under neutral conditions in a palladium(0)-catalysed allyl transfer reaction. In addition. a (2-3)sialyl T antigen threonine building block was prepared by a chemoenzymatic strategy and used in the synthesis of an N-terminal glycopeptide antigen of leukosialin (CD43). The proliferation of cytotoxic T cells could be induced using a construct consisting of a MUC1-glycopeptide antigen and a T cell epitope. 相似文献
924.
Dirk Weber Claudia Berger Timo Heinrich Peter Eickelmann Jochen Antel Horst Kessler 《Journal of peptide science》2002,8(8):461-475
The orphan receptor, human bombesin receptor subtype 3 (BRS-3) was assigned to the G-protein coupled bombesin receptor family because of its high sequence homology with the neuromedin B receptor (NMB-R) and gastrin-releasing peptide receptor (GRP-R). Since its pharmacology is stiIl unknown, new highly potent and selective tool-substances are needed, that may be able to elucidate its possible role in obesity and cancer. We have performed structure activity relationship studies on the high affinity peptide agonists [D-Phe6,beta-Ala11,Phe13,Nle14]Bn(6-14) and [D-Phe6,Phe13]Bn(6-13)propylamide, using their ability to mobilize intracellular calcium in BRS-3 transfected CHOGa-16 cells combined with receptor binding studies. It was demonstrated that for [D-Phe,beta-Ala11,Phe13,Nle14]Bn(6-14) the side chains of the residues Trp8 and Phe13, and to a smaller extent beta-Ala11, are the important amino acid side chains for receptor activation and binding, however for [D-Phe6,Phe13]Bn(6-13) propylamide His12 seems to be more important than Phe13. C-and N-terminal deletions and amino acid substitutions allowed further understanding. It was demonstrated that substitution of His 12 by Tyr leads to a high selectivity towards GRP-R. Using the acquired information, a small tetrapeptide library was designed with compounds presenting Trp and Phe at varying stereochemistry and distances, which led to the discovery of the lead-structure H-D-Phe-Gln-D-Trp-Phe-NH2. Systematic SAR revealed the important structural features of this peptide, C-terminal optimization resulted in the highly active and selective BRS-3 agonist H-D-Phe-Gln-D-Trp-1-(2-phenylethyl)amide. In summary, the size of the peptide was reduced from 8 or 9 amino acids to a tripeptide for BRS-3. 相似文献
925.
Biotransformation of Eugenol to Ferulic Acid by a Recombinant Strain of Ralstonia eutropha H16 下载免费PDF全文
The gene loci ehyAB, calA, and calB, encoding eugenol hydroxylase, coniferyl alcohol dehydrogenase, and coniferyl aldehyde dehydrogenase, respectively, which are involved in the first steps of eugenol catabolism in Pseudomonas sp. strain HR199, were amplified by PCR and combined to construct a catabolic gene cassette. This gene cassette was cloned in the newly designed broad-host-range vector pBBR1-JO2 (pBBR1-JO2ehyABcalAcalB) and transferred to Ralstonia eutropha H16. A recombinant strain of R. eutropha H16 harboring this plasmid expressed functionally active eugenol hydroxylase, coniferyl alcohol dehydrogenase, and coniferyl aldehyde dehydrogenase. Cells of R. eutropha H16(pBBR1-JO2ehyABcalAcalB) from the late-exponential growth phase were used as biocatalysts for the biotransformation of eugenol to ferulic acid. A maximum conversion rate of 2.9 mmol of eugenol per h per liter of culture was achieved with a yield of 93.8 mol% of ferulic acid from eugenol within 20 h, without further optimization. 相似文献
926.
Ink and Vinegar, a Simple Staining Technique for Arbuscular-Mycorrhizal Fungi 总被引:34,自引:0,他引:34 下载免费PDF全文
We developed a reliable, inexpensive, and simple method for staining arbuscular-mycorrhizal fungal colonizations in root tissues. Apart from applications in research, this nontoxic, high-quality staining method also could be of great utility in teaching exercises. After adequate clearing with KOH, an ink-vinegar solution successfully stained all fungal structures, rendering them clearly visible. 相似文献
927.
Purification and Characterization of the Coniferyl Aldehyde Dehydrogenase from Pseudomonas sp. Strain HR199 and Molecular Characterization of the Gene 总被引:2,自引:0,他引:2 下载免费PDF全文
Sandra Achterholt Horst Priefert Alexander Steinbüchel 《Journal of bacteriology》1998,180(17):4387-4391
The coniferyl aldehyde dehydrogenase (CALDH) of Pseudomonas sp. strain HR199 (DSM7063), which catalyzes the NAD+-dependent oxidation of coniferyl aldehyde to ferulic acid and which is induced during growth with eugenol as the carbon source, was purified and characterized. The native protein exhibited an apparent molecular mass of 86,000 ± 5,000 Da, and the subunit mass was 49.5 ± 2.5 kDa, indicating an α2 structure of the native enzyme. The optimal oxidation of coniferyl aldehyde to ferulic acid was obtained at a pH of 8.8 and a temperature of 26°C. The Km values for coniferyl aldehyde and NAD+ were about 7 to 12 μM and 334 μM, respectively. The enzyme also accepted other aromatic aldehydes as substrates, whereas aliphatic aldehydes were not accepted. The NH2-terminal amino acid sequence of CALDH was determined in order to clone the encoding gene (calB). The corresponding nucleotide sequence was localized on a 9.4-kbp EcoRI fragment (E94), which was subcloned from a Pseudomonas sp. strain HR199 genomic library in the cosmid pVK100. The partial sequencing of this fragment revealed an open reading frame of 1,446 bp encoding a protein with a relative molecular weight of 51,822. The deduced amino acid sequence, which is reported for the first time for a structural gene of a CALDH, exhibited up to 38.5% amino acid identity (60% similarity) to NAD+-dependent aldehyde dehydrogenases from different sources. 相似文献
928.
Adaptation of potassium translocation into the shoot of maize (Zea mays) to shoot demand: Evidence for xylem loading as a regulating step 总被引:1,自引:0,他引:1
In order to manipulate the shoot demand for mineral nutrients per unit root weight, maize ( Zea mays L.) seedlings were grown in nutrient solution with different temperatures in the root zone and at the shoot base. The aerial temperature was kept uniform at 24/20°C day/night. At a root zone temperature (RZT) of 24°C, shoot growth was reduced by decreasing the shoot base temperature (SBT) to 12°C; at a RZT of 12°C, shoot growth was increased by raising the SBT to 24°C. At both RZT root growth was not affected by the SBT. Thus, the shoot demand for nutrients per unit root was either increased by raising, or decreased by lowering the SBT. The net uptake rate of potassium (K), as determined from accumulation rates between sequential harvests, was not affected within the first 3 days after lowering the SBT, whereas net translocation rates of K into the shoot and translocation rates in the xylem exudate of decapitated plants were markedly reduced. Obviously, translocation of K into the shoot seems to be regulated independently from K uptake into the root cells. Translocation rates of K in the xylem exudate of decapitated plants were markedly reduced when the nutrient solution was replaced by CaCl2 solution during exudation. But, depending on the SBT before decapitation, significant differences remained in the translocation rates of K even when K uptake from the nutrient solution was prevented.
From the results it is suggested that xylem loading of K is regulated separately from K uptake from the external solution and that the adaptation of K translocation to shoot demand is coupled with an altered capacity of the root for xylem loading. 相似文献
From the results it is suggested that xylem loading of K is regulated separately from K uptake from the external solution and that the adaptation of K translocation to shoot demand is coupled with an altered capacity of the root for xylem loading. 相似文献
929.
Inge Kalsner Franz-Josef Schneider Rudolf Geyer Horst Ahorn Ingrid Maurer-Fogy 《Glycoconjugate journal》1992,9(4):209-216
Recombinant human soluble low affinity receptor for the Fc portion of IgE (sFcRII/sCD23) was produced inSaccharomyces cerevisiae or Chinese hamster ovary cells and subjected to carbohydrate analysis. Applied methods included analytical SDS-PAGE, reversed phase HPLC, methylation analysis and sequential degradation with exoglycosidases. The results revealed that sFcRII derived from Chinese hamster ovary cells is glycosylated exclusively at Ser-147, containing mainly the trisaccharide Sia(2–3)Gal(1–3)GalNAc, whereas the yeast derived glycoprotein was glycosylated at Ser-167 and contained only -mannosyl residues. It is shown here for the first time that different amino acids of a given protein can be O-glycosylated when expressed in yeast or Chinese hamster ovary cells. 相似文献
930.
John de Souza Horst Hertel Dora Fix Ventura Randolf Menzel 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,170(3):267-274
1. | Monopolar cells of the first visual ganglion, the lamina, of the bee were recorded from and stained intracellularly. |
2. | Several different response types to pulses of spectral light were found. The most common response type hyperpolarized in a phasic-tonic fashion. The tonic hyperpolarizing response frequently decreased gradually, but in some cases increased with lasting illumination. Some cells also gave a transient response to light-OFF. In contrast, one stained and several unstained cells showed depolarizing responses. Five cells exhibited spiking responses under normal physiological conditions. |
3. | The V/log I-functions were steeper than those of the photoreceptors and, in some cases, had both rising and falling parts with increasing intensities. The spectral sensitivity obtained with the constant response method showed a peak in the green (510–535 nm) in most cells. A series of spectral flashes revealed an additional type with highest sensitivity in UV. Indirect evidence was found in one cell for spectral opponent processing. |
4. | Two morphological types of monopolar cells were stained. These correspond well to Ribi's (1976) L1 and L2 cells, with some differences in detail. The most frequently stained cell type closely resembles his L2 type. All 3 stained spiking cells were of this type. |