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941.
Summary A 3D NMR technique is described which correlates the amide proton and nitrogen resonances of an amino acid residue with the C chemical shift of its preceding residue. The technique uses a relay mechanism, transferring magnetization from15N to13C via the intervening carbonyl nucleus. This method for obtaining sequential connectivity is less sensitive to large line widths than the alternative HNCA experiment. The technique is demonstrated for the protein calmodulin, complexed with a 26 amino acid fragment of skeletal muscle myosin light chain kinase.Abbreviations CaM
Calmodulin
- HCACO
-proton to -carbon to carbonyl correlation
- H(CA)NHN
-proton (via -carbon) to nitrogen to amide proton correlation
- HMQC
heteronuclear multiple quantum correlation
- HNCA
amide proton to nitrogen to C -carbon correlation
- M13
a 26-residue fragment of the CaM-binding domain of skeletal muscle myosin light chain kinase comprising residues 577–602. 相似文献
942.
Valeria Castelletto Ian W. Hamley Teck Lim Matias B. De Tullio Eduardo M. Castaño 《Journal of peptide science》2010,16(9):443-450
We study the complex formation of a peptide βAβAKLVFF, previously developed by our group, with Aβ(1–42) in aqueous solution. Circular dichroism spectroscopy is used to probe the interactions between βAβAKLVFF and Aβ(1–42), and to study the secondary structure of the species in solution. Thioflavin T fluorescence spectroscopy shows that the population of fibers is higher in βAβAKLVFF/Aβ(1–42) mixtures compared to pure Aβ(1–42) solutions. TEM and cryo‐TEM demonstrate that co‐incubation of βAβAKLVFF with Aβ(1–42) causes the formation of extended dense networks of branched fibrils, very different from the straight fibrils observed for Aβ(1–42) alone. Neurotoxicity assays show that although βAβAKLVFF alters the fibrillization of Aβ(1–42), it does not decrease the neurotoxicity, which suggests that toxic oligomeric Aβ(1–42) species are still present in the βAβAKLVFF/Aβ(1–42) mixtures. Our results show that our designed peptide binds to Aβ(1–42) and changes the amyloid fibril morphology. This is shown to not necessarily translate into reduced toxicity. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd. 相似文献
943.
Eunice Areal Bacelar José M. Moutinho-Pereira Berta C. Gon?alves Jo?o I. Lopes Carlos M. Correia 《Acta Physiologiae Plantarum》2009,31(3):611-621
Gas exchange rates, chlorophyll fluorescence, pressure–volume relationships, photosynthetic pigments, total soluble sugars,
starch, soluble proteins and proline concentrations were investigated in five Olea europaea L. cultivars with different geographical origins (Arbequina, Blanqueta, Cobran?osa, Manzanilla and Negrinha) grown under
Mediterranean field conditions. We found considerable genotypic differences among the cultivars. Comparing the diurnal gas
exchange rates, we observed that Cobran?osa, Manzanilla and Negrinha had high photosynthetic rate than Arbequina and Blanqueta.
The first group reveals to be better acclimated to drought conditions, and appears to employ a prodigal water-use strategy,
whereas Blanqueta and Arbequina, with high water-use efficiency, appear to employ a conservative water-use strategy. The degree
of midday depression in photosynthesis was genotype dependent, with a maximum in Arbequina and a minimum in Negrinha. The
reductions in the photosynthetic rate were dependent from both stomatal and non-stomatal limitations. Elastic adjustment plays an important role as drought tolerance mechanism. The group of cultivars that employ a prodigal
water-use strategy revealed high tissue elasticity, whereas Arbequina and Blanqueta revealed high tissue rigidity. We also
identified the existence of drought tolerance mechanisms associated with soluble proteins accumulation in the foliage. The
high levels of soluble proteins in Arbequina may represent an increased activity of oxidative stress defence enzymes and may
also represent a reserve for post stress recovery. In all cultivars, especially in Manzanilla, free proline was accumulated
in the foliage. The discussed aspects of drought stress metabolism may have an adaptative meaning, supporting the hypothesis
that olive cultivars native to dry regions, such as Cobran?osa, Manzanilla and Negrinha, have more capability to acclimate
to drought conditions than cultivars originated in regions with a more temperate climate, like Arbequina and Blanqueta. 相似文献
944.
Citric acid yields of 98.7% (sugar consumption basis) were reached in shaker flasks with mutant UV-ET-71-15 of Aspergillus niger in a resin-treated sucrose medium of the following composition (g/100 ml): sucrose, 14.0; NH(4)NO(3), 0.20; KH(2)PO(4), 0.10; MgSO(4).7H(2)O, 0.025; and (mg/liter): FeSO(4), 0.15 to 0.75; ZnSO(4), 0.10; and CuSO(4), 0.01. Yields of 75% were obtained in medium with resin-treated clarified syrup and 68% with ferrocyanide-treated blackstrap molasses. Optimal conditions included selection of appropriate pellets as inoculum at 3%, pH of 4.5, temperature at 30 C, agitation at 250 rev/min, and fermentation time of 8 days. The mutant tolerated high concentrations of trace elements. 相似文献
945.
Elizabeta Pertot Damjana Rozman Stjepan Miličić Helena Sočič 《Applied microbiology and biotechnology》1988,28(2):209-213
Summary The morphological development ofClaviceps paspali immobilized in Ca-alginate gel was examined. During consecutive reincubations, the immobilized mycelia differentiated into swollen, arthrosporoid-like cells, which never appeared during fermentation of free mycelium. Such differentiation could be connected with the improved, prologed vitality and metabolic activity of the immobilized cells. 相似文献
946.
Chromium is an essential trace element and is associated with some biological pathways, especially with glucose tolerance.
For these reasons, we decided to determine the concentration of chromium in two sets of Brazilian medicinal plants. The first
group consisted of plants that are considered as antidiabetic, whereas the second included plants that do not have this therapeutic
property. The concentration of chromium was determined by flameless atomic absorption. All the plants analyzed contain chromium
in the normal range for this element, but the hypoglycemic plants contain more chromium than the others (1–4 μg/g compared
to 0.5–1.5 μg/g). 相似文献
947.
Jayr de Paiva Campello Sebastião Ferreira Fonseca Ching-Jer Chang Ernest Wenkert 《Phytochemistry》1975,14(1):243-248
Sitosterol and the following terpenic compounds have been isolated from the bark of Podocarpus lambertius: 3β-hydroxytotarol, 4β-carboxynortotarol, and macrophyllic and lambertic acids. The leaves yielded sitosterol, stigmastan-3β,5α-diol-6-one, isopimaric acid, phyllocladene, isophyllocladene, 8,9-abieten-15-ol and 17-isophyllocladenol. 相似文献
948.
Peconick AP Sossai S Girão FA Rodrigues MQ Souza E Silva CH Guzman Q F Patarroyo V AM Vargas MI Patarroyo JH 《Experimental parasitology》2008,119(1):37-43
The synthetic vaccine SBm7462 is based on three immunogenic epitopes (4822, 4823 and 4824) contained within protein Bm86 derived from the Australian Yeerongpilly strain of the tick Rhipicephalus (Boophilus) microplus. Twenty strains of the tick originating from Brazil, Argentina, Colombia and Uruguay were analysed in order to identify differences compared with sequences present in components of vaccine SBm7462. For each parasite population, three cDNA fragments containing the nucleotides coding for the epitopes 4822, 4824 and 4823 were sequenced, and the amino acid sequences were deduced and compared with those of the homologous bm86 gene. The results indicate that the epitope sequences of vaccine SBm7462 are conserved in the South American populations of the tick. The conservation of such sequences is very important for the immunological response of different populations of R. (B.) microplus. 相似文献
949.
Molecular characterization of a fourth isoform of the catalytic subunit of protein phosphatase 2A from Arabidopsis thaliana 总被引:1,自引:0,他引:1
Antonio Casamayor Encarna Pérez-Callejón Gemma Pujol Joaquín Ariño Albert Ferrer 《Plant molecular biology》1994,26(1):523-528
We have recently reported the existence of multiple isoforms of the catalytic subunit of protein phosphatase 2A (PP2A) in Arabidopsis thaliana and the molecular cloning of cDNAs encoding three of these proteins (PP2A-1, PP2A-2, PP2A-3). The reported cDNA encoding PP2A-3 was truncated at the 5 terminus, lacking a short fragment of the N-terminal coding sequence. We have now isolated a near full-length cDNA encoding the entire PP2A-3 protein (313 residues). The clone includes 188 nucleotides of 5-untranslated region, where a 44 bp long poly(GA) track is found. We also describe the cloning of a cDNA encoding a fourth isoform of PP2A (PP2A-4). The polypeptide contains 313 residues being 98% identical to PP2A-3 and only 80% identical to both PP2A-1 and PP2A-2. The mRNA for PP2A-4 is 1.4 kb in length and, although predominantly expressed in roots, it is also found in other organs. It is concluded that in A. thaliana the isoforms of PP2A can be grouped in two extremely conserved subfamilies. 相似文献
950.
A procedure is presented for refinement of a homology model of E. coli tRNAVal, originally based on the X-ray structure of yeast tRNAPhe, using experimental residual dipolar coupling (RDC) and small angle X-ray scattering (SAXS) data. A spherical sampling algorithm
is described for refinement against SAXS data that does not require a globbic approximation, which is particularly important
for nucleic acids where such approximations are less appropriate. Substantially higher speed of the algorithm also makes its
application favorable for proteins. In addition to the SAXS data, the structure refinement employed a sparse set of NMR data
consisting of 24 imino N–HN RDCs measured with Pf1 phage alignment, and 20 imino N–HN RDCs obtained from magnetic field dependent alignment of tRNAVal. The refinement strategy aims to largely retain the local geometry of the 58% identical tRNAPhe by ensuring that the atomic coordinates for short, overlapping segments of the ribose-phosphate backbone and the conserved
base pairs remain close to those of the starting model. Local coordinate restraints are enforced using the non-crystallographic
symmetry (NCS) term in the XPLOR-NIH or CNS software package, while still permitting modest movements of adjacent segments.
The RDCs mainly drive the relative orientation of the helical arms, whereas the SAXS restraints ensure an overall molecular
shape compatible with experimental scattering data. The resulting structure exhibits good cross-validation statistics (jack-knifed
Q
free = 14% for the Pf1 RDCs, compared to 25% for the starting model) and exhibits a larger angle between the two helical arms
than observed in the X-ray structure of tRNAPhe, in agreement with previous NMR-based tRNAVal models.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献