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41.
The interaction of jatrophone with sRNA from Escherichia coli has been investigated through UV, CD, and 1H NMR measurements. The results obtained show that the interaction with jatrophone increases the stability of the polynucleotide. It appears that the optical properties of jatrophone depend upon the jatrophone/nucleotide ratio. The observed behaviour can only be explained by the existence of different types of interaction between jatrophone and sRNA. Even for a jatrophone/nucleotide ratio as low as 0.17 the 1H NMR spectra show a multiplicity of resonances that can only be explained by the simultaneous existence of two different binding modes involving the jatrophone molecules. 相似文献
42.
C. Steven McDaniel Taghi Manshouri M. Zouhair Atassi 《Journal of Protein Chemistry》1987,6(5):455-461
A peptide corresponding to residues 26–41 of α-bungarotoxin, and closed by a disulfide bond between two cysteine residues
at the amino and C terminal ends of the peptide, was synthesized and the monomeric form was purified. The peptide, which represents
the exposed part of the long central loop of the toxin molecule, was examined for binding to acetylcholine receptor. The peptide
was shown by radiometric titrations to bind radiolabeled receptor, and radiolabeled peptide was bound by receptor. The specificity
of the binding was confirmed by inhibition with the parent toxin. A synthetic analog of the peptide in which Trp-28 was replaced
by glycine had very little (10%) of the original activity. Succinylation of the amino groups of the peptide resulted in virtually
complete (98%) loss of the binding activity. These results indicate that a shortened loop peptide corresponding to the region
26–41 of α-bungarotoxin exhibits binding activities mimicking those of the parent molecule. In this region, Trp-28, and one
or both of Lys-26 and Lys-38, are essential contact residues in the binding to receptor. 相似文献
43.
Substrate particle size affects pit building decision and pit size in the antlion larvae Euroleon nostras (Neuroptera: Myrmeleontidae) 总被引:2,自引:0,他引:2
Abstract. The larvae of the antlion Euroleon nostras are pit-builders, constructing pitfall traps in loose sand. The number of pits and the pit diameter are recorded when larvae are kept in substrates with different particle sizes. The most convenient pit-building sand fractions are two fractions with fine sand (≤ 0.23 mm; 0.23–0.54 mm). The largest pits are constructed in sand with a particle size of 0.23–0.54 mm. In this sand fraction, larvae of all three instars most readily build pits. No pits are constructed in sand with a particle size greater than 1.54 mm. First- and second-instar larvae avoid building pits in substrates of particle size 1–1.54 mm, but third-instar larvae construct pits in this sand fraction. It is assumed that the antlion is capable of distinguishing between substrate types and this hypothesis is tested by giving larvae the choice of building a pit in one of four particle-size fractions. Larvae of all three instars prefer to build pits in the fraction with a particle size of 0.23–0.54 mm. Only third-instar larvae build pits in all four fractions, but only occasionally in the coarser fraction. 相似文献
44.
A. De Marco A. M. Petros R. A. Laursen M. Llinás 《European biophysics journal : EBJ》1987,14(6):359-368
The interaction of the isolated human plasminogen kringle 4 with the four -amino acid ligands -aminocaproic acid (ACA), N-acetyl-l-lysine (AcLys), trans-aminomethyl(cyclohexane)carboxylic acid (AMCHA) and p-benzylaminesulfonic acid (BASA) has been further characterized by 1H-NMR spectroscopy at 300 and 600 MHz. Pronounced high-field shifts, reaching 3 ppm, are observed for AMCHA resonances upon binding to kringle 4, which underscores the relevance of ligand lipophilic interactions with aromatic side chains at the binding site. Ligand titration curves for the nine His and Trp singlets found in the kringle 4 aromatic spectrum reveal a striking uniformity in the kringle response to the various ligands. The average binding curves exhibit a clear Langmuir absorption isotherm saturation profile and the data were analyzed under the assumption of one (high affinity) binding site per kringle. Equilibrium association constants (K
a
) and first order dissociation rate constants (k
off) were derived from linearized expressions of the Langmuir isotherm and of the spectral line-shapes, respectively. The results for the four ligands, at 295 K, pH* 7.2, indicate that: (a) AMCHA exhibits the strongest binding (K
a
=159 mM
-1) and ACA the weakest (K
a
=21 mM
–1) with AcLys and BASA falling in between; (b) ACA dissociates readily (k
off = 5.3 × 103 s–1) and AMCHA associates the fastest (k
off = 2.0 × 108
M
–1 s–1) while the kinetics for BASA exchange is relatively slow (k
off = 0.8 × 103 s–1, k
on = 0.6 × 108
M
–1s–1); (c) the ligand-binding kinetics is close to diffussion-controlled.Abbreviations ACA
-aminocaproic acid
- AcLys
N-acetyl-l-lysine
- AMCHA
t-aminomethyl(cyclohexane)carboxylic acid
- BASA
p-benzylaminesulfonic acid
- K4
kringle 4
- NOE
nuclear Overhauser effect
- ppm
parts-per-million
- pH*
glass electrode pH reading uncorrected for deuterium isotope effects
-
K
a
ligand-kringle 4 equilibrium association constant
-
k
off
ligand-kringle 4 dissociation rate constant
-
k
on
ligand-kringle 4 association rate constant 相似文献
45.
Blue bacteriorhodopsin was prepared by electrodialysis, cation-exchange chromatography and acidification. The electrooptical properties of these preparations compared to those of the native purple bacteriorhodopsin suggest that the blue bacteriorhodopsin has a smaller induced dipole moment than the native purple bacteriorhodopsin and that bound cations in the native bacteriorhodopsin stabilize the protein conformation in the membrane.Purple bacteriorhodopsin was regenerated by addition of potassium, magnesium or ferric ions to blue bacteriorhodopsin. Both spectrscopically and electrooptically the potassium- and ferric-regenerated samples are different from the native purple state. Although the magnesium-regenerated sample is spectroscopically similar to the native purple bacteriorhodopsin, the electrooptical properties are rather similar to those of the cation-depleted blue sample, suggesting that it is very difficult to re-stabilize protein structures once cations are depleted. 相似文献
46.
Solubilisation of a Glutamate Binding Protein from Rat Brain 总被引:2,自引:2,他引:0
Rat brain synaptic plasma membranes were solubilised in either 1% Triton X-100 or potassium cholate and subjected to batch affinity adsorption on L-glutamate/bovine serum albumin reticulated glass fibre. The fibre was extensively washed, and bound proteins eluted with 0.1 mM L-glutamate in 0.1% detergent, followed by repeated dialysis to remove the glutamate from the eluted proteins. Aliquots of the dialysed extracts were assayed for L-[3H]glutamate binding activity in the presence or absence of 0.1 mM unlabelled L-glutamate (to define displaceable binding). Incubations were conducted at room temperature and terminated by rapid filtration through nitrocellulose membranes. Binding to solubilised fractions could be detected only following affinity chromatography. Binding was saturable and of relatively low affinity: KD = 1.0 and 1.8 microM for Triton X-100 and cholate extracts, respectively. The density of binding sites was remarkably high: approximately 18 nmol/mg protein for Triton X-100-solubilised preparations, and usually double this when cholate was employed. Analysis of structural requirements for inhibition of binding revealed that only a very restricted number of compounds were effective, i.e., L-glutamate, L-aspartate, and sulphur-containing amino acids. Binding was not inhibited significantly by any of the selective excitatory amino acid receptor agonists--quisqualate, N-methyl-D-aspartate, or kainate. The implication from this study is that the glutamate binding protein is similar if not identical to one previously isolated and probably is not related to the pharmacologically defined postsynaptic receptor subtypes, unless solubilisation of synaptic membranes resulted in major alterations to binding site characteristics. Since solubilisation with Triton X-100 is known to preserve synaptic junctional complexes, it seems likely that the origin of the glutamate binding protein may be extrajunctional, although its functional role is unknown. 相似文献
47.
Gynheung An 《Molecular & general genetics : MGG》1987,207(2-3):210-216
Summary Expression of the three chlorophyll a/b binding protein (cab) genes of Arabidopsis thaliana was studied in transformed tobacco tissues. For each cab gene, approximately 1000 bp of the promoter region plus a portion of the structural gene was inserted into a promoter-expression vector such that a translational fusion between the cab gene and the promoter-less chloramphenicol acetyltransferase (cat) gene was formed. The constructed molecules were introduced into either cultured tobacco cells or tobacco leaves and the promoter activity was monitored as chloramphenicol acetyltransferase activity. The light-grown tissues exhibited 1.5- to 60-fold greater promoter activity than did dark-grown tissues. Expression of the cab promoters was tissue specific: activities were much stronger in green leaves than other tissues. The cab promoters were almost equally active in transformed calli or shoots derived from leaves. However, in cultured tobacco cells, one promoter was two to three times stronger than the other two. The chimeric gene fusion, cab-cat, segregated in the F1 generation as a dominant Mendelian trait. 相似文献
48.
Nicolas Mermod Juan L. Ramos Amos Bairoch Kenneth N. Timmis 《Molecular & general genetics : MGG》1987,207(2-3):349-354
49.
Summary
Nocardia mediterranei strain LBG A3136 contains the 23.7 kb element pMEA100 in a chromosomally integrated form as well as in the free state (Moretti et al. 1985). The integrated form of this element can be excised precisely from the Nocardia chromosome without any accompanying rearrangements in flanking chromosomal DNA. After transfer into plasmid-free mutant strains, pMEA100 reintegrates site specifically into its original chromosomal locus. The exact mapping of the pMEA100 integration site was accomplished by restriction analysis and DNA sequencing. The attachment site of pMEA100, the junctions of its integrated form and plasmid-free chromosomal DNA of N. mediterranei contain an identical 47 bp long sequence which is probably required for site-specific recombination connected with integration and excision of pMEA100. Only one such sequence was found in the chromosome of pMEA100-free N. mediterranei derivatives as suggested by the single integration locus. 相似文献
50.
Spinach-leaf ferredoxin was identified as a calcium-binding protein by 45Ca autoradiography on nitrocellulose membranes and with the cationic carbocyanine dye 1-ethyl-2-[3-(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)-2-methylpropenyl] naphtho[1,2-d]thiazolium bromide (stains-all). Binding of 45Ca was observed at pH 6.8 and pH 7.8 and in the presence of 5 mM and 20 mM MgCl2. At the higher MgCl2 concentration the Ca2+-binding capacity is reduced. Only micromolar concentrations of LaCl3, however, are required to achieve a similar effect. Both the oxidized and reduced forms of ferredoxin bind calcium.Abbreviations PAGE
polyacrylamide gel electrophoresis
- SDS
sodium dodecyl sulfate
- stains-all
1-ethyl-2-[3-(1-ethylnaphtho[1,2-d]thiazolin-2-ylidene)-2-methylpropenyl] naptho[1,2-d]thiazolium bromide 相似文献