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41.
Molecular mechanical studies of proflavine and acridine orange intercalation. 总被引:4,自引:3,他引:1 下载免费PDF全文
Previous workers have reported that proflavine and acridine orange form various structurally different complexes with the dinucleoside phosphates rCpG and dCpG, with uniform C3'-endo and mixed C3'-endo (3'-5') C2'-endo sugar puckers being observed. We present theoretical calculations, based on the method of molecular mechanics, which support the experimental observations. The results suggest that the mixed C3'-edo (3'-5') C2'-endo pucker conformation isi intrinsically more stable than the uniform C3'-endo conformation, but that the additional stabilisation gained from specific, hydrogen bonding, interactions between nucleic acid and solvent, or intramolecularly within the nucleic acid, can lead to the adoption of the latter conformation, or of variants between the two. The role played by hydrogen bonding between amino-groups and nucleic acid phosphate appears more subtle than previously supposed. 相似文献
42.
B. A. Weiner 《Applied microbiology and biotechnology》1977,4(1):59-65
Summary Aerobic culture with solid substrates of fresh swine waste combined with corn resulted in lactic acid fermentation with odor control. Heterofermentative lactic acid bacteria produced lactic and homologous tatty acids from acetic through valeric acid (0.1 meq/dry g) to reduce pH 2 units to 4.2 to 4.6. During the fermentation, lactic acid organisms increased from 107 to 109/dry g. Coliform organisms remained steady in number at 106 organisms/dry g. Pilot-plant scale fermentation produced a product with 21 to 39% more methionine than corn but was still limiting for this amino acid as well as lysine for young pigs. Fermentation product from fresh waste-corn cultures was fed as the major dietary component to young pigs, hens, and sheep. Pigs showed gain and gain/feed diminished by one-third in 13-day trials. Laying hens performed comparably to controls in a 21-day test, and sheep did not discriminate against fermentation product. 相似文献
43.
Clonazepam and dopamine-related stereotyped behavior 总被引:1,自引:0,他引:1
The effect of clonazepam on behavioral stereotypy induced by a number of dopaminergic agonists was investigated. Clonazepam inhibited levodopa- and amphetamine-induced behavior in guinea pigs but did not alter lergotrile- or apomorphine-induced stereotypy. The results suggest that clonazepam influences the central dopaminergic system through a direct effect of dopaminergic presynaptic mechanisms. 相似文献
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45.
19F nuclear magnetic resonance studies of the coat protein of bacteriophage M13 in synthetic phospholipid vesicles and deoxycholate micelles. 总被引:1,自引:0,他引:1 下载免费PDF全文
The nonlytic, filamentous coliphage M13 offers an excellent model system for the study of membrane-protein interactions. We prepare derivatives of the protein containing fluorine-labeled amino acids and use 19F nuclear magnetic resonance (NMR) to study the protein in both deoxycholate micelles and phospholipid vesicles. We have previously described the in vivo preparation of an m-fluorotyrosyl derivative of M13 coat protein and also a method for incorporation of high levels of this protein into small, uniformly sized phospholipid vesicles of defined composition. Herein we describe the in vivo preparation and the characterization of an m-fluorophenylalanine derivative. We simultaneously compare the environment and mobility of the tyrosine and phenylalanine residues (the former in the hydrophobic region of the protein and the latter in the hydrophilic regions) as influenced by bile salt detergent or lipid interactions. 相似文献
46.
W V Williams T Kieber-Emmons J VonFeldt M I Greene D B Weiner 《The Journal of biological chemistry》1991,266(8):5182-5190
The variable regions of antibody molecules bind antigens with high affinity and specificity. This binding is imparted largely by the hypervariable portions of the variable region. Hypervariable regions typically fold into reverse turn or loop structures. Peptides derived from antibody hypervariable region sequences can bind antigens with similar specificity, albeit with markedly lower affinity. In this study, cyclic and dimeric peptide analogs of an anti-idiotypic/antireceptor antibody hypervariable region were developed. This antibody (87.92.6) binds to reovirus type 3 receptors on cells as well as to a neutralizing anti-reovirus type 3 monoclonal antibody (9B.G5). The cyclic peptides were utilized to probe the optimal conformation for binding to both the receptor and 9B.G5. By dimerizing or constraining the conformation of these peptides, higher affinity binding was produced. By utilizing several different cyclic peptides, the optimal conformation for binding was established. The conformationally optimized cyclic peptide possessed greater than 40-fold higher affinity for the receptor and the idiotype than the linear analog. This study suggests that conformationally constrained and dimeric peptides derived from antibody hypervariable loop sequences can bind antigens (including receptors) with reasonable affinity. hypervariable loop sequences can bind antigens (including 相似文献
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48.
Aldehyde dehydrogenase from bovine liver mitochondria has been crystallized using the sitting drop method of vapor diffusion at 22 degrees C. The crystals formed from solutions containing, 40 mM-sodium citrate, 1 mM-NAD+ and 21% to 24% polyethylene glycol 3400 (pH 5.3 to 5.5). X-ray diffraction data collected from these crystals indicate that the crystals belong to the orthorhombic space group P2(1)2(1)2(1) with cell dimensions of a = 153.7 A, b = 159.37 A and c = 101.45 A. The crystals diffract to at least 2.9 A and a tetramer may comprise the asymmetric unit. 相似文献
49.
The cDNA coding for the precursor (p-ALDH) or mature (m-ALDH) rat liver mitochondrial aldehyde dehydrogenase was cloned in an expression vector pT7-7 and expressed in Escherichia coli strain BL21 (DE3)/plysS. The p-ALDH expressed in E. coli was a soluble tetrameric protein. It exhibited virtually the same specific activity and KmS for substrates as m-ALDH. N-terminal sequencing of isolated p-ALDH provided the evidence that the catalytic activity was not derived from a partially processed mature-like enzyme. The assembly states of both p-ALDH and m-ALDH synthesized in a rabbit reticulocyte lysate were also determined. Both of them were monomers and could not bind to a 5'-AMP-Sepharose column, showing that the monomeric form of the enzyme is inactive. The stabilities in vivo and in vitro were compared between p-ALDH and m-ALDH expressed in E. coli. p-ALDH was less stable than was m-ALDH both in vivo and in vitro. Thus, although the conformations of p-ALDH and m-ALDH are similar, the presence of signal peptide is a destabilizing factor to the p-ALDH. p-ALDH expressed in E. coli could bind to and be translocated into rat liver mitochondria, however, with lower efficiency when compared to the import of p-ALDH synthesized in reticulocyte lysate. 相似文献
50.