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排序方式: 共有1006条查询结果,搜索用时 15 毫秒
41.
F Venerini M Sette M E Stroppolo A De Martino A Desideri 《Archives of biochemistry and biophysics》1999,366(1):70-74
A Cu,Co derivative of the Cu,ZnSOD from Photobacterium leiognathi, in which cobalt has been selectively substituted for zinc, has been prepared and spectroscopically investigated. The derivative shows three bands in the visible region at 530, 566, and 600 nm when copper is in the oxidized state. Reduction or depletion of the copper ion produce a shift of the band absorbing at 600 to 590 nm because of the detachment from copper of the imidazolate bridging the two metals when copper is in the oxidized state. Numerous isotropically shifted 1H NMR lines are observed when copper is oxidized, confirming the presence of the imidazolate bridge between the two metals. Comparison of the optical and the NMR spectra with those observed for the eukaryotic enzyme reveals the occurrence of slight but unambiguous differences diagnostic of a different degree of distortion of the metal cluster between the prokaryotic and eukaryotic enzymes. 相似文献
42.
43.
Rigano MM Alvarez ML Pinkhasov J Jin Y Sala F Arntzen CJ Walmsley AM 《Plant cell reports》2004,22(7):502-508
Transgenic plants are potentially safe and inexpensive vehicles to produce and mucosally deliver protective antigens. However, the application of this technology is limited by the poor response of the immune system to non-particulate, subunit vaccines. Co-delivery of therapeutic proteins with carrier proteins could increase the effectiveness of the antigen. This paper reports the ability of transgenic Arabidopsis thaliana plants to produce a fusion protein consisting of the B subunit of the Escherichia coli heat-labile enterotoxin and a 6 kDa tuberculosis antigen, the early secretory antigenic target ESAT-6. Both components of the fusion protein were detected using GM1-ganglioside-dependent enzyme-linked immunosorbant assay. This suggested the fusion protein retained both its native antigenicity and the ability to form pentamers.Abbreviations
ELISA
Enzyme linked immunosorbant assay
-
ESAT-6
Early secretory antigenic target (6 kDa)
-
ETEC
Enterotoxigenic Escherichia coli
-
LTB
B subunit of E. coli heat-labile enterotoxin
Communicated by W.A. Parrott 相似文献
44.
Raveh Tilleman T Tilleman MM Krekels GA Neumann MH 《Plastic and reconstructive surgery》2004,113(3):857-861
The common excision skin pattern is either a fusiform ellipse or another pattern with dissimilar length and width. The purpose of this study was to define the most advantageous skin pattern regarding skin waste, vertex angle, and scar length. Five skin excision patterns used traditionally for closure of round lesions were analyzed: fusiform ellipse, fusiform circle, rhomboid, mosque, and S-shaped. In the analysis, the pattern characteristics were formulated by geometric principles, from which the results were compared. The smallest skin waste was found in rhomboid and mosque patterns, whereas the largest skin waste was found in the fusiform circle and ellipse. The vertex angle was found to decrease monotonously with the excision length-to-width ratio for all patterns except the mosque shape, which is zero per definition. The paradigm stating that a vertex angle of 30 degrees or less is maintained for length-to-width ratios below 4 in the surgical ellipse was found incorrect. It holds only for rhomboid and S-shaped excisions. The scar length was found almost independent of the pattern, with a variance of 3 percent. The authors conclude that the most advantageous surgical skin patterns are the rhomboid and mosque excisions. 相似文献
45.
In this paper, we report an AFM study on the supramolecular structures adopted by the synthetic polypentapeptide poly(ValGlyGlyValGly), whose monomeric sequence is an abundant, simple building block of elastin. The polypeptide was analyzed by deposition from both methanolic and aqueous suspensions, showing different behaviors. In methanol, the polypeptide is able to evolve, in a time-dependent way, from layers to ribbons to beaded filaments. When the equilibrium is reached, the formation of well-defined dendritic structures is also observed. This restructuring of the polypentapeptide seems to be reminiscent of a sort of Rayleigh instability. When deposited from aqueous suspensions, the polypeptide self-assembles either in fibrillar networks or in amyloid-like patterns, both of them being found in elastin or elastin-related polypeptides. As a general finding, poly(ValGlyGlyValGly) seems to constitute an excellent mimetic of the supramolecular properties of native elastin. 相似文献
46.
Musayev FN Di Salvo ML Ko TP Schirch V Safo MK 《Protein science : a publication of the Protein Society》2003,12(7):1455-1463
Pyridoxine 5'-phosphate oxidase catalyzes the terminal step in the synthesis of pyridoxal 5'-phosphate. The cDNA for the human enzyme has been cloned and expressed in Escherichia coli. The purified human enzyme is a homodimer that exhibits a low catalytic rate constant of approximately 0.2 sec(-1) and K(m) values in the low micromolar range for both pyridoxine 5'phosphate and pyridoxamine 5'-phosphate. Pyridoxal 5'-phosphate is an effective product inhibitor. The three-dimensional fold of the human enzyme is very similar to those of the E. coli and yeast enzymes. The human and E. coli enzymes share 39% sequence identity, but the binding sites for the tightly bound FMN and substrate are highly conserved. As observed with the E. coli enzyme, the human enzyme binds one molecule of pyridoxal 5'-phosphate tightly on each subunit. 相似文献
47.
Kino T Souvatzoglou E De Martino MU Tsopanomihalu M Wan Y Chrousos GP 《The Journal of biological chemistry》2003,278(28):25651-25656
48.
Two different isoforms of glucose-6-phosphate dehydrogenase (Glc6PDH; EC 1.1.1.49) have been partially purified from barley
(Hordeum vulgare L., cv. Alfeo) roots. The procedure included an ammonium sulfate step, Q-Sepharose and Reactive Blue agarose chromatography,
and led to 60-fold and 150-fold purification for the two enzymes, respectively. The Glc6PDH 1 isoform accounts for 17% of
total activity of the enzyme in roots, and is very sensitive to the effects of NADP+/NADPH ratio and dithiothreitol; the Glc6PDH 2 isoform is less affected by reducing power and represents 83% of the total
activity. The isoforms showed distinct pH optima, isoelectric points, K
m for glucose-6-phosphate and a different electrophoretic mobility. The kinetic properties for the two enzymes were affected
by ATP and metabolites. Both enzymes are inhibited to different extents by ATP when magnesium is omitted from the assay mixture,
whereas the addition of ATP-Mg2+ had no effect on Glc6PDH activities. The Glc6PDH isoforms are usually present in the plastids and cytosol of plant cells.
To verify the intracellular locations of the enzymes purified from barley roots, Glc6PDH was purified from isolated barley
root plastids; this isoform showed kinetic parameters coincident with those found for Glc6PDH 1, suggesting a plastid location;
the enzyme purified from the soluble fraction had kinetic parameters resembling those of Glc6PDH 2, confirming that this isoform
is present in the cytosol of barley roots.
Received: 21 June 2000 / Accepted: 28 July 2000 相似文献
49.
Mariani F Goletti D Ciaramella A Martino A Colizzi V Fraziano M 《Current molecular medicine》2001,1(2):209-216
Human macrophages represent the first line of defense for the containment of Mycobacterium tuberculosis infection. After phagocytosis, macrophages express activation surface markers and produce proinflammatory cytokines and chemokines whose main role is to control pathogen spreading by recruiting peripheral lymphocytes and monocytes at the site of inflammation. However, in the case of a concomitant human immunodeficiency virus (HIV) infection, these signals strongly enhance the susceptibility to viral infection both at the viral entry and replication levels. Under these conditions, viral expansion extends beyond tissue macrophages to T cells and vice-versa, according to the emerging viral phenotype. In absence of an efficient immune response, Mycobacterium tuberculosis can replicate in macrophages in an uncontrolled fashion culminating in macrophage death by apoptosis. As a consequence, a more severe form of immunedepression, involving both innate and specific immune responses, could be responsible for both ematogenous mycobacterial dissemination and extrapulmonary form of tuberculosis in HIV-infected patients. 相似文献
50.
Rosano C Zuccotti S Bucciantini M Stefani M Ramponi G Bolognesi M 《Journal of molecular biology》2002,321(5):785-796
[NiFe]-hydrogenases require a set of complementary and regulatory proteins for correct folding and maturation processes. One of the essential regulatory proteins, HypF (82kDa) contains a N-terminal acylphosphatase (ACT)-like domain, a sequence motif shared with enzymes catalyzing O-carbamoylation, and two zinc finger motifs similar to those found in the DnaJ chaperone. The HypF acylphosphatase domain is thought to support the conversion of carbamoylphosphate into CO and CN(-), promoting coordination of these ligands to the hydrogenase metal cluster. It has been shown recently that the HypF N-terminal domain can aggregate in vitro to yield fibrils matching those formed by proteins linked to amyloid diseases. The 1.27A resolution HypF acylphosphatase domain crystal structure (residues 1-91; R-factor 13.1%) shows a domain fold of betaalphabetabetaalphabeta topology, as observed in mammalian acylphosphatases specifically catalyzing the hydrolysis of the carboxyl-phosphate bonds in acylphosphates. The HypF N-terminal domain can be assigned to the ferredoxin structural superfamily, to which RNA-binding domains of small nuclear ribonucleoproteins and some metallochaperone proteins belong. Additionally, the HypF N-terminal domain displays an intriguing structural relationship to the recently discovered ACT domains. The structures of different HypF acylphosphatase domain complexes show a phosphate binding cradle comparable to the P-loop observed in unrelated phosphatase families. On the basis of the catalytic mechanism proposed for acylphosphatases, whereby residues Arg23 and Asn41 would support substrate orientation and the nucleophilic attack of a water molecule on the phosphate group, fine structural features of the HypF N-terminal domain putative active site region may account for the lack of acylphosphatase activity observed for the expressed domain. The crystallographic analyses here reported were undertaken to shed light on the molecular bases of inactivity, folding, misfolding and aggregation of the HypF N-terminal acylphosphatase domain. 相似文献