全文获取类型
收费全文 | 151篇 |
免费 | 0篇 |
国内免费 | 2篇 |
专业分类
化学工业 | 1篇 |
金属工艺 | 2篇 |
轻工业 | 4篇 |
武器工业 | 1篇 |
无线电 | 5篇 |
一般工业技术 | 4篇 |
冶金工业 | 132篇 |
自动化技术 | 4篇 |
出版年
2015年 | 1篇 |
2013年 | 3篇 |
2010年 | 1篇 |
2008年 | 1篇 |
2007年 | 1篇 |
2006年 | 2篇 |
2003年 | 1篇 |
2002年 | 1篇 |
1999年 | 4篇 |
1998年 | 27篇 |
1997年 | 26篇 |
1996年 | 17篇 |
1995年 | 15篇 |
1994年 | 13篇 |
1993年 | 7篇 |
1992年 | 1篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1985年 | 1篇 |
1977年 | 2篇 |
1976年 | 7篇 |
1973年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有153条查询结果,搜索用时 15 毫秒
1.
Photoinduced cross-links between the iodinated Lys26-p-azidobenzoyl derivative of neurotoxin II from Naja naja oxiana cobra venom and nicotinic acetylcholine receptor from Torpedo californica (AChR) have been studied in the presence of alpha-conotoxin GI from the marine snail C. geographus. Preincubation of the AChR-enriched membranes with increasing concentrations of alpha-conotoxin GI protects first the gamma subunit from photolabelling and then the delta subunit, the IC50 values being 0.76 and 5.01 microM, respectively. The results obtained, in view of the relevant data in literature, demonstrate that the (alpha + gamma) site, which is the high affinity site for d-tubocurarine, has also a higher affinity for an alpha-conotoxin than the (alpha + delta) containing site. The latter has a somewhat higher affinity than the (alpha + gamma) site towards some naturally occurring snake venom alpha-neurotoxins or their derivatives. 相似文献
2.
A semi-quantitative right coronary artery score (RCA score) was derived from the ratio of the number of the major left ventricular branches of the right coronary artery to the total of the right coronary and left circumflex arteries, to stratify the extent of perfusion in patients with right coronary artery dominance. Thirty-seven patients with one-vessel coronary disease involving a dominant right coronary artery proximal to the left ventricular branches were selected for study. Thallium scintigraphy was performed after right intracoronary injection in 11 patients, and 26 patients underwent conventional stress thallium scintigraphy (24 exercise thallium and two dipyridamole thallium scintigraphy). Thallium scores of perfusion region size after right intracoronary thallium injection and perfusion defect size in stress thallium studies were quantitated from planar thallium images. Both the RCA score and the regional thallium scores spanned over a wide range. The RCA score (range 0.23-0.85) correlated best with the posterior (70 degrees left anterior oblique view) plus lateral segment (40 degrees left anterior oblique view) thallium score (r = 0.88 and 0.53 for intracoronary and stress thallium studies respectively). It also correlated with the summed thallium scores in the posterior, lateral, apical and inferior segments (r = 0.73 and 0.54 respectively) but not with thallium scores in the apex or inferior segment alone. The proposed RCA score quantitates the variable posterolateral perfusion territory of the right coronary artery, and could stratify the area of myocardium at risk from coronary stenosis in the majority of patients with right coronary dominance. 相似文献
3.
4.
Barabanenkov Yu.N. Kravtsov Yu.A. Ozrin V.D. Saichev A.I. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1991,79(10):1367-1370
Backscattering enhancement is discussed as a universal wave phenomenon inherent to waves of whatever physical nature: electromagnetic, acoustic, spin, etc. This phenomenon arises due to multichannel wave propagation from a source to a scatterer and back and may be observed in the vicinity of the source because of mutual coherence of waves passing in opposite directions along identical (coherent) channels. Backscattering enhancement may be revealed when the wave field is scattered: by a system of chaotically distributed scatterers or by a system of inhomogeneities; by a body embedded in a turbulent medium; by a single body placed near an interface or within a waveguide (randomness of body position is assumed); by a body of complex form or a system of several scatterers randomly oriented in space; by a rough surface; and by many other physical systems. Possible practical applications of these effects are analyzed 相似文献
5.
Crystal structure of TNF-alpha mutant R31D with greater affinity for receptor R1 compared with R2 总被引:2,自引:0,他引:2
Reed C; Fu ZQ; Wu J; Xue YN; Harrison RW; Chen MJ; Weber IT 《Protein engineering, design & selection : PEDS》1997,10(10):1101-1107
Crystal structures have been determined of recombinant human tumor necrosis
factor-alpha (TNF-alpha) and its R31D mutant that preferentially binds to
TNF receptor R1 with more than seven times the relative affinity of binding
to receptor R2. Crystals of the wild-type TNF were of space group
P4(1)2(1)2 and had unit cell dimensions of a = b = 94.7 and c = 117.4 A.
Refinement of the structure gave an R-factor of 22.3% at 2.5 A resolution.
The crystals of TNF R31D mutant diffracted to 2.3 A resolution, and were of
identical space group to the wild type with unit cell dimensions of a = b =
95.4 and c = 116.2 A, and the structure was refined to an R-factor of
21.8%. The trimer structures of the wild-type and mutant TNF were similar
with a root mean square (r.m.s.) deviation of 0.56 A for Calpha atoms;
however, the subunits within each trimer were more variable with an average
r.m.s. deviation of 1.00 A on Calpha atoms for pairwise comparison of
subunits. Model complexes of TNF with receptors R1 and R2 have been used to
predict TNF-receptor interactions. Arg31 in all three subunits of wild-type
TNF is predicted to form an ionic interaction with the equivalent glutamic
acid in both receptors R1 and R2. Asp31 of the TNF R31D mutant is predicted
to interact differently with the two receptors. The side chain of Asp31 in
two subunits of the TNF mutant is predicted to form hydrogen bond
interactions with Ser59 or Cys70 of R1, while it has no predicted
interactions with R2. The loss of three strong ionic interactions of Arg31
and the electrostatic repulsion of Asp31 with Glu in the receptors is
consistent with the reduced binding of the R31D mutant to both receptors
relative to wild-type TNF. The replacement of these ionic interactions by
two weaker hydrogen bond interactions between Asp31 of the R31D mutant and
R1, compared with no interactions with R2, is in agreement with the
observed preferential binding of the R31D mutant to R1 over R2. Analysis of
the structure and function of receptor-discriminating mutants of TNF will
help understand the biological role of TNF and facilitate its use as an
antitumor agent.
相似文献
6.
7.
8.
RT Matheson DR Miller MJ Lacombe YN Han S Iwanaga H Kato KD wuepper 《Canadian Metallurgical Quarterly》1976,58(6):1395-1406
Flaujeac trait is the functional deficiency of a plasma protein of the intrinsic coagulation, kinin-forming, and plasma fibrinolytic pathways. The Flaujeac factor in man has been isolated and tentatively identified as a kininogen of high molecular weight (HMW). Highly purified bovine HMW-kininogen, but not bovine low molecular weight kininogen, repaired Flaujeac factor deficiency. The two subspecies of this molecule, HMW-kininogen a and HMW-kininogen b, also corrected Flaujeac factor deficiency. When bovine HMW-kininogen was incubated with bovine plasma kallikrein, kinin-free HMW-kininogen, bradykinin, and a glycopeptide fragment (peptide 1-2; 12,584 daltons) were rapidly released. None of these fragmentation products corrected Flaujeac factor deficiency alone or in mixtures. The function of HMW-kininogen appeared to depend upon the structural integrity of the native molecule. When injected in concentrations of 2 pmol-8 nmol/0.1 ml, peptide 1-2 caused increased vascular permeability in rabbits, rats, or guinea pigs. The enhanced permeability was maximal within 1-2 min and terminated in 5-10 min, differing from that of bradykinin or histamine. Injected together in equimolar amounts, peptide 1-2 and bradykinin produced a synergistic permeability response which was immediate in onset as well as prolonged in duration. Peptide 1-2 is a rapidly acting, highly basic glyco-peptide which mediates increased vascular permeability in a complementary and synergistic manner with bradykinin. 相似文献
9.
Detailed active site configuration of a new crystal form of methanol dehydrogenase from Methylophilus W3A1 at 1.9 A resolution 总被引:1,自引:0,他引:1
ZX Xia YN He WW Dai SA White GD Boyd FS Mathews 《Canadian Metallurgical Quarterly》1999,38(4):1214-1220
The three-dimensional structure of a new crystal form of methanol dehydrogenase from Methylophilus W3A1 has been obtained in the presence of substrate using data recorded at a synchrotron. The structure of this approximately 140 kDa heterotetramer, refined at 1. 9 A resolution, reveals the detailed configuration of its redox cofactor, pyrroloquinoline quinone (PQQ). C4, one of the oxygen-bearing atoms of this orthoquinone is in a planar configuration while C5, which bears the other quinone oxygen, is tetrahedral, suggesting that the PQQ is in the semiquinone redox state. The substrate binding site has been identified close to PQQ and to the side chain of Asp297, the putative active site base. The proximity of the hydroxyl of methanol to C5 of PQQ compared to the greater separation of the substrate methyl group from C5 supports the addition-elimination reaction mechanism involving a hemiketal intermediate. 相似文献
10.