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91.
92.
在论文将分为两部分,目的是要回顾碳纤维及其原丝的生产技术、纤维结构及其主要性能(第一部分).并总结目前树脂基或水泥基碳纤维复合材料的现状(第二部分)。 相似文献
94.
世界卫生组织(WHO)于1973年首次把杀螟硫磷(fenitrothion)编入农药规格手册。有效成份的分析采用滴定法,该法基于杀螟硫磷在酸性溶液中被锌还原,然后用亚硝酸钠滴定还原产物胺。方法包括原药及其可湿性粉剂的测定。这一方法并不是专一的而且费时。在WHO杀虫剂化学与规格专家委员会1977年会议上,J.W.Miles和D.L.Mount 相似文献
95.
Kataeva IA Uversky VN Brewer JM Schubot F Rose JP Wang BC Ljungdahl LG 《Protein engineering, design & selection : PEDS》2004,17(11):759-769
Cellobiohydrolase CbhA from Clostridium thermocellum cellulosome is a multi-modular protein composed starting from the N-terminus of a carbohydrate-binding module (CBM) of family 4, an immunoglobulin(Ig)-like module, a catalytic module of family 9 glycoside hydrolases (GH9), X1(1) and X1(2) modules, a CBM of family 3 and a dockerin module. Deletion of the Ig-like module from the Ig-GH9 construct results in complete inactivation of the GH9 module. The crystal structure of the Ig-GH9 module pair reveals the existence of an extensive module interface composed of over 40 amino acid residues of both modules and maintained through a large number of hydrophilic and hydrophobic interactions. To investigate the importance of these interactions between the two modules, we compared the secondary and tertiary structures and thermostabilities of the individual Ig-like and GH9 modules and the Ig-GH9 module pair using both circular dichroism (CD) spectroscopy and differential scanning calorimetry (DSC). Thr230, Asp262 and Asp264 of the Ig-like module are located in the module interface of the Ig-GH9 module pair and are suggested to be important in 'communication' between the modules. These residues were mutated to alanyl residues. The structure, stability and catalytic properties of the native Ig-GH9 and its D264A and T230A/D262A mutants were compared. The results indicate that despite being able to fold relatively independently, the Ig-like and GH9 modules interact and these interactions affect the final fold and stability of each module. Mutations of one or two amino acid residues lead to destabilization and change of the mechanism of thermal unfolding of the polypeptides. The enzymatic properties of native Ig-GH9, D264A and T230A/D262A mutants are similar. The results indicate that inactivation of the GH9 module occurs as a result of multiple structural disturbances finally affecting the topology of the catalytic center. 相似文献
96.
普遍称为Benzofuroxan(BFO)的苯并呋咱-1-氧化物已证明能降低填充炭黑的硫化胶的滞后损失30%以上。BFO大概能促进弹性体和炭黑之间的键合,导致硫化胶“佩恩效应”降低。BFO在母炼胶混炼期间于不同温度下加入。为了最大限度地降低滞后损失,需要高温混炼,而且采用高比表面积的炭黑会更有效。镍盐会改善BFO和弹性体/炭黑间的反应。 相似文献
97.
Wolff RL Lavialle O Pédrono F Pasquier E Destaillats F Marpeau AM Angers P Aitzetmüller K 《Lipids》2002,37(1):17-26
The seed fatty acid (FA) compositions of Abietoids (Abies, Cedrus, Hesperopeuce, Keteleeria, Pseudolarix, and Tsuga) are reviewed in the present study in conclusion to our survey of Pinaceae seed FA compositions. Many unpublished data are
given. Abietoids and Pinoids (Pinus, Larix, Ficea, and Pseudotsuga)—constituting the family Pinaceae—are united by the presence of several Δ5-olefinic acids, taxoleic (5,9–18∶2), pinolenic
(5,9,12–18∶3) coniferonic (5,9,12,15–18∶4), keteleeronic (5,11–20∶2), and sciadonic (5,11,14–20∶3) acids, and of 14-methyl
hexadecanoic (anteiso-17∶0) acid. These acids seldom occur in angiosperm seeds. The proportions of individual Δ5-olefinic
acids, however, differ between Pinoids and Abietoids. In the first group, pinolenic acid is much greater than taxoleic acid,
whereas in the second group, pinolenic acid is greater than or equal to taxoleic acid. Moreover, taxoleic acid in Abietoids
is much greater than taxoleic acid in Pinoids, an apparent limit between the two subfamilies being about 4.5% of that acid
relative to total FA. Tsuga spp. appear to be a major exception, as their seed FA compositions are much like those of species from the Pinoid group.
In this respect, Hesperopeuce mertensiana, also known as Tsuga mertensiana, has little in common with Abietoids and fits the general FA pattern of Pinoids well. Tsuga spp. and H. mertensiana, from their seed FA compositions, should perhaps be separated from the Abietoid group and their taxonomic position revised.
It is suggested that a “Tsugoid” subfamily be created, with seed FA in compliance with the Pinoid pattern and other botanical
and immunological criteria of the Abietoid type. All Pinaceae genera, with the exception of Pinus, are quite homogeneous when considering their overall seed FA compositions, including Δ5-olefinic acids. In all cases but
one (Pinus), variations from one species to another inside a given genus are of small amplitude. Pinus spp., on the other hand, have highly variable levels of Δ5-olefinic acids in their FA compositions, particularly when sections
(e.g., Cembroides vs. Pinus sections) or subsections (e.g., Flexiles and Cembrae subsections from the section Strobus) are compared, although they show qualitatively the same FA patterns characteristic of Pinoids. Multicomponent analysis of
Abietoid seed FA allowed grouping of individual species into genera that coincide with the same genera otherwise characterized
by more classical botanical criteria. Our studies exemplify how seed FA compositions, particularly owing to the presence of
Δ5-olefinic acids, may be useful in sustaining and adding some precision to existing taxonomy of the major family of gymnosperms,
Pinaceae. 相似文献
98.
如果认为聚氯乙烯中出现的链岐化点是由于分子内链转移反应所致,则意味着叔氯原子是造成热不稳定性的原因。用氯乙烯与2—氯丙烯共聚而制成的典型聚合物分枝的多少与脱氯化氢难易之间的相互关系支持了这一论点。但是很明显在氯乙烯均聚物中,没有叔氯原子。现在人们公认,聚氯乙烯中的多数分枝是与主链中的—CH—基团相联的CH_2Cl基团最近的研究工作还未表示聚氯乙烯CH_2Cl含量与热不稳定性之间的相互关系。氯乙烯—烯丙基氯共聚而成的含有较多CH_2Cl基团的聚合物样品,使我们得以对聚氯乙烯热稳定性的影响做进一步的研究是有用的。 相似文献
99.
INTROGRESSING PHEROMONE QTL BETWEEN SPECIES: TOWARDS AN EVOLUTIONARY UNDERSTANDING OF DIFFERENTIATION IN SEXUAL COMMUNICATION 总被引:2,自引:0,他引:2
Groot AT Ward C Wang J Pokrzywa A O'Brien J Bennett J Kelly J Santangelo RG Schal C Gould F 《Journal of chemical ecology》2004,30(12):2495-2514
As a first step toward understanding how noctuid moths evolve species-specific pheromone communication systems, we hybridized and backcrossed two closely related moth species, Heliothis virescens (Hv) and H. subflexa (Hs), which differ qualitatively and quantitatively in their multi-component sex pheromone blends. We used amplified fragment length polymorphism (AFLP) marker-based mapping of backcross families to determine which of the 30 autosomes in these moths contained quantitative trait loci (QTL) controlling the percentages of specific chemical components in the pheromone blends. In two previous backcrosses to Hs, we found a strong depressive effect of Hv-chromosome 22 on the percentage of three acetate components in the pheromone gland. These acetates are present in Hs and absent in Hv. Here, we describe how we introgressed Hv-chromosome 22 into the genomic background of Hs. Selection for Hv-chromosome 22 started from backcross 3 (BC3) females. All females that had Hv-chromosome 22 and a low percentage of acetates (< 3% of the total amount of pheromone components present) were backcrossed to Hs males. In BC5 to BC8, we determined whether Hv-chromosome 22 was present by a) running only the primer pairs that would yield the markers for that chromosome, and/or b) determining the relative percentages of acetates in the pheromone glands. Either or both genotype and phenotype were used as a criterion to continue to backcross these females to Hs males. In BC9, we confirmed the isolation of Hv-chromosome 22 in the Hs genomic background, and backcrossed the males to Hs females to eliminate the Hv-sex chromosome as well as mitochondrial DNA. The pheromone composition was determined in BC3, BC5, and BC11 females with and without Hv-chromosome 22. All backcross females with Hv-chromosome 22 contained significantly less acetates than females without this chromosome. In addition, BC3 females with Hv-chromosome 22 contained significantly more Z11-16:OH than BC3 females without Hv-chromosome 22. However, in BC5 and BC11 females, the correlation between Z11-16:OH and Hv-chromosome 22 was lost, suggesting that there are separate QTL for the acetates and for Z11-16:OH, and that the relative amount of the alcohol component is only affected in epistasis with other (minor) QTL. Now that we have succeeded in isolating the chromosome that has a major effect on acetate production, we can test in behavioral experiments whether the presence of acetates may have been a driving force for a shift in pheromone composition. Such tests are necessary to move towards an evolutionary understanding of the differentiation in sexual communication in Heliothis spp. moths. 相似文献
100.