首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   501篇
  免费   6篇
电工技术   3篇
化学工业   79篇
金属工艺   12篇
机械仪表   6篇
建筑科学   4篇
矿业工程   1篇
能源动力   4篇
轻工业   15篇
水利工程   1篇
无线电   10篇
一般工业技术   30篇
冶金工业   317篇
自动化技术   25篇
  2018年   4篇
  2017年   2篇
  2016年   4篇
  2014年   4篇
  2013年   11篇
  2012年   14篇
  2011年   4篇
  2010年   9篇
  2009年   3篇
  2008年   9篇
  2007年   8篇
  2006年   6篇
  2005年   7篇
  2004年   6篇
  2003年   6篇
  2002年   2篇
  2001年   2篇
  2000年   3篇
  1999年   15篇
  1998年   95篇
  1997年   69篇
  1996年   30篇
  1995年   21篇
  1994年   12篇
  1993年   26篇
  1992年   2篇
  1991年   4篇
  1990年   3篇
  1989年   5篇
  1988年   11篇
  1987年   4篇
  1986年   3篇
  1985年   7篇
  1984年   5篇
  1983年   6篇
  1982年   6篇
  1981年   9篇
  1980年   7篇
  1978年   2篇
  1977年   8篇
  1976年   29篇
  1975年   2篇
  1968年   2篇
  1966年   2篇
  1963年   1篇
  1960年   1篇
  1959年   2篇
  1958年   1篇
  1957年   2篇
  1955年   2篇
排序方式: 共有507条查询结果,搜索用时 234 毫秒
11.
Structure–property relationships have been developed for sulfonated poly(butylene terephthalate) copolymers. The compositional variables investigated were sulfonate content, molecular weight, and polymer endgroup composition, and the fundamental polymer properties evaluated were melt viscosity, crystallization kinetics, and impact strength. It was found that all compositional variables significantly affect all of the polymer properties of interest. The most interesting effect is the influence of polymer endgroup composition on polymer properties. The trends indicate that the carboxylic acid endgroups form intermolecular interactions with sodium sulfonate groups, resulting in a decrease in the strength of intermolecular ionic interactions between sodium sulfonate groups. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4662–4771, 2006  相似文献   
12.
A combinatorial process has been developed for the high throughput production and evaluation of surface coatings. The workflow designed for the production of arrays of liquid coatings involves the robotic transfer of aliquots of solutions of raw materials to an array of glass vials and mixing of the coatings using an unconventional magnetic stirring process. An investigation of the capability of the workflow to accurately and repeatedly prepare coating arrays was conducted as a function of solution viscosity and aliquot size. In addition, mixing capability was evaluated as a function of solution viscosity, total solution volume, and mechanism of stirring. Overall, the results of the study indicated that adequate accuracy and repeatability of the coating preparation process can be achieved as long as raw material solutions are designed such that viscosity is below about 250 cP and aliquot sizes are above about 75 μl. With regard to mixing capability, total solution volume was found to have a profound affect as did the stirring mechanism.  相似文献   
13.
Summary Asparagus seed, Mary Washington variety, was found to contain 14.7% of glyceride oil having iodine value 135.1, saponification value 185.5, and unsaponifiable matter 1.46%. The oil was converted to methyl esters, and the mixed esters were separated by fractional distillation and low-temperature crystallization. The acids were identified by chemical and physical methods. The % composition of the fatty acids is estimated from the data as follows: palmitic 3, linoleic 57, oleic 27, stearic 2, eicosenoic 1.5, arachidic 0.6, undetermined 9. The oil is somewhat similar to corn oil in composition. It has at least 2% of acids of the C20 series, which have not been reported previously in this plant family (Liliaceae). Presented at the meeting of the American Oil Chemists' Society, Philadelphia, Pa., October 10–12, 1955. Issued as N.R.C. No. 4426.  相似文献   
14.
Field survey of the geometrical isomers of 7,9-dodecadienyl alcohol, acetate, and aldehyde has resulted in attractants and inhibitors for three species of tortricid moths.Epinotia silvertoniensis and an undescribedEpinotia sp. were all attracted to (Z,Z)-7,9-dodecadienyl acetate. AnotherEpinotia sp. was attracted to (Z,Z)-7,9-dodecadienyl acetate and (Z,Z)-7,9-dodecadien-1-ol. Electroantennogram data and inhibition patterns for one of theEpinotia sp. are also reported. In addition,E. criddleana was attracted to lures containing (E)-9-dodecenyl acetate.  相似文献   
15.
Combinatorial chemistry has proven to be a valuable tool for the development of new compounds. In the pharmaceutical industry, where combinatorial chemistry began, the approach has been instrumental in the high-speed development of new drugs. Due to the overwhelming success of the combinatorial methodology in the pharmaceutical industry, it has been recently applied to materials development. We have recently developed a combinatorial factory capable of preparing and evaluating on the order of 100 organic clear coatings in a day.

One of the most challenging aspects of the creation of the combinatorial factory was the development of the high throughput screening (HTS) methods for the primary coating properties of interest such as optical clarity, abrasion resistance, adhesion, and weatherability. For each property, an entirely new method was developed that allowed for rapid measurement of these properties on very small samples. This paper describes various aspects of the development of these novel measurement systems including the correlation of the HTS methods with conventional, industry standard measurement methods.  相似文献   

16.
Male moths belonging to 17 species of Geometridae and nine species of Noctuidae were captured in traps baited with synthetic chemicals as part of a field screening program. The compounds tested were the C18-C22 homologs of: (1) (3Z,6Z,9Z)-triene hydrocarbons; (2) mixtures containing equal quantities of (3Z,6Z)-cis-9,10-expoxydienes, (3Z,92Z)-cis-6,7-epoxydienes, and (6Z,9Z)-cis-3,4-epoxydienes; (3) (3Z,6Z)-9S,10R-epoxydienes; (4) (3Z,6Z)-9R,10S-epoxydienes; and (5) (3Z,6Z,9Z,11E)-nonadecatetraene. Field captures and electroantennographic assays revealed a high degree of specificity in the responses of many species to the synthetic chemicals. In several species the ability of males to discriminate between the 9S,10R and 9R,10S enantiomers of the monoepoxydiene isomers was clearly shown. Synergists and inhibitors were discovered for several of the reported attractants, some of which were not previously known to have semiochemical activity. The geometrid moths captured includedEpirrhoe sperryi (Herbulot),Mesoleuca ruficillata (Guenée),Triphosa haesitata (Guenée),Metanema inatomaria (Guenée),Prochoerodes transversata (Drury),Cabera erythemaria (Guenée),Synaxis jubararia (Hulst),Dysstroma brunneata ethela (Hulst),Eulithes testata (Linnaeus),Sicya macularia (Harris),Xanthorhoe iduata (Guenée),X. abrasaria aquilonaria (Herrich-Schäffer),X. munitata (Hübner),Itame loricaria (Eversmann),Eupithecia annulata (Hulst),E. rovocastaliata (Packard) andE. satyrata dodata (Taylor). The noctuid moths captured includedBleptina caradrinalis (Guenée),Idia américalis (Guenée),I. aemula (Hübner),Rivula propinqualis (Guenée),Lomanaltes eductalis (Walker),Spargaloma sexpunctata (Grote),Caenurgina distincta (Neumuller),Euclidia cuspidea (Hübner), andZale duplicata (Bethune). Six of the nine noctuid species captured belong to three subfamilies for which sex attractants had not been reported previously. Details for the stereospecific synthesis of (3Z,6Z)-cis-9,10-epoxydienes are also reported.Issued as NRCC No. 24314.  相似文献   
17.
An array of perfectly alternating polycarbonate‐polydimethylsiloxane (PC‐PDMS) multiblock copolymers possessing systematic variations in block molecular weights were successfully produced by coupling preformed PC and PDMS telechelic oligomers using hydrosilylation. Based on gel permeation chromatography results, the multiblock copolymers were essentially void of the oligomeric precursors. Despite the relatively large difference in solubility parameter between PC and PDMS, the multiblock copolymers exhibited significant partial miscibility between the two phases. As expected, the degree of partial miscibility was dependent on the molecular weight of the blocks with the extent of partial miscibility increasing with decreasing block molecular weights. Morphological characterization using small angle X‐ray scattering showed that, at a given PC block molecular weight, the uniformity of the two phase morphology increased with increasing PDMS block molecular weight, which is consistent with a decrease in the extent of phase mixing with increasing PDMS block molecular weight. POLYM. ENG. SCI., 54:1648–1663, 2014. © 2013 Society of Plastics Engineers  相似文献   
18.
Videolaparoscopic cholecystectomy is considered the treatment of choice for simple cholelithiasis. Now many surgeons consider the laparscopic procedure usable also in the complicated biliary lithiasis like acute cholecystitis and choledocholithiasis. The authors report their recent experience of the laparoscopic treatment of biliary lithiasis, regarding 221 non-selected patients (69% symptomatic cholelithiasis, 20% chronic cholecystitis, 4.5% acute cholecystitis, 4.5% coledocolithiasis, 2% hydrops). The diagnostic-therapeutic protocol and the results are described and compared with the beginning of their experience, when they treated only symptomatic gallbladder stone disease, and with the reports of the literature. The authors concluded that the laparoscopic procedure is a good chance for the surgeon in the treatment of all cases of benign biliary disease. But, in particular for patients with choledocholithiasis, he has be able to know all the diagnostic and therapeutic possibilities, to choose the best in every single case.  相似文献   
19.
Marshall syndrome is a rare, autosomal dominant skeletal dysplasia that is phenotypically similar to the more common disorder Stickler syndrome. For a large kindred with Marshall syndrome, we demonstrate a splice-donor-site mutation in the COL11A1 gene that cosegregates with the phenotype. The G+1-->A transition causes in-frame skipping of a 54-bp exon and deletes amino acids 726-743 from the major triple-helical domain of the alpha1(XI) collagen polypeptide. The data support the hypothesis that the alpha1(XI) collagen polypeptide has an important role in skeletal morphogenesis that extends beyond its contribution to structural integrity of the cartilage extracellular matrix. Our results also demonstrate allelism of Marshall syndrome with the subset of Stickler syndrome families associated with COL11A1 mutations.  相似文献   
20.
Alkenyl acetates containing both geometrical isomers can be produced by a single controlled catalytic hydrogenation of the corresponding alkynyl acetate. The hydrogenation is capable of yielding formulations containing up to 60% trans isomer; the reduction is attended by positional isomerization in both geometrical isomers.NRCC No. 16834.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号