全文获取类型
收费全文 | 695篇 |
免费 | 2篇 |
专业分类
综合类 | 1篇 |
化学工业 | 20篇 |
金属工艺 | 2篇 |
机械仪表 | 3篇 |
建筑科学 | 16篇 |
矿业工程 | 2篇 |
能源动力 | 2篇 |
轻工业 | 21篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 15篇 |
一般工业技术 | 18篇 |
冶金工业 | 574篇 |
自动化技术 | 16篇 |
出版年
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 2篇 |
2013年 | 8篇 |
2012年 | 7篇 |
2011年 | 6篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2004年 | 4篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 19篇 |
1998年 | 172篇 |
1997年 | 100篇 |
1996年 | 86篇 |
1995年 | 37篇 |
1994年 | 33篇 |
1993年 | 35篇 |
1992年 | 6篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1978年 | 1篇 |
1977年 | 12篇 |
1976年 | 16篇 |
1973年 | 1篇 |
1964年 | 1篇 |
1925年 | 1篇 |
排序方式: 共有697条查询结果,搜索用时 15 毫秒
1.
PJ Oefner SP Hunicke-Smith L Chiang F Dietrich J Mulligan RW Davis 《Canadian Metallurgical Quarterly》1996,24(20):3879-3886
Based on a high-performance liquid chromatographic pump, we have built a device that allows recirculation of DNA through a 63-microm orifice with ensuing fractionation to a minimum fragment size of approximately 300 base pairs. Residence time of the DNA fragments in the converging flow created by a sudden contraction was found to be sufficiently long to allow extension of the DNA molecules into a highly extended conformation and, hence, breakage to occur at midpoint. In most instances, 30 passages sufficed to obtain a narrow size distribution, with >90% of the fragments lying within a 2-fold size distribution. The shear rate required to achieve breakage was found to be inversely proportional to the 1.0 power of the molecular weight. Compared with a restriction digest, up to 40% of all fragments could be cloned directly, with only marginal improvements in cloning efficiency having been observed upon prior end repair with Klenow, T4 polymerase or T4 polynucleotide kinase. Sequencing revealed a fairly random distribution of the fragments. 相似文献
2.
3.
Two patients are presented where internal mammary artery grafting was performed for the relief of symptomatic coronary artery disease. At follow-up the internal mammary artery was occluded and a communication between the internal mammary vein and the native coronary artery was demonstrated. These patients were characterised by the early recurrence of angina or the appearance of a continuous murmur. Both patients were treated by re-operation with ligation of the arterio-venous fistula and saphenous vein grafting. 相似文献
4.
Mulligan Neil W.; Lozito Jeffrey P.; Rosner Zachary A. 《Canadian Metallurgical Quarterly》2006,32(4):836
Generation enhances memory for occurrence but may not enhance other aspects of memory. The present study further delineates the negative generation effect in context memory reported in N. W. Mulligan (2004). First, the negative generation effect occurred for perceptual attributes of the target item (its color and font) but not for extratarget aspects of context (location and background color). Second, nonvisual generation tasks with either semantic or nonsemantic generation rules (antonym and rhyme generation, respectively) produced the same pattern of results. In contrast, a visual (or data-driven) generation task (letter transposition) did not disrupt context memory for color. Third, generating nonwords produced no effect on item memory but persisted in producing a negative effect on context memory for target attributes, implying that (a) the negative generation effect in context memory is not mediated by semantic encoding, and (b) the negative effect on context memory can be dissociated from the positive effect on item memory. The results are interpreted in terms of the processing account of generation. The original, perceptual-conceptual version of this account is too narrow, but a modified processing account, based on a more generic visual versus nonvisual processing distinction, accommodates the results. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
Generation enhances item memory but may not enhance other aspects of memory. In 12 experiments, the author investigated the effect of generation on context memory, motivated in part by the hypothesis that generation produces a trade-off in encoding item and contextual information. Participants generated some study words (e.g., hot-___) and read others (e.g., hot-cold). Generation consistently enhanced item memory but did not enhance context memory. More specifically, generation disrupted context memory for the color of the target word but did not affect context memory for location, background color, and cue-word color. The specificity of the negative generation effect in context memory argues against a general item-context trade-off. A processing account of generation meets greater success. In addition, the results provide no evidence that generation enhances recollection of contextual details. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
From the rhizomes of Polygonatum alte-lobatum, two new homologous series of 1,4-benzoquinones, polygonaquinones A and B, a novel homoisoflavanone, a new gentrogenin glycoside and 13 known compounds were isolated and characterized. The structures of the new compounds were determined as two homologous series of three 2,5-dihydroxy-3-methyl-6-alkyl-1,4-benzoquinones and three 2-hydroxy-3-methyl-6-alkyl-1,4-benzoquinones, with chain lengths C21 to C23, and 4',5,7-trihydroxy-6,8-dimethylhomoisoflavanone and gentrogenin 3-O-beta-D-glucopyranosyl(1-->2)-[beta-D-xylopyranosyl(1-->3)] -beta-D-glucopyranosyl(1-->4)-beta-D-galactopyranoside. 相似文献
7.
V Kamath CN Jones JC Yip BB Varasteh AH Cincotta GM Reaven YD Chen 《Canadian Metallurgical Quarterly》1997,20(11):1697-1701
OBJECTIVE: To assess the effect on various aspects of carbohydrate and lipid metabolism of administering a quick-release formulation of bromocriptine (Ergoset) to obese, nondiabetic, hyperinsulinemic women. RESEARCH DESIGN AND METHODS: Hourly concentrations of prolactin, glucose, insulin, free fatty acid (FFA), and triglyceride were measured for 24 h before and after approximately 8 weeks of treatment with Ergoset. In addition, fasting lipid and lipoprotein concentrations and the steady-state plasma glucose (SSPG) concentration in response to a continuous infusion of somatostatin, insulin, and glucose were determined before and after Ergoset administration. RESULTS: Circulating prolactin concentrations were dramatically decreased (P < 0.001) following treatment, associated with a significant fall (P < 0.05) in 24-h-long plasma glucose, FFA, and triglyceride concentrations. Neither circulating plasma insulin concentrations nor the ability of insulin to mediate glucose disposal changed with treatment. Finally, fasting total cholesterol fell (P < 0.05) and the ratio of total to HDL cholesterol decreased (P = 0.06) in association with Ergoset treatment. CONCLUSIONS: The fact that significant metabolic improvement was seen in the obese nondiabetic hyperinsulinemic women studied suggests that Ergoset could be of therapeutic benefit in clinical conditions of hyperglycemia and/or dyslipidemia. 相似文献
8.
The years of the great depression were marked with unemployment and economic ruin for many people. Americans were left feeling helpless and hopeless. After the 1932 presidential election of Franklin Roosevelt, his administration embarked on a course of government known as the New Deal. Many new and innovative programs were established to create jobs and a sense of hope for the public. This article will examine four programs that were of particular interest to nursing: the Federal Emergency Relief Act, the Civil Works Act, the Works Progress Act, and the Social Security Act. Nurses of the time embraced these programs. They participated in their development and implementation and made a difference in the lives of many desperate Americans. 相似文献
9.
解放前我国学者对新疆石油地质的调查和研究 总被引:1,自引:0,他引:1
20世纪初,随着近代地质学在中国的形成和发展,一些学者开始了对新疆石油地质的调查和研究,30年代末以前,翁文灏,章鸿钊等学者利用文献和间接获得的资料,对新疆石油资源进行了宏观考察和若干重要油苗的地质研究;40年代开始,黄汲清等地质家在新疆进行实地考察,对独山子油田进行了详细研究,并在南北疆部分地区进行了路线性石油地质调查。 相似文献
10.
The prevalence of several paraneoplastic syndromes associated with ovarian cancer was determined from a clinicopathological study of 908 patients with primary ovarian malignancy in the North East Thames Region. The diversity and rarity of these manifestations are great and the explanation for them is difficult. Circumstantial evidence suggests that in some cases an autoimmune phenomenon is the most plausible cause. 相似文献