全文获取类型
收费全文 | 714篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 17篇 |
综合类 | 1篇 |
化学工业 | 119篇 |
金属工艺 | 36篇 |
机械仪表 | 3篇 |
建筑科学 | 25篇 |
能源动力 | 28篇 |
轻工业 | 71篇 |
水利工程 | 1篇 |
石油天然气 | 3篇 |
武器工业 | 1篇 |
无线电 | 40篇 |
一般工业技术 | 131篇 |
冶金工业 | 179篇 |
原子能技术 | 10篇 |
自动化技术 | 56篇 |
出版年
2021年 | 10篇 |
2018年 | 10篇 |
2017年 | 7篇 |
2016年 | 5篇 |
2014年 | 12篇 |
2013年 | 42篇 |
2012年 | 24篇 |
2011年 | 29篇 |
2010年 | 33篇 |
2009年 | 26篇 |
2008年 | 17篇 |
2007年 | 16篇 |
2006年 | 31篇 |
2005年 | 22篇 |
2004年 | 26篇 |
2003年 | 27篇 |
2002年 | 24篇 |
2001年 | 12篇 |
2000年 | 7篇 |
1999年 | 15篇 |
1998年 | 32篇 |
1997年 | 24篇 |
1996年 | 20篇 |
1995年 | 19篇 |
1994年 | 15篇 |
1993年 | 17篇 |
1992年 | 10篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 18篇 |
1988年 | 13篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 10篇 |
1975年 | 4篇 |
1974年 | 10篇 |
1973年 | 4篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1970年 | 3篇 |
1969年 | 5篇 |
排序方式: 共有721条查询结果,搜索用时 15 毫秒
81.
Investigated the role of practice tests in predictions about test performance on texts. Generally, Ss predicted their relative performance on tests accurately. However, answering practice-test questions that were drawn from the same pool as criterion-test questions did not improve prediction accuracy. The main reason for this was that practice-test scores for specific texts did not correlate with criterion-test scores. In addition, neither practice tests that were identical to the criterion tests nor practice tests consisting of the question stems improved the accuracy of test predictions relative to no-practice tests. With identical practice and criterion tests, accuracy of self-generated feedback correlated positively with the accuracy of test predictions. For similar practice and criterion tests, however, accurate experimenter-provided feedback reduced test-prediction accuracy, presumably because of the lack of reliability. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
82.
A synthesis method and an MOS VLSI architecture are presented to realize sequential circuits that have the ability to implement any state machine having N states and m inputs, regardless of the actual sequence specified in the flow table. The design method utilizes binary tree structured logic to implement regular and dense circuits. The desired state sequence can be hardwired with power supply connections or can be dynamically reallocated if stored in a register. This allows programmable VLSI controllers to be designed with a compact size and performance approaching that of dedicated logic. Results of ICV implementations are reported and an example sequence-invariant state machine is contrasted with implementations based on traditional methods 相似文献
83.
MH Davidson KC Maki J Kalkowski EJ Schaefer SA Torri KB Drennan 《Canadian Metallurgical Quarterly》1997,16(3):236-243
OBJECTIVE: The objective of this study was to evaluate the effects of daily dietary supplementation with 1.25 g or 2.5 g of docosahexaenoic (DHA), in the absence of eicosapentaenoic acid (EPA), on serum lipids and lipoproteins in persons with combined hyperlipidemia (CHL) [serum low-density lipoprotein cholesterol (LDL-C) 130 to 220 mg/dL and triglycerides 150 to 400 mg/dL]. METHODS: After a 6-week dietary stabilization period, subjects entered a 4-week single-blind placebo (vegetable oil) run-in phase. Those with adequate compliance during the the run-in were randomized into one of three parallel groups (placebo, 1.25, or 2.5 g/day DHA) for 6 weeks of treatment. Supplements were administered in a triglyceride form contained in gelatin capsules. Primary outcome measurements were plasma phospholipid DHA content, serum triglycerides, high-density lipoprotein cholesterol (HDL-C). LDL-C and non-HDL-C. RESULTS: The DHA content of plasma phospholipids increased dramatically (2 to 3 fold) in a dose-dependent manner. Significant (p < 0.05) changes were observed in serum triglycerides (17 to 21% reduction) and HDL-C (6% increase) which were of similar magnitude in both DHA groups. Non-HDL-C [+1.6 (NS) and +5.7% (p < 0.04)] and LDL-C [+9.3% (NS) and +13.6% (p < 0.001)] increased in the DHA treatment groups. All lipid effects reached an apparent steady state within the first 3 weeks of treatment. CONCLUSION: Dietary DHA, in the absence of EPA, can affect lipoprotein cholesterol and triglyceride levels in patients with combined hyperlipidemia. The desirable triglyceride and HDL-C changes were present at a dose which did not significantly increased non-HDL-C or LDL-C. These preliminary findings suggest that dietary supplementation with 1.25 g DHA/day, provided in a triglyceride form, may be an effective tool to aid in the management of hypertriglyceridemia. 相似文献
84.
Research was conducted with 240 undergraduates to determine the relationship between an observer's own value orientation and his/her ability to detect the value orientations of others. Choices in a series of 3-choice decomposed games were used to classify Ss as altruistic, cooperative, individualistic, or competitive in orientation. Subsequently, Ss observed a hypothetical person (the "chooser") select between self- and other-outcome alternatives in a series of 4-choice decomposed games. The chooser's behavior was preprogrammed in accordance with an altruistic, cooperative, individualistic, or competitive orientation. Results confirm that Ss' own values affected their relative abilities to predict the different choosers' behaviors. Cooperative and individualistic Ss demonstrated comparatively high levels of predictive accuracy regardless of the chooser's social value orientation, whereas altruistic and competitive Ss' predictive accuracy varied as a function of the chooser's orientation. Results for cooperative and competitive Ss resembled the "triangle" effect first observed by H. H. Kelley and A. J. Stahelski (1970). (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
85.
86.
87.
The fluctuation propagator for the superconducting order parameter belowT c is derived for a gapless superconductor. The fluctuation of the order parameter consists of two distinct modes: the fluctuations of the phase and the modulus of the order parameter. The former fluctuation obeys a phononlike dispersion, while the latter fluctuation is described by a damping diffusion type equation. The present theory gives an account of the fluctuation-induced Josephson effect belowT c observed recently by Carlson and Goldman. 相似文献
88.
89.
S Kurooka M Hashimoto M Tomita A Maki Y Yoshimura 《Canadian Metallurgical Quarterly》1976,79(3):533-541
About 100 S-fatty acyl thiol compounds designed as substrates for pancreatic lipase [EC 3.1.1.3] were synthesized and tested for susceptibility to hydrolysis by hog pancreatic lipase and hog hepatic carboxylic esterase [EC 3.1.1.1] using 5,5'-dithiobis(2-nitrobenzoic acid) as a chromogenic reagent to determine the hydrolytic rates of their S-acyl bonds. In general, the hydrolytic rates of S-acyl bonds by the lipase were fast with thioglycerol type thiol moieties, slow with dithioethyleneglycol type or monothiol type, and negligible with thiopolyol type. As for the acyl moieties, the hydrolysis of the S-acyl bonds was fast with C3-5 acyl groups, followed by C6-8 acyl groups, and the rate decreased as the acyl chain length deviated from these values or branched. On the other hand, the hydrolysis of S-acyl bonds by the esterase occurred with all types of S-acyl esters except for esters of long S-acyl chains. Of all the compounds tested with the lipase, the rate of hydrolysis of S-acyl bond was maximum with 2,3-dimercaptopropan-1-ol tributyroate [I], high with 3-mercaptopropane-1,2-diol tributyroate [II], but negligible with the analogous compound, 1,3-dimercaptopropan-2-ol tributyroate. Compounds [I] and [II] may be practically useful as substrates for lipase assay in human serum samples pretreated with phenylmethylsulfonyl fluoride, a potent inhibitor against both serum arylesterase [EC 3.1.1.2] and hepatic esterase, which attack [I] and [II]. 相似文献
90.
We study theoretically the ringing of magnetization in superfluid3He-B for two configurations: the ringing in the Leggett configuration in the presence of a transverse field and the longitudinal ringing in the parallel plate configuration. It is shown that the time variation of the magnetization is described in terms of three distinct ringing frequencies in these general configurations. 相似文献