全文获取类型
收费全文 | 961篇 |
免费 | 1篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 15篇 |
金属工艺 | 3篇 |
机械仪表 | 2篇 |
建筑科学 | 5篇 |
能源动力 | 5篇 |
轻工业 | 10篇 |
水利工程 | 2篇 |
无线电 | 33篇 |
一般工业技术 | 19篇 |
冶金工业 | 830篇 |
原子能技术 | 1篇 |
自动化技术 | 32篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 2篇 |
2017年 | 2篇 |
2014年 | 2篇 |
2013年 | 6篇 |
2012年 | 7篇 |
2011年 | 10篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 14篇 |
2006年 | 4篇 |
2005年 | 12篇 |
2004年 | 8篇 |
2003年 | 4篇 |
2002年 | 3篇 |
2001年 | 8篇 |
2000年 | 3篇 |
1999年 | 39篇 |
1998年 | 250篇 |
1997年 | 130篇 |
1996年 | 110篇 |
1995年 | 45篇 |
1994年 | 49篇 |
1993年 | 45篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 12篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 24篇 |
1976年 | 45篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1968年 | 2篇 |
排序方式: 共有962条查询结果,搜索用时 15 毫秒
51.
Ackerman Brian P.; D'Eramo Kristen Schoff; Umylny Lina; Schultz David; Izard Carroll E. 《Canadian Metallurgical Quarterly》2001,15(2):288
This study examined the relations among family structure, caregiver relationship history, aspects of environmental adversity, and teacher reports about the externalizing behaviors of 6- and 7-year-old children from economically disadvantaged families. Family structure contrasted intact families, stepfamilies, single-parent families, and cohabiting families. Problem behaviors were more frequent for children from unmarried families than from married families and were more frequent for boys than for girls from cohabiting families. Relationship history reduced the effects for family structure. Children's adjustment varied with both the current status and past stability of caregiver intimate relationships for disadvantaged families. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
52.
The authors describe an interface system called Athena Muse. Muse is an experiment kit for the construction of multimedia learning environments. Learning environments developed with Muse offer a diverse set of complementary interaction techniques, styles, and devices. An interface developer can choose from four representation approaches: directed graphs, multidimensional spatial frameworks, declarative constraints, and procedural languages 相似文献
53.
IAPs comprise a family of inhibitors of apoptosis found in viruses and animals. In vivo binding studies demonstrated that both baculovirus and Drosophila IAPs physically interact with an apoptosis-inducing protein of Drosophila, Reaper (RPR), through their baculovirus IAP repeat (BIR) region. Expression of IAPs blocked RPR-induced apoptosis and resulted in the accumulation of RPR in punctate perinuclear locations which coincided with IAP localization. When expressed alone, RPR rapidly disappeared from the cells undergoing RPR-induced apoptosis. Expression of P35, a caspase inhibitor, also blocked RPR-induced apoptosis and delayed RPR decline, but RPR remained cytoplasmic in its location. Mutational analysis of RPR demonstrated that caspases were not directly responsible for RPR disappearance. The physical interaction of IAPs with RPR provides a molecular mechanism for IAP inhibition of RPR's apoptotic activity. 相似文献
54.
Increasing the contrast of just one eye's image degrades stereothresholds; this phenomenon is referred to as the stereo contrast paradox. In experiment one, this paradox was found to be absent in dynamic random-element stereograms; thresholds were simply limited by the lower of the two eyes' contrasts. In experiment two, in which narrowband Gabor targets were used, the paradox was found to be strongest at relatively low spatial frequencies (1 cycle deg-1). As spatial frequency was increased, the paradox gradually disappeared. At relatively high spatial frequencies (5 cycles deg-1), thresholds were generally limited by the lower of the two eyes' contrasts, as was found for the dynamic noise targets. These results demonstrate the interactions of spatial frequency and contrast in binocular image combination and yield clues as to the different roles which high and low spatial frequencies may play in stereopsis. 相似文献
55.
The “Overvoltage Measurements” field study was undertaken with the aim of establishing regulatory measures based on information from metered transient overvoltages occurring in low-voltage networks, installations, and telecommunication lines. Some 40 companies and institutions from industry and the power-utility, insurance, telecommunications, and research sectors contributed to the study. The overvoltages occurring between phase conductors and protective conductors were also measured 相似文献
56.
Common ground is contextual information shared by a listener and speaker that enables the listener to convert an ambiguous utterance to an informative communication. Four experiments examined young children's understanding of the common ground in interpreting ambiguous referential utterances. Kindergarten and 2nd-grade children and college students were read short vignettes containing statement, joint activity, status common ground, and an ambiguous or informative utterance about a display of 4–6 object drawings. The subjects were asked (a) whether the listener knew which object to pick (Experiment 1), (b) to pick an object themselves or choose "none" (Experiment 2), (c) the source of the listener's knowledge in the context or utterance (Experiment 3), and (d) whether a designated object was the "right one," the one the speaker "meant," or the one the speaker "could have meant" (Experiment 4). Even the kindergarten children used statement information effectively in interpreting ambiguous utterances, and all groups had difficulty using status information. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
57.
Ackerman Brian P.; Schoff Kristen; Levinson Karen; Youngstrom Eric; Izard Carroll E. 《Canadian Metallurgical Quarterly》1999,35(6):1355
This study examined the relations between alternative explanations of poverty cofactors and promotion processes and teacher reports of the problem behaviors of 6- and 7-yr old children from economically disadvantaged families (N?=?159). The results showed that single index representations of risk and promotion variables predicted child aggressive behaviors but not child anxious/depressed behaviors. An addictive model of individual risk indicators performed similarly. Similar indexes representing clusters of parent adjustment variables and family instability variables, however, differentially predicted aggressive and anxious/depressed behaviors, respectively. The results suggest the importance of promotion processes and representing environmental adversity at varying levels of specificity for children from economically disadvantaged families. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
58.
59.
RAD52 and RAD9 are required for the repair of double-strand breaks (DSBs) induced by physical and chemical DNA-damaging agents in Saccharomyces cerevisiae. Analysis of EcoRI endonuclease expression in vivo revealed that, in contrast to DSBs containing damaged or modified termini, chromosomal DSBs retaining complementary ends could be repaired in rad52 mutants and in G1-phase Rad+ cells. Continuous EcoRI-induced scission of chromosomal DNA blocked the growth of rad52 mutants, with most cells arrested in G2 phase. Surprisingly, rad52 mutants were not more sensitive to EcoRI-induced cell killing than wild-type strains. In contrast, endonuclease expression was lethal in cells deficient in Ku-mediated end joining. Checkpoint-defective rad9 mutants did not arrest cell cycling and lost viability rapidly when EcoRI was expressed. Synthesis of the endonuclease produced extensive breakage of nuclear DNA and stimulated interchromosomal recombination. These results and those of additional experiments indicate that cohesive ended DSBs in chromosomal DNA can be accurately repaired by RAD52-mediated recombination and by recombination-independent complementary end joining in yeast cells. 相似文献
60.
This study elucidates the role of combined fluconazole and flucytosine as therapy for cryptococcosis in the murine model of meningitis. Three strains of Cryptococcus neoformans for which the range of fluconazole MICs was wide--2 microg/ml (susceptible strain), 8 microg/ml (moderately susceptible strain), and 32 microg/ml (resistant strain)--were used for infection. One day postinfection, the mice were randomized into eight treatment groups: placebo; flucytosine (40 mg/kg of body weight/day); fluconazole at 3 mg/kg/day (low dosage), 10 mg/kg/day (moderate dosage), or 20 mg/kg/day (high dosage); and combined flucytosine and fluconazole at low, moderate, or high doses of fluconazole. Three major findings were demonstrated: (i) correlation between the MICs for the isolates and the in vivo effectiveness of fluconazole as assessed by the reduction in cryptococcal brain burden, (ii) a dose-response curve (a higher dose of fluconazole was significantly more efficacious than a lower dose [P < 0.001]), and (iii) synergism between fluconazole and flucytosine (therapy with a combination of fluconazole and flucytosine was superior to therapy with either agent alone [P < 0.01]). 相似文献