全文获取类型
收费全文 | 20995篇 |
免费 | 2010篇 |
国内免费 | 1556篇 |
专业分类
电工技术 | 441篇 |
技术理论 | 3篇 |
综合类 | 1959篇 |
化学工业 | 4306篇 |
金属工艺 | 2059篇 |
机械仪表 | 590篇 |
建筑科学 | 3482篇 |
矿业工程 | 500篇 |
能源动力 | 395篇 |
轻工业 | 890篇 |
水利工程 | 249篇 |
石油天然气 | 481篇 |
武器工业 | 148篇 |
无线电 | 636篇 |
一般工业技术 | 2862篇 |
冶金工业 | 3040篇 |
原子能技术 | 178篇 |
自动化技术 | 2342篇 |
出版年
2024年 | 70篇 |
2023年 | 394篇 |
2022年 | 701篇 |
2021年 | 863篇 |
2020年 | 863篇 |
2019年 | 785篇 |
2018年 | 712篇 |
2017年 | 849篇 |
2016年 | 836篇 |
2015年 | 826篇 |
2014年 | 1091篇 |
2013年 | 1199篇 |
2012年 | 1289篇 |
2011年 | 1576篇 |
2010年 | 1222篇 |
2009年 | 1240篇 |
2008年 | 1152篇 |
2007年 | 1266篇 |
2006年 | 1125篇 |
2005年 | 1042篇 |
2004年 | 879篇 |
2003年 | 798篇 |
2002年 | 671篇 |
2001年 | 526篇 |
2000年 | 341篇 |
1999年 | 313篇 |
1998年 | 237篇 |
1997年 | 200篇 |
1996年 | 162篇 |
1995年 | 114篇 |
1994年 | 120篇 |
1993年 | 91篇 |
1992年 | 73篇 |
1991年 | 58篇 |
1990年 | 71篇 |
1989年 | 45篇 |
1988年 | 30篇 |
1987年 | 32篇 |
1986年 | 36篇 |
1984年 | 28篇 |
1980年 | 30篇 |
1979年 | 25篇 |
1966年 | 28篇 |
1965年 | 31篇 |
1964年 | 49篇 |
1963年 | 39篇 |
1960年 | 26篇 |
1959年 | 29篇 |
1958年 | 30篇 |
1955年 | 46篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Ibuprofen is a well-known nonsteroidal anti-inflammatory drug, which can interact with lipid membranes. In this paper, the interaction of ibuprofen with bilayer lipid membrane was studied by UV-vis spectroscopy, cyclic voltammetry and AC impedance spectroscopy. UV-vis spectroscopy data indicated directly that ibuprofen could interact with lipid vesicles. In electrochemical experiments, ibuprofen displayed a biphasic behavior on bilayer lipid membrane supported on a glassy carbon electrode. It could stabilize the lipid membrane in low concentration, while it induced defects formation, even removed off bilayer lipid membrane from the surface of the electrode with increasing concentration. The mechanism about the interaction between ibuprofen and supported bilayer lipid membrane was discussed. 相似文献
102.
DiPietro Janet A.; Caulfield Laura E.; Irizarry Rafael A.; Chen Ping; Merialdi Mario; Zavaleta Nelly 《Canadian Metallurgical Quarterly》2006,120(3):687
Fetal and maternal data were monitored serially at 6 gestational ages from 20 to 38 weeks in 195 Peruvian fetuses. Digitized data included fetal heart rate and motor activity, as well as maternal heart rate and electrodermal conductance. Time series analysis evaluated the development of synchrony in 2 streams of fetal functioning and between mothers and fetuses. Intrafetal synchrony between heart rate and motor activity developed in an orderly fashion, with peak cross-correlation approaching an asymptote at 5 s at 28 weeks. Synchrony was not observed between fetal heart rate and maternal measures. Fetal motor activity exhibited synchrony with both maternal electrodermal and heart rate activity. Implications for revealing fundamental properties of neural development prior to birth are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
103.
V. E. Kahle 《Journal of Failure Analysis and Prevention》2006,6(4):23-28
Three reconditioned rail car couplers, arbitrarily identified as couplers, failed during service due to cracking of the front
face. The three couplers were reportedly upgraded by quenching and tempering to enhance strength and toughness. The objective
of this investigation was to determine the mode of crack propagation and the root cause of the observed failures.
Verl E. (Bud) Kahle, P.E., was a professional failure analyst for more than forty years. After receiving his Bachelor of Science
degree in physical metallurgy from Washington State University 1957, Bud was employed by the General Electric Company at a
facility in Hanford, Washington. He later was employed by the Aerojet General Corporation and eventually was head of the Southern
Pacific Materials Science Laboratory in Sacramento. After retirement from Southern Pacific he owned and operated his own firm,
Kahle Metallurgical Consulting Services, for fifteen years. He came to be known as “the man with the answers” to clients in
a variety of industries. Bud was a Life Member of ASM International.
Many of Bud’s clients remarked on the high quality of his failure analysis case histories and encouraged him to have them
published. After Bud passed away in 1999, his wife, Suzanne, approached ASM International to see if the society would be interested
in publishing any of his work. Mrs. Kahle was able to supply a large number of reports, which Bud had carefully archived over
the years. Journal of Failure Analysis and Prevention Associate Editor Michael Stevenson read through the collected case histories, selected the ones to be included in this issue,
and edited them for journal publication.
ASM International wishes to thank Mrs. Kahle for providing these case histories for publication. 相似文献
104.
We performed the first-principles calculation to investigate the electronic structure and polarization behaviors in PbTiO3/SrTiO3 (PST) superlattices. The DOS (density of state) profiles show that there are strong hybridizations of atom Ti–O and Pb–O which play very important roles on ferroelectricity of the PbTiO3/SrTiO3 superlattices. Comparing to the corresponding paraelectric phase, we find the electrons of the PT (PbTiO3) layers occupy lower energy states and electrons of the ST (SrTiO3) layer occupy higher energy states. It is shown that the polarizations of the superlattices decrease with proportion of SrTiO3 increasing. The constant polarization of local layer indicates that PST superlattices with small modulation lengthen can be approximately considered as a single ferroelectric material. Furthermore, according to electrostatic model, we find that directions of internal electric fields in PT and ST layers are opposite. In PST superlattices, internal electric field in PT layer leads to the loss of polarization of this layer, but the polarization of ST layer is induced by internal electric field of this layer. Compared to the value of the polarization in bulk PbTiO3, polarization of PST is smaller. 相似文献
105.
Goodnight Jackson A.; Bates John E.; Staples Angela Dawn; Pettit Gregory S.; Dodge Kenneth A. 《Canadian Metallurgical Quarterly》2007,21(1):39
This study examined the moderating effects of temperamental resistance to control on the link between development of sleep problems and development of externalizing behaviors over a 5-year period. Resistance to control was assessed with mothers' retrospective reports of temperament in infancy, provided when children were 5 years of age. Sleep problems were assessed with mother reports on an annual basis from age 5 to age 9. Externalizing behaviors were assessed with teacher reports on an annual basis from age 5 to age 9. A cross-domain latent growth curve model indicated that sleep problem trajectories were positively associated with externalizing behavior trajectories only for children high in resistance to control. In addition, resistance to control was positively associated with initial (age 5) sleep problems and initial (age 5) externalizing behaviors. The authors speculate that the development of sleep problems promotes the development of behavior problems for resistant children, whose self-regulatory abilities are especially tenuous. Implications for prevention and treatment of conduct problems are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
106.
Rowan Paul J.; Cofta-Woerpel Ludmila; Mazas Carlos A.; Vidrine Jennifer Irvin; Reitzel Lorraine R.; Cinciripini Paul M.; Wetter David W. 《Canadian Metallurgical Quarterly》2007,15(4):382
Ecological momentary assessment (EMA) consists of assessing phenomena in real time in the natural environment. EMA allows for more fine-grained analyses of addictive behavior and minimizes threats to internal validity, such as recall biases and errors. However, because of the intensive monitoring involved in EMA, measurement reactivity is a concern. To test whether EMA with palmtop personal computers induces reactivity, the authors compared smoking-related outcomes between smokers using EMA and those not using EMA during a quit attempt. The use of no-EMA control groups has been rare in reactivity investigations to date. The EMA protocol included event-contingent assessments (smoking episodes, urge episodes) and random assessments. Outcomes included biologically confirmed abstinence and self-report measures of withdrawal, self-efficacy, motivation, affect, and temptations. Participants were smokers motivated to quit (N = 96). They were randomized to 1 of 3 groups: EMA for the week preceding a planned quit date, EMA for the week following the quit date, and no EMA. Abstinence rates did not differ between the groups at Day 7 or at Day 28 postcessation. For the 20 subscales assessed at each of 3 assessment times, there were significant differences between participants with and without EMA experience for 3 subscales at the 1st of 3 assessment times, and significant differences for 3 different subscales at the 3rd assessment time. These differences suggest some reactivity to EMA, although the inconsistent pattern across time indicates that further research is needed to definitively conclude that EMA induces reactivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
107.
Servin Anna; Nordenstr?m Anna; Larsson Agne; Bohlin Gunilla 《Canadian Metallurgical Quarterly》2003,39(3):440
Gender-typed behaviors and interests were investigated in 26 girls, aged 2-10 years, affected with congenital adrenal hyperplasia (CAH) and in 26 unaffected girls matched for age. Girls with CAH were more interested in masculine toys and less interested in feminine toys and were more likely to report having male playmates and to wish for masculine careers. Parents of girls with CAH rated their daughters' behaviors as more boylike than did parents of unaffected girls. A relation was found between disease severity and behavior indicating that more severely affected CAH girls were more interested in masculine toys and careers. No parental influence could be demonstrated on play behavior, nor did the comparison of parents' ratings of wished for behavior versus perceived behavior in their daughters indicate an effect of parental expectations. The results are interpreted as supporting a biological contribution to differences in play behavior between girls with and without CAH. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
108.
Stimulus control of ring swimming was studied with male Siamese fighting fish (Betta splendens) using 2-component multiple schedules in which the components were correlated with the presence or absence of air bubbles in the water. In Experiment 1, either response-independent mirror presentations or extinction was juxtaposed with immediate response-dependent mirror presentations. Rates of ring swimming generally were higher with immediate reinforcement than with either response-independent mirror presentations or extinction. In Experiment 2, different durations of response-dependent mirror presentations were juxtaposed. Generally, higher rates of ring swimming occurred with 15-s than with 0-, 1-, or 3-s durations. Results demonstrate that stimulus control of responding can be established with these fish under several conditions of differential reinforcement. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
109.
Cross Susan E.; Gore Jonathan S.; Morris Michael L. 《Canadian Metallurgical Quarterly》2003,85(5):933
Examination of the assumptions underlying consistency perspectives in social and personality psychology reveals that they are based on an independent, individualistic view of the self. If the self is constructed as relational or interdependent with others, consistency may be less important in social behavior and well-being. Using a variety of measures of well-being, the studies showed that there is a weaker relation between consistency and well-being for individuals with a highly relational self-construal than for those with a low relational self-construal. Study 3 examined the association between the self-construal, consistency, authenticity, and well-being. These findings reveal the importance of a cultural analysis of theories of the self, personality, and well-being for further theory development. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
110.
In this paper, one-dimensional compression behavior of uniformly graded fine sand is studied with the use of oedometer test
at elevated stress levels. To reach the elevated stress levels, testing is performed in a strain controlled manner. In addition,
standard stress controlled testing method is also used at lower stress levels for the purpose of comparison. Specimens prepared
with initial relative densities ranging from loose to dense are subjected to normal loading as well as hysteretic and repeated
loading patterns. Results showed that there is a linear relationship between compressibility index and relative density. The
magnitude of compression is mainly influenced by inundation where the compressibility behavior is found to be depending on
the initial formation density. Regardless of the initial formation density, convergence to a similar compression index is
observed with the hysteretically loaded samples whereas a continuous modification was obtained with repetitively loaded reformed
specimens. 相似文献