全文获取类型
收费全文 | 2740篇 |
免费 | 86篇 |
专业分类
电工技术 | 39篇 |
综合类 | 8篇 |
化学工业 | 400篇 |
金属工艺 | 48篇 |
机械仪表 | 48篇 |
建筑科学 | 132篇 |
矿业工程 | 3篇 |
能源动力 | 68篇 |
轻工业 | 319篇 |
水利工程 | 12篇 |
石油天然气 | 6篇 |
无线电 | 168篇 |
一般工业技术 | 397篇 |
冶金工业 | 842篇 |
原子能技术 | 15篇 |
自动化技术 | 321篇 |
出版年
2023年 | 18篇 |
2022年 | 32篇 |
2021年 | 62篇 |
2020年 | 29篇 |
2019年 | 48篇 |
2018年 | 41篇 |
2017年 | 38篇 |
2016年 | 38篇 |
2015年 | 51篇 |
2014年 | 54篇 |
2013年 | 114篇 |
2012年 | 96篇 |
2011年 | 146篇 |
2010年 | 111篇 |
2009年 | 100篇 |
2008年 | 111篇 |
2007年 | 87篇 |
2006年 | 95篇 |
2005年 | 77篇 |
2004年 | 79篇 |
2003年 | 71篇 |
2002年 | 65篇 |
2001年 | 60篇 |
2000年 | 55篇 |
1999年 | 59篇 |
1998年 | 153篇 |
1997年 | 78篇 |
1996年 | 85篇 |
1995年 | 60篇 |
1994年 | 51篇 |
1993年 | 52篇 |
1992年 | 24篇 |
1991年 | 36篇 |
1990年 | 34篇 |
1989年 | 40篇 |
1988年 | 34篇 |
1987年 | 31篇 |
1986年 | 30篇 |
1985年 | 28篇 |
1984年 | 35篇 |
1983年 | 27篇 |
1982年 | 33篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1979年 | 19篇 |
1978年 | 15篇 |
1977年 | 31篇 |
1976年 | 48篇 |
1975年 | 15篇 |
1972年 | 11篇 |
排序方式: 共有2826条查询结果,搜索用时 703 毫秒
991.
Oaksford Mike; Morris Frances; Grainger Becki; Williams J. Mark G. 《Canadian Metallurgical Quarterly》1996,22(2):476
How positive induced mood states affect reasoning was investigated in three experiments. In Experiment 1, consistent with resource allocation theory (H. C. Ellis & P. W. Ashbrook, 1987), both positive and negative mood suppressed performance on a deontic version of Wason's selection task (P. W. Cheng & K. J. Holyoak, 1985)—participants confirmed where they normally falsify. Experiment 2 revealed the same confirmatory responses for participants performing a concurrent distracter task, indicating that induced mood states suppress reasoning by depleting central executive resources. This hypothesis was directly tested in Experiment 3. Participants in a positive, but not in a negative, mood state showed suppressed performance on the Tower of London task (T. Shallice, 1982)—the classical central executive task. The robust positive mood effects and the confirmation effects are discussed in terms of the D. A. Norman and T. Shallice (1986) model of central executive function and recent accounts of selection task performance (L. Cosmides, 1989; K. I. Manktelow & D. E. Over, 1991; M. Oaksford & N. Chater, 1994). (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
992.
Prewett-Livingston Amelia J.; Feild Hubert S.; Veres John G. III; Lewis Philip M. 《Canadian Metallurgical Quarterly》1996,81(2):178
This study investigated the effects of interviewer race, candidate race, and racial composition of interview panels on interview ratings. Data were collected on 153 police officers applying for promotion. Results confirmed a same-race rating effect (i.e., candidates racially similar to interviewers received higher ratings) for Black and White interviewers on racially balanced panels. A majority-race rating effect (i.e., candidates racially similar to the majority race of panel interviewers received higher ratings) existed for Black and White interviewers on primarily White panels. Rating patterns of Black and White interviewers on primarily Black panels also suggested a majority-race rating effect. Racial composition of selection interview panels in combination with interviewer and candidate race were proposed as variables affecting candidates' ratings. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
993.
A key claim of current theoretical analyses of the memory impairments associated with amnesia is that certain distinct forms of learning and memory are spared. A compelling example is that amnesic patients and controls are indistinguishable in repetition priming but amnesic patients are impaired at recognizing the study items. The authors show that this pattern of results is predicted by a single-system connectionist model of learning in which amnesia is simulated by a reduced learning rate. They also demonstrate that the model can reproduce the converse pattern in which priming but not recognition is impaired if the input is assumed to be additionally degraded in a priming test. The authors conclude that dissociations between priming and recognition do not require functionally or neurally distinct memory systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
994.
Chronic sinusitis is a recurrent disorder commonly found in atopic individuals, yet few studies have explored the role of inflammatory mediators in sinusitis. Sinus lavage fluid from ten patients with chronic sinusitis obtained during endoscopic surgery was analyzed for total cell counts and then assayed for histamine, immunoreactive leukotriene C4/D4/E4 (LTC4/D4/E4), and prostaglandin D2 (PGD2). All ten patients had been unresponsive to medical treatment, including oral corticosteroids in most cases. High concentrations of histamine, LTC4/D4/E4 and PGD2 were found in sinus fluid and were comparable to levels seen in nasal secretions of allergic rhinitis patients following allergen challenge. In the sinus fluid, inflammatory cells were predominantly neutrophils with only low percentages of mast cells, basophils or eosinophils. On the basis of the histamine and PGD2 concentrations in sinus fluid, we conclude that mast cell/basophil activation does occur in chronic sinusitis and may contribute to the persistent inflammation present in sinusitis. 相似文献
995.
Bile acid synthesis can be measured as release of14CO2 from [26-14C]cholesterol divided by cholesterol specific activity, but this method has not been validated in human subjects. We made
twelve comparisons of this CO2 method to standard isotope dilution in six normal subjects and found a mean discrepancy of 6%. Linear regression analysis
of one value with respect to the other revealed a correlation coefficient of 0.83 (P<0.001), a Y-intercept close to zero (−4.98)
and a slope close to 1 (1.06), suggesting good correspondence between the two methods. To assess the potential for error arising
from use of serum cholesterol to estimate specific activity of cholesterol used for bile acid synthesis, we compared synthesis
measured using serum free cholesterol specific activity to that measured using bile cholesterol specific activity, which is
known to be near isotopic equilibrium with the precursor pool used for bile acid synthesis. Synthesis calculated in these
two ways differed by less than 10%. The data indicate that the CO2 method using either serum or bile cholesterol specific activity provides a valid estimate of bile acid synthesis in man. 相似文献
996.
Alberto Castro-Muiz Amelia Martínez-Alonso Juan M.D. Tascn 《Microporous and mesoporous materials》2008,114(1-3):185-192
Isothermal treatments of the polyaramid fiber, [poly(p-phenylene terephthalamide)] (PPTA) in an inert atmosphere below its decomposition temperature are known to induce an important increase in char yield and modify the chemical composition and some other properties of the resulting chars. The objective of this work was to study the effect of this isothermal stage on the porous texture of chars and activated carbon fibers (ACFs) produced from PPTA. To this end, chars and ACFs were prepared by PPTA pyrolysis to 850 °C followed by CO2 activation at 800 °C to various burn-offs (BOs), introducing or not an intermediate isothermal pre-treatment under the conditions (500 °C, 200 min) known to lead to a maximum increase in char yield. The porosity characteristics of the resulting chars and ACFs were comparatively investigated by adsorption of CO2 (0 °C), and N2 (−196 °C). The isothermal stage led to a char with enhanced micropore volume and wider micropores. The ACFs prepared from this char exhibited larger amounts of wide micropores and mesopores than those prepared from PPTA pyrolyzed at a constant heating rate. 相似文献
997.
Garza-Meilandt Annette; Cantu Rebecca E.; Claiborne Brenda J. 《Canadian Metallurgical Quarterly》2006,120(4):905
Estrogen's effects on performance and neuronal morphology are variable, and the reasons for this variability are not yet understood. In this study, the authors compared the effects of 2 delivery routes of 17 β-estradiol on spatial learning and dendritic spine densities in young ovariectomized rats; estradiol was administered by implanted capsules or by daily oral gavage. Estradiol treatment via capsules improved performance in the radial-arm water maze and increased spine densities on dendrites of CA1 pyramidal neurons in the hippocampal formation. In contrast, daily oral administration of estradiol did not affect either measure. These data demonstrate that estradiol delivery is a critical variable in animal studies and that clinical studies comparing the effects of different estradiol treatment routes on cognition are warranted. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
998.
999.
Evaluation and treatment of changes in mood, sleep, and sexual functioning associated with menopause
Most women will not have significant psychological, sleep, or sexual disturbances during the transition from menstrual to menopausal life. Evaluation of these symptoms requires careful consideration of menopausal status, preexisting difficulties, and complicating medical or interpersonal problems. Hormone replacement therapy may be a useful treatment either alone or as an adjunct to other somatic, behavioral, or psychological interventions. 相似文献
1000.