全文获取类型
收费全文 | 2779篇 |
免费 | 63篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 396篇 |
金属工艺 | 43篇 |
机械仪表 | 22篇 |
建筑科学 | 105篇 |
矿业工程 | 1篇 |
能源动力 | 36篇 |
轻工业 | 220篇 |
水利工程 | 22篇 |
石油天然气 | 5篇 |
武器工业 | 1篇 |
无线电 | 142篇 |
一般工业技术 | 307篇 |
冶金工业 | 1171篇 |
原子能技术 | 2篇 |
自动化技术 | 362篇 |
出版年
2022年 | 36篇 |
2021年 | 41篇 |
2020年 | 21篇 |
2019年 | 28篇 |
2018年 | 40篇 |
2017年 | 38篇 |
2016年 | 32篇 |
2015年 | 35篇 |
2014年 | 54篇 |
2013年 | 118篇 |
2012年 | 106篇 |
2011年 | 138篇 |
2010年 | 99篇 |
2009年 | 98篇 |
2008年 | 117篇 |
2007年 | 132篇 |
2006年 | 89篇 |
2005年 | 99篇 |
2004年 | 73篇 |
2003年 | 68篇 |
2002年 | 74篇 |
2001年 | 64篇 |
2000年 | 65篇 |
1999年 | 70篇 |
1998年 | 92篇 |
1997年 | 63篇 |
1996年 | 64篇 |
1995年 | 54篇 |
1994年 | 62篇 |
1993年 | 61篇 |
1992年 | 59篇 |
1991年 | 20篇 |
1990年 | 45篇 |
1989年 | 40篇 |
1988年 | 48篇 |
1987年 | 48篇 |
1986年 | 35篇 |
1985年 | 39篇 |
1984年 | 25篇 |
1983年 | 36篇 |
1982年 | 41篇 |
1981年 | 42篇 |
1980年 | 28篇 |
1979年 | 34篇 |
1978年 | 25篇 |
1977年 | 30篇 |
1976年 | 26篇 |
1975年 | 19篇 |
1974年 | 17篇 |
1973年 | 12篇 |
排序方式: 共有2844条查询结果,搜索用时 0 毫秒
1.
JM Rumsey BC Donohue DR Brady K Nace JN Giedd P Andreason 《Canadian Metallurgical Quarterly》1997,54(12):1481-1489
The influence of ionic strength and composition on the binding and inhibition of human leukocyte elastase by glycosaminoglycans with variable degree and position of sulfation was investigated. The kinetic mechanism of inhibition had a hyperbolic, mixed-type character with a competitive component that was promoted by low ionic strength, reduced by phosphate ions, and which also depended on the substrate and glycosaminoglycan structure. Enzyme binding was a cooperative phenomenon that varied with ionic strength and composition. The inhibition patterns correlated with the cationic character of elastase and with the distribution of arginines on its molecular surface, most notably with residues located in the vicinity of the substrate binding region. The order of affinity for elastase binding was chondroitin 4-sulfate < chondroitin 6-sulfate < dermatan sulfate, iduronate-containing derivatives being superior with respect to the glucuronate-containing counterparts. Additional sulfation at both the 4- and 6- positions or at the N- and 4-positions of the N-acetylgalactosamine moiety decidedly improved the inhibitory efficiency. The results highlight a fundamental physiological role of enzyme-glycosaminoglycan interactions. In the azurophil granule of the human polymorphonuclear neutrophil, elastase and other enzymes are bound to a matrix of chondroitin 4-sulfate because this is the only glycosaminoglycan that simultaneously offers good binding for enzyme compartmentalization together with prompt release from the bound state at the onset of phagocytosis. 相似文献
2.
The effects of circuit weight training on mood, perceived stress, job satisfaction, and physical symptoms were investigated in a sample of state law enforcement officers. 43 male officers who were not regularly exercising were assigned to either 4 mo of circuit weight training or a wait-list control condition. Four months of circuit weight training led to a significant increase in strength on cardiovascular fitness. Ss also demonstrated significant improvements in mood, including decreases in somatization, anxiety, depression, and hostility. Circuit weight training also resulted in a decrease in reports of physical symptoms and in improvements in job satisfaction. Results indicate that Ss who dropped out of the exercise training program evidenced significantly greater anxiety, depression, and hostility at pretreatment than Ss who completed the program. These findings suggest that circuit weight training programs may contribute to important psychological benefits. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
ST O'Sullivan GT McGreal A Lyons L Burke JG Geoghegan MP Brady 《Canadian Metallurgical Quarterly》1994,47(9):851-852
A case of histologically confirmed Paget's disease of the breast in a 72 year old man, without underlying breast carcinoma, is reported. This report raises questions about the pathogenesis of this condition and suggests that Paget's disease is an independent, intraepidermal carcinoma rather than a direct extension of intraductal carcinoma of the breast to the nipple and areola. 相似文献
4.
Norman F. Haard Nancy Kariel Gene Herzberg L. A. Woodrow Feltham Karl Winter 《Journal of the science of food and agriculture》1985,36(4):229-241
Fish silage was prepared from 96.5% offal obtained from Atlantic cod fillet processing and 3.5% (by wt) formic acid. The fish silage became an homogeneous liquid of low viscosity in 36–58 h at 20°C; however, the oil and protein components continued to be hydrolysed for several months. Addition of formaldehyde to fish silage (0.25 or 0.39% by wt) after liquefaction was complete, served to prevent continued protein hydrolysis and oxidative rancidity of the oil. It also decreased the development of ‘off-odours’, and the formation of total volatile bases. Fish silage was readily absorbed by hay at a ratio of 1.5 parts silage to 1.0 parts hay by weight; the product is referred to as ‘haylage’. Voluntary intake by wethers of ‘haylage’ prepared from de-oiled, formaldehyde-treated fish silage was better than for ‘haylage’ prepared from untreated fish silage. The crude protein content of ‘haylage’ rations was more than satisfactory for fattening lambs, although the energy content of ‘haylage’ rations may be a limiting factor. Retention of fish oil in the silage to increase the energy content of rations was unsuccessful because voluntary feed intake was depressed. The addition of formaldehyde to fish silage is advantageous when the product is to be fed to ruminant livestock since protein and lipid degradation in the feed, and also possibly in the rumen, are minimised and voluntary intake of ‘haylage’ by sheep is increased. 相似文献
5.
The rationale for utilizing filial therapy as a treatment intervention with child witnesses of domestic violence while residing with their mothers in a shelter facility is explored and the effectiveness of an intensive 12-session filial therapy parent training group, conducted within 2-3 weeks, is described (n=11; aged 4-10 yrs). Results of analysis of covariance revealed that child witnesses in the experimental group significantly reduced behavior problems prevalent in child witnesses and significantly increased their self-concept as compared to child witnesses in the non-treatment comparison group. In addition, t-test results showed that mothers who facilitated treatment of the experimental group scored significantly higher after training on both their attitudes of acceptance and their empathic behavior. Comparative analysis revealed that intensive filial therapy as facilitated by the children's mothers was as effective in reducing behavior problems as was intensive individual play therapy and intensive sibling group play therapy as facilitated by professionally trained therapists. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
6.
Docherty Nancy M.; Cohen Alex S.; Nienow Tasha M.; Dinzeo Thomas J.; Dangelmaier Ruth E. 《Canadian Metallurgical Quarterly》2003,112(3):469
This study examined the degree to which different types of communication disturbances in the speech of 48 schizophrenia patients and 28 controls were variable and state related versus stable and traitlike. Clinically rated formal thought disorder and 5 types of referential disturbance showed substantial stability within participants over time. The sixth type of referential disturbance, the vague reference, was not stable over time. Formal thought disorder was associated with the severity of core psychotic symptoms in patients, whereas referential disturbances showed little or no association with positive or negative symptom severity. Furthermore, changes in psychotic symptoms over time were accompanied by corresponding changes in formal thought disorder but not referential disturbances. These results support the idea that some types of referential disturbances are traitlike and may be reflective of vulnerability as well as manifest illness. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
7.
The year 1992 marks the centennial of the founding of the American Psychological Association (APA). Through the years, psychologists who were interested in animal behavior processes have actively participated in this organization, and many have been elected president of APA. This article considers some aspects of theory and research in animal psychology during this 100-yr period by examining a selected set of APA presidential addresses. Attention is given to the presidents' evaluations of the state of animal psychology at the time of their presidency and their assessments of its future. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
8.
Bouchard Thomas J.; Arvey Richard D.; Keller Lauren M.; Segal Nancy L. 《Canadian Metallurgical Quarterly》1992,77(1):89
Responds to the points made by R. Cropanzano and K. James (see record 1991-00462-001) concerning the article by R. D. Arvey et al (1989). The authors acknowledge that the Arvey et al study is based on a single design, makes use of a small and special sample, and, as such, is vulnerable to threats of internal and external validity. Nevertheless, after providing a more comprehensive conceptual and empirical context for the study, and after reviewing a number of the issues raised by Cropanzano and James, the authors conclude that it is not premature to accept the idea that work attitudes are partially genetically influenced. Indeed, the authors use behavioral genetic theory, together with data gathered in the Arvey et al study, to make specific point predictions regarding the outcomes of an array of studies that easily can be undertaken. Finally, the authors acknowledge that the comments and issues raised by Cropanzano and James, along with the interchange, can offer directions for future research in this important area. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
9.
Michael Brady 《Energy》1985,10(10):1113-1118
Current energy policies have severely eroded the earth's natural atmospheric waste-receptor capacity. Present acid rain concentrations may require a switch to an alternative energy-resource emphasis. This policy recommendation follows directly from a deductive control theory demonstration which shows that, if fossil-fuel use is continued at present rates, then there is an ever-increasing risk of a man-made environmental crisis of uncertain nature and scope. 相似文献
10.
The extraction of nitrogenous material from Brewers' spent grain (BSG) by solvents (water, sodium chloride solution, aqueous alcohol, acidic and alkaline solutions) commonly used to extract cereal proteins, resulted in the relatively low (0·2 to 8·5%) recovery of the total nitrogen. The recovery of nitrogenous material by the use of aqueous alkaline solutions was increased from 3–4% to 41% when the BSG was subjected to cellulase incubation prior to extraction. Approximately 75% of the nitrogen was solubilized with trifluoracetic acid. Detergent solutions (acid, neutral) solubilized more than 80% of the total nitrogen of the BSG. The low solubility of the nitrogenous constituents by conventional protein solvents could be the result of association between cellulosic material and protein. 相似文献