全文获取类型
收费全文 | 12580篇 |
免费 | 1341篇 |
国内免费 | 745篇 |
专业分类
电工技术 | 378篇 |
技术理论 | 2篇 |
综合类 | 1447篇 |
化学工业 | 1844篇 |
金属工艺 | 257篇 |
机械仪表 | 559篇 |
建筑科学 | 1438篇 |
矿业工程 | 183篇 |
能源动力 | 126篇 |
轻工业 | 2250篇 |
水利工程 | 316篇 |
石油天然气 | 256篇 |
武器工业 | 53篇 |
无线电 | 906篇 |
一般工业技术 | 1090篇 |
冶金工业 | 980篇 |
原子能技术 | 129篇 |
自动化技术 | 2452篇 |
出版年
2024年 | 67篇 |
2023年 | 244篇 |
2022年 | 681篇 |
2021年 | 760篇 |
2020年 | 484篇 |
2019年 | 445篇 |
2018年 | 418篇 |
2017年 | 500篇 |
2016年 | 464篇 |
2015年 | 532篇 |
2014年 | 708篇 |
2013年 | 801篇 |
2012年 | 805篇 |
2011年 | 795篇 |
2010年 | 721篇 |
2009年 | 621篇 |
2008年 | 667篇 |
2007年 | 747篇 |
2006年 | 726篇 |
2005年 | 652篇 |
2004年 | 484篇 |
2003年 | 409篇 |
2002年 | 298篇 |
2001年 | 254篇 |
2000年 | 182篇 |
1999年 | 147篇 |
1998年 | 108篇 |
1997年 | 96篇 |
1996年 | 83篇 |
1995年 | 54篇 |
1994年 | 70篇 |
1993年 | 56篇 |
1992年 | 44篇 |
1991年 | 40篇 |
1990年 | 40篇 |
1989年 | 26篇 |
1988年 | 29篇 |
1987年 | 22篇 |
1986年 | 27篇 |
1985年 | 32篇 |
1984年 | 28篇 |
1983年 | 32篇 |
1982年 | 22篇 |
1981年 | 22篇 |
1979年 | 18篇 |
1964年 | 15篇 |
1960年 | 12篇 |
1957年 | 20篇 |
1956年 | 11篇 |
1955年 | 25篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
P. Powell 《Information Systems Journal》1992,2(4):269-280
Abstract. Expert systems proliferate. They are now a usable and used tool in a variety of organizations. However, little research has been undertaken on the quantification of success or failure of expert system projects. By and large the only test carried out for expert system validation is one of comparison of the conclusions of the system with those of an expert or team of experts. While questioning the validity, this paper accepts that this method is being used and analyses whether or not the results obtained from this type of test should be a surprise. That is, what sort of results should be expected and to what extent do the reported ones live up to these expectations? Earlier research from the field of human information processing casts doubts on the success claims made for current expert systems. The implications of this research are then analysed in order to explore the possible redeeming features of expert systems which are not taken into account in such comparisons. The use of linear models as comparators for expert systems may prove beneficial. 相似文献
12.
J. HADGRAFT 《International journal of cosmetic science》1985,7(3):103-115
The skin comes into contact with a large range of materials either deliberately or inadvertently. It should be possible to predict the exact transport rates of these materials through the skin as a function of the physicochemical properties of the different compounds. With this sort of knowledge it is possible to predict the exact disposition of compounds and use this in the formulation of new products both in the pharmaceutical and cosmetic field. The information will also be useful from the standpoint of skin toxicology and environmental health. In order to be able to predict this complex process it is necessary to split the overall transport into different component parts. This article will identify these components and provide illustrations. The major areas discussed will be barrier function of the skin, the release properties of different topical formulations and how these may be monitored. Novel means of enhancing the penetration of drugs will be discussed and how some additives that are incorporated into formulations will perhaps alter the barrier function of skin. A mathematical model describing skin penetration has been developed and its use in predicting blood levels will be described. This model has been tested both in animal experiments and in limited human studies and its relevance to these situations will be highlighted.
Absorption cutanée et transcutanée in vivo 相似文献
Absorption cutanée et transcutanée in vivo 相似文献
13.
14.
Reviews the book, The mind's we: Contextualism in cognitive psychology by Diane Gillespie (1992). In this text the author has both expanded on several of the key insights previously outlined in the critical literature and provided a congenial introductory text for the newcomer; a text to serve as a conceptual bridge between traditional cognitive psychological approaches and their newly emergent contextualist alternatives. As stated in her preface, Gillespie's purpose in preparing this book was to "bring together the work of psychologists who are interested in telling the contextualist story of cognition" and to "reveal and strengthen their insights and perspectives" (p. xiv). Given the philosophical range and theoretical diversity of those interested in telling such a story, the task is certainly a formidable one, but it is nonetheless one that she accomplishes with a commendable degree of elegance. Gillespie clearly articulates the diverse work of a large number of psychological theorists into a coherent and meaningful account that will do much toward imposing order on a field that is, by its very nature, somewhat scattered and contentious. Each of the book's six chapters proceeds carefully through a detailed and representative historical and conceptual analysis of traditional mechanistic approaches to human cognition prior to advancing their contextualist critiques and alternatives. Through a systematic analysis of the manner in which this "contextualist story" has arisen within the mechanistic milieu of traditional scientific psychology, she is able to clarify both the implications and relative merits and liabilities of two, quite often antithetical, conceptualizations of human cognitive phenomena. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
15.
No authorship indicated 《Canadian Metallurgical Quarterly》2006,61(8):811
Presents the citation for Anthony D. Wagner, who received the Award for Distinguished Scientific Early Career Contributions to Psychology (cognition and human learning) "for outstanding and innovative research on the neural basis of memory and executive control." A brief profile and a selected bibliography accompany the citation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
16.
人类聚居环境学对于居住区规划设计的启示 总被引:1,自引:0,他引:1
以人类聚居环境学的研究方法从若干方面对目前的居住区规划设计进行了一定的探讨,分析规划设计及建设方面目前存在的主要问题,提出以人类聚居环境学为指导的居住区规划设计理念。 相似文献
17.
Monodisperse poly(vinyl acetate) (PVAc) microspheres with high molecular weight obtained by suspension polymerization of vinyl acetate were saponified in alkaline aqueous solution to keep their spherical structure. The saponification was restricted on the surface of the PVAc microspheres and obtained particles had skin/core structure. Various poly(vinyl alcohol) (PVA) microspheres with different diameters and degrees of saponification (DSs) were obtained. The conversion of PVAc to PVA during the heterogeneous surface saponification time were examined by nuclear magnetic resonance spectroscopy and after 72 h hydrogel type PVA microspheres completely saponified were obtained. The crystal melting temperatures of the microspheres obtained by the saponification were measured a constant value of 238°C irrespective of varying DS, and the peaks became enlarged as reaction time. Iodine complexes were formed in saponified microspheres with DS of 41% and 99% by immersing them in I2/KI aqueous solution and decomposed by the reduction of I2 in the complexes to 2I? using sodium sulfite to confirm whether the skin formed through the saponification was composed of PVA with high VA content. Obviously, characteristic blue color developments owing to I5?‐PVA complexes were observed in both saponified regions and a red in the PVAc core. Consequently, it was concluded that the PVA skins formed by heterogeneous surface saponification had high DSs. Such complexes endowed polymeric microspheres a good radiopacity which would be useful in clinical treatment of vascular diseases and were examined by X‐ray irradiation image. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
18.
Liew Jeffrey; Eisenberg Nancy; Losoya Sandra H.; Fabes Richard A.; Guthrie Ivanna K.; Murphy Bridget C. 《Canadian Metallurgical Quarterly》2003,17(4):584
Relations of heart rate and skin conductance reactions to mildly evocative empathy-inducing slides with socioemotional functioning were examined for 154 children (mean age = 9 years, 5 months). In addition, maternal expressivity was tested as a moderator of these relations. Parents and teachers rated children's socioemotional functioning, and a behavioral measure of children's regulation was obtained. Boys who exhibited higher skin conductance and higher heart rate to slides depicting negative emotions were better regulated, less emotionally intense, and better adjusted than their peers. Furthermore, boys' regulation and adjustment were positively related to such physiological responding to negative slides if maternal negative expressivity was relatively low or moderate, but not high. Fewer findings were obtained for girls or for positive slides. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
19.
20.
Six misconceptions about evolutionary approaches to human behavior are exposed. Evidence is adduced to support the assertions that evolutionary approaches do not (a) adopt a reductionistic "gene-centered" level of analysis, (b) assume that natural selection is the only process that creates and designs ontogenetic processes and phenotypic outcomes, (c) assume that genes are the only agents responsible for the transgenerational inheritance of phenotypic traits and characteristics, (d) assume that genes are self-contained and impervious to extragenetic influences, (e) posit a strong form of genetic determinism, or (f) pay lip service to the role of the environment. Building straw men and knocking them down is an inherently destructive enterprise; integrating different approaches is a more constructive way of contributing to the growth of knowledge. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献