首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   4569篇
  免费   124篇
  国内免费   3篇
电工技术   46篇
综合类   4篇
化学工业   1055篇
金属工艺   84篇
机械仪表   77篇
建筑科学   156篇
矿业工程   17篇
能源动力   126篇
轻工业   339篇
水利工程   66篇
石油天然气   19篇
无线电   233篇
一般工业技术   750篇
冶金工业   1153篇
原子能技术   30篇
自动化技术   541篇
  2021年   70篇
  2020年   42篇
  2019年   53篇
  2018年   63篇
  2017年   70篇
  2016年   72篇
  2015年   63篇
  2014年   102篇
  2013年   264篇
  2012年   137篇
  2011年   214篇
  2010年   189篇
  2009年   166篇
  2008年   192篇
  2007年   176篇
  2006年   187篇
  2005年   155篇
  2004年   139篇
  2003年   142篇
  2002年   113篇
  2001年   86篇
  2000年   84篇
  1999年   87篇
  1998年   118篇
  1997年   103篇
  1996年   97篇
  1995年   94篇
  1994年   98篇
  1993年   83篇
  1992年   89篇
  1991年   43篇
  1990年   65篇
  1989年   58篇
  1988年   59篇
  1987年   50篇
  1986年   52篇
  1985年   82篇
  1984年   77篇
  1983年   65篇
  1982年   51篇
  1981年   46篇
  1980年   38篇
  1979年   50篇
  1978年   51篇
  1977年   39篇
  1976年   45篇
  1975年   33篇
  1974年   36篇
  1973年   27篇
  1972年   29篇
排序方式: 共有4696条查询结果,搜索用时 0 毫秒
991.
The relations between infant attractiveness and maternal behavior were examined by observing mothers feeding and playing with their firstborn infants while they were still in the hospital after giving birth (N?=?144) and again when the infants were 3 months of age (N?=?115). The attitudes of the mothers toward their infants were also assessed. Mothers of more attractive infants were more affectionate and playful compared with mothers of less attractive infants. In contrast, the mothers of less attractive infants were more likely to be attentive to other people rather than to their infant and to engage in routine caregiving rather than affectionate behavior. The attitudes of the mothers of less attractive infants were also more negative than those of mothers of more attractive infants, but the number of differences in attitudes was not as great as the behavioral differences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
992.
Using steady-state simulation, we have evaluated the effect of boiler superheat and reheat temperatures on the economics of the utility section of a Bayer Alumina Plant. These economics were compared with those of a steam plant which purchased power. Under this study's nominal economic conditions, producing steam and purchasing electricity was the cheaper option. A sensitivity analysis showed that the cogeneration plant became the better choice when the local cost of electricity rose above 10C/kWh. The plant economics improved monotonically with superheat temperature as did the thermo-dynamic efficiency. However, for reheat, the plant economics did not improve monotonically with temperature even though the thermodynamic eficiency did; thus improvement in the thermodynamic efficiency does not always yield improved economics.  相似文献   
993.
This study examined effects of reward and response costs on the ability of 19 attention-deficit hyperactivity disorder (ADHD) and 17 control children to inhibit responding. Children were tested under 4 reinforcement conditions on a go/no-go learning task developed by J. P. Newman, C. S. Widom, and S. Nathan (1985). Two conditions involved both reward and response costs, 1 response costs only, and 1 reward only. ADHD children made more commission errors than controls across the 4 conditions. Analyses of learning curves indicated that group differences became larger on later trials. Thus, impaired inhibition was more generalized in ADHD children than in the psychopaths and extraverts studied by Newman and colleagues, and it became most evident when the children were required to improve learning across trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
994.
Optical fluorescence has an extensive history of application in the laboratory to the measurement of ionic concentrations and the partial pressures of oxygen and carbon dioxide. The use of optical fluorescence based sensors to fulfill a recognized need for continuous invasive monitoring of arterial blood gases offers a number of inherent advantages. However, the requirements placed upon a blood gas probe and supporting instrumentation appropriate for use in the clinical environment result in significant design challenges in selection of suitable fluorescent dyes, maintenance of mechanical integrity while obtaining required miniaturization of sensors, and in the transmission, acquisition, and processing of low level light signals. An optical fluorescence based intravascular blood gas monitoring system has been developed which is particularly suited for the critical care and surgical settings and which has a sensor probe that can be introduced into the patient via a radial artery catheter. This system has shown an excellent agreement of measured with true values of pH, pCO2, and P02 in both in vitro and animal studies. Linear regression analysis of typical in vitro data, where true levels were established via tonometry and standardization to a high accuracy laboratory pH measuring instrument, shows slope/intercept values very close to 1.0/0.0 and correlation coefficients of greater than 0.99 for all three parameters.  相似文献   
995.
Used the individual differences scaling model of multidimensional scaling to explore the dimensions of thermal pain. 20 male undergraduates made 66 similarity judgments to all pairs of 12 different thermal stimulus intensities ranging from zero to noxious. Results reveal a 2-dimensional group stimulus space. The major dimension ordered the stimuli with respect to their intensity. This quantitative, strength-of-sensation dimension may be interpreted as indicating how weak or strong a stimulus feels, apart from any secondary qualities of warmth or pain. The 2nd dimension was related to the qualitative aspects of the stimuli and contained 2 attributes: (1) a pain attribute ranging from just detectable warmth to painful and (2) a warm–hot attribute running from just detectable warmth to hot. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
996.
Perceptions of marital interactions were gathered from a representative sample of urban newlywed couples (199 Black and 174 White). A factor analysis of the reports found 6 factors common to husbands and wives: Disclosing Communication, Affective Affirmation, Negative Sexual Interaction, Traditional Role Regulation, Destructive Conflict, and Constructive Conflict. Avoiding Conflict was specific to men and Positive Coorientation was specific to women. Wives reported fewer constructive and destructive conflict behaviors. Compared with Whites, Blacks reported more disclosure, more positive sexual interactions, and fewer topics of disagreement. They also more often reported leaving the scene of conflict and talking with others more easily than with the spouse. As hypothesized, perceptions that marital interactions affirm one's sense of identity strongly predicted marital well-being. Although regression analyses predicting marital happiness yielded few interactions with race or gender, those that are significant, coupled with race and gender differences in perceiving interaction, suggest taking a contextual orientation to the meaning of marital interaction. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
997.
The domain reduction method uses a finite group of symmetries of a system of linear equations arising by discretization of partial differential equations to obtain a decomposition into independent subproblems, which can be solved in parallel. This paper develops a theory for this class of methods based on known results from group representation theory and algebras of finite groups. The main theoretical result is that if the problem splits into subproblems based on isomorphic subdomains, then the group of symmetries must be commutative. General decompositions are then obtained by nesting decompositions based on commutative groups of symmetries.  相似文献   
998.
999.
1000.
A meta-analysis of child and adolescent psychotherapy outcome research tested previous findings using a new sample of 150 outcome studies and weighted least squares methods. The overall mean effect of therapy was positive and highly significant. Effects were more positive for behavioral than for nonbehavioral treatments, and samples of adolescent girls showed better outcomes than other Age?×?Gender groups. Paraprofessionals produced larger overall treatment effects than professional therapists or students, but professionals produced larger effects than paraprofessionals in treating overcontrolled problems (e.g., anxiety and depression). Results supported the specificity of treatment effects: Outcomes were stronger for the particular problems targeted in treatment than for problems not targeted. The findings shed new light on previous results and raise significant issues for future study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号