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   30359篇
  免费   755篇
  国内免费   39篇
电工技术   372篇
综合类   15篇
化学工业   6415篇
金属工艺   595篇
机械仪表   555篇
建筑科学   1298篇
矿业工程   337篇
能源动力   702篇
轻工业   2000篇
水利工程   251篇
石油天然气   261篇
武器工业   1篇
无线电   2102篇
一般工业技术   4526篇
冶金工业   7315篇
原子能技术   317篇
自动化技术   4091篇
  2022年   263篇
  2021年   442篇
  2020年   277篇
  2019年   372篇
  2018年   465篇
  2017年   412篇
  2016年   536篇
  2015年   420篇
  2014年   663篇
  2013年   1832篇
  2012年   1028篇
  2011年   1330篇
  2010年   998篇
  2009年   1058篇
  2008年   1263篇
  2007年   1181篇
  2006年   1090篇
  2005年   979篇
  2004年   845篇
  2003年   800篇
  2002年   800篇
  2001年   554篇
  2000年   452篇
  1999年   533篇
  1998年   750篇
  1997年   587篇
  1996年   618篇
  1995年   526篇
  1994年   540篇
  1993年   523篇
  1992年   480篇
  1991年   327篇
  1990年   461篇
  1989年   424篇
  1988年   379篇
  1987年   450篇
  1986年   396篇
  1985年   498篇
  1984年   502篇
  1983年   437篇
  1982年   404篇
  1981年   338篇
  1980年   334篇
  1979年   383篇
  1978年   335篇
  1977年   277篇
  1976年   277篇
  1975年   272篇
  1974年   233篇
  1973年   243篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
The settling rates and adsorption isotherms produced by a variety of suites of cationic polyelectrolytes in 3% kaolin suspensions were measured. Settling rates increased with molar mass even for low-mass, high-charge polymers. The very high settling rates produced by cationic copolymers of acrylamide decreased as the charge density of the polymer used increased. Hydrolysis of unbuffered polymers occurred over time and produced large changes in the effectiveness of the polymers. This is attributed to conformational changes. © 1994 John Wiley & Sons, Inc.  相似文献   
92.
Evaluated 120 healthy, sedentary, middle-aged adults randomly assigned to either a 6-mo home-based aerobic exercise training program or to an assessment-only control condition. Adherence across the 6-mo period by the exercise group was demonstrated by self-report and heart rate microprocessor methods to exceed 75%. A 14-item Likert rating scale was used to measure a variety of psychological variables. Significant between-groups differences favoring the exercise group were found on scale items closely associated with actual physical changes that occurred with exercise (satisfaction with shape/appearance, perceived fitness). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
93.
Comments on R. L. Woolfolk and F. C. Richardson's (see record 1985-12614-001) discussion of the ideology of behavior therapy and their argument that behavior therapy cannot develop a conception of what might be appropriate goals of treatment. The present author contends that goals are as much a scientific question as are questions of technique. A scientific approach to the study of goal selection is presented that can be applied to any type of adjustment problem. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
94.
95.
The bidirectional relation between life events and self-reported depression was examined across a 1-year period. With Time 1 depression controlled, Time 2 stress accounted for an additional 10% of Time 2 depressive symptoms. Health-related stress, family violence, and financial stress at Time 2 predicted Time 2 depression after control for Time 1 depression. With Time 1 stress controlled, Time 2 depression accounted for 8% of the variance in Time 2 stress. Time 2 depression predicted Time 2 health-related stress, financial stress, household changes, spouse–partner stress, family violence stress, and substance abuse stress, controlling for each of these stressors at Time 1. The results describe a complex relation between stress and depression and suggest that the relation between stress and depression is moderated by the type of stress. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
96.
A 1-yr follow-up study was conducted on families randomly assigned to settle custody disputes either in mediation or through adversary procedures. Consistent with Time 1 reports, at Time 2 fathers who mediated were substantially more satisfied than were fathers who litigated. Fathers who mediated also complied more with child support orders. Contrary to prediction, the greater satisfaction and compliance of fathers did not lead to increased satisfaction among mothers who mediated. In contrast to Time 1, at follow-up mothers who mediated were significantly less satisfied than were mothers who litigated, but selective attrition may account for these differences. The psychological adjustment of mothers and fathers was not significantly different between settlement groups at Time 2, but mothers in both groups reported less satisfaction with dispute settlement and less dysphoria at Time 2 than they had reported at Time 1. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
97.
Rates of poor psychological adjustment of children with sickle cell disease remained relatively constant over initial and follow-up assessment points. 50 children (aged 7–12 yrs) and their mothers completed the initial protocol. 30 children completed the follow-up plus 5 additional children and their mothers. These Ss were aged 7–24 yrs at follow-up. With initial levels of adjustment controlled, children's strategies for coping with pain accounted for a significant increment in child-reported symptoms and mother-reported internalizing behavior problems at follow-up beyond the contribution of illness and demographic parameters and follow-up interval. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
98.
Previous research on adaptation to visual-motor rearrangement suggests that the CNS represents accurately only 1 visual–motor mapping at a time. This idea was examined in 3 experiments where Ss tracked a moving target under repeated alternations between 2 initially interfering mappings (the "normal" mapping characteristic of computer input devices and a 108° rotation of the normal mapping). Alternation between the 2 mappings led to significant reduction in error under the rotated mapping and significant reduction in the adaptation aftereffect ordinarily caused by switching between mappings. Color as a discriminative cue, interference vs decay in adaptation aftereffect, and intermanual transfer were also examined. The results reveal a capacity for multiple concurrent visual–motor mappings, possibly controlled by a parametric process near the motor output stage of processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
99.
In a prospective study of adolescent depression, adolescents (N?=?1,508) were assessed at Time 1 and after 1 yr (Time 2) on psychosocial variables hypothesized to be associated with depression. Most psychosocial variables were associated with current (n?=?45) depression. Formerly depressed adolescents (n?=?217) continued to differ from never depressed controls on many of the psychosocial variables. Many of the depression-related measures also acted as risk factors for future depression (n?=?112), especially past depression, current other mental disorders, past suicide attempt, internalizing behavior problems, and physical symptoms. Young women were more likely to be, to become, and to have been depressed. Controlling for the psychosocial variables eliminated the gender difference for current and future but not for past depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
100.
Is there a relationship between personality and criminal behavior? We addressed this question in a representative birth cohort of 862 male and female 18-yr-olds. Personality was assessed with the Multidimensional Personality Questionnaire (MPQ). The MPQ measures 10 relatively independent personality traits and was not designed to identify offenders. Delinquency was assessed via 3 data sources: self-reports, informant reports, and official records. Variable-centered analyses revealed that MPQ scales indexing negative emotionality and behavioral constraint were consistent predictors of delinquency across the 3 data sources. Person-centered analyses revealed that youths abstaining from delinquency were uniquely characterized by low interpersonal potency. Youths involved in extensive delinquency were uniquely characterized by feelings of alienation, lack of social closeness and risk taking. Advances in understanding criminal behavior can be made through research that places the personality-delinquency link in a developmental context. (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