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   4985篇
  免费   303篇
  国内免费   3篇
电工技术   25篇
综合类   12篇
化学工业   1425篇
金属工艺   54篇
机械仪表   64篇
建筑科学   327篇
矿业工程   4篇
能源动力   81篇
轻工业   868篇
水利工程   60篇
石油天然气   22篇
无线电   196篇
一般工业技术   744篇
冶金工业   797篇
原子能技术   12篇
自动化技术   600篇
  2024年   10篇
  2023年   53篇
  2022年   149篇
  2021年   211篇
  2020年   98篇
  2019年   141篇
  2018年   149篇
  2017年   132篇
  2016年   165篇
  2015年   137篇
  2014年   229篇
  2013年   338篇
  2012年   283篇
  2011年   398篇
  2010年   281篇
  2009年   231篇
  2008年   249篇
  2007年   221篇
  2006年   217篇
  2005年   157篇
  2004年   160篇
  2003年   141篇
  2002年   110篇
  2001年   73篇
  2000年   76篇
  1999年   59篇
  1998年   52篇
  1997年   54篇
  1996年   59篇
  1995年   53篇
  1994年   40篇
  1993年   42篇
  1992年   46篇
  1991年   36篇
  1990年   51篇
  1989年   37篇
  1988年   39篇
  1987年   34篇
  1986年   25篇
  1985年   25篇
  1984年   38篇
  1983年   12篇
  1982年   28篇
  1981年   10篇
  1980年   17篇
  1979年   24篇
  1978年   13篇
  1977年   10篇
  1975年   17篇
  1972年   9篇
排序方式: 共有5291条查询结果,搜索用时 0 毫秒
991.
Objective: To investigate pre- to postinjury personality change in relation to outcomes following traumatic brain injury (TBI). Design: Prospective analysis of personality ratings, depression, and outcome using multiple regression analyses. Participants: Cohort of 3 clinical trauma groups (mild TBI, moderate-severe TBI, orthopedic injury) and their significant others (SO). Outcome Measures: Independent Living Scale, Vocational Independence Scale, and Mayo-Portland Adaptability Inventory, 1-2 years postinjury. Predictor Variables: Posttraumatic amnesia (PTA); patient and SO NEO Personality Inventory-Revised ratings of preinjury personality taken at 1-2 months postinjury. Results: Personality function was normal for all groups (regardless of rating source) and stable over time. Neuroticism, and specifically depression, accounted for small proportions of variance in functional outcome, beyond PTA. Conclusions: There is little empirical evidence for significant personality disturbance or change up to 2 years post-TBI. Personality and depression contribute modestly to functional outcomes. Results support a distinction between "personality change" and behavior change following TBI. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
992.
Clients (N = 77) undergoing cognitive therapy for depression were assessed before treatment with the Clinical Outcomes in Routine Evaluation-Outcome Measure (CORE-OM), which encompasses domains of subjective well-being, problems, functioning, and risk of harming self or others, along with the Beck Depression Inventory-II (BDI-II), the Hamilton Rating Scale for Depression (HRSD), the Beck Hopelessness Scale (BHS), and a measure of avoidant (Cluster C) personality problems (Inventory of Interpersonal Problems-Avoidant [IIP-Av]). The CORE-OM and the BDI-II were strongly correlated with each other and showed coherent and similar patterns of correlations with the HRSD, the BHS, and the IIP-Av. Sixty-one of the clients were repeatedly assessed during treatment with alternating versions of the CORE Short Form and with the BDI-II. Results strongly supported the convergent validity of the CORE measures with the BDI-II in across-clients comparisons of means scores and rates of improvement and in across-sessions comparisons within clients. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
993.
Bridge abutments typically contain a backwall element that is designed to break free of its base support when struck by a bridge deck during an earthquake event and push into the abutment backfill soils. Results are presented for a full-scale cyclic lateral load test of an abutment backwall configured to represent the dimensions (1.7?m height), boundary conditions, and backfill materials (compacted silty sand) that are typical of California bridge design practice. An innovative loading system was utilized that operates under displacement control and that assures horizontal wall displacement with minimal vertical displacement. The applied horizontal displacement ranged from null to approximately 11% of the wall height (0.11H). The maximum earth pressure occurred at a wall displacement of 0.03H and corresponded to a passive earth pressure coefficient of Kp = 16.3. The measured force distribution applied to the wall from hydraulic actuators allowed the soil pressure distribution to be inferred as triangular in shape and the mobilized wall-soil interface friction to be evaluated as approximately one-third to one-half of the soil friction angle. Post-test trenching of the backfill showed a log-spiral principal failure surface at depth with several relatively minor shear surfaces further up in the passive wedge. The ultimate passive resistance is well estimated by the log-spiral method and a method of slices approach. The shape of the load-deflection relationship is well estimated by models that produce a hyperbolic curve shape.  相似文献   
994.
Experimental investigations have been made in which single crystals of solid explosives such as cyclotrimethylene trinitramine, RDX, pentaerythritol tetranitrate, PETN, AgN3 and Pb(N3)2, were irradiated with a focused laser beam of wavelength 266 nm and duration 5 nsec in an ultra high vacuum system housing a fast and sensitive time-of-flight mass spectrometer. From the mass spectra (both +ve and -ve ions) of the chemical species obtained, possible decomposition schemes of RDX and PETN have been proposed. For silver and lead azides, the laser irradiation did not cause explosions if the power density was sufficiently low, but micrometre size craters were formed. In the mass spectra of AgN3 products N3 and silver cluster ions, Ag n +, have been found for the first time. It has been suggested that such investigations may possibly throw some light on our understanding of the reactions taking place in a deflagration/detonation wave.  相似文献   
995.
Posttraumatic stress (PTS) symptoms have been reported in mothers and fathers of childhood cancer survivors; however, little is known about patterns of PTS in these families. Cluster analysis was applied to the Posttraumatic Stress Disorder (PTSD) Reaction Index scores of 98 couples parenting adolescent childhood cancer survivors to describe patterns of PTS in families, yielding the following 5 clusters: Minimal PTS, Mothers Elevated, Disengaged, Fathers Elevated, and Elevated PTS. The clusters were validated using data from a structured psychiatric interview, an additional self-report measure of PTS, and an index of family functioning. These clinically meaningful patterns reveal that a majority of families had at least one parent with moderate to severe PTS, which supports development of family-based interventions for this population. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
996.
This paper presents an approach for implementing sustainability within a university environment, and for helping students become more effective problem solvers and professionals. In a “Sustainable Urban Development” course, taught by the writer, students develop projects to make their campus and community more sustainable. In the process, students learn how to analyze sustainability, work with decision makers, and put classroom knowledge into practice. Further, through this course’s emphasis on problem-based learning, students acquire critical cognitive skills and professional skills as they tackle complex, interdisciplinary, and real-world problems. Systematic evaluations of the course offer useful lessons. One is how to create synergies. For instance, while students benefited from hands-on experience with sustainability, the university benefited from students’ work. Another is how to demonstrate and quantify benefits from sustainability, which is vital to gaining support. Yet another is how to enable students to learn from both successful and unsuccessful attempts to implement ideas. Courses such as this can create important bridges between theory and application, and between education and professional practice.  相似文献   
997.
Data from 2 daily diary studies of stress, negative affect, and drinking were used to examine the correspondence between global self-reports of drinking to cope (DTC) and within-person stress/negative affect-drinking associations. In Study 1, 83 community-residing drinkers recorded data in nightly booklets on negative events, perceived stress, negative affect, and drinking for 60 consecutive days. In Study 2, 88 community-residing drinkers recorded data on negative events and negative interpersonal exchanges nightly and negative affect and drinking in near-real time on palmtop computers for 30 consecutive days. Both studies showed only modest correspondence between self-reported DTC and between-person differences in within-day, daily, and weekly associations between stress/negative affect and drinking. The findings indicate that individuals who report higher DTC simply may drink across a wider variety of conditions than those who report relatively lower DTC. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
998.
Data from 2 contingency management trials, targeting opiate or cocaine use, were used to investigate whether noncontingent vouchers inadvertently reinforce drug use. The control group in each trial received noncontingent vouchers matched in value and frequency to those received by experimental groups, but independent of urinalysis. Vouchers were offered thrice weekly for 8 weeks (opiates) or 12 weeks (cocaine). Both dose-response and temporal associations of noncontingent voucher receipt with drug-positive urines were assessed. Drug use was unrelated to frequency of noncontingent voucher delivery and noncontingent voucher receipt when being drug positive was unassociated with risk of subsequent drug use, with one exception: cocaine use in the cocaine study (relative risk = 1.05, 95% confidence interval: 1.01-1.09). Overall, results do not indicate a causal relationship between noncontingent voucher receipt and increased drug use. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
999.
The role of psychologists in psychiatric settings has evolved over the past century from primarily conducting psychological evaluations to being the vital and integral link (sometimes the only such link) to the delivery of scientifically sound assessment and treatment methods. Consequently, the role of the psychologist, with respect to the scientist-practitioner model, has expanded to include collaborator with, consultant to, and teacher of our colleagues in psychiatry. In the integrated areas of research and treatment of anxiety disorders, psychologists have been at the forefront of developing, evaluating, and disseminating empirically supported methods for the range of these conditions in children, adolescents, and adults. Issues common to psychologists practicing in psychiatric settings are discussed in this article, specifically with reference to the tasks and issues encountered by the anxiety specialist. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
1000.
Connell and Wellborn proposed a model which posits that the social context influences the development of self system processes which in turn have an impact on school engagement. The purpose of the present study was to test the validity of the Connell and Wellborn's model in line with academic procrastination. The model suggests that self-determination in family activities (implication) and the quality of the relation between parents and their children (structure) are positively associated to children's self-system processes (competence, autonomy, and relatedness). Moreover, the model proposes that children's self-system processes are negatively related to academic procrastination. Participants were 100 families (father, other, and children) from the Quebec city area. Results from path analysis supported the model. Theoretical implications of the findings are discussed in line with Connell and Wellborn's model. (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