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   1611篇
  免费   57篇
电工技术   4篇
综合类   1篇
化学工业   306篇
金属工艺   11篇
机械仪表   25篇
建筑科学   70篇
矿业工程   2篇
能源动力   28篇
轻工业   204篇
水利工程   12篇
石油天然气   3篇
无线电   66篇
一般工业技术   341篇
冶金工业   458篇
原子能技术   5篇
自动化技术   132篇
  2024年   2篇
  2023年   24篇
  2022年   43篇
  2021年   54篇
  2020年   36篇
  2019年   31篇
  2018年   37篇
  2017年   35篇
  2016年   35篇
  2015年   32篇
  2014年   44篇
  2013年   89篇
  2012年   93篇
  2011年   123篇
  2010年   84篇
  2009年   79篇
  2008年   101篇
  2007年   91篇
  2006年   90篇
  2005年   80篇
  2004年   72篇
  2003年   60篇
  2002年   62篇
  2001年   37篇
  2000年   35篇
  1999年   18篇
  1998年   23篇
  1997年   19篇
  1996年   27篇
  1995年   22篇
  1994年   16篇
  1993年   11篇
  1992年   7篇
  1991年   4篇
  1990年   13篇
  1989年   8篇
  1988年   6篇
  1987年   5篇
  1986年   3篇
  1985年   6篇
  1984年   2篇
  1983年   1篇
  1981年   2篇
  1980年   2篇
  1978年   3篇
  1975年   1篇
排序方式: 共有1668条查询结果,搜索用时 15 毫秒
101.
Collagen is a vital material in the tissues of living organisms. Found almost everywhere in the human body, collagen is important in connective tissues, bone growth, and cartilage. Collagen XI makes up a very small portion of the cartilaginous tissue; however, it plays a key role in cartilaginous tissue. Collagen XI and two collagen XI isoforms, V1b and V2, are critical in the ossification process. The location of collagen XI, V1b, V2, and their specific functions in the ossification process within developing bovine cartilage are not well characterized. In this work, the location of collagens I, II, XI and two collagen XI isoforms, V1b and V2, present in developing bovine cartilage are investigated using the immuno-SEM technique. The results for the locations of collagen I and II indicate a high level of consistency with previous work, thus showing that the technique of immuno-SEM can be used with confidence to determine the location of various collagen types within cartilaginous and mineralized tissue. This work has shown that collagen XI is present in the lower hypertrophic region and also in a pericellular arrangement, within about two microns of cell walls, throughout the cartilaginous tissue. V1b is expressed in the articular surface, mineralized region, resting zone, and the distal edge of the diaphysis. The V2 isoform is most strongly expressed in areas of newly forming cartilage, and disappears with chondrocyte maturation. V2 is present in the distal edge of the epiphysis, as well as in mineralized tissue. Collagen XI and two of its isoforms, V1b and V2, are thought to play a critical role in the ossification process. However, this role is not well understood, and is still being characterized. The detection of collagen XI and two of its isoforms in the osteo-chondral junction as well as at a joint surface further point to collagen XI, V1b, and V2 playing a vital role in the ossification process, and warrants further research as to their specific function within the ossification process.  相似文献   
102.
Civil engineering is an interdisciplinary field, and most of the projects designed and built represent very complex systems, both during the construction phase and in the built phase. This research describes how a course in land development that included engineering design elements, lectures that also touched on other related fields, and a field journal assignment at a “green” (sustainable) construction site facilitated students’ understanding of complex systems. Results suggest that this course design facilitates the development of students’ proficiencies in several skill sets, and can increase students’ understanding of the complexity involved in civil engineering projects.  相似文献   
103.
The present study assessed drug use and the validity of self–reports of substance use among help–seeking veterans referred to a specialty clinic for the assessment of posttraumatic stress disorder (PTSD). Patients (n?=?341) were asked to provide a urine sample for use in drug screening as part of an evaluation of PTSD. Self–reports of substance use were compared with same–day supervised urine samples for 317 patients who volunteered to participate in a drug screening. Results suggested that self–reports were generally quite valid. Only 8% of the cases involved patients not reporting substance use detected by urine screens. A total of 42% of the participants were identified as using drugs of abuse (excluding alcohol) through self–report and urine drug screens. Among participants using drugs, PTSD diagnosis was significantly associated with greater marijuana and depressant use as compared with stimulant (cocaine and amphetamines) use. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
104.
105.
This study was conducted to identify therapist and client behaviors with a positive response to social learning-based behavioral marital therapy. A sample of 32 couples receiving treatment was examined. Immediately after each therapy session, the therapist, husband, and wife independently completed process ratings forms that measured therapist and client behaviors during the session. Composite scales, derived from these ratings, were entered into multiple regression equations to examine their relationship with posttherapy marital satisfaction. After controlling for pretherapy marital satisfaction and the other predictor variables, therapists', husbands', and wives' ratings of positive client behavior (i.e., collaboration, active participation, and homework compliance) were positively associated with therapy outcome. Implications for marital therapy and suggestions for future research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
106.
Teacher perceptions about students' academic abilities are important for several reasons (e.g., instructional decision making, special education entitlement decisions). Not surprisingly, researchers have investigated the accuracy of teachers' decisions. Although some data reveal that teachers are relatively good judges of academic performance, other findings have suggested otherwise. A likely explanation for conflicting findings is the varying assessment methods (e.g., direct vs. indirect, norm-referenced vs. peer-independent) and different data analysis procedures that have been used across studies. The purpose of this study was to investigate a continuum of teacher-perception assessment methods as they corresponded to students' oral reading fluency performance. Participants included 10 teachers and 87 first, second, and third grade students from a suburban school in the northeast. Overall results suggested that teachers were generally accurate when estimating students' performance when students had strong oral reading fluency skills, but teachers had more difficulty judging students with average to low oral reading fluency. Further, data interpretation of teachers' judgment accuracy differed somewhat depending upon the statistical method employed. Implications, limitations, and suggestions for future research related to this study are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
107.
Peripheral capsaicin treatment induces molecular changes that sensitize the responses of nociceptive neurons in the spinal dorsal horn. The current studies demonstrate that capsaicin also undermines the adaptive plasticity of the spinal cord, rendering the system incapable of learning a simple instrumental task. In these studies, male rats are transected at the second thoracic vertebra and are tested 24 to 48 hours later. During testing, subjects receive shock to one hindleg when it is extended (controllable stimulation). Rats quickly learn to maintain the leg in a flexed position. Rats that have been injected with capsaicin (1% or 3%) in the hindpaw fail to learn, even when tested on the leg contralateral to the injection. This learning deficit lasts at least 24 hours. Interestingly, training with controllable electrical stimulation prior to capsaicin administration protects the spinal cord against the maladaptive effects. Rats pretrained with controllable stimulation do not display a learning deficit or tactile allodynia. Moreover, controllable stimulation, combined with naltrexone, reverses the capsaicin-induced deficit. These data suggest that peripheral inflammation, accompanying spinal cord injuries, might have an adverse effect on recovery. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
108.
109.
Women smokers concerned about weight gain (N?=?219) were randomly assigned to 1 of 3 adjunct treatments accompanying group smoking cessation counseling: (a) behavioral weight control to prevent weight gain (weight control); (b) cognitive–behavioral therapy (CBT) to directly reduce weight concern, in which dieting was discouraged; and (c) standard counseling alone (standard), in which weight gain was not explicitly addressed. Ten sessions were conducted over 7 weeks, and no medication was provided. Continuous abstinence was significantly higher at posttreatment and at 6 and 12 months of follow-up for CBT (56%, 28%, and 21%, respectively), but not for weight control (44%, 18%, and 13%, respectively), relative to standard (31%, 12%, and 9%, respectively). However, weight control, and to a lesser extent CBT, was associated with attenuation of negative mood after quitting. Prequit body mass index, but not change in weight or in weight concerns postquit, predicted cessation outcome at 1 year. In sum, CBT to reduce weight concerns, but not behavioral weight control counseling to prevent weight gain, improves smoking cessation outcome in weight-concerned women. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
110.
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