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   669篇
  免费   21篇
  国内免费   1篇
电工技术   2篇
化学工业   129篇
金属工艺   2篇
机械仪表   13篇
建筑科学   22篇
能源动力   34篇
轻工业   50篇
水利工程   7篇
石油天然气   1篇
无线电   36篇
一般工业技术   145篇
冶金工业   162篇
原子能技术   3篇
自动化技术   85篇
  2023年   3篇
  2022年   17篇
  2021年   20篇
  2020年   9篇
  2019年   10篇
  2018年   21篇
  2017年   12篇
  2016年   10篇
  2015年   13篇
  2014年   19篇
  2013年   28篇
  2012年   23篇
  2011年   41篇
  2010年   29篇
  2009年   28篇
  2008年   26篇
  2007年   26篇
  2006年   33篇
  2005年   28篇
  2004年   27篇
  2003年   24篇
  2002年   13篇
  2001年   9篇
  2000年   13篇
  1999年   13篇
  1998年   30篇
  1997年   20篇
  1996年   16篇
  1995年   15篇
  1994年   11篇
  1993年   9篇
  1992年   7篇
  1991年   4篇
  1990年   8篇
  1988年   2篇
  1987年   2篇
  1986年   2篇
  1985年   8篇
  1984年   5篇
  1983年   3篇
  1982年   6篇
  1981年   7篇
  1979年   6篇
  1978年   3篇
  1977年   5篇
  1976年   3篇
  1975年   7篇
  1973年   3篇
  1972年   3篇
  1968年   2篇
排序方式: 共有691条查询结果,搜索用时 15 毫秒
61.
Used concentrated cigarette smoke as an aversive agent in the treatment of 89 habitual cigarette smokers. A factorial design assessed the incremental efficacy of 3 procedures, hypothesized to increase treatment durability, as a function of client characteristics. The 1st, treatment focus, contrasted procedures considered optimal for internal vs external locus of control clients (measured with Rotter's Internal-External Control Scale). The 2nd, punishment, assessed an instruction to punish postclinic smoking with stimulus satiation conditions. The 3rd, timing of attitude change, presented an attitude change manipulation either before or after behavior change. The Eysenck Personality Inventory and C. S. Keutzer's effective cognitive dissonance measure were also administered. Changes in smoking behavior were monitored over a 6-mo period. 2 of the 3 treatment factors, treatment focus and timing of attitude change, interacted significantly with client characteristics in determining treatment outcome. Findings support the principle of tailoring therapeutic procedures to individual differences. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
62.
Longitudinal stripes are a common bed form in heterogeneous alluvial sediments and consist of periodic, spanwise variations in bed texture and elevation that are aligned parallel to the mean flow direction. This paper quantifies mean and turbulent flow structures over self-formed sediment stripes in a weakly bimodal sand and gravel mixture. Turbulence anisotropy generates two secondary circulation cells across the channel half-width, which produce a cross-stream perturbation in boundary shear stress. The interaction between this flow structure and the selective transport of bed material generates spanwise sediment sorting that is symmetrical about the centerline. Finer sediments are entrained from regions of high shear stress, transported laterally by the secondary flow, and deposited in regions of lower shear stress. Lateral changes in bed texture further enhance the near-bed secondary flow, which provides a positive feedback mechanism for stripe growth. In bimodal sediments, at shear stresses just above the entrainment threshold, stripes may replace lower-stage plane beds. At higher shear stresses the coarser sediment becomes more mobile and the stripes are replaced by flow transverse bed forms.  相似文献   
63.
Mood-congruent working memory biases were examined in a delayed matching to sample paradigm using the slow wave (SW) event-related brain potential (ERP) component. Mood-congruent working memory biases, indexed by SW amplitudes, were demonstrated among individuals experiencing a major depressive episode (MDE) and nondepressed controls but not individuals with dysthymia. However, analyses of symptom severity demonstrated that those with dysthymia exhibited significantly less negative SW amplitudes with increasing depressive mood severity, whereas individuals with major depression demonstrated more negative SW amplitudes with increasing depressive mood severity. These results are discussed in the context of diagnostic specificity for cognitive biases associated with working memory of mood-disordered individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
64.
65.
A methodology for scaling in situ bioremediation problems is presented. This methodology is based on multiphase, muiticomponent transport theory and employs inspectional analysis and numerical sensitivity studies. A general mathematical model that describes subsurface aerobic biotransformation of organic chemical species in a multiphase setting is first presented. This general model is applied to the specific case of microbial enhanced vapor-vacuum extraction (MEVVE) in a one-dimensional zone of immobile liquids. The resulting simplified MEVVE model considers rate-dependent interphase mass transfer, a flowing gaseous phase, a single hydrocarbon pseudo-component, and either oxygen or hydrocarbon limited microbial activity. By inspectional analysis a set of dimensionless groups are derived that represent the various model parameters. A scries of numerical sensitivity studies are presented that examine the impact of selected dimensionless groups on overall system biotransformation rates. This analysis demonstrates that overall biotranformation rates can be significantly limited not only by insufficient transport of oxygen in the gaseous phase, but also by interfacial mass transfer resistance between nonaqueous phase liquid globules and adjacent fluids. Finally, an examination of the selected dimensionless groups reveals the parameter requirements for properly scaled MEVVE tests. These results indicate the need for further investigation of the importantance of fluid distributions in the pore space and their impact on the design of laboratory and field tests.  相似文献   
66.
The biological performance of orthopaedic and oral metallic implants can be enhanced significantly by the application of bioactive coatings. In this work, a cost-efficient alternative to the traditional technique to produce a hydroxyapatite (HA) coating with a nanostructured feature onto a metallic implant surface at room temperature via electrospray deposition, is presented. To evaluate the bioactive capacity of these nanoHA (nHA) coatings in vitro, an acellular simulated body fluid soaking experiment and a human osteoblast (HOB) cell culture work were conducted. Under these physiological conditions, the accelerated apatite precipitation process occurred on the nHA-coated titanium surfaces as compared to the uncoated titanium surfaces. HOB cells developed mature cytoskeletons with distinct evidence of actin stress fibres and vinculin adhesion plaques, on these nHA coatings. Hence, this deposition technique holds great potential in producing high quality nHA coatings for biomedical applications.  相似文献   
67.
Summary A non-reducing disaccharide has been isolated from the kernels of tung (Aleurites fordi Hemsl.) and identified as sucrose.  相似文献   
68.
Placental extracellular vesicles (EVs) have increasingly been recognized as a major mediator of feto-maternal communication. However, the cellular and molecular mechanisms of the uptake of placental EVs by recipient cells are still not well-understood. We previously reported that placental EVs target a limited number of organs in vivo. In the current study, we investigated the mechanisms underlying the uptake of placental EVs into target cells. Placental EVs were derived from explant cultures of normal or preeclamptic placentae. The mechanisms underlying the uptake of placental EVs were elucidated, using the phagocytosis or endocytosis inhibitor, trypsin-treatment or integrin-blocking peptides. The endothelial cell activation was studied using the monocyte adhesion assay after the preeclamptic EVs exposure, with and/or without treatment with the integrin blocking peptide, YIGSR. The cellular mechanism of the uptake of the placental EVs was time, concentration and energy-dependent and both the phagocytosis and endocytosis were involved in this process. Additionally, proteins on the surface of the placental EVs, including integrins, were involved in the EV uptake process. Furthermore, inhibiting the uptake of preeclamptic EVs with YIGSR, reduced the endothelial cell activation. The interaction between the placental EVs and the recipient cells is mediated by integrins, and the cellular uptake is mediated by a combination of both phagocytosis and endocytosis.  相似文献   
69.
Biomarkers are crucial in oncology, from detection and monitoring to guiding management and predicting treatment outcomes. Histological assessment of tissue biopsies is currently the gold standard for oropharyngeal cancers, but is technically demanding, invasive, and expensive. This systematic review aims to review current markers that are detectable in biofluids, which offer promising non-invasive alternatives in oropharyngeal carcinomas (OPCs). A total of 174 clinical trials from the PubMed search engine in the last 5 years were identified and screened by 4 independent reviewers. From these, 38 eligible clinical trials were found and subsequently reviewed. The biomarkers involved, categorized by human papillomavirus (HPV)-status, were further divided according to molecular and cellular levels. Recent trials investigating biomarkers for both HPV-positive and HPV-negative OPCs have approaches from various levels and different biofluids including plasma, oropharyngeal swabs, and oral rinse. Promising candidates have been found to aid in detection, staging, and predicting prognosis, in addition to well-established factors including HPV-status, drinking and smoking status. These studies also emphasize the possibility of enhancing prediction results and increasing statistical significance by multivariate analyses. Liquid biopsies offer promising assistance in enhancing personalized medicine for cancer treatment, from lowering barriers towards early screening, to facilitating de-escalation of treatment. However, further research is needed, and the combination of liquid biopsies with pre-existing methods, including in vivo imaging and invasive techniques such as neck dissections, could also be explored in future trials.  相似文献   
70.
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