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   1717篇
  免费   30篇
  国内免费   2篇
电工技术   3篇
化学工业   254篇
金属工艺   21篇
机械仪表   23篇
建筑科学   108篇
矿业工程   11篇
能源动力   22篇
轻工业   239篇
水利工程   21篇
石油天然气   4篇
无线电   53篇
一般工业技术   158篇
冶金工业   652篇
原子能技术   3篇
自动化技术   177篇
  2023年   10篇
  2022年   19篇
  2021年   24篇
  2020年   18篇
  2019年   20篇
  2018年   19篇
  2017年   25篇
  2016年   35篇
  2015年   18篇
  2014年   26篇
  2013年   101篇
  2012年   51篇
  2011年   80篇
  2010年   62篇
  2009年   44篇
  2008年   62篇
  2007年   74篇
  2006年   76篇
  2005年   61篇
  2004年   61篇
  2003年   61篇
  2002年   51篇
  2001年   33篇
  2000年   38篇
  1999年   38篇
  1998年   31篇
  1997年   43篇
  1996年   35篇
  1995年   33篇
  1994年   26篇
  1993年   36篇
  1992年   31篇
  1991年   13篇
  1990年   33篇
  1989年   23篇
  1988年   19篇
  1987年   25篇
  1986年   22篇
  1985年   19篇
  1984年   24篇
  1983年   22篇
  1982年   19篇
  1981年   17篇
  1980年   14篇
  1978年   10篇
  1977年   15篇
  1976年   16篇
  1975年   18篇
  1974年   11篇
  1973年   9篇
排序方式: 共有1749条查询结果,搜索用时 15 毫秒
41.
The use of medical services is a function of several interacting psychological and social variables as well as a function of physical malfunction. The clinical significance of addressing patients' psychosocial issues has only occasionally been considered. However, the shift in health care economics toward health care maintenance is responsible for the increased interest in interventions in the domain of behavioral medicine and health psychology. Evidence is reviewed for 6 mechanistic pathways by which behavioral interventions can maximize clinical care and result in significant economic benefits. The rationale for further integration of behavioral and biomedicine interventions is also reviewed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
42.
Charles R. (Bob) Schuster, an internationally recognized researcher on the psychopharmacology of drugs of abuse, passed away on February 21, 2011. Bob Schuster was a pioneer in the scientific study of addiction and one of the founders of a specialized research field called behavioral pharmacology. Bob mentored many young scientists, including 15 doctoral students, 9 postdoctoral fellows, and many visiting scientists from around the world, as well as junior faculty members at the academic institutions where he had faculty appointments. Bob was active in numerous professional organizations and was the recipient of many national and international awards. Personally, Bob Schuster touched the lives of a great many people: his students, colleagues, extended family, and many friends. Bob is survived by his wife and colleague Chris-Ellyn Johanson; four children, Lyzbett, Rebecca, Robert, and Alyson; and seven grandchildren. He is also survived by his sister Bette Quemore. He was a man of many talents, a loving husband and father, and a great friend. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
43.
This theoretical model of emotion is based on research using the startle-probe methodology. It explains inconsistencies in probe studies of attention and fear conditioning and provides a new approach to emotional perception, imagery, and memory. Emotions are organized biphasically, as appetitive or aversive (defensive). Reflexes with the same valence as an ongoing emotional state are augmented; mismatched reflexes are inhibited. Thus, the startle response (an aversive reflex) is enhanced during a fear state and is diminished in a pleasant emotional context. This affect–startle effect is not determined by general arousal, simple attention, or probe modality. The effect is found when affects are prompted by pictures or memory images, changes appropriately with aversive conditioning, and may be dependent on right-hemisphere processing. Implications for clinical, neurophysiological and basic research in emotion are outlined. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
44.
In This Issue     
Software Quality Journal -  相似文献   
45.
While computable general equilibrium (CGE) models are a well-established tool in economic analyses, it is often difficult to disentangle the effects of policies of interest from that of the assumptions made regarding the underlying calibration data and model parameters. To characterize the behavior of a CGE model of carbon output with respect to two of these assumptions, we perform a large-scale Monte Carlo experiment to examine its sensitivity to base year calibration data and elasticity of substitution parameters in the absence of a policy change. By examining a variety of output variables at different levels of economic and geographic aggregation, we assess how these forms of uncertainty impact the conclusions that can be drawn from the model simulations. We find greater sensitivity to uncertainty in the elasticity of substitution parameters than to uncertainty in the base-year data as the projection period increases. While many model simulations were conducted to generate large output samples, we find that few are required to capture the mean model response of the variables tested. However, characterizing standard errors and empirical probability distribution functions is not possible without a large number of simulations.  相似文献   
46.
While economizing can improve the performance of vapor compression cycles, the cost of multi-stage compressors has limited its implementation to large-scale applications. However, the development of compressors with injection ports presents new opportunities for economizing in smaller-scale applications. In addition to eliminating the need for a costly multi-stage compressor, multiple injection ports can be added at relatively low cost to further improve cycle performance. In the current study, a model was developed to study the effect of the number of injection ports on performance and determine the limit to performance with injection. The model predicts that continuous injection, in which economized refrigerant is injected at an infinite number of ports to maintain saturated vapor in the compressor, provides very significant performance improvements for air-conditioning and refrigeration applications. At standard operating conditions, the COP increases between 18% and 51% depending on the application, with higher temperature lift cycles benefiting most significantly.  相似文献   
47.
A growing body of work suggests epigenetic dysregulation contributes to endometriosis pathophysiology and female infertility. The chromatin remodeling complex subunit AT-rich interaction domain 1A (ARID1A) must be properly expressed to maintain normal uterine function. Endometrial epithelial ARID1A is indispensable for pregnancy establishment in mice through regulation of endometrial gland function; however, ARID1A expression is decreased in infertile women with endometriosis. We hypothesized that ARID1A performs critical operations in the endometrial epithelium necessary for fertility besides maintaining gland function. To identify alterations in uterine gene expression resulting from loss of epithelial ARID1A, we performed RNA-sequencing analysis on pre-implantation uteri from LtfiCre/+Arid1af/f and control mice. Differential expression analysis identified 4181 differentially expressed genes enriched for immune-related ingenuity canonical pathways including agranulocyte adhesion and diapedesis and natural killer cell signaling. RT-qPCR confirmed an increase in pro-inflammatory cytokine and macrophage-related gene expression but a decrease in natural killer cell signaling. Immunostaining confirmed a uterus-specific increase in macrophage infiltration. Flow cytometry delineated an increase in inflammatory macrophages and a decrease in uterine dendritic cells in LtfiCre/+Arid1af/f uteri. These findings demonstrate a role for endometrial epithelial ARID1A in suppressing inflammation and maintaining uterine immune homeostasis, which are required for successful pregnancy and gynecological health.  相似文献   
48.
Nurr1 and brain-derived neurotrophic factor (BDNF) play major roles in cognition. Nurr1 regulates BDNF in midbrain dopaminergic neurons and cerebellar granule cells. Nurr1 and BDNF are also highly expressed in the cerebral cortex, a brain area important in cognition. Due to Nurr1 and BDNF tissue specificity, the regulatory effect of Nurr1 on BDNF in different brain areas cannot be generalized. The relationship between Nurr1 and BDNF in the cortex has not been investigated previously. Therefore, we examined Nurr1-mediated BDNF regulation in cortical neurons in activity-dependent and activity-independent states. Mouse primary cortical neurons were treated with the Nurr1 agonist, amodiaquine (AQ). Membrane depolarization was induced by KCl or veratridine and reversed by nimodipine. AQ and membrane depolarization significantly increased Nurr1 (p < 0.001) and BDNF (pAQ < 0.001, pKCl < 0.01) as assessed by real-time qRT-PCR. However, Nurr1 knockdown did not affect BDNF gene expression in resting or depolarized neurons. Accordingly, the positive correlation between Nurr1 and BDNF expression in AQ and membrane depolarization experiments does not imply co-regulation because Nurr1 knockdown did not affect BDNF gene expression in resting or depolarized cortical neurons. Therefore, in contrast to midbrain dopaminergic neurons and cerebellar granule cells, Nurr1 does not regulate BDNF in cortical neurons.  相似文献   
49.
50.
This article characterizes a novel twin screw extrusion (TSE) process with the capability of rotating at speeds up to 4500 rpm. The resulting extreme high shear rate is expected to result in molecular weight changes due to thermomechanical degradation of the polymeric materials being extruded, polystyrene (PS) in this case. In order to differentiate between mechanical and thermal factors affecting degradation of PS running at ultrahigh speeds and also to evaluate the relative importance of the two mechanisms, PS has been extruded at different screw speeds and different barrel temperatures with corresponding melt temperatures. Viscosity measurements and size exclusion chromatography measurements show the extent of degradation due to mechanical stress as a result of high screw rotational speeds. Furthermore, through analyzing the kinetics of PS depolymerization, the reaction rate and hypothetical apparent temperatures at each screw speed have been calculated. All results support the idea that the mechanical shear stress can be considered as the controlling factor of polymer degradation in ultrahigh speed TSE. POLYM. ENG. SCI., 56:743–751, 2016. © 2016 Society of Plastics Engineers  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