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   14892篇
  免费   216篇
  国内免费   11篇
教育   10378篇
科学研究   1746篇
各国文化   118篇
体育   1183篇
综合类   18篇
文化理论   193篇
信息传播   1483篇
  2022年   122篇
  2021年   172篇
  2020年   250篇
  2019年   372篇
  2018年   524篇
  2017年   528篇
  2016年   496篇
  2015年   306篇
  2014年   434篇
  2013年   2461篇
  2012年   374篇
  2011年   341篇
  2010年   347篇
  2009年   293篇
  2008年   304篇
  2007年   311篇
  2006年   293篇
  2005年   247篇
  2004年   277篇
  2003年   243篇
  2002年   255篇
  2001年   330篇
  2000年   341篇
  1999年   260篇
  1998年   147篇
  1997年   191篇
  1996年   184篇
  1995年   129篇
  1994年   142篇
  1993年   123篇
  1992年   205篇
  1991年   188篇
  1990年   220篇
  1989年   217篇
  1988年   186篇
  1987年   198篇
  1986年   175篇
  1985年   219篇
  1984年   163篇
  1983年   133篇
  1982年   131篇
  1981年   113篇
  1980年   117篇
  1979年   180篇
  1978年   138篇
  1977年   114篇
  1976年   92篇
  1975年   94篇
  1974年   99篇
  1973年   100篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Students with autism may struggle to develop the academic skills necessary for success in school and beyond. Understanding and improving academic skills performance requires appropriate measurement approaches. One such option that has been minimally studied with students with autism is curriculum-based measurement (CBM). Coinciding with the need to study different approaches to academic skills measurement for students with autism was the global pandemic which forced a shift to remote service delivery with little warning. While some autistic students struggled with this shift, others thrived, raising questions about how to further support students with autism in virtual formats. The purpose of this study was to examine the feasibility of using remotely administered CBM for autistic students by studying both the practicality and acceptability of this approach. Five students with autism (Grades 2–5) participated in this pilot study, completing reading, math, and writing CBMs at three time points. Student behavior and assessor fidelity were collected to examine practicality; assessor ratings of usability provided insight regarding the acceptability of the approach. Results indicated that remotely administered CBM is feasible for some students with autism: all participants completed the study tasks with minimal behavioral difficulties, and assessor ratings of acceptability were high.  相似文献   
982.
Infant social–emotional development may be impacted by the COVID-19 pandemic. This study investigated associations between maternal pre- and postnatal pandemic-related concerns and social–emotional developmental risk. Data, collected in 2020–2021, came from 220 mothers (87% white, 6% Hispanic, 1% Black, 3% Asian, 1% American Indian, Mage = 32.46 years), and infants (53.18% male, Mage = 12.98 months) in the United States. Maternal postnatal pandemic-related concerns were associated with total risk scores (B = 6.09, p-value <.001) and offspring risk of scoring positive for problems related to inflexibility (B = 4.07, p-value = .006). The total score association was moderated by self-reported social support. Infants may be detrimentally impacted by the pandemic via maternal pandemic-related concerns. Maternal social support may buffer infants.  相似文献   
983.
The perceptions of personal and professional identity development from four Black women counselor educators were examined through a collaborative autoethnography methodology. Themes identified include (a) intentionality of code-switching, (b) inextricable identities, (c) fight for and with authenticity, and (d) mutual development of personal and professional identities.  相似文献   
984.
This paper deals with the problem of constrained stability and tracking of Takagi–Sugeno (T–S) fuzzy positive systems. Linear programming (LP) is used to insert the constraints in the design phase while imposing positivity in closed-loop. The theoretical results are applied to the buck DC–DC converter which is widely used in the photovoltaic generators. Based on the simulation results success of the method is shown for this application.  相似文献   
985.
This study investigates the antecedents and consequences of team learning, which is composed of information acquisition, dissemination, and implementation, in information technology (IT) implementation projects. By investigating 129 IT implementation project teams, we found that (1) information acquisition and information dissemination have a positive impact on project outcomes, such as speed-to-users, lower implementation cost, and operational effectiveness, and (2) team behavior and enabler variables, such as teamwork, team communication, interpersonal trust between team members, team commitment, and senior manager support, positively influence team learning. We also found that team anxiety moderates the relationship between team learning and project outcomes.  相似文献   
986.
987.
Droplet-based microfluidics has gained extensive research interest as it overcomes several challenges confronted by conventional single-phase microfluidics. The mixing performance inside droplets/slugs is critical in many applications such as advanced material syntheses and in situ kinetic measurements. In order to understand the effects of operating conditions on the mixing performance inside liquid slugs generated by a microfluidic T-junction, we have adopted the volume of fluid method coupled with the species transport model to study and quantify the mixing efficiencies inside slugs. Our simulation results demonstrate that an efficient mixing process is achieved by the intimate collaboration of the twirling effect and the recirculating flow. Only if the reagents are distributed transversely by the twirling effect, the recirculating flow can bring in convection mechanism thus facilitating mixing. By comparing the mixing performance inside slugs at various operating conditions, we find that slug size plays the key role in influencing the mixing performance as it determines the amount of fluid to be distributed by the twirling effect. For the cases where short slugs are generated, the mixing process is governed by the fast convection mechanism because the twirling effect can distribute the fluid to the flow path of the recirculating flow effectively. For cases with long slugs, the mixing process is dominated by the slow diffusion mechanism since the twirling effect is insufficient to distribute the large amount of fluid. In addition, our results show that increasing the operating velocity has limited effects on improving the mixing performance. This study provides the insight of the mixing process and may benefit the design and operations of droplet-based microfluidics.  相似文献   
988.
Shear stress is the major mechanical force applied on vascular endothelial cells by blood flow, and is a crucial factor in normal vascular physiology and in the development of some vascular pathologies. The exact mechanisms of cellular mechano-transduction in mammalian cells and tissues have not yet been elucidated, but it is known that mechanically sensitive receptors and ion channels play a crucial role. This paper describes the use of a novel and efficient microfluidic device to study mechanically-sensitive receptors and ion channels in vitro, which has three independent channels from which recordings can be made and has a small surface area such that fewer cells are required than for conventional flow chambers. The contoured channels of the device enabled examination of a range of shear stresses in one field of view, which is not possible with parallel plate flow chambers and other previously used devices, where one level of flow-induced shear stress is produced per fixed flow-rate. We exposed bovine aortic endothelial cells to different levels of shear stress, and measured the resulting change in intracellular calcium levels ([Ca2+]i) using the fluorescent calcium sensitive dye Fluo-4AM. Shear stress caused an elevation of [Ca2+]i that was proportional to the level of shear experienced. The response was temperature dependant such that at lower temperatures more shear stress was required to elicit a given level of calcium signal and the magnitude of influx was reduced. We demonstrated that shear stress-induced elevations in [Ca2+]i are largely due to calcium influx through the transient receptor potential vanilloid type 4 ion channel.  相似文献   
989.
This study proposes a novel cell collection method based on collagenase treatment and ultrasonic vibration. The method collects calf chondrocytes from a reusable metal cell culture substrate. To develop our concept, we calculated the natural vibration modes of the cell culture substrate by a finite element method, and conducted eigenvalue and piezoelectric-structural analyses. Selecting the first out-of-plane vibration mode of the substrate, which has a single nodal circle, we designed and fabricated the cell collection device. The excited vibration mode properly realized our intentions. We then evaluated the cell collection ratio and the growth response, and observed the morphology of the collected cells. The collagenase and ultrasonic vibration treatment collected comparable numbers of cells to conventional trypsin and pipetting treatment, but improved the proliferating cell statistics. Morphological observations revealed that the membranes of cells collected by the proposed method remain intact; consequently, the cells are larger and rougher than cells collected by the conventional method. Therefore, we present a promising cell collection method for adhesive cell culturing process.  相似文献   
990.
Inconsistent response patterns have been used with other measures to screen for child maltreatment. To date the inconsistency (IC) scale, a validity scale on the Child Abuse Potential (CAP) Inventory, has not been used as a screening criterion for physical child abuse. The present study examined the responses of 89 physical child abusers and 108 comparison subjects to determine if the CAP Inventory IC scale has any utility in the screening for physical child abuse. While results indicated the CAP Inventory IC scale scores were significantly higher for the physical child abuse group, a series of discriminant analyses indicated that the IC scale did not account for any meaningful variance after variance related to child abuse factors was removed. Further, the results indicated that dependence on the IC scale alone for physical child abuse screening purposes could be expected to produce excessive false positive and false negative classifications.  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