全文获取类型
收费全文 | 15997篇 |
免费 | 191篇 |
国内免费 | 119篇 |
专业分类
教育 | 11020篇 |
科学研究 | 2086篇 |
各国文化 | 111篇 |
体育 | 1360篇 |
综合类 | 12篇 |
文化理论 | 123篇 |
信息传播 | 1595篇 |
出版年
2021年 | 115篇 |
2020年 | 218篇 |
2019年 | 313篇 |
2018年 | 439篇 |
2017年 | 381篇 |
2016年 | 399篇 |
2015年 | 250篇 |
2014年 | 328篇 |
2013年 | 2751篇 |
2012年 | 312篇 |
2011年 | 343篇 |
2010年 | 255篇 |
2009年 | 248篇 |
2008年 | 261篇 |
2007年 | 289篇 |
2006年 | 282篇 |
2005年 | 278篇 |
2004年 | 265篇 |
2003年 | 248篇 |
2002年 | 246篇 |
2001年 | 260篇 |
2000年 | 279篇 |
1999年 | 280篇 |
1998年 | 148篇 |
1997年 | 154篇 |
1996年 | 194篇 |
1995年 | 173篇 |
1994年 | 140篇 |
1993年 | 152篇 |
1992年 | 222篇 |
1991年 | 228篇 |
1990年 | 238篇 |
1989年 | 264篇 |
1988年 | 217篇 |
1987年 | 233篇 |
1986年 | 230篇 |
1985年 | 262篇 |
1984年 | 230篇 |
1983年 | 218篇 |
1982年 | 181篇 |
1981年 | 174篇 |
1980年 | 164篇 |
1979年 | 249篇 |
1978年 | 198篇 |
1977年 | 190篇 |
1976年 | 155篇 |
1975年 | 136篇 |
1974年 | 151篇 |
1973年 | 136篇 |
1971年 | 120篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
Neuropsychology of Early-treated Phenylketonuria: Specific Executive Function Deficits 总被引:14,自引:0,他引:14
Marilyn C. Welsh Bruce F. Pennington Sally Ozonoff Bobbye Rouse Edward R. B. McCabe 《Child development》1990,61(6):1697-1713
This study explored the hypothesis that children with early-treated phenylketonuria (PKU) are selectively impaired on executive function measures, even when still on diet. The rationale for this hypothesis is that even mild elevations in phenylalanine (Phe) can lead to lower central levels of biogenic amines, including dopamine (DA). We hypothesize that this mild DA depletion causes subtle prefrontal dysfunction, which in turn affects executive functions such as set maintenance, planning, and organized search. 11 preschool early-treated PKU children (M age = 4.64) and a sample of age- and IQ-matched unaffected peers (n = 11) were evaluated on a battery of executive function (EF) measures. In addition, a "non-executive function" task, recognition memory, was administered to all subjects. Group comparisons demonstrated that PKU children were significantly impaired on an executive function composite score; there were no group differences, however, in recognition memory. These results supported the hypothesized specific deficit in executive function. Furthermore, within the PKU group the executive function composite score was significantly negatively correlated with concurrent phenylalanine levels, even after controlling for the correlation between IQ and executive function skills. This second finding provides support for the proposed biochemical mechanism underlying the specific cognitive deficits. 相似文献
982.
Audiences,metaphors, and the Persian Gulf war 总被引:1,自引:0,他引:1
Benjamin R. Bates 《Communication Studies》2013,64(3):447-463
This paper examines George Bush's Persian Gulf war addresses as a representative anecdote of Bush's campaign to build an international military coalition. The paper argues that in war rhetoric international audiences should be considered. A theorization of the international audience is offered. George Bush's public speeches are then analyzed as they use two metaphoric clusters. The SAVAGE cluster is used to justify a response to Iraq's 1990 invasion of Kuwait. The CIVILIZATION cluster is used to justify an American‐led military response. The metaphoric clusters are shown to be persuasive to the international audience as they are adopted and recirculated by this audience. Conclusions and implications of the interaction of these two metaphoric clusters for future war rhetoric are offered. 相似文献
983.
Edgard B. Cornachione Maria R. Trombetta Silvia P.C. Casa Nova 《Studies in Educational Evaluation》2010,36(1-2):69-81
To what extent does the intense and direct involvement of internal stakeholders, such as program managers and staff members, play a significant role toward evaluation use? Stakeholder involvement is a key element in evaluation and evaluation use is considered within a broader sense that includes organizational knowledge, individual skills, and immediate program reviews. The background of this new non-degree online program is directly related to the Brazilian socioeconomic, cultural, and educational framework. Conclusions include 12 major claims related to program evaluation and an integrative approach involving Patton's and Stake's evaluation theories. Although delimited by the natural boundaries of a case study design, conclusions may benefit the strategic discussion of program evaluation in similar situations, at both professional and academic levels. 相似文献
984.
985.
Financial problems at colleges and universities have led many institutions to initiate extra efforts to obtain extramural funds. One such effort has been the establishment of formula-based research incentive plans. These plans generally utilize the recovery of indirect costs as the basis for allocating additional incentive funds to various areas as an encouragement to obtain additional extramural funds. Data from surveys conducted by the University of Missouri-Kansas City and Ohio University were combined with National Science Foundation reports to provide information about this relatively recent phenomena. The increasing popularity of these plans was shown in that a majority of institutions had such plans in effect during FY 1979. Analyses of the effectiveness of these plans showed no statistically significant differences between institutions with incentive plans and those without such plans, although mean federal research expenditures were approximately 20% greater at those institutions without these incentive plans. The evidence presented indicates that the receipt of federal research funds is not associated with the use of a formula-based research incentive plan. 相似文献
986.
Julie K. Snyder Gerald W. McLaughlin James R. Montgomery 《Research in higher education》1991,32(1):45-58
What factors contribute to high-quality funded research activity in research universities? What do these institutions have in common? What management strategies do they employ to encourage funded research excellence and activity? In this period of decreased or level government spending, competition for grants among research universities becomes fierce. In order to stay competitive, it is important to know what works in research management. Preliminary research has allowed us to provide some answers and to clarify some key questions on what makes a successful research program. 相似文献
987.
988.
María Dolores Robles-Ortega Francisco R. Feito Juan J. Jiménez Rafael J. Segura 《Journal of Cultural Heritage》2012,13(3):326-331
Nowadays, some virtual museums include 3D room scenes to show the models of its pieces, just like in real museums. Nevertheless, the generation and maintenance of this kind of scenes is generally difficult and should be done by an expert. For example, any change such as including a new piece or modifying the position of an existing fragment usually requires a different design and the creation of a new scene. In this paper we present a case study on the development of a web-based application to automatize this process. To this end, a database to store both graphic and non-graphic information about the pieces, and some 3D rooms to show them has been created. The designed scenes only contain some pieces of furniture to exhibit the fragments, which will be subsequently included. Thus, when a room is loaded in the web page, its associated pieces are obtained through a query in the database and its models are dynamically included in the original scene. Therefore, the position changes or the inclusion of new pieces are not performed in the 3D model, but in the database. Our application makes the transmission of the knowledge to the general public easier because any new discovered piece can be included in a existing museum effortlessly. 相似文献
989.
This study compares the instrumentation and analysis techniques used when determining the power expended pedalling a rope-braked
ergometer manufactured by Monark (Sweden) during a low intensity test. Power values were generated by eight subjects. The
instrumentation consisted of load cells to measure the rope brake forces, a tachometer to measure the flywheel velocity and
instrumented pedal cranks manufactured by Schoberer Rad Messtechnik (SRM). The subjects pedalled a rope-braked ergometer at
60 rev min-1, against a resistance of 3 kg, for 5 minutes. Three different measurements of the mean power were recorded and these were
compared with the value given by Monark. The SRM cranks provided two sets of results using different software packages supplied
with the cranks. SRM standard software is used for taking measurements during training and cycle races over long time periods.
An additional piece of software is provided by SRM called Ptnew, which gives readings of torque and pedal cadence over periods
up to 30 seconds. Using the values supplied by Monark each subject generated 180 W of power. The mean power for the eight
subjects, measured using the SRM cranks, was 170.36 W (SD 4.11) using the alternative SRM software (Ptnew) over a 30 second
period and 173.68 W (SD 2.21) using the standard SRM software. From the direct measurement of the brake forces and flywheel
velocity the mean power across the eight subjects was 148.90 W (SD 5.89). The SRM cranks measure the input power, whereas
the direct measurement system measures the power output excluding mechanical losses. These values give a figure for the mechanical
efficiency for the roped-braked ergometer of 88%. It was found that Monark overestimates the power generated by the subjects
when compared with both the SRM systems and the direct measurement instrumentation. 相似文献
990.
Background: Systematic review articles support the advance of science and translation of research evidence into healthcare practice. Inaccurate retrieval from medline could limit access to reviews. Objective: To determine the quality of indexing systematic reviews and meta‐analyses in medline . Methods: The Clinical Hedges Database, containing the results of a hand search of 161 journals, was used to test medline indexing terms for their ability to retrieve systematic reviews that met predefined methodologic criteria (labelled as ‘pass’ review articles) and reviews that reported a meta‐analysis. Results: The Clinical Hedges Database contained 49 028 articles; 753 were ‘pass’ review articles (552 with a meta‐analysis). In total 758 review articles (independent of whether they passed) reported a meta‐analysis. The search strategy that retrieved the highest number of ‘pass’ systematic reviews achieved a sensitivity of 97.1%. The publication type ‘meta analysis’ had a false positive rate of 5.6% (95% CI 3.9 to 7.6), and false negative rate of 0.31% (95% CI 0.26 to 0.36) for retrieving systematic reviews that reported a meta‐analysis. Conclusions: Inaccuracies in indexing systematic reviews and meta‐analyses in medline can be partly overcome by a 5‐term search strategy. Introducing a publication type for systematic reviews of the literature could improve retrieval performance. 相似文献