全文获取类型
收费全文 | 16969篇 |
免费 | 189篇 |
国内免费 | 125篇 |
专业分类
教育 | 11164篇 |
科学研究 | 2110篇 |
各国文化 | 158篇 |
体育 | 2045篇 |
综合类 | 21篇 |
文化理论 | 115篇 |
信息传播 | 1670篇 |
出版年
2021年 | 139篇 |
2020年 | 230篇 |
2019年 | 322篇 |
2018年 | 453篇 |
2017年 | 429篇 |
2016年 | 404篇 |
2015年 | 273篇 |
2014年 | 351篇 |
2013年 | 2826篇 |
2012年 | 337篇 |
2011年 | 356篇 |
2010年 | 307篇 |
2009年 | 315篇 |
2008年 | 316篇 |
2007年 | 278篇 |
2006年 | 306篇 |
2005年 | 259篇 |
2004年 | 494篇 |
2003年 | 432篇 |
2002年 | 419篇 |
2001年 | 513篇 |
2000年 | 340篇 |
1999年 | 257篇 |
1998年 | 170篇 |
1997年 | 166篇 |
1996年 | 168篇 |
1995年 | 164篇 |
1994年 | 152篇 |
1993年 | 159篇 |
1992年 | 253篇 |
1991年 | 224篇 |
1990年 | 236篇 |
1989年 | 239篇 |
1988年 | 192篇 |
1987年 | 221篇 |
1986年 | 210篇 |
1985年 | 235篇 |
1984年 | 200篇 |
1983年 | 211篇 |
1982年 | 188篇 |
1981年 | 149篇 |
1980年 | 162篇 |
1979年 | 226篇 |
1978年 | 173篇 |
1977年 | 150篇 |
1976年 | 157篇 |
1975年 | 117篇 |
1974年 | 139篇 |
1973年 | 126篇 |
1971年 | 115篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Robert P. Holley 《图书馆管理杂志》2015,55(7):595-603
Teaching the introductory LIS management course may be the most challenging assignment for LIS professors because of the breadth of the subject, the probabilistic nature of management principles, and the differing management environments of LIS organizations. The best teaching strategy is to describe honestly to students the benefits and limitations of the course and to focus on the achievable objectives of introducing students to core management concepts, providing skill enhancement, and encouraging them to evaluate their management potential. The article discusses the difficulties of teaching leadership skills, the limits imposed by student competencies, and the impact of the professor's background on course content. 相似文献
992.
993.
The tablet computer offers options for streaming TV programming that potentially alters viewing behaviors compared to the traditional television set, yet there is a dearth of research related to this viewing alternative. This study uses a national sample of adult iPad owners to investigate the tablet's role as a TV. The frameworks of continuity-discontinuity, use-diffusion, and attention and absorption to programming are applied to uncover where the tablet fits into the current repertoire of viewing devices, and how individuals are engaging with traditional TV programming through it. Results show that overall, the tablet's functionality as a TV can lead to experiential differences. 相似文献
994.
Recent years have witnessed a strong trend towards analysis of single-cells. To access and handle single-cells, many new tools are needed and have partly been developed. Here, we present an improved version of a single-cell printer which is able to deliver individual single cells and beads encapsulated in free-flying picoliter droplets at a single-bead efficiency of 96% and with a throughput of more than 10 beads per minute. By integration of acoustophoretic focusing, the cells could be focused in x and y direction. This way, the cells were lined-up in front of a 40 μm nozzle, where they were analyzed individually by an optical system prior to printing. In agreement with acoustic simulations, the focusing of 10 μm beads and Raji cells has been achieved with an efficiency of 99% (beads) and 86% (Raji cells) to a 40 μm wide center region in the 1 mm wide microfluidic channel. This enabled improved optical analysis and reduced bead losses. The loss of beads that ended up in the waste (because printing them as single beads arrangements could not be ensured) was reduced from 52% ± 6% to 28% ± 1%. The piezoelectric transducer employed for cell focusing could be positioned on an outer part of the device, which proves the acoustophoretic focusing to be versatile and adaptable. 相似文献
995.
A. Hokkanen I. Stuns P. Schmid A. Kokkonen F. Gao A. Steinecker J. Budczies P. Heimala L. Hakalahti 《Biomicrofluidics》2015,9(5)
We have developed a microfluidics based sampling system for tissue analytics. The proof-of-concept of the sampling system was demonstrated by extracting lipid samples from tissue biopsies. The sample collection system consists of a disposable silicon based multiport microneedle integrated with polymer microfluidics. The polymethyl methacrylate polymer microfluidic chip has a 10 μl sample reservoir and actuation membranes for liquid pumping. A special automated robotic system was developed to control the positioning of the needle and the sampling procedure on preselected spots on the tissue. Real breast cancer tissue samples were used to test the feasibility of the sampling system. We successfully measured indicative cancer biomarkers from the tissue surface. Phosphatidylcholine and phosphoethanolamine were extracted from the tissue membrane with methyl tert-butyl ether solvent and detected by mass spectrometry. In the future, this tool could be used in characterization of preoperative biopsies and tumour tissues removed during surgery. 相似文献
996.
A. Zaher S. Li K. T. Wolf F. N. Pirmoradi O. Yassine L. Lin N. M. Khashab J. Kosel 《Biomicrofluidics》2015,9(5)
Implantable drug delivery systems can provide long-term reliability, controllability, and biocompatibility, and have been used in many applications, including cancer pain and non-malignant pain treatment. However, many of the available systems are limited to zero-order, inconsistent, or single burst event drug release. To address these limitations, we demonstrate prototypes of a remotely operated drug delivery device that offers controllability of drug release profiles, using osmotic pumping as a pressure source and magnetically triggered membranes as switchable on-demand valves. The membranes are made of either ethyl cellulose, or the proposed stronger cellulose acetate polymer, mixed with thermosensitive poly(N-isopropylacrylamide) hydrogel and superparamagnetic iron oxide particles. The prototype devices'' drug diffusion rates are on the order of 0.5–2 μg/h for higher release rate designs, and 12–40 ng/h for lower release rates, with maximum release ratios of 4.2 and 3.2, respectively. The devices exhibit increased drug delivery rates with higher osmotic pumping rates or with magnetically increased membrane porosity. Furthermore, by vapor deposition of a cyanoacrylate layer, a drastic reduction of the drug delivery rate from micrograms down to tens of nanograms per hour is achieved. By utilizing magnetic membranes as the valve-control mechanism, triggered remotely by means of induction heating, the demonstrated drug delivery devices benefit from having the power source external to the system, eliminating the need for a battery. These designs multiply the potential approaches towards increasing the on-demand controllability and customizability of drug delivery profiles in the expanding field of implantable drug delivery systems, with the future possibility of remotely controlling the pressure source. 相似文献
997.
Mark P. Moresi Elizabeth J. Bradshaw David A. Greene Geraldine A. Naughton 《Journal of sports sciences》2015,33(2):180-191
Double-leg repeated jumping tasks are commonly used as measures of lower limb stiffness in exercise science research. Within similar stiffness calculations, variation in data-reduction criteria exists. The impact of these varied data-reduction methods on stiffness measures is unknown. Sixteen adolescent female participants from varied physical activity backgrounds performed 15 self-paced, bent-knee continuous jumps (CJb) on two force plates. Leg stiffness was calculated as the ratio of the peak force and the centre of mass displacement for each contact. Using combinations of criteria based on previous literature, 83 data-reduction methods were applied to the raw data. Data reduction suitability was assessed based on intra-trial reliability, the number of participants excluded and the average contacts excluded. Four data-reduction methods were deemed suitable for use with adolescent female populations, with three consecutive contacts within 1 SD of the average jump frequency considered optimal. The average individual stiffness values were not greatly influenced by the data-reduction method; however, for a single participant, a stiffness change of up to 6 kN · m?1 (30%) was observed. The role and potential impact of data-reduction methods used to evaluate measures of lower limb stiffness during repeated jumping tasks warrants consideration. 相似文献
998.
Marisa L. Conte Mark P. MacEachern Nandita S. Mani Whitney A. Townsend Judith E. Smith Chase Masters Caitlin Kelley 《Journal of the Medical Library Association》2015,103(2):69-73
Objective:The researchers used the flipped classroom model to develop and conduct a systematic review course for librarians.Setting:The research took place at an academic health sciences library.Method:A team of informationists developed and conducted a pilot course. Assessment informed changes to both course components; a second course addressed gaps in the pilot.Conclusion:The flipped classroom model can be successful in developing and implementing a course that is well rated by students. 相似文献
999.
1000.
Presidential election campaigns provide opportunities for parents to socialize their children to become politically engaged citizens. However, news coverage of the 2016 U.S. presidential campaign contained inappropriate content, leading parents to possibly restrict or denigrate rather than encourage child campaign news consumption. This study built on literatures in political socialization and parental mediation to explore mediation of campaign news coverage. Data from a representative sample of American parents during the Autumn of 2016 revealed that co-viewing, active mediation, and restrictive mediation were relatively common. The predictors of mediation included political variables, parenting orientations, and child factors, with the latter two often interacting with one another. The results have implications for how we conceptualize both political socialization and parental mediation. 相似文献