全文获取类型
收费全文 | 3342篇 |
免费 | 16篇 |
专业分类
教育 | 2349篇 |
科学研究 | 556篇 |
各国文化 | 5篇 |
体育 | 97篇 |
综合类 | 7篇 |
文化理论 | 63篇 |
信息传播 | 281篇 |
出版年
2022年 | 8篇 |
2021年 | 26篇 |
2020年 | 13篇 |
2019年 | 25篇 |
2018年 | 74篇 |
2017年 | 125篇 |
2016年 | 184篇 |
2015年 | 125篇 |
2014年 | 67篇 |
2013年 | 161篇 |
2012年 | 162篇 |
2011年 | 176篇 |
2010年 | 90篇 |
2009年 | 43篇 |
2008年 | 75篇 |
2007年 | 67篇 |
2006年 | 57篇 |
2005年 | 690篇 |
2004年 | 480篇 |
2003年 | 304篇 |
2002年 | 137篇 |
2001年 | 72篇 |
2000年 | 37篇 |
1999年 | 30篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 5篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1969年 | 2篇 |
1967年 | 3篇 |
1935年 | 2篇 |
排序方式: 共有3358条查询结果,搜索用时 15 毫秒
41.
IPv4, the workhorse protocol of the currently popular TCP/ IP protocol suite, is fast becoming obsolete. The exponential growth
of the Internet is the main reason that has required the creation of the next generation of Internet Protocol-IPv6. IPv6 is
much more flexible and promises to take care of the address space and security issues in the foreseeable future.
Part 1 of the paper lays the foundation of the various issues involved in designing the Internet Protocol and motivates the
need for an upgraded version of this protocol. 相似文献
42.
43.
In many Western science systems, funding structures increasingly stimulate academic research to contribute to practical applications,
but at the same time the rise of bibliometric performance assessments have strengthened the pressure on academics to conduct
excellent basic research that can be published in scholarly literature. We analyze the interplay between these two developments
in a set of three case studies of fields of chemistry in the Netherlands. First, we describe how the conditions under which
academic chemists work have changed since 1975. Second, we investigate whether practical applications have become a source
of credibility for individual researchers. Indeed, this turns out to be the case in catalysis, where connecting with industrial
applications helps in many steps of the credibility cycle. Practical applications yield much less credibility in environmental
chemistry, where application-oriented research agendas help to acquire funding, but not to publish prestigious papers or to
earn peer recognition. In biochemistry practical applications hardly help in gaining credibility, as this field is still strongly
oriented at fundamental questions. The differences between the fields can be explained by the presence or absence of powerful
upstream end-users, who can afford to invest in academic research with promising long term benefits. 相似文献
44.
45.
根据《棋经十三篇》这一部棋书,通过分析,看到了《棋经》与《孙子》的关系甚为密切,它不仅从篇章款式上摹拟《孙子十三篇》,而更是从有关棋的战略战术等内容问题上与《孙子十三篇》相吻合。因此。棋道如兵法。棋理合乎一般事物之辩证法则。 相似文献
46.
Sudhir Kurl Sae Young Jae Timo H.Makikallio Ari Voutilainen Magnus J.Hagnas Jussi Kauhanen Jari A.Laukkanen 《运动与健康科学(英文)》2022,11(2):266-271
Background:Little is known about exercise cardiac power(ECP),defined as the ratio of directly measured maximal oxygen uptake with peak systolic blood pressure during exercise,on heart failure(HF)risk.We examined the association of ECP and the risk of HF.Methods:This was a population-based cohort study of 2351 men from eastern Finland.The average time to follow-up was 25 years.Participants participated at baseline in an exercise stress test.A total of 313 cases of HF occurred.Results:Men with low ECP(<9.84 mL/mmHg,the lowest quartile)had a 2.37-fold(95%confidence interval(95%CI):1.68-3.35,p<0.0001)hazards ratio of HF as compared with men with high ECP(>13.92 mL/mmHg,the highest quartile),after adjusting for age.Low ECP was associated with a 1.96-fold risk(95%CI:1.38-2.78,p<0.001)of HF after additional adjustment for conventional risk factors.After further adjustment for left ventricular hypertrophy,the results hardly changed(hazards ratio=1.87,95%CI:1.31-2.66,p<0.001).One SD increase in ECP(3.16 mL/mmHg)was associated with a decreased risk of HF by 28%(95%CI:17%-37%).Conclusion:ECP provides a noninvasive and easily available measure from cardiopulmonary exercise tests in predicting HF.However,ECP did not provide additional value over maximal oxygen uptake. 相似文献
47.
Keith?KoenigEmail author Nan?Davis?Mitchell Thomas?E.?Hannigan J.?Keith?Clutter 《Sports Engineering》2004,7(2):105-117
The speed at which a player can swing a bat is central to the games of baseball and softball, determining, to a large extent,
the hit speed of the ball. Experimental and analytical studies of bat swing speed were conducted with particular emphasis
on the influence of bat moment of inertia on swing speed. Two distinct sets of experiments measured the swing speed of colege
baseball and fast-pitch softball players using weighted rods and modified bats. The swing targets included flexible targets,
balls on a tee and machine pitched balls. Internal mass alterations provided a range of inertial properties. The average measured
speeds, from 22 to 31 m s−1, are consistent with previous studies. Bat speed approximately correlates with the moment of inertia of the bat about a vertical
axis of rotation through the batter's body, the speed generally decreasing as this moment of inertia increases. The analytical
model assumes pure rotation of the batter/bat system about a vertical axis through the batter's body. Aerodynamic drag of
the batter's arms and the bat is included in the model. The independent variable is bat moment of inertia about the rotation
axis. There is reasonable agreement between the model and the measured speeds. Detailed differences between the two suggest
the importance of additional degrees of freedom in determining swing speed. 相似文献
48.
Institutions of higher education are looked to by society as the training grounds and gatekeepers for college-trained workers.
However, despite a long history of being viewed by many as unresponsive to labor force needs, the academy has not found ways
of effectively meeting these demands, nor articulating why it is that they have difficulty doing so. This paper discusses
how institutional researchers can help explain to campus administrators and others the role that institutions play in training
individuals for the workplace, and why they cannot always quickly respond to and solve shortages of college-trained workers.
The first section outlines what economic theory and research has to say regarding labor markets, how labor market shortages
arise, and how students make decisions about which major to pursue. The last section describes problems institutional researchers
face when using their skills with data to identify solutions to this problem. Using data from the state of New Hampshire,
it will be shown that the data available to institutional decisionmakers can be out of date, inaccurate, and not particularly
useful for designing policies that would enable an institution to respond to the labor needs of the economy. 相似文献
49.
The theory of the multiple intelligences are discussed in relation to working with young children and young children with disabilities. A rationale for the use of the multiple intelligences is discussed as well as practical suggestions on how they can be incorporated into early childhood programs. 相似文献
50.
Patricia?OdellEmail author Kathleen?Korgen Gabe?Wang 《Innovative Higher Education》2005,29(4):291-305
This study examined the effectiveness of curriculum-focused diversity initiatives on a college campus by determining the relationships between GPA, social class, year in school, residential status, racial diversity courses taken, and cross-racial friendships on the level of social distance between Whites-Blacks, Whites-Hispanics, Hispanics-Whites, Hispanics-Blacks, Blacks-Whites, and Blacks-Hispanics. The data suggest that, while the institution does a good job of bringing diverse groups of students to the campus, it does not effectively reduce the level of social distance among many members of the different racial groups on campus. Using the Intergroup Contact Hypothesis, the article concludes by suggesting means by which social distance among racial groups on campus might be decreased. 相似文献