全文获取类型
收费全文 | 8265篇 |
免费 | 116篇 |
国内免费 | 3篇 |
专业分类
教育 | 5770篇 |
科学研究 | 996篇 |
各国文化 | 87篇 |
体育 | 523篇 |
综合类 | 2篇 |
文化理论 | 57篇 |
信息传播 | 949篇 |
出版年
2021年 | 75篇 |
2020年 | 104篇 |
2019年 | 174篇 |
2018年 | 228篇 |
2017年 | 205篇 |
2016年 | 204篇 |
2015年 | 128篇 |
2014年 | 172篇 |
2013年 | 1510篇 |
2012年 | 176篇 |
2011年 | 163篇 |
2010年 | 147篇 |
2009年 | 151篇 |
2008年 | 166篇 |
2007年 | 128篇 |
2006年 | 135篇 |
2005年 | 120篇 |
2004年 | 136篇 |
2003年 | 99篇 |
2002年 | 102篇 |
2001年 | 136篇 |
2000年 | 132篇 |
1999年 | 116篇 |
1998年 | 78篇 |
1997年 | 79篇 |
1996年 | 87篇 |
1995年 | 68篇 |
1994年 | 60篇 |
1993年 | 97篇 |
1992年 | 115篇 |
1991年 | 119篇 |
1990年 | 123篇 |
1989年 | 99篇 |
1988年 | 93篇 |
1987年 | 111篇 |
1986年 | 95篇 |
1985年 | 105篇 |
1984年 | 96篇 |
1983年 | 98篇 |
1982年 | 100篇 |
1981年 | 83篇 |
1980年 | 80篇 |
1979年 | 104篇 |
1978年 | 94篇 |
1977年 | 90篇 |
1976年 | 79篇 |
1974年 | 70篇 |
1973年 | 65篇 |
1972年 | 55篇 |
1971年 | 58篇 |
排序方式: 共有8384条查询结果,搜索用时 15 毫秒
61.
Educational Freedom in an Age of Anxiety . Twelfth Yearbook of the John Dewey Society, ed.
Freedom, Power, and democratic Planning . By K. Mannheim, Internat. Lib. of Sociol. & Soc. Reconstr.
Improving Teaching-Learning Processes . By Ray H. Simpson. 相似文献
Freedom, Power, and democratic Planning . By K. Mannheim, Internat. Lib. of Sociol. & Soc. Reconstr.
Improving Teaching-Learning Processes . By Ray H. Simpson. 相似文献
62.
63.
64.
E.F. George 《Journal of The Franklin Institute》1951,252(6):493-500
From the reports of the CRPL, average yearly values of h′E, h′F1,f °E and NF1, for the months of January, March, June, July, September, and December of the years 1944 to 1949 were computed and plotted against the magnetic latitude. Altogether some 25,000 individual records were averaged. Seven curves were plotted. They showed that: (1) all curves are symmetrical with respect to the magnetic equator; (2) the h′E, h′F1, f0E and the NF, curves all swing up and down as the magnetic latitude, north and south, increases; (3) the h′E is definitely periodic with constant period and constant amplitude; (4) the h′E curve rises only slightly (on the average) with latitude. These results appear to be inconsistent with the ultraviolet light theory of ionization. 相似文献
65.
66.
67.
Charles F. Kettering 《Journal of The Franklin Institute》1951,251(1):109-119
Nearly all prognostigators, from the fellow who buys a $2 ticket on Blue Boy to the financial policy-makers of government and business, base their final conclusions upon past experience. Properly tempered (and herein lies the success or failure of the prophet), this is a completely logical procedure, and is especially applicable to engineering trends, for most of our technical progress has been achieved through a process of evolution.Thus, one of the best ways to gain an insight as to the direction in which we're going is to note our present position and to review how we reached it.In the preceding discussion, I have tried to cover a few specific phases of our transportation future in just this fashion, in order to emphasize that we can expect tomorrow further applications and extensions of the things we are working with today. 相似文献
68.
From the standpoint of circuit synthesis as well as for a fundamental comprehension of circuit behavior, it is desirable to be able to visualize the response of a circuit over an extended frequency range by means of a geometrical construction. Mathematically, the response of a circuit can be expressed with the La Place transform theory as a function of the complex frequency variable, p = α + jωw, in which a is the decrement and ω is the “real” angular frequency. Physically, the nature of the real-frequency response is usually not discernible by casual inspection of the mathematical function. This paper develops a means of visualizing this frequency response readily through the construction of a vector diagram from the response function. 相似文献
69.
70.