全文获取类型
收费全文 | 42009篇 |
免费 | 83篇 |
国内免费 | 116篇 |
专业分类
系统科学 | 392篇 |
丛书文集 | 1022篇 |
教育与普及 | 107篇 |
理论与方法论 | 236篇 |
现状及发展 | 18790篇 |
研究方法 | 1601篇 |
综合类 | 19575篇 |
自然研究 | 485篇 |
出版年
2013年 | 213篇 |
2012年 | 528篇 |
2011年 | 1084篇 |
2010年 | 240篇 |
2008年 | 705篇 |
2007年 | 757篇 |
2006年 | 751篇 |
2005年 | 768篇 |
2004年 | 689篇 |
2003年 | 778篇 |
2002年 | 716篇 |
2001年 | 1287篇 |
2000年 | 1222篇 |
1999年 | 768篇 |
1992年 | 739篇 |
1991年 | 606篇 |
1990年 | 647篇 |
1989年 | 644篇 |
1988年 | 643篇 |
1987年 | 637篇 |
1986年 | 650篇 |
1985年 | 792篇 |
1984年 | 622篇 |
1983年 | 540篇 |
1982年 | 470篇 |
1981年 | 496篇 |
1980年 | 598篇 |
1979年 | 1302篇 |
1978年 | 1116篇 |
1977年 | 1114篇 |
1976年 | 825篇 |
1975年 | 872篇 |
1974年 | 1303篇 |
1973年 | 1053篇 |
1972年 | 1072篇 |
1971年 | 1326篇 |
1970年 | 1765篇 |
1969年 | 1386篇 |
1968年 | 1269篇 |
1967年 | 1331篇 |
1966年 | 1127篇 |
1965年 | 827篇 |
1964年 | 220篇 |
1959年 | 503篇 |
1958年 | 731篇 |
1957年 | 577篇 |
1956年 | 486篇 |
1955年 | 442篇 |
1954年 | 483篇 |
1948年 | 265篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
This article presents a case example involving the renaming of an organizational change process from BPR to outsourcing. The paper discusses the important ramifications of such a name change in that the recognition of outsourcing allowed an organizational commitment to counseling and termination advice. The paper discusses two ways of looking at the name change, one from a critical theory perspective and one from a realist perspective. It demonstrates how theory can provide useful yet markedly different interpretations of such organizational events. Critical theory operates from within what can be termed the transitive epistemological dimension, whereas critical realism tends to emphasize the importance of ontological issues. Each has important things to say about the situation and improves our understanding overall. 相似文献
32.
We develop in this paper an efficient way to select the best subset threshold autoregressive model. The proposed method uses a stochastic search idea. Differing from most conventional approaches, our method does not require us to fix the delay or the threshold parameters in advance. By adopting the Markov chain Monte Carlo techniques, we can identify the best subset model from a very large of number of possible models, and at the same time estimate the unknown parameters. A simulation experiment shows that the method is very effective. In its application to the US unemployment rate, the stochastic search method successfully selects lag one as the time delay and five best models from more than 4000 choices. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
33.
34.
35.
European blackcaps,Sylvia atricapilla, with one breeding season per year, have a single-peaked annual testes cycle. However, African conspecifics from the Cape Verde Islands with two breeding seasons per annum demonstrate a two-peaked cycle. Both population-specific cycles reflect differences in the respective endogenous circannual rhythms. Experimental hybridization of birds of the two populations resulted in an intermediate pattern of testes cycle, thus demonstrating that there are genetic components for some temporal aspects in an avian reproductive cycle. Another characteristic of the African birds, their extremely rapid juvenile development and early sexual maturity (at an age of 5–6 months) proved largely to be a photoperiodic (short-day) effect in birds hatched in autumn. The same effect could also be induced in European conspecifics exposed to correspondingly short day-lengths. 相似文献
36.
37.
38.
39.
40.