全文获取类型
收费全文 | 46396篇 |
免费 | 97篇 |
国内免费 | 117篇 |
专业分类
系统科学 | 366篇 |
丛书文集 | 1082篇 |
教育与普及 | 118篇 |
理论与方法论 | 258篇 |
现状及发展 | 20426篇 |
研究方法 | 1757篇 |
综合类 | 21904篇 |
自然研究 | 699篇 |
出版年
2013年 | 292篇 |
2012年 | 585篇 |
2011年 | 1333篇 |
2010年 | 265篇 |
2008年 | 762篇 |
2007年 | 807篇 |
2006年 | 863篇 |
2005年 | 856篇 |
2004年 | 787篇 |
2003年 | 838篇 |
2002年 | 774篇 |
2001年 | 1361篇 |
2000年 | 1251篇 |
1999年 | 812篇 |
1992年 | 803篇 |
1991年 | 681篇 |
1990年 | 718篇 |
1989年 | 668篇 |
1988年 | 696篇 |
1987年 | 712篇 |
1986年 | 691篇 |
1985年 | 865篇 |
1984年 | 704篇 |
1983年 | 590篇 |
1982年 | 495篇 |
1981年 | 513篇 |
1980年 | 668篇 |
1979年 | 1431篇 |
1978年 | 1220篇 |
1977年 | 1208篇 |
1976年 | 880篇 |
1975年 | 998篇 |
1974年 | 1374篇 |
1973年 | 1208篇 |
1972年 | 1230篇 |
1971年 | 1484篇 |
1970年 | 1946篇 |
1969年 | 1506篇 |
1968年 | 1368篇 |
1967年 | 1451篇 |
1966年 | 1256篇 |
1965年 | 908篇 |
1964年 | 245篇 |
1959年 | 572篇 |
1958年 | 850篇 |
1957年 | 669篇 |
1956年 | 573篇 |
1955年 | 503篇 |
1954年 | 561篇 |
1948年 | 334篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
This is a contribution towards a history and philosophy of modeling in its early stages in electromagnetism. In 1873, James Clerk Maxwell (1831–1879) hinted at the methodology of modeling at the end of his Treatise on Electricity and Magnetism. We focus on Maxwell's impact on physicists who immediately followed him, specifically Oliver Lodge (1851–1940) and George Francis FitzGerald (1851–1901). We begin with the role that the scientific concept of model played in the late nineteenth century, as assessed by Ludwig Boltzmann (1844–1906). We then discuss the role of hypothesis as a methodology, the appeal to (dynamical) illustration, and the way Maxwell applied model and working model in his studies of electromagnetism. We show that for Maxwell these key terms were kept distinct, but Lodge did not maintain these distinctions and, in this regard, FitzGerald followed Lodge. Notwithstanding Lodge's influence, Fitzgerald modified Maxwell's theory based on the mechanical model he designed, thereby implicitly taking the first step towards modeling. This methodology consists in drawing consequences from the (mechanical) model to the (electrodynamic) theory and modifying the latter in light of the functioning of the former. At the core of our argument is the thesis that it was a methodological novelty to move from the concept of model to the methodology of modeling. The introduction of modeling as a new methodology into physics in the late nineteenth century was a major event which deserves proper recognition. 相似文献
2.
String theorists are certain that they are practicing physicists. Yet, some of their recent critics deny this. This paper argues that this conflict is really about who holds authority in making rational judgment in theoretical physics. At bottom, the conflict centers on the question: who is a proper physicist? To illustrate and understand the differing opinions about proper practice and identity, we discuss different appreciations of epistemic virtues and explanation among string theorists and their critics, and how these have been sourced in accounts of Einstein's biography. Just as Einstein is claimed by both sides, historiography offers examples of both successful and unsuccessful non-empirical science. History of science also teaches that times of conflict are often times of innovation, in which novel scholarly identities may come into being. At the same time, since the contributions of Thomas Kuhn historians have developed a critical attitude towards formal attempts and methodological recipes for epistemic demarcation and justification of scientific practice. These are now, however, being considered in the debate on non-empirical physics. 相似文献
3.
4.
5.
The shrink proofing on wool with treatment of protease named Argaenzyme STL was studied. The various pretreating auxiliaries, different parameters for protease treating process and the effect of stabilizer were discussed in detail. The varieties of some properties before and after protease treatment were also investigated. 相似文献
6.
7.
8.
9.
10.