全文获取类型
| 收费全文 | 131969篇 |
| 免费 | 7406篇 |
| 国内免费 | 88篇 |
专业分类
| 林业 | 5422篇 |
| 农学 | 4283篇 |
| 基础科学 | 831篇 |
| 16944篇 | |
| 综合类 | 21329篇 |
| 农作物 | 5281篇 |
| 水产渔业 | 6667篇 |
| 畜牧兽医 | 67945篇 |
| 园艺 | 1801篇 |
| 植物保护 | 8960篇 |
出版年
| 2020年 | 1180篇 |
| 2019年 | 1377篇 |
| 2018年 | 2035篇 |
| 2017年 | 2338篇 |
| 2016年 | 2102篇 |
| 2015年 | 1748篇 |
| 2014年 | 2227篇 |
| 2013年 | 5301篇 |
| 2012年 | 4120篇 |
| 2011年 | 5103篇 |
| 2010年 | 3252篇 |
| 2009年 | 3402篇 |
| 2008年 | 4980篇 |
| 2007年 | 4675篇 |
| 2006年 | 4361篇 |
| 2005年 | 4102篇 |
| 2004年 | 3859篇 |
| 2003年 | 3978篇 |
| 2002年 | 3551篇 |
| 2001年 | 4156篇 |
| 2000年 | 4254篇 |
| 1999年 | 3376篇 |
| 1998年 | 1475篇 |
| 1997年 | 1334篇 |
| 1996年 | 1246篇 |
| 1995年 | 1522篇 |
| 1994年 | 1358篇 |
| 1993年 | 1222篇 |
| 1992年 | 2583篇 |
| 1991年 | 2702篇 |
| 1990年 | 2586篇 |
| 1989年 | 2605篇 |
| 1988年 | 2369篇 |
| 1987年 | 2350篇 |
| 1986年 | 2427篇 |
| 1985年 | 2340篇 |
| 1984年 | 1881篇 |
| 1983年 | 1677篇 |
| 1982年 | 1149篇 |
| 1979年 | 1749篇 |
| 1978年 | 1397篇 |
| 1977年 | 1151篇 |
| 1976年 | 1212篇 |
| 1975年 | 1293篇 |
| 1974年 | 1501篇 |
| 1973年 | 1514篇 |
| 1972年 | 1405篇 |
| 1971年 | 1304篇 |
| 1970年 | 1250篇 |
| 1969年 | 1285篇 |
排序方式： 共有10000条查询结果，搜索用时 328 毫秒
991.
992.
993.
994.
Robinson AL 《Science (New York, N.Y.)》1979,206(4419):672-673
995.
Kaneps AG 《Science (New York, N.Y.)》1979,204(4390):297-301
Biostratigraphic analysis of seven piston cores from the southeastern Blake Plateau suggests that the upper Miocene to Recent sedimentary section at this location represents a history of deposition of calcareous ooze alternating with current-induced nondeposition or erosion. This record is primarily a result of long-term fluctuations in the velocity of the western boundary current or Gulf Stream, which sweeps the plateau. High-velocity phases of this current system, as signaled by hiatuses in the section, lie within the time limits 4.8 to 6.1, 3.9 to 4.4, 2.3 to 2.9, and 0 to 1.5 million years before present (B.P.). These time intervals are coeval with dated episodes of climatic decline and glaciation. The most intense acceleration of the Gulf Stream, as indicated by deep erosion of the Blake Plateau, occurred in the latest Miocene to earliest Pliocene (4.8 to 6.1 million years B.P.) in conjunction with a major expansion of the Antarctic ice cap. Subsequent accelerations of the Gulf Stream coincide with early Pliocene cooling in the Southern Hemisphere, worldwide expansion of high-altitude-high-latitude glaciers in the late Pliocene, and the classical glaciations of the Pleistocene. An additional, protracted increase in the average velocity of the Gulf Stream, which began in the late Miocene and culminated in the mid-Pliocene (about 3.8 million years B.P.), can be attributed to the gradual emergence of the Central American isthmus. 相似文献
996.
997.
Owadally AW 《Science (New York, N.Y.)》1979,203(4387):1363-1364
998.
999.
Bromley DA 《Science (New York, N.Y.)》1980,209(4452):110-121
From massive quarks deep in the hearts of atomic nuclei to the catastrophic collapse of giant stars in the farthest reaches of the universe, from the partial realization of Einstein's dream of a unified theory of the forces of nature to the most practical applications in technology, medicine, and throughout contemporary society, physics continues to have a profound impact on man's view of the universe and on the quality of life. The author argues that the past few years, in terms of new discoveries, new insight-and the new questions-have been among the most productive in the history of the field and puts into context his selection of some of the most important new developments in this fundamental science. 相似文献
1000.