全文获取类型
收费全文 | 16235篇 |
免费 | 41篇 |
国内免费 | 41篇 |
专业分类
系统科学 | 70篇 |
丛书文集 | 108篇 |
教育与普及 | 28篇 |
理论与方法论 | 57篇 |
现状及发展 | 5810篇 |
研究方法 | 758篇 |
综合类 | 9166篇 |
自然研究 | 320篇 |
出版年
2013年 | 186篇 |
2012年 | 232篇 |
2011年 | 567篇 |
2010年 | 102篇 |
2008年 | 263篇 |
2007年 | 333篇 |
2006年 | 334篇 |
2005年 | 311篇 |
2004年 | 299篇 |
2003年 | 282篇 |
2002年 | 287篇 |
2001年 | 691篇 |
2000年 | 678篇 |
1999年 | 370篇 |
1993年 | 47篇 |
1992年 | 341篇 |
1991年 | 273篇 |
1990年 | 297篇 |
1989年 | 316篇 |
1988年 | 285篇 |
1987年 | 268篇 |
1986年 | 291篇 |
1985年 | 314篇 |
1984年 | 270篇 |
1983年 | 245篇 |
1982年 | 203篇 |
1981年 | 189篇 |
1980年 | 211篇 |
1979年 | 502篇 |
1978年 | 391篇 |
1977年 | 365篇 |
1976年 | 302篇 |
1975年 | 348篇 |
1974年 | 497篇 |
1973年 | 378篇 |
1972年 | 386篇 |
1971年 | 491篇 |
1970年 | 609篇 |
1969年 | 413篇 |
1968年 | 448篇 |
1967年 | 377篇 |
1966年 | 384篇 |
1965年 | 259篇 |
1959年 | 135篇 |
1958年 | 225篇 |
1957年 | 162篇 |
1956年 | 115篇 |
1955年 | 115篇 |
1954年 | 110篇 |
1948年 | 89篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
961.
962.
963.
964.
965.
Most of the world's cod (Gadus morhua) fisheries are now tightly regulated or closed altogether. Being able to link individual fish to their population of origin would assist enormously in policing regulations and in identifying poachers. Here we show that microsatellite genetic markers can be used to assign individual cod from three different populations in the northeastern Atlantic Ocean to their population of origin. 相似文献
966.
Probabilities will help us plan for climate change 总被引:1,自引:0,他引:1
967.
In cycling and orienteering competitions, competitors can become bunched into packs, which may mask an individual's true ability. Here we model this process with a view to determining when competitors' times are determined more by others than by their own ability. Our results may prove useful in helping to stage events so that pack formation can be avoided. 相似文献
968.
969.
Marsh D 《Cellular and molecular life sciences : CMLS》2003,60(8):1575-1580
Magnetic resonance results, principally from 2H-nuclear magnetic resonance, indicate that the mean lipid-chain ordering at the surface of transmembrane proteins is comparable to that in fluid lipid bilayers. Principally, it is the requirement for matching the hydrophobic lengths of lipid and protein that modulates the degree of chain ordering at the lipid-protein interface. The distribution of chain order parameters is, nonetheless, broader in the presence of integral proteins than in fluid lipid bilayers. The chain configurations of the phospholipids that are resolved in crystals of integral membrane proteins display considerable conformational heterogeneity. Chain C–C dihedral angles are, however, not restricted to the energetically allowable trans and gauche rotamers. This indicates that the chains of a given lipid do not have a unique configuration in protein crystals. 相似文献
970.
Recently discovered functions of glucosylceramides in plants and fungi 总被引:11,自引:0,他引:11
Glycosphingolipids are ubiquitous membrane lipids of eukaryotic organisms and a few bacteria. Whereas inositol-containing glycosphingolipids are restricted to plants and fungi, galactosylceramide occurs only in fungi and animals. In contrast, glucosylceramide is the unique glycosphingolipid which plants, fungi and animals have in common. However, there are specific differences in the structure of the ceramide backbone of glucosylceramides from these organisms. A comparison of the structural features and the biosynthesis of glucosylceramides from plants, fungi and animals will contribute to our understanding of their functions, which so far have been analysed mainly in animals. The availability of nearly all genes involved in the biosynthesis of glucosylceramides enables the specific manipulation of glycosphingolipid metabolism by techniques of forward and reverse genetics. Application of this approach to unicellular organisms like yeasts, multicellular filamentous fungi, as well as to complex organisms like plants will reveal common and different glucosylceramide functions in these organisms. These glycolipids play a role both in intracellular processes and in cell-to-cell interactions. These interactions may occur between cells of a multicellular organism or between cells of different species, as in host-pathogen interactions. 相似文献