全文获取类型
收费全文 | 2427篇 |
免费 | 302篇 |
国内免费 | 2篇 |
专业分类
2731篇 |
出版年
2021年 | 22篇 |
2019年 | 24篇 |
2018年 | 23篇 |
2017年 | 29篇 |
2016年 | 36篇 |
2015年 | 64篇 |
2014年 | 79篇 |
2013年 | 112篇 |
2012年 | 140篇 |
2011年 | 98篇 |
2010年 | 63篇 |
2009年 | 61篇 |
2008年 | 105篇 |
2007年 | 112篇 |
2006年 | 92篇 |
2005年 | 95篇 |
2004年 | 88篇 |
2003年 | 88篇 |
2002年 | 79篇 |
2001年 | 80篇 |
2000年 | 86篇 |
1999年 | 87篇 |
1998年 | 39篇 |
1997年 | 27篇 |
1996年 | 24篇 |
1995年 | 37篇 |
1994年 | 21篇 |
1993年 | 29篇 |
1992年 | 60篇 |
1991年 | 55篇 |
1990年 | 44篇 |
1989年 | 42篇 |
1988年 | 36篇 |
1987年 | 45篇 |
1986年 | 35篇 |
1985年 | 32篇 |
1984年 | 26篇 |
1983年 | 22篇 |
1982年 | 23篇 |
1981年 | 20篇 |
1979年 | 33篇 |
1978年 | 36篇 |
1977年 | 18篇 |
1976年 | 20篇 |
1975年 | 32篇 |
1974年 | 17篇 |
1973年 | 34篇 |
1972年 | 16篇 |
1971年 | 26篇 |
1967年 | 22篇 |
排序方式: 共有2731条查询结果,搜索用时 0 毫秒
31.
32.
Sterols of Chlorella. II. The Occurrence of an Unusual Sterol Mixture in Chlorella vulgaris 总被引:2,自引:2,他引:0 下载免费PDF全文
Patterson GW 《Plant physiology》1967,42(10):1457-1459
33.
34.
Glenn W. Patterson 《Journal of phycology》1967,3(1):22-23
Cultures of Chlorella vulgaris were grown aulo-trophically under fluorescent light and heterotrophically on glucose and inorganic salts. Hydrocarbons were extracted and analyzed by gas-liquid chromatography, molecular sieve separations, and silicic acid-AgNO3 chromatography. Chlorella vulgaris grown under both culture conditions contained a series of saturated n-paraffins ranging from 17 to 36 carbon atoms in length. This is in contrast to reports in the early literature which indicated that the hydrocarbon fraction of algae was composed of only 1 or 2 specific hydrocarbons. Only under heterotrophic conditions, however, did C. vulgaris produce 1-penta-cosene and 1-heptacosene as the primary components of the hydrocarbon mixture. Other Chlorella species were examined, but only C. vulgaris produced significant quantities of these compounds. 相似文献
35.
36.
Genetic and physical mapping of a novel region close to the fragile X site on the human X chromosome 总被引:11,自引:0,他引:11
M. N. Patterson M. V. Bell J. Bloomfield T. Flint H. Dorkins S. N. Thibodeau D. Schaid G. Bren C. E. Schwartz b. Wieringa H. -H. Ropers D. F. Callen G. Sutherland U. Froster-Iskenius H. Vissing K. E. Davies 《Genomics》1989,4(4):570-578
We report the isolation and characterization of a novel DNA marker (1A1) in Xqter in the region of the fragile X. Genetic studies in families segregating for the fragile X syndrome suggest that 1A1 lies between the disease mutation and the distal locus, DXS52. Studies in normal and fragile X families show that 1A1 is tightly linked to DXS52 (Zmax = 17.20; theta max = 0.03) and F8 (Zmax = 7.01; theta max = 0.08). Multipoint mapping of families supports the order Xcen-DXS105-FRAXA-1A1-DXS52-(F8, DXS115)-Xqter. Pulsed-field gel electrophoresis (PFGE) studies demonstrate that 1A1 defines a new region of at least 2 Mb of DNA not physically linked to DXS52 or F8, thus extending the physical map of Xq27-qter to over 4 Mb. Complex partial digestion PFGE patterns, probably due to differing degrees of methylation, are observed with 1A1 in unrelated normal and fragile-X-positive individuals, whereas other distal markers give uniform digestion profiles. Physical data suggest that 1A1 lies in a region less CpG rich than other distal markers in Xq27-qter. 相似文献
37.
38.
Analysis of human chromosome 21: correlation of physical and cytogenetic maps; gene and CpG island distributions. 总被引:40,自引:3,他引:37 下载免费PDF全文
K Gardiner M Horisberger J Kraus U Tantravahi J Korenberg V Rao S Reddy D Patterson 《The EMBO journal》1990,9(1):25-34
Human chromosome 21 has been analyzed by pulsed-field gel electrophoresis using somatic cell hybrids containing limited regions of the chromosome and greater than 60 unique sequence probes. Thirty-three independent NotI fragments have been identified, totalling 43 million bp. This must account for essentially the entire long arm, and therefore gaps remaining in the map must be small. The extent of the pulsed-field map has allowed the direct correlation of the physical map with the cytogenetic map: translocation breakpoints can be unambiguously positioned along the long arm and the distances between them measured in base pairs. Three breakpoints have been identified, providing physical confirmation of cytogenetic landmarks. Information on sequence organization has been obtained: (i) 60% of the unique sequence probes are located within 11 physical linkage groups which can be contained in only 20% of the long arm; (ii) 9/21 genes are clustered within 4%; (iii) translocation breakpoints appear to occur within CpG island regions, making their identification difficult by pulsed-field techniques. This analysis contributes to the human genome mapping effort, and provides information to guide the rapid investigation of the biology of chromosome 21. 相似文献
39.
40.
The virion of Leishmania RNA virus is predicted to be composed of a 742-amino-acid major capsid protein and a small percentage of capsid-polymerase fusion molecules. Recently, the capsid protein alone was expressed and shown to spontaneously assemble into viruslike particles. Since the major structural protein of the virion shell self-assembles into viruslike particles when expressed in the baculovirus expression system, assembly of the virion can be studied by mutational analysis and expression of a single open reading frame. In this study, several deletions and one addition of the capsid protein of Leishmania RNA virus LRV1-4 were generated. These mutants show different degrees of assembly. Assembly domains are being identified such that the capsid protein may be used as a macromolecular packaging and delivery system for Leishmania species. 相似文献