全文获取类型
收费全文 | 60368篇 |
免费 | 4939篇 |
国内免费 | 31篇 |
专业分类
65338篇 |
出版年
2022年 | 413篇 |
2021年 | 856篇 |
2020年 | 528篇 |
2019年 | 639篇 |
2018年 | 831篇 |
2017年 | 773篇 |
2016年 | 1358篇 |
2015年 | 2393篇 |
2014年 | 2517篇 |
2013年 | 3338篇 |
2012年 | 4240篇 |
2011年 | 4244篇 |
2010年 | 2758篇 |
2009年 | 2440篇 |
2008年 | 3532篇 |
2007年 | 3590篇 |
2006年 | 3395篇 |
2005年 | 3419篇 |
2004年 | 3357篇 |
2003年 | 3151篇 |
2002年 | 3116篇 |
2001年 | 714篇 |
2000年 | 533篇 |
1999年 | 729篇 |
1998年 | 865篇 |
1997年 | 597篇 |
1996年 | 603篇 |
1995年 | 591篇 |
1994年 | 572篇 |
1993年 | 596篇 |
1992年 | 536篇 |
1991年 | 463篇 |
1990年 | 390篇 |
1989年 | 406篇 |
1988年 | 402篇 |
1987年 | 339篇 |
1986年 | 341篇 |
1985年 | 395篇 |
1984年 | 444篇 |
1983年 | 374篇 |
1982年 | 459篇 |
1981年 | 409篇 |
1980年 | 363篇 |
1979年 | 241篇 |
1978年 | 293篇 |
1977年 | 284篇 |
1976年 | 231篇 |
1975年 | 216篇 |
1974年 | 236篇 |
1973年 | 219篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
This paper is concerned with gene survival in a population which may increase without density dependence according to a generalization of the Moran model for haploid individuals. A selective advantage to one allele and the possibility of differential reproductive rates are allowed. Simple conditions are given for ultimate homozygosity to be certain and for the possibility of ultimate polymorphism. The results complement and extend those of Heyde (1981, 1982). 相似文献
2.
3.
4.
5.
6.
7.
Peter J Stephens 《BMJ (Clinical research ed.)》2005,330(7506):1508-1509
8.
9.
Murine Cytomegalovirus m02 Gene Family Protects against Natural Killer Cell-Mediated Immune Surveillance 下载免费PDF全文
Sofia A. Oliveira Se-Ho Park Peter Lee Albert Bendelac Thomas E. Shenk 《Journal of virology》2002,76(2):885-894
The murine cytomegalovirus m02 gene family encodes putative type I membrane glycoproteins named m02 through m16. A subset of these genes were fused to an epitope tag and cloned into an expression vector. In transfected and murine cytomegalovirus-infected cells, m02, m04, m05, m06, m07, m09, m10, and m12 localized to cytoplasmic structures near the nucleus, whereas m08 and m13 localized to a filamentous structure surrounding the nucleus. Substitution mutants lacking the m02 gene (SMsubm02) or the entire m02 gene family (SMsubm02-16) grew like their wild-type parent in cultured cells. However, whereas SMsubm02 was as pathogenic as the wild-type virus, SMsubm02-16 was markedly less virulent. SMsubm02-16 produced less infectious virus in most organs compared to wild-type virus in BALB/c and C57BL/6J mice, but it replicated to wild-type levels in the organs of immunodeficient gamma(c)/Rag2 mice, lacking multiple cell types including natural killer cells, and in C57BL/6J mice depleted of natural killer cells. These results argue that one or more members of the m02 gene family antagonize natural killer cell-mediated immune surveillance. 相似文献
10.
Victor F. Medina Peter M. Jeffers Steven L. Larson Waleska Perez 《International journal of phytoremediation》2000,2(4):287-295
Bleach treatment of plants was studied as a simple alternative to axenic tissue cultures for demonstrating phytodegradation of aqueous and gas-phase environmental contaminants. Parrotfeather (Myriophyllum aquaticum), spinach (Spinacia oleracea), and wheat (Triticum aestivum) were exposed to 0.525% NaC10 solutions for 15 s, then rinsed in deionized water. Plate counts indicated that 97 to 100% of viable bacteria were removed from parrotfeather and spinach. Transformation rates for 2,4,6-trinitrotoluene (TNT) by bleached and untreated parrotfeather were virtually identical. Similarly, treated and untreated spinach, wheat heads, and wheat leaves removed methyl bromide (MeBr) from air at the same rates. However, wheat root with attendant adhering soil was rendered inactive by bleach treatment. Parrotfeather roots examined by dissecting microscope and by electron microscope showed no significant damage caused by bleach treatment. 相似文献