全文获取类型
收费全文 | 609479篇 |
免费 | 167871篇 |
国内免费 | 29950篇 |
出版年
2016年 | 7780篇 |
2015年 | 9493篇 |
2014年 | 11189篇 |
2013年 | 14950篇 |
2012年 | 16754篇 |
2011年 | 17733篇 |
2010年 | 14281篇 |
2009年 | 18206篇 |
2008年 | 16889篇 |
2007年 | 17476篇 |
2006年 | 15658篇 |
2005年 | 15211篇 |
2004年 | 15239篇 |
2003年 | 14370篇 |
2002年 | 15020篇 |
2001年 | 28659篇 |
2000年 | 27298篇 |
1999年 | 25677篇 |
1998年 | 14001篇 |
1997年 | 13831篇 |
1996年 | 12822篇 |
1995年 | 12857篇 |
1994年 | 12188篇 |
1993年 | 11913篇 |
1992年 | 22402篇 |
1991年 | 22143篇 |
1990年 | 22277篇 |
1989年 | 21415篇 |
1988年 | 19993篇 |
1987年 | 18649篇 |
1986年 | 17358篇 |
1985年 | 17178篇 |
1984年 | 13929篇 |
1983年 | 11748篇 |
1982年 | 9768篇 |
1981年 | 8948篇 |
1980年 | 8494篇 |
1979年 | 12974篇 |
1978年 | 10745篇 |
1977年 | 9889篇 |
1976年 | 9288篇 |
1975年 | 10052篇 |
1974年 | 11292篇 |
1973年 | 11148篇 |
1972年 | 10800篇 |
1971年 | 9795篇 |
1970年 | 8556篇 |
1969年 | 8465篇 |
1968年 | 7632篇 |
1967年 | 6593篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Protection of Mice against Lethal Coxsackievirus B3 Infection by Using DNA Immunization 总被引:27,自引:0,他引:27 下载免费PDF全文
Andreas Henke Elke Wagner J. Lindsay Whitton Roland Zell Axel Stelzner 《Journal of virology》1998,72(10):8327-8331
Vaccination with DNA and recombinant vaccinia viruses (rec.VV) has been studied with the coxsackievirus B3 (CVB3) model system. Plasmids encoding all structural proteins of CVB3, when injected intramuscularly, induced only low levels of virus-specific antibodies. However, DNA vaccination with the major structural protein VP1 protected 72.2% of mice from lethal challenge, whereas VP1 expressed by rec.VV was much less efficient. 相似文献
992.
993.
Using a combination of a primary growth retardant, mefluidide, a synergistic additive, chlorsulfuron, a detergent to enhance penetration (X-77), and a herbicide, 2,4-D, to provide for control of broadleaf weeds, full-season management of bluegrass (Poa pratensis L.)—tall fescue (Festuca arundinaceae Schreb.) mixtures along roadsides has been achieved. A single spray application is made in the spring, and no additional herbicide applications or mechanical mowing are needed. The treatment is effective with greater than 90% control of fescue seed heads. Those few seed heads that do form remain short. It is economical. The costs of materials and application are equal to or less than the cost of a single mowing cycle. The treatment is environmentally safe when applied in early spring before most agricultural crops have been planted. The effectiveness and low cost of the combination derive from laboratory and greenhouse observations that various materials, herein referred to as additives, often only weakly effective as growth retardants themselves, will interact synergistically with mefluidide to provide overall treatment effectiveness at application rates that are economical. Using this principle, a combination suitable for roadside vegetation management was devised, field-tested for 2 years under actual use conditions, and found to be effective for full-season vegetation management of mixed bluegrass—tall fescue turf to permit considerable cost savings when compared to three-cycle mechanical mowing. 相似文献
994.
995.
996.
997.
998.
In the red howler monkey, Alouatta seniculus stramineus (2n = 47, 48, or 49), variations in diploid chromosome number are due to different numbers of microchromosomes. Males exhibit a Y;autosome translocation involving the short arm of an individual biarmed autosome. Consequently, the sex-chromosome constitution in the male is X1X2Y1Y2, with X1 representing the original X chromosome, X2 the biarmed autosome (No. 7), Y1 the Y;7p translocation product, and Y2 the acrocentric homolog of 7q. In the first meiotic division, a quadrivalent with a chain configuration can be observed in spermatocytes. Females have an X1X1X2X2 sex-chromosome constitution. Chromosome heteromorphisms were observed in pair 13, due to a pericentric inversion, and pair 19, due to the presence of constitutive heterochromatin. Microchromosomes, which varied in number between individuals, were also heterochromatic. NOR-staining was observed at two separate sites on a single chromosome pair (No. 10). A comparison of A.s. stramineus with A.s. macconnelli shows that these two subspecies have identical diploid chromosome numbers (47, 48, or 49), again due to a varying number of microchromosomes, and that they share a similar sex-chromosome constitution. Their karyotypes, however, are not identical, but can be derived from each other by a reciprocal translocation. Further comparisons with other A. seniculus subspecies reported in the literature indicate that this taxon is not karyologically uniform and that substantial chromosome shuffling has occurred between populations that have been considered to be subspecies by taxonomic criteria based on their morphometric attributes. 相似文献
999.
T Tobe S Minoshima S Yamase N H Choi M Tomita N Shimizu 《Cytogenetics and cell genetics》1991,57(4):193-195
SP-40,40 is a serum glycoprotein consisting of two different subunits (alpha and beta) assembled into a dimer by disulfide bonds. Northern blot hybridization, using total RNA from several cell lines, showed that SP-40,40 is expressed in glioblastoma and testicular tumor cells, as well as hepatoma cells. Spot blot hybridization of flow-sorted human chromosomes, using a SP-40,40 cDNA fragment as a probe, localized the gene for SP-40,40 to human chromosome 8. This gene has been given the designation CLI, for complement lysis inhibitor, by the Human Gene Nomenclature Committee. 相似文献
1000.