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51.
Dr. Lois Aldwin Robert Toso Robert Goodson Jennie Hunter 《Journal of industrial microbiology & biotechnology》1990,5(4):239-246
Summary The production of streptavidin byStreptomyces avidinii in several different media was examined at 24, 48 and 72 hours. Flask studies indicated that fermentation media containing either complex or multiple carbon sources resulted in higher yields of streptavidin than media with a single carbon source. Streptavidin could be detected in crude fermentation broths by use of a tritiated biotin binding assay. This assay appears to give useful estimates of streptavidin production. Depending upon the medium employed, streptavidin yields ranged from 0.5 mg/l to 53 mg/l. Production was successfully scaled up to ten liter fermentors. Streptavidin was purified in a one step process from centrifuged, concentrated fermentation broths by binding the protein to an iminobiotin column at pH 11 followed by elution at pH 4.0. Recovery percentages varied depending upon the solubility of the fermentation media ingredients. 相似文献
52.
Statistics for near independence in multivariate extreme values 总被引:17,自引:0,他引:17
53.
An exhaustive analysis of registers of births, deaths, and marriages is used to reconstitute genealogies, both ascending and
descending, for all individuals who lived in two mountain valleys: the Valserine valley (in the French Jura), which is studied
from the end of the seventeenth century to the present, and the Vallouise valley (in the French Alps) studied from the seventeenth
to the nieteenth centuries.
This genealogical approach makes it possible to trace the reproductive process in the populations whose members lived in the
valley for several generations. The Vallouise valley forms an important demographic isolate; nearly 98 per cent of those born
between 1820 and 1849 were descendants of ancestors who had lived in the valley two centuries earlier. By contrast, there
has been continuous immigration into the Valserine valley, which has resulted in a constant renewal of the gene pool. Only
18 per cent of the gene pool of individuals living in this valley two centuries later was contributed by those who lived in
the valley and who were born before 1750. 相似文献
54.
55.
Engineering challenges in high density cell culture systems 总被引:2,自引:0,他引:2
Ozturk SS 《Cytotechnology》1996,22(1-3):3-16
High density cell culture systems offer the advantage of production of bio-pharmaceuticals in compact bioreactors with high volumetric production rates; however, these systems are difficult to design and operate. First of all, the cells have to be retained in the bioreactor by physical means during perfusion. The design of the cell retention is the key to performance of high density cell culture systems. Oxygenation and media design are also important for maximizing the cell number. In high density perfusion reactors, variable cell density, and hence the metabolic demand, require constant adjustment of perfusion rates. The use of cell specific perfusion rate (CSPR) control provides a constant environment to the cells resulting in consistent production. On-line measurement of cell density and metabolic activities can be used for the estimation of cell densities and the control of CSPR. Issues related to mass transfer and mixing become more important at high cell densities. Due to the difference in mass transfer coefficients for oxygen and CO2, a significant accumulation of dissolved CO2 is experienced with silicone tubing aeration. Also, mixing is observed to decrease at high densities. Base addition, if not properly done, could result in localized cell lysis and poor culture performance. Non-uniform mixing in reactors promotes the heterogeneity of the culture. Cell aggregation results in segregation of the cells within different mixing zones. This paper discusses these issues and makes recommendations for further development of high density cell culture bioreactors. 相似文献
56.
57.
牛病毒性腹泻病毒的成熟和释放 总被引:5,自引:0,他引:5
试验中用电镜观察了牛病毒性腹泻病毒OregonC24V株在感染新生牛睾丸细胞中的形态发生。成熟的病毒颗粒是直径约为50nm的球形颗粒,内含直径约为30nm的核心。病毒在宿主细胞的胞质内复制,通过糙面内质网膜出芽成熟。病毒可以通过外排或在细胞死亡后含有病毒颗粒的空泡崩溃而释放到胞外。 相似文献
58.
Guo-Ling Nan Adelheid R. Kuehnle 《In vitro cellular & developmental biology. Plant》1995,31(3):131-136
Summary Five parameters were examined for their effect on transformation ofDendrobium tissues by microprojectile bombardment. The superpromoter in pBI426 produced at least 1.5 times as many transient transformants
as the single cauliflower mosaic virus 35S promoter in pBI121 (37 to 69% vs. 0 to 44%) with dark and frequent GUS (β-glucuronidase) staining. Tissue, genotype, and type of microparticle significantly affected transient GUS activity. Higher
expression was seen in protocormlike bodies and in hybrid UH44 compared to etiolated shoots and protocorms and to hybrids
M61 and K1329-39. Microparticles of 1.6-μm Bio-Rad gold were more effective than 1.0-μm ASI gold. Transient GUS activity did
not differ among protocormlike bodies bombarded using helium propellant pressures of 650, 900, or 1100 psi. Transgenic plants
were recovered fromDendrobium UH800 protocormlike bodies bombarded with pBI426-coated, 1.1-μm tungsten particles using an early-model gunpowder-driven
apparatus with an estimated stable transformation rate of 11.7%. One transgenic plant ofDendrobium UH44 was recovered from etiolated shoot explants bombarded with pBI121-coated, 1.1-μm tungsten particles using the Dupont
PDS-1000 with a stable transformation rate of 0.17%. Positive selection results showed 100 to 200 mg·liter−1 kanamycin to be appropriate for regeneration of transgenic plants from protocormlike bodies, protocorms, and etiolated shoot
explants over a 3- to 9.5-mo. period. 相似文献
59.
On semiparametric inference for modulated renewal processes 总被引:1,自引:0,他引:1
60.