全文获取类型
收费全文 | 537954篇 |
免费 | 55695篇 |
国内免费 | 433篇 |
出版年
2018年 | 5054篇 |
2017年 | 4876篇 |
2016年 | 6767篇 |
2015年 | 8423篇 |
2014年 | 10076篇 |
2013年 | 14364篇 |
2012年 | 16055篇 |
2011年 | 16707篇 |
2010年 | 11385篇 |
2009年 | 10234篇 |
2008年 | 14730篇 |
2007年 | 15309篇 |
2006年 | 14324篇 |
2005年 | 13774篇 |
2004年 | 13407篇 |
2003年 | 13056篇 |
2002年 | 12911篇 |
2001年 | 27150篇 |
2000年 | 27427篇 |
1999年 | 21139篇 |
1998年 | 6439篇 |
1997年 | 6739篇 |
1996年 | 6516篇 |
1995年 | 6025篇 |
1994年 | 5887篇 |
1993年 | 5671篇 |
1992年 | 17094篇 |
1991年 | 16700篇 |
1990年 | 16334篇 |
1989年 | 15798篇 |
1988年 | 14640篇 |
1987年 | 13698篇 |
1986年 | 12504篇 |
1985年 | 12695篇 |
1984年 | 10122篇 |
1983年 | 8801篇 |
1982年 | 6363篇 |
1981年 | 5732篇 |
1980年 | 5345篇 |
1979年 | 9561篇 |
1978年 | 7275篇 |
1977年 | 6595篇 |
1976年 | 6201篇 |
1975年 | 7161篇 |
1974年 | 7560篇 |
1973年 | 7468篇 |
1972年 | 6751篇 |
1971年 | 6022篇 |
1970年 | 5363篇 |
1969年 | 5019篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
211.
Burt V. Bronk Joe D. Patton David N. Mellard 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1982,697(3):278-285
Chick embryo fibroblasts were treated with the monofunctional alkylating agent methylmethane sulfonate at various concentrations for 1 h at 42°C, rinsed and then incubated post-treatment at various temperatures at which the kinetics of alkali-labile bond disappearance was followed. Growth experiments showed that these cells grew similarly at temperatures of either 37°C or 42°C. Repair as assessed by removal of alkali-labile bond was also similar for postincubation in the temperature range 37–42°C for damage due to methylmethane sulfonate treatment at concentrations less than 1.5 mM. When the postincubation temperature was raised higher than 42.5–43°C, this type of repair was stopped. The normal internal body temperature of adult chickens is about 41.6°C. Hence the present finding indicates that chick cells are much more severely restricted in DNA repair at temperatures above normal than are mammalian cells, which can function in this respect for several deg. C above 37°C. 相似文献
212.
A. GUY PLINT RON K. PICKERILL 《Lethaia: An International Journal of Palaeontology and Stratigraphy》1985,18(4):341-347
Middle Eocene, non-marine sediments from southern England contain examples of Teredolites borings in two contrasting palaeoenvironmental settings, viz.: (A) as in situ borings in an allochthonous lignite in an abandoned river channel and (B) as bored logs in cross-bedded fluvial sandstones of probable point-bar origin. The lignite is 0.30 m thick, of which the upper 0.20 m is intensely bored. Rounded pebbles of ?charcoal at its base also show small borings. A log in a fluvial sandstone shows densely-packed. radial club-shaped borings. now filled with sandstone. The wood substrate has subsequently been oxidized away. To our knowledge, this is the first detailed account of Teredolites from an ancient freshwater setting. 相似文献
213.
In experiments on CBA mice it was shown that migration of 51Cr-labeled spleen lymphocytes, injected intravenously, to lymph nodes of intact recipients was suppressed 6-24 months after the administration of a radiopharmaceutic preparation of selenium-75-selenomethionine in a quantity forming the doses of 1 Gy and 1.5 Gy absorbed within the whole body and lymphoid organs, respectively. Migration of labeled lymphocytes to the liver, kidneys and lungs, as well as their retention in the circulating blood, were increased. As the result of the migration disorders the specific affinity of lymphocytes for peripheral lymphoid tissue decreased. 相似文献
214.
215.
216.
M. Y. Shukor M. F. Rahman Z. Suhaili N. A. Shamaan M. A. Syed 《World journal of microbiology & biotechnology》2009,25(7):1225-1234
A bacterium that was able to tolerate and reduce as high as 50 mM of sodium molybdate to molybdenum blue has been isolated
from a metal recycling ground. The isolate was tentatively identified as Serratia sp. strain Dr.Y8 based on the carbon utilization profiles using Biolog GN plates and partial 16S rDNA molecular phylogeny.
ANOVA analysis showed that isolate Dr.Y8 produced significantly higher (P < 0.05) amount of Mo-blue with 3, 5.1 and 11.3 times more molybdenum blue than previously isolated molybdenum reducers such
as Serratia
marcescens strain Dr.Y6, E. coli K12 and E. cloacae strain 48, respectively. Its molybdate reduction characteristics were studied in this work. Electron donor sources such as
sucrose, mannitol, fructose, glucose and starch supported molybdate reduction. The optimum phosphate, pH and temperature that
supported molybdate reduction were 5 mM, pH 6.0 and 37°C, respectively. The molybdenum blue produced from cellular reduction
exhibited a unique absorption spectrum with a maximum peak at 865 nm and a shoulder at 700 nm. Metal ions such as chromium,
silver, copper and mercury resulted in approximately 61, 57, 80, and 69% inhibition of the molybdenum-reducing activity at
1 mM, respectively. The reduction characteristics of strain Dr.Y8 suggest that it would be useful in future molybdenum bioremediation. 相似文献
217.
T. A. Misharina M. B. Terenina N. I. Krikunova I. A. Khankhalaeva I. S. Khamagaeva L. L. Nikiforova 《Applied Biochemistry and Microbiology》2008,44(5):545-550
The differences between the composition of volatile substances in two specimens of dry smoked sausages produced using a standard and experimental (a mixture of propionic acid bacteria and bifidobacteria) cultures were studied by capillary gas chromatography. It was found that the experimental starter culture intensified the flavor-formation processes as compared with the standard culture. The experimental specimen had richer qualitative and quantitative compositions and displayed more intensive aroma and flavor. The contents of lactones and volatile terpenoids in the experimental specimen were much higher than in the control. The organoleptic characteristics of experimental dry smoked sausage specimen were considerably better. 相似文献
218.
219.
220.
A. D. Neklyudov A. N. Ivankin A. V. Berdutina 《Applied Biochemistry and Microbiology》2000,36(5):452-459
Properties of protein hydrolysates and possible uses of these substances in research and various branches of industry are
considered. The main problem discussed in this paper is the relationship between the degree of protein conversion and characteristics
(structural-functional and physicochemical) of hydrolysates. 相似文献