全文获取类型
收费全文 | 5379篇 |
免费 | 401篇 |
国内免费 | 1篇 |
出版年
2023年 | 43篇 |
2022年 | 60篇 |
2021年 | 162篇 |
2020年 | 110篇 |
2019年 | 129篇 |
2018年 | 165篇 |
2017年 | 151篇 |
2016年 | 247篇 |
2015年 | 310篇 |
2014年 | 334篇 |
2013年 | 377篇 |
2012年 | 516篇 |
2011年 | 425篇 |
2010年 | 244篇 |
2009年 | 234篇 |
2008年 | 307篇 |
2007年 | 249篇 |
2006年 | 258篇 |
2005年 | 246篇 |
2004年 | 240篇 |
2003年 | 211篇 |
2002年 | 184篇 |
2001年 | 41篇 |
2000年 | 39篇 |
1999年 | 48篇 |
1998年 | 57篇 |
1997年 | 41篇 |
1996年 | 31篇 |
1995年 | 31篇 |
1994年 | 31篇 |
1993年 | 29篇 |
1992年 | 23篇 |
1991年 | 25篇 |
1990年 | 17篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1973年 | 4篇 |
1972年 | 4篇 |
1969年 | 4篇 |
1968年 | 6篇 |
1961年 | 4篇 |
排序方式: 共有5781条查询结果,搜索用时 15 毫秒
21.
Effect of Naturally Occurring nif Reiterations on Symbiotic Effectiveness in Rhizobium phaseoli 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
David Romero Paul W. Singleton Lorenzo Segovia Enrique Morett B. Ben Bohlool Rafael Palacios Guillermo Dvila 《Applied microbiology》1988,54(3):848-850
Most naturally occurring strains of Rhizobium phaseoli possess reiteration of the nif genes. Three regions contain nitrogenase structural genes in strain CFN42. Two of these regions (a and b) have copies of nifH, nifD, and nifK, whereas the third region (c) contains only nifH. Strains containing mutations in either nif region a or nif region b had significantly diminished symbiotic effectiveness compared with the wild-type strain on the basis of nodule mass, total nitrogenase activity per plant, nitrogenase specific activity, total nitrogen in the shoot, and percentage of nitrogen. A strain containing mutations in both nif region a and nif region b was totally ineffective. These data indicate that both nif region a and nif region b are needed for full symbiotic effectiveness in R. phaseoli. 相似文献
22.
Narrow- and Broad-Host-Range Symbiotic Plasmids of Rhizobium spp. Strains That Nodulate Phaseolus vulgaris 总被引:11,自引:4,他引:7
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Susana Brom Esperanza Martinez Guillermo Dvila Rafael Palacios 《Applied microbiology》1988,54(5):1280-1283
Agrobacterium transconjugants containing symbiotic plasmids from different Rhizobium spp. strains that nodulate Phaseolus vulgaris were obtained. All transconjugants conserved the parental nodulation host range. Symbiotic (Sym) plasmids of Rhizobium strains isolated originally from P. vulgaris nodules, which had a broad nodulation host range, and single-copy nitrogenase genes conferred a Fix+ phenotype to the Agrobacterium transconjugants. A Fix− phenotype was obtained with Sym plasmids of strains isolated from P. vulgaris nodules that had a narrow host range and reiterated nif genes, as well as with Sym plasmids of strains isolated from other legumes that presented single nif genes and a broad nodulation host range. This indicates that different types of Sym plasmids can confer the ability to establish an effective symbiosis with P. vulgaris. 相似文献
23.
24.
Potato Lectin: A Cell-Wall Glycoprotein 总被引:1,自引:0,他引:1
The activity and the amount of potato lectin were measured inpotato tuber slices (Solanum tuberosum cv. Huinkul) aeratedfor 48 h. Lectin was found in a soluble form, liberated to themedium and associated with insoluble structures. Polyacrylamidegel electrophoresis in denaturating conditions and immunologicaltechniques indicated that the lectins associated to cell wall,soluble or liberated to the medium, were identical. The cell-wallfraction was found to contain 65% of total lectin in the tuber.The possible role of potato lectin in tubers was discussed. (Received June 5, 1985; Accepted September 3, 1985) 相似文献
25.
Prof. Salomon Bartnicki-Garcia Ildiko Bartnicki Rafael Sentandreu 《Current microbiology》1985,12(3):141-145
Whether intact or dissociated with digitonin, chitosomes isolated from the fungusMucor rouxii lack the ability to bind concanavalin A. The absence of external or internal concanavalin A-binding sites distinguishes the chitosome membrane no only from plasma membrane but also from membranes of other organelles (endoplasmic reticulum, mitochondrion, vacuole). This differential binding ability was used to partially separate chitosomal chitin synthetase from major membranes in a crude cell-free extract ofM. rouxii. 相似文献
26.
Josep J. Centelles Rafael Franco Enrique I. Canela Jorge Bozal 《Neurochemical research》1986,11(4):471-479
Suspensions of rat brain microsomes, synaptosomes, and synaptic vesicles were able to convert adenosine to inosine by means of adenosine deaminase. Isosbestic points of this transformation, at 222, 250 and 281 nm, remained unchanged with time-course. This fact suggests that adenosine deaminase (ADA, E.C. 3.5.4.4) is located on the surface of the vesicles whereas purine nucleoside phosphorylase (PNP, E.C. 2.1.2.4) is located inside the vesicles. Kinetic parameters of the particulate 5-nucleotidase (5N, E.C. 3.1.3.5) and adenosine deaminase were analogous to those of the cytosolic enzymes. These results suggest that soluble and particulate enzymes represent different pools of the same molecular species. 相似文献
27.
The activity of guanine deaminase (GAH, E.C. 3.5.4.3) was lower in rat cerebellum soluble and microsomal fractions than in rat brain subfractions. Adenosine deaminase (ADA, E.C. 3.5.4.4) activity was released in higher proportion than guanine deaminase, purine nucleoside phosphorylase (PNP, E.C. 2.1.2.4), 5-nucleotidase (5N, E.C. 3.1.3.5), and lactate (LDH, E.C. 1.1.1.27) and malate (MDH, E.C. 1.1.1.37) dehydrogenase in press-juices of rat brain. Furthermore, nerve ending-derived fractions (synaptosomes and synaptic vesicles) showed an enrichment of adenosine deaminase and also of 5-nucleotidase. The action of deoxycholate over the subfractions did not increase the activity of either enzyme. The contrary occurred with the remaining enzymes studied. Thus, it is possible that one set of enzymes are located on the surface of the particulate vesicles, whereas another set are located inside these vesicles, suggesting a compartmentation of purine catabolic enzymes in different areas of the central nervous system. 相似文献
28.
Nitrogen Source Regulates Glutamate Dehydrogenase NADP Synthesis in Neurospora crassa 总被引:8,自引:4,他引:4
下载免费PDF全文
![点击此处可从《Journal of bacteriology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Georgina Hernndez Ray Snchez-Pescador Rafael Palacios Jaime Mora 《Journal of bacteriology》1983,154(1):524-528
Neurospora crassa glutamate dehydrogenase-NADP (EC 1.3.1.3) has a higher activity when mycelium is grown on ammonium or nitrate as nitrogen source than when grown on glutamate or glutamine. Quantitative immunoelectrophoresis established that, under all conditions, enzyme activity corresponded to enzyme concentration. Isotope incorporation studies demonstrated that the nitrogen source exerts its regulation at the level of de novo enzyme synthesis. 相似文献
29.
Methylation of the Flagellin of Salmonella typhimurium 总被引:2,自引:2,他引:0
The methylation of endogenous proteins by Salmonella typhimurium SL 870 was investigated in cell-free extracts by using S-adenosylmethionine as methyl donor. Several lines of evidence are presented which suggest that one of the methylated products is the protein flagellin. Mutant strains of SL 870 (nml−fla+ and nml+fla−) were also found to synthesize epsilon-N-methyl-lysine. It is proposed that S. typhimurium possesses at least two genes specifying different methylating enzymes. One gene product is a flagellin-specific methylating enzyme, whereas the other gene(s) codes for enzymes that methylate one or more other cell proteins. 相似文献
30.
Dr. Rafael Bonfante 《Mycopathologia》1968,34(3-4):221-224
Summary A technique for observing the reduction of potassium tellurite byCandidas was developed. Various species of these yeasts reduce it at different concentrations, but that which is most useful for differentiation is 0.02 % added to Sabouraud dextrose agar basal medium. Of the yeasts studied,C. albicans, C. parapsilosis andC. tropicalis all reduced potassium tellurite to the concentration mentioned before, while the growth ofC. krusei, C. parakrusei andC. pseudotropicalis was inhibited. Without exception,C. pseudotropicalis reduced this salt at lower concentrations. The two strains ofC. guilliermondii tested gave contradictory results: one of them grew and reduced potassium tellurite, while the growth of the other was inhibited.Professor of Microbiology. 相似文献