全文获取类型
收费全文 | 17002篇 |
免费 | 1801篇 |
国内免费 | 2篇 |
出版年
2021年 | 221篇 |
2020年 | 150篇 |
2019年 | 158篇 |
2018年 | 171篇 |
2017年 | 194篇 |
2016年 | 300篇 |
2015年 | 467篇 |
2014年 | 600篇 |
2013年 | 751篇 |
2012年 | 855篇 |
2011年 | 826篇 |
2010年 | 551篇 |
2009年 | 443篇 |
2008年 | 661篇 |
2007年 | 784篇 |
2006年 | 669篇 |
2005年 | 646篇 |
2004年 | 626篇 |
2003年 | 574篇 |
2002年 | 585篇 |
2001年 | 477篇 |
2000年 | 458篇 |
1999年 | 389篇 |
1998年 | 225篇 |
1997年 | 195篇 |
1996年 | 183篇 |
1995年 | 165篇 |
1994年 | 186篇 |
1993年 | 165篇 |
1992年 | 298篇 |
1991年 | 272篇 |
1990年 | 292篇 |
1989年 | 266篇 |
1988年 | 283篇 |
1987年 | 282篇 |
1986年 | 218篇 |
1985年 | 248篇 |
1984年 | 235篇 |
1983年 | 211篇 |
1982年 | 168篇 |
1981年 | 175篇 |
1980年 | 152篇 |
1979年 | 210篇 |
1978年 | 199篇 |
1977年 | 151篇 |
1976年 | 155篇 |
1975年 | 156篇 |
1974年 | 183篇 |
1973年 | 140篇 |
1972年 | 167篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
31.
32.
33.
It has been previously reported that fasting may result in decreased lung surfactant production. In order to investigate this relationship and the role of nutrition in lung phospholipid synthesis, 21-day-old rats were exposed for 60 h to one of five dietary regimens: standard rat chow (controls), fasting, pure glucose, pure fat, or pure protein. After the period of fasting there was a 33% decrease in lung protein content, but there was no change in DNA content. Exposure to any of the experimental diets resulted in a decrease in tissue total phospholipid and phosphatidylcholine content per lung, but not per unit lung protein. Similarly lung lavage phospholipid and phosphatidylcholine content was decreased by 25% after fasting when expressed per lung or per unit DNA, but not per unit protein. Pulmonary cholinephosphotransferase (EC 2.7.8.2) activity was decreased in the fasted animals and those fed the protein diet, but not in the glucose or fat-fed animals. The activities of acetyl-CoA carboxylase (EC 6.4.1.2) and microsomal fatty acid elongation were decreased in all the experimental groups except for the glucose-fed group. It is concluded that fasting results in a decrease in lung cell size but not in lung cell number. Total phospholipid and phosphatidylcholine content in lung tissue and lung lavage is decreased per cell but not per unit cell mass. 相似文献
34.
C. M. Wilson 《BMJ (Clinical research ed.)》1932,1(3714):485-487
35.
Axial distortion of airways in the lung 总被引:2,自引:0,他引:2
Kallok M. J.; Lai-Fook S. J.; Hajji M. A.; Wilson T. A. 《Journal of applied physiology》1983,54(1):185-190
36.
37.
38.
Human hypoxanthine-guanine phosphoribosyltransferase 总被引:6,自引:0,他引:6
J M Wilson R Kobayashi I H Fox W N Kelley 《The Journal of biological chemistry》1983,258(10):6458-6460
A mutant form of human hypoxanthine-guanine phosphoribosyltransferase (HPRTToronto) was isolated from erythrocytes of a male patient with gout due to a partial deficiency of enzyme activity. The tryptic peptides of HPRTToronto were mapped by reverse-phase high pressure liquid chromatography in an attempt to define the precise abnormality in its primary structure. Sequence analysis of the single aberrant peptide in HPRTToronto revealed an arginine to glycine amino acid substitution at position 50. A single nucleotide change in the codon for arginine 50 (CGA leads to GGA) could explain this substitution. 相似文献
39.
The preparation and kinetics of lactate dehydrogenase attached to water-insoluble particles and sheets 总被引:2,自引:2,他引:0 下载免费PDF全文
1. The preparation of lactate dehydrogenase covalently attached to anion-exchange cellulose particles and sheets by use of a dichloro-sym-triazinyl dyestuff, Procion brilliant orange MGS, is described. 2. The stability and kinetic properties of these preparations were investigated. 3. An equation is derived to describe the change in concentration of a substrate when passed through a uniform bed of a substrate-inhibited enzyme. A number of theoretical curves are shown to illustrate the system. 4. A titrimetric assay for lactate dehydrogenase is described, and shown to be stoicheiometric over the range pH5.0-9.2. 5. The results are discussed in relation to previous work, and the effects of charged groups on the support, and of the diffusion film surrounding any particle in suspension, are treated qualitatively. 相似文献
40.
G. Fox Wilson 《The Annals of applied biology》1943,30(4):364-370
The results of experiments on the infection of many different plants with seven biologic strains of known history of the nematode, Anguillulina dipsaci (Kühn), are given, together with the results obtained by other investigators. The technique by which the nematode was induced to infect other host plants is described in detail. The biologic strain theory in relation to A. dipsaci is discussed, together with the merits of the trinomial system of nomenclature in connexion with unspecialized races. The factors concerned with nematode outbreaks receive consideration. The relationship that exists between flower colour in herbaceous phloxes and the degree of infection by A. dipsaci is presented. 相似文献