全文获取类型
收费全文 | 971篇 |
免费 | 97篇 |
国内免费 | 2篇 |
专业分类
1070篇 |
出版年
2022年 | 9篇 |
2021年 | 17篇 |
2020年 | 16篇 |
2019年 | 18篇 |
2018年 | 34篇 |
2017年 | 20篇 |
2016年 | 23篇 |
2015年 | 38篇 |
2014年 | 39篇 |
2013年 | 48篇 |
2012年 | 58篇 |
2011年 | 67篇 |
2010年 | 38篇 |
2009年 | 37篇 |
2008年 | 59篇 |
2007年 | 48篇 |
2006年 | 42篇 |
2005年 | 36篇 |
2004年 | 37篇 |
2003年 | 36篇 |
2002年 | 37篇 |
2001年 | 21篇 |
2000年 | 19篇 |
1999年 | 38篇 |
1998年 | 14篇 |
1997年 | 6篇 |
1996年 | 14篇 |
1995年 | 8篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 12篇 |
1989年 | 6篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 12篇 |
1985年 | 11篇 |
1984年 | 6篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1975年 | 4篇 |
1974年 | 7篇 |
1971年 | 4篇 |
排序方式: 共有1070条查询结果,搜索用时 15 毫秒
1.
2.
Micrococcus lysodeikticus cytoplasmic membranes labeled with ]-14C]arginine plus [-14C]-threonine were prepared and subjected to mild washing treatments to fractionate membrane proteins. Polyacrylamide gel electrophoresis of total membranes, in the presence of sodium dodecyl sulfate, results in the separation of 28-30 bands of labeled protein. Three peaks of protein show higher specific radioactivity than the others. Chloramphenicol at 100 mug/ml inhibits the incorporation of labeled precursors into membrane proteins by 45-70 percent, some of them being more affected by the antibiotic. From all available results, we suggest that the partial inhibitory effect shown by this antibiotic could be due to the existence of specific biosynthetic sites for some membrane proteins, which are differently affected by chloramphenicol. 相似文献
3.
R Martorell F S Mendoza R O Castillo I G Pawson C C Budge 《American journal of physical anthropology》1987,73(4):475-487
Mexican-American children are shorter but relatively heavier than non-Hispanic whites and blacks. The objectives of this paper are to assess the extent to which this "short and plump" physique occurs in data collected in two national surveys (HANES I and II); to determine variations by age, sex, and socioeconomic status; and to investigate the anthropometric characteristics that may account for the overweight. Three groups, defined on the basis of reported ancestry and observed race, are studied: Mexican-Americans (MEXAME), non-Hispanic Whites, (EURAME), and blacks (BLACK). Short stature was clearly associated with the poverty index (PI) in all three groups. MEXAMEs with a PI greater than 1.6 were similar in stature to EURAMEs at the same income level at ages 1-11 years but not at 12-17 years. On the other hand, MEXAMEs were shorter than BLACKs at all ages and income levels. The body mass index (kg/cm2) and poverty were unrelated. With respect to the anthropometric characteristics examined that are related to the body mass index, MEXAMEs and EURAMEs were similar in sitting height as a proportion of total height, arm muscle and fat areas, and triceps skinfold but different in the following ways: MEXAMEs had narrower elbow but broader bitrochanteric breadths and larger chest circumferences and subscapular skinfolds. Greater upper body dimensions and fatfolds seem to best describe the physique of MEXAMEs. However, in multiple regressions, these anthropometric characteristics failed to account fully for the greater relative weight of MEXAMEs as compared to EURAMEs. 相似文献
4.
Stanley A. Mendoza Abelardo Lopez-Rivas James W. Sinnett-Smith Enrique Rozengurt 《Experimental cell research》1986,164(2)
Vasopressin increased intracellular free calcium concentration [Ca2+]i in quin-2-loaded quiescent Swiss 3T3 cells. This effect of vasopressin was rapidly inhibited by biologically active tumour promoters including phorbol dibutyrate (PBt2) and by the synthetic diacylglycerol 1-oleoyl-2-acetyl-glycerol (OAG). Prolonged pretreatment of Swiss 3T3 cells with PBt2 causes a loss of protein kinase C activity (Rodriguez-Pena & Rozengurt, Biochem biophys res commun 120 (1984) 1053) [28]. This pretreatment abolished the inhibition by PBt2 or OAG of vasopressin-mediated increases in Ca2+]i. Vasopressin also stimulated 45Ca2+ efflux from cells pre-loaded with the isotope. This effect of the hormone was also inhibited by PBt2. Prolonged pretreatment with PBt2 prevented the inhibition of vasopressin-stimulated 45Ca2+ release by PBt2. Thus, protein kinase C stimulation inhibits vasopressin-mediated increases in [Ca2+]i and 45Ca2+ efflux apparently by blocking the increased release of Ca2+ from an intracellular store caused by the hormone. These findings suggest that activation of protein kinase C may act as a feedback inhibitor to modulate ligand-mediated increases in [Ca2+]i. 相似文献
5.
6.
Structural and immunological studies on the protoplast membrane of the yeast Candida utilis 总被引:2,自引:1,他引:1 下载免费PDF全文
C Garcia Mendoza M D Garcia Lopez F Uruburu J R Villanueva 《Journal of bacteriology》1968,95(6):2393-2398
Cell membranes of the yeast Candida utilis isolated by lysis of protoplasts have been shown to be lipoprotein in nature. Electron microscopy shows that Mg++ is responsible for maintaining the integrity of the membrane. A close serological relationship was found between membranes and cell walls isolated from the yeast. This relationship was exhibited not only by membranes obtained by strepzyme treatment but also by those obtained from the action of helicase enzyme. No such relationship existed between membranes and whole cells. Related data have been obtained by treatment of yeasts with different digestive enzymes. All of the results suggest that the protoplast membrane possesses traces of structural cell wall material. This material is detectable by serological tests, but not by electron microscopy. 相似文献
7.
8.
9.
DNA supercoiling and thermal regulation of unsaturated fatty acid synthesis in Bacillus subtilis 总被引:4,自引:1,他引:3
Roberto Grau Daniela Gardiol Gerardo Claudio Glikin Diego de Mendoza 《Molecular microbiology》1994,11(5):933-941
Bacillus subtilis growing at 37° C synthesizes, almost exclusively, saturated fatty acids. However, when a culture growing at 37°C is transferred to 20°C, the synthesis of unsaturated fatty acids is induced. The addition of the DNA gyrase inhibitor novobiocin specifically prevented the induction of unsaturated fatty acid synthesis at 20° C. Furthermore, it was determined that plasmid DNA isolated from cells growing at 20°C was significantly more negatively supercoiled than the equivalent DNA isolated from cells growing at 37°C. The overall results agree with the hypothesis that an increase in DNA supercoiling associated with a temperature downshift could regulate the unsaturated fatty acids synthesis in B. subtilis. 相似文献
10.
Post-thawing survival of ram sperm was examined after semen which had been layered on top of isolation columns containing solutions of bovine serum albumin (BSA) in Tris diluent was processed for freezing by the pellet method. Sperm isolated from the bottom of the BSA column had better post-thawing survival than sperm from the top of the column. The efficiency of sperm isolation was affected by the concentration of BSA in the column, the holding time of semen on the column and the concentration of sperm in the layered semen. The best post-thawing survival of sperm occurred when semen diluted to a concentration of 200 x 10(6) sperm/ml was layered on a column of 6% BSA in Tris diluent and the bottom layer of the column was isolated for freezing after two hours' holding time. 相似文献