全文获取类型
收费全文 | 9816篇 |
免费 | 974篇 |
国内免费 | 4篇 |
专业分类
10794篇 |
出版年
2023年 | 66篇 |
2022年 | 129篇 |
2021年 | 261篇 |
2020年 | 143篇 |
2019年 | 145篇 |
2018年 | 208篇 |
2017年 | 190篇 |
2016年 | 304篇 |
2015年 | 507篇 |
2014年 | 552篇 |
2013年 | 621篇 |
2012年 | 795篇 |
2011年 | 717篇 |
2010年 | 480篇 |
2009年 | 423篇 |
2008年 | 576篇 |
2007年 | 509篇 |
2006年 | 477篇 |
2005年 | 442篇 |
2004年 | 441篇 |
2003年 | 431篇 |
2002年 | 375篇 |
2001年 | 121篇 |
2000年 | 105篇 |
1999年 | 121篇 |
1998年 | 113篇 |
1997年 | 90篇 |
1996年 | 70篇 |
1995年 | 61篇 |
1994年 | 65篇 |
1993年 | 64篇 |
1992年 | 83篇 |
1991年 | 66篇 |
1990年 | 66篇 |
1989年 | 60篇 |
1988年 | 53篇 |
1987年 | 54篇 |
1986年 | 51篇 |
1985年 | 48篇 |
1984年 | 50篇 |
1983年 | 41篇 |
1982年 | 39篇 |
1981年 | 50篇 |
1980年 | 36篇 |
1979年 | 49篇 |
1978年 | 41篇 |
1977年 | 47篇 |
1976年 | 32篇 |
1974年 | 31篇 |
1968年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Marilyn Frank Fuller W. Bazer W.W. Thatcher C.J. Wilcox 《Prostaglandins & other lipid mediators》1977,14(6):1183-1196
Polyvinyl catheters were placed into the right and left utero-ovarian veins and saphenous vein and artery of three control (C) and four estradiol valerate (EV) treated gilts on Day 9 after onset of estrus. The EV treated gilts received 5mg EV/day on Days 11 through 15 after onset of estrus. On Days 12 through 17 utero-ovarian vein blood samples were collected at 15 min intervals from 0700 to 1000 hr and 1900 to 2200 hr and single samples were taken at 1100 and 2300 hr. Peripheral blood samples (saphenous vein or artery) were taken at 0700, 1100, 1900 and 2300 hr from Day 12 until the control gilts returned to estrus or until Day 25 for EV treated gilts and used to measure plasma steroid hormone concentrations. Utero-ovarian vein prostaglandin F (PGF) concentrations (ng/ml, n=1,177) were measured by RIA. Status (control
EV treated gilts) by day interactions were detected (P=.10). Curvilinear day trends were detected for plasma PGF concentrations in control (P<.01) but not EV treated gilts. PGF concentrations (
) for control and EV treated gilts were 1.20 ± 2.08 and .26 ± .84 ng/ml, respectively. PGF peaks (concentrations greater than
+ 2 S.D.) occured with greater frequency in control gilts (X2 = 4.87; P<.05). The interestrus interval (
) for control and treated gilts was 19.0 ± .6 and 146.5 ± 74.8 days, respectively. Data indicate that estradiol valerate may exert its luteotrophic effect by preventing PGF release from the uterus. 相似文献
42.
Pea chloroplastic phosphoribulokinase and yeast phosphoriboisomerase partition independently of one another in a two-phase polyethyleneglycol, dextran system, but apparent interaction is seen when ribose-5-phosphate is added to the two-phase system. It appears that the pea leaf of kinase recognizes yeast isomerase when it is carrying metabolite. 相似文献
43.
Two Types of Genetic Interaction Implicate the Whirligig Gene of Drosophila Melanogaster in Microtubule Organization in the Flagellar Axoneme 总被引:1,自引:1,他引:0 下载免费PDF全文
The mutant nc4 allele of whirligig (3-54.4) of Drosophila melanogaster fails to complement mutations in an alpha-tubulin locus, alpha 1t, mutations in a beta-tubulin locus, B2t, or a mutation in the haywire locus. However, wrl fails to map to any of the known alpha- or beta-tubulin genes. The extragenic failure to complement could indicate that the wrl product participates in structural interactions with microtubule proteins. The whirligig locus appears to be haploinsufficient for male fertility. Both a deficiency of wrl and possible loss of function alleles obtained by reverting the failure to complement between wrlnc4 and B2tn are dominant male sterile in a genetic background wild type for tubulin. The dominant male sterility of the revertant alleles is suppressed if the flies are also heterozygous for B2tn, for a deficiency of alpha 1t, or for the haync2 allele. These results suggest that it is not the absolute level of wrl gene product but its level relative to tubulin or microtubule function that is important for normal spermatogenesis. The phenotype of homozygous wrl mutants suggests that the whirligig product plays a role in postmeiotic spermatid differentiation, possibly in organizing the microtubules of the sperm flagellar axoneme. Flies homozygous for either wrlnc4 or revertant alleles are viable and female fertile but male sterile. Premeiotic and meiotic stages of spermatogenesis appear normal. However, in post-meiotic stages, flagellar axonemes show loss of the accessory microtubule on the B-subfiber of outer doublet microtubules, outer triplet instead of outer doublet microtubules, and missing central pair microtubules. 相似文献
44.
45.
46.
Analysis of the nucleoside triphosphate pyrophosphohydrolase specific activity of red cells obtained from a random Caucasian population indicated at least two subclasses. The specific activity of 18% of the population ranged from undetectable activity to 27.5 nmol ITP cleaved/20 min/mg hemoglobin. The remainder of the population had higher activity, 27.5–125 nmoles ITP cleaved/20 min/mg hemoglobin. The variation of NTPH activity evident in the red cells of an individual is reflected in granulocytes, lymphocytes, and platelets of that individual. Erythrocyte activity ranges from 0.7 to 21 units (nmol of ITP cleaved in 20 min)/107 cells, granulocytes have 17–201 units/107 cells, lymphocytes have 91–462 units/107 cells, and platelets have 1.1–7.1 units/107 platelets. These cell differences are discussed with respect to the hypothesis that NTPH prevents incorporation of ITP or dITP into nucleic acids.This work was supported by funds allocated by the Agricultural Experiment Station, Michigan State University. Michigan Agricultural Experiment Station Journal No. 8727. 相似文献
47.
48.
49.
50.
Amy Wong Devi R. Sagar Catharine A. Ortori David A. Kendall Victoria Chapman David A. Barrett 《Journal of lipid research》2014,55(9):1902-1913
We describe a novel LC method for the simultaneous and quantitative profiling of 43 oxylipins including eicosanoids, endocannabinoids, and structurally related bioactive lipids with modified acyl groups. The LC-MS/MS method uses switching at a defined time between negative and positive electrospray ionization modes to achieve optimal detection sensitivity for all the lipids. The validated method is linear over a range of 0.01–5 nmol/g (0.1–50 nmol/g for 2-arachidonoyl glycerol) with intra- and interday precision and accuracy between 1.38 and 26.76% and 85.22 and 114.3%, respectively. The method successfully quantified bioactive lipids in different tissue types in the rat, including spinal cord, dorsal root ganglia (DRGs), knee joint, brain, and plasma. Distinct regional differences in the pattern of lipid measured between tissue types were observed using principle component analysis. The method was applied to analyze tissue samples from an established preclinical rat model of osteoarthritis (OA) pain and showed that levels of 12-hydroxyeicosatetraenoic acid were significantly increased in the OA rat knee joint compared with controls, and that 15-hydroxyeicosatetraenoic acid was significantly increased in the DRGs in the model of OA compared with controls. The developed LC-MS/MS method has the potential to provide detailed pathway profiling in tissues and biofluids where the disruption of bioactive oxylipins may be involved in disease states. 相似文献