全文获取类型
收费全文 | 2285篇 |
免费 | 268篇 |
出版年
2021年 | 16篇 |
2019年 | 18篇 |
2018年 | 24篇 |
2016年 | 37篇 |
2015年 | 70篇 |
2014年 | 64篇 |
2013年 | 88篇 |
2012年 | 104篇 |
2011年 | 99篇 |
2010年 | 50篇 |
2009年 | 53篇 |
2008年 | 99篇 |
2007年 | 99篇 |
2006年 | 89篇 |
2005年 | 86篇 |
2004年 | 98篇 |
2003年 | 69篇 |
2002年 | 76篇 |
2001年 | 88篇 |
2000年 | 65篇 |
1999年 | 58篇 |
1998年 | 36篇 |
1997年 | 36篇 |
1996年 | 26篇 |
1995年 | 26篇 |
1994年 | 22篇 |
1993年 | 22篇 |
1992年 | 39篇 |
1991年 | 33篇 |
1990年 | 54篇 |
1989年 | 49篇 |
1988年 | 42篇 |
1987年 | 32篇 |
1986年 | 41篇 |
1985年 | 36篇 |
1984年 | 29篇 |
1983年 | 29篇 |
1982年 | 19篇 |
1981年 | 20篇 |
1979年 | 29篇 |
1978年 | 30篇 |
1977年 | 21篇 |
1976年 | 32篇 |
1975年 | 23篇 |
1974年 | 23篇 |
1973年 | 26篇 |
1972年 | 24篇 |
1971年 | 17篇 |
1970年 | 21篇 |
1969年 | 15篇 |
排序方式: 共有2553条查询结果,搜索用时 15 毫秒
21.
A simple enzyme-linked immunosorbent assay (ELISA) for sex hormone-binding globulin (SHBG) has been developed. Polyclonal antibody raised to SHBG purified to homogeneity was employed. The ELISA, which may be performed in under 4 h, shows no cross-reactivity with other serum proteins, has a sensitivity of less than 1.2 fmol per sample, demonstrates excellent correlation with ligand-binding techniques (r = 0.996; p less than 0.0001), and has intra- and inter-assay coefficients of variation of between 5-9% and 7-11% respectively. 相似文献
22.
The alpha-like globin gene cluster in rabbits contains embryonic zeta-
globin genes, an adult alpha-globin gene, and theta-globin genes of
undetermined function. The basic arrangement of genes, deduced from
analysis of cloned DNA fragments, is 5'-zeta 0-zeta 1-alpha 1-theta 1- zeta
2-zeta 3-theta 2-3'. However, the pattern of restriction fragments
containing zeta- and theta-globin genes varies among individual rabbits.
Analysis of BamHI fragments of genomic DNA from 24 New Zealand white
rabbits revealed eight different patterns of fragments containing
zeta-globin genes. The large BamHI fragments containing genes zeta 0 and
zeta 1 are polymorphic in length, whereas a 1.9-kb fragment containing the
zeta 2 gene and the 3.5-kb fragment containing the zeta 3 gene do not vary
in size. In contrast to this constancy in the size of the restriction
fragments, the copy number of the zeta 2 and zeta 3 genes does vary among
different rabbits. No length polymorphism was detected in the BamHI
fragments containing the theta-globin genes, but again the copy number
varies for restriction fragments containing the theta 2 gene. The alpha 1-
and theta 1-globin genes are located in a nonpolymorphic 7.2-kb BamHI
fragment. The combined data from hybridization with both zeta and theta
probes shows that the BamHI cleavage pattern does not vary within the
region 5'-alpha 1-theta 1- zeta 2-zeta 3-theta 2-3', but the pattern
genomic blot-hybridization patterns for the progeny of parental rabbits
with different zeta-globin gene patterns shows that the polymorphic
patterns are inherited in a Mendelian fashion. Two different haplotypes
have been mapped based on the genomic blot-hybridization data. The
variation in the alpha-like globin gene cluster in the rabbit population
results both from differences in the copy number of the duplication block
containing the zeta-zeta-theta gene set and from the presence or absence of
polymorphic BamHI sites.
相似文献
23.
24.
S. A. Clulow M. J. Wilkinson R. Waugh E. Baird M. J. DeMaine W. Powell 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1991,82(5):545-551
Summary Seventeen potato dihaploids, produced by pollinating the tetraploid (2n = 48) cv Pentland Crown with pollen from Solanum phureja (2n = 24) dihaploid inducer clones, were studied. Since dihaploids are thought to develop parthenogenetically from unfertilized ovules they were expected to be euploid (2n = 24), but somatic chromosome counts showed that 15 of the 17 dihaploids were aneusomatic. Ten of the clones were predominantly diploid (2n = 24) with a proportion of hyperploid cells that contained 25 or 26 chromosomes. Five of the dihaploids contained variable numbers of triploid cells (2n = 36). RFLP analysis was used to determine whether the additional chromosomes were from S. phureja or S. tuberosum. Unique hybridizing fragments present in S. phureja but not in Pentland Crown were identified. These S. phureja-specific restriction fragments were present in some of the dihaploid offspring of Pentland Crown. Of the 5 clones that contained triploid cells 4 had S. phureja type banding. Four of the 10 aneusomatic clones that contained hyperploid cells had the unique S. phureja hybridizing fragments. We propose that ovules of Pentland Crown were fertilized by pollen from S. phureja and that the aneusomatic clones were derived from triploid zygotes from which some of the S. phureja chromosomes were eliminated. We consider that this is an additional mechanism of dihaploid formation in potato. 相似文献
25.
E V YoungLai M Wilkinson N Thompson A Byrne 《Canadian journal of physiology and pharmacology》1988,66(1):38-42
To examine the role of opioid neurons on luteinizing hormone (LH) secretion in the female rabbit, we determined LH release at timed intervals after naloxone administration to rabbits aged 25-150 days. The LH response to naloxone (10 mg/kg) was not significantly elevated until day 43 when LH rose 76-113% above basal levels at 40-80 min. In 56-day-old females the corresponding increase was 160% at 15 min and in 65- to 67-day-olds it was 154%. From 70 to 80 days of age the LH response was blunted and no significant elevations could be elicited. By contrast, naloxone-induced LH increases were again evident when rabbits were older than 100 days. At all ages no significant change in FSH concentrations was observed. In the adult females, naloxone at 2.5, 5, and 10 mg/kg caused increases in LH secretion which occasionally were high enough to induce ovulation as exemplified by elevated serum progesterone 4 days later. These data suggest that opioid peptides may be involved in the prepubertal rise in LH and in the normal inhibition of adult secretion in the female rabbit. 相似文献
26.
E V YoungLai M Wilkinson P Hibbert A McMahon J F Jarrell 《Canadian journal of physiology and pharmacology》1988,66(4):337-341
The binding of 125I-labelled human chorionic gonadotropin (HCG) was studied using thick slices (300 micron) of rabbit ovarian tissue. Binding was saturable, reversible, stereospecific, and of high affinity. The amount of binding was proportional to the number of slices used and could be destroyed by boiling. Ovarian slices from eight individual rabbits were found to have two binding sites for 125I-labelled HCG with KD values of 272 +/- 64 and 1263 +/- 274 pM and Bmax values of 25.7 +/- 5.3 and 94.1 +/- 18.8 fmol/mg protein, respectively. In a comparative study the KD and Bmax values were 351 +/- 151 pM and 25.3 +/- 11.1 fmol/mg protein with slices from one ovary and 134 +/- 24 pM and 109 +/- 32 fmol/mg protein with membranes from the contralateral ovary. These data suggest that the binding of HCG can be determined in live tissue. 相似文献
27.
Structure of the O-specific polysaccharide from the lipopolysaccharide of Serratia marcescens O8 总被引:1,自引:0,他引:1
Structural studies have been carried out on the O-specific polysaccharide from the lipopolysaccharide of the reference strain (CDC 1604-55) for serogroup O8 of Serratia marcescens. The polymer has a branched, tetrasaccharide repeating unit of D-galactose(Gal),D-glucose(Glc), and 2-acetamido-2-deoxy-D-glucose(GlcNAc) with the following structure: (Formula: see text). The anomeric configuration assigned to the glucose residue differs from that (beta) previously proposed [Tarcsay, L., Wang, C. S., Li, S.-C. and Alaupovic, P. (1973) Biochemistry 12, 1948-1955]. The structure of the O8 polymer is identical with that of one of two polymers present in the cell envelope of a strain (CDC 1783-57) of S. marcescens O14. 相似文献
28.
29.
Reports of naturally occurring Microsporum canis infection in the rabbit are rare. During the tenth week of a 91 day percutaneous toxicity study, 17 of 30 adult New Zealand white rabbits developed skin lesions varying from multiple papules to ringed lesions 1 X 2 cm in diameter. The lesions were not pruritic. Hair and scale samples taken from rabbits with lesions were cultured for dermatophytes. Based upon colony morphology and macroconidial characteristics, M canis identification was confirmed. At the time of necropsy, fluorescence was observed in three animals examined with a Wood's lamp, and of 10 rabbits that were positive on culture, seven were clinically normal. Microscopically, hair follicles contained spores and mycelia. The source of this outbreak was not determined. Tap water was cultured and found negative for pathogenic fungi. These findings document M canis infections in laboratory-housed New Zealand white rabbit, such an asymptomatic carrier state should be considered in this outbreak. The significance of dermatomycosis in laboratory animals is primarily as a zoonosis and a research complication. 相似文献
30.
Michael Ward Barry Wilkinson Geoffrey Turner 《Molecular & general genetics : MGG》1986,202(2):265-270
Summary An allele (oliC31) of the A. nidulans oliC gene has been cloned using homology with the equivalent gene from N. crassa. OliC31 codes for an oligomycin-resistant, triethyltin-hypersensitive form of subunit 9 of the mitochondrial ATP synthase complex. Direct selection for oligomycin-resistance was possible following transformation of A. nidulans with the oliC31 gene. The phenotypes of transformants cultured in the presence of oligomycin were indicative of the position of integration of the transforming plasmid within the genome. Subsequent recombination events involving the integrated oliC31 gene were also apparent from altered levels of resistance to oligomycin or triethyltin. This gene should prove useful as a marker for transformation of strains lacking auxotrophic lesions and in gene replacement or disruption experiments. 相似文献