全文获取类型
收费全文 | 1960篇 |
免费 | 190篇 |
专业分类
2150篇 |
出版年
2022年 | 18篇 |
2021年 | 25篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2016年 | 29篇 |
2015年 | 35篇 |
2014年 | 46篇 |
2013年 | 62篇 |
2012年 | 81篇 |
2011年 | 76篇 |
2010年 | 51篇 |
2009年 | 39篇 |
2008年 | 62篇 |
2007年 | 70篇 |
2006年 | 68篇 |
2005年 | 64篇 |
2004年 | 54篇 |
2003年 | 60篇 |
2002年 | 45篇 |
2001年 | 57篇 |
2000年 | 56篇 |
1999年 | 49篇 |
1998年 | 28篇 |
1997年 | 22篇 |
1996年 | 15篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 22篇 |
1992年 | 42篇 |
1991年 | 30篇 |
1990年 | 42篇 |
1989年 | 40篇 |
1988年 | 24篇 |
1987年 | 50篇 |
1986年 | 55篇 |
1985年 | 51篇 |
1984年 | 54篇 |
1983年 | 65篇 |
1982年 | 49篇 |
1981年 | 53篇 |
1980年 | 55篇 |
1979年 | 37篇 |
1978年 | 29篇 |
1977年 | 26篇 |
1976年 | 23篇 |
1975年 | 21篇 |
1974年 | 26篇 |
1973年 | 27篇 |
1972年 | 13篇 |
1970年 | 19篇 |
排序方式: 共有2150条查询结果,搜索用时 15 毫秒
81.
The assessment of cellular proliferation by immunohistochemistry: A review of currently available methods and their applications 总被引:12,自引:0,他引:12
Summary Immunohistochemical methods using antibodies to cell cycle-related antigens may be used as a means of assessing various aspects of proliferation in tissue, and have the important advantage of preserving the spatial orientation of proliferating cells in histological sections. Currently, the most widely available antibodies for this purpose are antibodies to bromodeoxyuridine (BrdU), Ki67 and antibodies to proliferating cell nuclear antigen (PCNA). BrdU is a thymidine analogue incorporated during the S phase of the cell cycle, which can be introduced by in vivo administration or by in vitro incubation, and monoclonal antibodies are available to display its localization. Ki67 demonstrates a nuclear antigen expressed in all phases of the cell cycle, except G0 and early G1, but can only be applied to frozen tissue. PCNA is a nuclear antigen which is essential for DNA synthesis, two commercially available antibodies to PCNA work in paraffin-embedded tissue, but may have different staining characteristics under different conditions of fixation. The main advantages and disadvantages of these different techniques are discussed, together with their main applications to date. 相似文献
82.
J T Kindt A Woods B M Martin R J Cotter Y Osawa 《The Journal of biological chemistry》1992,267(13):8739-8743
Recent studies have shown that a protein-bound heme adduct formed from the reaction of BrCCl3 with myoglobin was due to bonding of the proximal histidine residue through the ring I vinyl of a heme-CCl2 moiety. The present study reveals that BrCCl3 also reacts with the heme of reduced human hemoglobin to form two protein-bound heme adducts. Edman degradation and mass spectrometry provided evidence that these protein-bound heme adducts were addition products in which heme-CCL2 or heme-CCl3 were bound to cysteine residue 93 of the beta-chain of hemoglobin. It appeared that the cysteine residue was bonded regiospecifically to the ring I vinyl group of the altered heme moiety, because the nonprotein-bound products of the reaction included the beta-carboxyvinyl and alpha-hydroxy-beta-trichloromethylethyl derivatives of the ring I vinyl moiety of heme. The absorption spectra of the protein-bound adducts in both the oxidized and reduced states were highly similar to those described for hemichromes, which are thought to be involved in the formation of Heinz bodies and subsequent red cell lysis. 相似文献
83.
Characteristics of spontaneous embryonic loss in 21 mares were compared with those of 52 contemporary mares that maintained pregnancy. Embryonic losses were, in retrospect, grouped according to day of loss and length of the interovulatory interval, respectively, as follows: group 1, less than or equal to day 20 and less than or equal to 30 days (n = 10); group 2, less than or equal to day 20 and greater than 30 days (n = 3); and group 3, greater than day 20 and greater than 30 days (n = 8); ovulation was day 0. Mean diameter of the embryonic vesicle in group 1 was smaller (P less than 0.05) on days 12-18 than in the pregnancy-maintained group, but among the pregnancy-maintained group and the embryonic-loss groups, the mean individual growth rates of vesicles was similar (no significant difference). A more frequent (P less than 0.05) location of the vesicles in the uterine body on day 13 in group 1 was due to a greater proportion of small vesicles and for day 18 was due to a greater incidence of fixation failure. Luteal regression occurred at the expected time in 77% of the mares with loss sooner than day 20. Low concentration of progesterone on days 12, 15 and 18, a detected decrease in diameter of the corpus luteum on days 15 and 18, and an interovulatory interval of less than or equal to 30 days indicated that luteolysis was not prevented by the embryonic vesicle in group 1.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
84.
Prostaglandin E2 (PGE2) bound specifically (P less than 0.001) to ampullary and isthmic tissue on Day 2 and Day 5 after ovulation. No significant differences (P greater than 0.8) were detected between Day 2 and Day 5 in the specific binding of ampullary or isthmic tissue. Significantly more (P less than 0.05) PGE2 bound specifically to ampullary versus isthmic tissue on both days. Detection of PGE2-specific binding in the oviductal isthmus on Day 2 and Day 5 indicates that the oviduct is responsive to PGE2 when it is capable of transporting equine embryos. 相似文献
85.
J.A. Weber G.L. Woods D.A. Freeman D.K. Vanderwall 《Prostaglandins & other lipid mediators》1992,43(1)
Prostaglandin E2 (PGE2) secreted by Day-6, Day-7, Day-8 and Day-9 equine embryos (ovulation = Day 0) during in vitro incubation was measured by radioimmunoassay. Embryonic PGE2 secretion (ng/embryo/24 hr) was detectable on Day 6 (0.27±0.39), tended to increase (P <0.1) on Day 7 (0.57±0.88), and increased significantly (P <0.05) on Day 8 (2.23±0.86) and Day 9 (4.13±0.71). Embryo diameter at the start of the incubation period was linearly correlated (P <0.01) to embryonic PGE2 secretion. 相似文献
86.
Purification and Characterization of an Autolysin from Clostridium acetobutylicum 总被引:9,自引:8,他引:1 下载免费PDF全文
Jocelyn R. Webster Sharon J. Reid David T. Jones David R. Woods 《Applied microbiology》1981,41(2):371-374
A proteinaceous substance with antibiotic-like activity, resembling that of a bacteriocin, was isolated from an industrial-scale acetone-butanol fermentation of Clostridium acetobutylicum. The substance, purified by acetone precipitation, diethylaminoethyl cellulose chromatography, and polyacrylamide gel electrophoresis, was characterized as a glycoprotein with a molecular weight of 28,000. The glycoprotein was partially inactivated by certain protease enzymes. It had no effect on deoxyribonucleic acid, ribonucleic acid, or protein synthesis, and it did not result in the loss of intracellular adenosine triphosphate. The glycoprotein lysed sodium dodecyl sulfate-treated cells and cell wall preparations, and therefore it is referred to as an autolysin. The autolysin gene appeared to be chromosomal since plasmid deoxyribonucleic acid was not detected in the C. acetobutylicum strain. 相似文献
87.
88.
89.
90.
Antibacterial effect of the scandium and indium complexes of enterochelin on Escherichia coli 总被引:1,自引:0,他引:1
Enterochelin, the iron chelator produced by a number of pathogenic enterobacteria, appears to be an essential metabolite for multiplication within the host, where it transports iron from the host iron-binding proteins to the bacteria. Previous work showed that complexes of enterochelin containing either scandium (Sc3+) or indium (In3+) exerted a bacteriostatic effect on Klebsiella pneumoniae in serum, whilst the Sc3+ complex exerted a significant therapeutic effect on mice infected with K. pneumoniae. These observations have now been extended to a number of pathogenic serotypes of Escherichia coli including those carrying either the K1 antigen or the ColV plasmid. The Sc3+ and In3+ complexes each exert a bacteriostatic effect on these organisms growing in either whole serum or media containing an iron-binding protein. Evidence is presented that the Sc3+ complex may act as a competitive inhibitor of the Fe3+ complex. In contrast to their effects on K. pneumoniae, sideramines other than enterochelin fail to reverse the bacteriostatic effect of the Sc3+ complex of enterochelin in E. coli, suggesting that the complex produces a more profound derangement of metabolism in this organism. The Sc3+ complex exerts a significant therapeutic effect on E. coli infections in mice although the In3+ complex is less active. 相似文献