全文获取类型
收费全文 | 879篇 |
免费 | 34篇 |
专业分类
913篇 |
出版年
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 26篇 |
2020年 | 11篇 |
2019年 | 16篇 |
2018年 | 27篇 |
2017年 | 15篇 |
2016年 | 22篇 |
2015年 | 39篇 |
2014年 | 41篇 |
2013年 | 68篇 |
2012年 | 57篇 |
2011年 | 73篇 |
2010年 | 30篇 |
2009年 | 23篇 |
2008年 | 52篇 |
2007年 | 47篇 |
2006年 | 35篇 |
2005年 | 32篇 |
2004年 | 45篇 |
2003年 | 33篇 |
2002年 | 25篇 |
2001年 | 26篇 |
2000年 | 16篇 |
1999年 | 11篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 9篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 13篇 |
1990年 | 11篇 |
1989年 | 14篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 5篇 |
1984年 | 4篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有913条查询结果,搜索用时 0 毫秒
901.
Y Hayashi A Reszka T Iguchi B Reinish T Kawashima A F Horwitz 《Cell structure and function》1991,16(2):135-139
We transfected rat pheochromocytoma (PC12) cells with a cDNA encoding chicken integrin beta 1 subunit. The chicken integrin beta 1 subunit produced in stable transfectants associated with two major alpha subunits of rat integrins to form interspecific chimeric receptors. These receptors mediated cell spreading and initial neurite outgrowth on laminin as did corresponding endogenous integrins, although they were slightly less effective in inducing cell adhesion to laminin. These results indicate that chicken integrin beta 1 may functionally substitute for beta 1 subunit of rat integrins in PC12 cells. Apparently, the structure of the integrin beta 1 subunit is highly conserved in the evolution of these species. 相似文献
902.
K Hirota T Gomi R Kishimoto M Iguchi K Hayakawa H Nakagawa 《Journal of biochemistry》1981,89(1):153-160
In studies with a synthetic androgen, R 1881, an androgen-binding component was found in the cytosol of human placental villi. Kinetic analysis indicated that the Kd value of this component was 1.4 nM at 0-4 degrees C and that binding of R 1881 amounted to 277 +/- 73 fmol/mg protein. glycerol density gradient ultracentrifugation showed a peak of binding activity in the 8S region in a medium of low ionic strength, but in the 4.5S region in a medium containing 9.5 M KCl. The R 1881-binding component was inactivated by mild heat- or trypsin-treatment, but not by treatment with DNase or RNase. Most of the R 1881-binding activity was sedimented at 20 to 40% saturation of ammonium sulfate. These findings indicate that the R 1881-binding component in human placental cytosol is quite similar in its characteristics to androgen receptors, which are present in various androgen-responsive organs. Testosterone was a more potent competitor of R 1881-binding than DHT or cyproterone acetate. Scatchard plots indicated that the binding site of testosterone was identical with that of R 1881. These findings suggest that the androgen receptor in placental cytosol is specific for testosterone. The Kd value for testosterone was calculated to be 3.2 nM. 相似文献
903.
Sho Hotta Satoshi Uchiyama Kenji Ichihara 《Bioscience, biotechnology, and biochemistry》2020,84(9):1820-1830
ABSTRACT Brazilian red propolis reportedly has reactive oxygen species (ROS) scavenging effects in vitro, but the cellular mechanisms remain unclear. In the present study, the effects of an ethanol extract of Brazilian red propolis (EERP) on the Nrf2-ARE intracellular antioxidant pathway were examined in vitro and in vivo. EERP and its constituents transactivated the reporter gene through the ARE sequence and enhanced the expression of Nrf2-regulated genes in HEK293 cells. It also increased Nrf2 protein in the nucleus, which was partially inhibited by kinase inhibitors. Furthermore, EERP suppressed ROS generation and cytotoxicity induced by tert-butyl hydroperoxide. In vivo, orally administered EERP increased the expression of Nrf2-regulated genes in mice liver. These results suggest that EERP is a potential resource for preventing oxidative stress-related diseases as an Nrf2 inducer. 相似文献
904.
Sho Kato Takayuki Motoyama Yushi Futamura Masakazu Uramoto Toshihiko Nogawa Toshiaki Hayashi 《Bioscience, biotechnology, and biochemistry》2020,84(6):1303-1307
ABSTRACTWe identified the biosynthetic gene cluster for lucilactaene, a cell cycle inhibitor from a filamentous fungus Fusarium sp. RK 97–94. The luc1 knockout strain accumulated demethylated analogs, indicating the involvement of Luc1 methyltransferase in lucilactaene biosynthesis. Lucilactaene showed potent antimalarial activity. Our data suggested that methylation and ether ring formation are essential for its potent antimalarial activity. 相似文献
905.
906.
Two basic types of spermatozoan aggregates, spermatophores and spermatozeugmata, found in 14 different species of sharks, one species of skate, and one species of chimaera (holocephalan), were investigated using light and scanning electron microscopy. Spermatophores, aggregates (usually 1,000–6,000 μm in diameter and larger) of randomly clumped sperm embedded in and surrounded by an eosinophilic matrix, were found in Alopias superciliosus, Odontaspis taurus, Carcharodon carcharias, Isurus oxyrinchus, and Lamna nasus. Three types of spermatozeugmata, sperm structures without a surrounding capsule or matrix, are described. The first, clumps of 60–200 sperm unbound in a supporting matrix, are found in Squalus acanthias and Hydrolagus colliei. In the second type, single-layered spheres are formed of sperm clumps with the sperm heads bound in a common supporting matrix. These are found in Carcharhinus limbatus and Carcharhinus plumbeus. The third type of spermatozeugmata are large multilayered, compound structures formed by the accretion of several single-layered aggregates. These multilayered structures characteristically are found in Carcharhinus falciformis, C. limbatus, Carcharhinus obscurus, C. plumbeus, Carcharhinus porosus, Prionace gluaca, Rhizoprionodon terraenovae, and Sphyrna lewini. Sperm aggregates of all types are stored between the septa and in the lumen of the terminal ampulla of the epididymis. In their various forms they are the final product of the mature male elasmobranch reproductive tract. In a male with mature claspers, the presence of sperm aggregates is a more reliable indicator of maturity and sexual activity than is clasper condition alone. © 1994 Wiley-Liss, Inc. 相似文献
907.
Pathways to chronic inflammation in rheumatoid synovitis 总被引:8,自引:0,他引:8
D Cavender D Haskard C L Yu T Iguchi P Miossec N Oppenheimer-Marks M Ziff 《Federation proceedings》1987,46(1):113-117
Postcapillary venules resembling the high endothelial venules (HEVs) of lymphoid tissues have often been observed at sites of chronic inflammation. We have therefore postulated that such venules may be an important site of lymphocyte migration into rheumatoid synovial membrane and that inflammatory cell products may act on endothelial cells (ECs) to increase lymphocyte emigration. Electron microscopic examination of rheumatoid synovial membranes showed that a strong correlation existed between the proportion of lymphocytes in perivascular tissue and the height/base ratio of the ECs in those areas. In addition, binding experiments showed that peripheral blood mononuclear cells preferentially bound to ECs in sections of rheumatoid synovial membrane that had the morphological appearance of HEVs. In vitro binding experiments, in which lymphocyte adhesion to human umbilical vein EC monolayers was measured, showed that adhesion was enhanced by preincubation of the ECs with interferon-gamma or interleukin 1 (IL 1). The central role of IL 1 in increasing lymphocyte migration into the rheumatoid synovial membrane was also supported by the findings that IL 1 is chemotactic for lymphocytes, ECs can secrete IL 1, and IL 1 activity is readily detectable in synovial fluids of rheumatoid arthritis patients. 相似文献
908.
Antibacterial activity of snail mucus mucin 总被引:1,自引:0,他引:1
909.
We studied the response of plasma 7B2 to LHRH and ovine corticotropin releasing hormone (o-CRH) in healthy young subjects. The plasma 7B2 concentration significantly increased from 78.3 +/- 7.5 (mean +/- SEM) to 102.0 +/- 6.0 ng/L (142.7 +/- 12.7% of the basal value; P less than 0.01) following iv administration of LHRH in seven young subjects. On the other hand, no increase in plasma 7B2 was found after iv administration of o-CRH in six young subjects. These results, together with our previous report of no increase in plasma 7B2 after administration of TRH and GHRH in young subjects, suggest that pituitary 7B2 may be present in gonadotrophs and be released only by LHRH in physiological conditions. 相似文献
910.
Organisms that migrate between rivers and the sea inevitably pass through estuarine habitats. Despite the potential importance
of salinity and temperature fluctuations for metabolic adaptation, little is known about the impact of environmental changes
in estuaries on the survival of residents. Ayu (Plecoglossus altivelis) is a migratory fish that inhabits estuarine brackish water in its early life stages. The recent decline in the abundance
of populations ascending into rivers is of concern for local biodiversity. The present study aims to elucidate the ecological
processes that determine the early success of Ayu larvae under variable environmental conditions. The effects of salinity
and water temperature on the endogenous growth of newly hatched larvae from the same brood were examined experimentally based
on morphological and metabolic characteristics. High salinity and high water temperature together appeared to require more
energy for larval osmoregulation, resulting in the acceleration of yolk depletion and reduced growth of the notochord. Increasing
the osmoregulative cost during the yolk-sac stage resulted in the faster induction of a state of starvation. Seawater is considered
to have an adverse effect on the survival of newly hatched larvae, as it lowers the efficiency of foraging and predator avoidance
due to an energetic tradeoff. More attention should be paid to the significance of estuarine environments involving brackish
waters to ensure the early survival of amphidromous fish such as Ayu. 相似文献