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591.
In the research fields of experimental embryology, teratological testing, and developmental engineering in avian species, a knowledge of normal embryonic development is necessary so that research may be performed efficiently and precisely. A series of normal stages based on external appearance has been established in both chicken and quail embryos. Those based on skeletal features, however, have not been elucidated. The present study newly established a series of normal stages for the development of the Japanese quail embryo skeleton. This series is composed of 15 stages determined by observing the timing of chondrification and calcification of the skeleton every 24 h, from 3 to 17 days of incubation. Cartilage and ossified bones were stained blue and red with Alcian blue 8GX and alizarin red S, respectively. These skeletogenous stages of the Japanese quail embryo will be useful as a normal control not only in studies of experimental embryology, teratological testing, and developmental engineering, but also in the analysis of mutant embryos with skeletal abnormalities. 相似文献
592.
A. Kume Naoko Tsuboi Takami Satomura Masayo Suzuki Masaaki Chiwa Kaneyuki Nakane Naoki Sakurai Takao Horikoshi Hiroshi Sakugawa 《Trees - Structure and Function》2000,14(6):305-311
The decline of Japanese red pine trees (Pinus densiflora Sieb. et Zucc.) at Mt. Gokurakuji (693 m a.s.l.), 30 km west of Hiroshima city, west Japan, was studied. The effects of air
pollution and acid deposition on the physiological characteristics of the trees, especially those of the needles, were investigated.
Ozone concentration was not correlated with the physiological status of the needles and SO2 concentration was not high in the declined area. NO2 concentration correlated negatively with needle longevity while it correlated positively with ethylene emission from 1-year-old
needles. Average needle longevity was about 2.8 years in non-declined areas; however the longevity was 1.3 years in the most
polluted area. The minimal fluorescence at night (F
0)of 1-year-old needles decreased with increasing NO2 concentration. The maximum stomatal conductance (gl), net photosynthesis (P
n)and intercellular CO2 concentration (C
i) in the declined areas were lower than in the non- declined areas (about 50%, 30% and 20% lower, respectively). The lower
C
isuggested that the major part of the decrease in P
ncan be explained by stomatal restriction. The soil pH, N content and C/N ratio showed no significant difference between the
declined and non-declined areas. The physiological disorders of needles were due to the damage by air pollutants, and important
roles of NO2 are suggested. Lowering of P
n and the shortening of needle longevity appear to be the main causes of the decline in pines in the forest decline area.
Received: 16 December 1998 / Accepted: 7 January 2000 相似文献
593.
594.
595.
C. V. Wylie P. K. Nakane G. B. Pierce 《Differentiation; research in biological diversity》1973,1(1):11-20
A pool of nondividing tumour cells, believed to be nonproliferating stem cells (Go ), has been identified in mammary adenocarcinomas of mice. To determine whether or not some of these cells might be postmitotic differentiated progeny of stem cells, mice bearing spontaneous tumours were either pulsed or perfused with tritium-labelled thymidine for five days, and light and electron autoradiography was performed using standard methods. Unlabelled cells (that had not synthesized DNA for five days) had a range of differentiation, but many of the cells were well differentiated. This observation supports the concept that many of the non-proliferating tumour cells were postmitotic as a result of differentiation and the balance were nonproliferating stem cells (Go ). The latter presumably did not divide because of environmental conditions. 相似文献
596.
According to development of the city, it has been revealed that demographic characteristics and living condition, as well as health status, have been differentiated among areas within it. On the causal relationships between urban growth and health, the present study shows no evidence, but a significant correlation between population density and demographic characteristics, and health, especially in maternal child health, have been observed in the same city (Takemoto et al., 1988). Considering the regionalization of characteristics in man and his environment within a city, public health activities based on the assessment of health needs in each community should be developed in urbanized society. 相似文献
597.
A trypanocidal drug suramin [hexasodium sym-bis(m-amino-benzoyl-m-amino-p-methylbenzoyl-1-naphthylamino-4, 6, 8-trisulfonate)carbamide] was found to be a potent inhibitor of the activities of DNA primase and polymerase alpha from human KB cells. The mechanism of the inhibition by suramin was, however, quite different by these two polymerases. In the case of DNA primase, suramin inhibited competitively the incorporation of a nucleotide substrate, GTP, on the template polydeoxycytidylate, while the polymerase alpha was inhibited competitively by the drug with respect to the template primer (activated DNA). The observed inhibitory effect of suramin on nucleic acid synthesis seems to explain yet unknown mechanism of trypanocidal action of the drug. 相似文献
598.
Biochemical analysis of the male germ cell-associated kinase (mak) gene, which was isolated recently by using weak cross-hybridization with the v-ros tyrosine kinase gene, revealed that the gene was highly expressed in mammalian testicular germ cells, but not in ovarian cells. In order to identify the cells which express the mak gene in more detail, we localized mak mRNA in frozen sections of mouse testis by non-radioactive in situ hybridization. In this study, we utilized thymine-thymine (T-T) dimerized mak cDNA as a haptenic, non-radioactive probe, and the signal was detected enzyme-immunohistochemically by using an anti-T-T antibody. As a result, mak mRNA was localized intensely in late pachytene (stage X) and diplotene (stage XI) spermatocytes, and faintly in dividing spermatocytes (stage XII) and early round spermatids (stage I-II), suggesting that the gene may play an important role in the phase around meiotic cell division, but not throughout the entire meiosis. 相似文献
599.
Daisuke Nakane Kohki Murata Tsuyoshi Kenri Keigo Shibayama Takayuki Nishizaka 《PLoS pathogens》2021,17(6)
Length control is a fundamental requirement for molecular architecture. Even small wall-less bacteria have specially developed macro-molecular structures to support their survival. Mycoplasma pneumoniae, a human pathogen, forms a polar extension called an attachment organelle, which mediates cell division, cytadherence, and cell movement at host cell surface. This characteristic ultrastructure has a constant size of 250–300 nm, but its design principle remains unclear. In this study, we constructed several mutants by genetic manipulation to increase or decrease coiled-coil regions of HMW2, a major component protein of 200 kDa aligned in parallel along the cell axis. HMW2-engineered mutants produced both long and short attachment organelles, which we quantified by transmission electron microscopy and fluorescent microscopy with nano-meter precision. This simple design of HMW2 acting as a molecular ruler for the attachment organelle should provide an insight into bacterial cellular organization and its function for their parasitic lifestyles. 相似文献
600.
Effects of IL-1 and cortisol on beta-adrenergic receptors, cell proliferation, and differentiation in cultured human A549 lung tumor cells 总被引:1,自引:0,他引:1
T Nakane T Szentendrei L Stern M Virmani J Seely G Kunos 《Journal of immunology (Baltimore, Md. : 1950)》1990,145(1):260-266
The effects of IL-1 and cortisol, and their interactions on the density of beta-adrenergic receptors (beta AR), cell proliferation, and the adherence of cells to plastic were studied in cultured human A549 lung tumor cells. The density of beta AR, assayed by 125I-pindolol binding, was increased two- to threefold by a 24-h incubation of the cells with IL-1 alpha, IL-1 beta, and TNF-alpha (EC50: 2.7, 8.2, and 24 pM, respectively), although a series of other cytokines and growth factors did not have this effect. Cortisol also increased beta AR density (EC50: 30 nM) and markedly potentiated the effects of IL-1 alpha, IL-1 beta, and TNF-alpha. Neither IL-1 nor cortisol influenced the proportion of cell surface vs internalized beta AR. The IL-1-induced increase in beta AR density was half-maximal after 6 h, was reversible at a similar rate, and was blocked by 1 microM of cycloheximide. The effect of IL-1 on beta AR was specific, as the density of glucocorticoid receptors, measured by 3H-dexamethasone binding, was reduced by IL-1. Both cortisol and IL-1 potentiated the isoproterenol-induced increase in cAMP accumulation. IL-1 inhibited cell proliferation and thymidine uptake, and increased the adherence of A549 cells to the plastic culture flask, as quantified by a cell detachment assay. The effect of IL-1 on cell adherence was not inhibited by cycloheximide. Cortisol decreased cell adherence and prevented the IL-1-induced increase in adherence. The results indicate that multiple effects of IL-1 in a cultured tumor cell line involve different mechanisms, suggesting heterogeneity of IL-1R and/or coupling of IL-1R to distinct, nuclear, and nonnuclear, effector pathways. 相似文献