全文获取类型
收费全文 | 3411篇 |
免费 | 169篇 |
出版年
2023年 | 12篇 |
2022年 | 19篇 |
2021年 | 40篇 |
2020年 | 17篇 |
2019年 | 34篇 |
2018年 | 54篇 |
2017年 | 30篇 |
2016年 | 66篇 |
2015年 | 103篇 |
2014年 | 125篇 |
2013年 | 222篇 |
2012年 | 255篇 |
2011年 | 231篇 |
2010年 | 146篇 |
2009年 | 116篇 |
2008年 | 228篇 |
2007年 | 226篇 |
2006年 | 210篇 |
2005年 | 189篇 |
2004年 | 228篇 |
2003年 | 189篇 |
2002年 | 220篇 |
2001年 | 31篇 |
2000年 | 37篇 |
1999年 | 33篇 |
1998年 | 37篇 |
1997年 | 42篇 |
1996年 | 45篇 |
1995年 | 32篇 |
1994年 | 32篇 |
1993年 | 29篇 |
1992年 | 32篇 |
1991年 | 31篇 |
1990年 | 26篇 |
1989年 | 28篇 |
1988年 | 20篇 |
1987年 | 24篇 |
1986年 | 17篇 |
1985年 | 12篇 |
1984年 | 10篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 13篇 |
1980年 | 15篇 |
1979年 | 9篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1975年 | 5篇 |
1974年 | 5篇 |
排序方式: 共有3580条查询结果,搜索用时 78 毫秒
1.
Young-Jun Park Tomotaro Nishikawa Norihiko Tomooka Kazuhiro Nemoto 《Molecular breeding : new strategies in plant improvement》2012,30(1):511-520
Polymorphisms at the Waxy locus of Amaranthus caudatus L. collected from a wide range of regions were used to investigate genetic diversity and mutation sites. A comparison of the Waxy locus revealed a very high level of sequence conservation. This result clearly showed low environmental and evolutionary variability in the Waxy gene. We also performed screening to confirm the mutation sites in the coding sequences of all accessions. The results indicate that one insertion in the coding region of Waxy genes was responsible for the change in perisperm starch leading to the waxy phenotype in all accessions of this species, and thus that a single mutation event altered the regulation of the Waxy gene during the domestication of this crop. In addition, phylogenetic analysis showed that waxy phenotypes within each of three species, A. caudatus, A. cruentus and A. hypochondriacus, originated separately or differentiated from nonwaxy phenotypes of each species through a single mutational event (i.e., a frame shift or base substitution). We also compared obvious structural features of the coding sequence of waxy and nonwaxy phenotypes with those of low-amylose phenotypes in A. caudatus. The Waxy coding sequences of low-amylose phenotypes do not show polymorphisms and are identical with those of waxy phenotypes. This could mean that there is another gene that encodes a key enzyme responsible for amylose synthesis as the elementary quantity in tissues other than perisperm in A. caudatus. 相似文献
2.
Kazuhiro Nakaya 《Ichthyological Research》1988,35(2):133-141
Additional specimens of the rareApristurus herklotsi are reported, and the characteristic features of this species are discussed.A. herklotsi is concluded to be a distinct species, having a very long snout, a narrow distance between the nostrils, a long caudal fin,
a short abdomen, numerous teeth on both jaws, and a low number of monospondylous vertebrae.A. herklotsi appears to be mature at about 44 cm in total length. 相似文献
3.
Mark T Uhlik Amy N Abell Bruce D Cuevas Kazuhiro Nakamura Gary L Johnson 《Biochimie et biologie cellulaire》2004,82(6):658-663
Mitogen-activated protein kinase (MAPK) pathways are activated by a plethora of stimuli. The literature is filled with papers describing the activation of different MAPKs by almost any stimulus or insult imaginable to cells. In this review, we use signal transduction wiring diagrams to illustrate putative upstream regulators for the MAPK kinase kinases, MEKK1, 2, and 3. Targeted gene disruption of MEKK1, 2, or 3 defined phenotypes for each MEKK associated with loss of specific MAPK regulation. Genetic analysis of MEKK function clearly defines specific components of the wiring diagram that require MEKK1, 2, or 3 for physiological responses. We propose that signal transduction network wiring diagrams are valuable tools for hypothesis building and filtering physiologically relevant phenotypic responses from less connected protein relations in the regulation of MAPK pathways. 相似文献
4.
Kazuhiro Yamaguchi Klaus D. Jürgens Heinz Bartels Johannes Piiper 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1987,157(1):1-9
Summary To estimate the advantage of the small red blood cells (RBC) of high-altitude camelids for O2 transfer, the kinetics of O2 uptake into and release from the RBC obtained from llama, vicuña and alpaca were investigated at 37°C with a stopped-flow technique. O2 transfer conductance of RBC (G) was estimated from the rate of O2 saturation change and the corresponding O2 pressure difference between medium and hemoglobin. For comparison, O2 kinetics for the RBC of a lowaltitude camelid (dromedary camel) and the pygmy goat were determined and previously measured values for human RBC were used. O2 transfer of RBC was found to be strongly influenced by extracellular diffusion, except with O2 release into dithionite solutions of sufficiently high concentration (>30 mM). TheG values measured in these standard conditions,G
st (in mmol · min–1 · Torr–1 · (ml RBC)–1) were: high-altitude camelids, 0.58 (averaged for llama, alpaca and vicuña since there were no significant interspecific differences); camel 0.42; goat, 0.42; man, 0.39. The differences can in part be attributed to expected effects of the size and shape of the RBC (volume, surface area, mean thickness), as well as to the intracellular O2 diffusivity which depends on the concentration of cellular hemoglobin. The highG
st of RBC of highaltitude camelids may be considered to enhance O2 transfer in lungs and tissues. But the O2 transfer conductance of blood, , equal toG
st multiplied by hematocrit (in mmol · min–1 · Torr–1 · (ml blood)–1), was only slightly higher as compared to other species: 0.20 (llama, alpaca, vicuña), 0.14 (camel), 0.18 (goat), 0.17 (man).Abbreviations
DPG
2,3-diphosphoglycerate
-
G
conductance
-
Hb
hemoglobin
-
RBC
red blood cells
-
percent saturation of hemoglobin 相似文献
5.
Fibroblast cells from two Japanese patients with Bloom's syndrome (BS) and normal donors were studied for the inactivation of colony-forming ability and the induction of sister-chromatid exchanges (SCEs) after N-ethyl-N-nitrosourea (ENU) treatment. The reduction of ENU-induced SCEs as a function of post-treatment incubation time was also compared between BS and normal fibroblasts. BS cells were approximately 4 times more sensitive than normal cells to the lethal effect of ENU and remarkably hypersensitive to the SCE induction by ENU. The post-treatment incubation of ENU-treated normal cells in the fresh medium resulted in a time-dependent decrease of the SCE level until 6 h after which time the SCE level remained the plateau of about 50% of the initial level. In contrast, the ENU-induced SCEs in BS cells decreased much more slowly with post-treatment incubation time and its half life was 24 h. These results collectively support the view that BS cells may be defective in the rapid repair of certain type(s) of DNA damages induced by ENU. 相似文献
6.
Sister-chromatid exchanges induced by ultraviolet light in Bloom's syndrome fibroblasts 总被引:1,自引:0,他引:1
The relationships between the cytotoxic effect of ultraviolet light and the UV-induced sister-chromatid exchanges (SCEs) were compared among fibroblast cell strains from two unrelated Bloom's syndrome (BS) patients, one xeroderma pigmentosum (XP) patient belonging to complementation group A and two unrelated normal controls. The "net" induced SCEs as a function of UV fluence, obtained by subtracting spontaneous SCEs from observed SCEs, were much higher in both BS cells and XP group A cells than in normal cells. The relative efficiency of induced SCE, defined as the "net" induced SCEs as a function of surviving fraction after UV irradiation, was higher in BS cells than in normal and XP cells, and there was essentially no difference between XP and normal cells. These results imply that in addition to the extremely high frequency of spontaneous SCEs, the increased efficiency in UV induction of SCEs may reflect the intrinsic defect(s) in BS cells. 相似文献
7.
Harringtonine showed cross resistance in adriamycin-resistant murine leukemia P388 (P388/ADM) and human leukemia K562 (K562/ADM) cells. The relative resistance of the P388/ADM and K562/ADM cells to harringtonine was about 7 and 40, respectively. Calcium influx blockers, diltiazem and the biscoclaurine alkaloid cepharanthine enhanced the cytotoxicity of harringtonine in P388/ADM and K562/ADM cells. The extent of enhancement was different for the two drugs, and up to a 9- to 10-fold increase in harringtonine cytotoxicity occurred in P388/ADM cells, and 14- to 22-fold enhancement in K562/ADM cells with diltiazem or cepharanthine. Harringtonine resistance of P388/ADM was circumvented completely, and the resistance of K562/ADM was circumvented partially, by diltiazem or cepharanthine. The mechanism of enhanced cytotoxicity by diltiazem and cepharanthine is probably inhibition of active efflux of harringtonine in P388/ADM and K562/ADM cells. 相似文献
8.
Kazuhiro Tanaka 《Archives of microbiology》1990,155(1):18-21
The ability of Desulfovibrio vulgaris strain Marburg (DSM 2119) to oxidize alcohols was surveyed in the presence and absence of hydrogen-scavenging anaerobes, Acetobacterium woodii and Methanospirillum hungatei. In the presence of sulfate, D. vulgaris grew not only on ethanol, 1-propanol, and 1-butanol, but also on isobutanol, 1-pentanol, ethyleneglycol, and 1,3-propanediol. Metabolism of these alcohols was simple oxidation to the corresponding acids, except with the last two substrates: ethyleneglycol was oxidized to glycolate plus acetate, 1,3-propanediol to 3-hydroxypropionate plus acetate. Experimental evidence was obtained, suggesting that 2-methoxyethanol was not utilized by all the cells of strain marburg, but by a spontaneous mutant. 2-Methoxyethanol was oxidized to methoxyacetate by the mutant. Co-culture of strain Marburg plus A. woodii grew on ethanol, 1-propanol, 1-butanol, and 1,3-propanediol in the absence of sulfate. Co-culture of strain Marburg plus M. hungatei grew on ethanol, 1-propanol, and 1-butanol, but not on ethyleneglycol and 1,3-propanediol, Co-culture of the mutant plus A. woodii or M. hungatei did not grow on 2-methoxyethanol. 相似文献
9.
Masanori Ito Kazuhiro Yoshida Eikai Kyo Ayse Ayhan Hirofumi Nakayama Wataru Yasui Hisao Ito Eiichi Tahara 《Virchows Archiv. B, Cell pathology including molecular pathology》1990,59(1):173-178
We have examined the expression of mRNAs for epidermal growth factor (EGF), transforming growth factor-alpha (TGF-α), EGF
receptor (EGFR), PDGF-A chain (PDGFA), PDGF-B chain (PDGFB) and PDGF receptor (PDGFR) genes in seven human colorectal carcinoma
cell lines and 18 human colorectal carcinomas.
In surgically resected specimens of the 18 colorectal tumors, TGF-α, EGFR, PDGFA, PDGFB and PDGFR mRNAs were detected at various
levels in 15 (83%), 9 (50%), 18 (100%), 8 (44%) and 12 (67%), respectively. They were also detected in normal tissues. Interestingly,
EGF mRNA was detected in only five (28%) of the tumors, but not in normal mucosa. Expression of EGF was also confirmed immunohistochemically
in tumor cells. Of the five tumors expressing EGF, four expressed EGFR mRNA and showed a tendency to invade veins and lymphatics.
All the colorectal carcinoma cell lines expressed TGF-α mRNA, and five cell lines expressed EGFR mRNA simultaneously. Production
of TGF-α protein by DLD-1 and CoLo320DM cells was confirmed by TGF-α specific monoclonal antibody binding assay. The spontaneous3H-thymidine uptake by DLD-1 was suppressed by an anti-TGF-α monoclonal antibody. PDGFA and PDGFB mRNA were also expressed
in four cell lines, but PDGFR and EGF mRNA was not detected. These results suggest that human colorectal carcinomas express
multi-loops of growth factors and that TGF-α produced by tumor cells functions as an autocrine growth factor in human colonic
carcinoma. 相似文献
10.
Tatsumi Nagahama Mitsuru Takata 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1990,167(1):1-10
1. | Spikes in Aplysia MA1 neurons produced excitatory (EJPs), inhibitory (IJPs), and diphasic inhibitory-excitatory junction potentials in different fibers of the buccal muscles. |
2. | The IJPs following the MA1 spikes were recorded in the muscle fibers innervated by the jaw-closing motoneurons. The depolarization of muscle fibers produced by the motoneurons was largely suppressed by simultaneous MA1 firing, suggesting that the MA1 neurons make a direct connection to a part of the muscle fibers innervated by these motoneurons and inhibit them. |
3. | The excitatory and inhibitory components of the junction potentials produced by MA1 were reversibly blocked by hexamethonium and d-tubocurarine, respectively. In contrast, the EJPs produced by the jaw-closing motoneurons were blocked by an amino acid antagonist, suggesting that the MA1 neurons and the jaw-closing motoneurons use different transmitters in the nerve-muscle junctions. |
4. | The jaw movement produced by the jaw-closing motoneurons was suppressed by simultaneous MA1 firing, and the suppression was released by d-tubocurarine, suggesting that the IJPs produced by MA1 may contribute to the suppression of jaw movement. The firing of MA1 produced the vertical movement of the buccal muscles, which was blocked by hexamethonium, suggesting that the EJPs produced by MA1 may contribute to the vertical movement. |