全文获取类型
收费全文 | 3603篇 |
免费 | 282篇 |
国内免费 | 3篇 |
专业分类
3888篇 |
出版年
2022年 | 22篇 |
2021年 | 27篇 |
2019年 | 23篇 |
2018年 | 28篇 |
2017年 | 29篇 |
2016年 | 57篇 |
2015年 | 94篇 |
2014年 | 102篇 |
2013年 | 177篇 |
2012年 | 197篇 |
2011年 | 171篇 |
2010年 | 89篇 |
2009年 | 88篇 |
2008年 | 165篇 |
2007年 | 178篇 |
2006年 | 136篇 |
2005年 | 149篇 |
2004年 | 139篇 |
2003年 | 129篇 |
2002年 | 154篇 |
2001年 | 131篇 |
2000年 | 135篇 |
1999年 | 107篇 |
1998年 | 58篇 |
1997年 | 53篇 |
1996年 | 33篇 |
1995年 | 37篇 |
1994年 | 33篇 |
1993年 | 40篇 |
1992年 | 77篇 |
1991年 | 75篇 |
1990年 | 69篇 |
1989年 | 87篇 |
1988年 | 55篇 |
1987年 | 62篇 |
1986年 | 56篇 |
1985年 | 71篇 |
1984年 | 67篇 |
1983年 | 38篇 |
1982年 | 37篇 |
1981年 | 28篇 |
1979年 | 44篇 |
1978年 | 30篇 |
1977年 | 37篇 |
1976年 | 22篇 |
1975年 | 25篇 |
1974年 | 26篇 |
1973年 | 26篇 |
1972年 | 24篇 |
1970年 | 23篇 |
排序方式: 共有3888条查询结果,搜索用时 15 毫秒
101.
102.
D. Smith Y. Yanai Y.-G. Liu S. Ishiguro K. Okada D. Shibata R.F. Whittier N.V. Fedoroff 《The Plant journal : for cell and molecular biology》1996,10(4):721-732
The transposition patterns of the Ds —GUS transposon T-DNA in 23 independent single-copy lines have been characterized and the map positions of 10 of them on three of the five Arabidopsis chromosomes are reported. Using overexpressed Activator ( Ac ) elements as a transposase source, it was found that the primary determinant of transposition frequency is the insertion site of the Ac -T-DNA. Neither the structure of the transposon T-DNA nor, in most cases, its insertion site have a significant effect on transposition frequency. Both the frequency and timing of transposition are influenced by the parent through which the transposon and transposase T-DNAs are transmitted. Overall, nearly 75% of plants in which excision has occurred bear a reinserted element and very short-range transpositions predominate, underlining the advantage of using mapped transposons for insertional mutagenesis. 相似文献
103.
Epidermal growth factor stimulates proliferation of mouse uterine epithelial cells in primary culture 总被引:1,自引:0,他引:1
Shiraga M Komatsu N Teshigawara K Okada A Takeuchi S Fukamachi H Takahashi S 《Zoological science》2000,17(5):661-666
Epidermal growth factor (EGF) is one of growth factors that are thought to mediate the stimulatory effects of estrogen on the proliferation of uterine epithelial cells. The present study was attempted to obtain direct evidence for the mitogenic effects of EGF on uterine epithelial cells, and to prove that EGF and EGF receptors are expressed in these cells. Mouse uterine epithelial cells were isolated from immature female mice and cultured with or without EGF for 5 days. EGF (1 to 100 ng/ml) significantly increased the number of uterine epithelial cells, and the maximal growth (141.9+/- 8.3% of controls) was obtained at a dose of 10 ng/ml. In addition, EGF (0.1 to 100 ng/ml) increased the number of DNA-synthesizing cells immunocytochemically detected by bromodeoxyuridine uptake to the nucleus. Northern blot analysis revealed that the uterine epithelial cells expressed both EGF mRNA (4.7 kb) and EGF receptor mRNAs (10.5, 6.6, and 2.7 kb) These results suggest that the proliferation of uterine epithelial cells is regulated by the paracrine and/or autocrine action of EGF. Our previous study demonstrated the mitogenic effect of IGF-I on uterine epithelial cells. To examine whether the EGF- and IGF-I signaling act at the same level in the regulation of the proliferation of uterine epithelial cells, the cultured cells were simultaneously treated with IGF-I and EGF. IGF-I was found to additively stimulate the mitogenic effects of EGF, suggesting that the EGF-induced growth of uterine epithelial cells is distinct from IGF-I-induced growth. 相似文献
104.
Hashimoto R Katoh Y Nakamura K Itoh S Iesaki T Daida H Nakazato Y Okada T 《Biochemical and biophysical research communications》2012,423(4):672-678
The bone marrow stroma contains osteoblasts and adipocytes that have a common precursor: the pluripotent mesenchymal stem cell found in bone marrow stromal cells (BMSCs). Local bone marrow Ca(2+) levels can reach high concentrations due to bone resorption, which is one of the notable features of the bone marrow stroma. Here, we describe the effects of high [Ca(2+)](o) on the accumulation of adipocytes in the bone marrow stroma. Using primary mouse BMSCs, we evaluated the level of adipocyte accumulation by measuring Oil Red O staining and glycerol-3-phosphate dehydrogenase (GPDH) activity. High [Ca(2+)](o) enhanced the accumulation of adipocytes following treatment with both insulin and dexamethasone together but not in the absence of this treatment. This enhanced accumulation was the result of both the accelerated proliferation of BMSCs and their differentiation into adipocytes. Using the fura-2 method, we also showed that high [Ca(2+)](o) induces an increase in [Ca(2+)](i). An intracellular Ca(2+) chelator suppressed the enhancement in adipocyte accumulation due to increased [Ca(2+)](o) in BMSCs. These data suggest a new role for extracellular Ca(2+) in the bone marrow stroma: increased [Ca(2+)](o) induces an increase in [Ca(2+)](i) levels, which in turn enhances the accumulation of adipocytes under certain conditions. 相似文献
105.
Insulin-like growth factor I enhances gonadotropin-releasing hormone-stimulated luteinizing hormone release from bovine anterior pituitary cells 总被引:3,自引:0,他引:3
The role of insulin-like growth factor I (IGF-I) in the release of luteinizing hormone (LH) is unclear in ruminants. In the present study, the effects of IGF-I on the release of LH stimulated by gonadotropin-releasing hormone (GnRH) were examined in primary cultures of bovine anterior pituitary (AP) cells, and the interaction between estradiol-17beta (E(2)) and IGF-I was characterized. GnRH(100nM)-stimulated LH release from the cultured cells was increased (P<0.05) 12, 24 and 36h after addition of IGF-I (250ng/ml), with a maximum at 12h (48.4ng/ml media versus 35.4ng/ml media in controls). IGF-I at concentrations of 25, 250 and 500ng/ml increased the release by 18.7, 24.2 and 28.9%, respectively (P<0.05), when compared with controls (37.2ng/ml media). E(2) (10nM), IGF-I (250ng/ml) and combined treatment of E(2) plus IGF-I also induced significant increases in LH release (P<0.05). The amounts of LH release after treatment with E(2) alone was 37.3% greater than with IGF-I alone (39.0ng/ml media versus 28.4ng/ml media) (P<0.05). When E(2) and IGF-I were added together (45.6ng/ml media), the release of LH was significantly greater than with either E(2) alone or IGF-I alone (P<0.05). E(2) (10nM) significantly (P<0.05) increased the amount of GnRH bound to the cells by 51.6% when compared with controls, however, IGF-I (250ng/ml) failed to increase GnRH binding. These results show that IGF-I enhances GnRH-stimulated LH release without changing the number of GnRH receptors in cattle, and IGF-I interacts with E(2) to increase the response to GnRH. 相似文献
106.
Naoko Sekino‐Suzuki Kohei Yuyama Toshiaki Miki Mizuho Kaneda Hidenori Suzuki Naomasa Yamamoto Tadashi Yamamoto Chitose Oneyama Masato Okada Kohji Kasahara 《Journal of neurochemistry》2013,124(4):514-522
The association of gangliosides with specific proteins in the central nervous system was examined by coimmunoprecipitation with an anti‐ganglioside antibody. The monoclonal antibody to the ganglioside GD3 (R24) immunoprecipitated the Csk (C‐terminal src kinase)‐binding protein (Cbp). Sucrose density gradient analysis showed that Cbp of rat cerebellum was detected in detergent‐resistant membrane (DRM) raft fractions. R24 treatment of the rat primary cerebellar cultures induced Lyn activation and tyrosine phosphorylation of Cbp. Treatment with anti‐ganglioside GD1b antibody also induced tyrosine phosphorylation. Furthermore, over‐expressions of Lyn and Cbp in Chinese hamster ovary (CHO) cells resulted in tyrosine 314 phosphorylation of Cbp, which indicates that Cbp is a substrate for Lyn. Immunoblotting analysis showed that the active form of Lyn and the Tyr314‐phosphorylated form of Cbp were highly accumulated in the DRM raft fraction prepared from the developing cerebellum compared with the DRM raft fraction of the adult one. In addition, Lyn and the Tyr314‐phosphorylated Cbp were highly concentrated in the growth cone fraction prepared from the developing cerebellum. Immunoelectron microscopy showed that Cbp and GAP‐43, a growth cone marker, are localized in the same vesicles of the growth cone fraction. These results suggest that Cbp functionally associates with gangliosides on growth cone rafts in developing cerebella. 相似文献
107.
Reiko Suzuki Naoko Ito Yuki Uno Ichiro Nishii Satoshi Kagiwada Sigeru Okada Tetsuko Noguchi 《PloS one》2013,8(12)
The colonial microalga Botryococcus braunii accumulates large quantities of hydrocarbons mainly in the extracellular space; most other oleaginous microalgae store lipids in the cytoplasm. Botryococcus braunii is classified into three principal races (A, B, and L) based on the types of hydrocarbons. Race B has attracted the most attention as an alternative to petroleum by its higher hydrocarbon contents than the other races and its hydrocarbon components, botryococcenes and methylsqualenes, both can be readily converted into biofuels. We studied race B using fluorescence and electron microscopy, and clarify the stage when extracellular hydrocarbon accumulation occurs during the cell cycle, in a correlation with the behavior and structural changes of the lipid bodies and discussed development of the algal colony. New accumulation of lipids on the cell surface occurred after cell division in the basolateral region of daughter cells. While lipid bodies were observed throughout the cell cycle, their size and inclusions were dynamically changing. When cells began dividing, the lipid bodies increased in size and inclusions until the extracellular accumulation of lipids started. Most of the lipids disappeared from the cytoplasm concomitant with the extracellular accumulation, and then reformed. We therefore hypothesize that lipid bodies produced during the growth of B. braunii are related to lipid secretion. New lipids secreted at the cell surface formed layers of oil droplets, to a maximum depth of six layers, and fused to form flattened, continuous sheets. The sheets that combined a pair of daughter cells remained during successive cellular divisions and the colony increased in size with increasing number of cells. 相似文献
108.
Ryo Yoshizawa Nobuhisa Umeki Akihiro Yamamoto Mariko Okada Masayuki Murata Yasushi Sako 《Molecular biology of the cell》2021,32(19):1838
p52SHC (SHC) and GRB2 are adaptor proteins involved in the RAS/MAPK (ERK) pathway mediating signals from cell-surface receptors to various cytoplasmic proteins. To further examine their roles in signal transduction, we studied the translocation of fluorescently labeled SHC and GRB2 to the cell surface, caused by the activation of ERBB receptors by heregulin (HRG). We simultaneously evaluated activated ERK translocation to the nucleus. Unexpectedly, the translocation dynamics of SHC were sustained when those of GRB2 were transient. The sustained localization of SHC positively correlated with the sustained nuclear localization of ERK, which became more transient after SHC knockdown. SHC-mediated PI3K activation was required to maintain the sustainability of the ERK translocation regulating MEK but not RAF. In cells overexpressing ERBB1, SHC translocation became transient, and the HRG-induced cell fate shifted from a differentiation to a proliferation bias. Our results indicate that SHC and GRB2 functions are not redundant but that SHC plays the critical role in the temporal regulation of ERK activation. 相似文献
109.
The chilling injury induced by high root temperature in the leaves of rice seedlings 总被引:2,自引:0,他引:2
Root temperature is found to be a very important factor forleaves to alter the response and susceptibility to chillingstress. Severe visible damage was observed in the most activeleaves of seedlings of a japonica rice (Oryza sativa cv. Akitakomachi),e.g. the third leaf at the third-leaf stage, after the treatmentwhere only leaves but not roots were chilled (L/H). On the otherhand, no visible damage was observed after the treatment whereboth leaves and roots were chilled simultaneously (L/L). Thechilling injury induced by L/H, a novel type of chilling injury,required the light either during or after the chilling in orderto develop the visible symptoms such as leaf bleaching and tissuenecrosis. Chlorophyll fluorescence parameters measured aftervarious lengths of chilling treatments showed that significantchanges were induced before the visible injury. The effectivequantum yield and photochemical quenching of PSII dropped dramaticallywithin 24 h in both the presence and absence of a 12 h lightperiod. The maximal quantum yield and non-photochemical quenchingof PSII decreased significantly only in the presence of light.On the other hand, L/H chilling did not affect the functionof PSI, but caused a significant decrease in the electron availabilityfor PSI. These results suggest that the leaf chilling with highroot temperature destroys some component between PSII and PSIwithout the aid of light, which causes the over-reduction ofPSII in the light, and thereby the visible injury is inducedonly in the light. 相似文献
110.
Keiichi Okada Takami Satomura Akihiko Kinoshita Takao Horikoshi Koh Yasue Masaki Fukuda Akiyoshi Yamada 《Mycoscience》2011,52(1):59-64
In this study, two plots in a secondary and another two in planted Pinus densiflora stands were exposed to different forest treatments, and the ectomycorrhizal (EM) biomass and its ergosterol content was measured
for a year. The unmanaged plot in the secondary stand had greater EM biomass than those in any other plots. Whereas understory
cutting had less effect on EM biomass, litter and humus removal decreased pine EM biomass and its ergosterol content, suggesting
that such forest treatment alters EM biomass and its structure. 相似文献