全文获取类型
收费全文 | 7504篇 |
免费 | 439篇 |
国内免费 | 3篇 |
出版年
2023年 | 19篇 |
2022年 | 63篇 |
2021年 | 104篇 |
2020年 | 54篇 |
2019年 | 88篇 |
2018年 | 99篇 |
2017年 | 110篇 |
2016年 | 146篇 |
2015年 | 254篇 |
2014年 | 295篇 |
2013年 | 491篇 |
2012年 | 472篇 |
2011年 | 481篇 |
2010年 | 351篇 |
2009年 | 306篇 |
2008年 | 521篇 |
2007年 | 499篇 |
2006年 | 508篇 |
2005年 | 486篇 |
2004年 | 487篇 |
2003年 | 465篇 |
2002年 | 457篇 |
2001年 | 66篇 |
2000年 | 58篇 |
1999年 | 103篇 |
1998年 | 103篇 |
1997年 | 80篇 |
1996年 | 75篇 |
1995年 | 61篇 |
1994年 | 76篇 |
1993年 | 63篇 |
1992年 | 51篇 |
1991年 | 42篇 |
1990年 | 25篇 |
1989年 | 27篇 |
1988年 | 37篇 |
1987年 | 26篇 |
1986年 | 28篇 |
1985年 | 21篇 |
1984年 | 31篇 |
1983年 | 15篇 |
1982年 | 29篇 |
1981年 | 28篇 |
1980年 | 16篇 |
1979年 | 25篇 |
1978年 | 11篇 |
1977年 | 20篇 |
1976年 | 12篇 |
1975年 | 8篇 |
1967年 | 9篇 |
排序方式: 共有7946条查询结果,搜索用时 31 毫秒
71.
Kato Tomohiko; Shirano Yumiko; Iwamoto Hiroyuki; Shibata Daisuke 《Plant & cell physiology》1993,34(7):1063-1072
A lipoxygenase L-4 gene was isolated from a soybean genomiclibrary. The amino acid sequence of lipoxygenase L-4 is highlyhomologous with the partial amino acid sequence of the 94-kDavegetative storage protein, vsp94, found in paraveinal mesophyllcells in the leaves of depodded soybean plants. No L-4 expressionwas observed in maturing seeds. The L-4 gene is highly expressedin the vegetative tissues of young seedlings, including cotyledons,hypocotyls, roots and primary leaves. L-4 expression followedthe same pattern as lipoxygenase activity in cotyledons peaking3 to 5 days after germination, and returning to a basal levelby 9 days after germination. L-4 gene expression was low inthe roots, stems and leaves of 10-week-old plants. Exposureof 4-week-old plants to atmospheric methyl jasmonate increasedL-4 mRNA in leaves. Continuous pod removal from 7-week-old plantsover a 2 week period resulted in dramatic accumulation of L-4mRNA in leaves. Accumulation of the L-4 protein and three otherlipoxygenase fractions in the leaves of depodded plants wasdemonstrated by ion exchange chromatography. These results indicatethat lipoxygenase L-4 is a component of vsp94. (Received May 31, 1993; Accepted August 9, 1993) 相似文献
72.
Tsutomu Araki Hiroyuki Kato Yasuo Kanai Kyuya Kogure 《Neurochemistry international》1993,23(6):541-548
Age-related alterations in major neurotransmitter receptors and voltage dependent calcium channels were analyzed by receptor autoradiography in the gerbil brain. [3H]Quinuclidinyl benzilate (QNB). [3H]cyclohexyladenosine (CHA), [3H]muscimol, [3H]MK-801, [3H]SCH 23390, [3H]naloxone, and [3H]PN200-110 were used to label muscarinic acetylcholine receptors, adenosine A1 receptors, γ-aminobutyric acidA (GABAA) receptors,
(NMDA) receptors, dopamine D1 receptors, opioid receptors, and voltage dependent calcium channels, respectively. In middle-aged gerbils (16 months old), the hippocampus exhibited a significant elevation in [3H]QNB, [3H]MK-801, [3H]SCH 23390, [3H]naloxone, and [3H]PN200-110 binding, whereas [3H]CHA and [3H]muscimol binding showed a significant reduction in this area, compared with that of young animals (1 month). On the other hand, the cerebellum showed a significant alteration in [3H]QNB, [3H]CHA, and [3H]naloxone binding and the striatum also exhibited a significant alteration in [3H]SCH 23390 and [3H]CHA binding in middle-aged gerbils. The neocortex showed a significant elevation only in [3H]CHA binding in middle-aged animals. The nucleus accumbens and thalamus also showed a significant alteration only in [3H]muscimol binding. However, the hypothalamus and substantia nigra exhibited no significant alteration in these bindings in middle-aged gerbils. These results demonstrate the age-related alterations of various neurotransmitter receptors and voltage dependent calcium channels in most brain regions. Furthermore, they suggest that the hippocampus is most susceptible to aging processes and is altered at an early stage of senescence. 相似文献
73.
Hydrogen peroxide formed during the course of the copper(II)-catalysed oxidation of cysteamine with oxygen was continuously determined by a peroxidase (POD)-catalysed luminol chemiluminescence (CL) method. Horseradish peroxidase (HRP), lactoperoxidase (LPO) and Arthromyces ramosus peroxidase (ARP) were used as a CL catalyst. The respective PODs gave specific CL intensity-time profiles. HRP caused a CL delay, and ARP gave a time-response curve which followed the production rate of H2O2. LPO gave only a weak CL flash which decayed promptly. These differences of CL response curves could be explained in terms of the different reactivities of PODs for superoxide anion and the different formation rate of luminol radicals in the peroxidation of luminol catalysed by POD. 相似文献
74.
Cell Sorting and Chondrogenic Aggregate Formation in Limb Bud Recombinants and in Culture 总被引:1,自引:1,他引:0
The cartilage pattern of the developing chick limb changes along the proximal-distal (PD) axis. It is assumed that these spatial changes are brought about by differences in the cellular properties of distal mesoderm, the progress zone (PZ). To examine whether these differences are actually maintained in the individual cells composing the PZ, we dissociated early (stage 20) and late (stage 25) PZ tissues into single cells, then mixed and recombined them with ectodermal jackets. The recombinants were grafted to limb bud stumps and allowed to develop into limb-like structures. Early PZ cells were distributed within whole cartilage elements along the PD axis of the limb-like structures, while cells from late PZ participated only in the formation of distal cartilage elements.
A difference in distribution pattern between the cells of early and late PZ in mixed culture was also observed. Cells of early PZ aggregated rapidly in patches and formed cartilage nodules, while the cells of late PZ distributed in regions surrounding these cell aggregates and gradually differentiated to cartilage cells. These results suggest that the cellular properties in the PZ concerning the rate of chondrogenic aggregate formation change during limb bud development, and that this change may relate to the cartilage pattern formation along the PD axis. 相似文献
A difference in distribution pattern between the cells of early and late PZ in mixed culture was also observed. Cells of early PZ aggregated rapidly in patches and formed cartilage nodules, while the cells of late PZ distributed in regions surrounding these cell aggregates and gradually differentiated to cartilage cells. These results suggest that the cellular properties in the PZ concerning the rate of chondrogenic aggregate formation change during limb bud development, and that this change may relate to the cartilage pattern formation along the PD axis. 相似文献
75.
Ken-ichiro Takamiya Yuzo Shioi Masakazu Morita Hiroyuki Arata Minoru Shimizu Michio Doi 《Archives of microbiology》1993,159(1):51-56
Characteristics and occurrence of cytochrome c-552 from an aerobic photosynthetic bacterium, Roseobacter denitrificans, were described.Relative molecular mass of the cytrochrome was 13.5 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and 15,000 by gel filtration. This cytochrome was a acidic protein having a pI of 5.6 and Em was +215 mV at pH 7.0. Absorption peaks were at 278, 408 and 524 nm in the oxidized form and 416, 523 and 552 nm in the reduced form.Amino acid composition and N-terminal amino acid sequence of cytochrome c-552 determined for 24 residues had low similarities to those of cytochrome c-551 of this bacterium, which is homologous to cytochrome c
2, although the physico-chemical properties of these two cytochromes were similar to each other.Cytochrome c-552 was maximally synthesized in the light under aerobic conditions but not in the dark. The synthesis also occurred in the presence of alternative acceptors such as trimethylamine N-oxide (TMAO) and nitrate under anaerobic conditions. Our results suggest that cytochrome c-552 is involved in TMAO respiration and denitrification in R. denitrificans, although the effect of light remains to be solved.Abbreviations Em
Midpoint redox potential
- PAGE
Polyacrylamide ge electrophoresis
- SDS-PAGE
Sodium dodecyl sulfate polyacrylamide gel electrophoresis
- TMAO
Trimethylamine N-oxide 相似文献
76.
Seiji Ichida Tetsuyuki Wada Satori Nakazaki Naruhisa Matsuda Hiroyuki Kishino Takafumi Akimoto 《Neurochemical research》1993,18(5):633-638
The characteristics of the specific bindings of [3H](+)PN200-110 (PN: L-type Ca channel antagonist) and [125I]-conotoxin G VI A (-CgTX: neuronal L-or N-type Ca channel antagonist) to crude membranes from undifferentiated neuroblastoma x glioma hybrid NG108-15 (NG108-15) cells and differentiated cells induced with dibutyryl cAMP (Bt2cAMP) were examined, because we have already observed that the magnitude and rate of KCL-stimulated45Ca uptake by NG108-15 cells increased progressively during differentiation of the cells induced with Bt2cAMP (unpublished results). The specific binding of [3H](+)PN to these crude membranes was saturable at various concentrations of 2.5–5.0 nM [3H](+)PN. Scatchard analysis showed that the specific binding of [3H](+)PN at equilibrium was significantly increased after differentiation of the NG108-15 cells with Bt2cAMP, but that the apparent Kd value for the specific binding of [3H](+)PN was not influenced by treatment with Bt2cAMP. The specific binding of [3H](+)PN to crude membranes from Bt2cAMP-treated NG108-15 cells was inhibited by a calcium agonist and antagonists, the order of their inhibitory potencies being (+)PN>nitrendipine>(–)PNBay K 8644diltiazem = verapamil. Thus, PNs showed significant stereoselective inhibition of the specific binding of [3H(+)PN. On the other hand, [125I]-CgTX at concentrations of 0.075–0.6 nM showed scarcely any specific binding to these crude membranes, although at 0.6 nM it showed specific binding to crude membranes from rat brain in the same experimental conditions. These results suggest that the increase in magnitude or rate of KCl-stimulated45Ca uptake during differentiation of NG108-15 cells is partially due to quantitative alteration of voltage-sensitive Ca channels in the cells, and that there are scarcely any specific binding sites for [125I]-CgTX on Bt2cAMP-treated or untreated NG108-15 cells. 相似文献
77.
Seiji Ichida Tetsuyuki Wada Masahiro Sekiguchi Hiroyuki Kishino Yuko Okazaki Takafumi Akimoto 《Neurochemical research》1993,18(11):1137-1144
Characteristics of specific125I-omega-conotoxin (-CgTX) binding were systematically investigated in crude membranes from rat whole brain. Kd and Bmax Values for the binding were 49.7 pM and 181.5 fmol/mg of protein, respectively. The effects of various types of Ca channel antagonists on the binding were investigated. Dynorphin A (1–13), in particular, specifically inhibited125I--CgTX binding, but not that of [3H](+)PN200-110. Spider venom fromPlectreurys tristes did not specifically inhibit specific binding of125I--CgTX, because the venom also inhibited the binding of [3H](+)PN200-110 to a similar degree. The amount of specific binding of125I--CgTX was less in the cerebellum than that in any other area of whole brain. The cross-linker disuccinimidyl suberate did not label with125I--CgTX and its binding sites in rat whole brain, although it did in chick whole brain, which was used as a positive control. These findings suggested that dynorphine A (1–13) was a selective blocker of -CgTX-sensitive Ca channels in crude membranes from rat whole brain and that -CgTX-sensitive Ca channels were mainly present a rat brain except cerebellum. 相似文献
78.
Toshiyuki Takahashi Hiroshi Ishikura Kazuhiro Iwai Chisa Takahashi Hiroyuki Kato Tatsuzo Tanabe Takashi Yoshiki 《Cancer immunology, immunotherapy : CII》1993,36(2):76-82
The permanent pancreas carcinoma cell line, PCI-24, was developed in order to analyse cytokine regulation on pancreas carcinoma and lymphokine-activated killer (LAK) cell interaction. PCI cells expressed ICAM-1 and HLA-ABC, but not HLA-DR antigens. PCI cells showed augmented ICAM-1 and HLA-ABC expression when incubated with interferon (IFN) and tumour necrosis factor . A similar but weak augmentary effect on the HLA-ABC and ICAM-1 surface expression was seen with interleukin-1 treatment. Natural attachment of LAK to PCI cells was augmented by recombinant IFN in close association with ICAM-1 up-regulation on PCI cells. In addition, natural attachment was significantly inhibited by anti-LFA-1 and anti-ICAM-1 antibody treatments. Cytotoxicity of the LAK cells against PCI cells was also significantly inhibited with the same treatment. Thus, the attachment of LAK cells to PCI cells through LFA-1/ICAM-1 molecules appeared to be essential for the cytotoxicity for PCI cells. Pretreatment of PCI cells, but not of LAK cells, with IFN or other cytokines resulted in a decrease of susceptibility for LAK cell cytotoxicity. The decreased susceptibility inversely correlated with HLA-ABC expression on the PCI cells. The collective evidence indicates that, although LAK cell attachment to pancreas carcinoma cells through the LFA-1/ICAM-1 molecule is augmented by IFN, IFN treatment of pancreas carcinoma cells reduces LAK cell cytotoxicity possibly through an increase in HLA-ABC or a regulation of molecules closely associated to HLA-ABC expression. 相似文献
79.
Hiroyuki Suzuki Shozo Fujioka Suguru Takatsuto Takao Yokota Noboru Murofushi Akira Sakurai 《Journal of Plant Growth Regulation》1993,12(2):101-106
Feeding experiments with tritium- and deuterium-labeled castasterone (CS) were conducted with three cell lines of Catharanthus roseus, including crown gall cells and nontransformed cells. In all three cell lines, the conversion of CS to brassinolide (BL) was observed and unequivocally confirmed by gas chromatography/mass spectrometry (GC/MS). This is the first conclusive evidence that CS is the biosynthetic precursor of BL.Biosynthesis of brassinosteroids in Catharanthus roseus. Part II. Part I of this series: Yokota et al. (1990a). 相似文献
80.
Takenobu Ishii Montserrat Ruiz-Torruella Jae Young Kim Hiroyuki Kanzaki Abdullah Albassam Wichaya Wisitrasameewong Satoru Shindo Roodelyne Pierrelus Alireza Heidari Umadevi Kandalam Shin Nakamura Alexandru Movila Dmitriy Minond Toshihisa Kawai 《Journal of cellular and molecular medicine》2023,27(12):1750-1756
Bone remodelling is mediated by orchestrated communication between osteoclasts and osteoblasts which, in part, is regulated by coupling and anti-coupling factors. Amongst formally known anti-coupling factors, Semaphorin 4D (Sema4D), produced by osteoclasts, plays a key role in downmodulating osteoblastogenesis. Sema4D is produced in both membrane-bound and soluble forms; however, the mechanism responsible for producing sSema4D from osteoclasts is unknown. Sema4D, TACE and MT1-MMP are all expressed on the surface of RANKL-primed osteoclast precursors. However, only Sema4D and TACE were colocalized, not Sema4D and MT1-MMP. When TACE and MT1-MMP were either chemically inhibited or suppressed by siRNA, TACE was found to be more engaged in shedding Sema4D. Anti-TACE-mAb inhibited sSema4D release from osteoclast precursors by ~90%. Supernatant collected from osteoclast precursors (OC-sup) suppressed osteoblastogenesis from MC3T3-E1 cells, as measured by alkaline phosphatase activity, but OC-sup harvested from the osteoclast precursors treated with anti-TACE-mAb restored osteoblastogenesis activity in a manner that compensates for diminished sSema4D. Finally, systemic administration of anti-TACE-mAb downregulated the generation of sSema4D in the mouse model of critical-sized bone defect, whereas local injection of recombinant sSema4D to anti-TACE-mAb-treated defect upregulated local osteoblastogenesis. Therefore, a novel pathway is proposed whereby TACE-mediated shedding of Sema4D expressed on the osteoclast precursors generates functionally active sSema4D to suppress osteoblastogenesis. 相似文献