全文获取类型
收费全文 | 3308篇 |
免费 | 194篇 |
出版年
2022年 | 21篇 |
2021年 | 40篇 |
2020年 | 26篇 |
2019年 | 35篇 |
2018年 | 40篇 |
2017年 | 45篇 |
2016年 | 79篇 |
2015年 | 105篇 |
2014年 | 142篇 |
2013年 | 223篇 |
2012年 | 213篇 |
2011年 | 205篇 |
2010年 | 111篇 |
2009年 | 87篇 |
2008年 | 201篇 |
2007年 | 156篇 |
2006年 | 166篇 |
2005年 | 156篇 |
2004年 | 159篇 |
2003年 | 140篇 |
2002年 | 118篇 |
2001年 | 97篇 |
2000年 | 95篇 |
1999年 | 93篇 |
1998年 | 37篇 |
1997年 | 18篇 |
1996年 | 16篇 |
1995年 | 24篇 |
1994年 | 25篇 |
1993年 | 21篇 |
1992年 | 48篇 |
1991年 | 45篇 |
1990年 | 45篇 |
1989年 | 53篇 |
1988年 | 48篇 |
1987年 | 44篇 |
1986年 | 43篇 |
1985年 | 38篇 |
1984年 | 29篇 |
1983年 | 11篇 |
1982年 | 29篇 |
1981年 | 13篇 |
1979年 | 17篇 |
1978年 | 19篇 |
1977年 | 12篇 |
1976年 | 8篇 |
1974年 | 13篇 |
1973年 | 12篇 |
1972年 | 9篇 |
1969年 | 16篇 |
排序方式: 共有3502条查询结果,搜索用时 15 毫秒
61.
To study the mechanism of action of diflubenzuron (DFB) and other benzoylphenylureas, we have initially hypothesized that their action may be related to exocytosis: to test the hypothesis, we obtained an intracellular vesicle preparation from the homogenate of integument of newly molted American cockroachs (Periplaneta americana L.) in 10 mM MES buffer containing 250 mM sucrose (isotonic) and 2.5 mM MgSO4, at pH 6.6. By studying DFB's effect on various ion transporting activities, we demonstrated that calcium uptake in this intracellular particulate preparation was significantly inhibited by DFB at low concentrations (e.g., 10−8 M). Such an inhibitory effect of DFB on Ca2+ uptake was eliminated by the addition of ionophores or membrane disruptors, as well as the sonication of vesicle preparation. On the other hand, oligomycin, protein phosphorylation modulators, Na+, and Li+ did not affect the calcium uptake. Among ionophores, agents disrupting H+ gradients (e.g. FCCP and NEM) totally eliminated 45Ca uptaking activity by vesicles as well as the inhibitory effect of DFB. Among calcium ion modulators, calmodulin inhibitors such as calmidazolium and trifluoperazine decreased the Ca2+-uptake, whereas membrane calcium channel blocker, verapamil, did not. ATP and γ-S-GTP stimulated Ca2+ uptake. However, the former increased only the DFB insensitive portion and the latter largely the DFB sensitive part of Ca2+. Together these data support the hypothesis that the action site of DFB in this preparation is the GTP-dependent Ca2+ transport process which is coupled to vacuolar type intracellular vesicles in the integument cells. 相似文献
62.
Zhao Ying Hiromasa Tojo Takanori Komatsubara Manabu Nakagawa Masami Inada Sumio Kawata Yuji Matsuzawa Mitsuhiro Okamoto 《生物化学与生物物理学报:疾病的分子基础》1994,1226(2):201-205
Enzyme activity, protein contents, and mRNA contents of group II phospholipase A2 (PLA2) in hepatocellular carcinoma (HCC) surgically obtained from 8 patients were compared with those in either its neighboring liver tissues or control liver tissues. The PLA2 specific activity towards the mixed micelles of 1-palmitoyl-2-oleoyl-phosphatidylglycerol and cholate was significantly greater in the tumor tissues (6.62 ± 1.46 nmol/min/mg) than those in the surrounding liver tissues (1.33 ± 0.22 nmol/min/mg) and controls (0.43 ± 0.04 nmol/min/mg). The results of immunoblot analysis using a specific anti-human group II PLA2 antibody and of Northern blot analysis using a human group II PLA2 cDNA as a probe demonstrated that group II PLA2 was responsible for the increased enzyme activity. The contents of immunoreactive group II PLA2 in the tumor tissues (8.81 ± 1.24 ng/mg) were significantly higher than those in the surrounding liver tissues (1.77 ± 0.27 ng/mg); those in the control tissues were below the analytical range of the method used. The group II PLA2 mRNA was also significantly increased in the tumor tissues, compared with that in the surrounding liver tissues, whereas it was not detectable in th controls. This indicates that group II PLA2 in HCC is induced at the pretranslational level. 相似文献
63.
Kumiko Ui Shoko Nishihara M. Sakuma S. Togashi R. Ueda Y. Miyata T. Miyake 《In vitro cellular & developmental biology. Animal》1994,30(4):209-216
Summary From the central nervous system ofDrosophila melanogaster 3rd instar larvae, eight continuous cell lines have been established (named ML-DmBG1 to 8). Using ML-DmBG2, single colony
isolation was carried out and six colonial clones were obtained. All reacted to the antibody to horseradish peroxidase, which
is a neuronal marker in insects. Acetylcholine, a known neurotransmitter inDrosophila, was detected in three of the colonial clones by high performance liquid chromatography. Therefore, it is concluded that
the established colonial clones are neural cells originating in the larval central nervous system. Among them, some variation
was observed with respect to morphology, acetylcholine content, and reactivity to anti-HRP. The variation may reflect the
heterogeneity of cells composing the central nervous system. 相似文献
64.
Nitric Oxide Reversibly Suppresses Xanthine Oxidase Activity 总被引:10,自引:0,他引:10
Masami Fukahori Kohji Ichimori Hideyuki Ishida Hiroe Nakagawa Haruka Okino 《Free radical research》1994,21(4):203-212
The effects of nitric oxide (NO) on xanthine oxidase (XOD) activity and the site(s) of the redox center(s) affected were investigated. XOD activity was determined by superoxide (O2-) generation and uric acid formation. NO reversibly and dose-dependently suppressed XOD activity in both determination methods. The suppression interval also disclosed a dose-dependent prolongation. The suppression occurred irrespective of the presence or absence of xanthine; indicating that the reaction product of NO and O2-, peroxynitrite, is not responsible for the suppression. Application of synthesized peroxynitrite did not affect XOD activity up to 2 μM. Methylene blue, which is an electron acceptor from Fe/S center, prevented the NO-induced inactivation. The results indicate that NO suppresses XOD activity through reversible alteration of the flavin prosthetic site. 相似文献
65.
Mouse mammary tumor virus with rearranged long terminal repeats causes murine lymphomas. 总被引:5,自引:3,他引:2
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
S Yanagawa K Kakimi H Tanaka A Murakami Y Nakagawa Y Kubo Y Yamada H Hiai K Kuribayashi T Masuda et al. 《Journal of virology》1993,67(1):112-118
Mouse mammary tumor virus (MMTV) is a slowly transforming retrovirus associated primarily with the induction of mammary tumors. It is widely accepted that T-cell lymphomas of various mouse strains are associated with extra proviruses of MMTV. These extra proviruses showed site-specific rearrangements in the U3 region of long terminal repeats (LTRs), consisting of about 400 nucleotide deletions and occasional substitution resulting in unique tandem repeats. However, the question of whether these mutant MMTVs cause lymphomas has not been experimentally resolved. Here we present distinct evidence that they do. We constructed chimeric MMTVs by replacing the LTR of the recently constructed pathogenic MMTV provirus clone with rearranged LTRs of MMTV proviruses obtained from two DBA/2 mouse lymphoma cell lines, MLA and DL-8, and inoculated them into BALB/c mice. These mice developed lymphomas, but no mammary tumors, 4 to 11 months postinoculation, whereas the original pathogenic MMTV clone alone induced mammary tumors. These results showed that the tissue specificity of MMTV tumorigenesis is determined by the LTR structures. 相似文献
66.
Enhanced production of rat interleukin-8 by in vitro and in vivo infections with influenza A NWS virus. 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We investigated the interleukin-8 (IL-8)-producing activity of influenza A NWS virus in cultured rat kidney NRK-52E cells and a rat influenza model. The production of rat IL-8 increased significantly in the virus-infected cells but not in UV-inactivated virus- or split-product-treated cells. The increase in IL-8 production could be detected in the bronchoalveolar lavage of infected rats. These data suggest that infectious virus has the potential to accelerate the production of IL-8 in cultured cells and in vivo in airway-lining cells. 相似文献
67.
68.
69.
Ota Yoko; Ario Takeshi; Hayashi Koji; Nakagawa Tsuyoshi; Hattori Tsukaho; Maeshima Masayoshi; Asahi Tadashi 《Plant & cell physiology》1992,33(3):225-232
Catalases purified from endosperm glyoxysomes and non-specializedmicrobodies from hypocotyls of castor bean seedlings differedin their specific activity [90164 and 0.894.9kunits (mg protein)1, respectively] and in their constituentsubunits [two subunits of 54 and 56 kDa for the endosperm enzymeand only one of 56 kDa for the hypocotyl enzyme]. Immunoblotanalysis also showed that particulate fractions from the endospermsand from etiolated and green cotyledons contained two catalasesubunits of 54 and 56 kDa, whereas such fractions from the hypocotylsand roots contained only the 56-kDa subunit. Leaf peroxisomesfrom green leaves had two catalase subunits of around 55 kDaeach. Results of translation in vitro indicated that the 54-and 56-kDa subunits were translated from distinct mRNAs andlevels of both mRNAs increased in the endosperms during germination,prior to increases in levels of catalase proteins. In the hypocotyls,the 56-kDa subunit seemed to be synthesized constitutively.
1Present addresses: YO, Toyota Central Institute, 31-9 Musashizuka,Nagabuchi, Nagakute, Aichi 480-11, Japan 相似文献
70.
Yoshihiro Kuroda Yoshitaka Maeda Shinichi Sawa Kiyohiro Shibata Kazuhide Miyamoto Terumichi Nakagawa 《Journal of peptide science》2003,9(4):212-220
Pathogenic prion proteins (PrP(Sc)) are thought to be produced by alpha-helical to beta-sheet conformational changes in the normal cellular prion proteins (PrP(C)) located solely in the caveolar compartments. In order to inquire into the possible conformational changes due to the influences of hydrophobic environments within caveolae, the secondary structures of prion protein peptides were studied in various kinds of detergents by CD spectra. The peptides studied were PrP(129-154) and PrP(192-213); the former is supposed to assume beta-sheets and the latter alpha-helices, in PrP(Sc). The secondary structure analyses for the CD spectra revealed that in buffer solutions, both PrP(129-154) and PrP(192-213) mainly adopted random-coils (approximately 60%), followed by beta-sheets (30%-40%). PrP(129-154) showed no changes in the secondary structures even in various kinds of detergents such as octyl-beta-D-glucopyranoside (OG), octy-beta-D-maltopyranoside (OM). sodium dodecyl sulfate (SDS), Zwittergent 3-14 (ZW) and dodecylphosphocholine (DPC). In contrast, PrP(192-213) changed its secondary structure depending on the concentration of the detergents. SDS, ZW, OG and OM increased the alpha-helical content, and decreased the beta-sheet and random-coil contents. DPC also increased the alpha-helical content, but to a lesser extent than did SDS, ZW, OG or OM. These results indicate that PrP(129-154) has a propensity to adopt predominantly beta-sheets. On the other hand, PrP(192-213) has a rather fickle propensity and varies its secondary structure depending on the environmental conditions. It is considered that the hydrophobic environments provided by these detergents may mimic those provided by gangliosides in caveolae, the head groups of which consist of oligosaccharide chains containing sialic acids. It is concluded that PrP(C) could be converted into a nascent PrP(Sc) having a transient PrP(Sc) like structureunder the hydrophobic environments produced by gangliosides. 相似文献