全文获取类型
收费全文 | 615篇 |
免费 | 46篇 |
专业分类
661篇 |
出版年
2022年 | 3篇 |
2021年 | 5篇 |
2020年 | 6篇 |
2019年 | 2篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 12篇 |
2015年 | 14篇 |
2014年 | 23篇 |
2013年 | 28篇 |
2012年 | 38篇 |
2011年 | 35篇 |
2010年 | 26篇 |
2009年 | 22篇 |
2008年 | 41篇 |
2007年 | 24篇 |
2006年 | 44篇 |
2005年 | 50篇 |
2004年 | 51篇 |
2003年 | 50篇 |
2002年 | 43篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1997年 | 10篇 |
1996年 | 5篇 |
1995年 | 12篇 |
1994年 | 13篇 |
1993年 | 7篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 7篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1971年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有661条查询结果,搜索用时 15 毫秒
41.
Furuno-Fukushi I Masumura K Furuse T Noda Y Takahagi M Saito T Hoki Y Suzuki H Wynshaw-Boris A Nohmi T Tatsumi K 《Radiation research》2003,160(5):549-558
Deletion mutations were efficiently recovered in mouse liver after total-body irradiation with X rays by using a transgenic mouse "gpt-delta" system that harbored a lambda EG10 shuttle vector with the red and gam genes for Spi- (sensitive to P2 lysogen interference) selection. We incorporated this system into homozygous Atm-knockout mice as a model of the radiosensitive hereditary disease ataxia telangiectasia (AT). Lambda phages recovered from the livers of X-irradiated mice with the Atm+/+ genotype showed a dose-dependent increase in the Spi- mutant frequency up to sixfold at 50 Gy over the unirradiated control of 2.8x10(-6). The livers from Atm-/- mice yielded a virtually identical dose-response curve for X rays with a background fraction of 2.4x10(-6). Structural analyses revealed no significant difference in the proportion of -1 frameshifts and larger deletions between Atm+/+ and Atm-/- mice, although larger deletions prevailed in X-ray-induced Spi- mutants irrespective of Atm status. While a possible defect in DNA repair after irradiation has been strongly indicated in the literature for nondividing cultured cells in vitro from AT patients, the Atm disruption does not significantly affect radiation mutagenesis in the stationary mouse liver in vivo. 相似文献
42.
The dissociation constant (Kd) for CO from neuronal nitric oxide synthase heme in the absence of the substrate and cofactor was less than 10−3 μM. In the presence of
-Arg, it dramatically increased up to 1 μM. In the presence of inhibitors such as NG-nitro-
-arginine methyl ester and 7-nitroindazole (NI), the Kd value further increased up to more than 100 μM. Addition of the cofactor, 5,6,7,8-tetrahydrobiopterin (H4B), increased the Kd value by 10-fold in the presence of
-Arg, whereas it decreased the value to less than one 250th in the presence of NI. Addition of H4B increased the recombination rate constant (kon) for CO by more than two-fold in the presence of
-Arg or N6-(1-iminoethyl)-
-lysine, whereas it decreased the kon value by three-fold in the presence of
-thiocitrulline. Thus, the binding fashion of some of inhibitors, such as NI, may be different from that of
-Arg with respect to the H4B effect. 相似文献
Full-size image
Full-size image
Full-size image
Full-size image
Full-size image
Full-size image
Full-size image
43.
Tanaka A Iwase H Hiki Y Kokubo T Ishii-Karakasa I Toma K Kobayashi Y Hotta K 《Glycoconjugate journal》1998,15(10):995-1000
Glycopeptides containing the N-linked oligosaccharide from human serum IgA1 were analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOFMS). Two glycopeptides, GP1 and GP2, prepared from the endoproteinase Asp-N digest of the IgA1 heavy chain, were derived from the CH2 domain (N-glycan site at Asn263) and the tailpiece portion (N-glycan site at Asn459), respectively. The structure of the attached sugar chain was deduced from the mass number of the glycopeptide and confirmed by a two-dimensional mapping technique for a pyridylaminated oligosaccharide. GP1 was composed of two major components having a fully galactosylated bianntena sugar chain with or without a bisecting N-acetylglucosamine (GlcNAc) residue. On the other hand, the GP2 fraction corresponded to the glycopeptides having a fully galactosylated and fucosylated bianntena sugar chain partly bearing a bisecting GlcNAc residue. Thus, the site-specific fucosylation of the N-linked oligosaccharide on the tailpiece of the 1 chain became evident for normal human serum IgA1. 相似文献
44.
Aki Isobe Kenjiro Sawada Yasuto Kinose Chifumi Ohyagi-Hara Erika Nakatsuka Hiroshi Makino Tomonori Ogura Tomoko Mizuno Noriko Suzuki Eiichi Morii Koji Nakamura Ikuko Sawada Aska Toda Kae Hashimoto Seiji Mabuchi Tsuyoshi Ohta Ken-ichirou Morishige Hirohisa Kurachi Tadashi Kimura 《PloS one》2015,10(2)
Ovarian cancer remains the most lethal gynecologic cancer and new targeted molecular therapies against this miserable disease continue to be challenging. In this study, we analyzed the expressional patterns of Interleukin-6 (IL-6) and its receptor (IL-6R) expression in ovarian cancer tissues, evaluated the impact of these expressions on clinical outcomes of patients, and found that a high-level of IL-6R expression but not IL-6 expression in cancer cells is an independent prognostic factor. In in vitro analyses using ovarian cell lines, while six (RMUG-S, RMG-1, OVISE, A2780, SKOV3ip1 and OVCAR-3) of seven overexpressed IL-6R compared with a primary normal ovarian surface epithelium, only two (RMG-1, OVISE) of seven cell lines overexpressed IL-6, suggesting that IL-6/IL-6R signaling exerts in a paracrine manner in certain types of ovarian cancer cells. Ovarian cancer ascites were collected from patients, and we found that primary CD11b+CD14+ cells, which were predominantly M2-polarized macrophages, are the major source of IL-6 production in an ovarian cancer microenvironment. When CD11b+CD14+ cells were co-cultured with cancer cells, both the invasion and the proliferation of cancer cells were robustly promoted and these promotions were almost completely inhibited by pretreatment with anti-IL-6R antibody (tocilizumab). The data presented herein suggest a rationale for anti-IL-6/IL-6R therapy to suppress the peritoneal spread of ovarian cancer, and represent evidence of the therapeutic potential of anti-IL-6R therapy for ovarian cancer treatment. 相似文献
45.
Kazuyuki Wakabayashi Kouichi Soga Takayuki Hoson Toshihisa Kotake Takashi Yamazaki Akira Higashibata Noriaki Ishioka Toru Shimazu Keiji Fukui Ikuko Osada Haruo Kasahara Motoshi Kamada 《PloS one》2015,10(9)
Network structures created by hydroxycinnamate cross-links within the cell wall architecture of gramineous plants make the cell wall resistant to the gravitational force of the earth. In this study, the effects of microgravity on the formation of cell wall-bound hydroxycinnamates were examined using etiolated rice shoots simultaneously grown under artificial 1 g and microgravity conditions in the Cell Biology Experiment Facility on the International Space Station. Measurement of the mechanical properties of cell walls showed that shoot cell walls became stiff during the growth period and that microgravity suppressed this stiffening. Amounts of cell wall polysaccharides, cell wall-bound phenolic acids, and lignin in rice shoots increased as the shoot grew. Microgravity did not influence changes in the amounts of cell wall polysaccharides or phenolic acid monomers such as ferulic acid (FA) and p-coumaric acid, but it suppressed increases in diferulic acid (DFA) isomers and lignin. Activities of the enzymes phenylalanine ammonia-lyase (PAL) and cell wall-bound peroxidase (CW-PRX) in shoots also increased as the shoot grew. PAL activity in microgravity-grown shoots was almost comparable to that in artificial 1 g-grown shoots, while CW-PRX activity increased less in microgravity-grown shoots than in artificial 1 g-grown shoots. Furthermore, the increases in expression levels of some class III peroxidase genes were reduced under microgravity conditions. These results suggest that a microgravity environment modifies the expression levels of certain class III peroxidase genes in rice shoots, that the resultant reduction of CW-PRX activity may be involved in suppressing DFA formation and lignin polymerization, and that this suppression may cause a decrease in cross-linkages within the cell wall architecture. The reduction in intra-network structures may contribute to keeping the cell wall loose under microgravity conditions. 相似文献
46.
The nuclear pore complex (NPC) facilitates nucleocytoplasmic transport, a crucial process for various cellular activities. The NPC comprises ~30 nucleoporins and is well characterized in vertebrates and yeast. However, only eight plant nucleoporins have been identified, and little information is available about the complete molecular structure of plant NPCs. In this study, an interactive proteomic approach was used to identify Arabidopsis thaliana nucleoporins. A series of five cycles of interactive proteomic analysis was performed using green fluorescent protein (GFP)-tagged nucleoporins. The identified nucleoporins were then cloned and subcellular localization analyses were performed. We found that the plant NPC contains at least 30 nucleoporins, 22 of which had not been previously annotated. Surprisingly, plant nucleoporins shared a similar domain organization to their vertebrate (human) and yeast (Saccharomyces cerevisiae) counterparts. Moreover, the plant nucleoporins exhibited higher sequence homology to vertebrate nucleoporins than to yeast nucleoporins. Plant NPCs lacked seven components (NUCLEOPORIN358 [Nup358], Nup188, Nup153, Nup45, Nup37, NUCLEAR DIVISION CYCLE1, and PORE MEMBRANE PROTEIN OF 121 kD) that were present in vertebrate NPCs. However, plants possessed a nucleoporin, Nup136/Nup1, that contained Phe-Gly repeats, and sequence analysis failed to identify a vertebrate homolog for this protein. Interestingly, Nup136-GFP showed greater mobility on the nuclear envelope than did other nucleoporins, and a Nup136/Nup1 deficiency caused various defects in plant development. These findings provide valuable new information about plant NPC structure and function. 相似文献
47.
Takashi L. Shimada Tomoo Shimada Ikuko Hara‐Nishimura 《The Plant journal : for cell and molecular biology》2010,61(3):519-528
The creation of transgenic plants has contributed extensively to the advancement of plant science. Establishing homozygous transgenic lines is time‐consuming and laborious, and using antibiotics or herbicides to select transformed plants may adversely affect the growth of some transgenic plants. Here we describe a novel technology, which we have named FAST (fluorescence‐accumulating seed technology), that overcomes these difficulties. Although this technology was designed for use in Arabidopsis thaliana, it may be adapted for use in other plants. The technology is based on the expression of a fluorescent co‐dominant screenable marker FAST, under the control of a seed‐specific promoter, on the oil body membrane. The FAST marker harbors a fusion gene encoding either GFP or RFP with an oil body membrane protein that is prominent in seeds. The marker protein was only expressed in a specific organ (i.e. in dry seeds) and at a specific time (i.e. during dormancy), which are desirable features of selectable and/or screenable markers. This technique provides an immediate and non‐destructive method for identifying transformed dry seeds. It identified the heterozygous transformed seeds among the T1 population and the homozygous seeds among the T2 population with a false‐discovery rate of <1%. The FAST marker reduces the length of time required to produce homozygous transgenic lines from 7.5 to 4 months. Furthermore, it does not require sterilization, clean‐bench protocols or the handling of large numbers of plants. This technology should greatly facilitate the generation of transgenic Arabidopsis plants. 相似文献
48.
49.
Various Cucurbita seed globulins showed patterns similar toone another on SDS-gel electrophoresis, and ß bandsfor unreduced globulins and , ', and ' bands for reduced ones.On gel electrophoresis in 6 M urea, reduced globulin gave twoacidic and two basic bands. These corresponded to and ' chainsand 1 and 2 chains, respectively, identified by two-dimensionalurea-SDS gel electrophoresis. The compositions of the and ßsubunits were proposed. (Received September 8, 1977; ) 相似文献
50.
Keiko Sasaki Tomohiro Ichinose Tomoko Doko Ikuko Imoto Fred Jopp 《Landscape and Ecological Engineering》2016,12(1):61-72
Distributions of lucidophyllous species are limited due to the fragmentation of laurel forest. On Komayama Hill in central Japan, we evaluated the colonization of typical lucidophyllous vascular plants from a 350-year-old laurel forest into adjacent abandoned secondary forest for conservation and restoration purposes. A total of 14 consecutive subplots were established along the vegetation border between the two forests (length, 30 m; width, 5 m), extending 70 m into the secondary forest; 18 quadrats of old-growth forest were surveyed. Edge effects of old-growth forest were found to play an important role in re-establishing lucidophyllous saplings and seedlings in the secondary forest. In particular, the abundances of the four dominant canopy species of the old-growth forest significantly decreased with increasing distance. Hence, they are expected to colonize further into the secondary forest and, ultimately, to dominate the canopy. However, the number of lucidophyllous species did not change with distance. Species such as Ficus nipponica, Damnacanthus indicus, Ilex integra, and Lemmaphyllum microphyllum were near-completely or completely limited to the old-growth forest. They are known to be negatively affected by forest fragmentation and were observed to be struggling to colonize the exterior of the old-growth forest even after 60 years of abandonment. Their absence highlighted the limited colonization capacities of some old-growth forest species and underlined the time required for habitat restoration following human disturbance. We conclude that it is important to consider the population dynamics of dominant canopy species and the colonization of these interior species when assessing the habitat expansion of lucidophyllous species and hence the restoration of degraded lands. 相似文献