全文获取类型
收费全文 | 7091篇 |
免费 | 342篇 |
国内免费 | 8篇 |
出版年
2023年 | 12篇 |
2022年 | 10篇 |
2021年 | 61篇 |
2020年 | 44篇 |
2019年 | 60篇 |
2018年 | 97篇 |
2017年 | 85篇 |
2016年 | 115篇 |
2015年 | 198篇 |
2014年 | 253篇 |
2013年 | 522篇 |
2012年 | 439篇 |
2011年 | 432篇 |
2010年 | 276篇 |
2009年 | 292篇 |
2008年 | 470篇 |
2007年 | 462篇 |
2006年 | 444篇 |
2005年 | 492篇 |
2004年 | 483篇 |
2003年 | 453篇 |
2002年 | 409篇 |
2001年 | 63篇 |
2000年 | 75篇 |
1999年 | 73篇 |
1998年 | 92篇 |
1997年 | 73篇 |
1996年 | 76篇 |
1995年 | 81篇 |
1994年 | 54篇 |
1993年 | 70篇 |
1992年 | 67篇 |
1991年 | 57篇 |
1990年 | 42篇 |
1989年 | 46篇 |
1988年 | 27篇 |
1987年 | 49篇 |
1986年 | 36篇 |
1985年 | 26篇 |
1984年 | 38篇 |
1983年 | 30篇 |
1982年 | 42篇 |
1981年 | 32篇 |
1980年 | 23篇 |
1979年 | 29篇 |
1978年 | 28篇 |
1977年 | 18篇 |
1976年 | 21篇 |
1975年 | 11篇 |
1974年 | 13篇 |
排序方式: 共有7441条查询结果,搜索用时 15 毫秒
11.
12.
Shigeo Koyasu Makoto Asada Akio Fukuda Yoshimi Okada 《Journal of molecular biology》1981,153(2):471-475
The mode of polymerization of two species of flagellins, flagellin A and flagellin B, in polar flagella of Caulobacter crescentus was examined. By immunological staining we found that 1 to 1.2 μm of the portion of the flagellar filament proximal to the cell was composed of flagellin B, whereas about 5 μm of the distal portion was composed of flagellin A. This result, together with the previous observation that a flagellin B-less mutant cannot form normal flagella but instead forms stubs in spite of their high level of flagellin A synthesis, indicates that flagellin B is very important for the formation of complete flagella and/or for the initiation of filament formation from the hook. 相似文献
13.
Naoki Tokuhara Kana Namiki Mai Uesugi Chihiro Miyamoto Makoto Ohgoh Katsutoshi Ido Takashi Yoshinaga Toshihiko Yamauchi Junro Kuromitsu Sadao Kimura Norimasa Miyamoto Yoshitoshi Kasuya 《The Journal of biological chemistry》2010,285(43):33294-33306
One of the family of voltage-gated calcium channels (VGCC), the N-type Ca2+ channel, is located predominantly in neurons and is associated with a variety of neuronal responses, including neurodegeneration. A precise mechanism for how the N-type Ca2+ channel plays a role in neurodegenerative disease, however, is unknown. In this study, we immunized N-type Ca2+ channel α1B-deficient (α1B−/−) mice and their wild type (WT) littermates with myelin oligodendrocyte glycoprotein 35–55 and analyzed the progression of experimental autoimmune encephalomyelitis (EAE). The neurological symptoms of EAE in the α1B−/− mice were less severe than in the WT mice. In conjunction with these results, sections of the spinal cord (SC) from α1B−/− mice revealed a reduction in both leukocytic infiltration and demyelination compared with WT mice. No differences were observed in the delayed-type hypersensitivity response, spleen cell proliferation, or cytokine production from splenocytes between the two genotypes. On the other hand, Western blot array analysis and RT-PCR revealed that a typical increase in the expression of MCP-1 in the SC showed a good correlation with the infiltration of leukocytes into the SC. Likewise, immunohistochemical analysis showed that the predominant source of MCP-1 was activated microglia. The cytokine-induced production of MCP-1 in primary cultured microglia from WT mice was significantly higher than that from α1B−/− mice and was significantly inhibited by a selective N-type Ca2+ channel antagonist, ω-conotoxin GVIA or a withdrawal of extracellular Ca2+. These results suggest that the N-type Ca2+ channel is involved in the pathogenesis of EAE at least in part by regulating MCP-1 production by microglia. 相似文献
14.
Mycoplasmas exhibit a novel, substrate-dependent gliding motility that is driven by ∼400 “leg” proteins. The legs interact with the substrate and transmit the forces generated by an assembly of ATPase motors. The velocity of the cell increases linearly by nearly 10-fold over a narrow temperature range of 10-40°C. This corresponds to an Arrhenius factor that decreases from ∼45 kBT at 10°C to ∼10 kBT at 40°C. On the other hand, load-velocity curves at different temperatures extrapolate to nearly the same stall force, suggesting a temperature-insensitive force-generation mechanism near stall. In this article, we propose a leg-substrate interaction mechanism that explains the intriguing temperature sensitivity of this motility. The large Arrhenius factor at low temperature comes about from the addition of many smaller energy barriers arising from many substrate-binding sites at the distal end of the leg protein. The Arrhenius dependence attenuates at high temperature due to two factors: 1), the reduced effective multiplicity of energy barriers intrinsic to the multiple-site binding mechanism; and 2), the temperature-sensitive weakly facilitated leg release that curtails the power stroke. The model suggests an explanation for the similar steep, sub-Arrhenius temperature-velocity curves observed in many molecular motors, such as kinesin and myosin, wherein the temperature behavior is dominated not by the catalytic biochemistry, but by the motor-substrate interaction. 相似文献
15.
16.
Mouse serum (MS) effected a rapid accumulation of many lipid droplets by cultured cells in the growing or resting state. MS-induced adipose conversion in all of 12 randomly selected cell lines, including human, mink, rat, and mouse cells and almost all of the cells in a culture dish were converted. Under excessive amounts of MS, the cells became mature adipocytes, lost the ability to divide and soon died. However, proliferation of adipocytes induced by smaller quantities of MS was not different from that of control cells in calf serum (CS). When adipose conversion developed, oncorna virus producing cells ceased virus production and there was a clear connection between decrease of virus production and rate of adipose conversion. The adipose conversion of 3T3-FL cells grown for 7 days in the presence of bromodeoxyuridine (BUdR) was inhibited. Actinomycin D (actD) and cycloheximide also inhibited adipose conversion. It is suggested that the cells may have an inherent ability to differentiate into adipocytes. 相似文献
17.
Makoto Misono 《Molecular Engineering》1993,3(1-3):193-203
First, fundamental properties (structure, acid and redox properties) and advantages of solid polyoxometalate catalysts (catalyst design by acid and redox control, molecularity, unusual reaction field and unique basicity) are explained. Then, the mechanism of alcohol dehydration elucidated by direct observation of reaction intermediates by solid-state NMR and the very high activity of Cs2.5H0.5PW12O40 are described. Finally several industrial applications of polyoxometalate catalysts are briefly introduced placing stress on the role of unique chemical properties of polyoxometalates. 相似文献
18.
Kanji Takeo Reiko Tanaka Makoto Miyaji Kazuko Nishimura 《FEMS microbiology letters》1995,129(2-3):231-235
Abstract Stationary-phase cells of Cryptococcus neoformans displayed two morphological characteristics: virtually all the cells were unbudded even in the early stationary phase and even when grown in rich media, and average cell size increased from that of exponential-phase cells. DNA contents for small and large stationary-phase cells were determined by quantitative fluorescence microscopy after DNA staining with propidium iodide or DAPI. Small cells contained G, DNA, whereas large unbudded cells had either a G2 or G1 DNA content, indicating that Cr. neoformans can enter into the stationary phase from either the G1 or G2 period. 相似文献
19.
20.
Michihiro Sugahara Makoto Kandatsu 《Bioscience, biotechnology, and biochemistry》2013,77(12):1389-1393
The metabolic half lives of glycine in the tissue-proteins of the rooster were determined by single oral dose of 2-C14 glycine before measuring the amount of synthesized glycine in the rooster by ?constant pool? method. The specific activity of glycine originated from the purine ring of uric acid showed the highest value for 5 hrs. after administration, following rapid decrease until 7 days, thereafter slower one.Although the specific activity of glycine in the tissue protein (serum and liver) decreased exponentially, its trend was not distinct in the pectoral muscle, and in the early period its decrease seemed to be considerably fast (t1/2 about 6 days).The specific activities of glycine in the serum protein were always higher than those in the liver protein. The metabolic half livers obtained were as follows. Liver: Faster 2 days, slower 11 days. Serum: faster 2 days, slower 11 days. Pectoral muscle: faster 6 days, slower 30 days. Recovery of C14 into 4-C and 5-C in the purine ring of excreted uric acid during 24 hours after the administration of isotope was about 24%. 相似文献