全文获取类型
收费全文 | 488篇 |
免费 | 27篇 |
出版年
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 3篇 |
2016年 | 6篇 |
2015年 | 9篇 |
2014年 | 17篇 |
2013年 | 36篇 |
2012年 | 20篇 |
2011年 | 18篇 |
2010年 | 13篇 |
2009年 | 13篇 |
2008年 | 24篇 |
2007年 | 24篇 |
2006年 | 28篇 |
2005年 | 32篇 |
2004年 | 33篇 |
2003年 | 29篇 |
2002年 | 26篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 12篇 |
1998年 | 6篇 |
1997年 | 8篇 |
1996年 | 2篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 10篇 |
1977年 | 4篇 |
1976年 | 10篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1972年 | 2篇 |
1970年 | 3篇 |
排序方式: 共有515条查询结果,搜索用时 15 毫秒
71.
Fujii R Shimonaka S Uchida N Gardiner AT Cogdell RJ Sugisaki M Hashimoto H 《Photosynthesis research》2008,95(2-3):327-337
Typical purple bacterial photosynthetic units consist of supra-molecular arrays of peripheral (LH2) and core (LH1-RC) antenna
complexes. Recent atomic force microscopy pictures of photosynthetic units in intact membranes have revealed that the architecture
of these units is variable (Scheuring et al. (2005) Biochim Bhiophys Acta 1712:109–127). In this study, we describe methods for the construction of heterologous photosynthetic
units in lipid-bilayers from mixtures of purified LH2 (from Rhodopseudomonas acidophila) and LH1-RC (from Rhodopseudomonas viridis) core complexes. The architecture of these reconstituted photosynthetic units can be varied by controlling ratio of added
LH2 to core complexes. The arrangement of the complexes was visualized by electron-microscopy in combination with Fourier
analysis. The regular trigonal array of the core complexes seen in the native photosynthetic membrane could be regenerated
in the reconstituted membranes by temperature cycling. In the presence of added LH2 complexes, this trigonal symmetry was
replaced with orthorhombic symmetry. The small lattice lengths for the latter suggest that the constituent unit of the orthorhombic
lattice is the LH2. Fluorescence and fluorescence-excitation spectroscopy was applied to the set of the reconstituted membranes
prepared with various proportions of LH2 to core complexes. Remarkably, even though the LH2 complexes contain bacteriochlorophyll
a, and the core complexes contain bacteriochlorophyll b, it was possible to demonstrate energy transfer from LH2 to the core complexes. These experiments provide a first step along
the path toward investigating how changing the architecture of purple bacterial photosynthetic units affects the overall efficiency
of light-harvesting. 相似文献
72.
Changes in the motility time of spermatozoa collected from the testes and the sperm duct of normal and sex-reversed male (XX) rainbow trout in physiological balanced salt solution were examined after incubation in artificial seminal plasmas of various pHs. Although untreated spermatozoa from the sperm duct retained motility for 60–90 s in the balanced salt solution, the spermatozoa collected from the testes were immotile. During the incubation in artificial seminal plasma of pH 7.0, the spermatozoa from the sperm duct hardly moved, similar to the testicular spermatozoa in the balanced salt solution. By suspending and incubating the testicular spermatozoa in artificial seminal plasma of pH 9.9 for 2 h at 4°C, the percentage of motile spermatozoa increased from 0–5% to 80%. The spermatozoa remained motile for at least 2 min after long-term incubation (12 h). When the full-sib eggs were inseminated with untreated testicular spermatozoa or testicular sperm treated for 2 h at high pH, the percentage survival increased from 5.5% to 53.8% at the eyed stage due to the high-pH treatment. The incubation of the spermatozoa in high-pH artificial seminal plasma improved the motility of the spermatozoa from the testes of the sex-reversed male that had lost its sperm duct. By this treatment, it is possible to markedly increase the mass production efficiency of all-female or all-female triploid sterile progenies. 相似文献
73.
Misumi S Eto A Mitsumata R Yamada M Takamune N Shoji S 《Biochemical and biophysical research communications》2008,377(2):617-621
Our previous study demonstrated that the immunization with a cycloimmunogen derived from extracellular loop-2 (ECL-2) of CCR5 (cDDR5) attenuated acute phase of CCR5-tropic simian-human immunodeficiency virus (SHIV)SF162P3 replication in vivo. Although the study showed that the antisera raised against cDDR5 reacted with cell-expressed CCR5, we have not yet demonstrated whether the antisera can react with virion-incorporated CCR5. Here, we show that rhesus cDDR5 (rcDDR5)-specific antibodies react with not only cell-expressed but also virion-incorporated simian CCR5s (siCCR5s), but may predominantly exert their inhibitory effects on simian immunodeficiency virus (SIV) infection by the binding of cell-expressed rather than virion-incorporated CCR5s. These results suggest that the virion-incorporated CCR5 may contribute to the reactivation of the anti-rcDDR5 antibody-producing B-cells by SIV particles after rcDDR5 immunization, although the binding of anti-rcDDR5 antibody to virion-incorporated CCR5 results in a partial inhibitory effect on SIV infection. 相似文献
74.
75.
76.
Stability and ferrous iron content of the nitrogenase and its components from Azotobacter vinelandii
Summary Nitrogenase of Azotobacter vinelandii is sensitive to oxygen, and sensitivity develops during purification. Such inactivation is well prevented by 0.1% hydroquinone plus 0.01% ascorbate, which are also effective in preventing inactivation of enzyme on storage under H2. Activity is proportional to ferrous iron content of crude sample of enzyme. On storage at 0°C, 0.3 M KCl inactivates the enzyme, while KCl stabilizes its components. Nitrogenase is not cold labile, while the components are cold labile; Fe, Mo-component is most stable at 22°C and Fe-component at 13.5°C. Nitrogenase substrates, except N2, stabilize nitrogenase, but not the components. 相似文献
77.
78.
Megumi Narukawa‐Nara Ayako Nakamura Ko Kikuzato Yusuke Kakei Akiko Sato Yuka Mitani Yumiko Yamasaki‐Kokudo Takahiro Ishii Ken‐ichiro Hayashi Tadao Asami Takehiko Ogura Shigeo Yoshida Shozo Fujioka Takashi Kamakura Tsutomu Kawatsu Masanori Tachikawa Kazuo Soeno Yukihisa Shimada 《The Plant journal : for cell and molecular biology》2016,87(3):245-257
We previously reported l ‐α‐aminooxy‐phenylpropionic acid (AOPP) to be an inhibitor of auxin biosynthesis, but its precise molecular target was not identified. In this study we found that AOPP targets TRYPTOPHAN AMINOTRANSFERASE of ARABIDOPSIS 1 (TAA1). We then synthesized 14 novel compounds derived from AOPP to study the structure–activity relationships of TAA1 inhibitors in vitro. The aminooxy and carboxy groups of the compounds were essential for inhibition of TAA1 in vitro. Docking simulation analysis revealed that the inhibitory activity of the compounds was correlated with their binding energy with TAA1. These active compounds reduced the endogenous indole‐3‐acetic acid (IAA) content upon application to Arabidopsis seedlings. Among the compounds, we selected 2‐(aminooxy)‐3‐(naphthalen‐2‐yl)propanoic acid (KOK1169/AONP) and analyzed its activities in vitro and in vivo. Arabidopsis seedlings treated with KOK1169 showed typical auxin‐deficient phenotypes, which were reversed by exogenous IAA. In vitro and in vivo experiments indicated that KOK1169 is more specific for TAA1 than other enzymes, such as phenylalanine ammonia‐lyase. We further tested 41 novel compounds with aminooxy and carboxy groups to which we added protection groups to increase their calculated hydrophobicity. Most of these compounds decreased the endogenous auxin level to a greater degree than the original compounds, and resulted in a maximum reduction of about 90% in the endogenous IAA level in Arabidopsis seedlings. We conclude that the newly developed compounds constitute a class of inhibitors of TAA1. We designated them ‘pyruvamine’. 相似文献
79.
Suguru Takatsuto Nahoko Kosuga Bun-ichi Abe Takahiro Noguchi Shozo Fujioka Takao Yokota 《Journal of plant research》1999,112(1):27-33
Triticum aestivum L.) and foxtail millet (Setaria italica Beauv.) were found by GC-MS to contain, in addition to bulk sterols, 4-en-3-one steroids including 24-ethylcholesta-4,24(28)Z- dien-3-one (a new steroid), 24-methylcholest-4-en-3-one, 24-ethylcholesta-4,22E-dien-3-one and 24-ethylcholest-4-en-3-one, as well as 5α-steroidal 3-one compounds including 24-methyl-5α-cholestan-3-one,
24-ethyl-5α-cholestan-3-one and 24-ethyl 5α-cholest-22E-en-3-one (in S. italica only). Analysis of free sterol and steryl ester fractions indicated that campestanol and sitostanol were present at high
levels in both seeds. These results suggest that the seeds of T. aestivum and S. italica synthesize campestanol from campesterol via 24-methylcholest-4-en-3-one and 24-methyl-5α-cholestan-3-one as has already been
demonstrated in Arabidopsis thaliana L., and also produce sitostanol from sitosterol via 24-ethylcholest-4-en-3-one and 24-ethyl-5α-chotestan-3-one. Biosynthetic
relationships of campestanol and sitostanol with C28 and C29 brassinosteroids are discussed.
Received 4 September 1998/ Accepted in revised form 26 November 1998 相似文献
80.