全文获取类型
收费全文 | 2096篇 |
免费 | 150篇 |
出版年
2021年 | 20篇 |
2020年 | 13篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 25篇 |
2015年 | 44篇 |
2014年 | 49篇 |
2013年 | 84篇 |
2012年 | 93篇 |
2011年 | 83篇 |
2010年 | 59篇 |
2009年 | 44篇 |
2008年 | 107篇 |
2007年 | 102篇 |
2006年 | 76篇 |
2005年 | 97篇 |
2004年 | 110篇 |
2003年 | 104篇 |
2002年 | 81篇 |
2001年 | 90篇 |
2000年 | 69篇 |
1999年 | 63篇 |
1998年 | 34篇 |
1997年 | 28篇 |
1996年 | 19篇 |
1995年 | 12篇 |
1994年 | 16篇 |
1993年 | 21篇 |
1992年 | 67篇 |
1991年 | 44篇 |
1990年 | 45篇 |
1989年 | 65篇 |
1988年 | 49篇 |
1987年 | 41篇 |
1986年 | 29篇 |
1985年 | 37篇 |
1984年 | 19篇 |
1982年 | 16篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1977年 | 12篇 |
1976年 | 11篇 |
1975年 | 12篇 |
1974年 | 13篇 |
1973年 | 20篇 |
1971年 | 16篇 |
1970年 | 15篇 |
1968年 | 17篇 |
1967年 | 20篇 |
1966年 | 17篇 |
排序方式: 共有2246条查询结果,搜索用时 125 毫秒
991.
Binding of streptonigrin to DNA 总被引:1,自引:0,他引:1
992.
Normal macrophages were activated to antibody-dependent cytotoxic effector cells by in vitro treatment with the local anesthetic lidocaine. Experiments on the dose-response and time course of the effect of lidocaine showed that incubation of normal macrophages with 10 mM lidocaine for 10 min at 28 C was enough for induction of antibody-dependent cellular cytotoxicity. The activation by lidocaine was accompanied by enhanced phagocytosis of sheep red blood cells (SRBC) sensitized with anti-SRBC antiserum, but not enhanced ingestion of polystyrene latex particles (PLP). These findings suggest that lidocaine, which has various effects on cell membranes, induces some perturbation of macrophage membranes, resulting in activation of Fc receptor functions in antibody-dependent cytotoxicity and phagocytosis. 相似文献
993.
994.
995.
Crystallization and preliminary X-ray diffraction studies of aspartic proteinase from Irpex lacteus.
H Kobayashi K Kasamo H Mizuno H Kim I Kusakabe K Murakami 《Journal of molecular biology》1992,226(4):1291-1293
Crystals of ILAP (Irpex lacteus aspartic proteinase) have been obtained by the hanging drop method using ammonium sulfate as a precipitant. The crystals are monoclinic, space group P2(1) with cell dimensions a = 54.5 A, b = 79.6 A, c = 37.5 A, beta = 96.8 degrees. The crystals are quite stable to X-rays and diffract beyond 1.9 A resolution. There is one molecule in the asymmetric unit. 相似文献
996.
The localization of acid and alkaline phosphatases in Staphylococcus aureus was studied by fractionation of cells after treatment with the L-11 enzyme and by electron microscopic histochemistry. The two enzyme activities were located in distinctly different positions at the surface of the cells. Acid phosphatase appeared to be localized around the cell membrane of the bacteria, because the enzyme was recovered exclusively in the membrane fraction and because deposition of lead phosphate was detected by electron microscopic histochemistry on the inner surface of the cell membrane of intact bacteria and spheroplasts. The highest specific activity of alkaline phosphatase was also associated with the membrane fraction. However, on electron microscopic histochemistry of intact cells, the deposition of lead phosphate was only seen on the outer surface of the cell wall. 相似文献
997.
998.
999.
Kouichi Mizuno Masahiro Matsuzaki Shiho Kanazawa Tetsuo Tokiwano Yuko Yoshizawa Misako Kato 《Biochemical and biophysical research communications》2014
Trigonelline (N-methylnicotinate), a member of the pyridine alkaloids, accumulates in coffee beans along with caffeine. The biosynthetic pathway of trigonelline is not fully elucidated. While it is quite likely that the production of trigonelline from nicotinate is catalyzed by N-methyltransferase, as is caffeine synthase (CS), the enzyme(s) and gene(s) involved in N-methylation have not yet been characterized. It should be noted that, similar to caffeine, trigonelline accumulation is initiated during the development of coffee fruits. Interestingly, the expression profiles for two genes homologous to caffeine synthases were similar to the accumulation profile of trigonelline. We presumed that these two CS-homologous genes encoded trigonelline synthases. These genes were then expressed in Escherichiacoli, and the resulting recombinant enzymes that were obtained were characterized. Consequently, using the N-methyltransferase assay with S-adenosyl[methyl-14C]methionine, it was confirmed that these recombinant enzymes catalyzed the conversion of nicotinate to trigonelline, coffee trigonelline synthases (termed CTgS1 and CTgS2) were highly identical (over 95% identity) to each other. The sequence homology between the CTgSs and coffee CCS1 was 82%. The pH-dependent activity curve of CTgS1 and CTgS2 revealed optimum activity at pH 7.5. Nicotinate was the specific methyl acceptor for CTgSs, and no activity was detected with any other nicotinate derivatives, or with any of the typical substrates of B′-MTs. It was concluded that CTgSs have strict substrate specificity. The Km values of CTgS1 and CTgS2 were 121 and 184 μM with nicotinic acid as a substrate, and 68 and 120 μM with S-adenosyl-l-methionine as a substrate, respectively. 相似文献
1000.
Rick K. Huang Ulrich Baxa Gudrun Aldrian Abdullah B. Ahmed Joseph S. Wall Naoko Mizuno Oleg Antzutkin Alasdair C. Steven Andrey V. Kajava 《Biophysical journal》2014
The established correlation between neurodegenerative disorders and intracerebral deposition of polyglutamine aggregates motivates attempts to better understand their fibrillar structure. We designed polyglutamines with a few lysines inserted to overcome the hindrance of extreme insolubility and two D-lysines to limit the lengths of β-strands. One is 33 amino acids long (PolyQKd-33) and the other has one fewer glutamine (PolyQKd-32). Both form well-dispersed fibrils suitable for analysis by electron microscopy. Electron diffraction confirmed cross-β structures in both fibrils. Remarkably, the deletion of just one glutamine residue from the middle of the peptide leads to substantially different amyloid structures. PolyQKd-32 fibrils are consistently 10–20% wider than PolyQKd-33, as measured by negative staining, cryo-electron microscopy, and scanning transmission electron microscopy. Scanning transmission electron microscopy analysis revealed that the PolyQKd-32 fibrils have 50% higher mass-per-length than PolyQKd-33. This distinction can be explained by a superpleated β-structure model for PolyQKd-33 and a model with two β-solenoid protofibrils for PolyQKd-32. These data provide evidence for β-arch-containing structures in polyglutamine fibrils and open future possibilities for structure-based drug design. 相似文献