全文获取类型
收费全文 | 1581篇 |
免费 | 107篇 |
国内免费 | 4篇 |
专业分类
1692篇 |
出版年
2023年 | 13篇 |
2022年 | 40篇 |
2021年 | 68篇 |
2020年 | 27篇 |
2019年 | 30篇 |
2018年 | 45篇 |
2017年 | 35篇 |
2016年 | 50篇 |
2015年 | 61篇 |
2014年 | 75篇 |
2013年 | 105篇 |
2012年 | 124篇 |
2011年 | 122篇 |
2010年 | 50篇 |
2009年 | 57篇 |
2008年 | 87篇 |
2007年 | 74篇 |
2006年 | 64篇 |
2005年 | 40篇 |
2004年 | 44篇 |
2003年 | 38篇 |
2002年 | 31篇 |
2001年 | 41篇 |
2000年 | 37篇 |
1999年 | 19篇 |
1998年 | 12篇 |
1997年 | 11篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 8篇 |
1992年 | 29篇 |
1991年 | 22篇 |
1990年 | 19篇 |
1989年 | 27篇 |
1988年 | 14篇 |
1987年 | 8篇 |
1986年 | 16篇 |
1985年 | 7篇 |
1984年 | 11篇 |
1982年 | 6篇 |
1980年 | 7篇 |
1979年 | 14篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1975年 | 10篇 |
1974年 | 5篇 |
1973年 | 7篇 |
1972年 | 6篇 |
1971年 | 8篇 |
1969年 | 5篇 |
排序方式: 共有1692条查询结果,搜索用时 8 毫秒
1.
Isolation and screening of potential actinobacteria for rapid composting of rice straw 总被引:2,自引:0,他引:2
Rice straw is produced as a by-product from rice cultivation, which is composed largely of lignocellulosic materials amenable
to general biodegradation. Lignocellulolytic actinobacteria can be used as a potential agent for rapid composting of bulky
rice straw. Twenty-five actinobacteria isolates were isolated from various in situ and in vitro rice straw compost sources.
Isolates A2, A4, A7, A9 and A24 were selected through enzymatic degradation of starch, cellulose and lignin followed by the
screening for their adaptability on rice straw powder amended media. The best adapted isolate (A7) was identified as Micromonospora
carbonacea. It was able to degrade cellulose, hemicelluloses and carbon significantly (P ≤ 0.05) over the control. C/N ratio was reduced to 18.1 from an initial value of 29.3 in 6 weeks of composting thus having
the potential to be used in large scale composting of rice straw. 相似文献
2.
3.
4.
Munirul Alam Shin-ichi Miyoshi Ikuyo Maruo Chiemi Ogawa Sumio Shinoda 《Microbiology and immunology》1994,38(6):467-470
The protease elaborated by Vibrio mimicus is known to possess hemagglutinating ability to chicken erythrocytes, the well-known HA/protease. A non-protease hemagglutinin (HA) with strong agglutinating ability towards rabbit erythrocytes was obtained from 32 hr culture supernatant of a pathogenic environmental strain of V. mimicus. This HA (V. mimicus HA: VMHA) appeared stable at relatively higher temperature and agglutinated the erythrocytes from rabbit, guinea pig and mouse but not the erythrocytes from chicken, bovine, horse and sheep. Simple sugars, metal ions and chelating agents failed to inhibit the activity of VMHA. The activity of VMHA was found to be sensitive to digestion by proteolytic enzymes including HA/protease. These results provide evidence for the existence of novel HA other than HA/protease in V. mimicus. 相似文献
5.
C L Cohn J R Sprinkle J Alam M Hermodson T Meyer D W Krogmann 《Archives of biochemistry and biophysics》1989,270(1):227-235
The low-potential cytochrome c550 has been purified from the cyanobacterium Microcystis aeruginosa and its amino acid sequence has been determined. The protein contains 135 amino acid residues with the Cys-X-X-Cys-His heme binding site at residues 37 to 41. The sequence from residue 28 to 45 shows similarity to cytochrome c553 residues 1 to 18 when the heme binding sites are aligned. Another region of similarity is in the carboxyl-terminal regions of these two proteins. The two aligning regions of cytochrome c553 correspond to helical segments in other related cytochromes. A partial sequence of cytochrome c550 from Aphanizomenon flos-aquae was obtained and showed a 48% identity to the sequence of the M. aeruginosa cytochrome. The single methionine residue in cytochrome c550 of M. aeruginosa occurs at position 119 but there is no methionine in this region in the A. flos-aquae cytochrome, indicating that methionine is not the sixth ligand to the heme iron atom. Histidine 92 is a possible sixth ligand in M. aeruginosa cytochrome c550. The far-uv circular dichroism spectrum indicates that this protein is approximately 17% alpha helix, 42% beta-pleated sheet, and 41% random coil. 相似文献
6.
Design of liposome to improve encapsulation efficiency of gelonin and its effect on immunoreactivity and ribosome inactivating property 总被引:1,自引:0,他引:1
Anis Alam S. R. K. Bhuri Anil K. Mavila Vinod Singh 《Molecular and cellular biochemistry》1992,112(2):97-109
Gelonin, purified from the seeds of Gelonium multiflorum, using cation-exchange and gel-filtration chromatography was characterised for its purity, homogeneity and molecular weight by reverse-phase HPLC (RP-HPLC) and SDS-PAGE analysis. The HPLC purified gelonin was used for entrapment studies in the liposomes. Liposomes were prepared by reverse phase evaporation (REV) technique using three different types of lipid composition in the same molar ratio. The method resulted in 75–80% entrapment efficiency of gelonin in the liposomes. Entrapped and unentrapped gelonin was characterized for physico-chemical, immunochemical and biological properties. The immunoreactivity of entrapped gelonin was fully preserved but the ribosome-inactivating property was slightly inhibited. The method involved mild conditions, highly reproducible and the liposomes produced appeared to be stable for several months. It has important implications in the development of cell type specific cytotoxic agents where a chemical cross-linking is involved which significantly inhibits both immunoreactivity and ribosome-inactivating ability of the toxin. 相似文献
7.
A thermotolerant methylotrophicBacillus sp. (KISRI TM1A, NCIMB 40040), isolated from the Kuwaiti environment and belonging to the group II spore-forming, bacilli, could not be correlated with any knownBacillus sp. It may, therefore, be a new species. It grew at temperatures from 37° to 58°C from pH 6.5 to 9.0 and on methanol up to 40 g l–1. It grew well in a chemostat. Its biomass yield coefficient was improved by about 30% by optimization of medium and growth conditions, reaching a maximum of 0.44g g–1 at 45°C pH 6.8 to 7.0, dilution rate 0.25 h–1 with methanol at 10 g l–1. Average crude protein and amino acid content were 84% and 60%, respectively, and maximum productivity attained under laboratory conditions was 5.06 g l–1h–1. It was concluded that this strain has good potential for use in single-cell protein production. 相似文献
8.
Molecular cloning of a cDNA coding for 70 kilodalton subunit of soluble guanylate cyclase from rat lung 总被引:6,自引:0,他引:6
M Nakane S Saheki T Kuno K Ishii F Murad 《Biochemical and biophysical research communications》1988,157(3):1139-1147
A complementary DNA clone corresponding to the 70 kDa subunit of soluble guanylate cyclase (EC 4.6.1.2) of rat lung has been isolated. The primary structure of the cDNA consisted of 3063 nucleotides including a 1857-nucleotide coding region for 619 amino acids, and the calculated molecular weight was 70476. Blot hybridization of total poly(A)+RNAs from rat tissues detected a mRNA of about 3.4 kilobases. The amount of mRNA was abundant in lung, cerebrum and cerebellum, moderate in heart and kidney, and low in liver and muscle. Southern blot analysis of high molecular weight genomic DNA from rat liver indicated the presence of one gene in the rat haploid genome. The amino acid sequence of the 70 kDa subunit has partial homology with particulate guanylate cyclase from sea-urchin sperm, and protein phosphatase inhibitor I. 相似文献
9.
Comparison of binding and cyclic GMP accumulation by atrial natriuretic peptides in endothelial cells 总被引:8,自引:0,他引:8
Rat 125I-labeled atrial natriuretic factor (ANF (8-33)) was used to identify ANF receptors on cultured bovine aortic endothelial cells. Specific binding of 125I-ANF at 37 degrees C to confluent endothelial cells was saturable and of high affinity. Scatchard analysis of the equilibrium binding data indicated that endothelial cells contain a single class of binding sites with a Kd of 0.1 +/- 0.01 nM. This particular clone of endothelial cells had 16000 +/- 1300 receptors per cell. The order of potency for competing with 125I-ANF binding was human atrial natriuretic peptide (hANP) = atrial natriuretic factor (ANF (8-33)) greater than atriopeptin II greater than atriopeptin III greater than atriopeptin. The weakest competitor, atriopeptin I, had a K1 of 0.45 nM, which was only 6-fold higher than the K1 for hANP and ANF (8-33). ANF (8-33) and hANP in the presence of 0.5 mM isobutylmethyl-xanthine produced a 15-20-fold increase in cyclic GMP content at 10 pM and a maximal 500-fold elevation of cyclic GMP at 10 nM. The concentrations required to elicit a half-maximal increase in cyclic GMP for hANP, ANF (8-33), atriopeptin I, atriopeptin II and atriopeptin III were 0.30, 0.35, greater than 500, 4.0 and 5.0 nM, respectively. Although atriopeptin I acted as a partial agonist, it was unable to antagonize the effect of ANF (8-33) on cyclic GMP formation. These findings suggest that endothelial cells have multiple and functionally distinct ANF-binding sites. 相似文献
10.