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排序方式: 共有1245条查询结果,搜索用时 15 毫秒
1.
T Kakizono T Nihira H Taguchi 《Biochemical and biophysical research communications》1986,137(3):964-969
Tryptophanase has an essential tyrosyl residue/active site which can be modified by tetranitromethane. Pyridoxal 5'-phosphate can prevent this modification efficiently, whereas pyridoxal 5'-phosphate N-oxide cannot, indicating that the free pyridinium N is required for the interaction of the coenzyme with the tyrosyl residue, probably via a hydrogen bond. The weakened binding of the coenzyme to the modified enzyme was confirmed on gel filtration, the modified enzyme being dissociated from the coenzyme seven-fold faster than the native enzyme. Furthermore, absorption spectral analyses demonstrated that the modified enzyme can catalyze the transaldimination step, but fails to abstract the alpha-H of substrates. The tyrosyl residue, therefore, not only participates in coenzyme binding, but also contributes to alpha-H labilization. 相似文献
2.
Optimum conditions for ursodeoxycholic acid production from lithocholic acid by Fusarium equiseti M41. 总被引:1,自引:1,他引:0 下载免费PDF全文
Ursodeoxycholic acid dissolves cholesterol gallstones in humans. In the present study optimum conditions for ursodeoxycholic acid production by Fusarium equiseti M41 were studied. Resting mycelia of F. equiseti M41 showed maximum conversion at 28 degrees C, pH 8.0, and dissolved oxygen tension of higher than 60% saturation. Monovalent cations, such as Na+, K+, and Rb+, stimulated the conversion rate more than twofold. In the presence of 0.5 M KCl, the initial uptake rate and equilibrium concentration of lithocholic acid (substrate) were enhanced by 5.7- and 1.7-fold, respectively. We confirmed that enzyme activity catalyzing 7 beta-hydroxylation of lithocholic acid was induced by substrate lithocholic acid. The activity in the mycelium was controlled by dissolved oxygen tension during cultivation: with a dissolved oxygen tension of 15% and over, the activity peak appeared at 25 h of cultivation, whereas the peak was delayed to 34 and 50 h with 5 and 0% dissolved oxygen tension, respectively. After reaching the maximum, the 7 beta-hydroxylation activity in the mycelium declined rapidly at pH 7.0, but the decline was retarded by increasing the pH to 8.0. Several combinations of operations, such as pH shift (from pH 7 to 8), addition of 0.5 M KCl, and dissolved oxygen control, were applied to the production of ursodeoxycholic acid in a jar fermentor, and a much larger amount of ursodeoxycholic acid (1.2 g/liter) was produced within 96 h of cultivation. 相似文献
3.
Sadaaki Iwanaga Takashi Morita Toshiyuki Miyata Takanori Nakamura Jun Aketagawa 《Journal of Protein Chemistry》1986,5(4):255-268
A hemocyte lysate from horseshoe crab produced a gel, when exposed to Gram-negative bacterial endotoxins. This gelation reaction of the lysate, so-called Limulus test, has been widely employed as a simple and very sensitive assay method for endotoxins. Recent biochemical studies on the principle of Limulus test indicate that the hemocytes contain several serine protease zymogens, which constitute a coagulation cascade triggered by endotoxins, and that there is a (1 3)--d-glucan-mediated coagulation pathway which also results in the formation of gel. Up to now, six protein components, designated coagulogen, proclotting enzyme, factor B, factor C, factor G and anti-LPS factor, all of which are closely associated with the endotoxin-mediated coagulation pathway, have been purified and biochemically characterized. Among these components, the complete amino acid sequences of coagulogens isolated from one American and three Asian species of horseshoe crabs have been established. Moreover, the reconstitution experiment using the isolated clotting factors, C, B, proclotting enzyme and coagulogen in the presence of endotoxin, leads to the formation of coagulin get. Based on these results, we propose here a mechanism for the Limulus coagulation cascade. 相似文献
4.
On cell proliferation and differentiation of the fundic mucosa of the golden hamster 总被引:1,自引:0,他引:1
Takanori Hattori 《Cell and tissue research》1974,148(2):213-226
5.
Isolated microspores of Chinese cabbage (Brassica campestris ssp. pekinensis) were incubated in modified NN medium containing 10% sucrose in darkness at 33°C for one day followed by culture at 25°C. After 14 days of culture, microspores developed into embryos ranging from globular to cotyledonary stage. Plants were regenerated after transfer of embryos to medium containing 3% sucrose and no plant growth regulators.Abbreviations NN
Nitsch and Nitsch
- MS
Murashige and Skoog
- NAA
naphthaleneacetic acid
- BA
6-benzylaminopurine 相似文献
6.
Inactivation of bleomycin by an N-acetyltransferase in the bleomycin-producing strain Streptomyces verticillus 总被引:1,自引:0,他引:1
Masanori Sugiyama Takanori Kumagai Mitsuhiko Shionoya Eiichi Kimura Julian E. Davies 《FEMS microbiology letters》1994,121(1):81-85
Abstract Bleomycin-producing Streptomyces verticillus ATCC15003 possesses a bleomycin acetyltransferase which inactivates the drug in the presence of acetyl coenzyme A. The site of acylation in enzymically prepared acetylbleomycin A2 was determined by nuclear magnetic resonance analysis; the primary amino group of the β-aminoalanine moiety of bleomycin was acetylated. Acetylbleomycin A2 had no detectable antibacterial activity and did not induce in vitro DNA degradation. 相似文献
7.
Zhao Ying Hiromasa Tojo Takanori Komatsubara Manabu Nakagawa Masami Inada Sumio Kawata Yuji Matsuzawa Mitsuhiro Okamoto 《生物化学与生物物理学报:疾病的分子基础》1994,1226(2):201-205
Enzyme activity, protein contents, and mRNA contents of group II phospholipase A2 (PLA2) in hepatocellular carcinoma (HCC) surgically obtained from 8 patients were compared with those in either its neighboring liver tissues or control liver tissues. The PLA2 specific activity towards the mixed micelles of 1-palmitoyl-2-oleoyl-phosphatidylglycerol and cholate was significantly greater in the tumor tissues (6.62 ± 1.46 nmol/min/mg) than those in the surrounding liver tissues (1.33 ± 0.22 nmol/min/mg) and controls (0.43 ± 0.04 nmol/min/mg). The results of immunoblot analysis using a specific anti-human group II PLA2 antibody and of Northern blot analysis using a human group II PLA2 cDNA as a probe demonstrated that group II PLA2 was responsible for the increased enzyme activity. The contents of immunoreactive group II PLA2 in the tumor tissues (8.81 ± 1.24 ng/mg) were significantly higher than those in the surrounding liver tissues (1.77 ± 0.27 ng/mg); those in the control tissues were below the analytical range of the method used. The group II PLA2 mRNA was also significantly increased in the tumor tissues, compared with that in the surrounding liver tissues, whereas it was not detectable in th controls. This indicates that group II PLA2 in HCC is induced at the pretranslational level. 相似文献
8.
Serum-free culture of rat keratinocytes 总被引:2,自引:0,他引:2
Hirosuke Oku Chikara Kumamoto Tomoyuki Miyagi Takanori Hiyane Junichi Nagata Isao Chinen 《In vitro cellular & developmental biology. Animal》1994,30(8):496-503
Summary Procedures for the serum-free culture of rat keratinocytes have been established. Basal cells prepared from epidermis of newborn
rat were stored in liquid nitrogen and used for primary culture. Among the available media, MCDB 153, developed originally
for human keratinocyte (HK) culture, was the best for the development of serum-free formulation. To grow rat keratinocytes,
bovine serum albumin was arbitrarily substituted for the macromolecule supplements needed for HK culture, i.e. fetal bovine
serum protein or bovine pituitary extract. Qualitative and quantitative adjustment of supplements was thereafter made to support
rapid cell growth. Satisfactory cell growth was achieved in the optimized medium of MCDB 153 supplemented with growth factors
and amino acids: insulin (10 μg/ml), hydrocortisone (0.1 μg/ml), epidermal growth factor (25 ng/ml), calcium chloride (0.2
mM), histidine (0.23 mM), isoleucine (0.05 mM), tryptophane (0.015 mM), threonine (1.25 mM), tyrosine (0.031 mM), alanine (4.08 mM), and albumin (2 mg/ml). This optimized culture system was superior to the original HK culture condition for rapid growth
of rat keratinocytes. Under our condition, cells grew as a monolayer, becoming confluent, but without stratification, and
were passaged 2 to 3 times without any changes in morphology. The serum-free formulation allows us to control more accurately
the concentrations of biomolecules in the medium including lipids and hormones, and therefore will be suitable for the study
focusing on lipid metabolism or hormonal regulation of rat keratinocytes. 相似文献
9.
Yoshikazu Nagata Tadashi Tetsukawa Takanori Kobayashi Ken-ichi Numachi 《Ichthyological Research》1996,43(2):117-124
Eleven populations of the rosy bitterling,Rhodeus ocellatus, from different localities in Japan, were genetically compared at 16 protein-coding loci using starch-gel electrophoresis.
Two loci,Ldh-2 andPgdh, were demonstrated as diagnostic markers for the identification of two subspecies;R. ocellatus kurumeus, which is native to Japan, andR. ocellatus ocellatus, which was introduced from China. The two subspecies were distinguished by the complete substitution of different alleles
between them. Population ofR. ocellatus kurumeus occurring in Yao City, Osaka, and in Kanzaki, Saga Prefecture were genetically closely related to each other (genetic distance:
D=0.056) but distantly so toR. ocellatus ocellatus from Saitama Prefecture (D=0.202 or 0.265). Electrophoretic analyses also elucidated the existence of hybrid populations
of the two subspecies. The populations ofR. ocellatus kurumeus in Yao City had lower genetic variability and a lower incidence of white coloration on the ventral fins than populations
of the same in Saga Prefecture. The present study strongly implies that the introduction of the foreign freshwater fishes
with subspecific differentiation, into the original range of indigenous subspecies, should be averted not to bring the genetic
pollution. 相似文献
10.
Plasmids containing a Pseudomonas sp. strain 109 extracellular lipase gene (lipL) lacking NH2-terminal sequence and a lipase modulator gene (limL) lacking the NH2-terminal hydrophobic region were constructed and expressed independently in Escherichia coli by using the T7 promoter expression vector system. Recombinant LipL (rLipL) was produced as inclusion bodies, whereas recombinant LimL (rLimL) was present as a soluble protein. During in vitro renaturation of the purified rLipL inclusion bodies after they had been dissolved in 8 M urea, addition of rLimL was essential to solubilize and modulate rLipL. The solubility and activity of rLipL were influenced by the rLimL/rLipL molar ratio; the highest level of solubility was obtained at an rLimL/rLipL ratio of 4:5, whereas the highest activity level was obtained at an rLimL/rLipL ratio of 4:1. After renaturation, rLipL and rLimL were coprecipitated with anti-rLipL antibody, indicating the formation of an rLipL-rLimL complex. Activity of the native lipase purified from Pseudomonas sp. strain 109 was also inhibited by rLimL. By Western blotting (immunoblotting) with anti-rLimL antibody, native LimL was detected in Pseudomonas cells solubilized by sarcosyl treatment. LimL was purified from Pseudomonas sp. strain 109, and the NH2-terminal amino acid sequence was determined to be NH2-Leu-Glu-Pro-Ser-Pro-Ala-Pro-. We propose that to prevent membrane degradation, LimL weakens lipase activity inside the cell, especially in the periplasm, in addition to modulating lipase folding. 相似文献