全文获取类型
收费全文 | 3095篇 |
免费 | 172篇 |
出版年
2023年 | 14篇 |
2022年 | 17篇 |
2021年 | 62篇 |
2020年 | 45篇 |
2019年 | 50篇 |
2018年 | 69篇 |
2017年 | 67篇 |
2016年 | 99篇 |
2015年 | 139篇 |
2014年 | 154篇 |
2013年 | 236篇 |
2012年 | 262篇 |
2011年 | 257篇 |
2010年 | 172篇 |
2009年 | 142篇 |
2008年 | 247篇 |
2007年 | 208篇 |
2006年 | 222篇 |
2005年 | 197篇 |
2004年 | 163篇 |
2003年 | 156篇 |
2002年 | 112篇 |
2001年 | 10篇 |
2000年 | 10篇 |
1999年 | 23篇 |
1998年 | 10篇 |
1997年 | 19篇 |
1996年 | 17篇 |
1995年 | 13篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 5篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1972年 | 1篇 |
1961年 | 3篇 |
1960年 | 1篇 |
排序方式: 共有3267条查询结果,搜索用时 738 毫秒
81.
One molecular species of prothoracicotropic hormone with a molecular weight of about 22, 000 (22K-PTTH) of the silkworm, Bombyx mori, was isolated from 5 × 105 adult heads. The purification procedure consisted of 16 steps including defatting, salt-extraction, fractional precipitations, conventional column chromatographies, and high performance liquid chromatographies. An approximately 5 × 106-fold purification was attained to yield 5.4 μg (0.25 nmol) of the pure hormone with a recovery of 3.3%. Injection of 0.11 ng of the purified 22K-PTTH could elicit adult development in a brainless Bombyx pupa. 22K-PTTH is a basic protein (pI 7.7 ~ 8.7) containing disulfide bond(s). The amino-terminal amino acid sequence of 22K-PTTH was determined to be Gly-Asn-Ile-Gln-Val-Glu-Asn-Gln-Ile-Pro-Asp-Pro-. 相似文献
82.
83.
Hajimu Morioka Misako Takezawa Hiroshiro Shibai 《Bioscience, biotechnology, and biochemistry》2013,77(10):2835-2842
The cell differentiation system of Friend leukemia cells was applied to screening for new types of antitumor antibiotics. F5-5, Friend leukemia cells, were the most suitable for the assay system due to the stability of their response on repeated culture passages. Antibiotics like mitomycin C, adriamycin and actinomycin D, but not cycloheximide, did not induce detectable benzidine-positive cells among the F5-5 cells in the concentration ranges tested. Among the culture fluids of one thousand and fifty-one streptomycete strains subjected to the assay system, actinomycin V, FL-518 and FL-657 were found to be the most active as inducers. Actinomycin V possessing l-4-ketoproline as a substitute for l-proline of actinomycin D at a concentration of 1.0ng/ml caused 39.7% of the F5-5 cells to become benzidine-positive. Furthermore, actinomycin V inhibited the colony formation of F5-5 cells in the soft agar medium at a concentration of 0.004 ng/ml. 相似文献
84.
Takashi Matsumoto Daisuke Yoshida Shigenobu Mizusaki Hideo Tomita Koichi Koshimizu 《Bioscience, biotechnology, and biochemistry》2013,77(4):861-864
The mutagenic activities of quinoline, isoquinoline, phenanthridine, benzo(f)quinoline, benzo(h)quinoline and their α-amino derivatives were compared in relation to the effect of structural changes using the Salmonella typhimurium test system. All mutagenic compounds tested require the liver microsomal fraction for their mutagenic activity. Phenanthridine, two benzoquinolines and quinoline were mutagenic. α-Amination of two benzoquinolines and quinoline resulted to increase their mutagenic activity intensively. Addition of a benzene ring to the benzene moiety of 2-aminoquinoline, so that two carbon atoms are shared, affected distinctly the increase in the mutagenic activity. The co-existence of benzoquinoline series with 2-aminobenzo(f)quinoline showed the clear synergistic action. 相似文献
85.
Atsuko Kushi Akira Koiwai Daisuke Yoshida Fujio Gotō 《Bioscience, biotechnology, and biochemistry》2013,77(10):2513-2515
Mass spectra of N-trifluoroacetyl n-butyl ester (BTFA) of ornithinoalanine (OAL) and lanthionine (LAN) were compared with those of the BTFA derivatives of lysinoalanine (LAL) and the related amino acids. A difference of m/z 14, corresponding to one methylene group, was found in each pair of characteristic fragments between BTFA-OAL and BTFA-LAL. A temperature-programmed gas-liquid chromatography and gas chromatography-mass spectrometry were developed to analyze BTFA-LAN, BTFA-OAL and BTFA-LAL. More LAL and LAN were formed in α-lactalbumin than lysozyme by high-temperature treatment in water. OAL was detected in lysozyme treated at 100° and 120°C in alkali solution, but not in α-lactalbumin. 相似文献
86.
Daisuke Tsuru Heizo Kira Takehiko Yamamoto Juichiro Fukumoto 《Bioscience, biotechnology, and biochemistry》2013,77(9):856-862
The neutral protease of Bacillus amylosacchariticus was inactivated by low concentrations of several metal-chelating agents and the inactivated enzyme with EDTA restored its activity almost completely by the addition of Zn++ or Co++ and partially by Fe++ or Mn++, if these metal ions were added shortly after the EDTA-treatment. The native enzyme was found to contain 0.19% of zinc together with a significant amount of calcium. Parallel increase in specific activity and zinc content of enzyme preparation was observed throughout the purification procedure. The elution pattern of enzyme activity on a CM-cellulose column chromatography also completely coincided with that of protein-bound zinc. A zinc-free inactive enzyme was also reactivated by the addition of zinc or cobalt ions, clearly showing that the neutral protease of B. amylosacchariticus is a zinc mctalloenzyme. 相似文献
87.
Yoshimoto Tadashi Nakanishi Toshihiro Fukumoto Juichiro Tsuru Daisuke 《Bioscience, biotechnology, and biochemistry》2013,77(11):1775-1782
About 100 soil samples were subjected to screening for microorganisms which were capable of producing lytic enzyme toward Staphylococcus aureus. A strain belonging to Streptomyces was isolated and found to produce lytic enzyme(s) noninduciblly, when grown aerobically at 37°C for 25 hr in a medium containing 7.5% soybean cake extract, 2% dextrin, 0.6% K2HPO4, 0.02% each of MgSO4·7H2O and KCl, pH 7.0. The crude enzyme preparation was active at pH values of 8.5 and 5.8 toward S. aureus, B. subtilis, L. bulgaricus and Str. faecalis but was completely inert against M. lysodeikticus, indicating the enzyme(s) to be distinguished from other bacteriolytic enzymes of Streptomyces so far reported. 相似文献
88.
Daisuke Tsuru Heizo Kira Takehiko Yamamoto Juichiro Fukumoto 《Bioscience, biotechnology, and biochemistry》2013,77(3):330-335
Some physicochemical properties and amino acid composition of the alkaline protease of B. amylosacchariticus were determined. The molecular weight and sedimentation coefficient were estimated to be 22,700 and 2.89 s, respectively, and the amino terminal amino acid was identified to be alanine. The enzyme contained 15.9% of nitrogen and was composed of 220 residues of amino acid: lys6, his5, arg3, asp20, thr14, ser37, glu12, pro10, gly25 ala27 val20, met3, isoleu12, leu12, tyr9, phe2, try3 and amide ammonia16 The results indicate that protein nature and chemical properties of the alkaline protease presented here are distinct from those of alkaline proteases obtained from the other strains of B. subtilis, such as subtilopeptidase A, B and BPN’ 相似文献
89.
An arylamidase was purified from Flavobacterium meningosepticum by a series of chromatographies on CM-cellulose, DEAE-Sephadex A-50 and Sephadex G-150. The purified enzyme appeared homogeneous on SDS-gel electrophoresis. The molecular weight of the enzyme was estimated to be more than 500,000 dalton by using a column of Sepharose 4B and to be 62,000 when checked by SDS-gel electrophoresis. The enzyme was most active at pH 7.5 toward Leu-β-naphthylamide (Leu-β-NA). It catalyzed the hydrolysis of not only various amino acid-β-naphthylamides but also some peptides, but the hydrolysis rate of the latter substrates was quite low. Cys-di-β-naphthylamide was split by this enzyme at an optimal pH of 6.2. Incubation of oxytocin with the enzyme resulted in a decrease in the biological activity, indicating that this arylamidase possesses an oxytocinase (cystyl aminopeptidase)-like activity. 相似文献
90.
Tsuru Daisuke Hiraoka Nobutsugu Hirose Tsuneyo Fukumoto Juichiro 《Bioscience, biotechnology, and biochemistry》2013,77(11):1727-1732
Nine strains capable of producing dextranase were isolated from soil. Among them, a strain belonging to the genus Aspergillus was chosen as the best producer of the enzyme. The mold produced greater amounts of dextranase than those found in some strains in the genus Penicillium, when grown aerobically at 28°C for 5 to 6 days in medium containing 1% dextran, 1% NaNO3 or polypeptone, 0.2% yeast extracts, 0.4% K2HPO4 and small amounts of inorganic salts, pH 8.5. From the comparative taxonomic experiments, the mold used here was identified to be a strain belonging to Aspergillus carneus. 相似文献