全文获取类型
收费全文 | 10027篇 |
免费 | 824篇 |
国内免费 | 5篇 |
专业分类
10856篇 |
出版年
2022年 | 47篇 |
2021年 | 98篇 |
2020年 | 56篇 |
2019年 | 82篇 |
2018年 | 120篇 |
2017年 | 111篇 |
2016年 | 155篇 |
2015年 | 230篇 |
2014年 | 288篇 |
2013年 | 538篇 |
2012年 | 482篇 |
2011年 | 488篇 |
2010年 | 294篇 |
2009年 | 290篇 |
2008年 | 469篇 |
2007年 | 498篇 |
2006年 | 456篇 |
2005年 | 490篇 |
2004年 | 447篇 |
2003年 | 440篇 |
2002年 | 430篇 |
2001年 | 337篇 |
2000年 | 380篇 |
1999年 | 347篇 |
1998年 | 126篇 |
1997年 | 105篇 |
1996年 | 104篇 |
1995年 | 105篇 |
1994年 | 91篇 |
1993年 | 115篇 |
1992年 | 279篇 |
1991年 | 192篇 |
1990年 | 205篇 |
1989年 | 204篇 |
1988年 | 306篇 |
1987年 | 180篇 |
1986年 | 154篇 |
1985年 | 135篇 |
1984年 | 104篇 |
1983年 | 93篇 |
1982年 | 60篇 |
1981年 | 62篇 |
1979年 | 80篇 |
1978年 | 60篇 |
1977年 | 38篇 |
1976年 | 43篇 |
1975年 | 45篇 |
1974年 | 57篇 |
1973年 | 44篇 |
1972年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
81.
Hisao Matsui Mayumi Kasao Susumu Imamura 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1978,145(2):231-236
A method is described for the determination of urinary hippuric acid by high-performance liquid chromatography. The method used ethyl acetate extraction for partial clean-up of the urine. The separation was carried out on a reversed-phase column using 20% methanol in 0.01 M aqueous potassium phosphate containing 0.5% acetic acid as a mobile phase. The column effluent was monitored with a UV detector at 254 nm. Hippuric acid was separated from other normal urine constituents in less than 10 min. Metabolites of xylene and styrene did not interfere with the assay. Analytical recoveries from urine were excellent and peak height and concentration were linearly related. 相似文献
82.
83.
84.
A procedure for the purification of aldehyde dehydrogenase from bakers' yeast (Saccharomyces cerevisiae) is reported. Treatment with acid, heat and organic solvents was avoided and chromatographic and filtration techniques in the presence of phenylmethylsulfonylfluoride were mainly used. An affinity chromatography step using the reactive dye Cibacron blue F3G-A, which was covalently bound to Sepharose 4B, was found to be essential. The enzyme was bound to and then released from the dye. The purified enzyme was shown to be homogeneous by gel filtration, disc electrophoresis and SDS electrophoresis. The molecular weight of the purified enzyme determined by gel filtration was 170,000, which agreed with that of the enzyme in the crude extract. The enzyme was composed of subunits of a molecular weight of 57,000. The specific activity of the enzyme was 20 units per mg of protein under the standard assay conditions. The substrate specificity, the relative maximal velocity, the michaelis constants, the pH optimum, the stability and the activation energy of the enzyme are reported. 相似文献
85.
Two different peptides containing an aspartyl residue reactive with 1, 2-epoxy-3-(p-nitrophenoxy)propane (EPNP) in the acid protease from Rhizopus chinensis were isolated from a peptic digest of the EPNP-modified enzyme. One of the peptides was sequenced as Asp-Thr-Gly-Ser-Asp. The amino acid sequence had very high homology with those around the EPNP-reactive aspartyl residues in rennin (chymosin) [EC 3.4.23.4] and pepsin [EC 3.4.23.1]. The other peptide contained no methionine residue and gave the sequence: Asp-Thr-Gly-Thr-Thr-Leu. The N-terminal aspartyl residue of each peptide was deduced to be the EPNP-reactive site. 相似文献
86.
Satoshi Nakamura Kunimasa Koga 《Biochemical and biophysical research communications》1977,78(2):806-810
By the method of differential scanning calorimetry, it was found that thermal stability of glucose oxidase was dependent on its redox states. The oxidized form showed an apparent denaturation temperature at 76°C and the denaturation enthalpy was approximately 865 kcal/mol. On reduction of the enzyme, the denaturation temperature increased by about 10°, but no significant change was seen in the denaturation enthalpy. The activation energies of the denaturation of the oxidized and the reduced enzymes were about 89 and 103 kcal/mol, respectively. These results may imply conformational changes in the catalytic turnover of this enzyme. 相似文献
87.
88.
The analgesic actions of some synthetically prepared peptides having the Tyr-D-Arg unit at the N terminal portion of met- and leu-enkephalin were measured by the intra-cisternal injection method in mice. Among them, Tyr-D-Arg-Gly-Phe (DR-4) induced the most potent naloxone-reversible analgesia and was also effective by s.c. injection. DR-4 showed the good affinity to mu-receptor, and the resistance to the enzymatic degradation. 相似文献
89.
The crystal structure of the complex of subtilisin BPN′ (EC 3.4.21.14) with its protein inhibitor (Streptomyces subtilisin inhibitor) was solved at 4.3 Å resolution, thus establishing the following. (1) Two subtilisin BPN′ molecules (2E) associate with one dimeric inhibitor molecule (I2) to form the complex molecule E2I2. (2) The conformation of neither the inhibitor nor subtilisin BPN′ undergoes any detectable change at this resolution upon complex formation. (3) The inhibitor binds to subtilisin to form an antiparallel β-sheet, as in the case of trypsin/ trypsin inhibitor complexes. (4) The scissible bond of the inhibitor is between Met73′ and Val74′, as proposed earlier (Ikenaka et al., 1974). (5) The protein inhibitor and the substrates bind to subtilisin BPN′ in essentially the same way. 相似文献
90.
Incidence of Salmonellae in animal feed ingredients in Japan 总被引:1,自引:0,他引:1