全文获取类型
收费全文 | 2695篇 |
免费 | 147篇 |
出版年
2022年 | 8篇 |
2021年 | 24篇 |
2020年 | 20篇 |
2019年 | 29篇 |
2018年 | 39篇 |
2017年 | 29篇 |
2016年 | 42篇 |
2015年 | 73篇 |
2014年 | 103篇 |
2013年 | 188篇 |
2012年 | 134篇 |
2011年 | 159篇 |
2010年 | 88篇 |
2009年 | 87篇 |
2008年 | 129篇 |
2007年 | 139篇 |
2006年 | 141篇 |
2005年 | 123篇 |
2004年 | 120篇 |
2003年 | 142篇 |
2002年 | 119篇 |
2001年 | 79篇 |
2000年 | 94篇 |
1999年 | 75篇 |
1998年 | 46篇 |
1997年 | 45篇 |
1996年 | 32篇 |
1995年 | 27篇 |
1994年 | 26篇 |
1993年 | 21篇 |
1992年 | 44篇 |
1991年 | 41篇 |
1990年 | 34篇 |
1989年 | 33篇 |
1988年 | 21篇 |
1987年 | 21篇 |
1986年 | 30篇 |
1985年 | 30篇 |
1984年 | 14篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 15篇 |
1980年 | 9篇 |
1978年 | 17篇 |
1977年 | 17篇 |
1975年 | 19篇 |
1974年 | 11篇 |
1973年 | 16篇 |
1972年 | 10篇 |
1966年 | 8篇 |
排序方式: 共有2842条查询结果,搜索用时 31 毫秒
61.
A Sugenoya Y Yamada G Kaneko M Kobayashi M Miyakawa F Iida 《Endocrinologia japonica》1984,31(6):749-753
In vitro release of thyroid hormone was investigated under basal and TSH-stimulated conditions in the solitary autonomously functioning thyroid nodules (AFTN). A small portion (0.5 g of wet weight) of the nodules and adjacent thyroid tissues removed surgically from five patients with solitary AFTN were prepared for the dispersed cell culture. In the experiment on non TSH-stimulated (basal) conditions, those culture media which were totally replaced on the 5th day after primary culture were utilized for the determination of thyroxine (T4) and triiodothyronine (T3) by radioimmunoassay. T4 and T3 levels in culture media of the functioning nodules were 1.15 +/- 0.33 microgram/dl (mean +/- SEM) and 2.72 +/- 0.68 ng/ml, contrasted with levels of 0.67 +/- 0.09 microgram/dl and 1.24 +/- 0.22 ng/ml in the paranodular tissues. The mean ratios of T3/T4 of the nodules and paranodular tissues were 0.25 +/- 0.02 and 0.19 +/- 0.02, respectively (p less than 0.05). Meanwhile, in another experiment under TSH stimulatory conditions employing 40 and 80 microU/ml of human TSH, there were no significant differences in T4 and T3 releases when the two groups were compared. 相似文献
62.
Summary Processes in the development of intestinal metaplasia of the stomach were investigated from the morphological and histochemical approaches using light and electron microscopic techniques. The specimens taken from 38 gastric carcinomas and 15 gastric and/or duodenal ulcers were subjected to this study. Morphological appearances of the intestinal metaplasia observed in routine examination with hematoxylin and eosin staining was able to be divided into complete and incomplete metaplasia by the light and electron microscopic histochemical stainings of the mucosubstances. The columnar cells at the area of the incomplete metaplasia had both the properties of the intestinal epithelia and the gastric foveolar epithelia. The incomplete as well as the complete metaplasia arose from the generative cells at the isthmus of the gland. The generative cells, however, sometimes gradually transformed to produce the complete metaplastic cells. The two processes of the development of the intestinal metaplasia were proposed and discussed. 相似文献
63.
Two enzymatically active forms of valyl-tRNA synthetase [EC 6.1.1.9] were found in the cells of Bacillus subtilis. The aminoacylation activities of the two forms were altered during the sporulation of B. subtilis. The tRNA'S acylated by these enzymes were analyzed by methylated albumin-Kieselguhr column chromatography. 相似文献
64.
Zinc-substituted horseradish peroxidase is oxidized by K2IrCl6 to a characteristic state which retains one oxidizing equivalent more than the zinc peroxidase. The oxidized enzyme gives an optical absorption spectrum similar to that of compound I of peroxidase and catalase, and a g = 2 electron paramagnetic resonance signal which has an intensity corresponding to the porphyrin content. It is reduced back to the zinc peroxidase by a stoichiometric amount of ferrocyanide or by a large excess of K3IrCl6. From the equilibrium data, the value of E0' for the zinc peroxidase couple is estimated to be 0.74 V at pH 6. The oxidized zinc peroxidase is also formed by the addition of H2O2 or upon illumination with white light. The rate constants for the oxidation by K2IrCl6 and H2O2 at pH 8.0 are 8 x 10(5) and 8 x 10(2) M-1 s-1, respectively. No essential spectral change can be observed when K2IrCl6 is added to the metal-free peroxidase (protoporphyrin--apoperoxidase complex) or to zinc-substituted sperm whale myoglobin. 相似文献
65.
Electron paramagnetic resonance (EPR) spectra of the glycosylated minor hemoglobins A1a-1, A1a-2, A1b and A1c and the major hemoglobin A0 in the nitrosyl form have been obtained in the absence and presence of inositol hexaphosphate. In the absence of inositol hexaphosphate, nitrosyl hemoglobins A1a-1, A1a-2 and A1b exhibited a triplet hyperfine structure centered at g = 2.009 which has been shown to be diagnostic of the low affinity (T) quaternary structure. Addition of inositol hexaphosphate to nitrosyl hemoglobins A0, A1c, A1b and A1a-2 developed a triplet hyperfine structure of the EPR spectra but the magnitude of the hyperfine was decreased in the order of hemoglobins A0, A1c, A1b and A1a-2. However, inositol hexaphosphate had essentially no effect on the EPR spectrum of nitrosyl hemoglobin A1a-1. The present results account qualitatively for the oxygen binding properties of these glycosylated minor hemoglobins in the framework of a two-state allosteric model. 相似文献
66.
Summary A patient with acute lymphoblastic leukemia (ALL) whose cells had L3 (Burkitt-type) morphology was found to have a variant translocation t(2;8)(p13;q24), that has been reported only in Burkitt lymphomas. This observation provides additional evidence for a close association of particular karyotypic abnormalities with both Burkitt-type ALL and Burkitt lymphoma. 相似文献
67.
68.
A new synthesis of desmosterol was described using hyodeoxycholic acid (3,6-dihydroxy-5β-cholanic acid) as a starting material. Epidesmosterol (3-hydroxycholesta-5,24-diene) was also synthesized for the first time from the same starting material. 相似文献
69.
The generic composition of the heterotrophic bacterial population of Tokyo Bay, which is now highly polluted and eutrophic, was compared with that of the adjacent, less polluted regions of Sagami Bay and Suruga Bay. Members of Vibrionaceae predominated in the bacterial flora of seawater and zooplankton samples from Sagami Bay, Suruga Bay, and the mouth of Tokyo Bay. However,Vibrio spp. formed only a small proportion of the bacterial population of the water and sediment samples from the inner Tokyo Bay; there the Gram-negative, nonmotile, nonpigmented bacteria, which were tentatively identified asAcinetobacter, were predominant. The result of experiments, in which seawater samples from Tokyo Bay were incubated under various experimental conditions, indicated that two significant factors apparently control the growth ofVibrio spp. in seawater; (1) a direct antagonism betweenVibrios and phytoplankton undergoing rapid growth, and (2) a limiting organic nutrient forvibrios. 相似文献
70.
cis-5-Hydroxy-L-pipecolic acid was isolated and characterized from the leaves of Morus alba and the seeds of Lathyrus japonicus. The trans-form was also obtained from the former. 相似文献