全文获取类型
收费全文 | 1118篇 |
免费 | 54篇 |
国内免费 | 3篇 |
出版年
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 5篇 |
2019年 | 15篇 |
2018年 | 28篇 |
2017年 | 18篇 |
2016年 | 19篇 |
2015年 | 39篇 |
2014年 | 35篇 |
2013年 | 84篇 |
2012年 | 57篇 |
2011年 | 60篇 |
2010年 | 36篇 |
2009年 | 34篇 |
2008年 | 80篇 |
2007年 | 65篇 |
2006年 | 78篇 |
2005年 | 62篇 |
2004年 | 52篇 |
2003年 | 65篇 |
2002年 | 61篇 |
2001年 | 15篇 |
2000年 | 12篇 |
1999年 | 19篇 |
1998年 | 13篇 |
1997年 | 9篇 |
1996年 | 4篇 |
1995年 | 14篇 |
1994年 | 9篇 |
1993年 | 10篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 4篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 15篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1973年 | 2篇 |
1969年 | 3篇 |
排序方式: 共有1175条查询结果,搜索用时 15 毫秒
11.
Isao Matsui Masaharu Kamei Shuzo Otani Seiji Morisawa Anthony E. Pegg 《Biochemical and biophysical research communications》1982,106(4):1155-1160
Spermidine acetylase activity was detected in extracts prepared from and there was a marked increase in activity over the early period of growth. This increase reached a maximum 3 h after inoculation and was followed by an increase in ornithine decarboxylase activity. The acetylase was also able to use spermine as a substrate, but not putrescine. With spermidine and acetyl-CoA as substrate, the product formed was exclusively N1-acetyl-spermidine. This is the first evidence for the occurrence in bacteria of spermidine-N1-acetyltransferase, an enzyme which has previously been described in mammalian cells. These results suggest that acetylation of spermidine may be involved in the growth of and in the regulation of its polyamine content. 相似文献
12.
Organizers of the Sixth International Symposium on the Biology of the Turbellaria 相似文献
13.
Polycelis (Seidlia) auriculata is endemic to mountain districts of Japan, from the central part of Honshû to the area of the Daisetsu Mts of Hokkaidô. In northern Japan, it sometimes occurs in cold-water biotopes of lowland areas. The progenitor of P. auriculata appears to have been the oldest immigrant into northern Japan among the Japanese Polycelis species, entering through a northern route as a preglacial faunal element. P. auriculata now shows a discontinious distribution in northern Japan. By virtue of its geographical and vertical distribution, ecological niche, variation in anatomy of the copulatory apparatus, and cytodemes, this species appears to be in the process of transformation. 相似文献
14.
We have employed a new scale for characterizing chromosomal forms in the karyotypes of four species of Bipalium from five localities in Japan. Specimens of Bipalium nobile Kawakatsu et Makino, 1982, from Yokohama had a diploid chromosome number of 2x = 10 (2m + 2sm + 2sm + st & sm + 2sm); specimens of the same species from Toyonaka had this number as well but with slightly different chromosomal form (2m + 2sm + sm & st + 2st + m & sm). An undescribed species from Sanjô, Bipalium sp. 2, with two dorsal stripes and a yellow head crescent, had 2x = 10 (2m + 2sm + 2sm + 2sm + 2m); and another undescribed species from Chichijima Island, Bipalium sp. 3, with five dorsal stripes, had 2x = 10 (2m + 2sm + 2sm + 2sm + 2m). A non-sexual bipaliid tentatively identified as Bipalium kewense Moseley, 1878, from Chichijima Island had 2x = 18 (2m + 2m + 2m + 2sm + 2st + 2sm + 2sm + 2sm + 2sm). 相似文献
15.
Takashi Iwamoto Masahide Takahashi Masaharu Ohbayashi Izumi Nakashima 《Experimental cell research》1992,200(2)
We recently reported the establishment of transgenic mouse lines carrying the mouse metallothionein/ret fusion gene in which severe melanosis and melanocytic tumors developed. In the present study, we demonstrate that a significant number of pigmented hairs developed in Wv/Wv mice crossed to one of the transgenic mouse lines. The pigmented hair of Wv/Wv mice carrying the ret oncogene did not lose color during aging and reappeared after shaving, indicating that the melanocytes in the hair follicle function. The melanocytic tumors also developed in these mice, although the incidence was lower than that in the wild transgenic mice. Furthermore, the neural tube culture of mouse embryos indicated that neural crest cells of the transgenic mice gave rise to a cell population that autonomously produced melanin even in the absence of melanocyte stimulating hormone. These results strongly suggested that the introduced ret oncogene could compensate for the defect of c-kit in Wv mice during both embryogenesis and postnatal life and induce a high level of melanin synthesis in the process of melanocyte development. 相似文献
16.
Sachio Hayashi Masaharu Nonoguchi Yoshihiko Shimokawa Mikihiko Tubouchi Yoshiyuki Takasaki Kiyohisa Imada 《Journal of industrial microbiology & biotechnology》1992,9(2):145-147
Summary Two extracellular -fructofuranosidases (E-1 andE-2) fromAureobasidium sp. ATCC 20524, producing 1-kestose (1F--fructofuranosyl-sucrose) from sucrose, were purified to homogeneity. Molecular weights of the enzymes were estimated to be about 304000 (E-1) and 315000 (E-2) Da by gel filtration. The enzymes contained 33% (w/w) (E-1) and 27% (w/w) (E-2) carbohydrate. TheK
m values for sucrose ofE-1 andE-2 andE-2 were 0.34 and 0.28 M, respectively. were 0.34 and 0.28 M, respectively. The enzymatic profiles of these enzymes were almost identical to intracellular enzymesP-1 andP-2 except for the differences in carbohydrate content andK
m values ofE-2 andP-2. 相似文献
17.
M Takigawa Y Nishida F Suzuki J Kishi K Yamashita T Hayakawa 《Biochemical and biophysical research communications》1990,171(3):1264-1271
Treatment of yolk-sac membranes of 4-day-old chick embryos with spermine or spermidine resulted in angiogenesis in the membranes. The angiogenic activity of spermine was stronger than that of spermidine. Putrescine, polylysine and histamine did not induce angiogenesis in the membranes. Administration of putrescine, spermidine and spermine increased their respective levels in yolk-sac membranes, but no interconversion of these amines was observed. The increases in spermidine and spermine levels in yolk-sac membranes preceded induction of angiogenesis. The angiogenesis induced by spermine was inhibited by tissue inhibitors of metalloproteinases, that is, TIMP and TIMP-2. These findings suggest that spermine and spermidine are angiogenesis factors in yolk-sac membranes of chick embryos and that matrix metalloproteinases represented by collagenase are involved in their action. 相似文献
18.
The enzyme activity of dephosphorylation of thymidine triphosphate was found in microsomal fraction of rat liver. The enzyme activity decreased at the time when [3H]thymidine incorporation into DNA of regenerating liver increased. When the [3H]thymidine incorporation was suppressed by 1,3-diaminopropane, the enzyme activity remained elevated. These results suggest that the enzyme activity appears to be closely linked to DNA synthesis. 相似文献
19.
Masaharu Konishi Yoshio Mori Kentaro Hirai 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1982,229(2)
A gas—liquid chromatographic method for the simultaneous determination of triazolobenzophenone [2′,5-dichloro-2-(3-glycylaminomethyl-5-methyl-4H-1,2,4-triazol-4-yl)-benzophenone, TB] and its major blood metabolite, triazolam, 8-chloro-6-(o-chlorophenyl)-1-methyl-4H-s-triazolo[4,3-a][1,4]benzodiazepine (TZ), in monkey plasma was developed. Decomposition of TB was observed during gas—liquid chromatography. In alkaline medium, TB in plasma was submitted to ring closure reaction to yield triazolo-aminoquinoline, [4-amino-7-chloro-5-(2-chlorophenyl)-1-methyl-4H-s-triazolo[4,3-a]quinoline (TAQ), while TZ remained unaffected, and TAQ and TZ in the benzene extract were assayed by gas—liquid chromatography using an electron-capture detector. The concentration ranges studied were from 5 to 40 ng of TB per 0.5 ml of plasma and from 2 to 20 ng of TZ per 0.5 ml of plasma. This method could be applied to the determination of the plasma levels of TB and TZ in monkeys following intravenous administration of a single 0.2 mg/kg dose of TB. 相似文献
20.
Yoshinori Asakawa Masao Toyota Masaharu Uemoto Takaaki Aratani 《Phytochemistry》1976,15(12):1929-1931
The distribution in six Porella species of drimane-, aromadendrane- and pinguisane-type sesquiterpenes and norsesquiterpenes is described. The sharp pungent substance of P. gracillissima, P. fauriei and P. macroloba is (+)-tadeonal. 相似文献