全文获取类型
收费全文 | 2327篇 |
免费 | 122篇 |
国内免费 | 1篇 |
出版年
2022年 | 13篇 |
2021年 | 30篇 |
2020年 | 13篇 |
2019年 | 15篇 |
2018年 | 26篇 |
2017年 | 20篇 |
2016年 | 34篇 |
2015年 | 58篇 |
2014年 | 78篇 |
2013年 | 189篇 |
2012年 | 104篇 |
2011年 | 107篇 |
2010年 | 53篇 |
2009年 | 64篇 |
2008年 | 117篇 |
2007年 | 116篇 |
2006年 | 100篇 |
2005年 | 95篇 |
2004年 | 96篇 |
2003年 | 114篇 |
2002年 | 87篇 |
2001年 | 63篇 |
2000年 | 79篇 |
1999年 | 71篇 |
1998年 | 30篇 |
1997年 | 22篇 |
1996年 | 19篇 |
1995年 | 21篇 |
1994年 | 16篇 |
1993年 | 22篇 |
1992年 | 47篇 |
1991年 | 45篇 |
1990年 | 49篇 |
1989年 | 60篇 |
1988年 | 38篇 |
1987年 | 44篇 |
1986年 | 27篇 |
1985年 | 31篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 22篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 22篇 |
1978年 | 17篇 |
1977年 | 24篇 |
1976年 | 17篇 |
1975年 | 15篇 |
1974年 | 9篇 |
1971年 | 9篇 |
排序方式: 共有2450条查询结果,搜索用时 15 毫秒
71.
Two new isomeric coumarins were isolated from leaves of Boenninghausenia albiflora Reichb. Their structures were elucidated as (E)-7-hydroxy-6-(3-hydroxy-3-methyl-1-butenyl)-2(H)-1-benzpyran-2-one and (Z)-7-hydorxy-6-(3-hydroxy-3-methyl-1-butenyl)-2(H)-1-benzopyran-2-one. 相似文献
72.
Ubiquinone (UQ) formation in BY-2 tobacco cells was especially promoted by a high concentration of 2,4-D. 2,4,5-T, MCP and NAA also promoted UQ formation in these cells. The UQ content in the cells cultured at high concentrations of 2,4-D was higher than that of controls throughout the culture period. The addition of 2,4-D at an early period in cell growth was very effective in promoting UQ formation, but addition at the stationary phase was ineffective. Cell growth was improved by adding phosphate to the medium but UQ content was decreased. UQ content decreased slowly during subculturing, whereas cell growth recovered gradually. 相似文献
73.
Sei-itsu Murota Midori Abe Katsuhiro Otsuka Wen-Chang Chang 《Prostaglandins & other lipid mediators》1977,13(4):711-717
Early effects of various prostaglandins on the production of hexosamine-containing substances by cultured fibroblasts, which were derived from a rat carrageenin granuloma, were studied. At the stationary phase, the cells were exposed for 6 h to one of the prostaglandin A1 (PGA1), A2, B1, B2, D2, F1α, F2α, E1, E2 or arachidonic acid in various concentrations ranging from 0.01 to 10 μg/ml for all the stimuli and from 10 pg to 10 μg/ml for PGF2α. The activity of the cells in incorporating 3H-glucosamine into hexosamine-containing substances (acidic) glycosaminoglycans and glycoproteins) during this period was compared with that of control cells. All the stimuli tested showed more or less stimulative effect on the synthesis of hexosamine-containing substances at their specific concentrations. PGF2α was found to be the most potent stimulant and its stimulative effect was found significant even at the low concentration of 100 pg/ml. PGD2, F1α and E2 were the next potent stimuli. Their optimum dose were around 1 μg/ml but they still had significant stimulation at the concentration of 0.01 μg/ml. Effect of PGE2 was rather mild. Stimulation by PGA1, A2, B1 and B2 or arachidonic acid was seen at high dose, and its seemed to be non-specific. The results suggested that these prostaglandins such as PGF2α, D2, F1α and E2 play some important role on regulating the production of intercellular ground substances. 相似文献
74.
The effect of PGF2α on the synthesis of hexosamine-containing substances (acidic glycosaminoglycans and glycoproteins) was studied in cultured fibroblasts derived from a rat carrageenin granuloma. Treatment with PGF2α ranging from 0.01 μg/ml to 20 μg/ml resulted in a significant increase of the production of these macromolecules by the cells. The stimulatory effect was found significant even at the low concentration of 10 ng/ml, and could be seen as early as 3h after exposure to PGF2α. The hexosamine-containing substances increased by PGF2α revealed that 80% of the increase was due to acidic glycosaminoglycans and the rest was due to glycoproteins. 相似文献
75.
Midori Hiramatsu 《Neurochemical research》1983,8(9):1163-1175
Inbred E1 mice are highly susceptible to convulsive seizures upon “throwing” stimulation. The strain is known to have an abnormal 5-hydroxytryptamine (5-HT) metabolism. In the study here 5-HT level, [14C]5-hydroxytryptophan (5-HTP) metabolism, MAO activity and [3H]5-HT receptor binding were examined in the cortex, brainstem and cerebellum. In the interictal period cortical and brainstem 5-HT level and [3H]5-HT receptor binding were significantly lower. In the same period cortical biosynthesized [14C]5-HT from [14C]5-HTP taken up was higher, and MAO activity was not changed.L-DOPA with MK486 induced a low threshold of seizures and decreased cortical 5-HT level. Abnormally functioning 5-HT neurones may exist in the E1 mouse cortex. 相似文献
76.
77.
1. A peptide which enhances ureogenesis in primary cultured hepatocytes of rats was isolated from a tryptic digest of bovine beta-casein. 2. The structure of the peptide was Ala-Val-Pro-Tyr-Pro-Gln-Arg which is located from 177th to 183rd residues from N-terminal of beta-casein. 3. The peptide also showed the activity to inhibit protein synthesis and protein degradation. 4. It also inhibited DNA synthesis of hepatocytes induced by insulin and/or epidermal growth factor. 相似文献
78.
Constitutive expression of FosB and its short form, FosB/SF, induces malignant cell transformation in rat-1A cells 总被引:7,自引:0,他引:7
K Kovary C A Rizzo R P Ryseck T Noguchi C Raynoschek J M Pelosin R Bravo 《The New biologist》1991,3(9):870-879
We have established Rat-1A cell lines constitutively expressing c-Fos and the two products of the fosB gene, FosB and its short form, FosB/SF. The expressed proteins in the different stable transfectants have been characterized by immunofluorescence and immunoprecipitation analysis. Our results demonstrate that constitutive expression of FosB, like the constitutive expression of c-Fos and, to a lesser extent, FosB/SF, results in cells that grow to increased saturation densities and have the ability to grow in an anchorage-independent manner. Most important is the finding that expression of these proteins augments the tumorigenic potential of Rat-1A cells. These results show that both forms of FosB have a stimulatory effect on cell proliferation. 相似文献
79.
We recently reported that by postnatal day 40 the activity of sn-glycerol-3-phosphate dehydrogenase (GPDH) was significantly depressed in the cerebellum of genetic-hypothyroid mutant mice. This mutant mouse-GPDH combination was used in the present study to define the critical time period during which thyroid hormone (T4) and growth hormone (GH) are essential for maturation of Bergmann glial cells. Our findings are that (a) induction of GPDH activity in the Bergmann glial cell is dependent on T4, (b) T4 is most effective when administered during the second 20 days of postnatal life, (c) the effect of GH on GPDH activity is complementary to or synergistic with that of T4, and (d) Bergmann glial cells and radial glial fibers of the mutant mice contain immunoreactive GPDH following various hormonal treatments. These results suggest that T4 is indispensable for the maturation of Bergmann glial cells. 相似文献
80.
Mouse Offspring Derived from Fetal Ovaries or Reaggregates Which were Cultured and Transplanted into Adult Females 总被引:5,自引:3,他引:2
Koichiro Hashimoto Motoko Noguchi Norio Nakatsuji 《Development, growth & differentiation》1992,34(2):233-238
Primordial germ cells (PGCs) and gonia could be promising novel targets and vehicles for manipulation of the mammalian germ line. To make such manipulation a practical possibility, PGCs or gonia must be allowed to produce gametes and offspring after they were isolated from embryos and manipulated in culture. As the first step to develop such research strategy, we obtained offspring from mouse oogonia which were isolated from embryonic ovaries and cultured as dispersed cells before transplantation into female mice as reaggregates. 相似文献