全文获取类型
收费全文 | 5548篇 |
免费 | 401篇 |
国内免费 | 1篇 |
出版年
2023年 | 34篇 |
2022年 | 81篇 |
2021年 | 128篇 |
2020年 | 92篇 |
2019年 | 112篇 |
2018年 | 130篇 |
2017年 | 113篇 |
2016年 | 186篇 |
2015年 | 280篇 |
2014年 | 323篇 |
2013年 | 412篇 |
2012年 | 491篇 |
2011年 | 422篇 |
2010年 | 294篇 |
2009年 | 247篇 |
2008年 | 352篇 |
2007年 | 329篇 |
2006年 | 300篇 |
2005年 | 255篇 |
2004年 | 214篇 |
2003年 | 224篇 |
2002年 | 183篇 |
2001年 | 60篇 |
2000年 | 63篇 |
1999年 | 59篇 |
1998年 | 34篇 |
1997年 | 35篇 |
1996年 | 43篇 |
1995年 | 35篇 |
1994年 | 26篇 |
1993年 | 29篇 |
1992年 | 40篇 |
1991年 | 31篇 |
1990年 | 29篇 |
1989年 | 26篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 25篇 |
1985年 | 15篇 |
1984年 | 19篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 12篇 |
1978年 | 13篇 |
1974年 | 9篇 |
1973年 | 12篇 |
1939年 | 6篇 |
1938年 | 11篇 |
排序方式: 共有5950条查询结果,搜索用时 31 毫秒
1.
2.
R. Shainkin-Kestenbaum C. Caruso G. M. Berlyne 《Biological trace element research》1991,28(3):213-221
The effect of nickel on superoxide dismutase activity (SOD), as well as on rate of hydroxydopamine oxidation, was studied in vitro since lipid peroxidation has been implicated in cell damage by nickel, whose toxicity and carcinogenicity are well established. Nickel strongly inhibits SOD activity. The degree of inhibition is directly proportion to the nickel concentration (tested range 0.066 to 0.33 microgram/mL in the reaction mixture); to the substrate concentration (tested range 0.4 x 10 4M to 1.1 x 10 4M 6-hydroxydopamine); and to reaction mixture. Autoxidation of 6-hydroxydopamine was increased by nickel concentrations higher than 15 micrograms/mL. The combination of excessive oxygen free radical production and inhibition of their elimination by inhibition of SOD activity may contribute to the nickel toxicity that has been reported in industrial accidents, as well as to the high incidence of cancer occurring in nickel workers. It may also contribute to many complications in uremic patients, in whom increased serum nickel levels were reported to be in a similar range to those inhibiting SOD. 相似文献
3.
4.
Sequence complexity and diversity of polyadenylated RNA molecules transcribed in human myeloid cells
5.
Amy Chapman Gonzalo Gonzales Wayne R. Burrowes Paul Assanah Bernadette Iannone Michael K. Leung George B. Stefano 《Cellular and molecular neurobiology》1984,4(2):143-155
In Mytilus and Leucophaea the high-affinity binding site density is significantly lower in old animals than in young animals, whereas the low-affinity site density remains unchanged. In Mytilus the estimated met-enkephalin and met-enkephalin-Arg6-Phe7 levels are significantly higher in old than in young animals. In Leucophaea only the met-enkephalin level can be determined, and it is also higher in old animals. The decrease in the high-affinity binding site density and the corresponding increase in endogenous enkephalin levels suggest the existence of an opioid compensatory mechanism associated with the aging process. In Mytilus there is a demonstrated decrease with age in intraganglionic dopamine levels in response to applied opiates. In addition, the inhibition of dopamine-stimulated adenylate cyclase activity by opiates also decreases in older animals. In Leucophaea the sex difference in opioid binding densities diminishes with age. 相似文献
6.
7.
8.
Natural antibodies to interferon-gamma 总被引:3,自引:0,他引:3
Natural antibodies to interferon (IFN)-γ were detected in the serum of virus-infected patients and also, at a low titre, in
the serum of healthy subjects. The increased titre of antibodies to IFN-γ in the sera of virus-infected patients, and its
decrease with clinical resolution, indicate that these antibodies are related to viral infection and probably reflect IFN-γ
production as a result of antigenic stimulationin vivo. Natural antibodies to IFN-γ were affinity purified and studied for their capability to interferein vitro with the multiple activities of the lymphokine. Data obtained show that these human anti-IFN-γ antibodies have no inhibitory
effect on the antiviral and antiproliferative activity of IFN-γ and do not interfere with the binding of the lymphokine to
its specific cell receptor. Instead, they can inhibit the expression of HLA-DR antigens induced by IFN-γ on U937 cells and
interfere, in mixed lymphocyte culture, with the proliferation of lymphocytes and the generation of cytotoxic lymphocytes.
Experiments in animal models suggest that natural antibodies to IFN-γ may have a role in the immunoregulatory process limiting
the intensity and/or duration of immune response. As they can interfere only with the immunomodulating activities of IFN-γ,
these antibodies might open up new therapeutic approaches to diseases with evidence of activated cell-mediated immunity. 相似文献
9.
Cristina Cereda Emanuela Leoni Pamela Milani Orietta Pansarasa Giuliano Mazzini Stefania Guareschi Elena Alvisi Andrea Ghiroldi Luca Diamanti Stefano Bernuzzi Mauro Ceroni Emanuela Cova 《PloS one》2013,8(10)
Several lines of evidence support the hypothesis of a toxic role played by wild type SOD1 (WT-SOD1) in the pathogenesis of sporadic amyotrophic lateral sclerosis (SALS). In this study we investigated both distribution and expression profile of WT-SOD1 in leukocytes from 19 SALS patients and 17 healthy individuals. Immunofluorescence experiments by confocal microscopy showed that SOD1 accumulates in the nuclear compartment in a group of SALS subjects. These results were also confirmed by western blot carried out on soluble nuclear and cytoplasmic fractions, with increased nuclear SOD1 level (p<0.05). In addition, we observed the presence of cytoplasmic SOD1 aggregates in agreement with an increased amount of the protein recovered by the insoluble fraction. A further confirmation of the overall increased level of SOD1 has been obtained from single cells analysis using flow cytometry as cells from SALS patients showed an higher SOD1 protein content (p<0.05). These findings add further evidence to the hypothesis of an altered WT-SOD1 expression profile in peripheral blood mononuclear cells (PBMCs) from patients with ALS suggesting that WT-SOD1 species with different degrees of solubility could be involved in the pathogenesis of the disease. 相似文献
10.