全文获取类型
收费全文 | 805697篇 |
免费 | 94781篇 |
国内免费 | 969篇 |
专业分类
901447篇 |
出版年
2018年 | 7103篇 |
2017年 | 6778篇 |
2016年 | 9986篇 |
2015年 | 14671篇 |
2014年 | 16769篇 |
2013年 | 23255篇 |
2012年 | 27105篇 |
2011年 | 27553篇 |
2010年 | 18394篇 |
2009年 | 16859篇 |
2008年 | 24215篇 |
2007年 | 25084篇 |
2006年 | 23195篇 |
2005年 | 22474篇 |
2004年 | 22309篇 |
2003年 | 20989篇 |
2002年 | 20359篇 |
2001年 | 34916篇 |
2000年 | 35047篇 |
1999年 | 28082篇 |
1998年 | 10570篇 |
1997年 | 10794篇 |
1996年 | 10344篇 |
1995年 | 9655篇 |
1994年 | 9478篇 |
1993年 | 9368篇 |
1992年 | 23072篇 |
1991年 | 22399篇 |
1990年 | 22018篇 |
1989年 | 21466篇 |
1988年 | 19542篇 |
1987年 | 18767篇 |
1986年 | 17547篇 |
1985年 | 17220篇 |
1984年 | 14531篇 |
1983年 | 12590篇 |
1982年 | 9740篇 |
1981年 | 8810篇 |
1980年 | 8208篇 |
1979年 | 13694篇 |
1978年 | 10857篇 |
1977年 | 9845篇 |
1976年 | 9176篇 |
1975年 | 10192篇 |
1974年 | 11124篇 |
1973年 | 10904篇 |
1972年 | 9793篇 |
1971年 | 9048篇 |
1970年 | 7611篇 |
1969年 | 7460篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
993.
O G Ianovski? L A Zakharova A M Vasilenko 《Biulleten' eksperimental'no? biologii i meditsiny》1990,109(1):55-57
In addition to the immunostimulating activity, bone marrow mediators, myelopeptides (MP) show the dose-dependent effect on the development of pain sensitivity in mice. When injected in nanogram amounts, MP induce hyperalgesia and 3-9 fold higher production of antibodies against SREC. When injected in milligram amounts, they exhibit hypoalgesic effect and no influence on antibody production. Immunostimulating effect in MP (mol, mass less than 1 KD, fraction 3) is accompanied with hypoalgesia. Bone marrow factors of mol. masses 40-150 KD (fraction 1) eluted at Sephadex G-25 gel-filtration before MP enhance the pain sensitivity tHreshold and show a potent immunodepressive effect. Thus the bone marrow factors are capable of exhibiting the opposite effects on the immune system in the pain control system that evidences the tight interrelation between these systems. 相似文献
994.
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
995.
E. R. R. Rochedo L. F. C. Conti H. G. Paretzke 《Radiation and environmental biophysics》1996,35(4):243-261
The structure and mathematical model of PARATI, a detailed computer programme developed for the assessment of the radiological
consequences of an accidental contamination of urban areas, is described with respect to the scenarios used for the estimation
of exposure fields in a village or town, the models for the initial and secondary contamination with the radionuclide 137Cs, the concepts for calculating the resulting radiation exposures and the changes with time of the contamination and radiation
fields. Kerma rates at various locations in tropical urban areas are given, and the contribution of different contaminated
surfaces to these rates after dry or wet deposition are discussed.
Received: 12 April 1996 / Accepted in revised form: 30 August 1996 相似文献
996.
In this study we investigated whether alpha-tocopherol can be spared by ubiquinol-3 during autoxidation of multilamellar liposome. A lipophilic azocompound, 2,2'-azobis-(2,4-dimethyl-valeronitrile), was chosen to initiate liposome autoxidation. The effect of either alpha-tocopherol, ubiquinol-3, or a mixture of them was compared. Rates of conjugated diene formation and concomitant disappearance of the two antioxidants was measured. Since the inhibition rate constant for the scavenging of peroxyl radical for alpha-tocopherol was higher than that for quinol-3, it was concluded that alpha-tocopherol is regenerated by ubiquinol-3. 相似文献
997.
998.
999.
1000.
Two cases of right lower lobe oedema are presented as a supposedly very rare sign of left heart failure after myocardial infarction in the presence of acute mitral regurgitation. Causes of unilateral oedema and its clinical relevance in the diagnostic and therapeutic perspectives are discussed, and a review of the literature on this topic is presented. 相似文献