全文获取类型
收费全文 | 330465篇 |
免费 | 15268篇 |
国内免费 | 861篇 |
出版年
2021年 | 1805篇 |
2018年 | 15819篇 |
2017年 | 14724篇 |
2016年 | 11778篇 |
2015年 | 3849篇 |
2014年 | 4729篇 |
2013年 | 6623篇 |
2012年 | 12162篇 |
2011年 | 22262篇 |
2010年 | 18921篇 |
2009年 | 14415篇 |
2008年 | 18452篇 |
2007年 | 20816篇 |
2006年 | 7461篇 |
2005年 | 7681篇 |
2004年 | 8066篇 |
2003年 | 8083篇 |
2002年 | 7789篇 |
2001年 | 9588篇 |
2000年 | 9239篇 |
1999年 | 7009篇 |
1998年 | 2129篇 |
1997年 | 1976篇 |
1996年 | 1841篇 |
1992年 | 5488篇 |
1991年 | 5733篇 |
1990年 | 5659篇 |
1989年 | 5640篇 |
1988年 | 5229篇 |
1987年 | 4880篇 |
1986年 | 4444篇 |
1985年 | 4677篇 |
1984年 | 3709篇 |
1983年 | 3050篇 |
1982年 | 2027篇 |
1981年 | 1722篇 |
1980年 | 1726篇 |
1979年 | 3338篇 |
1978年 | 2576篇 |
1977年 | 2376篇 |
1976年 | 2331篇 |
1975年 | 2838篇 |
1974年 | 3117篇 |
1973年 | 3085篇 |
1972年 | 3427篇 |
1971年 | 3244篇 |
1970年 | 2220篇 |
1969年 | 2158篇 |
1968年 | 2031篇 |
1967年 | 1797篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
952.
The activity of superoxide dismutase (SOD) from bovine erythrocytes was measured by the inhibition of nitrotetrazolium blue reduction rate in superoxide anion radical generation systems--xanthine/xanthine oxidase of NADH/phenazine methasulfate. The enzyme activity increases in the presence of compounds acting as electron donors in radical-involving reactions and decreased in the presence of compounds possessing the properties of electron acceptors. Activation of SOD by electron donors and its inhibition by electron acceptors was dependent on the concentration of the above compounds. In the absence of SOD electron donors and acceptors did not change the rate of tetrazolium blue reduction by superoxide anion radicals. The role of the new type of SOD regulation for the enzyme functioning in the cell is discussed. 相似文献
953.
Iodine concentration by the fungus Penicillium chrysogenum inhabiting soils of the nonchernozem zone
S V Letunova S A Alekseeva E M Korobova 《Nauchnye doklady vysshe? shkoly. Biologicheskie nauki》1986,(10):94-98
The iodine accumulation by strains of microscopic fungi Penecillium chrysogenum isolated from soddy-middle podzolic soils of Kirov region has been studied. It has been shown that fungi are able to accumulate from 5,0 X 10(-5) to 10,2% of iodine depending upon the medium iodine content and the degree of the organisms' tolerance to its high concentrations. 相似文献
954.
Eberhard Gischler 《Facies》2010,56(2):173-177
Shallow fore-reef areas worldwide are usually characterized by spurs and grooves. A comparison of examples from the three
world oceans suggests that Indo-Pacific spurs and grooves are shaped predominantly by erosion, whereas western Atlantic spur
and groove systems are largely a product of constructive processes. I propose that this difference is caused by regional differences
in Holocene sea-level change, which controlled exposure to waves and currents, and reef-accretion rates. The transgressive–regressive
sea-level curve in the Indo-Pacific realm, i.e., the Mid-to-Late Holocene sea-level fall in these areas has maintained high-energy
conditions in the shallow fore reef. Higher exposure to waves and currents favors erosion and leads to a dominance of crustose
coralline algae that have relatively slow growth rates. In the western Atlantic, the transgressive Holocene sea level has
caused Mid-to-Late Holocene deepening and has maintained accommodation space for reef accretion. Fast-growing acroporid corals
thrive under lower exposure and are more common than coralline algae. The fossil record of the spur and groove system is rather
poor, which is probably a consequence of the need of excellent, three-dimensional outcrops for identification. 相似文献
955.
T P Chernobel' T I Randmaa Z Ia Maksimova A A Shinkorenko V N Migunov 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1987,(11):88-90
A total of 218 batches of blood preparations produced from different raw materials have been studied by means of enzyme immunoassay kits (Abbott Laboratories, USA). The assays have revealed that the preparations under study are nonstandard with respect to the content and isolation rate of HBsAg, the marker of hepatitis B virus. These data necessitate search for the ways of improving the quality of blood preparations. 相似文献
956.
Identification of the functional site of erythrocyte protein 4.1 involved in spectrin-actin associations 总被引:23,自引:0,他引:23
I Correas T L Leto D W Speicher V T Marchesi 《The Journal of biological chemistry》1986,261(7):3310-3315
Peptides produced by mild chymotryptic digestion of human erythrocyte protein 4.1 mimic the ability of intact 4.1 to promote the binding of spectrin to F-actin. This complex-promoting activity was found to reside in an 8-kDa peptide which was fully functional when dissociated from other protein 4.1-derived peptides, indicating that noncovalent complexes of multiple peptides were not essential for activity. The 8-kDa peptide was incorporated into a ternary complex with spectrin and F-actin in approximately stoichiometric amounts. Amino acid composition and two-dimensional peptide mapping show that the 8-kDa active peptide is located within the 10-kDa region of protein 4.1 which contains a cAMP-dependent phosphorylated site. 相似文献
957.
958.
Peter V Scott 《BMJ (Clinical research ed.)》1982,285(6350):1277-1278
959.
E S Revazova Iu N Solov'ev T M Khizhniakova T V Iudicheva 《Biulleten' eksperimental'no? biologii i meditsiny》1985,99(4):469-471
The authors describe human cancer strains established from 6 cell lines transplanted to nude mice and rats: cancer of the liver, colon, lung, bladder and Burkitt's lymphoma. In spite of a long history (for several years) of cell line transfers in vitro, on transplantation of tumor cells, nude animals established tumors histologically identical to the primary cancer. 相似文献
960.