全文获取类型
收费全文 | 435868篇 |
免费 | 48691篇 |
国内免费 | 548篇 |
专业分类
485107篇 |
出版年
2018年 | 4217篇 |
2016年 | 5636篇 |
2015年 | 7453篇 |
2014年 | 8748篇 |
2013年 | 11978篇 |
2012年 | 13646篇 |
2011年 | 13997篇 |
2010年 | 9554篇 |
2009年 | 8809篇 |
2008年 | 12669篇 |
2007年 | 13152篇 |
2006年 | 12327篇 |
2005年 | 11744篇 |
2004年 | 11753篇 |
2003年 | 11049篇 |
2002年 | 10804篇 |
2001年 | 17685篇 |
2000年 | 17682篇 |
1999年 | 14122篇 |
1998年 | 5128篇 |
1997年 | 5355篇 |
1996年 | 4976篇 |
1995年 | 4666篇 |
1994年 | 4563篇 |
1993年 | 4583篇 |
1992年 | 11741篇 |
1991年 | 11648篇 |
1990年 | 11395篇 |
1989年 | 11019篇 |
1988年 | 10573篇 |
1987年 | 10162篇 |
1986年 | 9446篇 |
1985年 | 9309篇 |
1984年 | 7803篇 |
1983年 | 6763篇 |
1982年 | 5203篇 |
1981年 | 4651篇 |
1980年 | 4494篇 |
1979年 | 7468篇 |
1978年 | 5888篇 |
1977年 | 5461篇 |
1976年 | 5247篇 |
1975年 | 5634篇 |
1974年 | 6351篇 |
1973年 | 6201篇 |
1972年 | 5782篇 |
1971年 | 5257篇 |
1970年 | 4651篇 |
1969年 | 4609篇 |
1968年 | 4451篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
911.
912.
913.
914.
A methanogenic enrichment culture decomposed small concentrations of (14)C-benzoate to (14)C(4) and (14)CO(2) under stringently anaerobic conditions with or without preceding exposure to benzoate. 相似文献
915.
916.
917.
918.
A previous experiment (Herzfeld & Taub, 1977) demonstrated that slide projections and explicit suggestions relating to thermal experiences can significantly augment temperature self-regulations training (.5 degrees F, p less than .05). however, the experimental design was thought to result in an underestimate of the magnitude of the effect, since each subject served as his own control and could therefore make use on nonsuggestion training days of material provided on training days. In this experiment, separate groups of subjects either were given feedback combined with the suggestion procedure on each of 8 training days or were given feedback alone. The mean temperature self-regulation of the suggestion group (2.01 degrees F) was significantly better than the self-regulation (.73) of the nonsuggestion group (t test, p less than 0.01), a difference of 1.28 degrees F. 相似文献
919.
Platinum(II) binding to metallothioneins 总被引:1,自引:0,他引:1
The reaction of equine renal metallothionein (MT) with excess K2PtCl4 at pH 2 results in a polymeric adduct containing 17 +/- 2 mol Pt/mol MT. A monomeric adduct containing 7 mol Pt/mol MT is obtained at neutral pH. Rates of reaction of Pt7MT with DTNB and iodoacetic acid are consistent with Pt2+ to cysteine thiolate coordination, and the extent of reaction in both cases is 11 +/- 2 mol cys/mol MT. Adducts from the reaction of K2PtCl4 with apoMT chemically modified at the N-terminal methionine residue, Cd7MT, and native MT are also reported. A structural model of Pt7MT is proposed in which the square planar tetrathiolate Pt(II) unit is incorporated into a three-metal beta cluster. Implications for the metabolism of platinum anticancer drugs are discussed. 相似文献
920.
Recent data have demonstrated that differences in sIg density on B lymphocytes distinguish functionally distinct subpopulations of these cells. Other reports suggest that cyropreservation may change the frequency of sIg-bearing lymphocytes. To determine if cryopreservation alters either the frequency of sIg cells or the distribution of sIg density, PBM from normals and patients with CLL and LCL were analyzed using the FACS. Aliquots of Ficoll-Hypaque-separated PBM were controlled-rate frozen (1 °C/min) in 7.5% Me2SO in RPMI 1640 and thawed in a 37 °C water bath on the same day. Fresh and frozen-thawed PBM aliquots were labeled with fluorescein conjugates of F(ab′) fragments of affinity chromatography-purified anti-Fab or class-specific anti-μ, anti-δ, anti-γ, or anti-α. Histograms of relative cell fluorescence, reflecting sIg density, were prepared for each aliquot with the FACS. The frequency of sIg-bearing PBM labeled with each reagent was not significantly altered by freezing. Likewise, FACS profiles demonstrated that the distribution of sIg density on normal and CLL PBM was unchanged after freezing. However, the fluorescence peak produced by frozen-thawed unlabeled cells was occasionally slightly broader than that of fresh cells, suggesting increased autofluorescence induced by freezing. These data indicate that frozen cell preparations may be utilized for the study of B-lymphocyte subsets as determined by sIg density. 相似文献