全文获取类型
收费全文 | 2852篇 |
免费 | 162篇 |
国内免费 | 4篇 |
出版年
2023年 | 9篇 |
2022年 | 34篇 |
2021年 | 36篇 |
2020年 | 30篇 |
2019年 | 47篇 |
2018年 | 70篇 |
2017年 | 46篇 |
2016年 | 78篇 |
2015年 | 134篇 |
2014年 | 153篇 |
2013年 | 195篇 |
2012年 | 249篇 |
2011年 | 247篇 |
2010年 | 161篇 |
2009年 | 121篇 |
2008年 | 196篇 |
2007年 | 194篇 |
2006年 | 136篇 |
2005年 | 148篇 |
2004年 | 157篇 |
2003年 | 85篇 |
2002年 | 87篇 |
2001年 | 71篇 |
2000年 | 74篇 |
1999年 | 59篇 |
1998年 | 15篇 |
1997年 | 16篇 |
1996年 | 16篇 |
1995年 | 21篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 16篇 |
1991年 | 20篇 |
1990年 | 10篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 4篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 2篇 |
1973年 | 3篇 |
1970年 | 1篇 |
1969年 | 4篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有3018条查询结果,搜索用时 15 毫秒
991.
992.
993.
Kim HM Park BS Kim JI Kim SE Lee J Oh SC Enkhbayar P Matsushima N Lee H Yoo OJ Lee JO 《Cell》2007,130(5):906-917
TLR4 and MD-2 form a heterodimer that recognizes LPS (lipopolysaccharide) from Gram-negative bacteria. Eritoran is an analog of LPS that antagonizes its activity by binding to the TLR4-MD-2 complex. We determined the structure of the full-length ectodomain of the mouse TLR4 and MD-2 complex. We also produced a series of hybrids of human TLR4 and hagfish VLR and determined their structures with and without bound MD-2 and Eritoran. TLR4 is an atypical member of the LRR family and is composed of N-terminal, central, and C-terminal domains. The beta sheet of the central domain shows unusually small radii and large twist angles. MD-2 binds to the concave surface of the N-terminal and central domains. The interaction with Eritoran is mediated by a hydrophobic internal pocket in MD-2. Based on structural analysis and mutagenesis experiments on MD-2 and TLR4, we propose a model of TLR4-MD-2 dimerization induced by LPS. 相似文献
994.
995.
Lee SR Kim JW Kim BS Kim MO Kim SH Yoo DH Shin MJ Lee S Park YS Park YB Ha JH Ryoo ZY 《Theriogenology》2007,67(4):698-703
In the present study, canine oocytes were exposed to various concentrations of and durations of exposure to EDTA saturated with Ca(2+) (Ca-EDTA), a cell membrane-impermeable metal ion chelator, to determine if parthenogenetic activation could be induced. When oocytes were cultured for 48 or 72 h in parthenogenetic activation medium (PAM) without Ca-EDTA (control) or PAM supplemented with 1 or 5mM Ca-EDTA, the highest rate of pronuclear formation (PN) was obtained in oocytes cultured in 1mM Ca-EDTA for 48 h (8.0%; P<0.05). There was no pronuclear formation in the control group (PAM without Ca-EDTA). Oocytes treated with 5mM Ca-EDTA for 48 h or 1mM Ca-EDTA for 72 h formed a parthenogenetic pronucleus (3.1 and 4.5, respectively). However, there was no pronuclear formation in oocytes treated with 5mM Ca-EDTA for 72 h. In summary, exposure to Ca-EDTA can induce pronuclear formation in canine oocytes. 相似文献
996.
Physicochemical and biological characteristics of the exopolysaccharide, PS7, produced from Beijerinckia indica were investigated. The PS7 weight fractions of Glc and GlcUA were 0.45 and 0.25, respectively, and the molar ratio of Glc:Rha:GalUA was approximately 5:1:1.3. The PS7 was chemically derivatized with diethylaminoethyl chloride-HCl (DEAE-HCl), and the resulting modified PS7 contained both positive and negative charges. The elemental and IR analyses were conducted to confirm the successful incorporation of DEAE groups into PS7. Large increase in nitrogen fraction was observed from the derivatized PS7 by elemental analysis. The characteristic CH(3) and CH(2) peaks originated from DEAE group were detected in (1)H NMR spectrum of the derivatized PS7 as well. Solubility of native PS7 was improved almost twice from 40 to 75% after DEAE-derivatization, while water holding capacity (WHC) drastically decreased from 10,026 to 245%. Oil binding capacity (OBC) of PS7 also significantly dropped from 1528 to 331% after the derivatization. The [eta] values of native and derivatized PS7 were 27.6 and 0.31 dL/g at 25 degrees C, respectively, which means that the DEAE-derivatization significantly decreased the [eta] of PS7. The bile acid binding capacity of PS7 was indirectly determined by measuring the holding capability of cholic acid inside the dialysis membrane. When PS7 was DEAE-derivatized, there was substantial decrease in the cholic acid retardation index (CRI). Up to 8-9h of dialysis, the derivatized PS7 hold 8.6% less of cholic acid compared to native one. 相似文献
997.
998.
Hwang IK Yoo KY Li H Choi JH Kwon YG Ahn Y Lee IS Won MH 《Neurochemical research》2007,32(9):1604-1609
Doublecortin (DCX), a microtubule-associated protein, specifically expresses in neuronal precursors. This protein has been
used as a marker for neuronal precursors and neurogenesis. In the present study, we observed differences in DCX immunoreactivity
and its protein levels in the hippocampal dentate gyrus between adult and aged dogs. In the adult dog, DCX immunoreactive
cells with well-stained processes were detected in the subgranular zone of the dentate gyrus. Numbers of DCX immunoreactive
cells in the dentate gyrus of the aged dog were significantly decreased compared to those in the adult dog. DCX immunoreactive
cells in both adult and aged dog did not show NeuN (a marker for mature neurons) immunoreactivity. NeuN immunoreactivity in
the aged dog was poor compared to that in the adult dog. DCX protein level in the aged dentate gyrus was decreased by 80%
compared to that in the adult dog. These results suggest that the reduction of DCX in the aged hippocampal dentate gyrus may
be involved in some neural deficits related to the hippocampus. 相似文献
999.
Phylogenetic studies were conducted for Carpinus and the subfamily Coryloideae (Betulaceae) using sequences of the chloroplast matK gene, the trnL-trnF region (trnL intron, and trnL [UAA] 3' exon-trnF [GAA] intergenic spacer) and the psbA-trnH intergenic spacer, and the nuclear ribosomal ITS regions. The combined analyses of the three chloroplast regions suggest
that Coryloideae is monophyletic; Ostryopsis is sister to the Carpinus - Ostrya clade; Corylus is monophyletic and sister to the Ostrya - Carpinus - Ostryopsis clade; Ostrya is paraphyletic; and within Carpinus, species of sect. Carpinus from eastern Asia form a monophyletic group, whereas the positions of C. betulus from Europe and C. caroliniana from eastern North America are unresolved within the Carpinus clade. The cpDNA tree generated in this study is largely congruent with the previously published ITS results, but the ITS
tree places Carpinus sect. Distegocarpus as sister to the Ostrya - Carpinus sect. Carpinus clade. Future work is needed to examine the relationships within the Ostrya - Carpinus clade, evaluate the generic status of Ostrya, and test the phylogenetic position of Ostryopsis. 相似文献
1000.
Kim HA Jeong KS Park DH Lee JA Jeong WI Kim YK 《Molecular and cellular biochemistry》2007,301(1-2):201-208
Heavy water labeling method was applied to measure the effect of genistein on mammary gland carcinogenesis by incoporating
2H from 2H2O into the deoxyribose (dR) moiety of purine deoxyribonucleotides in dividing cells. In the present study, we followed the
study design of Lamartiniere group to evaluate the efficacy of 2H2O labeling on the measurement of mammary gland carconogenesis. Female Sprague–Dawley rats were fed estrogen-free AIN-93G diet
starting 1 week before breeding and continuing through pregnancy and lactation. Female pups were assigned to the following
groups on postnatal day 16 and fed AIN-93G diet: vehicle (dimethylsulfoxide) (DMSO), genistein, and estradiol benzoate (EB).
On postnatal days 16, 18, and 20, female pups were injected subcutaneously with 500 μg genistein/g body wt, 500 ng EB/g body
wt, or an equivalent volume of the vehicle. At day 50 postpartum, half of each group were gavaged with 60 mg dimethylbenz[a]anthracene
(DMBA) in perila oil. After 1 week of DMBA treatment, all animals were labeled with 2H2O by administration of 4% 2H2O in drinking water after single intraperitonial bolus injection with 99.9% 2H2O until sacrifice on postnatal day 81. The time-dependent weight gains were observed in all groups throughout the experimental
period. The enrichment of body 2H2O was attained at 1.84–2.47% through oral administration of 2H2O. Mammary epithelial cell proliferation was measured by enrichment (EM1) of dA from rats. DMBA-treated groups showed higher
fractional synthesis than DMBA non-treated groups. The group exposed only to genistein showed significantly lower EM1 (1.46 ± 0.87%)
than those of control groups, i.e., the DMBA non-treated group (2.28 ± 0.29%) and the DMBA-treated group (2.32 ± 0.28%). Bromodeoxyuridine
(BrdU) immunostaining of mammary tissue revealed that genistein reduced proliferation of the mammary epithelial, and the number
of cells stained positive for BrdU both in DMBA-treated groups and DMBA non-treated groups. H&E staining of mammary epithelium
also showed that the exposure to genistein decreased proliferation of the mammary epithelium. The epithelium in the rats treated
with DMBA showed mostly multiple cell layers, in contrast to the mostly double layer shown in the DMBA non-treated rats. The
exposure to genistein in the prepubertal period inhibited mammary epithelial cell proliferation. In conclusion, the 2H2O labeling results were in good agreement with the results of BrdU incorporation and histomorphometry, which demonstrates
that 2H2O labeling can be used as a tool to measure carcinogenesis. 相似文献