全文获取类型
收费全文 | 1362篇 |
免费 | 108篇 |
国内免费 | 5篇 |
出版年
2021年 | 24篇 |
2020年 | 21篇 |
2019年 | 17篇 |
2018年 | 36篇 |
2017年 | 32篇 |
2016年 | 44篇 |
2015年 | 64篇 |
2014年 | 67篇 |
2013年 | 94篇 |
2012年 | 98篇 |
2011年 | 85篇 |
2010年 | 54篇 |
2009年 | 38篇 |
2008年 | 55篇 |
2007年 | 54篇 |
2006年 | 46篇 |
2005年 | 44篇 |
2004年 | 29篇 |
2003年 | 29篇 |
2002年 | 33篇 |
2001年 | 29篇 |
2000年 | 30篇 |
1999年 | 19篇 |
1998年 | 18篇 |
1997年 | 9篇 |
1995年 | 10篇 |
1994年 | 15篇 |
1993年 | 12篇 |
1992年 | 16篇 |
1991年 | 24篇 |
1990年 | 16篇 |
1989年 | 14篇 |
1988年 | 19篇 |
1987年 | 30篇 |
1986年 | 21篇 |
1985年 | 26篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 15篇 |
1981年 | 9篇 |
1980年 | 10篇 |
1979年 | 13篇 |
1978年 | 9篇 |
1976年 | 8篇 |
1974年 | 9篇 |
1973年 | 14篇 |
1972年 | 8篇 |
1971年 | 8篇 |
1970年 | 10篇 |
1968年 | 8篇 |
排序方式: 共有1475条查询结果,搜索用时 15 毫秒
111.
Inja Lim Jihyun Yun Jung‐Ha Kim Young‐Ku Kang Nari Kim Jin Han Hyoweon Bang Jae‐Hong Ko 《Birth defects research. Part B, Developmental and reproductive toxicology》2010,89(3):201-206
BACKGROUND: This study was conducted to evaluate the occurrence and fate of fetal lumbar rib induced by Scutellariae radix (SR) in rats. METHODS: Water extracts of SR were orally administered to pregnant rats from day 7 to day 17 of gestation at a dose of 186 mg/kg/day, equivalent to 25 g/kg of starting material, representing a 100‐fold increase over typical human intake level. RESULTS: The incidence of fetal lumbar rib in the SR‐treated group was increased on gestational day 20 and then decreased on postnatal day 50. The weight of fetuses in the SR‐treated group tended to be less than that in the control group. Alkaline phosphatase in SR‐treated dams was increased on gestational day 20, but was decreased on postnatal day 50. There were no significant differences between the vehicle control and SR‐treated groups in maternal body weight, embryological, histopathological, hematological, and serum biochemical changes. CONCLUSIONS: The present data suggest that the appearance of lumbar rib induced by SR is a transient fetal variation rather than teratogenicity or maternal toxicity. Birth Defects Res (Part B) 89:201–206, 2010. © 2010 Wiley‐Liss, Inc. 相似文献
112.
113.
114.
Browning of chitooligomers and their optimum preservation 总被引:1,自引:0,他引:1
Lintao Zeng Caiqin Qin Weilin Chi Liansheng Wang Zongjun Ku Wei Li 《Carbohydrate polymers》2007,67(4):551-558
Chitooligomers have attracted much interest due to their unique biological activities. However, chitooligomers easily turn brown during shelf life. The factors influencing the browning of chitooligomers were investigated. The results indicated that the browning was attributed to the structure change of chitooligomers. The water-solubility, thermal stability and moisture–adsorption of chitooligomers decreased with the increase of browning. The time, temperature, pH, moisture, oxygen and reductant all had effect on the browning of chitooligomers. The optimal preservation condition for chitooligomers should be at low temperature and humidity, at pH below 4 or above 10, and in absence of oxygen. 相似文献
115.
Phylogenetic analysis of two putative Nosema isolates from Cruciferous Lepidopteran pests in Taiwan 总被引:1,自引:0,他引:1
In this study, a new microsporidian, PX2, was isolated from the diamondback moth, Plutella xylostella, and then compared with another isolate (PX1), and with Nosema spodopterae and N. bombycis. Sequence data showed that the rRNA gene organizations of PX1 and PX2 exhibited a typical Nosema-specific organization: 5'-LSUrRNA (large subunit ribosomal RNA)-ITS (internal transcribed spacer)-SSUrRNA-IGS (intergenic spacer)-5S-3'. Phylogenetic analysis (maximum likelihood, neighbor joining, maximum parsimony, and Bayesian analysis) of the LSUrRNA and SSUrRNA gene sequences, and the sequences of the alpha-tubulin, beta-tubulin, and RPB1 (DNA dependent RNA polymerase II largest subunit) genes found that PX1 was closer to N. bombycis and N. spodopterae than to PX2. Comparison of the identities of the rRNA domains and of the other three genes showed a high divergence in the sequences of the rRNA spacer regions (ITS and IGS). This is consistent with the hypothesis that PX2, if not PX1, might represent a new Nosema species. 相似文献
116.
The selective RNA-binding protein quaking I (QKI) is necessary and sufficient for promoting oligodendroglia differentiation 总被引:1,自引:0,他引:1
Chen Y Tian D Ku L Osterhout DJ Feng Y 《The Journal of biological chemistry》2007,282(32):23553-23560
Quaking I (QKI) is a selective RNA-binding protein essential for myelination of the central nervous system. Three QKI isoforms with distinct C termini and subcellular localization, namely QKI-5, QKI-6, and QKI-7, are expressed in oligodendroglia progenitor cells (OPCs) prior to the initiation of myelin formation and implicated in promoting oligodendrocyte lineage development. However, the functional requirement for each QKI isoform and the mechanisms by which QKI isoforms govern OPC development still remain elusive. We report here that exogenous expression of each QKI isoform is sufficient to enhance differentiation of OPCs with different efficiency, which is abolished by a point mutation that abrogates the RNA binding activity of QKI. Reciprocally, small interfering RNA-mediated QKI knockdown blocks OPC differentiation, which can be partly rescued by QKI-5 and QKI-6 but not by QKI-7, indicating the differential requirement of QKI isoform function in advancing OPC differentiation. Furthermore, we found that abrogation of OPC differentiation, as a result of QKI deficiency, is not due to altered proliferation capacity or cell cycle progression. These results indicate that QKI isoforms are necessary and sufficient for promoting OPC development, which must involve direct influence of QKI on differentiation/maturation of OPCs independent of cell cycle exit, likely via regulating the expression of the target mRNAs of QKI that support OPC differentiation. 相似文献
117.
A fluorescent method was developed for the detection of unpaired and mismatched DNAs using a MutS-fluorophore conjugate. The fluorophore, 2-(4'-(iodoacetoamido)anilino) naphthalene-6-sulfonic acid (IAANS), was site-specifically attached to the 469 position of Thermus aquaticus (Taq.) MutS mutant (C42A/T469C). The fluorophore labeled residue located at the dimer interface of the protein undergoes a drastic conformational change upon binding with mismatched DNA. The close proximity of the two identical fluorescent molecules presumably causes the self-quenching of the fluorophore, since fluorescence emission of the biosensor decreases with increasing concentrations of mismatched DNA. The order of binding affinity for each unpaired and mismatched DNA obtained by this method was DeltaT (Kd=52 nM)>GT (62 nM)>DeltaC (130 nM)>CT (160 nM)>DeltaG (170 nM)>DeltaA (250 nM)>CC (720 nM)>AT (950 nM). This order is comparable to the previous results of the gel mobility shift assay. Thus, this method can be a simple, useful tool for elucidating the mechanism of DNA mismatch repair as well as a novel probe for detecting of genetic mutation. 相似文献
118.
Black LA Nersesian DL Sharma P Ku YY Bennani YL Marsh KC Miller TR Esbenshade TA Hancock AA Cowart M 《Bioorganic & medicinal chemistry letters》2007,17(5):1443-1446
4-[6-(2-Tertiaryaminoethyl)naphthalen-2-yl]benzonitriles are conformationally constrained histamine H3 receptor antagonists with high potency and selectivity. The analogs were designed around a naphthalene core, with the goal of enhancing lipophilicity and CNS penetration, as compared to a previously reported benzofuran series. The SAR of the tertiary amine moiety is similar to that reported for the benzofuran series, with analogs bearing a 2-methylpyrrolidine substituent possessing the greatest rat and human H3 receptor binding affinities. 相似文献
119.
Nonsyndromic orofacial clefting (NS-OFC) is a common complex multifactorial trait with a considerable genetic component and a number of candidate genes suggested by various approaches. Twenty biallelic and microsatellite DNA markers in the strong candidate loci TGFA, TGFB3, GABRB3, RARA, and BCL3 were analysed for allelic association with the NS-OFC phenotype in 112 nuclear families (proband + both parents) from Lithuania by using the transmission disequilibrium test (TDT). Associations were found between the TGFA gene marker rs2166975 and nonsyndromic cleft palate only (CPO) phenotype (p = 0.045, df 1) as well as between the D2S292 marker and the cleft lip with or without cleft palate (CL/CP) phenotype in allele-wise TDT (P = 0.005, df 9) and genotype-wise TDT (P = 0.021, df 24). A weak association (P = 0.085, df 3) of the BCL3 marker (BCL3 gene) with the risk of CPO was also found. Thus our initial results support the contribution of allelic variation in the TGFA locus to the aetiology of CL/CP in the population of Lithuania but they do not point to TGFA as a major causal gene. Different roles of the TGFA and BCL3 genes in the susceptibility to NS-OFC phenotypes are suggested. 相似文献
120.
Kim JD Kang SM Park MY Jung TY Choi HY Ku SK 《Bioscience, biotechnology, and biochemistry》2007,71(6):1527-1534
The preventive anti-diabetic effect of dangnyosoko (DNSK), a Chinese herbal medicine, was evaluated in STZ-induced diabetic rats. DNSK was orally administered once a day from 3 d after STZ-induction at 100, 200, and 500 mg/kg for 4 weeks, and the results were compared to those for glibenclamide. Dramatic decreases in body weight and plasma insulin levels and increases in blood and urine glucose levels were detected in STZ-induced diabetic animals with disruption and disappearance of pancreatic islets and increases in glucagon- and decreases in insulin-producing cells. However, these diabetic changes were significantly and dose-dependently inhibited by treatment with DNSK, and DNSK at 100 mg/kg showed more favorable effects than glibenclamide at 5 mg/kg. Based on these results, it is thought that DNSK has favorable effects in ameliorating changes in blood and urine glucose levels and body weight, and that histopathological changes in the pancreas in STZ induce diabetes. 相似文献