全文获取类型
收费全文 | 3261篇 |
免费 | 224篇 |
国内免费 | 1篇 |
专业分类
3486篇 |
出版年
2024年 | 4篇 |
2023年 | 12篇 |
2022年 | 42篇 |
2021年 | 58篇 |
2020年 | 38篇 |
2019年 | 45篇 |
2018年 | 90篇 |
2017年 | 63篇 |
2016年 | 120篇 |
2015年 | 160篇 |
2014年 | 218篇 |
2013年 | 240篇 |
2012年 | 289篇 |
2011年 | 275篇 |
2010年 | 170篇 |
2009年 | 161篇 |
2008年 | 196篇 |
2007年 | 187篇 |
2006年 | 177篇 |
2005年 | 141篇 |
2004年 | 179篇 |
2003年 | 108篇 |
2002年 | 102篇 |
2001年 | 107篇 |
2000年 | 69篇 |
1999年 | 56篇 |
1998年 | 16篇 |
1997年 | 21篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 16篇 |
1991年 | 17篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有3486条查询结果,搜索用时 15 毫秒
71.
Sung-Ho Oh Juhee Ahn Do-Hyung Kang Hyeon-Yong Lee 《Marine biotechnology (New York, N.Y.)》2011,13(2):205-214
The effect of ultrasonic extraction on extraction yields, cytotoxicity, and anticancer activity of Spirulina maxima was investigated in this study. Optimal extraction conditions were determined as 60 kHz frequency at 60°C for 30 min with
120 W intensity, which resulted in 19.3% of extraction yields and 19.1% of cytotoxicity on normal human cells. Yields from
conventional water and ethanol extraction were 15.8% at 100°C and 8.3% at 80°C, respectively. It was found that the extracts
obtained by ultrasonic extraction process selectively inhibited the digestive-related cancer cell lines, such as human stomach
cancer cells, having 89% of the highest inhibition ratio and 4.5 of the highest selectivity. In adding 0.5 mg/mL of the extract,
human promyelocytic leukemia cells' cell differentiation was increased 1.72 times over that of the control. Expression level
of B cell lymphoma-2 from Hep3B cell was also effectively suppressed by the extract obtained at 60 kHz and 60°C, leading to
the inhibition of the early step of carcinogenesis. This work suggests that anticancer activity of the extracts is due to
water-soluble polysaccharides rather than proteins and is further supported by the result that the ultrasonification extraction
process can efficiently extract relatively intact polysaccharides rather than digesting the proteins in S. maxima by matrix assisted laser desorption ionization-time of flight and high performance size exclusion chromatography chromatogram
analyses. Therefore, ultrasonic extraction increases both extraction yield and the biological activity of S. maxima extracts, which might be useful as an alternative natural anticancer agent in the medical and food industries. 相似文献
72.
Park SH Kim CM Je BI Park SH Park SJ Piao HL Xuan YH Choe MS Satoh K Kikuchi S Lee KH Cha YS Ahn BO Ji HS Yun DW Lee MC Suh SC Eun MY Han CD 《Planta》2007,227(1):1-12
OSH6 (Oryza sativa Homeobox6) is an ortholog of lg3 (Liguleless3) in maize. We generated a novel allele, termed OSH6-Ds, by inserting a defective Ds element into the third exon of OSH6, which resulted in a truncated OSH6 mRNA. The truncated mRNA was expressed ectopically in leaf tissues and encoded the N-terminal region of OSH6, which includes
the KNOX1 and partial KNOX2 subdomains. This recessive mutant showed outgrowth of bracts or produced leaves at the basal node
of the panicle. These phenotypes distinguished it from the OSH6 transgene whose ectopic expression led to a “blade to sheath transformation” phenotype at the midrib region of leaves, similar
to that seen in dominant Lg3 mutants. Expression of a similar truncated OSH6 cDNA from the 35S promoter (35S::ΔOSH6) confirmed that the ectopic expression of this product was responsible for the aberrant bract development. These data suggest
that OSH6-Ds interferes with a developmental mechanism involved in bract differentiation, especially at the basal nodes of panicles.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
73.
74.
Inhibin is a gonadal hormone which is composed of an alpha-subunit and one of two related beta-subunits (betaA, betaB). Inhibin is important for pituitary FSH regulation, normal follicle development and maintenance of the estrous cycle in the female, whereas the role of inhibin in the male is less clear. Thus, we examined the expression of the inhibin-alpha gene in testis during sexual maturation in male mice, to try to gain insight into its functions in the male. Male mice of the ICR strain attained fertility at 6 weeks of age, and histological analysis revealed that a functional testis was formed, with seminiferous tubules which contain mature sperm and with an abundant population of Leydig cells. Parallel with this sexual maturation, inhibin-alpha subunit protein synthesis increased, whereas synthesis of the activin betaA and activin betaB followed with a delayed time course. Inhibin-alpha mRNA also increased during this critical period, and this corresponded to a change in the methylation status of the inhibin-alpha gene. Taken together, our data reveal that activation of inhibin-alpha gene during testis development correlated with the histological maturation of the testis and the acquisition of fertility in male mice. 相似文献
75.
76.
Zhirong Li Tae Kyu Ahn Thomas J. Avenson Matteo Ballottari Jeffrey A. Cruz David M. Kramer Roberto Bassi Graham R. Fleming Jay D. Keasling Krishna K. Niyogi 《The Plant cell》2009,21(6):1798-1812
Plants protect themselves from excess absorbed light energy through thermal dissipation, which is measured as nonphotochemical quenching of chlorophyll fluorescence (NPQ). The major component of NPQ, qE, is induced by high transthylakoid ΔpH in excess light and depends on the xanthophyll cycle, in which violaxanthin and antheraxanthin are deepoxidized to form zeaxanthin. To investigate the xanthophyll dependence of qE, we identified suppressor of zeaxanthin-less1 (szl1) as a suppressor of the Arabidopsis thaliana npq1 mutant, which lacks zeaxanthin. szl1 npq1 plants have a partially restored qE but lack zeaxanthin and have low levels of violaxanthin, antheraxanthin, and neoxanthin. However, they accumulate more lutein and α-carotene than the wild type. szl1 contains a point mutation in the lycopene β-cyclase (LCYB) gene. Based on the pigment analysis, LCYB appears to be the major lycopene β-cyclase and is not involved in neoxanthin synthesis. The Lhcb4 (CP29) and Lhcb5 (CP26) protein levels are reduced by 50% in szl1 npq1 relative to the wild type, whereas other Lhcb proteins are present at wild-type levels. Analysis of carotenoid radical cation formation and leaf absorbance changes strongly suggest that the higher amount of lutein substitutes for zeaxanthin in qE, implying a direct role in qE, as well as a mechanism that is weakly sensitive to carotenoid structural properties. 相似文献
77.
The DNA repair machinery must locate and repair DNA damage all over the genome. As nucleosomes inhibit DNA repair in vitro, it has been suggested that chromatin remodeling might be required for efficient repair in vivo. To investigate a possible contribution of nucleosome dynamics and chromatin remodeling to the repair of UV-photoproducts in nucleosomes, we examined the effect of a chromatin remodeling complex on the repair of UV-lesions by Micrococcus luteus UV endonuclease (ML-UV endo) and T4-endonuclease V (T4-endoV) in reconstituted mononucleosomes positioned at one end of a 175-bp long DNA fragment. Repair by ML-UV endo and T4-endoV was inefficient in mononucleosomes compared with naked DNA. However, the human nucleosome remodeling complex, hSWI/SNF, promoted more homogeneous repair by ML-UV endo and T4-endo V in reconstituted nucleosomes. This result suggests that recognition of DNA damage could be facilitated by a fluid state of the chromatin resulting from chromatin remodeling activities. 相似文献
78.
79.
80.
Seong Rim Byeon Hyunjin Vincent Kim Mijin Jeon Young Gil Ahn Maeng Sup Kim Jae Yang Kong Hye Yun Kim Young Soo Kim Dong Jin Kim 《Bioorganic & medicinal chemistry letters》2013,23(11):3467-3469
Alzheimer’s disease drug discovery regarding exploration into the molecules and processes has focused on the intrinsic causes of the brain disorder correlated with the accumulation of amyloid-β. An anti-amyloidogenic bis-styrylbenzene derivative, KMS80013, showed excellent oral bioavailability (F = 46.2%), facilitated brain penetration (26%, iv) in mouse and target specific in vivo efficacy in acute AD mouse model attenuating the cognitive deficiency in Y-maze test. Acute toxicity (LD50 >2000 mg/kg) and hERG channel inhibition (14% at 10 μM) results indicated safety of KMS80013. 相似文献