全文获取类型
收费全文 | 4200篇 |
免费 | 297篇 |
国内免费 | 6篇 |
出版年
2023年 | 19篇 |
2022年 | 19篇 |
2021年 | 75篇 |
2020年 | 41篇 |
2019年 | 50篇 |
2018年 | 108篇 |
2017年 | 80篇 |
2016年 | 131篇 |
2015年 | 218篇 |
2014年 | 233篇 |
2013年 | 286篇 |
2012年 | 313篇 |
2011年 | 321篇 |
2010年 | 186篇 |
2009年 | 174篇 |
2008年 | 224篇 |
2007年 | 190篇 |
2006年 | 220篇 |
2005年 | 180篇 |
2004年 | 174篇 |
2003年 | 171篇 |
2002年 | 152篇 |
2001年 | 94篇 |
2000年 | 98篇 |
1999年 | 73篇 |
1998年 | 33篇 |
1997年 | 28篇 |
1996年 | 27篇 |
1995年 | 21篇 |
1994年 | 30篇 |
1993年 | 24篇 |
1992年 | 44篇 |
1991年 | 33篇 |
1990年 | 31篇 |
1989年 | 28篇 |
1988年 | 21篇 |
1987年 | 25篇 |
1986年 | 17篇 |
1985年 | 17篇 |
1984年 | 17篇 |
1983年 | 20篇 |
1979年 | 18篇 |
1977年 | 15篇 |
1975年 | 16篇 |
1974年 | 20篇 |
1973年 | 17篇 |
1972年 | 20篇 |
1970年 | 13篇 |
1969年 | 13篇 |
1967年 | 13篇 |
排序方式: 共有4503条查询结果,搜索用时 996 毫秒
991.
Suk Weon Kim Sung Hee Ban Soon-Chun Jeong Hwa-Jee Chung Suk Min Ko Ook Joon Yoo Jang R. Liu 《Biotechnology and Bioprocess Engineering》2007,12(6):646-652
When whole cell extracts are subjected to proton nuclear magnetic resonance spectroscopy (1H NMR), metabolite profiles are generated that contain overlapping signals of the majority of compounds within the extract.
In order to determine whether pattern recognition based on the metabolite profiles of higher plants is able to genetically
discriminate between plants, we analyzed leaf samples of eight cultivars ofCatharanthus roseus by1H NMR. Hierarchical dendrograms, based on the principal component analysis of the1H NMR total, aliphatic carbohydrate and aromatic region data, revealed possible relationships between the cultivars. The dendrogram
based on the aromatic region data was in general agreement with the genetic relationships determined by conventional DNA fingerprinting
methods. Secologanin and polyphenols were assigned to the signals of the1H NMR spectra, and contributed most profoundly to the discrimination between cultivars. The overall results indicate that
the genetic relationships betweenC. roseus cultivars are reflected in the differences of the aromatic compounds in the leaves. 相似文献
992.
Byung-Hoon Kim Doman Kim Dong-Lyun Cho Sung-Hoon Lim So young Yoo Joong-ki Kook Yong ick Cho Seung-Ho Ohk Yeong-Mu Ko 《Biotechnology and Bioprocess Engineering》2007,12(2):136-139
Streptococcus mutans is one of the more significant pathogens involved in the development of dental caries in humans. The purpose of this research
was to design a TiO2-coated dental instrument and to determine the bactericidal effects of the instrument onS. mutants. TiO2 photocatalytic films were prepared by the low-pressure metal-organic chemical vapor deposition (LPMOCVD) method using titanium
tetraisopropoxide (TTIP) as precursor. The photocatalytic reaction was carried out on a TiO2-coated pyrex petri dish with an ultraviolet (UV) light emitting diode (LED) illuminator or a fluorescent lamp light source.
Our data indicates that the relative survival ratio ofS. mutans when plated onto TiO2 photocatalytic films and under exposure to UV-A light for 15 min was 0.01%. In addition, a fluorescent lamp light source
also had bactericidal effects on theS. mutans plated TiO2 photocatalytic films. These results indicate that TiO2-coated dental materials or devices may be useful in dental treatments for the prevention of carious or enamel demineralization. 相似文献
993.
Development of a general‐purpose method for cell purification using Cre/loxP‐mediated recombination 下载免费PDF全文
Shunsuke Kuroki Mika Akiyoshi Ko Ideguchi Satsuki Kitano Hitoshi Miyachi Michiko Hirose Nathan Mise Kuniya Abe Atsuo Ogura Makoto Tachibana 《Genesis (New York, N.Y. : 2000)》2015,53(6):387-393
A mammalian body is composed of more than 200 different types of cells. The purification of a certain cell type from tissues/organs enables a wide variety of studies. One popular cell purification method is immunological isolation, using antibodies against specific cell surface antigens. However, this is not a general‐purpose method, since suitable antigens have not been found in certain cell types, including embryonic gonadal somatic cells and Sertoli cells. To address this issue, we established a knock‐in mouse line, named R26 KI, designed to express the human cell surface antigen hCD271 through Cre/loxP‐mediated recombination. First, we used the R26 Kl mouse line to purify embryonic gonadal somatic cells. Gonadal somatic cells were purified from the R26 KI; Nr5a1‐Cre‐transgenic (tg) embryos almost equally as efficiently as from Nr5a1‐hCD271‐tg embryos. Second, we used the R26 KI mouse line to purify Sertoli cells successfully from R26 KI; Amh‐Cre‐tg testes. In summary, we propose that the R26 KI mouse line is a powerful tool for the purification of various cell types. genesis 53:387–393, 2015. © 2015 Wiley Periodicals, Inc. 相似文献
994.
995.
Heterologous expression and characterization of endocellulase from the Japanese pine sawyer Monochamus saltuarius (MsGHF5) 下载免费PDF全文
Hyunjun Ko Hyuk‐Min Kwon Hyun‐Jin Ko Ji‐Hyeon Ryu Hwi‐Seung Song Yong Chul Park 《Entomological Research》2015,45(1):26-30
In this study, the endocellulase gene from Monochamus saltuarius (MsGHF5) was transformed into Escherichia coli (RosettaBlue(DE3)pLysS strain), and induced by IPTG. The molecular weight of recombinant MsGHF5 (rMsGHF5) was 78 kDa and was expressed as a fusion protein with maltose binding protein in pMAL‐c2 expression vector. Native‐PAGE was conducted with 0.1% carboxymethyl cellulose as a substrate, and the zymogenic bands were observed. The Michaelis constant and maximum velocity of rMsGHF5 were 0.199 mg/mL and 0.034 μmol/min/mL, respectively. The optimal condition for rMsGHF5 occurred at pH 5 and 30°C. Fe2+ and Mn2+ stimulated the activity of rMsGHF5 by 167 and 114% respectively, whereas Cu2+, Hg2+ and Zn2+ inhibited its activity. 相似文献
996.
In vitro generation of functional dendritic cells differentiated from CD34 negative cells isolated from human umbilical cord blood 下载免费PDF全文
997.
Ko Tomikawa 《ZooKeys》2015,(530):15-36
A new species of anisogammarid amphipod, Jesogammarus (Jesogammarus) ikiensis
sp. n., is described from freshwaters in the Iki Island, Nagasaki Prefecture, Japan, based on results of morphological and molecular analyses. The new species is distinguished from all members of the genus by the combination of small number of setae on dorsal margins of pleonites 1–3, short and small number of setae on posterior margins of peduncular articles of antennae, mandibular article 1 without setae, well developed posterior lobes of accessory lobes of coxal gills on gnathopod 2 and pereopods 3–5, and pectinate setae on palmar margin of female gnathopod 2. A key to all the species of Jesogammarus is provided. 相似文献
998.
999.
Tomokazu Amano Emiko Jeffries Misa Amano Akihiro C. Ko Hong Yu Minoru S. H. Ko 《DNA research》2015,22(5):331-342
Aneuploidy, an abnormal number of chromosomes, has previously been considered irremediable. Here, we report findings that euploid cells increased among cultured aneuploid cells after exposure to the protein ZSCAN4, encoded by a mammalian-specific gene that is ordinarily expressed in preimplantation embryos and occasionally in stem cells. For footprint-free delivery of ZSCAN4 to cells, we developed ZSCAN4 synthetic mRNAs and Sendai virus vectors that encode human ZSCAN4. Applying the ZSCAN4 biologics to established cultures of mouse embryonic stem cells, most of which had become aneuploid and polyploid, dramatically increased the number of euploid cells within a few days. We then tested the biologics on non-immortalized primary human fibroblast cells derived from four individuals with Down syndrome—the most frequent autosomal trisomy of chromosome 21. Within weeks after ZSCAN4 application to the cells in culture, fluorescent in situ hybridization with a chromosome 21-specific probe detected the emergence of up to 24% of cells with only two rather than three copies. High-resolution G-banded chromosomes further showed up to 40% of cells with a normal karyotype. These findings were confirmed by whole-exome sequencing. Similar results were obtained for cells with the trisomy 18 of Edwards syndrome. Thus a direct, efficient correction of aneuploidy in human fibroblast cells seems possible in vitro using human ZSCAN4. 相似文献
1000.
Ginsenoside Rg1 improves bone marrow haematopoietic activity via extramedullary haematopoiesis of the spleen 下载免费PDF全文
Hua‐Hsing Liu Fei‐Peng Chen Rong‐Kai Liu Chun‐Lin Lin Ko‐Tung Chang 《Journal of cellular and molecular medicine》2015,19(11):2575-2586
Cyclophosphamide (CY) is a chemotherapeutic agent used for cancer and immunological diseases. It induces cytotoxicity of bone marrow and causes myelosuppression and extramedullary haematopoiesis (EMH) in treated patients. EMH is characterized with the emergence of multipotent haematopoietic progenitors most likely in the spleen and liver. Previous studies indicated that a Chinese medicine, ginsenoside Rg1, confers a significant effect to elevate the number of lineage (Lin−) Sca-1+ c-Kit+ haematopoietic stem and progenitor cells (HSPCs) and restore the function of bone marrow in CY-treated myelosuppressed mice. However, whether the amelioration of bone marrow by Rg1 accompanies an alleviation of EMH in the spleen was still unknown. In our study, the cellularity and weight of the spleen were significantly reduced after Rg1 treatment in CY-treated mice. Moreover, the number of c-Kit+ HSPCs was significantly decreased but not as a result of apoptosis, indicating that Rg1 alleviated EMH of the spleen induced by CY. Unexpectedly, the proliferation activity of c-Kit+ HSPCs was only up-regulated in the spleen, but not in the bone marrow, after Rg1 treatment in CY-treated mice. We also found that a fraction of c-Kit+/CD45+ HSPCs was simultaneously increased in the circulation after Rg1 treatment. Interestingly, the effects of Rg1 on the elevation of HSPCs in bone marrow and in the peripheral blood were suppressed in CY-treated splenectomized mice. These results demonstrated that Rg1 improves myelosuppression induced by CY through its action on the proliferation of HSPCs in EMH of the spleen and migration of HSPCs from the spleen to the bone marrow. 相似文献