全文获取类型
收费全文 | 10772篇 |
免费 | 565篇 |
国内免费 | 4篇 |
出版年
2022年 | 53篇 |
2021年 | 122篇 |
2020年 | 57篇 |
2019年 | 83篇 |
2018年 | 129篇 |
2017年 | 120篇 |
2016年 | 170篇 |
2015年 | 260篇 |
2014年 | 308篇 |
2013年 | 651篇 |
2012年 | 548篇 |
2011年 | 501篇 |
2010年 | 331篇 |
2009年 | 319篇 |
2008年 | 518篇 |
2007年 | 477篇 |
2006年 | 484篇 |
2005年 | 442篇 |
2004年 | 445篇 |
2003年 | 461篇 |
2002年 | 423篇 |
2001年 | 415篇 |
2000年 | 411篇 |
1999年 | 339篇 |
1998年 | 142篇 |
1997年 | 114篇 |
1996年 | 87篇 |
1995年 | 85篇 |
1994年 | 81篇 |
1993年 | 88篇 |
1992年 | 243篇 |
1991年 | 247篇 |
1990年 | 197篇 |
1989年 | 179篇 |
1988年 | 183篇 |
1987年 | 158篇 |
1986年 | 148篇 |
1985年 | 146篇 |
1984年 | 120篇 |
1983年 | 110篇 |
1982年 | 89篇 |
1981年 | 59篇 |
1980年 | 57篇 |
1979年 | 90篇 |
1978年 | 85篇 |
1977年 | 62篇 |
1976年 | 58篇 |
1975年 | 49篇 |
1973年 | 58篇 |
1970年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 578 毫秒
991.
Ogino Hideki; Nakabayashi Kazuhiko; Michishita Eriko; Scherer Stephen W.; Fujii Michihiko; Suzuki Toshikazu; Ayusawa Dai 《DNA research》1998,5(4):247-250
Pieces of metaphase chromosomes prepared from mouse cells containingneo-tagged human chromosome 7 were transferred to mouse cellswith calcium phosphate to isolate G418-resistant clones. FISHanalysis revealed that the majority of them contained humanDNA at a single site on their genome. These transformants containedSTS markers mapped to various regions of chromosome 7. It isthus suggested that pieces of human chromosomes tend to assembleand integrate on the mouse genome. 相似文献
992.
We have applied atomic force microscopy (AFM) to the measurement of BAL 31 nuclease activities. BAL 31 nuclease, a species
of exonuclease, is used to remove unwanted sequences from the termini of DNA before cloning. For cutting out only the appropriate
sequences, it is important to know the nuclease properties, such as digestion speed and the distribution of the lengths of
the digested DNA. AFM was used to obtain accurate measurements on the lengths of DNA fragments before and after BAL 31 nuclease
digestion. We analyzed 4 DNAs with known number of base pairs (288, 778, 1818, and 3162 base pairs) for correlating the contour
length measured by AFM with the number of base pairs under the deposition conditions used. We used this calibration for analyzing
DNA degradation by BAL 31 nuclease from the AFM measurement of contour lengths of digested DNAs. In addition, the distribution
of digested DNA could be analyzed in more detail by AFM than by electrophoresis, because digested DNA were measured as a population
by electrophoresis, but were measured individually by AFM. These results show that AFM will be a useful new technique for
measuring nuclease activities.
Received: 8 August 1997 / Accepted: 10 September 1997 相似文献
993.
Production of trehalose synthase from a basidiomycete, Grifola frondosa, in Escherichia coli 总被引:1,自引:0,他引:1
K. Saito H. Yamazaki Y. Ohnishi S. Fujimoto E. Takahashi S. Horinouchi 《Applied microbiology and biotechnology》1998,50(2):193-198
The genomic DNA and cDNA for a gene encoding a novel trehalose synthase (TSase) catalyzing trehalose synthesis from α-d-glucose 1-phosphate and d-glucose were cloned from a basidiomycete, Grifola frondosa. Nucleotide sequencing showed that the 732-amino-acid TSase-encoding region was separated by eight introns. Consistent with
the novelty of TSase, there were no homologous proteins registered in the databases. Recombinant TSase with a histidine tag
at the NH2-terminal end, produced in Escherichia coli, showed enzyme activity similar to that purified from the original G. frondosa strain. Incubation of α-d-glucose 1-phosphate and d-glucose in the presence of recombinant TSase generated trehalose, in agreement with the enzymatic property of TSase that
the equilibrium lay far in the direction of trehalose synthesis.
Received: 12 January 1998 / Received revision: 20 February 1998 / Accepted: 20 March 1998 相似文献
994.
Suckling- and estrogen-induced prolactin release from the anterior pituitary is mediated by alpha-melanocyte stimulating hormone (alpha-MSH) secreted by the intermediate lobe of the pituitary in the rat. Melanocortin 5-receptors are expressed in the anterior pituitary and probably mediate the alpha-MSH function. In contrast, the mouse anterior pituitary does not express the receptor. To examine whether or not alpha-MSH regulates prolactin release in mice, we performed cell immunoblot assay using anterior pituitary cells from adult female mice. We found that alpha-MSH acted on mammotrophs (prolactin-secreting cells) and stimulated prolactin release in a dose dependent manner. A series of RT-PCR using oligonucleotide primer pairs specific for each subtypes of melanocortin receptors revealed that the melanocortin 3-receptor is the sole receptor expressed in the mouse anterior pituitary. These results suggest that alpha-MSH-induced prolactin release is mediated by melanocortin 3-receptors in female mice. 相似文献
995.
T Matsuguchi S Okamura T Aso K Takahashi T Sata Y Niho 《Biochemistry international》1991,23(5):979-985
We investigated the gene expression of the alpha chain of C4b-binding protein (C4bp alpha) in a variety of tissues, and in liver cell and hepatoma lines. C4bp alpha mRNA was detected in the liver, but not in the other tissues examined. The constitutive gene expression of C4bp alpha by a hepatoma line, HepG2, was significantly augmented by treatment with monocyte-conditioned medium (MoCM), 12-O-tetradecanoylphorbol-13-acetate (TPA), interleukin-6 (IL6) and tumor necrosis factor (TNF) but not by a calcium ionophore (A23187) or interleukin-1 beta (IL1 beta). 相似文献
996.
Enami Isao; Mochizuki Yasuki; Takahashi Seitaro; Kakuno Tomisaburo; Horio Takekazu; Satoh Kazuhiko; Katoh Sakae 《Plant & cell physiology》1990,31(5):725-729
Treatment of oxygen-evolving Photosystem II complexes, whichlack light-harvesting chlorophyll a/b proteins, with a seriesof disuccinimidyl esters with different chain lengths yieldeda crosslinked product which consisted of one molecule each ofthe extrinsic 33 kDa and 23 kDa proteins. In addition, crosslinkingbetween the 33 kDa protein and the chlorophyll-carrying 47 kDaprotein and between the 23 kDa and 17 kDa proteins was confirmed.Thus, the three extrinsic proteins are closely associated witheach other to form a complex which is attached to the PS IIreaction center complexes. (Received December 1, 1989; Accepted May 2, 1990) 相似文献
997.
Koichiro Harada Hideki Kubo Yoshitaka Tomigahara Kazuhiko Nishioka Junya Takahashi Mio Momose Shinichi Inoue Atsuyuki Kojima 《Bioorganic & medicinal chemistry letters》2010,20(1):272-275
The synthesis and SAR studies of 3- and 4-substituted 7-hydroxycoumarins as novel 17β-HSD3 inhibitors are discussed. The most potent compounds from this series exhibited low nanomolar inhibitory activity with acceptable selectivity versus other 17β-HSD isoenzymes and nuclear receptors. 相似文献
998.
Naoto Takahashi Hisaya Hasegawa Mami Komiyama Takehiro Ohki Yukari Yada Yasunori Koike Ryou Kawamata Yoko Honma Mariko Momoi 《Cytokine》2009,45(1):39-43
Neonatal toxic shock syndrome (TSS)-like exanthematous disease (NTED) is an emerging neonatal infectious disease caused by TSS toxin-1 (TSST-1). Although NTED and TSS are caused by the same superantigenic exotoxin, NTED is less severe than TSS. The mechanism of this reduced severity in NTED has not been elucidated. Thirteen patients with NTED were enrolled in the study. We investigated serum cytokine profile using a cytometric bead array system with a cytokine panel. Expression of Vβ2 and CD45RO in CD4+ T cells was investigated in mononuclear cells by using flowcytometry. Ten patients with other bacterial infections and eight patients without any infections were also enrolled as control groups. The mean serum level of IL-10 was 1209.9 pg/mL in patients with NTED at the time of admission into the study. The other inhibitory cytokine, IL-4, exhibited a minimum level. The high level of IL-10 rapidly decreased within 3–9 days of the onset of NTED. The cytokine profile of NTED, with its high IL-10 level, was clearly different from that of the other bacterial infections. The increased level of IL-10 seems to be related to the reduced severity of NTED. Th2 shift is not thought to be the cause of this IL-10 excretion. 相似文献
999.
This study describes complete control region sequences of mitochondrial DNA (mtDNA) from 117 Ethiopian cattle from 10 representative populations, in conjunction with the available cattle sequences in GenBank. In total, 79 polymorphic sites were detected, and these defined 81 different haplotypes. The haplotype and nucleotide diversity of Ethiopian cattle did not vary among the populations studied. All mtDNA sequences from Ethiopian cattle converged into one main maternal lineage (T1) that corresponds to African Bos taurus cattle. According to the results of this study, no zebu mtDNA haplotypes have been found in Ethiopia, where the most extensive hybridization took place on the African continent. 相似文献