全文获取类型
收费全文 | 1116篇 |
免费 | 64篇 |
国内免费 | 1篇 |
专业分类
1181篇 |
出版年
2022年 | 6篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 10篇 |
2018年 | 9篇 |
2017年 | 12篇 |
2016年 | 19篇 |
2015年 | 27篇 |
2014年 | 37篇 |
2013年 | 77篇 |
2012年 | 60篇 |
2011年 | 65篇 |
2010年 | 36篇 |
2009年 | 42篇 |
2008年 | 81篇 |
2007年 | 76篇 |
2006年 | 69篇 |
2005年 | 78篇 |
2004年 | 86篇 |
2003年 | 81篇 |
2002年 | 81篇 |
2001年 | 12篇 |
2000年 | 8篇 |
1999年 | 13篇 |
1998年 | 10篇 |
1997年 | 19篇 |
1996年 | 12篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1992年 | 10篇 |
1991年 | 12篇 |
1990年 | 9篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1967年 | 3篇 |
1963年 | 4篇 |
排序方式: 共有1181条查询结果,搜索用时 15 毫秒
11.
Hitoshi Suzuki Kimiyuki Tsuchiya Mitsuru Sakaizumi Shigeharu Wakana Susumu Sakurai 《Journal of molecular evolution》1994,38(2):107-112
An analysis by restriction endonuclease digestion of ribosomal DNA (rDNA) was carried out in natural populations of Apodemus speciosus, a field mouse that is endemic to Japan. Two restriction sites, the EcoRI (E3) and DraI (D4) sites, in the nontranscribed spacer region downstream from the gene for 28S RNA showed polymorphism within and between individuals in the populations from the Japanese main islands. By contrast, populations from the small adjoining islands which are thought to have separated from the main islands 1–2 × 104 years ago showed relatively low levels of polymorphism within and between individuals, i.e., one of the polymorphic bands in the case of each enzyme was predominant in these populations, irrespective of the variants. These results indicate that the rate of fixation of site variations depends on population size and that the direction of fixation is random. Furthermore, each polymorphic restriction site seems to be fixed independently.Correspondence to: H. Suzuki 相似文献
12.
Shinichi Kitamura Takashi Hirano Kenichi Takeo Mitsuru Mimura Kanji Kajiwara Bjrn T. Stokke Tsutomu Harada 《International journal of biological macromolecules》1994,16(6)
The conformation and dilute solution properties of (2→1)-β-d-fructan in aqueous solution were studied by gel permeation chromatography, low-angle laser light-scattering photometry, viscometry, small-angle X-ray scattering and electron microscopy. Fractions covering a broad range of weight-average molecular weights (Mw) from 1.49 × 104 to 5.29 × 106 were obtained from a native sample by ultrasonic degradation and fractional precipitation. For Mw < 4 × 104, the intrinsic viscosity [η] varies with Mw0.71, indicating that the fructan chain behaves as a random coil expanded by an excluded-volume effect in this molecular weight region. For Mw > 105, [η] exhibits an unusually weak dependence on Mw and finally becomes almost independent of molecular weight. This behaviour is interpreted in terms of a globular conformation of the high-molecular-weight fructan molecules. Small-angle X-ray-scattering measurements and electron microscopic observations support this interpretation of the values of [η] observed. 相似文献
13.
It has been generally considered that the low productivity of Leguminosae is caused by accumulation in the reproductive organs of a large amount of protein and lipid, since the biochemical costs of synthesizing these compounds is higher than that for carbohydrate. However, we report here on results which show that: the growth efficiencies (dry matter accumulated/ (dry matter accumulated + respiration)) of reproductive organs of Gramineae and Leguminosae were similar; the growth efficiency of rice in the vegetative stage was greater than that of soybean and field bean, regardless of nitrogen application rate; and when 14CO2, 14C-sucrose or 14C-asparagine were introduced to the leaf at the maturation stage, respiratory loss of the introduced 14C was greater in soybean and field bean, especially in the light, than in rice. Thus, it is assumed that the low productivity in Leguminosae is caused by a larger respiratory loss under both dark and light condition in the shoot, and not in the reproductive organs. 相似文献
14.
Kazuo Iwaki Norio Okumura Mitsuru Yamazaki 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1993,619(2)
A rapid and accurate determination of tetracycline antibiotics in human serum by reversed-phase high-performance liquid chromatography with fluorescence detection has been developed, based on protein precipitation in serum. Various reagents for precipitation were investigated, and 24% trichloroacetic acid in methanolic solution gave the maximum recovery (at least 94.3%) and interference-free chromatograms of different three tetracyclines. At a concentration of 0.5 μg/ml, the precision (relative standard deviation) ranged from 1.12 to 1.94%. In the range 0.04–10.0 μg/ml for oxytetracycline and chlorotetracycline and 0.01–10.0 μg/ml for tetracycline, linear responses were observed. The detection limits of this method were 10–35 ng/ml for all three antibiotics. The proposed method was applied to the determination of serum concentrations in subjects receiving tetracycline antibiotics. 相似文献
15.
Summary Application of an immobilized growing yeast cell system to continuous production of ethanol in high concentration (10%) was
investigated using Saccharomyces cerevisiae IFO 2363. When a medium containing 25% glucose was fed, the growth of yeast cells in gel was inhibited. The inhibitory effect
was found to be reduced by a stepwise increase in concentration of glucose in the feed medium. The stepwise operation resulted
in constant growth of cells in the gel even in the medium containing 25% glucose. By this stepwise feeding system, continuous
production of ethanol of 114 mg/ml was maintained at a retention time of 2.6 h for over 2 months and a conversion rate of
glucose to ethanol of over 95% of theoretical, was achieved. 相似文献
16.
Z H Sun K Nomura S Toraya M Ujihara N Horiba T Suda T Tsushima H Demura A Kono 《Endocrinologia japonica》1992,39(6):563-569
Adrenal computed tomographic (CT) scanning was conducted in twelve patients with Addison's disease during the clinical course. In tuberculous Addison's disease (n = 8), three of four patients examined during the first two years after disease onset had bilaterally enlarged adrenals, while one of four had a unilaterally enlarged one. At least one adrenal gland was enlarged after onset in all six patients examined during the first four years. Thereafter, the adrenal glands may atrophy bilaterally, in contrast to adrenal glands in idiopathic Addison's disease, which atrophy bilaterally from disease onset (n = 2). Adrenal calcification was a less sensitive clue in tracing pathogenesis, i.e., adrenal calcification was observed in five of eight patients with tuberculous Addison's disease, but not in idiopathic patients. Thus, adrenal CT scanning could show the etiology of Addison's disease (infection or autoimmunity) and the phase of Addison's disease secondary to tuberculosis, which may be clinically important for initiating antituberculous treatment. 相似文献
17.
Shuso Takeda Masayo Hirao-Suzuki Mitsuru Shindo Hironori Aramaki 《Current issues in molecular biology》2022,44(9):3849
Experimental evidence accumulated by our research group and others strongly suggests that (–)-xanthatin, a xanthanolide sesquiterpene lactone, exhibits anti-proliferative effects on human breast cancer cells (in vitro) as well as anti-tumor effects in experimental animals (in vivo). In cancer biology, it is now critically important for anti-cancer agents to selectively target cancer stem cells (CSCs) in order to overcome cancer therapeutic resistance and recurrence. However, it has not yet been established whether (–)-xanthatin abrogates the formation of breast CSCs. In the present study, we utilized chemically synthesized pure (–)-xanthatin and a culture system to obtain mammospheres from human breast cancer MCF-7 cells, which are a CSC-enriched population. We herein demonstrated for the first time that (–)-xanthatin exhibited the ability to kill mammospheres, similar to salinomycin, an established selective killer of CSCs. A possible anti-proliferative mechanism toward mammospheres by (–)-xanthatin is discussed. 相似文献
18.
19.
El-Kabbani O Darmanin C Schneider TR Hazemann I Ruiz F Oka M Joachimiak A Schulze-Briese C Tomizaki T Mitschler A Podjarny A 《Proteins》2004,55(4):805-813
The X-ray structures of human aldose reductase holoenzyme in complex with the inhibitors Fidarestat (SNK-860) and Minalrestat (WAY-509) were determined at atomic resolutions of 0.92 A and 1.1 A, respectively. The hydantoin and succinimide moieties of the inhibitors interacted with the conserved anion-binding site located between the nicotinamide ring of the coenzyme and active site residues Tyr48, His110, and Trp111. Minalrestat's hydrophobic isoquinoline ring was bound in an adjacent pocket lined by residues Trp20, Phe122, and Trp219, with the bromo-fluorobenzyl group inside the "specificity" pocket. The interactions between Minalrestat's bromo-fluorobenzyl group and the enzyme include the stacking against the side-chain of Trp111 as well as hydrogen bonding distances with residues Leu300 and Thr113. The carbamoyl group in Fidarestat formed a hydrogen bond with the main-chain nitrogen atom of Leu300. The atomic resolution refinement allowed the positioning of hydrogen atoms and accurate determination of bond lengths of the inhibitors, coenzyme NADP+ and active-site residue His110. The 1'-position nitrogen atom in the hydantoin and succinimide moieties of Fidarestat and Minalrestat, respectively, form a hydrogen bond with the Nepsilon2 atom of His 110. For Fidarestat, the electron density indicated two possible positions for the H-atom in this bond. Furthermore, both native and anomalous difference maps indicated the replacement of a water molecule linked to His110 by a Cl-ion. These observations suggest a mechanism in which Fidarestat is bound protonated and becomes negatively charged by donating the proton to His110, which may have important implications on drug design. 相似文献
20.
Endo K Takino T Miyamori H Kinsen H Yoshizaki T Furukawa M Sato H 《The Journal of biological chemistry》2003,278(42):40764-40770
The transmembrane heparan sulfate proteoglycan syndecan-1 was identified from a human placenta cDNA library by the expression cloning method as a gene product that interacts with membrane type matrix metalloproteinase-1 (MT1-MMP). Co-expression of MT1-MMP with syndecan-1 in HEK293T cells promoted syndecan-1 shedding, and concentration of cell-associated syndecan-1 was reduced. Treatment of cells with MMP inhibitor BB-94 or tissue inhibitor of MMP (TIMP)-2 but not TIMP-1 interfered with the syndecan-1 shedding promoted by MT1-MMP expression. In contrast, syndecan-1 shedding induced by 12-O-tetradecanoylphorbol-13-acetate treatment was inhibited by BB-94 but not by either TIMP-1 or TIMP-2. Shedding of syndecan-1 was also induced by MT3-MMP but not by other MT-MMPs. Recombinant syndecan-1 core protein was shown to be cleaved by recombinant MT1-MMP or MT3-MMP preferentially at the Gly245-Leu246 peptide bond. HT1080 fibrosarcoma cells stably transfected with the syndecan-1 cDNA (HT1080/SDC), which express endogenous MT1-MMP, spontaneously shed syndecan-1. Migration of HT1080/SDC cells on collagen-coated dishes was significantly slower than that of control HT1080 cells. Treatment of HT1080/SDC cells with BB-94 or TIMP-2 induced accumulation of syndecan-1 on the cell surface, concomitant with further retardation of cell migration. Substitution of Gly245 of syndecan-1 with Leu significantly reduced shedding from HT1080/SDC cells and cell migration. These results suggest that the shedding of syndecan-1 promoted by MT1-MMP through the preferential cleavage of Gly245-Leu246 peptide bond stimulates cell migration. 相似文献