全文获取类型
收费全文 | 2365篇 |
免费 | 171篇 |
国内免费 | 124篇 |
专业分类
2660篇 |
出版年
2024年 | 5篇 |
2023年 | 25篇 |
2022年 | 70篇 |
2021年 | 127篇 |
2020年 | 91篇 |
2019年 | 87篇 |
2018年 | 76篇 |
2017年 | 67篇 |
2016年 | 109篇 |
2015年 | 139篇 |
2014年 | 159篇 |
2013年 | 198篇 |
2012年 | 200篇 |
2011年 | 183篇 |
2010年 | 116篇 |
2009年 | 94篇 |
2008年 | 114篇 |
2007年 | 111篇 |
2006年 | 92篇 |
2005年 | 68篇 |
2004年 | 65篇 |
2003年 | 57篇 |
2002年 | 61篇 |
2001年 | 39篇 |
2000年 | 37篇 |
1999年 | 31篇 |
1998年 | 13篇 |
1997年 | 16篇 |
1996年 | 17篇 |
1995年 | 17篇 |
1994年 | 12篇 |
1993年 | 12篇 |
1992年 | 23篇 |
1991年 | 17篇 |
1990年 | 15篇 |
1989年 | 9篇 |
1988年 | 13篇 |
1987年 | 11篇 |
1986年 | 12篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1980年 | 5篇 |
1975年 | 4篇 |
1973年 | 4篇 |
1971年 | 3篇 |
1969年 | 3篇 |
1968年 | 2篇 |
1967年 | 2篇 |
排序方式: 共有2660条查询结果,搜索用时 15 毫秒
41.
Junpei Zhou Qian Wu Rui Zhang Minghe Mo Xianghua Tang Junjun Li Bo Xu Junmei Ding Qian Lu Zunxi Huang 《Folia microbiologica》2014,59(5):423-431
A glycosyl hydrolase family 10 endoxylanase from Bacillus sp. HJ14 was grouped in a separated cluster with another six Bacillus endoxylanases which have not been characterized. These Bacillus endoxylanases showed less than 52 % amino acid sequence identity with other endoxylanases and far distance with endoxylanases from most microorganisms. Signal peptide was not detected in the endoxylanase. The endoxylanase was expressed in Escherichia coli BL21 (DE3), and the purified recombinant enzyme (rXynAHJ14) was characterized. rXynAHJ14 was apparent optimal at 62.5 °C and pH 6.5 and retained more than 55 % of the maximum activity when assayed at 40–75 °C, 23 % at 20 °C, 16 % at 85 °C, and even 8 % at 0 °C. Half-lives of the enzyme were more than 60 min, approximately 25 and 4 min at 70, 75, and 80 °C, respectively. The enzyme exhibited more than 62 % xylanase activity and stability at the concentration of 3–30 % (w/v) NaCl. No xylanase activity was lost after incubation of the purified rXynAHJ14 with trypsin and proteinase K at 37 °C for 60 min. Different components of oligosaccharides were detected in the time-course hydrolysis of beechwood xylan by the enzyme. During the simulated intestinal digestion phase in vitro, 11.5–19.0, 15.3–19.0, 21.9–27.7, and 28.2–31.2 μmol/mL reducing sugar were released by the purified rXynAHJ14 from soybean meal, wheat bran, beechwood xylan, and rapeseed meal, respectively. The endoxylanase might be an alternative for potential applications in the processing of sea food and saline food and in aquaculture as agastric fish feed additive. 相似文献
42.
DNA polymerase delta, the key enzyme for eukaryotic chromosomal replication, has been well characterized as consisting of a core enzyme of a 125 kDa catalytic subunit and a smaller 50 kDa subunit. However, less is known about the other proteins that may comprise additional subunits or participate in the macromolecular protein complex that is involved in chromosomal DNA replication. In this study, the properties of calf thymus pol delta preparations isolated by immunoaffinity chromatography were investigated. It is demonstrated for the first time using highly purified preparations that the pol delta heterodimer is associated with other polypeptides in high-molecular weight species that range from 260000 to >500000 in size, as determined by FPLC gel filtration. These preparations are associated with polypeptides of ca. 68-70, 34, 32, and 25 kDa. Similar findings were revealed with glycerol gradient ultracentrifugation. The p68 polypeptide was shown to be a PCNA binding protein by overlay methods with biotinylated PCNA. Protein sequencing of the p68, p34, and p25 polypeptide bands revealed sequences that correspond to the hypothetical protein KIAA0039. KIAA0039 displays a small but significant degree of homology to Schizosaccharomyces pombe Cdc27, which, like Saccharomyces cerevisiae Pol32p, has been described as the third subunit of yeast pol delta. These studies provide evidence that p68 is a subunit of pol delta. In addition, the p68-70 and p32 polypeptides were found to be derived from the 70 and 32 kDa subunits of RPA, respectively. 相似文献
43.
Lin X Peng P Cheng L Chen S Li K Li ZY Mo YH Zhou Z Li M 《Differentiation; research in biological diversity》2012,83(1):1-9
An intra-myocardial injection of a cardiogenic factor (cardiogenin) was reported to induce myocardial regeneration of exogenous mesenchymal stem cell (MSCs) origin. In this study, replacement of the dangerous intra-myocardial injection with a safe method and whether the endogenous MSCs contribute to the cardiogenin-mediated myocardial regeneration were investigated. Bone marrow transplantation with labeled MSCs was performed in rats, which were subsequently subject to a permanent ligation of left anterior descending coronary artery one week after the transplantation. The rats were then treated with the cardiogenin through oral administration for 2 weeks. We not only demonstrated the substantial therapeutic effects of cardiogenin on myocardial infarction through an oral administration, but also provided direct evidences that the bone marrow derived endogenous MSCs are the major cellular source of the regenerating myocardium. Preliminary mechanistic studies suggested that miR-9 and its target E-cadherin may be required for intercalated disc formation. 相似文献
44.
Liu HA Sun HX Mo XM Li SY Li XY Zhang G Lu L 《Indian journal of experimental biology》2012,50(5):313-319
We have found and synthesized a trapping ligand peptide H22-LP (the conservative sequence is NAHCALL) from a random phage library according to the broad-spectrum trapping receptor H22, which derived from the residue 14-35 near the N-terminal region of receptor US28 on HCMV. In this study, we will evaluate its potential as an efficient antagonist of US28 and the anti-virus activity, acting as a broad spectrum chemokine receptors antagonist. Stable expression of US28 and ORF74 in NIH/3T3 cells were successfully constructed in vitro. Flow cytomety was used to determine the concentration of Ca2+ induced by H22-LP, and the binding of H22-LP and US28 was confirmed by enzyme-linked immunosorbent assay (ELISA). Antivirus activity of H22-LP on HCMV and KSHV was evaluated by anti-virus experiments. Our data suggest that H22-LP is an effectual antagonist of receptor US28 of HCMV and ORF74 of KSHV in the transfection assay, and it has potential to inhibit infection of HCMV and KSHV. These results provide support for the development of anti-virus strategies based on targeted inhibiting the infection of herpesvirus. 相似文献
45.
Krueger AC Madigan DL Green BE Hutchinson DK Jiang WW Kati WM Liu Y Maring CJ Masse SV McDaniel KF Middleton TR Mo H Molla A Montgomery DA Ng TI Kempf DJ 《Bioorganic & medicinal chemistry letters》2007,17(8):2289-2292
Substituted 1-hydroxy-4,4-dialkyl-3-oxo-3,4-dihydronaphthalene benzothiadiazine derivatives were investigated as inhibitors of genotype 1 HCV polymerase. Structure-activity relationship patterns for this class of compounds are discussed. It was found that the saturated alkane dialkyl units provided the most active analogs. 相似文献
46.
朱砂叶螨对三种杀螨剂的抗性选育与抗性风险评估 总被引:11,自引:3,他引:11
为评价朱砂叶螨Tetranychus cinnabarinus对3种杀螨剂的抗性风险,在实验室抗性品系选育基础上,应用数量遗传学中的域性状分析法,研究了朱砂叶螨北碚种群对甲氰菊酯、阿维菌素和哒螨灵3种杀螨剂的抗性现实遗传力,并对3种药剂在不同杀死率下抗性发展的速率进行了预测。结果表明:分别单一连续汰选16代后,朱砂叶螨对甲氰菊酯、阿维菌素的抗性倍数分别达26.54和4.51倍,对哒螨灵表现为敏感性降低(抗性倍数为1.16倍);朱砂叶螨对甲氰菊酯、阿维菌素和哒螨灵的抗性现实遗传力分别为0.2472,0.1519和0.0160。在室内选择条件下,杀死率为50%~90%时,要获得10倍抗性,甲氰菊酯仅需要13~6代,阿维菌素需要约21~10代;哒螨灵需要约197~89代;在田间选择,三种药剂都将需要更长的时间。抗性筛选16代结果表明,抗性风险较高的是菊酯类的甲氰菊酯,其次是生物源农药阿维菌素,杂环类的哒螨灵抗性风险较小。试验结果可为朱砂叶螨抗性治理提供参考。 相似文献
47.
48.
49.
The heart as an endocrine organ 总被引:1,自引:0,他引:1
Modern data on atrial natriuretic factor (ANF) are presented. Synthesis of this factor, its storage and release from cardiac atria are described. The role of ANF in the body fluid volume regulation and blood pressure homeostasis is discussed. ANF is regarded as a circulating hormone. 相似文献
50.
Liu Yuan Luo Cong Zhang Xiu-Juan Lu Xin-Xi Yu Hai-Xia Xie Xiao-Jie Fan Zhi-Yi Mo Xiao He Xin-Hua 《Plant Cell, Tissue and Organ Culture》2020,143(1):219-228
Plant Cell, Tissue and Organ Culture (PCTOC) - CONSTANS (CO)/CONSTANS-like (COL) genes play an important role in the photoperiodic flowering pathway. However, the functional roles of the CO/COL... 相似文献