全文获取类型
收费全文 | 17397篇 |
免费 | 1608篇 |
国内免费 | 1782篇 |
专业分类
20787篇 |
出版年
2024年 | 66篇 |
2023年 | 283篇 |
2022年 | 630篇 |
2021年 | 991篇 |
2020年 | 696篇 |
2019年 | 832篇 |
2018年 | 795篇 |
2017年 | 608篇 |
2016年 | 780篇 |
2015年 | 1157篇 |
2014年 | 1350篇 |
2013年 | 1359篇 |
2012年 | 1656篇 |
2011年 | 1457篇 |
2010年 | 837篇 |
2009年 | 832篇 |
2008年 | 912篇 |
2007年 | 799篇 |
2006年 | 622篇 |
2005年 | 548篇 |
2004年 | 520篇 |
2003年 | 442篇 |
2002年 | 406篇 |
2001年 | 299篇 |
2000年 | 260篇 |
1999年 | 229篇 |
1998年 | 168篇 |
1997年 | 145篇 |
1996年 | 138篇 |
1995年 | 102篇 |
1994年 | 117篇 |
1993年 | 80篇 |
1992年 | 98篇 |
1991年 | 101篇 |
1990年 | 61篇 |
1989年 | 46篇 |
1988年 | 48篇 |
1987年 | 31篇 |
1986年 | 41篇 |
1985年 | 37篇 |
1984年 | 22篇 |
1983年 | 28篇 |
1982年 | 20篇 |
1980年 | 14篇 |
1979年 | 14篇 |
1977年 | 11篇 |
1975年 | 13篇 |
1974年 | 12篇 |
1973年 | 11篇 |
1970年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
The ubiquitin-proteasome system (UPS) in plants, like in other eukaryotes, targets numerous intracellular regulators and thus modulates almost every aspect of growth and development. The well-known and best-characterized outcome of ubiquitination is mediating target protein degradation via the 26S proteasome, which represents the major selective protein degradation pathway conserved among eukaryotes. In this review, we will discuss the molecular composition, regulation and function of plant UPS, with a major focus on how DELLA protein degradation acts as a key in gibberellin signal transduction and its implication in the regulation of plant growth. 相似文献
142.
Repression of microRNA‐382 inhibits glomerular mesangial cell proliferation and extracellular matrix accumulation via FoxO1 in mice with diabetic nephropathy 下载免费PDF全文
143.
The development of acellular pertussis vaccines has raised a number of issues relevant to the control of these products. Of particular importance is the need for robust and accurate in vitro assays for the antigen content of the vaccines which might contain up to five different antigen components, each of which needs to be independently assayed. This paper describes a simple method for the quantification of three component antigens. Because relatively high doses of purified antigens are used in those preparations, the elimination of residual toxicity is a major concern. This is achieved by genetic modification of chemical treatment. The latter results in modification of the immunological reactivity of the antigens making direct assay by such methods as ELISA ineffective. A single radial diffusion technique using polyclonal antisera for the assay of pertussis toxoid (PTxd), chemically treated filamentous haemagglutinin (FHA) and pertactin (69 kDa) has been developed. The method uses low concentrations of antisera, allowing accurate and reproducible quantification of antigen content as low as 25 microg/ml of protein for pertussis toxoid and filamentous haemagglutinin and 5 microg/ml for pertactin. Since by the addition of detergent, diffusible subunits are produced irrespective of the original physical state of the antigens, the assay is suitable for assay of these antigens after detoxification/or stabilization by chemical treatment and is able to determine the differences between preparations which have the same protein concentration but different antigenic contents. This provides a means for assuring the consistency of the antigens after detoxification/or chemical stabilization which could be used as an in-process control method for acellular pertussis vaccines. 相似文献
144.
145.
柯萨奇B组病毒感染与胰岛素依赖型糖尿病关系的研究 总被引:1,自引:0,他引:1
探讨柯萨奇B组病毒(CBV)感染与胰岛素依赖型糖尿病之间的关系。用PT-PCR方法检测38例IDDM患者外周血中CBV-RNA,同时用ELISA法测定血清中CBV特异性IgM。结果显示,病例组38例患者外周血CBV-RNA阳性率为42.10%,血清中CBV-IgM阳性率为36.84%。对照组的阳性率分别为7.5%和5%。两组比较有显著性差别(P<0.05)。说明胰岛素依赖型糖尿病与柯萨奇B组病毒感染有关。 相似文献
146.
The oligosaccharide on alpha-subunit loop 2 (alpha 2) is needed for full glycoprotein hormone efficacy. Efforts to prepare glycoprotein hormone antagonists usually involve removing the alpha 2 oligosaccharide and are hampered by its requirement for efficient heterodimer secretion from mammalian cells. Here we show that hormones lacking this oligosaccharide can be produced by treating them at low pH to dissociate the heterodimer and permitting the subunits to re-associate in the presence of peptide N-glycosidase F (PNGase F). Re-assembly of human choriogonadotropin, human follitropin, and bovine lutropin occurred rapidly and efficiently following removal of the alpha 2 oligosaccharide by PNGase F. Consequently, virtually all heterodimers formed in the presence of this enzyme lacked this oligosaccharide. These findings support the notion that heterodimer assembly in vitro occurs by a threading mechanism that is impeded by the presence of the alpha 2 oligosaccharide. This procedure should facilitate the study of glycoprotein hormone structure and function. 相似文献
147.
Gong X Xie T Yu L Hesterberg M Scheide D Friedrich T Yu CA 《The Journal of biological chemistry》2003,278(28):25731-25737
An azido-ubiquinone derivative, 3-azido-2-methyl-5-methoxy[3H]-6-decyl-1,4-benzoquinone ([3H]azido-Q), was used to study the ubiquinone/protein interaction and to identify the ubiquinone-binding site in Escherichia coli NADH:ubiquinone oxidoreductase (complex I). The purified complex I showed no loss of activity after incubation with a 20-fold molar excess of [3H]azido-Q in the dark. Illumination of the incubated sample with long wavelength UV light for 10 min at 0 degrees C caused a 40% decrease of NADH:ubiquinone oxidoreductase activity. SDS-PAGE of the complex labeled with [3H]azido-Q followed by analysis of the radioactivity distribution among the subunits revealed that subunit NuoM was heavily labeled, suggesting that this protein houses the Q-binding site. When the [3H]azido-Q-labeled NuoM was purified from the labeled reductase by means of preparative SDS-PAGE, a 3-azido-2-methyl-5-methoxy-6-decyl-1,4-benzoquinone-linked peptide, with a retention time of 41.4 min, was obtained by high performance liquid chromatography of the protease K digest of the labeled subunit. This peptide had a partial NH2-terminal amino acid sequence of NH2-VMLIAILALV-, which corresponds to amino acid residues 184-193 of NuoM. The secondary structure prediction of NuoM using the Toppred hydropathy analysis showed that the Q-binding peptide overlaps with a proposed Q-binding motif located in the middle of the transmembrane helix 5 toward the cytoplasmic side of the membrane. Using the PHDhtm hydropathy plot, the labeled peptide is located in the transmembrane helix 4 toward the periplasmic side of the membrane. 相似文献
148.
149.
150.