全文获取类型
收费全文 | 4357篇 |
免费 | 237篇 |
国内免费 | 2篇 |
出版年
2022年 | 14篇 |
2021年 | 33篇 |
2020年 | 20篇 |
2019年 | 29篇 |
2018年 | 50篇 |
2017年 | 32篇 |
2016年 | 71篇 |
2015年 | 112篇 |
2014年 | 122篇 |
2013年 | 231篇 |
2012年 | 251篇 |
2011年 | 218篇 |
2010年 | 121篇 |
2009年 | 165篇 |
2008年 | 244篇 |
2007年 | 256篇 |
2006年 | 219篇 |
2005年 | 233篇 |
2004年 | 243篇 |
2003年 | 252篇 |
2002年 | 248篇 |
2001年 | 131篇 |
2000年 | 106篇 |
1999年 | 118篇 |
1998年 | 72篇 |
1997年 | 64篇 |
1996年 | 71篇 |
1995年 | 51篇 |
1994年 | 36篇 |
1993年 | 54篇 |
1992年 | 66篇 |
1991年 | 78篇 |
1990年 | 67篇 |
1989年 | 48篇 |
1988年 | 61篇 |
1987年 | 54篇 |
1986年 | 42篇 |
1985年 | 49篇 |
1984年 | 30篇 |
1983年 | 34篇 |
1982年 | 21篇 |
1981年 | 25篇 |
1980年 | 28篇 |
1979年 | 21篇 |
1978年 | 14篇 |
1977年 | 6篇 |
1976年 | 18篇 |
1975年 | 11篇 |
1974年 | 8篇 |
1972年 | 8篇 |
排序方式: 共有4596条查询结果,搜索用时 125 毫秒
1.
2.
3.
Circulating tumor cells (CTCs), shed from primary tumors and disseminated into peripheral blood, are playing a major role in metastasis. Even after isolation of CTCs from blood, the target cells are mixed with a population of other cell types. Here, we propose a new method for analyses of cell mixture at the single-cell level using a microfluidic device that contains arrayed electroactive microwells. Dielectrophoretic (DEP) force, induced by the electrodes patterned on the bottom surface of the microwells, allows efficient trapping and stable positioning of single cells for high-throughput biochemical analyses. We demonstrated that various on-chip analyses including immunostaining, viability/apoptosis assay and fluorescent in situ hybridization (FISH) at the single-cell level could be conducted just by applying specific reagents for each assay. Our simple method should greatly help discrimination and analysis of rare cancer cells among a population of blood cells. 相似文献
4.
5.
Summary An activated carbon column was utilized for the synthesis of disaccharides by use of a reversed hydrolysis activity of an immobilized -galactosidase column in order to shift the equilibrium to the direction of condensation. The yields of lactulose and allo-lactulose from galactose and fructose, and N-acetyl lactosamine and N-acetyl allolactosamine from galactose and N-acetyl glucosamine, were 11.3% and 10.0%, respectively. 相似文献
6.
Ogawa Masahiro; Kumamaru Toshihiro; Satoh Hikaru; Iwata Nobuo; Omura Takeshi; Kasai Zenzaburo; Tanaka Kunisuke 《Plant & cell physiology》1987,28(8):1517-1527
Protein body type one (PB-I) was isolated and purified fromdeveloping rice grain by a combination of sucrose density gradientcentrifugation and treatment with pepsin. SDS-PAGE analysisshowed that isolated PB-I contains several polypeptide groups,the largest having an apparent molecular size of 13 kDa andtwo smaller ones of 10 kDa and 16 kDa. The 13-kDa group wasfound to be composed of two polypeptides of slightly differentmolecular sizes, 13a (larger component) and 13b (smaller component).Most of the 13a and 13b polypeptides were shown to be largelyprolamins, although there were also some salt- and alcohol-insolublepolypeptides with an apparent molecular size of 13 kDa. It wasconcluded that PB-I is the accumulation site of rice prolamin.It was further estimated that the protein amount in PB-I accountedfor about 20% of the total protein of rice endosperm. (Received March 20, 1987; Accepted September 8, 1987) 相似文献
7.
The effects of di(2-ethylhexyl)phthalate, a typical peroxisomal proliferator, on the activities of key enzymes in the glycerophospholipid synthetic pathway and the incorporation of lipid precursors into liver lipids in vitro were studied periodically in rats. When di(2-ethylhexyl)phthalate was fed at the 1% level to rats, glycerol-3-phosphate acyltransferase activity increased 2-3-fold in liver homogenates and microsomes in 2-4 days. The specific activity of microsomal CTP:phosphocholine cytidylyltransferase increased by 1.5-fold, whereas the cytosolic activity was depressed. The microsomal CDPcholine:diacylglycerol cholinephosphotransferase specific activity decreased, whereas the activity in the homogenates increased, suggesting the proliferation of the hepatic endoplasmic reticulum in di(2-ethylhexyl)phthalate-treated rats. The incorporation of [1(3)-3H]glycerol or [1-14C]acetate into liver phospholipids in vitro increased in 2 days and stayed at a high level up to 12 days. The present study confirmed that di(2-ethylhexyl)phthalate induced an enhancement of phospholipid synthesis in the liver. The increase in hepatic phospholipid synthesis by this drug is presumably linked to the proliferation of peroxisomes and other intracellular membranes. 相似文献
8.
A simple and rapid method for studying optical anisotropic properties of liposomes was proposed. Intensities of transmitted light through one spherical liposome of dipalmitoylphosphatidylcholine placed between two polarizers were measured at various wavelengths by a microscopic spectrophotometer. Large increases in the intensities were observed at the prephase-transition temperature, which were caused by an increase in the birefringence of the multilayer of the liposome. The birefringence values obtained from the intensity data were about 0.020 below the pretransition temperature and 0.028 above that temperature. These values are in good agreement with the results reported for the plane samples in which lipid bilayers are stacked. The obtained values of the birefringence were far lower than the values estimated from polarizabilities. This lower birefringence is attributed to disordering of the tilt direction in the multilayer. The degree of order of the liposome multilayers calculated from the birefringence increased by 38% at the pretransition. This simple method is applicable to the study of the multilayer structure of liposomes in water. 相似文献
9.
Abstract Biovar A strains of Fusobacterium necrophorum exhibited high hydrophobicity when examined by the method of Rosenberg et al. Biovar B strains showed a lower cell surface hydrophobicity than biovar A strains. Biovar B strains were divided into 2 groups according to their hydrophobic activity. The strains of biovar A and the first group of biovar B were increasingly removed from aqueous phase to octane phase by increasing the volume of octane, but the turbidity of the second group of biovar B was not significantly affected. The hydrophobicity of biovar A strains decreased on heating at 60 and 100°C for 30 min. 相似文献
10.
Cell- and tissue-specific monoclonal antibodies in eggs and embryos of the ascidian Halocynthia roretzi 总被引:4,自引:0,他引:4
To obtain specific immunological probes for studying molecular mechanisms involved in the early embryonic development of ascidians, we have produced monoclonal antibodies directed against a homogenate of larvae of the ascidian Halocynthia roretzi. Among these, we have screened monoclonal antibodies that specifically recognize cells and/or tissues of the embryo. Characterization of six epidermis-specific monoclonal antibodies (including larval tunic-specific and larval fin-specific), three muscle-specific antibodies, two endoderm-specific antibodies, one notochord-specific antibody and two monoclonal antibodies that specifically recognize trunk-lateral cells suggests that these monoclonal antibodies may be useful as markers for analysing molecular mechanisms involved in specification of these cells. Seven monoclonal antibodies characteristically stain intercellular materials of the developing embryo and may therefore be valid for studying cellular construction of the embryo. Furthermore, monoclonal antibodies that recognize components of follicle cells, perivitelline space and sperm have also been established. 相似文献