全文获取类型
收费全文 | 993篇 |
免费 | 65篇 |
出版年
2022年 | 9篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 6篇 |
2017年 | 8篇 |
2016年 | 16篇 |
2015年 | 20篇 |
2014年 | 27篇 |
2013年 | 52篇 |
2012年 | 56篇 |
2011年 | 61篇 |
2010年 | 32篇 |
2009年 | 23篇 |
2008年 | 57篇 |
2007年 | 60篇 |
2006年 | 76篇 |
2005年 | 51篇 |
2004年 | 45篇 |
2003年 | 42篇 |
2002年 | 63篇 |
2001年 | 42篇 |
2000年 | 33篇 |
1999年 | 40篇 |
1998年 | 7篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1993年 | 5篇 |
1992年 | 18篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 18篇 |
1988年 | 14篇 |
1987年 | 7篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 8篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1970年 | 3篇 |
排序方式: 共有1058条查询结果,搜索用时 187 毫秒
21.
Superficial cells of the oral mucosal epithelium in the carp and the cytoskeleton of the epithelial cells are examined by scanning and transmission electron microscopy. Microridges are formed on the surface of the epithelium. Epithelial cells contain two types of vesicles: mucous secretory vesicles and coated vesicles. Most of the mucous vesicles are situated in the center of the cell near the Golgi apparatus. In freeze-fracture replicas, intramembranous particles are abundant in the membranes of the secretory vesicles but rare in the apical plasma membrane. Coated vesicles are situated in the apical and subapical cytoplasm. A great number of thick filaments, considered to be keratin filaments, run randomly throughout the cell to form a meshwork. Thick filaments, which are sparse in the central cytoplasm, are connected to the membranes of the secretory vesicles and other membranous organelles. A layer of closely packed thin filaments, considered to be actin filaments, is found just beneath the apical plasma membrane. Microtubules also occur in the apical cytoplasm and run almost parallel to the cell surface. Both kinds of vesicles are connected to the thin and thick filaments. Their functional significance in the regulation of membrane at the free surface is discussed. 相似文献
22.
Sonodynamic therapy, a promising new approach to cancer treatment, is based on synergistic cell killing by combination of certain drugs (sonosensitizers) and ultrasound. Although the mechanism of sonodynamic action is not understood, the role of free radicals produced from sonosensitizers by ultrasound is implicated. In this work, we studied formation of free radicals during the decomposition of several water-soluble azo compounds by 50 kHz ultrasound in aqueous solutions. Using the spin trap 3, 5-dibromo-4-nitrosobenzene sulfonate (DBNBS) tertiary carbon-centered radicals from 2, 2'-azobis (N,N'-dimethyl-eneisobutyramidine) dihydrochloride (VA-044), 2-(carbamoylazo)-isobutyronitrile (V-30), and 2, 2'-azobis (2-amidinopropane) dihydrochloride (AAPH) and CH3 radicals from 1, 1'-azobis (N,N'-dimethylformamide) (ADMF) were detected in argonsaturated solutions and the corresponding oxygen-centered radicals (alkoxyl and peroxyl) from VA-044, V-30, and AAPH were identified using the spin trap 5, 5'-dimethyl-l-pyrroline-N-oxide (DMPO) in aerated sonicated solutions. No free radicals from 4, 4'-dihydroxyazobenzene-3, 3'-dicarboxylic acid, disodium salt (DHAB) could be found in either system. While VA-044 and AAPH could also be readily decomposed by heat (42.5°C and 80°C), V-30 decomposition only occurred in the ultrasound-exposed solutions. The most likely mechanism of decomposition of azo compounds by ultrasound is their thermolysis in the heated shell of the liquid surrounding ca vita ting bubbles driven by ultrasound and/or by pyrolysis inside these bubbles. Experiments using scavengers of ·OH and ·H, which are produced by sonolysis in aqueous solutions, demonstrated that these radicals are not involved in the ultrasound-mediated radical production from the azo compounds. Due to the known cytotoxic potential of free radicals produced from azo compounds, the use of these compounds as ultrasound sensitizers appears to be a promising approach for sonodynamic cell killing. 相似文献
23.
Alternative splicing and genomic structure of the AML1 gene involved in acute myeloid leukemia. 总被引:17,自引:0,他引:17
下载免费PDF全文
![点击此处可从《Nucleic acids research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
H Miyoshi M Ohira K Shimizu K Mitani H Hirai T Imai K Yokoyama E Soeda M Ohki 《Nucleic acids research》1995,23(14):2762-2769
24.
High level of GUS gene expression driven by pollen-specific promoters in electroporated lily pollen protoplasts 总被引:8,自引:0,他引:8
Gene constructs that contained the -glucuronidase (GUS) gene under the control of a pollen-specific Zm13 promoter from maize and a LAT52 promoter from tomato were introduced by electroporation into pollen protoplasts isolated from bicellular pollen grains of Lilium longiflorum. After 20 h in culture, the pollen protoplasts exhibited the apparent expression of GUS in a fluorometric assay. The GUS activity induced under the control of the Zm13 promoter was over 10 000 times higher than activity in the control (with no DNA or without electroporation). By contrast, the GUS gene was nearly silent in the lily microspore protoplasts and generative cell protoplasts. The GUS activity driven by the Zm13 and LAT52 promoters was also detected by a cytochemical assay. The frequency of blue-staining pollen protoplasts was about 70% in the case of the Zm13 promoter. The efficiency of gene transfer by electroporation was much higher than by particle bombardment. This protoplast-specific electroporation system is suitable for rapid and reliable examination of pollen-specific promoters, being as good as the particle bombardment system. 相似文献
25.
A process for the bacterial oxidation of dulcitol to d-tagatose has been developed. The strain Arthrobacter globiformis ST48 used in this fermentation was isolated from soil. The yield of d-tagatose accumulated in the medium from dulcitol was as high as 85%. About 14 g of d-tagatose crystals was isolated from 1 liter of 2% dulcitol medium. 相似文献
26.
Synthetic thyrotropin-releasing hormone (TRH) tartrate monohydrate was administered by rapid intravenous injection to nine normal males. Plasma thyroid-stimulating hormone (TSH), luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were measured before and at selected periods after TRH injection. The mean plasma TSH value immediately prior to TRH injection was 3.5 muU/ml and the level 15 min after injection was 14.8 muU/ml. The mean plasma LH value immediately prior to TRH injection was 8.0 mIU/ml and the level 15 min after injection was 15.0 mIU/ml. The latter elevation was statistically significant (p less than 0.01), although it was just above the upper normal range. The mean plasma FSH value immediately prior to TRH injecion was 7.7 mIU/ml, and a significant difference was not observed after TRH administration. These results revealed that synthetic TRH tartrate monohydrate influenced the release of LH from the anterior pituitary. 相似文献
27.
Kozo Hayashi Kazuo Yamada Keiji Ohe Akima Miyoshi Takashi Kawasaki 《生物化学与生物物理学报:生物膜》1980,596(3):414-419
The effect of amytal on energy metabolism and acid secretion in an isolated gastric mucosa of the guinea-pig were studied. Determination of adenine nucleotides, creatine phosphate, pyruvate and lactate in the gastric mucosa showed that amytal depressed the levels of ATP, creatine phosphate and energy charge with elevation of the AMP and pyruvate levels. This treatment inhibited concomitantly acid secretion and active chloride transport detected by short circuit current. The addition of menadione with ascorbate to the medium in the presence of amytal partially restored ATP and energy charge levels and also induced a partial recovery of acid secretion and active chloride transport. These results suggest that ATP is a direct energy donor for acid secretion in the gastric mucosa of the guinea-pig. 相似文献
28.
Experimental rat chimeras were produced by aggregation of eight-cell embryos from two inbred strains, ACI/Hkm and WKAH/Hkm, which differ from each other in their major histocompatibility complexes and coat colors, and their mosaicism was analyzed. The existence of the isozyme Es-1, a serum cholinesterase specifically produced by WKAH-derived cells, and the agouti coat color due to ACI cells, indicated that all of the rats analyzed were unequivocal chimeras. The proportion of ACI cells in the red blood cell populations of the chimeras varied from 45% to 98%, as determined with a fluorescence-activated cell sorter and a monoclonal antibody against class I (RT1) antigen. Digital analysis of the coat color revealed that the proportion of the ACI type of coat color ranged from 72% to 98% in these chimeric rats. Each phenotype expressed in the coat color was complex and varied in size. The ratios of red blood cells and the coat color inclined toward the ACI type of cell population. Conversely, the rate of the WKAH-cell-type population was less than 50%. A breeding test disclosed chimerism of germ cells in two chimeric rats, and there were more pups with agouti coats than with albino coats. Taken together, it was shown in most of the phenotypes analyzed that the ACI type of cells was predominant in all of the chimeric rats. We discuss the possible causes for this unbalanced distribution in the rats. 相似文献
29.
A convenient and nonradioactive method for DNA hybridization tests termed the "Universal probe system" has been developed. This method is based on the principle of sandwich hybridization. This system consists of two single-stranded DNA probes (a primary probe and a biotin-labeled secondary probe). The primary probe is prepared from a chimeric phage-plasmid vector containing the complementary sequence to a target gene. The secondary probe has a sequence complementary to the vector portion of the primary probe and is labeled with biotin via the transamination reaction. An advantage of this method is that the single-stranded primary probe can be prepared with ease by using the chimeric phage-plasmid vector system, thereby avoiding tedious labeling of individually different probes. As the primary probe is not modified with biotin and other labels, it conserves the sequence to be hybridized with a target. Accordingly, the primary probe containing a relatively short hybridizing region (ca. 50 bp) can efficiently hybridize with the target. In fact, the universal probe is sensitive enough to detect a single-copy human gene on Southern blots. 相似文献
30.
Structural organization of the bovine adrenodoxin gene 总被引:1,自引:0,他引:1
Y Sagara H Sawae A Kimura Y Sagara-Nakano K Morohashi K Miyoshi T Horiuchi 《Journal of biochemistry》1990,107(1):77-83