全文获取类型
收费全文 | 12494篇 |
免费 | 785篇 |
国内免费 | 1篇 |
专业分类
13280篇 |
出版年
2022年 | 59篇 |
2021年 | 116篇 |
2020年 | 62篇 |
2019年 | 94篇 |
2018年 | 166篇 |
2017年 | 110篇 |
2016年 | 206篇 |
2015年 | 297篇 |
2014年 | 378篇 |
2013年 | 744篇 |
2012年 | 592篇 |
2011年 | 639篇 |
2010年 | 360篇 |
2009年 | 405篇 |
2008年 | 656篇 |
2007年 | 593篇 |
2006年 | 595篇 |
2005年 | 596篇 |
2004年 | 616篇 |
2003年 | 576篇 |
2002年 | 600篇 |
2001年 | 384篇 |
2000年 | 395篇 |
1999年 | 322篇 |
1998年 | 184篇 |
1997年 | 148篇 |
1996年 | 144篇 |
1995年 | 140篇 |
1994年 | 120篇 |
1993年 | 106篇 |
1992年 | 242篇 |
1991年 | 250篇 |
1990年 | 222篇 |
1989年 | 220篇 |
1988年 | 177篇 |
1987年 | 161篇 |
1986年 | 143篇 |
1985年 | 147篇 |
1984年 | 125篇 |
1983年 | 123篇 |
1982年 | 114篇 |
1981年 | 90篇 |
1980年 | 68篇 |
1979年 | 86篇 |
1978年 | 95篇 |
1977年 | 64篇 |
1976年 | 81篇 |
1975年 | 60篇 |
1974年 | 47篇 |
1973年 | 65篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
81.
82.
A new rapid and simple method has been developed for the separation of disaccharides obtained by chondroitinase digestion of chondroitin sulfates and dermatan sulfate using electrophoresis on cellulose acetate plates (Titan III cellulose acetate plates). Three disaccharides are completely separated by electrophoresis in barium acetate or calcium acetate in a short time, and less than 50 μg of glycosaminoglycan samples can be analyzed within 2 h. 相似文献
83.
Takao Shimizu Kigen Kondo Osamu Hayaishi 《Archives of biochemistry and biophysics》1981,206(2):271-276
In the presence of heme and reduced glutathione, prostaglandin (PG) endoperoxides underwent rapid conversion to malondialdehyde and 12l-hydroxy-5,8,10-heptadecatrienoic acid. In addition, PG endoperoxides as well as lipid peroxides produced malondialdehyde to yield a red pigment during the thiobarbituric acid reaction with different efficiencies. The relative rates of the reaction were: 1,1,3,3-tetraethoxypropane, 100; PGG2, 55; PGH2, 32; and 15-hydroperoxyarachidonic acid, 6. The thiobarbituric acid reactive materials in rabbit serum decreased by 25–60%, after intravenous administration of aspirin (a cyclo-oxygenase inhibitor) and with a concomitant decline of serum PG levels. These results, taken together, suggested that serum thiobarbituric acid values, considered to be an indicator of lipid peroxide levels, were to a significant extent due to PG endoperoxides and their derivatives. 相似文献
84.
Solid phase fluoroimmunoassay of serum 11-deoxycortisol (17,21-dihydroxy-4-pregnene-3,20-dione) was established using fluorescein isothiocyanate-labelled 11-deoxycortisol and anti-11-deoxycortisol antibody-conjugated polyacrylamide beads. 21-Amino-17-hydroxyprogesterone (21-amino-17-hydroxy-4-pregnene-3,20-dione) was synthesized as a useful derivative for preparing the fluorescent dye conjugate. Serum 11-deoxycortisol was measured with this assay system after extraction and purification by Sephadex LH-20 column chromatography. The minimal amount of 11-deoxycortisol detected was 40 pg/tube and the measurable range was from 0.04 to 5.0 microgram/dl. Intra- and inter-assay coefficients of variation were 8.3% (n=6) and 9.8% (n=5), respectively. 11-deoxycortisol values determined by the present assay correlated well with those determined by radioimmunoassay. The present assay is particularly suitable for estimating the conditions of the pituitary and adrenocortical functions. 相似文献
85.
Nucleotide sequences of two aspartic acid tRNAs from rat liver and rat ascites hepatoma 总被引:7,自引:0,他引:7
Y Kuchino N Shindo-Okada N Ando S Watanabe S Nishimura 《The Journal of biological chemistry》1981,256(17):9059-9062
86.
T Watanabe 《Tissue & cell》1981,13(1):1-7
The cell surface of Paramecium caudatum, syngen 3, was examined by electron microscopy using ruthenium red (RR) staining. The RR-positive surface coat is of uniform thickness and is found on the entire surface of paramecia, including the gullet area. The surface coat is also observed on the membranes in the tightly united region of conjugating cells. Measurements of the thickness of the surface coat in six stocks of P. caudatum demonstrate a significant difference between complementary mating types: cells of mating type VI have a thicker layer than those of mating type V. No detectable differences in morphology of the surface coat are observed between mating reactive and unreactive cells. Observation in detached cilia indicated that changes in the morphology of the surface coat provoked by the detachment procedure have no effect on mating reactivity. RR stainable substances are detected on both sides of ciliary membranes. 相似文献
87.
Shinkichi Kamata Akira Okada Takehiko Watanabe Yasunaru Kawashima Hiroshi Wada 《Journal of neurochemistry》1980,35(5):1190-1199
The etiologic relationship between disturbances in metabolism of amino acids and amines and hepatic coma was investigated by examining the effects of diets containing various mixtures of amino acids on brain amine metabolism in rats with a portacaval shunt, using a method for simultaneous analysis of amino acids and amines. Rats with a portacaval shunt were fed on four different amino acid compositions with increased amounts of various amino acids suspected to be etiologically related to hepatic coma, such as methionine, phenylalanine, tyrosine, and tryptophan. The animals were killed 4 weeks after operation. During the experimental period, these animals did not become comatose, but exhibited various behavioral abnormalities. Marked increase in the plasma and brain levels of the augmented amino acids, especially methionine and tyrosine, were observed in rats with a portacaval shunt. Brain noradrenaline, dopamine, and serotonin levels were significantly decreased when the brain tyrosine level was increased. These results indicate that in rats with a portacaval shunt the dietary levels of amino acids greatly influence the brain levels of both amino acids and transmitter amines. 相似文献
88.
Osamu Koiwai Shigeo Masaki Shonen Yoshida 《Biochemical and biophysical research communications》1981,103(3):990-996
A factor that stimulates purified DNA polymerase β about 2-fold was separated from DNA polymerase β activity on a DNA-cellulose column. During the early stage of purification, the factor may be associated with DNA polymerase β to form a complex that sediments at 3.9 S in sucrose gradients and behaved as a 52,000 dalton protein on a Sephadex G-100 column. The complex, which contains 40,000 and 12,500 dalton polypeptides, was insensible to the stimulator, and did not show any exonuclease activity. 相似文献
89.
90.