全文获取类型
收费全文 | 7467篇 |
免费 | 481篇 |
国内免费 | 7篇 |
出版年
2022年 | 39篇 |
2021年 | 71篇 |
2019年 | 71篇 |
2018年 | 81篇 |
2017年 | 77篇 |
2016年 | 119篇 |
2015年 | 169篇 |
2014年 | 201篇 |
2013年 | 427篇 |
2012年 | 389篇 |
2011年 | 301篇 |
2010年 | 196篇 |
2009年 | 186篇 |
2008年 | 359篇 |
2007年 | 368篇 |
2006年 | 360篇 |
2005年 | 346篇 |
2004年 | 377篇 |
2003年 | 356篇 |
2002年 | 367篇 |
2001年 | 254篇 |
2000年 | 238篇 |
1999年 | 196篇 |
1998年 | 101篇 |
1997年 | 83篇 |
1996年 | 67篇 |
1995年 | 58篇 |
1994年 | 64篇 |
1993年 | 65篇 |
1992年 | 158篇 |
1991年 | 126篇 |
1990年 | 150篇 |
1989年 | 143篇 |
1988年 | 121篇 |
1987年 | 114篇 |
1986年 | 105篇 |
1985年 | 90篇 |
1984年 | 90篇 |
1983年 | 73篇 |
1982年 | 56篇 |
1981年 | 61篇 |
1980年 | 46篇 |
1979年 | 80篇 |
1978年 | 59篇 |
1977年 | 53篇 |
1976年 | 40篇 |
1975年 | 46篇 |
1974年 | 44篇 |
1973年 | 41篇 |
1972年 | 47篇 |
排序方式: 共有7955条查询结果,搜索用时 15 毫秒
101.
Hideya Hayashi Seiji Ito Teruo Tanaka Manabu Negishi Hideo Kawabe Yokohama Hiromitsu Kikuko Watanabe Osamu Hayaishi 《Prostaglandins & other lipid mediators》1987,33(4)
In view of the recent finding that prostaglandin D2 is stereospecifically converted to 9α,11β-prostaglandin F2, an isomer of prostaglandin F2α, a highly specific and sensitive radioimmunoassay for 9α,11β-prostaglandin F2 was developed and applied to determine the content of this prostaglandin in various rat tissues. Antisera against 9α-11β-prostaglandin F2 were raised in rabbits immunized with the bovine serum albumin conjugate, and [3H]9α,11β-prostaglandin F2 was enzymatically prepared from [3H]prostaglandin D2. The assay detected 9α,11β-prostaglandin F2 over the range of 20 pg to 1 ng, and the antiserum showed less than 0.04% cross-section with prostaglandin F2α, prostaglandin F2β and 9β,11β-prostaglandin F2. To avoid postmortem changes, tissues were frozen in liquid nitrogen immediately after removal. The basal level of 9α,11β-prostaglandin F2 was hardly detectable in various tissues of the rat examined, including spleen, lung, liver and brain; although it was found to be 0.31 ± 0.06 ng/g wet weight in the small intestine. During convulsion induced by pentylenetetrazole, enormous amounts of prostaglandin D2 (ca. 180 ng/g wet weight) and prostaglandin F2α (ca. 70 ng/g) were produced in the brain; however, 9α,11β-prostaglandin F2 was detected neither there nor in the blood. This result demonstrates that the conversion to 9α,11β-prostaglandin F2 is a minor pathway, if one at all, of prostaglandin D2 metabolism in the rat brain. 相似文献
102.
Oncogene amplification in tumor cells 总被引:1,自引:0,他引:1
N Kanda Y Kaneko Y Hayashi T Utakoji 《Tanpakushitsu kakusan koso. Protein, nucleic acid, enzyme》1986,31(13):1277-1285
103.
A variant in the restriction endonuclease cleavage pattern of mitochondrial DNA in the domestic fowl, Gallus gallus domesticus 总被引:6,自引:0,他引:6
The cleavage patterns of mitochondrial DNAs (mtDNAs) were investigated from 15 lines of domestic fowls, Gallus gallus domesticus, using 11 restriction endonucleases. The cleavage patterns with 10 restriction endonucleases were identical in all the lines. A variant was found in a line of White Leghorn in the pattern with MspI digestions. Cleavage patterns of the red jungle fowl, Gallus gallus gallus, were identical to the common patterns shown by the 14 lines of domestic fowls. 相似文献
104.
Development of human pancreas 总被引:2,自引:0,他引:2
Masashi Fukayama Michio Ogawa Yukiko Hayashi Morio Koike 《Differentiation; research in biological diversity》1986,31(2):127-133
The developmental sequence of human pancreatic secretory proteins has not previously been studied in detail. We applied immunohistochemistry to study 20 fetal and neonatal pancreas' (8th to 39th gestational weeks) using antisera against the following pancreatic secretory proteins: pancreatic secretory trypsin inhibitor (PSTI), serine proteinases (trypsin, chymotrypsin, and elastase I), and amylase. PSTI was first detected in developing buds of the pancreas during the 8th gestational week, and proteinases were observed in acinar cells during the 14th week of gestation. Immunoreactivity for both PSTI and proteinases was found in most acinar cells soon after their appearance. Immunoreactivity for amylase could not be detected in fetal or neonatal pancreas tissue. PSTI was also found in developing islets during the 14th gestational week, but the number of immunoreactive cells had decreased by term. Cells positive for serine proteinases were occasionally in contact with islets in second-trimester fetuses. In discussing these results, we give particular attention to the nonparallel appearance of secretory products in the fetal pancreas, and the significance of cells immunoreactive for secretory proteins in endocrine islets. 相似文献
105.
Amylase in human lungs and the female genital tract. Histochemical and immunohistochemical localization 总被引:2,自引:0,他引:2
We investigated the localization of amylase in normal human lungs and the female genital tract using immunohistochemical and histochemical methods. Immunohistochemical procedures were applied to formaldehyde-fixed, paraffin-embedded specimens as well as to cryostat sections of periodate/lysine/paraformaldehyde (PLP)-fixed tissues. The starch-substrate-film method was used for the histochemical investigation of unfixed frozen sections. Amylase immunoreactivity was observed in ciliated epithelial cells of the bronchus and in serous cells of the bronchial glands but not in the alveolar epithelium. Immunoreactive amylase was also found in the cytoplasm of the ciliated epithelium of the fallopian tubes, especially in the apical part of the cytoplasm and in ciliary vesicles. Immunoreactive amylase was also found to be present in the surface epithelial cells and glands of the uterine cervix, as well as in the superficial part of the endometrial glands. The distribution of amylase activity revealed using histochemistry was similar to that observed in cryostat sections of PLP-fixed tissues after immunohistochemical staining. Amylase antigenicity was better preserved in cryostat sections of PLP-fixed materials than in formaldehyde-fixed, paraffin-embedded specimens. The results are discussed in relation to pulmonary and female-genital-tract diseases. 相似文献
106.
The structure of nucleosome core particles as revealed by difference Raman spectroscopy. 总被引:1,自引:0,他引:1
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)
Raman spectra have been observed of nucleosome core particles (I) prepared from chicken erythrocyte chromatin, its isolated 146 bp DNA (II), and its isolated histone octamer (H2A+H2B+H3+H4)2 (III). By examining the difference Raman spectra, (I)-(II), (I)-(III), and (I)-(II)-(III), several pieces of information have been obtained on the conformation of the DNA moiety, the conformation of the histone moiety, and the DNA-histone interaction in the nucleosome core particles. In the nucleosome core particles, about 15 bp (A.T rich) portions of the whole 146 bp DNA are considered to take an A-form conformation. These are considered to correspond to its bent portions which appear at intervals of 10 bp. 相似文献
107.
Summary A population-based screening of newborns for the structural variants of fetal hemoglobin was carried out in Osaka Prefecture, Japan, by isoelectric focusing of globin chains using dried blood on filter paper. Of 80,000 newborns, 18 had globin variants and 55 had globin variants. The incidence of globin variants (1/1,455) was much higher than that of globin variants (1/4,444). Structural studies were then carried out on the abnormal globins in 36 samples, and revealed that 25 of them were Hb F Yamaguchi (AT 80 AspAsn). The prevalence of this variant in Japanese was estimated to be as high as one per 2,100. 相似文献
108.
109.
Biosynthesis of Bacillus licheniformis penicillinase in Escherichia coli and in Bacillus subtilis. 总被引:5,自引:5,他引:0
Modified prepenicillinase was accumulated in both Escherichia coli and Bacillus subtilis treated with globomycin. Although the inhibitions of processings of prepenicillinase and prolipoprotein by globomycin in E. coli are qualitatively similar, they differ in the degree of inhibition at given concentrations of globomycin. The processing of prepenicillinase proceeds much more rapidly in E. coli than in B. subtilis. 相似文献
110.
S Maezawa Y Hayashi T Nakae J Ishii K Kameyama T Takagi 《Biochimica et biophysica acta》1983,747(3):291-297
An assessment study was carried out to evaluate the performance of the low-angle laser light scattering technique combined with high-performance gel chromatography in the presence of a nonionic surfactant, octaethyleneglycol n-dodecyl ether, precision differential refractometry and ultraviolet photometry. It was found that the combined technique is highly promising as a method for the determination of the molecular weight of a membrane protein solubilized by the surfactant. For trial, molecular weights of the following membrane proteins of Escherichia coli, both solubilized in oligomeric forms, were measured; porin that forms the transmembrane diffusion pore in the outer membrane, and lambda-receptor protein that facilitates the diffusion of maltose-maltodextrins across the outer membrane. The result obtained indicates that both porin and lambda-receptor protein exist as trimers in the surfactant solution. 相似文献