全文获取类型
收费全文 | 196288篇 |
免费 | 11350篇 |
国内免费 | 3549篇 |
出版年
2022年 | 1637篇 |
2021年 | 3002篇 |
2020年 | 2046篇 |
2019年 | 2569篇 |
2018年 | 9138篇 |
2017年 | 8546篇 |
2016年 | 7534篇 |
2015年 | 4416篇 |
2014年 | 5204篇 |
2013年 | 6326篇 |
2012年 | 9245篇 |
2011年 | 13720篇 |
2010年 | 10490篇 |
2009年 | 9793篇 |
2008年 | 11060篇 |
2007年 | 12371篇 |
2006年 | 4883篇 |
2005年 | 5241篇 |
2004年 | 4796篇 |
2003年 | 4859篇 |
2002年 | 4372篇 |
2001年 | 5446篇 |
2000年 | 5153篇 |
1999年 | 3829篇 |
1998年 | 1423篇 |
1997年 | 1365篇 |
1996年 | 1238篇 |
1995年 | 1148篇 |
1994年 | 1115篇 |
1993年 | 1075篇 |
1992年 | 2741篇 |
1991年 | 2732篇 |
1990年 | 2666篇 |
1989年 | 2407篇 |
1988年 | 2192篇 |
1987年 | 2158篇 |
1986年 | 1963篇 |
1985年 | 1942篇 |
1984年 | 1606篇 |
1983年 | 1400篇 |
1982年 | 1016篇 |
1979年 | 1492篇 |
1978年 | 1191篇 |
1977年 | 1062篇 |
1976年 | 1023篇 |
1975年 | 1209篇 |
1974年 | 1297篇 |
1973年 | 1398篇 |
1972年 | 1825篇 |
1971年 | 1591篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
41.
42.
43.
We studied the impulse activity of neurons of the basal and lateral amygdalar nuclei generated when experimental animals (rats) performed fast stereotyped food-procuring movements by the forelimb. Within the basolateral amygdala, there are neurons whose activity is related to different stages of getting off the food, and according to the characteristics of their spiking these neurons should be divided into a number of subpopulations. Activation forestalling the movement initiation by 0.5-1.0 sec was observed in most neurons of the basolateral amygdala; this is considered a manifestation of excitation related to a motivation component of the food-procuring behavior. Activation of amygdalar neurons following movement initiation can result from generation in this structure of additional excitation necessary for successful performance of a complete food-procuring motor cycle. 相似文献
44.
45.
46.
A Yersinia pseudotuberculosis protein which cross-reacts with HLA-B27 总被引:10,自引:0,他引:10
J H Chen D H Kono Z Yong M S Park M M Oldstone D T Yu 《Journal of immunology (Baltimore, Md. : 1950)》1987,139(9):3003-3011
The most-debated question in the investigation of the spondyloarthropathies has been whether there is molecular mimicry between host HLA-B27 antigens and the arthritis-causing pathogens. We have generated a monoclonal anti-HLA-B27 antibody in our laboratory and have used a radioimmunoassay to screen a panel of bacterial species. Two strains of Yersinia pseudotuberculosis were found to be highly reactive. The cross-reactive Yersinia component was identified by Western blot to be a 19,000 component. A preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis chromatography apparatus was constructed to isolate milligram quantities of this component. To verify that the component carried the HLA-B27-specific epitope, rabbits were hyperimmunized with the purified materials. Affinity-purified antibodies from one of the immunized rabbits indeed carried anti-HLA-B27 activity. Last, antibodies generated against synthetic peptides derived from the HLA-B27.1 amino acid sequence were tested against the Yersinia component. Positive reactivity was found with antibodies generated against a peptide spanning residues 69-83 of the HLA-B27.1 protein. Since this resides in the segment responsible for the allotypic specificity of the antigen, these experiments establish the presence of molecular mimicry to a high degree of confidence. 相似文献
47.
Coordinate regulation of ribosomal protein mRNA level in regenerating rat liver. Study with the corresponding mouse cloned cDNAs. 总被引:17,自引:6,他引:11
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)
Cloned mouse ribosomal protein (rp) cDNAs exhibit extensive homology with the corresponding rat sequences. The size of the rp-mRNAs and complexity of the rp-genes are very similar in the two species. Using the mouse rp-recombinant DNAs we find that the relative abundance of rat L7, L13, L18, L30, L32/33 and S16 mRNAs increases after partial hepatectomy. Their maximal level is about twice that of normal rat liver, and is achieved 12-18 h after the operation, while the relative abundance of albumin mRNA decreases to half the normal values 12 h after partial hepatectomy. This concomitant increase in the relative content of these rp-mRNAs indicates coordinate regulation of their level in the rat. The dissimilar behavior of L10 and L19 rp-mRNA suggests additional control mechanisms of rp-mRNA levels in the regenerating rat liver. 相似文献
48.
The amino acid composition, N- and C-terminal amino acid sequences, and the basic physicochemical and immunochemical properties of the recently discovered pregnancy-associated molecular variant of human transcortin (Strel'chyonok, O.A., Avvakumov, G.V. and Akhrem, A.A. (1984) Carbohydr. Res. 134, 133-140) have been found to be identical to those of transcortin from normal donor serum. This suggests the identity of polypeptide moieties of the two glycoproteins. The transcortin variant has a lower isoelectric point (3.5-4.1) than normal transcortin (3.6-4.2), and different electrophoretic mobility in low-porosity polyacrylamide gel (one band versus two for normal transcortin). These differences can be reasonably explained by different organization of the carbohydrate moieties of these glycoproteins due to diverse post-translational modification of a single polypeptide chain. The levels of transcortin variant in the maternal venous serum throughout normal gestation (447 donors in all) and on the fifth day after delivery, as well as in umbilical cord serum and extracts of term placenta, have been measured by a radioimmune assay. Analysis of the data obtained allowed us to conclude that the biosynthesis of pregnancy-associated transcortin variant occurs in some organ of the maternal organism rather than in the feto-placental system, and it is a characteristic of pregnancy as a unique physiological state of the female organism rather than a phenomenon caused by individual features of certain women. We assume that the transcortin variant takes part in the guided transport of corticosteroids and/or progestins into some tissues that develop in the course of gestation. 相似文献
49.
M. Tanushev E. M. Myasnikova Dr. Sci A. Yu. Yakovlev 《Biometrical journal. Biometrische Zeitschrift》1987,29(1):93-102
The aim of this study was mathematical formalization of the development of two damage processes in response to the combined action of two different damaging agents. The model allows to obtain the parametric family of distributions for the life-span when the organism's death is due to joint effect of two damage processes. Differing by their probabilistic meaning the notions of a priori (M (t)) and a posteriori (M(y)) conditional mean contributions of each damage process to the final effect of combined injury are introduced. The formulas permitting to compute the M and M values on the basis of survival data parametric analysis are given. 相似文献
50.