全文获取类型
收费全文 | 1103792篇 |
免费 | 110967篇 |
国内免费 | 485篇 |
出版年
2018年 | 13486篇 |
2017年 | 12866篇 |
2016年 | 15750篇 |
2015年 | 17497篇 |
2014年 | 20624篇 |
2013年 | 30210篇 |
2012年 | 34691篇 |
2011年 | 38555篇 |
2010年 | 26901篇 |
2009年 | 25102篇 |
2008年 | 34153篇 |
2007年 | 36545篇 |
2006年 | 30172篇 |
2005年 | 29362篇 |
2004年 | 29200篇 |
2003年 | 28384篇 |
2002年 | 27672篇 |
2001年 | 44439篇 |
2000年 | 44133篇 |
1999年 | 35536篇 |
1998年 | 13453篇 |
1997年 | 13644篇 |
1996年 | 12977篇 |
1995年 | 12078篇 |
1994年 | 11705篇 |
1993年 | 11787篇 |
1992年 | 29734篇 |
1991年 | 29236篇 |
1990年 | 28607篇 |
1989年 | 28141篇 |
1988年 | 26173篇 |
1987年 | 24941篇 |
1986年 | 23331篇 |
1985年 | 23603篇 |
1984年 | 19536篇 |
1983年 | 16996篇 |
1982年 | 13128篇 |
1981年 | 11800篇 |
1980年 | 11055篇 |
1979年 | 18562篇 |
1978年 | 14628篇 |
1977年 | 13382篇 |
1976年 | 12784篇 |
1975年 | 14131篇 |
1974年 | 15289篇 |
1973年 | 15042篇 |
1972年 | 14236篇 |
1971年 | 12845篇 |
1970年 | 10907篇 |
1969年 | 10754篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Large deformation mechanics of the enucleated eyeball 总被引:1,自引:0,他引:1
L A Taber 《Journal of biomechanical engineering》1984,106(3):229-234
Large deformation of enucleated pig eyeballs under rigid cylindrical indenters was studied analytically and experimentally. The analytic model for the eyeball consists of a fluid-filled spherical membrane composed of an incompressible, elastic material with an exponential strain energy function. The Rayleigh-Ritz technique provided an approximate solution via a potential energy formulation. Comparison with results from tests on eyeballs and a water-filled rubber (Mooney-Rivlin) shell shows good agreement at large deflection, where membrane action dominates. Due to the highly nonlinear stress-strain relations for the sclera, the load remains relatively small until the indenter displacement approaches 40-60 percent of the eyeball radius, and then the load increases rapidly. Depending on the indenter size, either a perforation or a rupture type of failure occurs. 相似文献
993.
994.
The self determinants recognized by human virus-immune T cells can be distinguished from the serologically defined HLA antigens 总被引:10,自引:0,他引:10
W E Biddison F E Ward G M Shearer S Shaw 《Journal of immunology (Baltimore, Md. : 1950)》1980,124(2):548-552
The self specificity of human influenza virus-immune cytotoxic T cells has been analyzed in order to clarify the relationship between the self antigens that they recognize and the serologically defined HLA-A and -B antigens. Virus-immune effectors from HLA-A2-positive donors were tested on panels of virus-infected target cells from donors who were either HLA-mismatched or matched only for HLA-A2. Virus-immune T cells from 11 out of 11 A2-positive donors lysed all A2-matched virus-infected target cells (and no HLA-mismatched targets), except that each of these effector cells consistently failed to lyse virus-infected target cells from one A2-positive donor (designated M7). Although the A2 specificity of donor M7 could also be distinguished from the A2 antigen of other donors by alloimmune cytotoxic T cells, no differences in the A2 antigen of donor M7 could be defined by extensive serologic analyses. These results indicate that there is a strong but incomplete association between a self antigen recognized by virus-immune T cells and the serologically defined HLA-A2 specificity. 相似文献
995.
996.
C Toga-Piquet A S Henderson J M Grillo A M Vagner-Capodano A Stahl 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1984,298(14):383-386
The Pig chromosomes that contain rDNA sites displayed a polymorphism in the distribution of the genes among the nucleolar organizers located on pairs Nos. 8 and 10. Two, or more often three, active sites were observed in the chromosomes of lymphocytes stimulated with phytohemagglutinin. Only 5% of the metaphases showed a 4th small active site. At the onset of stimulation most cells contained one-two nucleoli; four nucleoli were never observed. After prolonged stimulation, the number of nuclei containing three nucleoli increased. A 4th small nucleolus appeared in a few cells, presumably formed by activation of the smallest rDNA site. 相似文献
997.
998.
M A Chamberlain 《BMJ (Clinical research ed.)》1985,290(6480):1449-1450
999.
Analogs of the molluscan neuropeptide FMRFamide were tested on four different molluscan muscle preparations which show qualitatively different responses to the peptide; the structure-activity relations are basically similar, but not identical. The C-terminal amide and the Arg3 residue are critical for FMRFamide-like activity on all four preparations. In contrast, analogs extended at the N-terminal or with conservative substitutions for the Phe1 or Met2 residue are approximately equipotent to FMRFamide. These structural requirements parallel those for the C-terminal tetrapeptide amide of gastrin. 相似文献
1000.
Isolation and screening of potential actinobacteria for rapid composting of rice straw 总被引:2,自引:0,他引:2
Rice straw is produced as a by-product from rice cultivation, which is composed largely of lignocellulosic materials amenable
to general biodegradation. Lignocellulolytic actinobacteria can be used as a potential agent for rapid composting of bulky
rice straw. Twenty-five actinobacteria isolates were isolated from various in situ and in vitro rice straw compost sources.
Isolates A2, A4, A7, A9 and A24 were selected through enzymatic degradation of starch, cellulose and lignin followed by the
screening for their adaptability on rice straw powder amended media. The best adapted isolate (A7) was identified as Micromonospora
carbonacea. It was able to degrade cellulose, hemicelluloses and carbon significantly (P ≤ 0.05) over the control. C/N ratio was reduced to 18.1 from an initial value of 29.3 in 6 weeks of composting thus having
the potential to be used in large scale composting of rice straw. 相似文献