全文获取类型
收费全文 | 1049884篇 |
免费 | 125786篇 |
国内免费 | 598篇 |
专业分类
1176268篇 |
出版年
2016年 | 11789篇 |
2015年 | 17456篇 |
2014年 | 20132篇 |
2013年 | 28522篇 |
2012年 | 32119篇 |
2011年 | 32313篇 |
2010年 | 21981篇 |
2009年 | 20698篇 |
2008年 | 29367篇 |
2007年 | 30138篇 |
2006年 | 28262篇 |
2005年 | 27176篇 |
2004年 | 26768篇 |
2003年 | 26022篇 |
2002年 | 25211篇 |
2001年 | 44741篇 |
2000年 | 45290篇 |
1999年 | 36292篇 |
1998年 | 14078篇 |
1997年 | 14870篇 |
1996年 | 14203篇 |
1995年 | 13445篇 |
1994年 | 13181篇 |
1993年 | 13176篇 |
1992年 | 31002篇 |
1991年 | 30224篇 |
1990年 | 29540篇 |
1989年 | 28871篇 |
1988年 | 26644篇 |
1987年 | 26039篇 |
1986年 | 24235篇 |
1985年 | 24331篇 |
1984年 | 20241篇 |
1983年 | 17702篇 |
1982年 | 14007篇 |
1981年 | 12641篇 |
1980年 | 12089篇 |
1979年 | 19676篇 |
1978年 | 15788篇 |
1977年 | 14387篇 |
1976年 | 13626篇 |
1975年 | 14861篇 |
1974年 | 15821篇 |
1973年 | 15537篇 |
1972年 | 14029篇 |
1971年 | 12959篇 |
1970年 | 11090篇 |
1969年 | 10605篇 |
1968年 | 9492篇 |
1967年 | 8510篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Rare syndromes. The Kaufman-McKusick syndrome. A review of the 44 cases reported in the literature 总被引:1,自引:0,他引:1
A Cantani M L Tacconi N Benincori A Picarazzi D Ceccoli S Gaudino 《Annales de génétique》1987,30(2):70-74
The Kaufman-McKusick syndrome (MK 23670) is a rare autosomal recessive disorder characterized by the triad of hydrometrocolpos, postaxial polydactyly, and congenital heart disease. Multiple other anomalies have been ascribed to this syndrome. Hydrometrocolpos, especially if unrecognized, may be a serious, life-threatening condition in the newborn girl. Forty-four cases have been so far reported in the literature. A great phenotypic variability occurs in this syndrome, therefore making it very difficult to identify the disorder at its presentation and classify it correctly. We shall hereafter review current data regarding the prominent clinical features, the diagnosis and treatment of this syndrome. Problems in genetic counseling will be discussed. 相似文献
993.
The population dynamics of Heterodera glycines as influenced by alachlor, fenamiphos, and ethoprop alone and in herbicide-nematicide combinations were studied in the field. Numbers of H. glycines juveniles and eggs were higher at midseason and harvest where nematicides were applied. Fenamiphos alone or in combination with alachlor provided better control of H. glycines and greater seed yields than treatments with ethoprop. Numbers of H. glycines eggs at harvest in 1980 were positively correlated with numbers of juveniles at planting in 1981 and negatively related to seed yield in 1981. 相似文献
994.
995.
A simple and accurate technique for the determination of the heat resistance of spores is described. The technique combines a modified capillary tube method with a solid heating block. The come-up time of spore suspensions was found to be short and simple and accurate technique is suggested for the correction of the come-up times. Experimental results are presented for the destruction of spores of Bacillus stearothermophilus at 120 which indicates the accuracy and reproducibility of the new method. 相似文献
996.
Naturally occurring strains of Salmonella paratyphi B unable to form adhesive (type-1) fimbriae 总被引:1,自引:0,他引:1
D C Old 《Genetical research》1982,40(3):305-313
997.
998.
J Rivera J M Mullins K Furuichi C Isersky 《Journal of immunology (Baltimore, Md. : 1950)》1986,136(2):623-627
Rat basophilic leukemia (RBL) cells have distinct receptors for IgE and IgG. We assessed the endocytosis of chemically and immunochemically cross-linked mouse-IgG and its influence on the simultaneous endocytosis of IgE. We found that at 37 degrees C, aggregates of IgG and IgE were endocytosed at about the same rate with one-half of the maximal endocytosis occurring in 5 to 13 min, and the efficiency of endocytosis for both ligands ranging from 40 to 70%. We also found that endocytosis of cross-linked IgE and IgG occurred simultaneously and neither ligand significantly affected the rate or extent of endocytosis of the other. The cells accumulated the cross-linked IgG, and then released it to the extracellular environment, at a rate (less than 3%/hr) slower than the released endocytosed IgE (greater than 10%/hr). Using an assay that discriminates between unbound and receptor-bound oligomeric IgG, we found that oligomeric IgG is endocytosed with its receptor, and that the bulk of the ligand remains bound to its receptor for greater than 120 min after endocytosis. The differences in the rate of release of endocytosed IgG vs IgE suggests that the intracellular fate or pathway of these two oligomeric ligands may differ. 相似文献
999.
D. Higuet 《Genetica》1986,69(2):107-110
Under the hypothesis that heterosis may be due to a greater flexibility of heterozygotes, we have measured in a Drosophila melanogaster strain, polymorphic at the sepia locus, female productivity of the homozygotes and heterozygotes for this locus, in constant as well as in fluctuating temperature conditions. It was expected that the heterozygotes, being more flexible, would be better adapted to a fluctuating temperature than to a constant one. At none of the three temperature regimes (18°C; 28°C; 18–28°C) heterosis or rather overdominance was evident. However, fluctuating temperature results reveal a greater performance of all genotypes than constant-temperature ones do. 相似文献
1000.
Robert C. Tait Byron E. Froman Debbie L. Laudencia-Chingcuanco Leslie D. Gottlieb 《Plant molecular biology》1988,11(4):381-388
Nuclear genes that appear to encode both cytosolic and plastid isozymes of phosphoglucose isomerase (PGI), an essential glycolytic enzyme, have been isolated from three diploid species of the annual wild flower genus Clarkia (Onagraceae). The genes do not contain introns and are expressed to varying degrees in Escherichia coli when cloned in either Charon 35 phage or pUC plasmid vectors. The PGI proteins synthesized in E. coli form dimers, are catalytically active, and their electrophoretic mobilities are similar to those of appropriate Clarkia PGIs. The nucleotide sequence of a gene encoding a plastid isozyme of C. unguiculata is described. 相似文献