全文获取类型
收费全文 | 536613篇 |
免费 | 68765篇 |
国内免费 | 1590篇 |
出版年
2021年 | 5070篇 |
2020年 | 5219篇 |
2019年 | 7273篇 |
2018年 | 9128篇 |
2017年 | 8917篇 |
2016年 | 11409篇 |
2015年 | 14921篇 |
2014年 | 16266篇 |
2013年 | 20993篇 |
2012年 | 22556篇 |
2011年 | 22366篇 |
2010年 | 16161篇 |
2009年 | 13627篇 |
2008年 | 18451篇 |
2007年 | 18358篇 |
2006年 | 17421篇 |
2005年 | 16334篇 |
2004年 | 16243篇 |
2003年 | 15068篇 |
2002年 | 14535篇 |
2001年 | 20444篇 |
2000年 | 20314篇 |
1999年 | 16174篇 |
1998年 | 6173篇 |
1997年 | 6032篇 |
1996年 | 5767篇 |
1995年 | 5542篇 |
1994年 | 5185篇 |
1993年 | 5169篇 |
1992年 | 12980篇 |
1991年 | 12873篇 |
1990年 | 12613篇 |
1989年 | 12037篇 |
1988年 | 11161篇 |
1987年 | 10504篇 |
1986年 | 10033篇 |
1985年 | 9820篇 |
1984年 | 8197篇 |
1983年 | 7058篇 |
1982年 | 5353篇 |
1981年 | 4816篇 |
1979年 | 7608篇 |
1978年 | 6136篇 |
1977年 | 5455篇 |
1976年 | 5142篇 |
1975年 | 5944篇 |
1974年 | 6496篇 |
1973年 | 6294篇 |
1972年 | 5618篇 |
1971年 | 5214篇 |
排序方式: 共有10000条查询结果,搜索用时 796 毫秒
991.
The detection of apple chlorotic leafspot virus by a modified procedure of enzyme-linked immunosorbent assay (ELISA) 总被引:1,自引:0,他引:1
The technique of enzyme-linked immunosorbent assay (ELISA) was modified to enable detection of apple chlorotic leafspot virus (CLSV) both in herbaceous hosts and in several naturally infected fruiting and ornamental woody host species. Some of the characteristics of the modified method as used with different virus-host combinations are described. 相似文献
992.
L K Riago A M Nurk A Ia Korneev L Kh Allikmets 《Biulleten' eksperimental'no? biologii i meditsiny》1982,94(11):58-59
(+/-) Fenibut beta-phenyl-GABA) was not able to displace 3H-GABA in Na+ independent GABA binding (IC50 greater than 250 microM). Nevertheless, (+/-) fenibut and (+/-) baclofen effectively displaced 3H-GABA in Ca2+ dependent GABA binding in the presence of 50 microM (+) bicuculline. (+/-) Fenibut was less potent in this respect. It is suggested that fenibut may act via bicuculline-insensitive GABA receptors. 相似文献
993.
The vertebrate head is an extremely complicated structure: development of the head requires tissue-tissue interactions between derivates of all the germ layers and coordinated morphogenetic movements in three dimensions. In this review, we highlight a number of recent embryological studies, using chicken, frog, zebrafish and mouse, which have identified crucial signaling centers in the embryonic face. These studies demonstrate how small variations in growth factor signaling can lead to a diversity of phenotypic outcomes. We also discuss novel genetic studies, in human, mouse and zebrafish, which describe cell biological mechanisms fundamental to the growth and morphogenesis of the craniofacial skeleton. Together, these findings underscore the complex interactions leading to species-specific morphology. These and future studies will improve our understanding of the genetic and environmental influences underlying human craniofacial anomalies. 相似文献
994.
995.
F L P Heyes 《BMJ (Clinical research ed.)》1980,281(6248):1146
996.
997.
André De Troyer 《Journal of applied physiology》2005,98(3):795-803
Changes in intrathoracic pressure produced by the various inspiratory intercostals are essentially additive, but the interaction between these muscles and the diaphragm remains uncertain. In the present study, this interaction was assessed by measuring the changes in airway opening (DeltaPao) or transpulmonary pressure (DeltaPtp) in vagotomized, phrenicotomized dogs during spontaneous inspiration (isolated intercostal contraction), during isolated rectangular or ramp stimulation of the peripheral ends of the transected C(5) phrenic nerve roots (isolated diaphragm contraction), and during spontaneous inspiration with superimposed phrenic nerve stimulation (combined diaphragm-intercostal contraction). With the endotracheal tube occluded at functional residual capacity, DeltaPao during combined diaphragm-intercostal contraction was nearly equal to the sum of the DeltaPao produced by the two muscle groups contracting individually. However, when the endotracheal tube was kept open, DeltaPtp during combined contraction was 123% of the sum of the individual DeltaPtp (P < 0.001). The increase in lung volume during combined contraction was also 109% of the sum of the individual volume increases (P < 0.02). Abdominal pressure during combined contraction was invariably lower than during isolated diaphragm contraction. It is concluded, therefore, that the canine diaphragm and intercostal muscles act synergistically during lung expansion and that this synergism is primarily due to the fact that the intercostal muscles reduce shortening of the diaphragm. When the lung is maintained at functional residual capacity, however, the synergism is obscured because the greater stiffness of the rib cage during diaphragm contraction enhances the DeltaPao produced by the isolated diaphragm and reduces the DeltaPao produced by the intercostal muscles. 相似文献
998.
Calorimetric properties of mixtures of ganglioside GM1 and dipalmitoylphosphatidylcholine 总被引:2,自引:0,他引:2
L O Sillerud D E Schafer R K Yu W H Konigsberg 《The Journal of biological chemistry》1979,254(21):10876-10880
999.
1000.
David Gutirrez‐Larruscain Santiago Andrs‐Snchez Enrique Rico María Montserrat Martínez‐Ortega 《植物分类学报:英文版》2019,57(1):42-54
Forty-five populations of Pentanema corresponding to seven species included in the Pentanema conyzae clade have been studied using AFLP fingerprinting. The results show that allopolyploidization could have been involved in the diversification of this group, specifically in species P. langeanum and P. maletii. Molecular data confirm the presence of P. britannicum in the Iberian Peninsula and key steps are provided to identify the species that are morphologically the most challenging. 相似文献