全文获取类型
收费全文 | 5623篇 |
免费 | 746篇 |
国内免费 | 1篇 |
出版年
2022年 | 45篇 |
2021年 | 75篇 |
2020年 | 48篇 |
2019年 | 66篇 |
2018年 | 79篇 |
2017年 | 97篇 |
2016年 | 100篇 |
2015年 | 157篇 |
2014年 | 176篇 |
2013年 | 228篇 |
2012年 | 268篇 |
2011年 | 289篇 |
2010年 | 177篇 |
2009年 | 166篇 |
2008年 | 205篇 |
2007年 | 211篇 |
2006年 | 191篇 |
2005年 | 191篇 |
2004年 | 173篇 |
2003年 | 166篇 |
2002年 | 166篇 |
2001年 | 186篇 |
2000年 | 157篇 |
1999年 | 145篇 |
1998年 | 84篇 |
1997年 | 67篇 |
1996年 | 49篇 |
1995年 | 54篇 |
1994年 | 68篇 |
1993年 | 66篇 |
1992年 | 108篇 |
1991年 | 97篇 |
1990年 | 111篇 |
1989年 | 110篇 |
1988年 | 98篇 |
1987年 | 105篇 |
1986年 | 87篇 |
1985年 | 116篇 |
1984年 | 99篇 |
1983年 | 101篇 |
1982年 | 68篇 |
1981年 | 59篇 |
1980年 | 63篇 |
1979年 | 82篇 |
1978年 | 54篇 |
1977年 | 66篇 |
1976年 | 64篇 |
1975年 | 48篇 |
1974年 | 52篇 |
1973年 | 61篇 |
排序方式: 共有6370条查询结果,搜索用时 31 毫秒
111.
Heterodera zeae, the corn cyst nematode, is redescribed and illustrated with comparative details and measurements of females, cysts, and larvae from Maryland, USA; and India. Scanning electron micrographs o f specimens from the United States are also presented. Revised measurements for the larval stylet and new diadnostic characters, especially in the cyst cone, for H. zeae are given. The relationship of H. zeae to close species is discussed. 相似文献
112.
Ethidium fluorescence assays were adapted for the rapid and sensitive detection of precA; in addition, fluorescence measurements on binding precA to linear, OC and CCC PM2 DNAs have enabled the stoichiometry of precA binding as well as the precA-induced unwinding angle of DNA to be determined. The stoichiometry of binding was independently confirmed by sedimentation analysis to be one precA molecule per 3 bp. The unwinding angle was also independently confirmed by measurements of fluorescence changes induced by the binding of precA to CCC DNA which was relaxed by topoisomerase to give a precA-induced unwinding angle of 51 degrees. Electron microscopy of OC DNA molecules which bound nonsaturating amounts of precA revealed that the length increase in DNA due to precA was approximately 55%. Finally, examination of negatively stained precA complexes with a variety of linear DNAs showed that the minor groove is the primary site of interaction for this protein. 相似文献
113.
Chemical Nature of Malty Flavor and Aroma Produced by Streptococcus lactis var. maltigenes
下载免费PDF全文
![点击此处可从《Applied microbiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Mature skim milk cultures of Streptococcus lactis var. maltigenes were steam distilled at low temperature under reduced pressure. Ethyl ether extracts were prepared from the distillates and analyzed by gas-liquid chromatography and mass spectrometry. Twenty of 31 components detected in the culture distillates were identified positively and 11 tentatively, whereas 10 of 19 components detected in the heated skim milk control were identified positively and 9 tentatively. Among components detected in the culture distillate, but not detected in the heated skim milk distillate, and which have not been previously identified in milk cultures of the organism were phenylacetaldehyde and phenethanol. Quantitative analyses of the volatiles entrained from milk cultures of several strains of S. lactis var. maltigenes revealed a probable relationship between variation in the character of the aroma of the cultures and the alcohol/aldehyde ratio. 相似文献
114.
115.
Isolation of brain tubulin by affinity chromatography 总被引:2,自引:0,他引:2
N D Hinman J L Morgan N W Seeds J R Cann 《Biochemical and biophysical research communications》1973,52(3):752-758
An affinity chromatographic procedure for the isolation of tubulin from brain is described. The yield is good and the method rapid and gentle. Criteria of purity are colchicine binding, SDS acrylamide gel electrophoresis, and velocity sedimentation. 相似文献
116.
117.
118.
Structure and Development of Viruses as Observed in the Electron Microscope: X. Entry and Uncoating of Adenovirus 总被引:1,自引:1,他引:0
下载免费PDF全文
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Stages in the direct penetration of adenovirus through the cell membrane are illustrated. Phagocytosis with rupture of the vacuole and release of virus into the cytoplasm may also account for entry of some particles. Uncoating by digestion within phagosomes was not observed. Rather, alteration of capsid and core occurred to virions free in the cytoplasm. Nucleoprotein released from virus close to the nucleus was transported to the nuclear matrix by a unique mechanism. These events were not prevented by puromycin and hence were not dependent upon the synthesis of new enzymes. They were, however, energy-dependent. 相似文献
119.
Stimulation of ethylene evolution and abscission in cotton by 2-chloroethanephosphonic Acid 总被引:14,自引:13,他引:1
下载免费PDF全文
![点击此处可从《Plant physiology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Morgan PW 《Plant physiology》1969,44(3):337-341
Ethrel, a mixture of 2-chloroethanephosphonic acid and its ethyl ester, hastens abscission of leaves, debladed petioles, and flower buds of cotton plants (Gossypium hirsutum, L.). Both young and old leaves abscissed while still green. Application of Ethrel stimulated evolution of ethylene, and this response preceded abscission. Air concentrations of ethylene around enclosed, treated-plants were adequate to produce abscission in plants. Non-treated plants defoliated when enclosed with plants sprayed with Ethrel. The stimulation of abscission of explant petioles by Ethrel was reversed by naphthalene acetic acid. The stimulation of abscission by Ethrel was concluded to be mediated by ethylene. 相似文献
120.
Ten adults suffering from salicylate overdosage were treated successfully with a combination of sodium bicarbonate and acetazolamide to exploit the increase in salicylate clearance which is known to occur in very alkaline urine. The advantages of the method include the absence of important complications and the small volume of fluid required. 相似文献