全文获取类型
收费全文 | 176795篇 |
免费 | 7936篇 |
国内免费 | 848篇 |
出版年
2022年 | 637篇 |
2021年 | 1560篇 |
2020年 | 884篇 |
2019年 | 1113篇 |
2018年 | 12996篇 |
2017年 | 11671篇 |
2016年 | 9389篇 |
2015年 | 4208篇 |
2014年 | 4336篇 |
2013年 | 5111篇 |
2012年 | 10679篇 |
2011年 | 18939篇 |
2010年 | 15811篇 |
2009年 | 11807篇 |
2008年 | 14889篇 |
2007年 | 16419篇 |
2006年 | 5491篇 |
2005年 | 5532篇 |
2004年 | 5848篇 |
2003年 | 5672篇 |
2002年 | 5170篇 |
2001年 | 1136篇 |
2000年 | 818篇 |
1999年 | 1000篇 |
1998年 | 1252篇 |
1997年 | 858篇 |
1996年 | 764篇 |
1995年 | 660篇 |
1994年 | 633篇 |
1993年 | 700篇 |
1992年 | 589篇 |
1991年 | 567篇 |
1990年 | 479篇 |
1989年 | 416篇 |
1988年 | 452篇 |
1987年 | 369篇 |
1986年 | 329篇 |
1985年 | 413篇 |
1984年 | 534篇 |
1983年 | 424篇 |
1982年 | 508篇 |
1981年 | 498篇 |
1980年 | 425篇 |
1979年 | 298篇 |
1978年 | 337篇 |
1977年 | 287篇 |
1976年 | 273篇 |
1974年 | 243篇 |
1972年 | 364篇 |
1971年 | 380篇 |
排序方式: 共有10000条查询结果,搜索用时 937 毫秒
881.
Fusarium moniliforme grown in a chemically defined medium in submerged culture accumulated amino acids extracellularly. Alanine and glutamic acid were present in greatest amounts, with traces of glycine, lysine, threonine, and valine detectable. Increasing the glucose and urea concentrations of the medium increased yields of alanine. Further increases in alanine production occurred with elevated levels of mineral salts in the medium, whereas the addition of a vitamin mixture proved to be inhibitory. Chemical changes resulting from the growth of F. moniliforme in the final fermentation medium disclosed maximal alanine production, mycelial weight, and glucose consumption after 72 hr of incubation at 28.5 C. Total soluble nitrogen, by contrast, was minimal at the same time period. The pH remained in the alkaline range throughout the fermentation. 相似文献
882.
883.
884.
885.
886.
887.
Book reviewed in this article:
LINGUISTICS: Pis'mennost'
LINGUISTICS: Pis'mennost'
888.
The lethal effects of high-intensity airborne sonic (9.9 kc/sec) and ultrasonic waves (30.4 kc/sec) on spores of Bacillus subtilis var. niger ATCC 9372 were determined. The spores, which were deposited on filter-paper strips, were exposed to sound waves for periods varying from 1 to 8 hr, at a temperature of 40 C and a relative humidity of 40%. Significant reductions in the viable counts of spores exposed to airborne sonic or ultrasonic irradiations were obtained. The antibacterial activity of airborne sound waves varied with the sound intensity level, the period of irradiation, and the distance of the sample from the sound source. At similar intensity levels, the amplitude of motion of the sound waves appeared to be a factor in acoustic sterilization. 相似文献
889.
890.
Michael F. Myers 《CMAJ》1965,92(17):926-927
Sweat chlorides of 10 sets of parents of children with cystic fibrosis and 11 controls were studied in an attempt to develop a test for the diagnosis of cystic fibrosis heterozygotes by subjecting both the parents and controls to a low sodium diet and comparing sweat chloride values as the diet progressed. It was hoped that the sweat chloride levels of the parents, the heterozygotes, would remain stationary throughout the diet, since their children, the homozygotes, reveal this finding under similar conditions of salt deprivation. The sweat chloride levels of the controls, because of effects of aldosterone, were expected to decrease steadily from the commencement of the diet to its termination.A decrease in sweat chloride values of similar magnitude was found in both parents and controls as the diet continued. It is concluded that the study of sweat electrolyte levels in salt-deprived subjects is of no value in the diagnosis of cystic fibrosis heterozygotes. 相似文献