全文获取类型
收费全文 | 11555篇 |
免费 | 1385篇 |
国内免费 | 10篇 |
出版年
2021年 | 144篇 |
2020年 | 89篇 |
2019年 | 103篇 |
2018年 | 138篇 |
2017年 | 116篇 |
2016年 | 190篇 |
2015年 | 329篇 |
2014年 | 324篇 |
2013年 | 473篇 |
2012年 | 542篇 |
2011年 | 551篇 |
2010年 | 334篇 |
2009年 | 345篇 |
2008年 | 494篇 |
2007年 | 475篇 |
2006年 | 459篇 |
2005年 | 466篇 |
2004年 | 453篇 |
2003年 | 496篇 |
2002年 | 447篇 |
2001年 | 233篇 |
2000年 | 215篇 |
1999年 | 179篇 |
1998年 | 137篇 |
1997年 | 104篇 |
1996年 | 121篇 |
1995年 | 120篇 |
1994年 | 109篇 |
1993年 | 100篇 |
1992年 | 172篇 |
1991年 | 182篇 |
1990年 | 148篇 |
1989年 | 152篇 |
1988年 | 136篇 |
1987年 | 155篇 |
1986年 | 120篇 |
1985年 | 148篇 |
1984年 | 131篇 |
1983年 | 138篇 |
1982年 | 136篇 |
1981年 | 136篇 |
1980年 | 125篇 |
1979年 | 119篇 |
1978年 | 108篇 |
1977年 | 112篇 |
1976年 | 111篇 |
1975年 | 83篇 |
1974年 | 111篇 |
1973年 | 93篇 |
1972年 | 82篇 |
排序方式: 共有10000条查询结果,搜索用时 500 毫秒
21.
B.K. Shaw 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》2000,186(7-8):747-757
Many bird species produce vocalizations which are accompanied by distinctive postural displays, but the neural mechanisms that allow such integrated production of vocal and postural motor patterns are not understood. In the crowing behavior of Japanese quail, a characteristic vocal pattern is accompanied by and coordinated with a postural display that consists of a sequence of rapid, patterned head movements. The purpose of the present study was to investigate the role of a midbrain vocal nucleus, the nucleus intercollicularis, in the production of the acoustic and postural components of crowing in quail. Brief electrical stimuli were applied to the nucleus intercollicularis during spontaneously emitted crows in quail with chronically implanted electrodes, to determine if perturbing neural activity in the nucleus intercollicularis resulted in a disruption of ongoing crowing behavior. The most common effect of such stimuli was a concurrent, premature termination of both the acoustic and head movement components of the crow. These results imply that the nucleus intercollicularis plays a role in the production of both the acoustic and postural components of crowing in quail. 相似文献
22.
Jeffrey Pomerance Richard Johnson Shoba Kagal Philip Brooks Malcolm Margolin Arthur Allen 《The Western journal of medicine》1980,133(4):289-291
Recently, there has been increased interest in the influence of maternal prenatal nutrition on the course and outcome of pregnancy. Evidence has accumulated that a woman''s weight before pregnancy and the weight gained during pregnancy directly affect infant birth weight, incidence of neonatal mortality, and growth and development of the infant during the first year of life. Although recent recommendations for weight gain in pregnancy have been liberalized, a survey of 195 pregnant women who had prenatal visits in both clinic and private offices showed deficiencies in their understanding of the subject. Some 37 percent of women believed they should gain 20 pounds (9 kg) or less during pregnancy. Eight percent admitted to dieting before at least one antenatal visit and 54 percent thought their doctor would not be concerned about too little weight gained during pregnancy. This suggests that many women and some doctors are still ignorant of current concepts of proper nutrition during pregnancy. Apparently, increased lay and professional educational efforts are needed. 相似文献
23.
Deborah Shaw Ian R. Poxton John R.W. Govan 《FEMS immunology and medical microbiology》1995,11(2):99-106
Abstract Burkholderia cepacia has emerged as an important multiresistant pathogen in cystic fibrosis (CF), associated in 20% of colonised patients with a rapid and fatal decline in lung function. Although knowledge of B. cepacia epidemiology has improved, the mechanisms involved in pathogenesis remain obscure. In this study, B. cepacia lipopolysaccharide (LPS) was assessed for endotoxic potential and the capacity to induce tumour necrosis factor (TNF). LPS preparations from clinical and environmental isolates of B. cepacia and from the closely related species Burkholderia gladioli exhibited a higher endotoxic activity and more pronounced cytokine response in vitro compared to preparations from the major CF pathogen Pseudomonas aeruginosa . This study may help to explain the vicious host immune response observed during pulmonary exacerbations in CF patients colonised by B. cepacia and lead to therapeutic advances in clinical management. 相似文献
24.
25.
26.
Banta Arthur M. 《Molecular & general genetics : MGG》1922,29(1):141
27.
Arthur E. Barker 《BMJ (Clinical research ed.)》1911,1(2631):1302-1304
28.
29.
30.
The destruction of spores of Bacillus subtilis by the combined effects of hydrogen peroxide and ultraviolet light 总被引:3,自引:0,他引:3
W.M. Waites S.E. Harding D.R. Fowler S.H. Jones D. Shaw M. Martin 《Letters in applied microbiology》1988,7(5):139-140
Ultraviolet light irradiation of bacterial spores in the presence of hydrogen peroxide has been shown to produce synergistic kills when compared with ultraviolet light (u.v.) and hydrogen peroxide used sequentially. This use in combination has been patented for the commercial sterilization of packaging before filling with UHT-processed products. Previous results have shown that lamps producing u.v. light with a maximum output at about 254 nm were extremely effective. Results obtained using a Synchrotron radiation source to produce a narrow band of irradiation now shows that the greatest kill of spores of Bacillus subtilis in the presence of hydrogen peroxide is obtained with radiation at ˜270 nm. Such results suggest that the action of the u.v. light is not directly on the spore DNA but may be related to the production of free hydroxyl radicals from hydrogen peroxide. 相似文献