全文获取类型
收费全文 | 303920篇 |
免费 | 35361篇 |
国内免费 | 689篇 |
出版年
2018年 | 2843篇 |
2017年 | 2595篇 |
2016年 | 3570篇 |
2015年 | 4744篇 |
2014年 | 5665篇 |
2013年 | 7638篇 |
2012年 | 8751篇 |
2011年 | 8819篇 |
2010年 | 5731篇 |
2009年 | 5531篇 |
2008年 | 7715篇 |
2007年 | 7834篇 |
2006年 | 7628篇 |
2005年 | 7305篇 |
2004年 | 7129篇 |
2003年 | 6901篇 |
2002年 | 6714篇 |
2001年 | 17432篇 |
2000年 | 17595篇 |
1999年 | 13438篇 |
1998年 | 3939篇 |
1997年 | 4223篇 |
1996年 | 3937篇 |
1995年 | 3560篇 |
1994年 | 3535篇 |
1993年 | 3610篇 |
1992年 | 10467篇 |
1991年 | 10393篇 |
1990年 | 9863篇 |
1989年 | 9682篇 |
1988年 | 9029篇 |
1987年 | 8396篇 |
1986年 | 7585篇 |
1985年 | 7441篇 |
1984年 | 5839篇 |
1983年 | 5088篇 |
1982年 | 3623篇 |
1981年 | 3188篇 |
1980年 | 3034篇 |
1979年 | 5356篇 |
1978年 | 4125篇 |
1977年 | 3752篇 |
1976年 | 3302篇 |
1975年 | 3783篇 |
1974年 | 3953篇 |
1973年 | 3893篇 |
1972年 | 3429篇 |
1971年 | 3189篇 |
1970年 | 2823篇 |
1969年 | 2743篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
941.
942.
J M Al-Hassan M Afzal M Ali M Thomson T Fatima S Fayad R S Criddle 《Comparative biochemistry and physiology. B, Comparative biochemistry》1986,85(1):41-47
Lipids associated with a threat induced epidermal gel secretion from the catfish, Arius thalassinus, have been analyzed. Phospholipids, neutral lipids and glycolipids are all present and each of these subclasses has been analyzed by thin layer and gas chromatography with a general similarity with membrane lipids being noted. The epidermal gel lipids differed from total liver lipids of the catfish. Fatty acid analysis showed the gel lipid to be rich in the unsaturated fatty acids: oleate (omega 7, C18:1), arachidonate (omega 6, C20:4), and docosahexaenoate (omega 3, C22:6). Some prostaglandins were quantitated in lipid extracts from the epidermal gel. 相似文献
943.
944.
945.
946.
Rutherford T. Johnstone 《The Western journal of medicine》1956,84(4):265-268
Within the past decade the chemist has evolved a new group of insecticides having a greater range of toxicity to insects—and to man. Since their use is ubiquitous, it is imperative that information be widely disseminated regarding proper cautionary measures as well as the early signs and symptoms of toxicity. 相似文献
947.
The arid zone scorpion Urodacus yaschenkoi (Birula 1903) is shown to have six instars. Instars can be recognized by measuring the claws and the carapace plus first five tail segments. A population study, carried out at Coombah, NSW, showed that the life history consisted of mating in September–October, 18 month gestation, birth in February-March, moult to second instar March-April and annual moults to sixth instar in December–February. The minimum generation time was 6 y, and the population appeared to be stable. The calendar of catches method was used to determine the population size (about 400 animals in 2240 m2) but required some extra assumptions to cope with loss of marks from individuals when they moulted. 相似文献
948.
R. Brändén T. Nilsson S. Styring 《Biochemical and biophysical research communications》1980,92(4):1297-1305
A sensitive and reliable method to determine the stereochemical composition of 3-phosphoglyceric acid is presented. Results obtained with this method show that 3-phosphoglyceric acid formed in the ribulose-1,5-bisphosphate carboxylase reaction is a mixture of 10% L-3-PGA and 90% D-3-PGA. 相似文献
949.
Nine schizophrenic patients participated in a study which explored whether EEG feedback techniques could effect changes in the EEG similar to those associated with neuroleptic-induced improvement. During five sessions, each patient was presented feedback signals which continuously refected the discrepancy between characteristics of the patient's EEG power spectral profile and spectral profile characteristics associated by past research with neuroleptic induced clinical improvement. Significant within-session changes were observed for two of three EEG power spectrum bands of interest. No significant session-to-session EEG changes were observed. The results suggest that the EEG of schizophrenics can be temporarily altered, using feedback techniques, in a way that mimics the EEG changes that have been shown to occur with neuroleptic induced clinical improvement.The authors are indebted to Turan M. Itil, John W. Fredrickson, Michael Madwed, and Irene B. Francis. Senior authorship is shared equally. 相似文献
950.