全文获取类型
收费全文 | 293019篇 |
免费 | 34532篇 |
国内免费 | 152篇 |
专业分类
327703篇 |
出版年
2018年 | 2399篇 |
2016年 | 3085篇 |
2015年 | 4034篇 |
2014年 | 4913篇 |
2013年 | 6734篇 |
2012年 | 7697篇 |
2011年 | 7906篇 |
2010年 | 5200篇 |
2009年 | 5031篇 |
2008年 | 7143篇 |
2007年 | 7320篇 |
2006年 | 7202篇 |
2005年 | 6920篇 |
2004年 | 6782篇 |
2003年 | 6614篇 |
2002年 | 6464篇 |
2001年 | 17258篇 |
2000年 | 17444篇 |
1999年 | 13301篇 |
1998年 | 3861篇 |
1997年 | 4127篇 |
1996年 | 3851篇 |
1995年 | 3487篇 |
1994年 | 3466篇 |
1993年 | 3540篇 |
1992年 | 10386篇 |
1991年 | 10316篇 |
1990年 | 9804篇 |
1989年 | 9635篇 |
1988年 | 8990篇 |
1987年 | 8356篇 |
1986年 | 7556篇 |
1985年 | 7407篇 |
1984年 | 5823篇 |
1983年 | 5074篇 |
1982年 | 3612篇 |
1981年 | 3179篇 |
1980年 | 3030篇 |
1979年 | 5349篇 |
1978年 | 4114篇 |
1977年 | 3749篇 |
1976年 | 3299篇 |
1975年 | 3776篇 |
1974年 | 3947篇 |
1973年 | 3891篇 |
1972年 | 3421篇 |
1971年 | 3183篇 |
1970年 | 2822篇 |
1969年 | 2741篇 |
1968年 | 2412篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
Mirror carp were infected with Ichthyophthirius multifiliis (Fouquet) under standardized conditions. The size and number of parasites at selected sites on the body were recorded during the course of the infection. Initial exposure to 40 mature parasites resulted in a mild infection with 100% recovery after 18 days. Recovered fish did not appear to be carriers of the parasite. Exposure to 400 parasites resulted in 100% mortality between 22–25 days. The growth rate of the parasite was linear. Parasites were more numerous in the dorsal surface of the fish than in the lateral or ventral surface. The increase in parasite numbers during the disease was greater in the gills than in the skin. 相似文献
172.
173.
174.
175.
M. de Kwaadsteniet C. A. van Reenen L. M. T. Dicks 《Probiotics and antimicrobial proteins》2010,2(2):61-65
The potential of nisin F as an antimicrobial agent in treating subcutaneous skin infections was tested in vivo by infecting C57BL/6 mice with a bioluminescent strain of Staphylococcus aureus (Xen 36). Strain Xen 36 has the luxABCDE operon located on a native plasmid. Mice were grouped into four groups: Infected with strain Xen 36 and treated with nisin F, infected with strain Xen 36 and treated with saline (placebo), not infected and treated with nisin (control) and not infected and not treated (control). The immune systems of the mice were suppressed with deksamethasone. Mice were treated with either nisin F or sterile physiological saline 24 and 48 h after infection with subcutaneously injected S. aureus Xen 36 (4 × 106 CFU). Histology and bioluminescent flux measurements revealed no significant difference between infected mice treated with nisin and saline, respectively. However, infected mice treated with nisin F had an increased number of polymorphonuclear cells when compared with infected mice treated with saline. Also, not infected mice treated with nisin F had an influx of polymorphonuclear cells. Nisin F is thus ineffective in combating deep dermal staphylococcal infections. The apparent immune modulation of nisin when subcutaneously injected has to be investigated. 相似文献
176.
177.
The capillaries of the cardiac muscle were investigated in the goat by means of light microscopy, transmission electron microscopy and scanning electron microscopy, and the following results were obtained. The capillaries of the working cardiac muscles were numerous, arranged mainly parallel to the long axis of muscle cells and formed dense elongated networks. On the contrary, those of the terminal Purkinje fibers were relatively few in number, oriented in various directions and formed loose and circularly meshed networks surrounding the fibers. Such findings were discussed in correlation with the physiology and functional morphology of various types of the cardiac muscle cells. 相似文献
178.
T S Il'ina 《Genetika》1986,22(11):2572-2582
The published data on molecular mechanisms of transposons movement inside and between genomes are reviewed. The replicative mechanism of transposition of the family of Tn3-like elements is discussed, as well as the modes of bacteriophage Mu, Tn9, Tn10, Tn903 transposition. The factors affecting the choice of transposition pathways are analysed. 相似文献
179.
The [3H]ketanserin binding characteristics in the apomorphine-induced aggressive and nonaggressive adult male Wistar rats were studied. Repeated apomorphine (0.5 mg/kg, once daily) treatment gradually induced aggressive behaviour in sixteen animals from twenty. Thereafter the animals were retrospectively divided into apomorphine-induced aggressive and nonaggressive group. The maximal number of the [3H]ketanserin binding sites was increased in the apomorphine-treated animals in the frontal (233.9+/-26.5, 364.6+/-31.7, and 367.0+/-34.8 fmol/mg protein for the vehicle, apomorphine-nonaggressive, and apomorphine-aggressive group, respectively) and cerebral cortex (164.2+/-6.7, 289.7+/-29.3, and 249.0+/-15.4 fmol/mg protein for the vehicle, apomorphine-nonaggressive, and apomorphine-aggressive group, respectively). In conclusion, our experiments demonstrate that repeated apomorphine treatment upregulates the maximal number of the 5-HT2A receptors in rat frontal and cerebral cortex as measured by [3H]ketanserin binding and this phenomenon is independent from the development of aggressive behaviour. 相似文献
180.