全文获取类型
收费全文 | 320700篇 |
免费 | 15777篇 |
国内免费 | 934篇 |
专业分类
337411篇 |
出版年
2021年 | 2034篇 |
2019年 | 1843篇 |
2018年 | 14724篇 |
2017年 | 13461篇 |
2016年 | 11178篇 |
2015年 | 4236篇 |
2014年 | 5161篇 |
2013年 | 7131篇 |
2012年 | 12274篇 |
2011年 | 21083篇 |
2010年 | 17693篇 |
2009年 | 13101篇 |
2008年 | 17079篇 |
2007年 | 18866篇 |
2006年 | 7736篇 |
2005年 | 7461篇 |
2004年 | 8010篇 |
2003年 | 7770篇 |
2002年 | 7475篇 |
2001年 | 9579篇 |
2000年 | 9138篇 |
1999年 | 7047篇 |
1998年 | 2166篇 |
1997年 | 2003篇 |
1996年 | 1853篇 |
1992年 | 5506篇 |
1991年 | 5728篇 |
1990年 | 5666篇 |
1989年 | 5631篇 |
1988年 | 5241篇 |
1987年 | 4882篇 |
1986年 | 4453篇 |
1985年 | 4687篇 |
1984年 | 3712篇 |
1983年 | 3046篇 |
1982年 | 2019篇 |
1980年 | 1730篇 |
1979年 | 3341篇 |
1978年 | 2583篇 |
1977年 | 2380篇 |
1976年 | 2336篇 |
1975年 | 2834篇 |
1974年 | 3120篇 |
1973年 | 3087篇 |
1972年 | 2991篇 |
1971年 | 2871篇 |
1970年 | 2217篇 |
1969年 | 2161篇 |
1968年 | 2037篇 |
1967年 | 1799篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
P N Deriabin B V Karal'nik N P Vaneeva 《Zhurnal mikrobiologii, epidemiologii, i immunobiologii》1984,(8):47-52
Species-specific (Staphylococcus aureus and S. epidermidis) antigenic and antibody erythrocyte diagnosticums have been prepared. Various tests made with the use of these diagnosticums have demonstrated that the activity of specific antigens is higher in hydrochloric acid extracts than in trichloroacetic and phenolic ones; this activity is linked with undialyzed components and depends on the peculiar features of the strain. 相似文献
992.
993.
The influence of dibunol, phenazepam used alone and combined on rat conflict behavior and rat blood and brain malonic dialdehyde content was studied. It was shown that dibunol exerts an unmarked anticonflict action that can be removed by bicuculline. Combined administration of dibunol and phenazepam potentiates appreciably the anticonflict effect. This permits reducing the doses of the drugs. The anxiolytic effect of dibunol alone and combined with phenazepam is attended by a decrease in the content of malonic dialdehyde in rat blood and brain, evidence of the reduction of the lipid peroxidation intensity. 相似文献
994.
995.
Nitrogen is the major growth-limiting nutrient for marine algae. One potential source of nitrogen for marine algae is ammonium released by invertebrates. Many mid-intertidal reefs in northeastern New Zealand are dominated by a close association between the honeycomb barnacle Chamaesipho columna and an encusting brown alga Pseudolithoderma sp. Growth of Pseudolithoderma was enhanced in the presence of live C. columna, which released ammonium at a greater rate than the maximum rate of ammonium uptake by Pseudolithoderma. Algal tissue on barnacle tests had a lower C:N ratio than tissue located more than 2 cm from the nearest barnacle, suggesting the barnacle is an important source of nitrogen for the alga. The role of nutrient exchange in determining ecological patterns of species in marine communities is discussed. 相似文献
996.
O E Kolesova G V Leont'eva L A Apollonova R Kh Chilingirov Iu I Bobkov 《Biulleten' eksperimental'no? biologii i meditsiny》1986,101(3):282-284
The method of intravenous administration of UV-irradiated donor plasma to patients with jaundice of different genesis has been tested in the experiments on rats and used clinically in 20 patients. Biochemical and morphological studies have shown that such treatment causes stable improvement in the liver functional state. 相似文献
997.
L V Antonova A A Kamenski? T I Vlasova N Iu Sarycheva V N Nezavibat'ko 《Biulleten' eksperimental'no? biologii i meditsiny》1986,102(11):569-571
Heptapeptide Met-Glu-His-Phe-Pro-Gly-Pro (ACTH4-10 analog) at a dose of 0.015 mg/kg failed to alter open field behaviour of rats in the first test series. The peptide abolished amphetamine-induced stimulation of the exploratory and grooming behaviour. Extinction of the rats' exploratory behaviour during second test series in the open field (7 days later) was disturbed when haloperidol or apomorphine were injected before the first test series. When the peptide was administered with haloperidol or apomorphine, the extinction tended to become normal. Heptapeptide failed to change noradrenaline, dopamine or 5-hydroxytryptamine content in the rat forebrain. However, this peptide at a concentration of 10(-4) M moderately diminished tyrosine hydroxylation velocity in the rat striatal or hypothalamic synaptosomes, the effect depending on tyrosine concentration. These data suggest the involvement of catecholaminergic component into the heptapeptide action on the behaviour of rats. 相似文献
998.
P. N. Hoffman E. M. Cooke D. P. Larkin L. J. Southgate R. T. Mayon-White J. V. Pether A. E. Wright D. Keenlyside 《BMJ (Clinical research ed.)》1988,297(6640):34-36
Twenty general practices in four areas in Britain were surveyed to establish their needs for and practices of sterilising and disinfecting equipment. Of the 327 items of equipment and instruments examined in the survey, 190 were satisfactorily decontaminated, 100 were treated in a way judged to result in doubtful decontamination, and in 37 cases treatment was considered unsatisfactory. Decontamination apparatuses (autoclaves, hot air ovens, and hot water disinfectors) were generally in good working order, but the use of chemical disinfectants was often inappropriate. Recommendations were made on appropriate methods of decontamination for various items in common use in general practice. By virtue of the large numbers of patients treated by general practitioners there is a substantial possibility of transmitting infection; having appropriate methods for decontaminating instruments and equipment is therefore imperative. 相似文献
999.
1000.
We describe a 26-year-old patient with 17-ketoreductase deficiency who was raised as a male from 8 months and whose left testis was brought down at the age of 2.5 years and the right testis at the age of 4. Despite the early orchidopexy and not significantly decreased serum testosterone, he was sterile, and biopsy of the testes at the age of 26 revealed absence of spermatogenesis. This case indicates that the absence of spermatogonia in previously reported patients whose testes remained undescended until a later age could not be attributed solely to cryptorchidism. We suggest that decreased intratesticular testosterone due to steroidogenic defect in the developing testis mainly contributes to the arrest of spermatogenesis. 相似文献