全文获取类型
收费全文 | 1089315篇 |
免费 | 116374篇 |
国内免费 | 971篇 |
专业分类
1206660篇 |
出版年
2018年 | 10525篇 |
2017年 | 9994篇 |
2016年 | 14211篇 |
2015年 | 18925篇 |
2014年 | 22338篇 |
2013年 | 31817篇 |
2012年 | 35936篇 |
2011年 | 37183篇 |
2010年 | 25153篇 |
2009年 | 23211篇 |
2008年 | 33120篇 |
2007年 | 34223篇 |
2006年 | 32124篇 |
2005年 | 30814篇 |
2004年 | 30664篇 |
2003年 | 29209篇 |
2002年 | 28504篇 |
2001年 | 45274篇 |
2000年 | 44848篇 |
1999年 | 36097篇 |
1998年 | 13905篇 |
1997年 | 13984篇 |
1996年 | 13184篇 |
1995年 | 12419篇 |
1994年 | 11913篇 |
1993年 | 11940篇 |
1992年 | 29902篇 |
1991年 | 29433篇 |
1990年 | 28810篇 |
1989年 | 28096篇 |
1988年 | 25867篇 |
1987年 | 24650篇 |
1986年 | 23227篇 |
1985年 | 23186篇 |
1984年 | 19175篇 |
1983年 | 16768篇 |
1982年 | 12796篇 |
1981年 | 11664篇 |
1980年 | 10768篇 |
1979年 | 18015篇 |
1978年 | 14388篇 |
1977年 | 13054篇 |
1976年 | 12316篇 |
1975年 | 13914篇 |
1974年 | 14996篇 |
1973年 | 14751篇 |
1972年 | 13422篇 |
1971年 | 12107篇 |
1970年 | 10581篇 |
1969年 | 10338篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
261.
A new internal perfusion method has been developed which allows control of the internal solute composition in squid axons. The superiority of this technique compared to the old perfusion methods is shown by the experiments performed which have reproduced, both qualitatively and quantitatively, the Na+ and Ca2+ fluxes observed in intact and dialyzed axons. Compared with the internal dialysis, the perfusion method has the advantage that the permeability barrier give by the porous capillary has been eliminated. This allows the introduction into the axon of solutes with very high molecular weight, at the same time that a fast and reliable internal control can be achieved. 相似文献
262.
263.
M C Brown G C Lunt A Stapleton 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1989,92(1):9-13
1. Using homogenates of supraoesophageal ganglia from locust we observed specific binding of [35S]-TBPS which was linear with protein concentration up to 7 mg/ml, showed a pH optimum at pH 9.0 and was linear with NaCl concentration up to 350 mM. 2. Kinetic analysis of the binding showed positive cooperativity as a result of changes in on and off-rates with occupation of the binding site by the ligand. The apparent KD = 417 nM and Bmax = 1083 fmol/mg of membrane protein were calculated using a computer program for dose-response curve fitting. 3. The binding was enhanced by GABA, pentobarbital and benzodiazepines. Picrotoxinin had no effect on the binding at 0.1 mM. Only the cage convulsants TBPS and IBP were able to displace the binding. 4. Whilst the characteristics of the binding are similar to those reported for house fly thorax and abdomen preparations they are significantly different from those reported for house fly head, cockroach nerve cord and rat brain. 相似文献
264.
A polyclonal antibody to ubiquitin has been prepared and shown to react with both ubiquitin and ubiquitinated histone 2A (uH2A). Applying this antibody in Western blotting experiments, we have observed that the salivary glands of Chironomus tentans contain an unusually low amount of uH2A (1% of histone 2A), while the amount of free ubiquitin is as abundant as in other animal cells, e.g. HeLa cells. The same low content of uH2A was also found in diploid epidermal cells of Chironomus origin suggesting that the low amount is not a characteristic of the polytene state of chromatin in salivary gland cells but rather a property of C. tentans as a species. The significance of the low degree of ubiquitination is discussed in relation to the information available on the organization of Chironomus chromatin into unusually large chromomeric entities. 相似文献
265.
Y Wattanagoon R E Phillips D A Warrell K Silamut S Looareesuwan B Nagachinta D J Back 《BMJ (Clinical research ed.)》1986,293(6538):11-13
In a study of intramuscular injection of quinine eight adults with moderately severe falciparum malaria resistant to chloroquine were treated with quinine dihydrochloride, being given a loading dose of 20 mg salt (16.7 mg base)/kg followed by three or four eight hourly maintenance doses of 10 mg salt (8.3 mg base)/kg injected into the anterior thigh. All patients responded to treatment. Fever and parasite clearance times (mean (SD) 60 (23) h and 53 (22) h respectively) were comparable with those obtained with intravenous quinine. The mean peak plasma quinine concentration of 11.0 mg/l (34.4 mu mol/l) [corrected] was reached a median of five hours after administration of the loading dose. In all patients plasma quinine concentrations exceeded the high minimum inhibitory concentration for Plasmodium falciparum malaria prevalent in Thailand within four hours of the start of treatment but did not cause toxicity other than mild cinchonism. When intravenous infusion is not possible an intramuscular quinine loading dose is an effective means of starting treatment in patients with moderately severe falciparum malaria who cannot swallow tablets. 相似文献
266.
In this paper the recent population changes of the Wild Boar in different European countries is analysed through the study of hunting statistics. A simultaneous increase in numbers is observed throughout the whole area during the period 1965–1975. From 1975 onwards the population stabilizes itself apart from in peripheral areas like Finland. Potentially favourable factors which play a part in this process are discussed and certain reproductive and dispersive characteristics which favour its invasive behaviour are discussed. 相似文献
267.
268.
269.
Three methods of analysis were used to determine the diet of territorial hooded crows at Lough Hyne Marine Reserve, Co Cork, Ireland The regular collection of prey Items from these sites at Lough Hyne was integrated with pellet and stomach analysis to determine diet Intertidal organisms occurred in over 80% of pellets and 43% of stomachs and occupied over 77% of the total wet weight of foods identified in pellets All prey items recovered from drop sites originated from the intertidal habitat, involved either large-sized species or larger individuals of smaller-sized species, and were only dropped during October to February Twenty-five intertidal species were identified but only a few of these species contributed to the bulk of the diet Hooded crows were shown to consume a wide range of intertidal species throughout the year, though the species composition in the diet was seasonally influenced Depletion and weight loss of intertidal molluscs through the winter was shown to have a minimal effect on selection suggesting that prey switching was driven by the birds nutritional requirements 相似文献
270.
The method for obtaining antisera to meningococci of different serotypes are described and the scheme for the preparation of serotyping is presented, as well as the method for the preparation of the determinate fraction of serotype 2. Antisera to typing antigens 1, 2, 2-7, 2-10, 4, 5, 6, 8 (1) have been obtained, their specificity tested in parallel experiments with American and French typing sera. When typing meningococci, the use of antisera to purified protein antigen 2 is recommended. 相似文献