全文获取类型
收费全文 | 769492篇 |
免费 | 90005篇 |
国内免费 | 427篇 |
专业分类
859924篇 |
出版年
2018年 | 6608篇 |
2017年 | 6320篇 |
2016年 | 9189篇 |
2015年 | 12995篇 |
2014年 | 14827篇 |
2013年 | 21489篇 |
2012年 | 24315篇 |
2011年 | 24531篇 |
2010年 | 16459篇 |
2009年 | 15188篇 |
2008年 | 21899篇 |
2007年 | 22516篇 |
2006年 | 20856篇 |
2005年 | 20166篇 |
2004年 | 19839篇 |
2003年 | 19105篇 |
2002年 | 18511篇 |
2001年 | 34872篇 |
2000年 | 35260篇 |
1999年 | 28436篇 |
1998年 | 10300篇 |
1997年 | 10711篇 |
1996年 | 10342篇 |
1995年 | 9457篇 |
1994年 | 9642篇 |
1993年 | 9372篇 |
1992年 | 23313篇 |
1991年 | 22286篇 |
1990年 | 21984篇 |
1989年 | 21866篇 |
1988年 | 19743篇 |
1987年 | 18926篇 |
1986年 | 17514篇 |
1985年 | 17411篇 |
1984年 | 14515篇 |
1983年 | 12684篇 |
1982年 | 9812篇 |
1981年 | 8778篇 |
1980年 | 8326篇 |
1979年 | 13848篇 |
1978年 | 10746篇 |
1977年 | 9727篇 |
1976年 | 9312篇 |
1975年 | 10020篇 |
1974年 | 10622篇 |
1973年 | 10419篇 |
1972年 | 9485篇 |
1971年 | 8613篇 |
1970年 | 7409篇 |
1969年 | 7032篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
E Imbasciati R Gusmano A Edefonti P Zucchelli C Pozzi C Grassi M Della Volpe F Perfumo P Petrone M Picca et al. 《BMJ (Clinical research ed.)》1985,291(6505):1305-1308
In a multicentre, randomised, prospective trial 89 patients (67 children and 22 adults) with the minimal change nephrotic syndrome were treated with three intravenous pulses of methylprednisolone followed by low dose oral prednisone for six months (group given methylprednisolone) or with high dose oral prednisone for four weeks followed by low dose oral prednisone for five months (control group). Five patients in the group given methylprednisolone and one in the control group did not respond initially. The time to response was shorter in children treated with methylprednisolone. No significant differences between the two groups were observed in the number of patients who relapsed or number of relapses per patient per year. Patients given methylprednisolone tended to relapse earlier than patients in the control group. Side effects related to treatment were significantly fewer in the group given methylprednisolone than in the control group. These data suggest that a short course of methylprednisolone pulses followed by low dose oral prednisone is only marginally less effective than a regimen of high dose oral steroids but can improve the ratio of risk to benefit associated with treatment of the minimal change nephrotic syndrome. 相似文献
112.
Monosomy 21: a new case confirmed by in situ hybridization 总被引:4,自引:0,他引:4
M. C. Pellissier N. Philip M. A. Voelckel-Baeteman M. G. Mattei J. F. Mattei 《Human genetics》1987,75(1):95-96
Summary A new case of total monosomy 21 in a newborn is described. The diagnosis was first made using the cytogenetic data; it was then confirmed by the dosage of copper-superoxide dismutase (SOD-1) which showed a 50% decrease. In situ hybridization with a probe previously assigned to chromosome 21 was used to rule out the possibility of a partial monosomy with an unbalanced reciprocal translocation. 相似文献
113.
P Avril R Ducroc B Garzon E Moreau F Hervatin P Millet J P Geloso 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1986,303(18):739-742
Sensitivity of the developing rat stomach to histamine (HA) was examined on isolated gastric mucosae of rats of various ages from the fetal to adult periods. Spontaneous acid secretion in mu eq/h.cm2 occurred at all the ages studied, at a basal rate of 0.45 +/- 0.07 in fetuses to 0.22 +/- 0.03 (day 5), 0.11 +/- 0.04 (day 10), 0.12 +/- 0.04 (day 12), 0.22 +/- 0.08 (day 16) and 0.33 +/- 0.04 (adults). In the fetal rats as in the adults, marked responses to respectively 10(-5) and 10(-4) M HA were demonstrated. The H2-receptor antagonist cimetidine diminished HA-induced secretion by 66 and 57% in fetuses and adults respectively. Between these two stages (from days 5 to 12), basal secretion and the response to HA dropped significantly. On day 21 of gestation, as well as on the critical days 5 and 12 after parturition, db-cAMP (10(-4) M) caused maximal stimulation of acid secretion. These results indicate that the development of responsiveness to HA in the rat is biphasic. They suggest that after birth, the H2-receptor adenylate cyclase system undergoes major modifications which might lead to the complete lack of responsiveness to HA by day 12. 相似文献
114.
A series of measurements of blood pressure in normotensive and hypertensive subjects showed that measurements made with a sphygmomanometer with the arm dependent by the side were consistently higher than those made with the arm horizontal at heart level. The mean difference in a group of 90 hypertensive outpatients was 11/12 mm Hg. Failure to appreciate the importance of arm position may lead to erroneous measurements of blood pressure. This has important implications for clinical practice and research. 相似文献
115.
Genes for the biosynthesis of spinosyns: applications for yield improvement in Saccharopolyspora spinosa 总被引:2,自引:0,他引:2
K Madduri C Waldron P Matsushima M C Broughton K Crawford D J Merlo R H Baltz 《Journal of industrial microbiology & biotechnology》2001,27(6):399-402
Spinosyns A and D are the active ingredients in an insect control agent produced by fermentation of Saccharopolyspora spinosa. Spinosyns are macrolides with a 21-carbon, tetracyclic lactone backbone to which the deoxysugars forosamine and tri-O-methylrhamnose are attached. The spinosyn biosynthesis genes, except for the rhamnose genes, are located in a cluster that
spans 74 kb of the S. spinosa genome. DNA sequence analysis, targeted gene disruptions and bioconversion studies identified five large genes encoding type
I polyketide synthase subunits, and 14 genes involved in sugar biosynthesis, sugar attachment to the polyketide or cross-bridging
of the polyketide. Four rhamnose biosynthetic genes, two of which are also necessary for forosamine biosynthesis, are located
outside the spinosyn gene cluster. Duplication of the spinosyn genes linked to the polyketide synthase genes stimulated the
final step in the biosynthesis — the conversion of the forosamine-less pseudoaglycones to endproducts. Duplication of genes
involved in the early steps of deoxysugar biosynthesis increased spinosyn yield significantly. Journal of Industrial Microbiology & Biotechnology (2001) 27, 399–402.
Received 31 May 2001/ Accepted in revised form 09 July 2001 相似文献
116.
117.
The heart rate and respiratory patterns in hypoxia are not well documented in unanaesthetized intact newborn animals. We studied heart rate and respiratory patterns during quiet sleep in 17% inspired O2 in 31 unanaesthetized newborns of five species: lamb, piglet, puppy, kitten, and rabbit. There was no significant change in mean heart rate and respiratory rate with hypoxia for any species. Brief apneas greater than 5 s were frequent (5-8/h), both in 21 and 17% O2 only in lambs and puppies. No sustained periodic breathing was induced by hypoxia. Thus, mild hypoxia has little steady-state effect on heart rate and respiratory rate and pattern in these unanaesthetized newborns. These findings are compatible with depressed chemoreceptor threshold, but indicate a remarkably mature respiratory pattern in full-term newborns of these species. 相似文献
118.
119.
120.