全文获取类型
收费全文 | 713篇 |
免费 | 90篇 |
国内免费 | 1篇 |
出版年
2021年 | 8篇 |
2020年 | 5篇 |
2019年 | 13篇 |
2018年 | 4篇 |
2017年 | 18篇 |
2016年 | 11篇 |
2015年 | 27篇 |
2014年 | 17篇 |
2013年 | 30篇 |
2012年 | 26篇 |
2011年 | 35篇 |
2010年 | 31篇 |
2009年 | 16篇 |
2008年 | 16篇 |
2007年 | 28篇 |
2006年 | 25篇 |
2005年 | 35篇 |
2004年 | 31篇 |
2003年 | 26篇 |
2002年 | 37篇 |
2001年 | 18篇 |
2000年 | 20篇 |
1999年 | 18篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 8篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 11篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1988年 | 16篇 |
1987年 | 16篇 |
1986年 | 9篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1977年 | 11篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1974年 | 4篇 |
1973年 | 9篇 |
1970年 | 4篇 |
1966年 | 5篇 |
排序方式: 共有804条查询结果,搜索用时 15 毫秒
1.
Gastrointestinal pH measurement in rats: influence of the microbial flora, diet and fasting 总被引:1,自引:0,他引:1
The pH of the rat intestinal tract was decreased by the presence of a microbial flora, but its influence in the forestomach is less clear. Stomach pH values varied according to the amount of food present at the time of measurement. Fasting increased the pH of the gastrointestinal tract in conventional rats but had little effect in germfree rats. In the conventional rat, feeding a purified diet compared with a commercial diet resulted in a lower pH in the forestomach and a higher pH in the caecal contents. Magnesium trisilicate promoted gastric emptying in conventional rats and its antacid effect was observed only in the caecum and colon. 相似文献
2.
3.
4.
Davis G. M.; Coates A. L.; Papageorgiou A.; Bureau M. A. 《Journal of applied physiology》1988,65(3):1093-1098
The measurement of pulmonary mechanics has been developed extensively for adults, and these techniques have been applied directly to neonates and infants. However, the compliant chest wall of the infant frequently predisposes to chest wall distortion, especially when there is a low dynamic lung compliance (CL,dyn). We describe a technique of directly measuring the static chest wall compliance (Cw,st), developed initially in the newborn lamb and subsequently applied to the premature neonate with chest wall distortion. The mean CL,dyn in seven intubated newborn lambs in normoxia was 2.45 +/- 0.41 ml.cmH2O-1.kg-1, whereas Cw,st was 11.81 +/- 0.25 ml.cmH2O-1.kg-1. These values did not change significantly in seven animals breathing through a tight-fitting face mask or with hypercapnia-induced tachypnea. For the eight premature infants the mean CL,dyn was 1.35 +/- 0.36 ml.cmH2O-1.kg-1, whereas the mean Cw,st was 3.16 +/- 1.01 ml.cmH2O-1.kg-1. This study shows that, under relaxed conditions when measurements of static compliance are performed, the chest wall is more compliant than the lung. The measurement of Cw,st may thus be used to determine the contribution of the respiratory musculature in stabilizing the chest wall. 相似文献
5.
Stephen F. Lincoln Andrea M. Hounslow Bruce G. Doddridge John M. Coates 《Inorganica chimica acta》1985,100(2):207-210
Proton NMR studies of N,N-diethylformamide (def) exchange on [M(Me6tren)def]2+ where M = Co and Cu yield: kex (298.2K) = 26.3 ± 2.2, 980 ± 70 s−1; ΔH≠ = 58.3 ± 1.7, 36.3 ± 0.9 kJ mol−1; ΔS≠= −22.2 ± 4.6, −65.9 ± 2.5 J K−1 mol−1; and ΔV≠ = −1.3 ± 0.2, 5.3 ± 0.3 cm3 mol−1 respectively. These data which are consistent with a and d activation modes operating when M = Co and Cu respectively are compared with data for related systems. 相似文献
6.
7.
Efficacy of a variety of disinfectants against Listeria spp 总被引:1,自引:0,他引:1
The efficacy of 14 disinfectants against Listeria innocua and two strains of Listeria monocytogenes in the presence of organic matter was studied. Quantitative efficacy tests were used. Many of the disinfectants tested were not as effective on Listeria spp. when the test organisms were dried onto the surface of steel disks (carrier tests) as they were when the organisms were placed in suspension (suspension test). The presence of whole serum and milk (2% fat) further reduced the disinfectant capacities of most of the formulations studied. Only three disinfectants (povidone-iodine, chlorhexidine gluconate, and glutaraldehyde) were effective in the carrier test in the presence of serum; however, all three were ineffective when challenged with milk (2% fat). Only one solution, sodium dichloroisocyanurate, was effective in the presence of milk. All but four formulations (chloramine-T, phosphoric acid, an iodophor, and formaldehyde) were effective in the suspension tests, regardless of the organic load. L. monocytogenes was observed to be slightly more resistant to disinfection than L. innocua was. There was no difference in disinfectant susceptibility between the two strains of L. monocytogenes. These findings emphasize the need for caution in selecting an appropriate disinfectant for use on contaminated surfaces, particularly in the presence of organic material. 相似文献
8.
Rosamond C. H. Shepherd 《BioControl》1990,35(3):441-447
Host specificity tests of the moth,Microthrix inconspicuella Ragonot in Australia, indicated that larvae could feed and develop on young apple leaves. Additional tests in South Africa
on leaves and fruit of the 4 apple varieties, Jonathan, Starking (Red Delicious), Granny Smith and Golden Delicious, showed
that apples were not a preferred food. Little feeding occurred and pupation happened infrequently. No 2nd generation resulted whenM. inconspicuella colonies were confined on apple fruit or leaves.
相似文献
9.
Oligochaetes (Naididae,Tubificidae, Enchytraeidae and Alluroididae) of Guyana,Peru and Ecuador 总被引:2,自引:2,他引:0
More than 41 species in 23 genera of the microdrile oligochaete families Tubificidae, Naididae, Opistocystidae, and Enchytraeidae and the freshwater megadrile family Alluroididae have been identified in recent collections made in Peru, Guyana and Ecuador. Just less than 70% of our species records are new for one or more of these countries and one is a new, albeit tentative, generic record for the South American continent. About 16 species new to science remain to be described. One of these is only the second reported species of Brinkhurstia (Alluroididae) and possesses unusual, single, very elongate penial setae. All of our species records are pertinent to tests of different hypotheses about historical and phylogenetic relationships among organisms of northern and southern South America and North America. The species, including new ones, with limited distributions are of particular significance to such hypotheses. 相似文献
10.
Gavin Sherlock A. Majeed Bahman Amarbirpal Mahal Jia-Ching Shieh Miguel Ferreira John Rosamond 《Molecular genetics and genomics : MGG》1994,245(6):716-723
In the budding yeast Saccharomyces cerevisiae, progress of the cell cycle beyond the major control point in G1 phase, termed START, requires activation of the evolutionarily conserved Cdc28 protein kinase by direct association with GI cyclins. We have used a conditional lethal mutation in CDC28 of S. cerevisiae to clone a functional homologue from the human fungal pathogen Candida albicans. The protein sequence, deduced from the nucleotide sequence, is 79% identical to that of S. cerevisiae Cdc28 and as such is the most closely related protein yet identified. We have also isolated from C. albicans two genes encoding putative G1 cyclins, by their ability to rescue a conditional GI cyclin defect in S. cerevisiae; one of these genes encodes a protein of 697 amino acids and is identical to the product of the previously described CCN1 gene. The second gene codes for a protein of 465 residues, which has significant homology to S. cerevisiae Cln3. These data suggest that the events and regulatory mechanisms operating at START are highly conserved between these two organisms. 相似文献