全文获取类型
收费全文 | 748772篇 |
免费 | 77581篇 |
国内免费 | 383篇 |
出版年
2018年 | 6693篇 |
2017年 | 6617篇 |
2016年 | 10269篇 |
2015年 | 15681篇 |
2014年 | 17131篇 |
2013年 | 22722篇 |
2012年 | 24593篇 |
2011年 | 22648篇 |
2010年 | 15800篇 |
2009年 | 14779篇 |
2008年 | 18896篇 |
2007年 | 19408篇 |
2006年 | 18317篇 |
2005年 | 23023篇 |
2004年 | 21452篇 |
2003年 | 19395篇 |
2002年 | 17035篇 |
2001年 | 33943篇 |
2000年 | 33911篇 |
1999年 | 27549篇 |
1998年 | 9095篇 |
1997年 | 9443篇 |
1996年 | 9010篇 |
1995年 | 8376篇 |
1994年 | 8444篇 |
1993年 | 8119篇 |
1992年 | 23404篇 |
1991年 | 22769篇 |
1990年 | 22247篇 |
1989年 | 21944篇 |
1988年 | 20165篇 |
1987年 | 19064篇 |
1986年 | 17493篇 |
1985年 | 17584篇 |
1984年 | 14034篇 |
1983年 | 12221篇 |
1982年 | 9049篇 |
1981年 | 8008篇 |
1980年 | 7592篇 |
1979年 | 13529篇 |
1978年 | 10302篇 |
1977年 | 9249篇 |
1976年 | 8695篇 |
1975年 | 9809篇 |
1974年 | 10379篇 |
1973年 | 10266篇 |
1972年 | 9381篇 |
1971年 | 8278篇 |
1970年 | 7445篇 |
1969年 | 6956篇 |
排序方式: 共有10000条查询结果,搜索用时 859 毫秒
951.
952.
L N Kobylianski? 《Biulleten' eksperimental'no? biologii i meditsiny》1984,98(10):425-427
The total and unsedimentable activity of acid DNase, RNase, phosphatase and arylsulfatases A and B was examined in the rat kidneys during long-term compression of soft tissues in the presence of high excitability of the sympathoadrenal system. Injection of adrenalin to rats with trauma reduced the total activity of DNase, acid phosphatase and arylsulfatases A and B, particularly at the late periods of soft tissue compression, whereas the total activity of acid RNase slightly increased as compared with control. Compression of soft tissues after adrenalin preinjection was accompanied by a substantial rise of unsedimentable activity of the lysosomal enzymes under study in the kidneys. The activity of the enzymes in cytosol progressively ascended as the time of soft tissue injury increased. 相似文献
953.
Cyclic AMP is not detectable in Clostridium perfringens 总被引:3,自引:0,他引:3
Cyclic AMP was not detected (less than 5 X 10(-9) M intracellular concentration) at any stage of growth or sporulation of two strains of Clostridium perfringens grown with or without methylxanthines. Only Bacillus and Lactobacillus, genera belonging to the same phylogenetic cluster, have previously exhibited undetectable levels of cyclic AMP. 相似文献
954.
P. H. Baylis 《Cell biochemistry and function》1988,6(3):223-223
955.
P Dejours J Armand H Beekenkamp 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1992,315(4):145-150
The pH, the osmolality and the urea and ammonia concentrations in blood, as well as the net urea and ammonia excretions, were studied in the amphibian Xenopus laevis exposed for several weeks to increased osmotic pressure (OP) of the ambient water, as a result of the addition of either NaCl or mannitol to the water. The pH and the ammonia concentration of the blood were independent of the variations of the ambient osmolarity. On the contrary, the blood osmolality and its urea concentration increased markedly when the ambient OP was augmented. The increase of ambient OP by NaCl addition to the medium augmented the urea net excretion and slightly decreased the ammonia excretion. When the increase of ambient OP resulted from the addition of mannitol in the water, excretions of urea and ammonia became negligible. 相似文献
956.
Oxidation of thymine with O2 was promoted by copper(I) ion generated from reaction of L-ascorbic acid (AA) with copper (II) ion. The main oxidation products were thymine glycol (TG) and N-formyl-N'-pyruvylurea (FPU). At higher concentration of O2, formation of FPU was favored, while TG was dominant at higher Cu(II) ion and lower O2 concentrations. Reaction mechanism involving hydroxy thyminyl radical was proposed. 相似文献
957.
Phenotypic data on 203 Gram-negative non-fermentative bacteria of the Flavobacterium-Cytophaga group isolated from milk and butter were analyzed by numerical taxonomic techniques. Twenty reference strains including species of Flavobacterium, Cytophaga and strains of Pseudomonas paucimobilis were included in the study. Using the matching coefficient of Sokal & Michener with antibiotic susceptibility data included, 139 isolates were recovered in nine clusters. Six of these clusters were linked at or above the 85% S level while three were linked at or above the 79% S level. The largest cluster, representing 46.3% of the isolates, could be equated with Flavobacterium sp. Group IIb. Other clusters could be equated with Flavobacterium sp. L 16/1 (22.7% of isolates), F. balustinum (10.8% of isolates), F. breve (4.4%), F. multivorum (3.5%) and Cytophaga johnsonae (1.5%). The cluster resembling Flavobacterium sp. L 16/1 and a smaller unclassified cluster, were exceptional in being susceptible to the antibiotics cephalothin and penicillin G. 相似文献
958.
P S Gromov A M Shandala L I Kovalev S S Shishkin 《Biulleten' eksperimental'no? biologii i meditsiny》1986,102(7):28-30
Fractionation of human erythrocyte membrane proteins was performed using a modification of two-dimensional gel electrophoresis described by P. O'Farrel with isoelectric point plotted against molecular mass. All major erythrocyte proteins, including high molecular weight proteins, such as spectrin and band 3 protein, identified by one-dimensional sodium dodecyl sulfate gel electrophoresis, were visualized by silver staining of two-dimensional gels. All in all about 50 polypeptides were distinguished on two-dimensional electrophoretic patterns. Preliminary protein map was developed. 相似文献
959.
Detection of genetic variants affecting cattle behaviour and their impact on milk production: a genome‐wide association study 下载免费PDF全文
Juliane Friedrich Bodo Brand Siriluck Ponsuksili Katharina L. Graunke Jan Langbein Jacqueline Knaust Christa Kühn Manfred Schwerin 《Animal genetics》2016,47(1):12-18
Behaviour traits of cattle have been reported to affect important production traits, such as meat quality and milk performance as well as reproduction and health. Genetic predisposition is, together with environmental stimuli, undoubtedly involved in the development of behaviour phenotypes. Underlying molecular mechanisms affecting behaviour in general and behaviour and productions traits in particular still have to be studied in detail. Therefore, we performed a genome‐wide association study in an F2 Charolais × German Holstein cross‐breed population to identify genetic variants that affect behaviour‐related traits assessed in an open‐field and novel‐object test and analysed their putative impact on milk performance. Of 37 201 tested single nucleotide polymorphism (SNPs), four showed a genome‐wide and 37 a chromosome‐wide significant association with behaviour traits assessed in both tests. Nine of the SNPs that were associated with behaviour traits likewise showed a nominal significant association with milk performance traits. On chromosomes 14 and 29, six SNPs were identified to be associated with exploratory behaviour and inactivity during the novel‐object test as well as with milk yield traits. Least squares means for behaviour and milk performance traits for these SNPs revealed that genotypes associated with higher inactivity and less exploratory behaviour promote higher milk yields. Whether these results are due to molecular mechanisms simultaneously affecting behaviour and milk performance or due to a behaviour predisposition, which causes indirect effects on milk performance by influencing individual reactivity, needs further investigation. 相似文献
960.
Summary Mutants of S. marcescens HY have been isolated which produce between five and one hundred times more exocellular nuclease than does the parental strain. These nuclease-superactive (nuc
su) mutants are highly pleiotropic: they produce more exocellular marcescin A and lipase than the wild-type and their ability to inactivate penicillin G is increased. Furthermore, all nuclease-superactive mutants if lysogenic for the heteroimmune phages Kappa and/or y show spontaneous induction rates for both prophages 10 to 200 fold greater than the corresponding wild-type. Nuc
su mutants of independent origin synthesize nuclease and marcescin A in approximately proportional amounts although the corresponding structural genes do not seem to be part of a single operon because some bacteriocin-superactive mutants were isolated which showed an increase of the synthesis of marcescin A only. Nuclease-defective (nuc) mutants are all of the non-pleiotropic type. Three hypotheses to explain the effects of the nuc
su mutation at the molecular level are discussed and some evidence in support of one of these hypotheses (gene-dosage effect) is presented in an accompanying paper (Timmis and Winkler, 1973). 相似文献