全文获取类型
收费全文 | 1706篇 |
免费 | 114篇 |
国内免费 | 1篇 |
出版年
2023年 | 6篇 |
2022年 | 16篇 |
2021年 | 48篇 |
2020年 | 31篇 |
2019年 | 28篇 |
2018年 | 31篇 |
2017年 | 20篇 |
2016年 | 45篇 |
2015年 | 71篇 |
2014年 | 74篇 |
2013年 | 108篇 |
2012年 | 110篇 |
2011年 | 127篇 |
2010年 | 79篇 |
2009年 | 72篇 |
2008年 | 85篇 |
2007年 | 80篇 |
2006年 | 84篇 |
2005年 | 73篇 |
2004年 | 74篇 |
2003年 | 65篇 |
2002年 | 66篇 |
2001年 | 33篇 |
2000年 | 38篇 |
1999年 | 25篇 |
1998年 | 19篇 |
1997年 | 16篇 |
1996年 | 12篇 |
1995年 | 8篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 19篇 |
1991年 | 21篇 |
1990年 | 18篇 |
1989年 | 22篇 |
1988年 | 16篇 |
1987年 | 19篇 |
1986年 | 20篇 |
1985年 | 15篇 |
1984年 | 17篇 |
1983年 | 7篇 |
1981年 | 6篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1966年 | 5篇 |
排序方式: 共有1821条查询结果,搜索用时 62 毫秒
31.
Joelle E. Romanchik Earl H. Harrison Diane W. Morel 《The Journal of nutritional biochemistry》1997,8(12):681-688
Carotenoids are dietary antioxidants transported with plasma lipoproteins, primarily low-density lipoprotein (LDL). In this study in vitro methods were used to increase the amounts of specific, individual carotenoids in LDL. By addition of carotenoid to isolated LDL or to serum, followed by (re)isolation of the lipoproteins, samples of LDL were enriched 4- to 150-fold with lutein, 2- to 15-fold with lycopene, or 3- to 25-fold with β-carotene. Enrichment with specific carotenoids was achieved without affecting the electrophoretic mobility of the lipoprotein, its cholesterol to protein ratio, or the levels of other cartenoids or -tocopherol. The distributions among lipoproteins of carotenoid added to serum were similar, but not identical, to the distributions of the endogenous carotenoids. In particular, for added lutein, a greater proportion was found in HDL, and for added β-carotene, more was found in very low-density lipoprotein (VLDL). We then studied the effect of enriching LDL with specific carotenoids on its susceptibility to oxidation by copper ions. Lutein, β-cryptoxanthin, lycopene, and β-carotene, the four major plasma carotenoids, and -tocopherol were destroyed before the formation of lipid peroxidation products. The rates of destruction of the individual carotenoids differed; lycopene was destroyed most rapidly and lutein most slowly. Upon oxidation of β-carotene-enriched LDL, the rates of destruction of β-carotene, lycopene, and lutein were slowed and the lag times before the initiation of lipid peroxidation increased from 19 to 65 min. Neither effect was observed in LDL enriched with lutein or lycopene. Thus, β-carotene was unique among the carotenoids studied in having a small, but significant effect on LDL oxidation in vitro. 相似文献
32.
The existence of Na+ -dependent Ca2+ transport was investigated in microsomal fractions from the longitudinal smooth muscle of the guinea-pig ileum and from the rat aorta, and its activity was compared with that of the plasmalemmal ATP-dependent Ca2+ pump previously identified in these preparations. The rate of Ca2+ release from plasmalemmal vesicles previously loaded with Ca2+ through the ATP-dependent Ca2+ pump was transiently faster in the presence of 150 mM-NaCl in the medium than in the presence of 150 mM-KCl or -LiCl or 300 mM-sucrose. Na+-loaded vesicles took up Ca2+ when an outwardly directed Na+ gradient was formed across the membrane. The Ca ionophore A23187 induced a rapid release of 85% of the sequestered Ca2+, whereas only 15% was displaced by La3+. Ca2+ accumulated by the Na+-induced Ca2+ transport was released by the addition of NaCl, but not KCl, to the medium. Ca2+ uptake in Na+-loaded vesicles was inhibited in the presence of increasing NaCl concentration in the medium. Half-maximum inhibition was observed with 28 mM-NaCl. Data fitted the Hill equation, with a Hill coefficient (h) of 1.9. Na+-induced Ca2+ uptake was a saturable function of Ca2+ concentration in the medium. Half-maximum activity was obtained with 18 microM-Ca2+ in intestinal-smooth-muscle microsomal fraction and with 50 microM-Ca2+ in aortic microsomal fraction. The results suggest that in these membrane preparations a transmembrane movement of Ca2+ can be driven by a Na+ gradient. However, the Na+-induced Ca2+ transport had a lower capacity, a lower affinity and a slower rate than the ATP-dependent Ca2+ pump. 相似文献
33.
M P Deane R H Mangia N M Pereira H Momen A M Gon?alves C M Morel 《Memórias do Instituto Oswaldo Cruz》1984,79(4):495-497
From an initial double infection in mice, established by simultaneous and equivalent inocula of bloodstream forms of strains Y and F of Trypanosoma cruzi, two lines were derived by subinoculations: one (W) passaged every week, the other (M) every month. Through biological and biochemical methods only the Y strain was identified at the end of the 10th and 16th passages of line W and only the F strain at the 2nd and 4th passages of line M. The results illustrate strain selection through laboratory manipulation of initially mixed populations of T. cruzi. 相似文献
34.
Pure cholinergic synaptosomes prepared from the electric organ of Torpedo are able to take adenosine up efficiently and convert it to ATP. The apparent Km of the adenosine uptake is 2.4 μM and the Vm: 518 pmol/30′/mg prot. The uptake system exhibits a high specificity towards adenosine, as shown by the lack of competition with analogues. Tubercidin blocks the uptake competitively and dipyridamole is a very potent non competitive inhibitor (Ki= 4 × 10-8 M). Considering that during nerve activity ATP is released extracellularly and can modulate transmitter release, the physiological significance of adenosine uptake is discussed as a possible mechanism to terminate the ATP action. 相似文献
35.
The superoxide-generating oxidase of phagocytic cells. Physiological, molecular and pathological aspects. 总被引:32,自引:0,他引:32
Professional phagocytes (neutrophils, eosinophils, monocytes and macrophages) possess an enzymatic complex, the NADPH oxidase, which is able to catalyze the one-electron reduction of molecular oxygen to superoxide, O2-. The NADPH oxidase is dormant in non-activated phagocytes. It is suddenly activated upon exposure of phagocytes to the appropriate stimuli and thereby contributes to the microbicidal activity of these cells. Oxidase activation in phagocytes involves the assembly, in the plasma membrane, of membrane-bound and cytosolic components of the oxidase complex, which were diassembled in the resting state. One of the membrane-bound components in resting phagocytes has been identified as a low-potential b-type cytochrome, a heterodimer composed of two subunits of 22-kDa and 91-kDa. The link between NADPH and cytochrome b is probably a flavoprotein whose subcellular localization in resting phagocytes remains to be determined. Genetic defects in the cytochrome b subunits and in the cytosolic factors have been shown to be the molecular basis of chronic granulomatous disease, a group of inherited disorders in the host defense, characterized by severe, recurrent bacterial and fungal infections in which phagocytic cells fail to generate O2- upon stimulation. The present review is focused on recent data concerning the signaling pathway which leads to oxidase activation, including specific receptors, the production of second messengers, the organization of the oxidase complex and the molecular defects responsible for granulomatous disease. 相似文献
36.
L Cohen-Tanugi F Morel M C Pilloud-Dagher J M Seigneurin P Francois M Bost P V Vignais 《European journal of biochemistry》1991,202(2):649-655
Epstein-Barr-virus-transformed human B lymphocytes (EBV B lymphocytes) stimulated by 4 beta-phorbol 12-myristate 13-acetate exhibit an NADPH-dependent oxidase activity capable of generating the superoxide anion O2-, similar to, but less efficient than that of activated neutrophils. A cell-free system of oxidase activation consisting of a membrane fraction and cytosol from EBV B lymphocyte homogenate supplemented with guanosine 5'-[gamma-thio]triphosphate (GTP[S]), arachidonic acid and Mg2+ was found to be competent in the production of O2-, assessed by the superoxide-dismutase-sensitive reduction of cytochrome c in the presence of NADPH. However, cytochrome c reduction was slow and largely insensitive both to superoxide dismutase, and to iodonium biphenyl, a powerful inhibitor of the oxidase activity in neutrophils. A markedly faster reduction of cytochrome c in the presence of NADPH was obtained with a heterologous system consisting of cytosol from EBV B lymphocytes and bovine neutrophil membranes, GTP[S], arachidonic acid and Mg2+; in this system, reduction of cytochrome c was totally inhibited by superoxide dismutase and iodonium biphenyl. These results show that EBV B lymphocytes contain a substantial amount of cytosolic factors of oxidase activation, and that the limiting factors for O2- production in B lymphocytes are the membrane components of the oxidase complex. The heterologous system of EBV B lymphocyte cytosol and bovine neutrophil membranes provided a rapid and convenient method to diagnose cytosolic defects in autosomal forms of chronic granulomatous disease. In addition, it might be a useful tool to explore the mechanism of action of the cytosolic factors in oxidase activation. 相似文献
37.
Mohammed Sbia Marie-Francoise Diebler Nicolas Morel Maurice Israël 《Journal of neurochemistry》1992,59(4):1273-1279
The mediatophore is a presynaptic membrane protein that has been shown to translocate acetylcholine (ACh) under calcium stimulation when reconstituted into artificial membranes. The mediatophore subunit, a 15-kDa proteolipid, presents a very high sequence homology with the N,N'-dicyclohexylcarbodiimide (DCCD)-binding proteolipid subunit of the vacuolar-type H(+)-ATPase. This prompted us to study the effect of DCCD, a potent blocker of proton translocation, on calcium-dependent ACh release. The present work shows that DCCD has no effect on ACh translocation either from Torpedo synaptosomes or from proteoliposomes reconstituted with purified mediatophore. However, using [14C]DCCD, we were able to demonstrate that the drug does bind to the 15-kDa proteolipid subunit of the mediatophore. These results suggest that although the 15-kDa proteolipid subunits of the mediatophore and the vacuolar H(+)-ATPase may be identical, different domains of these proteins are involved in proton translocation and calcium-dependent ACh release and that the two proteins have a different membrane organization. 相似文献
38.
Maurice Arissian Dominique Perrissin-Fabert André Blouet Jean-Louis Morel Armand Guckert 《Journal of Plant Growth Regulation》1991,10(1-4):1-4
The role of imazaquin in the absorption, translocation, and distribution of chlormequat chloride in CYCOCEL* CL has been studied in winter wheat. Three treatments were applied to the 5th leaf of the main stem at growth stage 5 (Feekes Large scale): (1)14C-chlormequat chloride, (2) CYCOCEL* CL containing14C-chlormequat chloride, and (3) CYCOCEL* CL containing14C-imazaquin. Tracing of the radioactivity was followed in the treated leaf, main stem, tillers, and roots. Results showed that more than 85% of the radioactivity absorbed remained in the treated leaf. Ten days after the application of chlormequat chloride alone, 94.4% of the14C-chlormequat was found in the treated leaf, 2.9% in the main stem, 1.2% in the tillers, and 1.4% in the root system versus 88.2, 8.2, 2.1, and 1.4%, respectively, for the chlormequat chloride plus imazaquin treatment. It was concluded that imazaquin increases the mobility and the pattern of distribution of chlormequat chloride in the plant. 相似文献
39.
40.
The 125I-labeled Mr 80000 form of neurophysin has been purified from bovine neurohypophysi. Tryptic digests of this species were analyzed, prior to or after treatment with carboxypeptidase B, by high-pressure liquid chromatography followed by isoelectric focusing and the fragments compared with those generated by a similar treatment of reference bovine 1-39 adrenocorticotropin. The ACTH peptides 22-39 and 1-8, as well as the 1-7 derivative of the latter were identified by those two independent criteria. This provides chemical evidence supporting the hypothesis [8] that high Mr neurophysin may contain the sequence of ACTH. 相似文献