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2.
Indu S. Ambudkar Timothy Lockwich Yukiharu Hiramatsu Bruce J. Baum 《Molecular and cellular biochemistry》1992,114(1-2):73-77
Conclusions While it is generally accepted that Ca2+ plays an important regulatory role in the physiology of a number of non-excitable cells, the mechanisms which regulate intracellular [Ca2+ are far from well established. Ca2+ transporting mechanisms which distribute Ca2+ intracellularly as well as those which allow influx of extracellular Ca2+ are involved in mediating intracellular Ca2+ homestasis. In this paper we have described recent studies on the regulation of the Ca2+ influx system in the data, it appears that the process of Ca2+ entry is extremely complex and may involve several levels of regulation. Understanding the molecular basis of these regulatory mechanisms presents a challeging problem for future studies. 相似文献
3.
Valerie J. Horn Paul A. Sheehy Miriam B. Goodman Indu S. Ambudkar 《Molecular and cellular biochemistry》1991,101(1):43-49
Intracellular Ca2+ mobilization events were assessed in mouse L cells, which contain native prostaglandin E1 receptors and transfected human 2 adrenergic receptors. Both Fura2 (single cell measurements) and Quin 2, (cuvette assays) were used to determine [Ca2+]i levels. Our results demonstrate that in the transfected cells there is a dose-dependent increase in [Ca2+]i in response to isoproterenol (0.1 nM–100 nM), which is inhibited by the -adrenergic antagonist, propranolol, and is a result of intracellular Ca2+ release. [Ca2+]1 in these cells was also increased by prostaglandin E1, 8 bromo cyclic AMP, and aluminum fluoride. Both 8 bromo cAMP and isoproterenol induced a rapid increase in the levels of IP1, IP2, and IP3. The data presented demonstrate that the elevation of intracellular cyclic AMP induces an increase in IP3 production which leads to an elevation in [Ca2+];. We propose that this cyclic AMP dependent activation of the IP3 generating system occurs at a post-receptor site.Abbreviations cAMP
Adenosine Cyclic 3-5-Monophosphate
- [Ca2+]i
intracellular [Ca2+]i
- 8 Br cAMP
8 Bromo Adenosine Cyclic 3-5-Monophosphate
- DAG
Diacylglycerol
- EGTA]
[Ethylene Bis (oxyethylenenitrilo)] Tetracetic acid
- BSA
Bovine Serum Albumin
- HBSS-H
Hanks' Balanced Salt Solution buffered with HEPES to pH 7.4
- HEPES
4-(2-Hydroxyethyl)-1-piperazineethanesulfonic acid
- PIP2
Phosphatidylinositol 4,5-bisphosphate
- IP2
Inositol 4 Phosphate
- IP2
Inositol 4,5 Bisphosphate
- IP3
Inositol Trisphosphate
- PGE1
Prostaglandin E1
- PBS
Phosphate Buffered Saline Solution 相似文献
4.
Early iron deficiency in rat does not affect the weight or the protein, DNA, and RNA content but results in a slight reduction in gamma-aminobutyric acid (GABA) (13%, p less than 0.01) and glutamic acid (20%, p less than 0.001) content of the brain. The activities of the two GABA shunt enzymes, glutamate dehydrogenase and GABA-transaminase, and of the NAD+-linked isocitrate dehydrogenase (ICDH) were inhibited whereas the glutamic acid decarboxylase, mitochondrial NADP+-linked ICDH, and succinic dehydrogenase activities remained unaltered in brain. On rehabilitation with the iron-supplemented diet for 1 week, these decreased enzyme activities in brain attained the corresponding control values. However, the hepatic nonheme iron content increased to about 80% of the control, after rehabilitation for 2 weeks. A prolonged iron deficiency resulting in decreased levels of glutamate and GABA may lead to endocrinological, neurological, and behavioral alterations. 相似文献
5.
From the petrol extract of Piper clusii five lignans were isolated. One of the lignans (?)-clusin is assigned the structure (?)-2-furanol-4(1,3-benzodioxol-5-ylmethyl) tetrahydro-3(3,4,5-trimethoxyphenyl) methyl. This is the first report of this compound from a natural source. Asaronaldehyde and sitosterol were also present. 相似文献
6.
Circular dichroism and ordered structure of bisnucleoside oligophosphates and their Zn2+ and Mg2+ complexes 总被引:4,自引:0,他引:4
Circular dichroism, absorbance, hypochromicity, and the formation of Mg2+ and Zn2+ complexes have been measured for a series of bisnucleoside oligophosphates that contain adenosine, guanosine, and mixed guanosine/adenosine, guanosine/cytidine, and guanosine/uridine, as well as 7-methylguanosine and ribose-methylated purine nucleosides. All of the metal complex ions have stacking interactions at 2 degrees C, 10 mM tris(hydroxymethyl)aminomethane hydrochloride, pH 8.0. There is a measurable degree of base stacking for all unsubstituted purine nucleotides that differs, however, from that of bases in nucleic acids. The degree of base stacking varies with the length of oligophosphate chains and the state of methylation. The effect of 7-methylation of guanosine is interpreted as causing a switch of nucleic acid base stacking from an atypical to a typical mode, which could be important for cap function in mRNA. The Mg2+ and Zn2+ complexes give rise to characteristic circular dichroism. In all instances excepting 7-methylated bisguanosine oligophosphates, the active secondary structures are disrupted, and in this regard, Zn2+ is more effective than Mg2+. At least two sets of binding sites are involved. A single metal ion is bound tightly. Stability, in terms of equilibrium constants, increases by more than 1000-fold as a function of chain length varying from two to six phosphates. The consequences of methylation are only minor. Electrostatic attraction between metal ions and phosphates is the most likely mechanism of these phenomena as judged by the effect of high ionic strength. 相似文献
7.
8.
In vitro matured and fertilized buffalo oocytes were co-cultured with buffalo oviductal epithelial cells (BOEC) in CRlaa medium. Cleaved embryos were separated according to the time of completion of first cleavage (i.e., before 30 h and after 30 h post insemination) and cultured for 5 to 10 d and allowed to develop to the blastocyst stage. Zygotes cleaving before 30 h were termed fast-cleaving while those cleaving after 30 h were termed slow-cleaving. The results indicated that fast-cleaving embryos are more likely to develop into blastocysts (25%) than slow-cleaving embryos (7.8%). The quality and viability of fast-cleaving and fast-developing blastocysts was found to be better than that of slow-cleaving, slow-developing blastocysts as judged by cell numbers (67.7 +/- 3.7 vs 35.2 +/- 2.1). However, the mitotic index was not different between the 2 groups. The sex of fast-developing and slow-developing blastocysts was determined via the polymerase chain reaction (PCR) to correlate the rate of embryonic development with the sex ratio of the embryos. Embryos produced by Bull 293 and Bull M-82, irrespective of their being fast or slow-developing, gave rise to more females and males, respectively. From these results, we suggest that there may be a sire effect on sex ratio of in vitro produced buffalo embryos. 相似文献
9.
10.
Yukiharu Hiramatsu Indu S. Ambudkar Bruce J. Baum 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》1991,1092(3):391-396
β-Adrenergic receptor stimulation of adenylyl cyclase involves the activation of a GTP-binding regulatory protein (G-protein, termed here Gs). Inactivation of this G-protein is associated with the hydrolysis of bound GTP by an intrinsic high affinity GTPase activity. In the present study, we have characterized the GTPase activity in a Gs-enriched rat parotid gland membrane fraction. Two GTPase activities were resolved; a high affinity GTPase activity displaying Michaelis-Menten kinetics with increasing concentrations of GTP, and a low affinity GTPase activity which increased linearly with GTP concentrations up to 10 mM. The β-adrenergic agonist isoproterenol (10 μM) increased the Vmax of the high affinity GTPase component approx. 50% from 90 to 140 pmol/mg protein per min, but did not change its Km value (≈ 450 nM). Isoproterenol also stimulated adenylyl cyclase activity in parotid membranes both in the absence or presence of GTP. In the presence of a non-hydrolyzable GTP analogue, guanosine 5′-(3-O-thio)triphosphate (GTPγS), isoproterenol increased cAMP formation to the same extent as that observed with AlF4?. Cholera toxin treatment of parotid membranes led to the ADP-ribosylation of two proteins (≈ 45 and 51 kDa). Cholera toxin also specifically decreased the high affinity GTPase activity in membranes and increased cAMP formation induced by GTP in the absence or the presence of isoproterenol. These data demonstrate that the high affinity GTPase characterized here is the ‘turn-off’ step for the adenylyl cyclase activation seen following β-adrenergic stimulation of rat parotid glands. 相似文献