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21.
The influence of surfactant micelles on the acid-base dissociation of the charged tertiary amino group of the local anesthetic, tetracaine, has been investigated. From measurements of tetracaine fluorescence as a function of bulk pH, apparent values of 6.88, 7.58 and 9.92 were found in the presence of cationic, neutral and anionic micelles, respectively, in 10 mM NaCl. These values are considerably displaced with respect to the in aqueous solution which is 8.26. Such large shifts can be attributed to the effect of the surface polarity and electrical potential on the dissociation behavior of the anesthetic bound to micelles. It can be expected that the acid-base dissociation of a local anesthetic adsorbed to nerve fibers will also be affected by the properties of the membrane surface. Thus, it is suggested that the influence of the interfacial region on the of surface-bound molecules should not be disregarded when estimating the proportion of charged and uncharged forms of local anesthetics interacting with axonal membranes. 相似文献
22.
Abstract: Membranes of the secretory vesicles from bovine adrenal medulla were investigated for the presence of the endogenous protein phosphorylation activity. Seven phosphoprotein bands in the molecular weight range of 250,000 to 30,000 were observed by means of the sodium dodecyl sulphate electrophoresis and autoradiography. On the basis of the criteria of molecular weight, selective stimulation of the phosphorylation by cyclic AMP (as compared with cyclic GMP) and immunoprecipitation by specific antibodies, band 5 (molecular weight 60,300) was found to represent the phosphorylated form of the secretory vesicle-bound tyrosine hydroxylase. The electrophoretic mobility, the stimulatory and inhibitory effects of cyclic AMP in presence of Mg2+ and Zn,2+ respectively, and immunoreactivity toward antibodies showed band 6 to contain two forms of the regulatory subunits of the type II cyclic AMP-dependent protein kinase, distinguishable by their molecular weights (56,000 and 52,000, respectively). Phosphorylation of band 7 (molecular weight 29,800) was stimulated about 2 to 3 times by Ca2+ and calmodulin in the concentration range of both agents believed to occur in the secretory tissues under physiological conditions. 相似文献
23.
Piero Cammarano Filomena Mazzei Paola Londei Angela Teichner Mario de Rosa Agata Gambacorta 《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1983,740(3):300-312
Ribosomal subunits of Caldariella acidophila (max.growth temp., 90°C) have been compared to subunits of Bacillus acidocaldarius (max. growth temp., 70°C) and Escherichia coli (max. growth temp., 47°C) with respect to (a) bihelical content of rRNA; (b) G·C content of bihelical domains and (c) tightness of rRNA-protein interactions. The principal results are as follows. 1. Subunits of C. acidophila ribosomes (Tm = 90–93°C) exhibit considerable thermal tolerance over their B. acidocaldarius (Tm = 77°C) and E. coli counterparts (Tm = 72°C). 2. Based on the ‘melting’ hyperchromicities of the intact ribosomal subunits a 51–55% fraction of the nucleotides appears to participate in hydrogen-bonded base pairing regardless of ribosome source, whereas a larger fraction, 67–70%, appears to be involved in hydrogen bonding in the naked rRNA species. 3. The G·C content of bihelical domains of both free and ribosome-bound rRNA increases with increasing thermophily; based on hyperchromicity dispersion spectra of intact subunits and free rRNA, the bihelical parts of C. acidophila rRNA are estimated to contain 63–64% G·C, compared to 58.5% G·C for B. acidocaldarius and 55% G·C for E. coli. 4. The increment in ribosome Tm values with increasing thermophily is greater than the increase in Tm for the free rRNA, indicating that within ribosomes bihelical domains of the thermophile rRNA species are stabilized more efficiently than their mesophile counterparts by proteins or/ and other component(s). 5. The efficiency of the rRNA-protein interactions in the mesophile and thermophile ribosomes has been probed by comparing the releases, with LiCl-urea, of the rRNA species from the corresponding ribosomal subunits stuck to a Celite column through their protein moiety; it has been established that the release of C. acidophila rRNA from the Celite-bound ribosomes occurs at salt-urea concentrations about 4-fold higher than those required to release rRNA from Celite-bound E. coli ribosomes. 6. Compared to E. coli, the C. acidophila 50 and 30 S ribosomal subunits are considerably less susceptible to treatment designed to promote ribosome unfolding through depletion of magnesium ions. 相似文献
24.
F F Kadlubar K C Morton D M Ziegler 《Biochemical and biophysical research communications》1973,54(4):1255-1261
Organic hydroperoxides are capable of supporting the C-oxidation of several different amines in the presence of hepatic microsomes. Evidence is presented that indicates that microsomal cytochrome P-450 acts as the catalyst. Removal of the NADPH-cytochrome oxidoreductase or essential phospholipid from microsomes does not significantly affect the peroxidase activity. Of the amine substrates C-oxidized by organic hydroperoxides in the presence of microsomes, only aminopyrine and dimethylaniline are rapidly oxidized by hydroperoxides in the presence of catalase. The catalase-mediated reaction can also be distinguished from the microsomal-catalyzed reaction by the use of differential inhibitors. 相似文献
25.
Developmental and Regional Expression of NMDA Receptor Subtypes Containing the NR2D Subunit in Rat Brain 总被引:7,自引:3,他引:4
Abstract: The regional and developmental expression of NMDA receptors containing the NR2D subunit was analyzed on the level of the subunit mRNA and protein in rat brain. RNase protection experiments indicated that among two proposed splice variants of the NR2D subunit, only the NR2D-2 subunit is expressed. The regional distribution of the NR2D subunit protein was visualized with a newly developed NR2D-2 subunit-specific antiserum on brain sections using the histoblot technique. In adult brain, NR2D immunoreactivity was mainly restricted to diencephalic, mesencephalic, and brainstem structures. During postnatal development, the NR2D subunit was detected transiently in certain regions, such as the ventro-basal complex of the thalamus, hippocampus, inferior colliculus, and brainstem reticular formation, suggesting that NR2D subunit-containing receptors play a role in these brain areas only during development. The level of NR2D subunit mRNA and protein decreased during late postnatal development. However, significant levels of NR2D subunit mRNA and protein were present in adulthood, in particular, in the globus pallidus, thalamus, subthalamic nuclei, and superior colliculus. These results indicate a functional relevance for NMDA receptors containing the NR2D subunit in the developing and adult brain, although its expression in the adult brain is less prominent and restricted to a few brain areas. 相似文献
26.
Keiko Tadano-Aritomi Harumi Kubo Philip Ireland Takeshi Kasama Shizuo Handa Ineo Ishizuka 《Glycoconjugate journal》1996,13(2):285-293
A novel mono-sulfated glycosphingolipid based on the gangliotriaose core structure was isolated from rat kidney. The isolation procedure involved extraction of lipids with chloroform/methanol, mild alkaline methanolysis, column chromatographies with anion exchangers and silica beads. The structure was characterized by compositional analysis, FTIR spectroscopy, methylation analysis,1H-NMR spectroscopy and negative-ion liquid secondary ion mass spectrometry (LSIMS) using the intact glycolipid and its desulfation product. The two dimensional chemical shift correlated spectroscopy provided information on the sugar sequence as well as anomeric configurations, and indicated the presence of a 3-O-sulfatedN-acetylgalactosamine within the molecule. Negative-ion LSIMS with high- and low-energy collision-induced dissociation defined the sugar sequence and ceramide composition, confirming the presence of a sulfatedN-acetylgalactosamine at the non-reducing terminus. From these results, the complete structure was proposed to be HSO3-3GalNAc1-4Gal1-4Glc1-1Cer (Gg3Cer III3-sulfate, SM2b).
Abbreviations: Abbreviations for sulfated glycolipids [17] follow the modifications of the nomenclature system of Svennerholm for gangliosides [37], and the designation of the other glycosphingolipids follows the IUPAC-IUB recommendations [38]. Cer, ceramide; LacCer, lactosylceramide, Gal1-4Glc1-1Cer; Gg3Cer, gangliotriaosylceramide, GalNAc1-4Gal1-4Glc1-1Cer; Gg4Cer, gangliotetraosylceramide, Gal1-3GalNAc1-4Gal1-4Glc1-1Cer; iGb4Cer, isoglobotetraosylceramide, GalNAc1-3Gal1-3Gal1-4Glc1-1Cer; Gb4Cer, globotetraosylceramide, GalNAc1-3Gal1-4Gal1-4Glc1-1Cer; SM4s, galactosylceramide sulfate, GalCer I3-sulfate; SM3, lactosylceramide sulfate, LacCer II3-sulfate; SM2a, Gg3Cer II3-sulfate; SM2b, Gg3Cer III3-sulfate; SB2, Gg3Cer II3,III3-bis-sulfate; SM1a, Gg4Cer II3-sulfate; SM1b, Gg4Cer IV3-sulfate; SB1a, Gg4Cer II3,IV3-bissulfate; GLC, gas-liquid chromatography; GC-MS, gas chromatography-mass spectrometry; DQF, double quantum filtered; COSY, chemical-shift-correlated spectroscopy; LSIMS, liquid secondary ion mass spectrometry; CID, collision-induced dissociation; MS/MS, tandem mass spectrometry. 相似文献
27.
Abstract: We have studied the regional distribution and characteristics of polyamine-sensitive [3H]ifenprodil binding sites by quantitative autoradiography in the rat brain. In forebrain areas ifenprodil displaced [3H]ifenprodil (40 nM) in a biphasic manner with IC50 values ranging from 42 to 352 nM and 401 to 974 µM. In hindbrain regions, including the cerebellum, ifenprodil displacement curves were monophasic with IC50 values in the high micromolar range. Wiping studies using forebrain slices (containing both high- and low-affinity sites) or cerebellar slices (containing only the low-affinity site) showed that high- and low-affinity ifenprodil sites are sensitive to spermine and spermidine, to the aminoglycoside antibiotics neomycin, gentamicin, and kanamycin, and to zinc. Two calmodulin antagonists, W7 and calmidazolium, also displaced [3H]ifenprodil from both sites. Other calmodulin antagonists, including trifluoperazine, prenylamine, and chlorpromazine, selectively displaced [3H]ifenprodil from its low-affinity site in hindbrain and forebrain regions. High-affinity [3H]ifenprodil sites, defined either by ifenprodil displacement curves or by [3H]ifenprodil binding in the presence of 1 mM trifluoperazine, were concentrated in the cortex, hippocampus, striatum, and thalamus with little or no labeling of hindbrain or cerebellar regions. This distribution matches that of NMDAR2B mRNA, supporting data showing that ifenprodil has a preferential action at NMDA receptors containing this subunit. Low-affinity [3H]ifenprodil sites have a more ubiquitous distribution but are especially concentrated in the molecular layer of the cerebellum. [3H]Ifenprodil was found to bind to calmodulin-agarose with very low affinity (IC50 of ifenprodil = 516 µM). This binding was displaced by calmodulin antagonists and by polyamines, with a potency that matched their displacement of [3H]ifenprodil from its low-affinity site in brain sections. However, the localization of the low-affinity [3H]ifenprodil site does not strictly correspond to that of calmodulin, and its identity remains to be further characterized. The restricted localization of high-affinity [3H]ifenprodil binding sites to regions rich in NMDAR2B subunit mRNA may explain the atypical nature of this NMDA antagonist. 相似文献
28.
In extracts from the primary leaf blade of sugar beet (Beta vulgaris L.) we separated a chloroplastic isoform (GS 2) of glutamine synthetase (GS, EC 6.3.1.2) and one or two (depending on leaf age) cytosolic isoforms (GS 1a and GS 1b). The latter were prominent in the early (GS 1a) and late stages of leaf ontogeny (GS 1a and GS 1b), whereas during leaf maturation GS 2 was the predominantly active GS isoform. The GS 1 isoforms were active exclusively in the octameric state although tetrameric GS 1 protein was detected immunologically. Their activity stayed at a relatively constant level during leaf ontogeny; an increase was observed only in the senescent leaf. The activity of GS 2, however, changed drastically during primary leaf ontogeny and was modulated by changes in the oligomeric state of the active enzyme. In the early and late stages of leaf ontogeny when GS 2 activity was low (lower than that of the GS 1 isoforms), GS 2 was active only in the octameric state. In the maturing leaf, when GS 2 activity had reached its maximum level (much higher than that of the GS 1 isoforms), 80 of total GS 2 activity was due the activity of the tetrameric form of the enzyme and 20 was due to octameric GS 2. Tetrameric GS 2 was a hetero-tetramer and thus not the unspecific dissociation product of homo-octameric GS 2. In addition, GS 2 activity was modulated by an activation/inactivation of the tetrameric GS 2 protein. Due to an activation of the GS 2 tetramer, the activity of tetrameric GS 2 increased during leaf maturation from zero level 23-fold compared with that of GS 1a and 18-fold compared with that of GS 1b. Possible activators of tetrameric GS 2 are thiol-reactive substances. During leaf senescence, GS 2 activity decreased to zero; this decrease was due to an inactivation of the tetrameric GS 2 protein probably caused by oxidation.Abbreviations FLL
final lamina length
- FPLC
fast protein liquid chromatography
- GS
glutamine synthetase
- GHA
-glutamyl hydroxamate
- Rubisco
ribulose-1,5-bisphosphate carboxylase/oxygenase
Dr. Roger Wallsgrove's (Rothamsted Experimental Station, Harpenden, UK) generous gift of GS antiserum is greatly appreciated. 相似文献
29.
Egbert J. Boekema Arjen F. Boonstra Jan P. Dekker Matthias Rögner 《Journal of bioenergetics and biomembranes》1994,26(1):17-29
Electron microscopy (EM) in combination with image analysis is a powerful technique to study protein structure at low- and high resolution. Since electron micrographs of biological objects are very noisy, substantial improvement of image quality can be obtained by averaging individual projections. Crystallographic and noncrystallographic averaging methods are available and have been applied to study projections of the large protein complexes embedded in photosynthetic membranes from cyanobacteria and higher plants. Results of EM on monomeric and trimeric Photosystem I complexes, on monomeric and dimeric Photosystem II complexes, and on the monomeric cytochromeb6/f complex are discussed. 相似文献
30.