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61.
Neuza Domingues André R. A. Marques Rita Diogo Almeida Calado Inês S. Ferreira Cristiano Ramos José Ramalho Maria I. L. Soares Telmo Pereira Luís Oliveira José R. Vicente Louise H. Wong Inês C. M. Simões Teresa M. V. D. Pinho e Melo Andrew Peden Cláudia Guimas Almeida Clare E. Futter Rosa Puertollano Winchil L. C. Vaz Otília V. Vieira 《Traffic (Copenhagen, Denmark)》2023,24(7):284-307
62.
63.
Abstract: The α subunit of Gz (αz) harbors two N-terminal serine residues (at positions 16 and 27) that serve as protein kinase C-mediated phosphorylation sites. The cognate residues in the α subunit of Gt1 provide binding surfaces for the β1 subunit. We used three serine-to-alanine mutants of αz to investigate the functional importance of the two N-terminal serine residues. Wild-type or mutant αz was transiently coexpressed with different receptors and adenylyl cyclase isozymes in human embryonic kidney 293 cells, and agonist-dependent regulation of cyclic AMP accumulation was examined in a setting where all endogenous α subunits of Gi were inactivated by pertussis toxin. Replacement of one or both serine residues by alanine did not alter the ability of αz to interact with δ-opioid, dopamine D2, or adenosine A1 receptors. Its capacity to inhibit endogenous and type VI adenylyl cyclases was also unaffected. Functional release of βγ subunits from the mutant αz subunits was not impaired because they transduced βγ-mediated stimulation of type II adenylyl cyclase. Constitutively active mutants of all four αz subunits were constructed by the introduction of a Q205L mutation. The activated mutants showed differential abilities to inhibit human choriogonadotropin-mediated cyclic AMP accumulation in luteinizing hormone receptor-transfected cells. Loss of both serine residues, but not either one alone, impaired the receptor-independent inhibition of adenylyl cyclase by the GTPase-deficient mutant. Thus, replacement of the amino-terminal serine residues of αz has no apparent effect on receptor-mediated responses, but these serine residues may be essential for ensuring transition of αz into the active conformation. 相似文献
64.
Ronald I. Clyman Louise Wong Michael A. Heymann Abraham M. Rudolph 《Prostaglandins & other lipid mediators》1978,15(2):325-331
The relative potencies of the prostaglandins A1, A2, E1, E2, F2α and their 15-keto-, 15-keto-13,14-dihydro-, and 13,14-dihydro-metabolites were investigated on isolated lamb ductus arteriosus preparations contracted by exposure to elevated PO2. All the prostaglandins (except PGF2α and its 15-keto-metabolites) relaxed the tissue. However, only PGE1, E2, and their 13,14-dihydro-metabolites, were effective at concentrations below 10−8 M. Therefore, events that alter metabolism of circulating PGs in the perinatal period may have significant effects on the relative patency or closure of the ductus arteriosus. 相似文献
65.
Resting cells of Bacteroides melaninogenicus fermented L-[14C]aspartate as a single substrate. The 14C-labeled products included succinate, acetate, CO2, oxaloacetate, formate, malate, glycine, alanine, and fumarate in the relative percentages 68, 15, 9.9, 2.7, 1.8, 1.0, 0.7, 0.5, and 0.06, respectively, based on the total counts per minute of the L-[14C]aspartate fermented. Ammonia was produced in high amounts, indicating that 96% of the L-aspartate fermented was deaminated. These data suggest that L-aspartate is mainly being reduced through a number of intermediate reactions involving enzymes of the tricarboxylic acid cycle to succinate. L-[14C]asparagine was also fermented by resting cells of B. melaninogenicus to form L-aspartate, which was subsequently, but less actively, fermented. 相似文献
66.
Maternal undernutrition may result in a greater deprivation of the fetus than has previously been believed. The infant not only may be "light for dates" but also has an increased risk of perinatal disability or death secondary to gross neurologic and developmental abnormalities. This article reviews current knowledge of the energy, protein, iron, vitamin, sodium and calcium requirements in pregnancy, with special reference to the management of the underweight and overweight pregnant women. 相似文献
67.
Microsomal fractions of cells isolated from chick epiphyseal cartilage catalyzed the synthesis of prostaglandins from radiolabeled delta8,11,14-eicosatrienoic and from arachidonic acids. In addition, the microsomal supernatants contained both 15-hydroxyprostaglandin dehydrogenase and prostaglandin 15-keto delta13,14-reductase activities. Two major classes of prostaglandins (E and F) were synthesized; however, a major product which chromatographically behaves as PGA was also isolated. Synthetase activities were analyzed for pH optima and response to known stimulators and inhibitors of prostaglandin systhesis. The different activators had varying stimulatory effects on prostaglandin synthesis; the anti-inflammatory drugs were all strongly inhibitory. Synthetase activity in the growth plate was highest in the zone of hypertrophy, declining substantially in the more heavily calcified regions. Degradative enzyme activities were highest in the zone of maturation and significantly lower in the adjacent hypertrophic zone. The net effect of these opposing activities would be to elevate prostaglandin levels at the zone of hypertrophy, a finding which suggests that prostaglandins may play a role in the modulation of epiphyseal cartilage metabolism. 相似文献
68.
Resting cells of Bacteroides melaninogenicus fermented L-[14C]aspartate as a single substrate. The 14C-labeled products included succinate, acetate, CO2, oxaloacetate, formate, malate, glycine, alanine, and fumarate in the relative percentages 68, 15, 9.9, 2.7, 1.8, 1.0, 0.7, 0.5, and 0.06, respectively, based on the total counts per minute of the L-[14C]aspartate fermented. Ammonia was produced in high amounts, indicating that 96% of the L-aspartate fermented was deaminated. These data suggest that L-aspartate is mainly being reduced through a number of intermediate reactions involving enzymes of the tricarboxylic acid cycle to succinate. L-[14C]asparagine was also fermented by resting cells of B. melaninogenicus to form L-aspartate, which was subsequently, but less actively, fermented. 相似文献
69.
LR5182 inhibited the uptake of dopamine in rat striatal synaptosomes and the uptake of norepinephrine in cortical synaptosomes with inhibitor constants, Ki values, of 3nM and 58nM, respectively. It was only a week inhibitor of serotonin uptake in cortical synaptosomes with a Ki value of 1.7μM. The uptake of dopamine and norepinephrine were significantly lowered within an hour after an intraperitoneal injection of LR5182. Among known inhibitors of dopamine uptake in synaptosomes of rat brain, LR5182 is most effective and selective. The rigid structure of LR5182 (Figure 1) suggested a gauche conformation of dopamine to be favored by the striatal uptake of dopamine. 相似文献
70.
The methyl 4-azidobenzimidate derivative of the naturally occurring ATPase inhibitor protein (IF1) of mitochondria binds to the beta subunits of soluble F1-ATPase upon photoactivation [Klein, G., Satre, M., Dianoux, A.-C., & Vignais, P. V. (1981) Biochemistry 20, 1339--1344]. A number of specific ATPase inhibitors, namely, 4-chloro-7-nitrobenzofurazan (NBF-Cl), efrapeptin, 5'-[p-(fluorosulfonyl)benzoyl]adenosine (FSBA), phenylglyoxal, aurovertin, tridentate ferrous bathophenanthroline, and octylguanidine (referred to hereafter as "artificial" inhibitors), are also considered to bind to the beta subunit, and there is strong evidence that the first three bind at the active site. Since the inhibition by IF1 of complex V ATPase activity can be reversed by incubation of the inhibited complex at pH 8.0, this system was used to investigate whether the inhibitions brought about by IF1 and the artificial inhibitors were independent, mutually interfering, or mutually exclusive. The experiments were carried out in two ways. (a) Complex V was first maximally inhibited by IF1. Then an artificial inhibitor was added and allowed to react. Excess artificial inhibitor was removed by precipitation of the doubly inhibited complex V with ammonium sulfate and resuspension in inhibitor-free buffer at pH 8.0. Incubation at pH 8.0 released the inhibition due to IF1. However, it was found that the factor that controlled reemergence of ATPase activity was the degree of inhibition exerted by the artificial inhibitor. When the artificial inhibitor was removed first (which was done by addition of dithiothreitol when the artificial inhibitor was NBF-Cl), then reemergence of activity depended on incubation at pH 8.0 to reverse the inhibition due to IF1. These results indicated that IF1-inhibited complex V could be independently inhibited by various artificial inhibitors. The artificial inhibitors used in this type of study were NBF-Cl, efrapeptin, aurovertin, FSBA, and phenylglyoxal. (b) Complex V was first treated with the artificial inhibitor (ferrous bathophenanthroline or octylguanidine) and then with IF1. Results showed that prior treatment of complex V with these inhibitors did not interfere with IF1 subsequently exerting maximal and reversible inhibition. The above results have been discussed in view of the recent finding that F1-ATPase contains two functional and interacting hydrolytic sites [Grubmeyer, C., & Penefsky, H.S. (1981) J. Biol. Chem. 256, 3718--3727]. 相似文献