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31.
W T Garvey T P Huecksteadt F B Lima M J Birnbaum 《Molecular endocrinology (Baltimore, Md.)》1989,3(7):1132-1141
32.
Alkaline extracts of adult opossum red cells were used to determine triphosphates of adenosine, deoxyadenosine and guanosine by anion exchange HPLC. Mean (nm/g Hg) ATP content of erythrocytes was 3713 and that of dATP 1913 (n = 12). Sonicates of red cells deaminated adenosine (ADO) at a rate of 1.55 nm/mg Hg/h and deoxyadenosine (dADO) at 1.82 nm/mg Hg/h. dATP synthesis from provided dADO was one order of magnitude greater in opossum than in human erythrocytes at both low and high dADO and Pi concentrations. 相似文献
33.
Shlomo Nir Nejat Düzgünes Maria C. Pedroso De Lima Dick Hoekstra 《Cell biochemistry and biophysics》1990,17(2):181-201
The fusion of viruses with cells and liposomes is reviewed with focus on the analysis of the final extents and kinetics of
fusion.Influenza virus andSendai virus exhibit 100% of fusion capacity with cells at pH 5 and pH 7.5, respectively. On the other hand, there may be in certain
cases, a limit on the number of virions that can fuse with a single cell, that is significantly below the limit on binding.
It still remains to be resolved whether this limit reflects a limited number of possible fusion sites, or a saturation limit
on the amount of viral glycoproteins that can be incorporated in the cellular membrane, like the case of virus fusion with
pure phospholipid vesicles, in which the fusion products were shown to consist of a single virus and several liposomes. Both
viruses demonstrate incomplete fusion activity towards liposomes of a variety of compositions. In the case ofSendai virus, fusion inactive virions bind essentially irreversibly to liposomes. Yet, preliminary results revealed that such bound,
unfused virions can be released by sucrose gradient centrifugation. The separated unfused virions subsequently fuse when incubated
with a “fresh” batch of liposomes. We conclude, therefore, that the fraction of initially bound unfused virions does not consist
of dective particles, but rather of particles bound to liposomes via “inactive” sites.
Details of the low pH inactivation of fusion capacity ofinfluenza virus towards cells and liposomes are presented. This inactivation is caused by protonation and exposure of the hydrophobic
segment of HA2, and affects primarily the fusion rate constants. Some degree of inactivation also occurs when virions are bound to cellular
membranes. 相似文献
34.
Sheila H. Luijten J. Gerard B. Oostermeijer Nico C. van Leeuwen Hans C. M. den Nijs 《Plant Systematics and Evolution》1996,201(1-4):15-30
In a medium-sized population ofArnica montana, a threatened species in The Netherlands, the breeding system, reproductive success and genetic clonal structure were studied. Pollination experiments suggested thatA. montana is largely self-incompatible. Inbreeding depression was observed for seedling weight but not for fruit weight and germination rate. Although genetic variation is rather low in this population, the data suggest an outcrossing mating system. Analysis of the genotype of all mapped rosettes in a plot of 100 m2 indicated that dense clusters often consist of identical genotypes, suggesting a clonal structure. Open clusters frequently contained several different genotypes. This may be caused by limited fruit dispersal, since seedlings were found mainly within or in the near surroundings of the clusters. 相似文献
35.
Maria Claudia Gonzalez Deniselle Susana L. Gonzalez Gerardo G. Piroli Analia E. Lima Alejandro F. De Nicola 《Cellular and molecular neurobiology》1996,16(1):61-72
Summary 1. Wobbler mice suffer an autosomal recessive mutation producing severe motoneuron degeneration and dense astrogliosis, with
increased levels of glial fibrillary acidic protein (GFAP) in the spinal cord and brain stem. They have been considered animal
models of amyotrophic lateral sclerosis and infantile spinal muscular atrophy.
2. Using Wobbler mice and normal littermates, we investigated the effects of the membrane-active steroid Lazaroid U-74389F
on the number of GFAP-expressing astrocytes and glucocorticoid receptors (GR). Lazaroids are inhibitors of oxygen radical-induced
lipid peroxidation, and proved beneficial in cases of CNS injury and ischemia.
3. Four days after pellet implantation of U-74389F into Wobbler mice, hyperplasia and hypertophy of GFAP-expressing astrocytes
were apparent in the spinal cord ventral and dorsal horn, areas showing already intense astrogliosis in untreated Wobbler
mice. In control mice, U-74389F also produced astrocyte hyperplasia and hypertophy in the dorsal horn and hyperplasia in the
ventral-lateral funiculi of the cord.
4. Givenin vivo U-74389F did not change GR in spinal cord of Wobbler or control mice, in line with the concept that it is active in membranes
but does not bind to GR. Besides, U-74390F did not compete for [3H]dexamethasone binding when addedin vitro.
5. The results suggest that stimulation of proliferation and size of GFAP-expressing astrocytes by U-74389F may be a novel
mechanism of action of this compound. The Wobbler mouse may be a valuable animal model for further pharmacological testing
of glucocorticoid and nonglucocorticoid steroids in neurodegenerative diseases. 相似文献
36.
Sheila Andreatta-Van Leyen Joan R. Hembree Richard L. Eckert 《Journal of cellular physiology》1994,160(2):265-274
Insulin-like growth factors (IGFs) are important regulators of epithelial cell growth. The mitogenic activity of these factors is influenced by the levels of extracellular IGF binding proteins, including insulin-like growth factor binding protein 3 (IGFBP-3). In the present report we study the effects of epidermal growth factor (EGF) and all-trans-retinoic acid (RA) on IGFBP-3 RNA and protein levels in human papillomavirus-immortalized cervical epithelial cells. Treatment of ECE16-1 cells with 3–20 ng/ml EGF causes a marked reduction in IGFBP-3 levels. In contrast, 1 μM RA increases IGFBP-3 mRNA and protein levels in the presence or absence of 20 ng/ml EGF. The response is concentration dependent with a half-maximal increase observed at 1 nM RA. RA is able to reverse the EGF suppression when added simultaneously or 3 days after initiation of EGF treatment. Conversely, when cells are treated with RA, IGFBP-3 levels increase within 24 h and subsequent addition of EGF is without effect. Thus, the RA-dependent increase in IGFBP-3 levels is dominant over the EGF suppression. The increased IGFBP-3 levels are correlated with RA suppression of proliferation. Similar RA effects on IGFBP-3 mRNA levels were observed in other cervical epithelial cell lines (i.e., ECE16-D1, ECE16-D2, and CaSki). These results suggest that RA may act to inhibit cervical cell growth by increasing IGFBP-3 levels and reducing the extracellular concentration of free insulin-like growth factor I (IGFI) and/or, alternatively, IGFBP-3 may inhibit cell growth by direct effects on the cell, independent of IGFI. © 1994 Wiley-Liss, Inc. 相似文献
37.
The binding sites of 8-[3H]hydroxy-2-(di-n-propylamino)tetralin ([3H]DPAT) were characterized in the retina of goldfish in order to evaluate the selectivity of the ligand for serotonin1A (5HT1A) receptors. Specificity of the binding was performed in the presence of serotonergic and dopaminergic agonists and antagonists. Buspirone, spriroxatrine and 5-methoxy-N,N-dimethyltryptamine were potent inhibitors, followed by propranolol, citalopram, imipramine and desipramine. Serotonin was not a potent inhibitor, and its interaction with the binding sites of [3H]DPAT was complex. Nomifensine displayed an important inhibition, however, other dopamine uptake blockers, such as bupropion and GBR-12909, were less potent. Haloperidol was also a good inhibitor, but the D1 receptor agonist, SKF-38393, the D2 receptor antagonist, sulpiride, and dopamine did not inhibit the binding. GppNHp inhibited the binding in the micromolar range. The analysis of saturation experiments by isotopic dilution, using buspirone to determine nonspecific binding, revealed two sites. The number of binding sites defined by buspirone were higher than the ones defined by nomifesine. The specific binding, using buspirone for definition, was reduced by the intraocular injection of 6-hydroxydopamine. This investigation demonstrates that [3H]DPAT labels 5HT1A receptors in goldfish retina, but also interacts with a non-5HT receptor site. These receptors seem to be localized in dopaminergic neurons. 相似文献
38.
39.
Sheila L. Vrana Kent E. Vrana Timothy R. Koves James E. Smith Steven I. Dworkin 《Journal of neurochemistry》1993,61(6):2262-2268
Cocaine is an inhibitor of dopamine and serotonin reuptake by synaptic terminals and has potent reinforcing effects that lead to its abuse. Tyrosine hydroxylase (TH) and tryptophan hydroxylase (TPH) catalyze the rate-limiting steps in dopamine and serotonin biosynthesis, respectively, and are the subject of dynamic regulatory mechanisms that could be sensitive to the actions of cocaine. This study assessed the effects of chronic cocaine on brain TH and TPH activities. Cocaine was administered (0.33 mg/infusion, i.v.) to rats for 7 days every 8 min for 6 h per day. This administration schedule is similar to patterns of self-administration by rats when given ad libitum access to this dose. This chronic, response-independent administration increased TH enzyme activity in the substantia nigra (30%) and ventral tegmental area (43%). Moreover, TH mRNA levels were also increased (45 and 50%, respectively). In contrast to the enzymatic and molecular biological changes in the cell bodies, TH activity was unchanged in the terminal fields (corpus striaturn and nucleus accumbens). Similarly, TPH activity was increased by 50% in the raphe nucleus (serotonergic cell bodies). In summary, the chronic response-independent administration of cocaine produces increases in the expression of TH mRNA and activity in both the cell bodies of motor (nigrostriatal) and reinforcement (mesolimbic) dopamine pathways. These increases are not manifested in the terminal fields of these pathways. 相似文献
40.
Martina Ferraguti Sergio Magallanes Jéssica Jiménez-Peñuela Josué Martínez-de la Puente Luz Garcia-Longoria Jordi Figuerola Jaime Muriel Tamer Albayrak Staffan Bensch Camille Bonneaud Rohan H. Clarke Gábor Á. Czirják Dimitar Dimitrov Kathya Espinoza John G. Ewen Farah Ishtiaq Wendy Flores-Saavedra László Zsolt Garamszegi Olof Hellgren Dita Horakova Kathryn P. Huyvaert Henrik Jensen Asta Križanauskienė Marcos R. Lima Charlene Lujan-Vega Eyðfinn Magnussen Lynn B. Martin Kevin D. Matson Anders Pape Møller Pavel Munclinger Vaidas Palinauskas Péter L. Pap Javier Pérez-Tris Swen C. Renner Robert Ricklefs Sergio Scebba Ravinder N. M. Sehgal Manuel Soler Eszter Szöllősi Gediminas Valkiūnas Helena Westerdahl Pavel Zehtindjiev Alfonso Marzal 《Global Ecology and Biogeography》2023,32(5):809-823