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91.
测定妊娠期妇女羊水中微量元素锌、铜(Zn、Cu)的含量变化,对预测胎儿的发育情况,具有一定的参考价值。本文介绍一种利用紫外辐射消化技术,对羊水进行预处理后,再用阳极溶出伏安(ASV)方法测定。讨论了辐射条件,并通过重复性、回收率及线性关系来证实方法的可靠性和准确性。与传统的湿式消化法相比,紫外辐射法有取样量少、温度低)、不易挥发、操作简便及较低的试剂空白值等优点。 相似文献
92.
Hikaru Tanaka Naofumi Uesato Koki Shigenobu 《Naunyn-Schmiedeberg's archives of pharmacology》1995,351(4):391-397
Chronotropic and inotropic effects of histamine were examined in isolated atrial and ventricular preparations from embryonic and hatched chicken hearts. Histamine produced positive chronotropic and inotropic responses both in embryonic and hatched hearts. The responses to histamine in middle embryonic myocardia, which were observed in the micromolar range, were antagonized by H2 antagonists but not by H1, H3 antagonists and propranolol. Isobutylmethylxantine, an inhibitor of phosphodiesterase, produced a leftward shift of the concentration-response curve for the chronotropic effect of histamine in the embryo. The responses to histamine in myocardia from hatched chicks, which were observed in the milimolar range, appeared concurrently with the responses to tyramine during development and were antagonized by beta adrenoceptor antagonists but not by any of the histamine antagonists. The positive inotropic response to histamine in hatched ventricular preparations were greatly attenuated by reserpine pretreatment or in the presence of desipramine. Thus, we demonstrated that exogenously applied histamine produces positive chronotropic and inotropic responses in developing chicken hearts and that the mechanisms are different between embryonic and hatched chicks: direct action on H2 receptors in the embryonic heart and release of norepinephrine from sympathetic nerve terminals in hatched hearts. 相似文献
93.
本文采用转蓝法紫外分光光度法测定了三家药厂七批白霉素片体外溶出度,求得T_(50),Td威布尔函数参数具有显著差异,表明不同厂家所生产的白霉素片的溶出度相差显著,提出了影响药物溶出的某些因素,建议国产白霉素片有必要制定溶出标准。 相似文献
94.
Dr M. Weeke-Lüttmann 《European journal of epidemiology》1994,10(4):513-514
The epidemiological situation calls for almost yearly changes in the antigenic composition of influenza vaccine, thus necessitating fresh licensing procedures. Since the time for bringing a new vaccine onto the market should be relatively short, the following work of all parties involved must be done expeditiously: 1) WHO recommendations on new virus strains and their subsequent adaptation by the EEC (February/March); 2) Distribution of the new virus strains to the International Reference Centers for Influenza in the UK and USA (February/ March); the centers later issue reference materials for the determination of the haemagglutinin antigen concentration (April/May); 3) Production and testing of seed virus by manufacturers, as well as validation of the producer's inactivation process for the new virus strains (May/June); 4) Licensing of the vaccines by the National Control Authority (Paul-Ehrlich-Institute) (June/July); in the case of previously licensed products, the procedure is limited essentially to the approval of the detailed protocol of production and tests on the new virus strains, clinical studies not being required before licensing because of a lack of time; 5) Paul-Ehrlich-Institute's test for batch release, according to Directive 89/342/EEC, besides protocol approval, conducts material testing of the endotoxin and antigen content of each vaccine lot; the assay for the antigen quantification is especially laborious and sometimes must be repeated because of test invalidity. 相似文献
95.
Controlled release of sugar and toxicant from a novel device for controlling pest insects 总被引:1,自引:0,他引:1
Xing Ping Hu Baruch S. Shasha Michael R. McGuire Ronald J. Prokopy 《Journal of controlled release》1998,50(1-3):257-265
A novel biodegradable device, designed for long-lasting residual effectiveness of feeding stimulant (sugar) and insecticide (dimethoate) against apple maggot flies and other insects, was formulated. The device is an 8-cm diameter fruit-mimicking sphere, consisting of 42–50% sugar entrapped in a mixture of gelatinized corn flour and wheat flour in the presence of glycerin, and coated with a layer of latex paint containing dimethoate and sugar. We found that the outer layer of paint prevents cracking of the sphere upon drying and creates a barrier to control the release of both sugar and dimethoate. Releases of each ingredient were screened first by chemical analysis and then by bioassays in the laboratory and in field cages against apple maggot flies. Chemical analysis demonstrated strong potential for controlled release of water-soluble feeding stimulant and water-insoluble insecticide measured as a function of the amount of rainfall and duration of exposure time. Field results showed greater than 70% insecticidal activity after 11 weeks of sphere exposure in an orchard. This device has the potential to be used for a variety of insect-control applications through manipulating its shape, color and texture into forms known to be attractive to target insects, and by employing various toxicants designed to be effective against such insects. 相似文献
96.
Norbert T. Sandor Attila Brassai Attila Pliskas Balazs Lendvai 《Brain research bulletin》1995,36(5):483-486
The effect of the nitric oxide synthase inhibitor N-nitro-
-arginine methyl ester (L-NAME) on the basal and stimulation-evoked release of dopamine (DA) and acetylcholine (ACh) was investigated in rat striatum. The experiments were carried out in isolated superfused striatal slices, loaded with either [3H]-dopamine or [3H]-choline.We have found that L-NAME reduced the elecrical field stimulation-evoked release of DA, while its enantiomer N-nitro-D-arginine methyl ester (D-NAME) was ineffective. In the presence of the nitric oxide (NO) precursor
-arginine L-NAME failed to influence DA release. Furthermore, treatment with the N-methyl-
-aspartate (NMDA) receptor antagonist MK-801 completely reversed the effect of L-NAME on striatal DA release. In contrast, L-NAME had no effect on either the basal or the stimulation-evoked ACh release in any experimental conditions studied.Our data indicate that endogenously produced NO is involved in the modulation of striatal DA, but not in ACh release. Furthermore, it seems likely that the modulatory effect of NO is linked to activation of presynaptic NMDA receptors located on the striatal dopaminergic nerve terminals. 相似文献
97.
Ant nio F. Ambr sio Jo o O. Malva Ars lio P. Carvalho Caetana M. Carvalho 《European journal of pharmacology》1997,340(2-3):301-310
The effects of the adenosine A1 receptor agonist, N6-cyclopentyladenosine (CPA), on both the increase in intracellular free Ca2+ concentration ([Ca2+]i) and on the release of endogenous glutamate in rat hippocampal synaptosomes were studied. The inhibitory effect of CPA on the increase in [Ca2+]i stimulated with 4-aminopyridine was neutralized by the adenosine A1 receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). The inhibitory effect of CPA was greater in synaptosomes from the CA1 subregion than in whole hippocampal synaptosomes. The inhibitory effects of both CPA and of the Ca2+ channel blockers, ω-conotoxin GVIA, ω-conotoxin MVIIC or ω-conotoxin GVIA plus ω-conotoxin MVIIC, were greater than those caused by the Ca2+ channel blockers. The release of endogenous glutamate was inhibited by 41% by CPA. The inhibition observed when CPA and ω-conotoxin GVIA or CPA and ω-conotoxin MVIIC were present was also greater than the inhibition by the Ca2+ channel blockers alone. The presence of both ω-conotoxin GVIA and ω-conotoxin MVIIC did not completely inhibit the release of glutamate, and CPA significantly enhanced this inhibition. The membrane potential and the accumulation of []tetraphenylphosphonium of polarized or depolarized synaptosomes was not affected by CPA, suggesting that adenosine did not increase potassium conductances. The present results suggest that, in hippocampal glutamatergic nerve terminals, adenosine A1 receptor activation partly inhibits P/Q- and other non-identified types of Ca2+ channels. 相似文献
98.
Slices from rat midbrain containing the raphe nuclei and from hippocampus were prepared, loaded with [3H]5-HT and superfused and the resting and the electrically stimulated [3H]5-HT release was measured. The 5-HT3 receptor agonist 2-methyl-5-HT (1 to 10 μmol/l) increased the resting tritium outflow in superfused raphe nuclei slices, EC50 5.3 μmol/l. The 2-methyl-5-HT-induced increase of tritium outflow was an external Ca2+-independent process and was not altered by reserpine pretreatment but it was reversed by addition of the 5-HT uptake inhibitor fluoxetine (1 μmol/l). The 5-HT3 receptor antagonists ondansetron and GYKI-46 903 (1 μmol/l) did not antagonize the stimulatory effect of 2-methyl-5-HT on resting tritium outflow. 2-Methyl-5-HT in lower concentration increased the electrically induced tritium overflow from raphe nuclei slices (EC50 0.56 μmol/l) and also from hippocampal slices preloaded with [3H]5-HT. These effects were reversed by 1 μmol/l of ondansetron and GYKI-46903. The 5-HT3 receptor antagonists (1 μmol/l) were without effects on depolarization-evoked [3H]5-HT release at 2 Hz stimulation, when 10 Hz stimulation was used, ondansetron and GYKI-46 903 reduced the tritium overflow from raphe nuclei slices. These data indicate that 5-HT3 receptors positively alter depolarization-induced somatodendritic 5-HT release in the raphe nuclei. They also show that 2-methyl-5-HT is able to evoke 5-HT release not only from vesicles but also from cytoplasmic stores via a transporter-dependent exchange process. 相似文献
99.
The actions of the nonsteroidal antiinflammatory drug niflumic acid were studied on frog neuromuscular preparations by conventional electrophysiological techniques. Niflumic acid reduced the amplitude and increased the latency of endplate potentials in a concentration-dependent manner. Neuromuscular junctions pretreated with niflumic acid (0.05–0.5 mM) showed much less depression than control when they were stimulated with trains of impulses. Inhibition of acetylcholine release was reverted by raising the extracellular Ca2+ concentration but not by simply washing out the preparations with niflumic acid-free solutions. Pretreatment with indomethacin (0.1 mM), another nonsteroidal antiinflamatory drug, did not affect the niflumic acid-induced inhibition of evoked responses. Niflumic acid (0.1 mM) did not change the amplitude of miniature endplate potentials and had a dual action on the frequency of miniatures: it decreased their frequency at 0.1 mM whereas it produced an enormous increase in the rate of spontaneous discharge at 0.5 mM. Niflumic acid (0.1–1 mM) reversibly increased the amplitude and affected the kinetics of presynaptic voltage-activated K+ current and Ca2+-activated K+ current in a concentration-dependent manner. Niflumic acid (0.1–1 mM) irreversibly decreased the amplitude and reversibly affected the kinetics of the nodal Na+ current. Indomethacin (0.1 mM) had no effect on presynaptic currents. In conclusion, niflumic acid reduces acetylcholine release by increasing presynaptic K+ currents. This may shorten the depolarizing phase of the presynaptic action potential and may reduce the entry of Ca2+ with each impulse. 相似文献
100.
The purpose of this cross-sectional study was to determine whether measures on a selected groups of visual and psychomotor variables distinguished between groups of elite, intermediate and novice table tennis players. The variables included commonly of Melbourne measured clinical functions such as static visual acuity, extent of visual field and oculomotor balance and more experimental visual tasks such as recognition of, peripheral targets, saccadic latency and dynamic visual acuity. Psychomotor performance was assessed by measures of simple reaction time, choice response time and hand movement time. Although elite level competitors had significantly better dynamic visual acuity, a wider visual field and superior recognition of peripheral targets compared to less skilled competitors, the magnitude, or practical significance of these differences was not great and individually accounted for less than 5 per cent of population variance. Elite competitors had significantly faster psychomotor responses than novice players with die skill variables individually accounting for between 21 per cent and 62 per cent of population variance in psychomotor performance. These results indicate that the psychomotor parameters could be a useful part of a test battery for talent identification amongst table tennis players. 相似文献