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991.
Mercury and selenium interaction: A review   总被引:10,自引:1,他引:9  
This paper reviews studies on mercury and selenium interaction. It includes the effects of selenium on mercury toxicity on the organism, organ/tissue, and subcellular levels. The paper also touches on possible mechanisms for the "protective action" of selenium against mercury toxicity and deals briefly with the synergism between the two elements.  相似文献   
992.
A 24-year-old male underwent bone marrow transplantation for severe aplastic anemia. Posttransplantation complications included severe graft-versus-host disease and cytomegalovirus (CMV) infection manifested by gastrointestinal bleeding and apparent pneumonitis. Massive rectal bleeding necessitated exploratory laparotomy at which time a right colon resection was performed. Fifteen cecal ulcers were present which on histologixc examination revealed numerous cells containing characteristic intranuclear inclusions. Life-threatening gastrointestinal lesions associated with CMV infection will be seen with increasing frequency as more patients undergo the severe immunosuppression associated with bone marrow and organ transplantation. Prompt recognition and expeditious surgical management will result in improved survival in this high-risk population.
Résumé Chez un sujet de 24 ans qui avait subi une transplantation de moelle osseuse sort survenues des complications de rejet et une infection à cytomégalovirus qui s'est manifestée par une hémorragie digestive et une atteinte pulmonaire. L'abondance de l'hémorragie a imposé une laparotomie exploratrice qui a conduit à une hémicolectomie droite. Sur la pièce de résection on a découvert quinze ulcérations. L'examen histologique a montré qu'elles contenaient de nombreuses cellules dont le noyau présentait de nombreuses inclusions caractéristiques.Ce type de lésions digestives allant de pair avec une infection a cytomégalovirus devrait devenir de plus en plus fréquent chez les malades qui présentent des phénomènes immuno-dépressifs après transplantation d'organes ou de moelle osseuse. Il sera nécessaire de les reconnaitre rapidement pour les traiter chirurgicalement sans retard. C'est à ce prix que le risque d'évolution fatale pourra être réduit chez ces sujets à haut risque.
  相似文献   
993.
6-125I-iodo-2-methyl-1,4-naphthoquinol bis (diammonium phosphate) (6-125I-iodo-MNDP) has been synthesised and studied as the prototype of a class of potential radio-halogenated anti-cancer agents. The incorporated 125I provides Auger electron radiations which behave like high LET radiations in the treatment of tumours, though the accompanying X- and -radiations make an undersirable contribution to the total body dose. The in vitro experiments reported show that 6-125I-iodo-MNDP is selectively concentrated in the cells of some human malignant tumours by factor of about 15 to 20 or more in relation to the cells of normal origin studied. On the basis of dosimetric considerations and comparison with clinical treatment with tritiated methylnaphthoquinol diphosphate, practical dosage of 6-125I-iodo-MNDP is suggested and clinical indications and safety of use are discussed. The types of tumour of particular interest are inoperable cases of carcinoma of the colon, carcinoma of the pancreas, malignant melanoma and osteosarcoma. Further investigations are in progress.Beit Memorial Fellow for Medical Research  相似文献   
994.
Summary Dopamine was shown to act on the circular smooth muscle of the stomach body to cause contraction at a yohimbine-sensitive site (2) and a relaxation at a prazosin-sensitive site (1). Metoclopramide and tiapride failed to modify either response, failed to antagonise a relaxation to phenylephrine at 1(1 sites in the same tissue, and failed to modify the contractions caused by dopamine and phenylephrine at an 2-adrenoceptor site in the pyloric sphincter. However, (+)- and (–)-sultopride and (+)-sulpiride antagonised the dopamine-induced contractions of the stomach body indicating an 2-antagonist action. An ability to attenuate the relaxation of this tissue may reflect a displacement of the contraction curve to the right rather than an 2-antagonist action since the response to phenylephrine was not antagonised either in this tissue or in the pyloric sphincter. Within the central nervous system the (–)-enantiomers of sultopride and sulpiride have a highly selective dopamine receptor blocking action. This cotrasts with the present findings in the stomach musculature of a non-stereospecific antagonism at 2-type adrenoceptors.  相似文献   
995.
Nerve growth factor binds to two different specific receptors on responsive cells. The relationship of these two receptors is not fully understood at this time. We have studied the binding of labeled NGF to a different strain of white leghorn chicken embryo dorsal root ganglionic cells. The equilibrium dissociation constants for the two sites (K = 4.1 ± 1.8 × 10?11M, K = 1.0 ± 0.8 × 10?9M) are identical to those obtained previously. Also, the number of type I sites per cell (3.8 ± 1.3 × 103) is the same as that previously determined. However, the number of type II sites per cell (1.9 ± 1.3 × 104) is significantly different than that previously determined. This 2.5-fold decrease in the number of type II sites does not affect the concentration of NGF needed to obtain maximal fiber outgrowth from explanted sensory ganglia. The rate of association (1.2 ± 0.2 × 107 M?1 sec?1 at 22°C) of labeled NGF with receptors on sensory neurons from this different strain of chickens is identical to that previously obtained. The rate of association of NGF with its receptors on sensory neurons was also determined at 4°C. This rate constant (2.1 ± 1.1 × 106 M?1 sec?1) along with the rate constants obtained at 22° and 37°C were used to determine an activation energy for the binding of NGF to its receptors. The activation energy obtained (16.2 kcal/mole) suggests that binding is not a diffusion-controlled process.  相似文献   
996.
Summary Fifty-one patients with non-small cell lung cancer (NSCLC) were treated, during a phase II trial, with 4 demethylepipodophyllotoxin--d-ethylidene glucoside (VP16-213). Forty-nine were evaluable for response, and of these two (4%) had partial responses lasting 5 and 6 months. Prior treatment with chemotherapy may have adversely affected response rate; none of the 24 previously treated patients had a major response. Myelosuppression was the dose limiting toxicity. Anorexia, nausea and vomiting, partial alopecia, and chills plus hypotension during drug infusion were the other toxic effects. We conclude that VP16-213 has only minimal activity as a single agent in NSCLC.Supported in part by NIH Grant No. CA-05826 and CA-09027, and by NCI Contract NO-1-CM 972744Demethylepipodophyllotoxin--d-Ethylidene Glucoside (NSC141540) was supplied by the Drug Evaluation Branch of the National Cancer Institute  相似文献   
997.
Oxiperomide and tiapride are dopamine receptor antagonists claimed to have antidyskinetic properties in animal models and in the clinic. Halopemide and mezilamine are other dopamine antagonists predicted to lack extrapyramidal side effects in man on the basis of animal studies. Acute dyskinesias, a neuroleptic-induced acute extrapyramidal syndrome, were elicited in squirrel monkeys by oxiperomide (1 mg/kg), tiapride (30 mg/kg), and halopemide (10 mg/kg). The dyskinesias were virtually indistinguishable from those caused by a standard behaviorally equivalent dose of haloperidol (1.25 mg/kg PO) in the same individual monkeys. Mezilamine (0.3 mg/kg) also induced dyskinesias, which appeared to be less pronounced than those following haloperidol. The antidyskinetic properties of oxiperomide and tiapride evidently do not confer protection against dyskinetic movements induced by dopamine antagonism.  相似文献   
998.
A flow-limited physiologic mathematical model has been developed to describe the time course of 2deoxycoformycin (2dCF) concentrations in the plasma and tissues of mice following iv and ip doses. Urinary excretion is modeled as a linear process involving filtration and secretion, since kidney clearance exceeded estimated glomerular filtration rate. Intracellular binding is described as the sum of linear nonspecific binding plus strong saturable binding to adenosine deaminase. Pharmacokinetic parameters are determined by a sequential optimization scheme in which each tissue is studied by means of a hybrid model. The model has been used to predict pharmacokinetic behaviour of 2dCF in both normal and leukemic mice, and model simulations are compared with published data.  相似文献   
999.
The Raji human lymphoma line is able to remove O6-methylguanine(O6MeG) lesions introduced by treatment of cells with N-methyl-N'-nitro-N-nitroso-guanidine(MNNG). The reaction has a rapid phase in which 40% of theO6MeG is removed in the first 10 min. The capacity of cellsfor rapid O6MeG removal is limited and is saturated at concentrationsof MNNG which do not saturate the systems removing 3-methyladenine.Pretreatment of cells with MNNG inhibits their ability to removeO6MeG produced by a subsequent dose given after 2 h. Treatmentwith N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) is effectivein diminishing cellular capacity for O6MeG removal, and cellsunable to remove O6MeG and sensitive to the cytotoxic effectsof MNNG are also more sensitive to ENNG than their removal competentcounterparts. Regeneration of the ability to remove O6MeG requiresincubation of cells for periods > 24 h. The O6MeG removalsystem is similar to that found in adapted Escherichia colialthough the capacity of the Raji lymphoma line is much lowerthan that of the induced bacteria per unit of DNA.  相似文献   
1000.
Earlier studies showed that N-acetyl-2-aminofluorene (AAF) ismuch more carcinogenic than N-acetyl-2-amino-7-iodofluorene(AAIF). Subsequently it was found that substitution of C-8 ofguanine bases in DNA with AAF residues resulted in displacementof the guanine bases outside the DNA helix. This did not occurafter similar substitution with AAIF residues. As one approachto assessing the possible importance of this gross conformationaldifference to the carcinogenicity of AAF, the carcinogenic activitiesof two electrophilic esters, N-myristoyloxy-AAF and its 7-iododerivative, were compared by s.c. injection into male Fischerrats. On injection of a total of 64 µmol, each ester induceda high incidence of sarcomas, and the latent periods were similar.N-Myristoyloxy-AAIF was solvolyzed in aqueous media at aboutone-half the rate of N-myristoyloxy-AAF, and it was less than10% as reactive with native DNA as N-myristoyloxy-AAF. N-Myristoyloxy-AAFand N-myristoyloxy-AAIF were each less reactive than the correspondingacetoxy derivatives. These data suggest that the low carcinogenicityof AAIF as compared to that of AAF may not be associated withthe conformations of their adducts in the DNA. This differencein carcinogenicity may be related to differences in the ratesof metabolic activation and inactivation of these two amides.  相似文献   
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