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71.
Benzo[a]pyrene at an environmentally relevant dose is slowly absorbed by, and extensively metabolized in, tracheal epithelium 总被引:2,自引:0,他引:2
Gerde P; Muggenburg BA; Thornton-Manning JR; Lewis JL; Pyon KH; Dahl AR 《Carcinogenesis》1997,18(9):1825-1832
While tobacco smoke has been conclusively identified as a lung carcinogen,
there is much debate over which smoke constituent(s) are primarily
responsible for its carcinogenicity. Previous studies in our laboratory
suggested that highly lipophilic carcinogens are slowly absorbed in the
thicker epithelium of the conducting airways, potentially allowing for
substantial local metabolism. The bioactivation of polycyclic aromatic
hydrocarbons in airway epithelium may, hence, be important in tobacco
smoke-induced carcinogenesis. In the present study, the hypothesis of slow
absorption and substantial local metabolic activation of highly lipophilic
carcinogen in airway epithelium was tested in dogs. A single dose of
tritiated benzo[a]pyrene (BaP) dissolved in a saline/phospholipid
suspension was instilled in the trachea, just anterior to the carina. At
intervals of a few minutes up to 30 min over a 3-h period, blood samples
were drawn from the azygous vein, which drains the area around the point of
instillation, and from the systemic circulation. Tissue samples were taken
at the end of the experiment. The concentration of BaP with depth into the
tracheal mucosa was determined with autoradiography. BaP was slowly
absorbed into the trachea with a half-time of approximately 73 min, which
is consistent with diffusion-limited passage through the epithelium and
lead to local doses in the tracheal epithelium that were more than a
1000-fold those of other tissues. The long retention of BaP in the
epithelium provided the local metabolizing enzymes with high substrate
levels over a long period, resulting in extensive metabolism. At 3 h after
the exposure, 23% of the BaP-equivalent activity remained in the tracheal
mucosa. Of this fraction, 13% was parent compound, 28% was organic
extractable, 31% was water-soluble, and 28-7% of the instilled dose was
bound to tracheal tissues. These results explain the tendency of highly
lipophilic carcinogens, such as BaP, to induce tumors at the site of entry
and, furthermore, indicate that the highly lipophilic components of tobacco
smoke and polluted air may be the most important contributors to lung
tumors of the conducting airways.
相似文献
72.
MT Bardella N Molteni L Prampolini AM Giunta AR Baldassarri D Morganti PA Bianchi 《Archives of disease in childhood》1994,70(3):211-213
The use of follow up studies was evaluated in 128 patients with coeliac disease during their first visit to a department for adults. The original diagnosis had been made in childhood in all patients. Fifty eight (45%) of the subjects were following a gluten free diet, 23 (18%) were following a gluten free diet but with occasional gluten consumption, and 47 (37%) had adopted an unrestricted, gluten containing diet for a mean of 11.2 years. There was no correlation in individual subjects between the presence of symptoms, biochemical and immunological abnormalities, severity of histological findings, and the amount of dietary gluten, despite the greater frequency of symptoms in the group following an unrestricted diet than in the other two groups. Short stature and epilepsy with cerebral calcifications only occurred in patients following an unrestricted diet. As only diagnosis based on two or three biopsy samples and regular follow up correlated positively with dietary compliance, it is suggested that a histologically confirmed diagnosis of coeliac disease and regular lifelong follow up are essential in the management of these patients. 相似文献
73.
STOTT DJ; MCLELLAN AR; FINLAYSON J; CHU P; ALEXANDER WD 《QJM : monthly journal of the Association of Physicians》1991,78(1):77-84
The clinical and biochemical characteristics of 15 elderly patientswith low levels of thyrotrophin (TSH) (<0.1 mU/L) but normalfree tri-iodothyronine, (T3) and free thyroxine (T4) (groupS) were compared with 10 euthyroid subjects (group E) and 10hyperthyroid patients (group T). Free T3 and free T4 were significantlyhigher (p<0.05) in group S(6.3±0.5 and 18.6±1.0pmol/l, respectively) than in group E(4.6±0.3, 12.6+0.6).In common with elderly hyperthyroid patients (group T)patientsin group S had few signs or symptoms of thyrotoxocosis, butthe Wayne score (clinical index of hyperthyroidism) was higherin group S than in euthyroid subjects (p<0.05). Thyroid microsomal,thyrogolobulin or thyrotrophin receptor antibodies were commonin group T (n=9)but not in groups S(n=2) or E(n=1). This suggestsa low prevalence of Graves' disease in group S compared to groupT. Combined thyrotrophin releasing hormone (TRH; 200 µgi.v.) and gonadotrophin releasing hormone GnRH; 100 µgi.v.) tests were performed; no cases of low TSH due to hypopituitarismwere identified in group S. During a mean of 7.9 (412)months of observation TSH reverted to the normal range (>0.2mU/L)in 7 of 15 patients in group S; thyroid hormone concentrationsrose above the normal range in four, however, only two patientsrequired treatment for hyperthyroidism. It is unlikely thatthe suppressed TSH of patients in group S was due to mild thyroidhormone excess; although this is often a transitory phenomenon,these patients are at increased risk of developing overt hyperthyroidism. 相似文献
74.
75.
76.
Immunologic effects of vitamin D 总被引:1,自引:0,他引:1
77.
78.
79.
Martínez Quesada M Trujillo Berraquero F Almendro Delia M Hidalgo Urbano R Cruz Fernández JM 《Revista espa?ola de cardiología》2005,58(4):450-452
Primary cardiac tumors are infrequent and usually benign. They can manifest as dyspnea, chest pain, palpitations, sudden death, peripheral embolism, cyanosis, or general symptoms. They are sometimes an incidental finding in an asymptomatic patient. We describe a 33-year-old man who was seen because of dyspnea and palpitations. Transthoracic echocardiography revealed, on the lateral wall of the left ventricle, an intramyocardial mass that was successfully resected surgically. The pathologic diagnosis was hamartoma of mature cardiac myocytes. We discuss the usefulness of imaging techniques for identifying cardiac masses. 相似文献
80.
Durán Ferreras A Duque San Juan P Durán Ferreras E Ponce Herrera C Acevedo Bañez I Cambil Molina T Castro Montaño J Rodríguez de Quesada y Tello B 《Revista espanola de medicina nuclear》2004,23(1):39-41
We present the case of a 78 year old man admitted to the hospital with progressive memory disorder. Neuropsychological examination showed inability to recognize familiar faces (prosopagnosia). MRI documented cortical atrophy, which did not explain the neurological deficit. CT did not show abnormalities. Most patients with prosopagnosia present brain atrophy, as they are more than 65 years old. Scanning by SPECT revealed hypoperfusion in the right parietotemporal region, which was worse in a later examination. 相似文献