首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   37417篇
  免费   1933篇
  国内免费   191篇
耳鼻咽喉   484篇
儿科学   770篇
妇产科学   484篇
基础医学   5025篇
口腔科学   829篇
临床医学   2390篇
内科学   9418篇
皮肤病学   1069篇
神经病学   2611篇
特种医学   1757篇
外国民族医学   1篇
外科学   6529篇
综合类   184篇
一般理论   4篇
预防医学   902篇
眼科学   493篇
药学   2525篇
中国医学   98篇
肿瘤学   3968篇
  2023年   174篇
  2022年   310篇
  2021年   662篇
  2020年   412篇
  2019年   500篇
  2018年   641篇
  2017年   549篇
  2016年   703篇
  2015年   693篇
  2014年   988篇
  2013年   1148篇
  2012年   1768篇
  2011年   1952篇
  2010年   1168篇
  2009年   1094篇
  2008年   1810篇
  2007年   1998篇
  2006年   1920篇
  2005年   2002篇
  2004年   1877篇
  2003年   1723篇
  2002年   1765篇
  2001年   1131篇
  2000年   1046篇
  1999年   1036篇
  1998年   522篇
  1997年   371篇
  1996年   415篇
  1995年   336篇
  1994年   276篇
  1993年   297篇
  1992年   715篇
  1991年   621篇
  1990年   612篇
  1989年   586篇
  1988年   559篇
  1987年   526篇
  1986年   498篇
  1985年   457篇
  1984年   353篇
  1983年   282篇
  1982年   187篇
  1979年   260篇
  1978年   171篇
  1977年   197篇
  1973年   184篇
  1972年   192篇
  1971年   200篇
  1970年   173篇
  1969年   191篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
We describe a case of aldosterone-producing adrenocortical adenoma (APA) associated with a probable post-operative adrenal crisis possibly due to subtle autonomous cortisol secretion. The patient was a 46-year-old female who suffered from severe hypertension and hypokalemia. CT and MRI scans revealed a 2-cm diameter adrenal mass. The patient's plasma aldosterone level was increased, and her plasma renin activity was suppressed, both of which findings were consistent with APA. Cushingoid appearance was not observed. Morning and midnight serum cortisol and plasma adrenocorticotropic hormone (ACTH) levels were all within the normal range. Her serum cortisol level was suppressed to 1.9 microg/dl as measured by an overnight 1-mg dexamethasone suppression test, but was incompletely suppressed (2.7 microg/dl) by an overnight 8-mg dexamethasone suppression test. In addition, adrenocortical scintigraphy showed a strong uptake at the tumor region and a complete suppression of the contra-lateral adrenal uptake. After unilateral adrenalectomy, she had an episode of adrenal crisis, and a transient glucocorticoid replacement improved the symptoms. Histopathological studies demonstrated that the tumor was basically compatible with APA. The clear cells in the tumor were admixed with small numbers of compact cells that expressed 17alpha-hydroxylase, suggesting that the tumor was able to produce and secrete cortisol. In addition, the adjacent non-neoplastic adrenal cortex showed cortical atrophy, and dehydroepiandrosterone sulfotransferase immunoreactivity in the zonae fasciculata and reticularis was markedly diminished, suggesting that the hypothalamo-pituitary-adrenal (HPA) axis of the patient was suppressed due to neoplastic production and secretion of cortisol. Together, these findings suggested that autonomous secretion of cortisol from the tumor suppressed the HPA axis of the patient, thereby triggering the probable post-operative adrenal crisis. Post-operative adrenocortical insufficiency should be considered in clinical management of patients with relatively large APA, even when physical signs of autonomous cortisol overproduction are not apparent.  相似文献   
12.
We report a 53-year-old woman with severe Graves' ophthalmopathy accompanied by uncontrolled myasthenia gravis. She presented remarkable exophthalmos, chemosis, and restriction of eye movement. Despite plasma exchange, steroid pulse therapy, local injection of steroid, and irradiation, ocular symptoms did not ameliorate. Since optic neuropathy was seen, orbital decompression surgery was performed in the left eye. Bilateral chemosis was improved after the surgery. Five years after surgery, there was no ocular palsy in the operated left eye, but in the contralateral eye. For the good prognosis of the eye movement, orbital decompression might be recommended in the severe Graves' ophthalmopathy accompanied by the optic neuropathy and/or ophthalmoplegia with proptosis.  相似文献   
13.
Direct measurement of intra-arterial blood pressure (BP) for 24-h provides approximately 100,000 values that vary enormously, but each (BPi) can be expressed by the equation BPi = BP0 + DeltaBPi (BP0, base BP; DeltaBPi, BP increment, i=1, 2, ..., 100 x 10(3)). About 20% of outpatients with hypertension exhibit white-coat hypertension (WCH). In such patients, DeltaBPc (i = c; c, time at the clinic) is surmised to be large. A method for explaining the physiological factors in DeltaBPc and the estimation of base BP in the outpatient clinic is important. This study addresses this issue. A total of 293 subjects were divided into four groups: 1) WCH group, 45 individuals (office BP > or = 140/90 mmHg and 24-h indirect BP < 125/80 mmHg); 2) normotensive (NT) group, 84 controls matched for age and sex; 3) WHO-I group, 95 hypertensive patients with WHO stage I (office BP > or = 140/90 mmHg and 24-h BP > or = 125/80 mmHg); and 4) WHO-II group, 69 hypertensive patients with WHO stage II. Their BPc and heart rate (HR; HRc, clinic HR) values were measured by a BP-ECG monitoring device in the outpatient clinic. Power-spectral analysis was used to obtain the ratio between the low-frequency component (LF) and high-frequency component (HF) of ECG-RR variability (LF/HF = LH). Twenty-four-hour indirect BP (and BP0) and base HR (HR0) were measured by a portable device (TM2425) at 30-min intervals. Then, DeltaBPc (= BPc - BP0) was estimated by performing linear multivariate analysis applying the model equation DeltaBPc = (BPc -alphaLH)(1-betaHR0/HRc) + epsilon to the above variables (alpha and beta, constant values; epsilon, error). This model equation made it possible to estimate BP0 (and DeltaBPc) with a high coefficient of correlation (r > or = 0.85, mean of error less than 0.82 +/- 5.9 mmHg). The predictive accuracy for discrimination between WCH and sustained hypertension (WHO-I and WHO-II groups) by this equation was 88%. The new DeltaBP-estimation device (BP-ECG monitor) enabled us to infer BP0 and is therefore useful in estimating WCH in the outpatient clinic.  相似文献   
14.
15.
Living donor liver transplantation (LDLT) for patients with portal vein thrombosis (PVT) involves technical difficulty. The aim of this research was to analyze their preoperative diagnosis of PVT, operative procedures, and postoperative courses of patients with preoperative PVT. Thirty-nine patients of 404 adult patients (9.7%) undergoing LDLT in our hospital from 1996 June to 2004 December had PVT at their transplantation. Twenty-nine patients had intractable ascites, 21 had gastrointestinal bleeding, and 18 had encephalopathy. The thrombus was located in the portal trunk in 23, in the portal trunk and superior mesenteric vein (SMV) in 7, and developed into the SMV and the splenic vein in 8. The occlusive grade was partial in 29, and complete in 10 patients. The thrombus was removed by a simple technique, and eversion and/or incision technique, or total removal of the portal vein (PV). The PV was reconstructed with the thrombectomized native PV, with an interposed vein graft, or porto-caval hemitransposition. Advanced PVT had a significant impact on blood loss and hospital mortality. Three out of 10 patients with residual PVT required radiological and/or surgical intervention after transplantation. In conclusion, thorough planning is essential for a successful LDLT outcome for patients with preexisting PVT.  相似文献   
16.
Three hundred and twenty samples of subgingival plaque were obtained from 80 caucasian girls, ranging from 10 to 13 years of age. The samples were analyzed to verify the influence of age upon colonization of the gingival sulcus by microorganisms potentially pathogenic to the periodontal tissues. The gingival and plaque status were evaluated through the gingival index (GI) and plaque index (PlI) and the microflora was assessed by the enzymatic method benzoyl-arginine-naphthylamide (BANA). The results of the BANA test were positive for 62.50% of the tested individuals and 40% of the examined sites. The influence of age was statistically significant on BANA reactivity, and the number of positive sites was greater at 11 (57.5%) than at 12 years (28.8%).  相似文献   
17.
Thirty-seven patients with primary aldosteronism were treated by unilateral total adrenalectomy during a 7-year period (1981–1987). The 37 patients were classified into 3 groups on the basis of adrenal pathology: unilateral solitary adenoma, 23 cases (group 1); unilateral adenomas, 3 cases (group 2); and adenoma with multiple macro- or microscopic nodules, 11 cases (group 3). The preoperative conditions of the patients (age, duration of hypertension, plasma renin activity, plasma aldosterone concentration, and serum potassium concentration), postoperative sequential changes of hormone levels, and outcome of hypertension were compared among the groups in order to determine whether the differences of adrenal pathology would affect the postoperative course. The preoperative parameters excluding age at surgery did not differ significantly among the 3 groups. The mean age in group 3, however, was slightly higher than in groups 1 and 2 (47.8 versus 42.8 versus 42.7 years). Postoperative hormonal changes were also similar, particularly in groups 1 and 3, staying within the normal range throughout the follow-up period (mean, 31 months; range, 3–86 months). However, postoperative improvement of hypertension showed marked differences, being significantl retarded in patients with multinodular lesions (group 3), about half of whom remained hypertensive even after 1 year. Nodular lesions other than adenoma(s) were, therefore, thought not to contribute to hormonal excess but to result from intractable hypertension.
Resumen Treinta y siete pacientes con aldosteronismo primario fueron tratados mediante adrenalectomía total unilateral en un período de 7 años (1981–1987). Los 37 pacientes fueron clasificados en 3 grupos con base en la patología adrenal: adenoma solitario unilateral, 23 casos (grupo I); adenomas unilaterales, 3 casos (grupo 2); y adenoma con múltiples macro-o micronódulos, 11 casos (grupo 3). Las condiciones preoperatorias de los pacientes (edad, duración de la hipertensión, actividad de renina plasmática, concentración plasmática de aldosterona, y concentración sérica de potasio), los cambios postoperatorios secuenciales en los niveles hormonales, y el resultado de la hipertensión fueron comparados en los 3 grupos, con el objeto de determinar si las diferencias en la patología adrenal podrían afectar la evolución postoperatoria. Los parámetros preoperatorios, excluyendo la edad en el momento de la cirugía, no diferieron significativamente en los 3 grupos. La edad promedio en el grupo 3, sin embargo, fue ligeramente superior en los grupos 1 y 2 (47.8 versus 42.8 versus 42.7 años).Los cambios hormonales postoperatorios también fueron similares, particularmente en los grupos 1 y 3, manteniéndose dentro del rango normal a través del seguimiento (promedio, 31 meses; rango, 3–86). Sin embargo, la mejoría postoperatoria de la hipertensión exhibió diferencias marcadas, con aparación significativamente tardía en pacientes con lesiones nodulares (grupo 3); aproximadamente la mitad de éstos permanecieron hipertensos aún después de un año. Por consiguiente, se piensa que las lesiones nodulares diferentes del adenoma(s) no contribuyen al exceso hormonal sino que resultan de la hipertensión intratable.

Résumé Trente-sept patients ayant un hyperaldostéronisme primaire ont eu une surrénalectomie totale unilatérale entre 1981 et 1987. Ces 37 patients ont été classés en 3 groupes selon la pathologie surrénalienne: adénome solitaire unilatéral, 23 cas (groupe 1); adénome unilatéral, 3 cas (groupe 2); et adénome avec nodules micro ou macroscopiques multiples, 11 cas (groupe 3). On a comparé les données préopératoires (âge, durée de l'hypertension, activité rénine plasmatique, concentration d'aldostérone plasmatique et kaliémie), les changements hormonaux postopératoires, et l'évolution de l'hypertension afin de déterminer si des différences de pathologie surrénalienne peuvent influencer l'évolution postopératoire. Les paramètres préopératoires (excepté l'âge) ne différaient pas de façon significative parmi les 3 groupes. L'âge moyen était plus élevé dans le groupe 3 que dans les groupes 1 et 2 (47.8 versus 42.8 versus 42.7 ans).Les variations hormonales postopératoires étaient également similaires, surtout dans les groupes 1 et 3, restant dans les limites de la normale pendant la période de suivi (moyenne, 31 mois; extrêmes, 3 à 86 mois). Cependant l'amélioration de l'hypertension postopératoire était différente, retardée de façon significative chez les patients ayant des lésions multinodulaires (groupe 3), la moitié d'entre eux restant hypertendus après un an. Les lésions nodulaires, étant donné que les adénomes ne donnent pas d'hypersécrétion hormonale, peuvent traduire plutôt une hypertension prolongée.


Presented at the International Association of Endocrine Surgeons in Toronto, Ontario, Canada, September, 1989.  相似文献   
18.
We evaluated whether we could predict the neurologic outcome in 55 out-of-hospital cardiac arrest patients using auditory brainstem responses (ABR). ABR patterns were classified into one of 3 types by evaluation of 5 components: type 1, with all 5 components; type 2, lack of at least one response between the 2nd and 5th components; type 3, with only the first component or no response. The relation between the ABR patterns on the 3rd day following resuscitation and the neurologic outcome on hospital discharge was evaluated. The specificity that the 5 awake patients had type-1 ABR was 38%. The sensitivity that the 10 brain dead patients had type-3 ABR was 60%. In the type-1 ABR patients, the negative predictive value that the patients were awake was 100%. In the type-3 ABR patients, the negative predictive value that the patients became brain dead was 90.9%. These results suggest that ABR on the 3rd post-resuscitation day may not be useful for predicting if patients are awake or become brain dead, although the loss of components may be a sign of morbidity, and the presence of the 2nd or later components indicates possible future prevention of brain death.  相似文献   
19.
Unique formation of rodent cortical barrels by layer 4 neurones attracts study of the sensory function of cortical input stage neurones (layer 4) compared with that of output stage neurones (layer 5). We have recorded extracellular responses from rat somatosensory cortical neurones to deflections of contralateral vibrissae. Thirty-two layer 4 barrel neurones and 29 layer 5b neurones were studied. Whisker stimulations were ramp-and-hold deflections with one of six different ramp velocities (100–2.5 mm s−1) and one of four different plateau amplitudes (2000–200 μm). Twenty-four (6 × 4) different stimulus forms were applied to the tip of a whisker trimmed to 10 mm in a predetermined order in stimulus cycles of 20–50 repetitions. Spike counts for a period of 2560 ms in 10 ms bins were summed to construct a matrix of 24 peristimulus histograms for each neurone. Twenty-four amplitude and 24 velocity values were computed from counts during the plateau and ramp phases, respectively. To determine the amplitude- and velocity dependence of a neurone, an amplitude F value (the ratio of variations among-/within-amplitude of the amplitude value) and a velocity F value (ratio of variations among-/within-velocity of the velocity value) were derived by analysis of variance. The amplitude F value of the layer 4 barrel neurones was greater than that of the layer 5b neurones ( P < 0.0001). The velocity F value of the barrel neurones was smaller than that of the layer 5b neurones ( P = 0.0226). The results suggests that barrel neurones and layer 5b neurones tend to detect amplitude and velocity components of whisker deflection, respectively.  相似文献   
20.
The biochemical activities of 8 lysosomal acid hydrolases in leukemic cells from 48 patients were examined. Characteristic alterations were found in α-mannosidase, β-galactosidase and N-acetyl-β-glucosaminidase activities of leukemic cells. The level of α-mannosidase activity was much higher in myelo(mono)genous leukemias (AML, AMoL, AMMoL, CML and CMMoL) than in lymphogenous ones (ALL, T-cell leukemia, hairy cell leukemia and CLL) without exception. The β-galactosidase activity also differed as a result of α-mannosidase, except in T-cell leukemia. In T-cell leukemia it was within the range of normal lymphocytes, but in the other lymphogenous leukemias it was significantly below normal. N-acetyl-β-glucosaminidase activity in myelo(mono)genous leukemic cells was above the range of normal granulocytes. The changes in these enzyme levels were consistent. The lymphocytic or myelocytic nature of three cases of acute undifferentiated leukemia could be determined by enzyme studies. In two cases it was lymphocytic and in one it was myelocytic. The enzymatic abnormalities were also found in morphologically mature neutrophils from patients with not only chronic types (CML, CMMoL) but also acute types (AMoL, AMMoL) of leukemias, and were similar to those of their respective leukemic cells. Analysis of lysosomal enzymes (at least three of those mentioned above), can elucidate one of the biochemical properties of leukemic cells and may be valuable in the differentiation of leukemias.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号