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   26660篇
  免费   1333篇
  国内免费   116篇
耳鼻咽喉   150篇
儿科学   390篇
妇产科学   530篇
基础医学   3322篇
口腔科学   791篇
临床医学   1878篇
内科学   6458篇
皮肤病学   501篇
神经病学   2401篇
特种医学   1311篇
外科学   4106篇
综合类   106篇
预防医学   741篇
眼科学   481篇
药学   1981篇
中国医学   76篇
肿瘤学   2886篇
  2023年   106篇
  2022年   242篇
  2021年   449篇
  2020年   250篇
  2019年   360篇
  2018年   460篇
  2017年   350篇
  2016年   435篇
  2015年   457篇
  2014年   627篇
  2013年   797篇
  2012年   1200篇
  2011年   1362篇
  2010年   719篇
  2009年   670篇
  2008年   1208篇
  2007年   1254篇
  2006年   1223篇
  2005年   1244篇
  2004年   1232篇
  2003年   1173篇
  2002年   1204篇
  2001年   961篇
  2000年   959篇
  1999年   960篇
  1998年   367篇
  1997年   282篇
  1996年   281篇
  1995年   216篇
  1994年   192篇
  1993年   183篇
  1992年   666篇
  1991年   584篇
  1990年   610篇
  1989年   589篇
  1988年   499篇
  1987年   471篇
  1986年   458篇
  1985年   409篇
  1984年   283篇
  1983年   243篇
  1980年   93篇
  1979年   240篇
  1978年   148篇
  1977年   128篇
  1975年   103篇
  1974年   96篇
  1972年   106篇
  1971年   103篇
  1969年   102篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Temporal evolution of internal memory states in a terrestrial mollusk, Limax flavus, was studied using cooling-induced retrograde amnesia. The slug was conditioned to avoid carrot odor by temporally correlated presentation of carrot juice and a bitter-taste stimulus of quinidine sulfate. We could induce retrograde amnesia by cooling of the conditioned slug immediately after the training trial. Thus, we studied the memory states in the slug using the retrograde amnesia according to strategies used in the studies of memory states in mammals or insects. In the early process of memory acquisition, at least two distinctive memory states were observed, short-term memory and long-term memory (LTM). For LTM, two states were also observed. One was a reactivated state of LTM, which was sensitive to the cooling used to induce the amnesia. The other was a so-called resting state of LTM, which was insensitive to cooling. A few days after memory acquisition, further evolution was observed in that the amnesia could not be induced even if the memory trace was reactivated. The results obtained in Limax flavus was comparable with those obtained in a variety of animals.  相似文献   
102.
A sensitive enzyme-linked immunosorbent assay (ELISA) was used in a retrospective study of placental alkaline phosphatase (PLAP) levels in serum, cerebrospinal fluid (CSF), and intratumoral cyst fluid in primary intracranial germinoma. The ELISA showed no cross-reactivity with intestinal alkaline phosphatase except in very high concentrations, after samples had been heat-treated. Three patients with germinoma were studied for serum PLAP levels and in all the levels were elevated (3.78, 0.52, and 2.11 IU/liter). Two of the germinoma patients were studied for PLAP levels in the CSF, and both had elevated levels (0.83 and 9.83 IU/liter). The intratumoral cyst fluid in one case of germinoma was tested for PLAP and the level was found to be very high (603 IU/liter). These PLAP levels decreased concomitantly with the reduction in tumor size during irradiation. Serum PLAP levels were measured in 40 control adult male individuals and in the CSF of 20 nonpregnant patients with subarachnoid hemorrhage. The upper normal limits were 0.20 and 0.11 IU/liter in the serum and the CSF, respectively. All PLAP levels measured in the serum of patients with various brain tumors were 0.18 IU/liter or less. This study strongly suggests that PLAP is a clinically useful tumor marker for primary intracranial germinoma.  相似文献   
103.
104.
105.
Three noninvasive image-diagnosing methods, computed tomography (CT), scintigraphy with201T1C1 and99mTcOh4 , and ultrasonography (US), were preoperatively performed on 50 patients with chronic renal failure and secondary hyperparathyroidism who underwent total parathyroidectomy and parathyroid autograft. The detection rates of the 3 methods on the 191 excised parathyroid glands were compared according to weight and location. CT detected 57.1% of all glands and 78.6% of 103 glands weighing over 500 mg. Scintigraphy detected 51.8% and 75.7%, and US detected 42.4% and 53.4%, respectively. The detection rate of upper glands was best with CT at 58.9% and 89.1%; that of lower glands was best with scintigraphy at 65.3% and 80.4%. Although the combination of the 3 methods diagnosed 69.6% and 89.5%, CT and scintigraphy, the best 2 combinations, visualized 67.5% and 88.3%.
Resumen Tres métodos diagnósticos no invasivos, la tomografía computadorizada (TC), la centelleografía con201T1C1 y99mTcO4 y la ultrasonografía (US) fueron realizados preoperatoriamente en 50 pacientes con falla renal crónica e hiperparatiroidismo secundario sometidos a paratiroidectomía y autotransplante paratiroideo. Las tasas de detección de los 3 métodos fueron comparados sobre las 191 glándulas paratiroideas resecadas en relación a los pesos y a los sitios de ubicación. La TC detectó el 57.1% del total de glándulas y el 78.6% de aquellas glándulas (103) con pesos superiores a 500 mg. La centelleografía detectó 51.8% y 75.7%, y la US 42.4% y 53.4% respectivamente. La tasa de detección para las glándulas superiores fue optima con TC, con 58.9% y 89.1%; la de las glándulas inferiores fue óptima con centelleografía, con 65.3% y 80.4%. Aunque la combinación de los 3 metodos diagnosticó el 69.6% y 89.5%, la TC y la centelleografía, la mejor de las combinaciones, visualizó el 67.5% y el 88.3% respectivamente.

Résumé Trois méthodes d'imagerie non invasives, la tomodensitométrie, la scintigraphie (avec T1C1210 et TcO4 99m), et l'ultrasonographie ont été pratiquées avant l'intervention chez 50 malades qui présentaient une insuffisance rénale chronique compliquée d'hyperparathyroïdisme secondaire et qui furent traités par parathyroïdectomie totale et autogreffe parathyroïdienne. Les taux de détection de ces 3 méthodes concernant 191 glandes parathyroïdes réséquées ont été évalués en fonction du poids et du siège des lésions. La tomodensitométrie a permis de découvrir 57.1% de toutes les glandes et 78.6% des glandes dont le poids dépassait 500 mg; la scintigraphie 51.8% et 75.7%; l'ultrasonographie 42.4% et 53.4%. Le taux de détection des glandes supérieures fut plus élevé avec la tomodensitométrie: 58.9% et 89.1%; celui des glandes inférieures le fut avec la scintigraphie: 65.3% et 80.4%. Si la combinaison des 3 méthodes permet le diagnostic dans 69.6% et 89.5% des cas la tomodensitométrie associée seulement à la scintigraphie donne des résultats très voisins, les taux respectifs étant de 67.5% et de 88.3%.


Presented at the International Association of Endocrine Surgeons in Paris, September 1985.  相似文献   
106.
107.
108.
109.
Many Tau-positive glia with paired nuclei and astrocyte type morphology were identified in three brains from patients with progressive supranuclear palsy (PSP). They were positive by Bielschowsky's and Bodian's silver staining as well as by immunostaining with Tau-2, Alz-50, anti-GFAP and anti-paired helical filament antibodies, but not with anti-ubiquitin antibody. They were predominantly localized in the striatum, thalamus and frontal cortex but were not seen in white matter and were not plentiful in areas of heavy neuronal degeneration. Electron microscopy clearly showed the nuclear pairing and localized the Tau protein to bundles suggestive of microtubules in the cytoplasm and proximal processes. Such glial cells were rarely seen in cases of other neurodegenerative diseases or neurologically normal controls. These data suggest that there is an unusual gliotic reaction in PSP in brain areas which show relatively little neuronal loss.  相似文献   
110.
The clinical significance of eosinophils in urine was examined. Eosinophils were found in 9 out of 10 cases of interstitial cystitis, and there were more than 50 eosinophils in 50 fields in 6 of these cases. Although the number of eosinophils almost correlated with the number of leucocytes, the relationship between eosinophils and leucocytes in interstitial cystitis was different in acute and chronic cystitis. Since urinary eosinophils could be observed in cases of interstitial cystitis in which leucocytes were as low as 3 to 10 per field and the number of eosinophils was not decreased by chemotherapy, the urinary eosinophils in interstitial cystitis may be of allergic significance and reflect eosinophilic infiltration into the bladder wall.  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