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   8387篇
  免费   518篇
  国内免费   76篇
耳鼻咽喉   73篇
儿科学   170篇
妇产科学   93篇
基础医学   1100篇
口腔科学   122篇
临床医学   542篇
内科学   2342篇
皮肤病学   191篇
神经病学   523篇
特种医学   384篇
外科学   1497篇
综合类   24篇
预防医学   325篇
眼科学   175篇
药学   420篇
中国医学   6篇
肿瘤学   994篇
  2023年   51篇
  2022年   120篇
  2021年   253篇
  2020年   142篇
  2019年   187篇
  2018年   265篇
  2017年   195篇
  2016年   248篇
  2015年   239篇
  2014年   323篇
  2013年   366篇
  2012年   590篇
  2011年   545篇
  2010年   335篇
  2009年   272篇
  2008年   443篇
  2007年   394篇
  2006年   411篇
  2005年   416篇
  2004年   376篇
  2003年   421篇
  2002年   386篇
  2001年   157篇
  2000年   156篇
  1999年   144篇
  1998年   106篇
  1997年   94篇
  1996年   75篇
  1995年   61篇
  1994年   47篇
  1993年   51篇
  1992年   101篇
  1991年   101篇
  1990年   93篇
  1989年   70篇
  1988年   72篇
  1987年   56篇
  1986年   59篇
  1985年   50篇
  1984年   42篇
  1983年   47篇
  1982年   32篇
  1981年   28篇
  1979年   32篇
  1974年   36篇
  1973年   30篇
  1972年   23篇
  1971年   35篇
  1970年   34篇
  1969年   27篇
排序方式: 共有8981条查询结果,搜索用时 31 毫秒
31.
Risk of gallstones following gastrectomy in Japanese men   总被引:3,自引:0,他引:3  
The risk of gallstones developing after gastrectomy in middle-aged Japanese men was investigated in a study of 2,738 men aged between 48 and 56 years who underwent both gallbladder ultrasonography (US) and a barium study of the upper digestive tract. It was revealed that 61 men had gallstones, 37 had had their gallbladder removed previously, and 55 had a history of gastrectomy. The prevalence of gallstones was 3.5 times higher in the men who had previously undergone gastrectomy (7.7%) than in those who had not (2.2%) (P=0.03). Moreover, gallstones tended to be more prevalent in those who had undergone Billroth II gastrectomy (12.5%) compared with those who had undergone Billroth I gastrectomy (5.6%); however, the difference was not significant. These results indicate that gastrectomy using either Billroth I or Billroth II reconstruction predisposes to gallstone formation. Nevertheless, it was estimated that prior gastrectomy was responsible for no more than 5% of gallstones in the study population.  相似文献   
32.
Background: The intrathecal alpha2 -adrenergic agonist, clonidine, has been shown to have considerable antinociceptive effect, although clonidine causes hypotension and bradycardia The combination of intrathecal clonidine and local anesthetics enhances analgesic effects, whereas the combination may cause marked hypotension and motor blockade, which may limit the clinical application of the combination. Tizanidine, another alpha2 -adrenergic agonist, has also provided antinociception without producing pronounced hemodynamic changes. This study was designed to evaluate the antinociceptive and hemodynamic interactions of tizanidine and clonidine with lidocaine.

Methods: Male Sprague Dawley rats were chronically implanted with lumbar intrathecal catheters. The tail-flick test was used to assess the thermal nociceptive threshold. The ability of intrathecal tizanidine, clonidine, lidocaine, or the combinations of alpha2 -adrenergic agonist and lidocaine to alter the tail-flick latency was examined. To characterize the antinociceptive interaction, the isobolographic analysis was applied. Additionally, the motor function, blood pressure and heart rate after intrathecal administration of drugs and combinations were also monitored.

Results: Intrathecal tizanidine, clonidine, or the combinations increased the tail-flick latency in dose- and time-dependent fashion without affecting motor function. The order potencies (dose producing a 50% of peak effect, in micro gram) of tizanidine and clonidine were 1.8 and 0.75, respectively. With isobolographic analysis, tizanidine with lidocaine and clonidine with lidocaine showed significantly synergistic antinociceptive interaction. Potency ratio analysis and fractional analysis also confirmed the synergistic interaction. At the doses in the combinations showing comparable antinociception, tizanidine with lidocaine, unlike clonidine with lidocaine, did not affect motor function or blood pressure.  相似文献   

33.
Abstract: The possibility on placing electrodes at Fpz-A2 instead of C3-A2 was investigated to obtain a more stable configuration avoiding obstruction by the hair. Our original system of alpha wave detection by a microcomputer was used, and a total of 22 all-night hypnograms of five healthy young students waa recorded. Pearson's moment correlation coefficients of alpha wave % between the two positions were 0.780–0.948. Except for one subject, alpha wave % taken at Fpz-A2 tended to be 3–5% lower than that at C3-A2. The above analysis indicates that using EEG electrode position of Fpz-A2 is valid and useful as a stable electrode configuration for a long-time monitoring.  相似文献   
34.
A competitive enzyme immunoassay was developed for metabolites of 450191-S, a ring-opened derivative of triazolobenzodiazepines, in human serum. Three kinds of labelled antigens, beta-D-galactosidase conjugates, and antisera from three kinds of immunogens, bovine serum albumin conjugates, were tested and the hapten heterologous assay was selected. B/F separation was performed using immobilized second antibody and the enzyme activity was measured using fluorescent substrate. One of the serum metabolites, the carboxyl form, was extracted from acidified serum and measured by the assay. The minimum detectable concentration was 1.5 ng/ml in serum, 15 pg/tube. The intra-assay and inter-assay variances were 5.5% and 7.7% at 6 ng/ml of serum, respectively. Standard curves of other related metabolites were assessed with various combinations of labelled antigens and antibodies.  相似文献   
35.
36.
37.
Clinicopathologic studies were performed to establish rational criteria for total thyroidectomy as a treatment of follicular carcinoma. During the 4-year period from 1981 to 1984, total thyroidectomy was carried out on 23 patients in whom unequivocal vascular invasion and/or obvious extracapsular extension were disclosed on pathological study of the primary thyroid lesion. Although occult metastatic lesions were detected postoperatively in 5 patients, no distant metastases have been found in 12. Distant metastasis was clinically manifest on admission in the other 6 patients. The degree of vascular invasion at the primary lesion was not correlated with the occurrence of distant metastasis. However, 10 of the 15 patients with tumors characterized by a thick fibrous capsule had distant metastases, while all but 1 of 8 patients with a thin capsule showed no metastasis. Apparent capsular invasion seemed to increase the relative risk of distant metastasis. On the other hand, solid clusters of tumor cells containing a variable number of small follicles, which characterize Langhans' wuchernde Struma, were found in 6 patients, and 5 of them showed distant metastases. Thus, total thyroidectomy should be considered when (a) distant metastases are clinically apparent, (b) the primary lesion has a thick fibrous capsule with or without obvious capsular invasion, or (c) solid clusters of tumor cells are demonstrated microscopically.
Resumen Se realizaron estudios clinicopatológicos con el propósito de establecer criterios racionales para la tiroidectomía total en el tratamiento del carcinoma folicular. En el curso de un perfodo de 4 anos entre 1981 y 1984, se realizó tiroidectomía total en 23 pacientes en quienes se halló inequívoca invasión vascular y/o obvia extension extracapsular en el examen histopatológico de la lesión tiroidea primaria. Aunque postoperatoriamente se detectaron lesiones metastáticas ocultas en 5 pacientes, no se encontraron metástasis distantes en 12. Metástasis distantes eran clínicamente manifiestas en el momenta de la admisión en los otros 6 pacientes. El grado de invasión vascular en la lesión primaria no apareció correlacionado con la ocurrencia de metástasis distantes. Sin embargo, 10 de los 15 pacientes con tumores caracterizados por una cápsula gruesa y fibrosa tenían metástasis distantes, mientras solo 1 de 8 pacientes con tumores de cápsula fina mostró metástasis. La invasión capsular aparente parece incrementar el riesgo relativo de metástasis distantes. Por otra parte, agrupaciones sólidas de células tumorales con presencia de números variables de folículos pequeños, que caracterizan al wuchernde Struma de Langhans, fueron encontrados en 6 pacientes, 5 de los cuales mostraron metastasis distantes. Por lo tanto, se debe considerar la tiroidectomía total cuando: (a) haya metástasis distantes clínicamente aparentes, (b) la lesión primaria tenga una gruesa cápsula fibrosa con o sin invasión capsular obvia, y (c) se demuestren microscópicamente agrupaciones sólidas de células tumorales.

Résumé Une étude clinicopathologique a été menée pour déterminer les critères de thyroïdectomie totale comme traitement dans le cancer folliculaire de la thyroïde. Pendant 4 ans, de 1981 à 1984, 23 patients ont subi une thyroïdectomie totale pour envahissement vasculaire non équivoque et/ou extension extracapsulaire évidente découverte sur la pièce d'exérèse initiale. Cinq patients avaient des métastases occultes découvertes dans la période postopératoire, 6 avaient des métastases cliniquement évidentes, alors que 12 ne présentaient aucun signe de métastase à distance. Le degré d'envahissement vasculaire de la lésion primitive n'était pas corrélé avec la survenue de métastases à distance. Cependant, 10 des 15 patients à tumeurs caractérisées par un épaississement de la capsule fibreuse avaient des métastases à distance, alors que 7 des 8 patients avec une capsule mince n'avaient pas de métastases. L'envahissement capsulaire était associé à un plus grand risque de métastases à distance. Des amas solides de cellules tumorales contenant de petits follicules, le wuckernde struma de Langhans, étaient retrouvés dans 6 cas, dont 5 avaient des métastases à distance. Ainsi, la thyroïdectomie totale est préconisée lorsque (a) des métastases à distance sont cliniquement évidentes, (b) la lésion primitive possède une capsule fibreuse épaisse avec ou sans envahissement évident, et (c) on met en évidence des cellules tumorales en amas microscopiquement.


Presented at the International Association of Endocrine Surgeons in Sydney, Australia, September, 1987.  相似文献   
38.
A case of pancreatic tumor with features of both duct and islet cell components was found incidentally at autopsy in a 76 year old male who had died of intrahepatic cholan-giocarcinoma. The tumor, measuring about l.0cm in diameter, was located in the pancreatic tail. The tumor was composed of two distinct cell populations, islet cells and duct cells. Immunocytochemically, nearly all of the former cells were positive for insulin but negative for cytokeratin, carcinoembryonic antigen (CEA) and mucin, while the latter were positive for cytokeratin, CEA and mucin but negative for insulin. Additionally, a majority of the tumor cells that had formed islet-like structures were positive for neuron specific enolase (NSE), whereas NSE-positive cells were found only rarely in duct components. Electron microscopy confirmed the presence of two cell populations. Simultaneous occurrence of duct and islet cell components in a single pancreatic tumor indicates an intimate histogenetic relationship between pancreatic endocrine and duct cells. Acta Pathol Jpn 39: 328 335, 1989.  相似文献   
39.
The role of 5-HT1A and 5-HT1B receptors in entrainment function was studied in Otsuka Long Evans Tokushima fatty (OLETF) rats and control Long Evans Tokushima Otsuka (LETO) rats. Light-induced (100 lux, 30 min) Fos expression in the suprachiasmatic nucleus was studied. Light-induced Fos expression was significantly decreased in OLETF rats compared to that in LETO rats. The decrease of light-induced Fos expression in OLETF rats was significantly reversed by pretreatment with the 5-HT1B receptor antagonist, isamoltan (3 mg/kg, i.p.). Simultaneous administration of CGS12066B (5 mg/kg, i.p.), a 5-HT1B agonist, blocked the reversal effect of isamoltan on Fos expression. Fos expression was not changed in LETO rats by pretreatment with isamoltan (3 mg/kg, i.p.). The Fos expression in LETO and OLETF rats was significantly decreased by pretreatment with the 5-HT1A antagonist, WAY-100,635. Phase shifts in locomotor activity paralleled the Fos expression. Light-induced phase shifts of locomotor activity in OLETF rats were significantly smaller than those in LETO rats. The phase shifts were significantly increased by isamoltan (3 mg/kg, i.p.) in OLETF rats. These results suggest that 5-HT1B receptors are involved in the reduced entrainment function of OLETF rats.  相似文献   
40.
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