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   9095篇
  免费   442篇
  国内免费   61篇
耳鼻咽喉   79篇
儿科学   184篇
妇产科学   75篇
基础医学   1170篇
口腔科学   116篇
临床医学   518篇
内科学   2802篇
皮肤病学   75篇
神经病学   680篇
特种医学   377篇
外科学   1547篇
综合类   23篇
一般理论   1篇
预防医学   279篇
眼科学   90篇
药学   528篇
中国医学   43篇
肿瘤学   1011篇
  2023年   58篇
  2022年   113篇
  2021年   153篇
  2020年   102篇
  2019年   164篇
  2018年   177篇
  2017年   141篇
  2016年   189篇
  2015年   167篇
  2014年   227篇
  2013年   303篇
  2012年   476篇
  2011年   544篇
  2010年   289篇
  2009年   260篇
  2008年   438篇
  2007年   506篇
  2006年   492篇
  2005年   591篇
  2004年   564篇
  2003年   594篇
  2002年   609篇
  2001年   160篇
  2000年   138篇
  1999年   162篇
  1998年   163篇
  1997年   123篇
  1996年   109篇
  1995年   106篇
  1994年   111篇
  1993年   111篇
  1992年   139篇
  1991年   116篇
  1990年   126篇
  1989年   100篇
  1988年   103篇
  1987年   101篇
  1986年   81篇
  1985年   69篇
  1984年   64篇
  1983年   49篇
  1982年   31篇
  1981年   23篇
  1980年   27篇
  1979年   27篇
  1978年   21篇
  1975年   18篇
  1974年   25篇
  1973年   17篇
  1971年   19篇
排序方式: 共有9598条查询结果,搜索用时 15 毫秒
41.
42.
Background. A membrane oxygenator consisting of a microporous polypropylene hollow fiber with a 0.2-μm ultrathin silicone layer (cyclosiloxane) was developed. Animal experimental and preliminary clinical studies evaluated its reliability in bypass procedures.

Methods. Five 24-hour venoarterial bypass periods were conducted on dogs using the oxygenator (group A). In 5 controls, bypass periods were conducted using the same oxygenator without silicone coating (group B). As a preliminary clinical study, 14 patients underwent cardiopulmonary bypass with the silicone-coated oxygenator.

Results. Eight to 16 hours (mean, 12.2 hours) after initiation of bypass, plasma leakage occurred in all group B animals, but none in group A. The O2 and CO2 transfer rates after 24 hours in group A were significantly higher than at termination of bypass in group B (p < 0.005 and p < 0.03, respectively). Scanning electron microscopy of silicone-coated fibers after 24 hours of bypass revealed no damage to the silicone coating of the polypropylene hollow fibers. In the clinical study, the oxygenator showed good gas transfer, acceptable pressure loss, low hemolysis, and good durability.

Conclusions. This oxygenator is more durable and offers greater gas transfer capabilities than the previous generation of oxygenators.  相似文献   

43.
p = 0.0007) and tumor necrosis (TN) (HMC: p = 0.0050). Univariate analysis showed that AMC or HMC was a statistically significant predictor of overall survival in all patients ( p = 0.0086 and p = 0.0307, respectively). Multivariate analysis showed that AMC was an independent predictor of node status when we fitted a model with node status, BVI, and either AMC or HMC; but HMC was not independent. However, when we fitted a model including all 11 of the other indicators and AMC or HMC, the node status, HG, and LI were independent predictors, but AMC and HMC were not. Although AMC was a better method than HMC for evaluating angiogenesis, we cannot confirm angiogenesis as a significant independent prognostic factor associated with long-term survival in Japanese breast cancer patients.  相似文献   
44.
Here, we present the first report of the molecular cloning of zebrafish protocadherin 10 (Pcdh10, OL-protocadherin) and describe its functional analyses in the development of segmental plate. Epitope-tagged Pcdh10 expressed in embryos was localized on cell peripheries of adjacent cells. In situ hybridization showed that pcdh10 was expressed in the paraxial mesoderm (PAM) and developing somites, and in the pineal body, the diencephalon, and the vicinity of otocysts. Expression in PAM increased in the last few presumptive somites, reached the maximum level in the latest segmenting somites, and decreased thereafter during somite maturation. These expression patterns suggested that Pcdh10 is involved in development of PAM and somites. This was confirmed by morpholino knockdown and dominant-negative inhibition of Pcdh10 in embryos, which disturbed movements of PAM cells and somite segmentation. Comparative studies showed that pcdh10 expression lasted up to approximately three times longer in maturing somites than that of paraxial protocadherin (pcdh8). They also indicated that the adaxial cells expressed pcdh8 but not pcdh10. We propose that Pcdh10 is involved in the morphogenic movements of PAM cells and somite segmentation and that differential adhesion of Pcdh8 and Pcdh10 plays a role in the morphogenic machinery of somites and adaxial cells.  相似文献   
45.
SUMMARY: A comparative immunohistological study was performed for the glomerular deposition of complements (C1q and C3c), fibrin/fibrinogen‐related antigen (FRA), the expression of intercellular adhesion molecule‐1 (ICAM‐1), and the infiltration of leucocytes bearing β2 integrins (leucocyte function associated antigen‐1 (LFA‐1), complement receptor 3 (CR3) and complement receptor 4 (CR4)) on renal biopsy specimens from 49 cases with Henoch‐Schoenlein purpura nephritis (HSPN), and 49 age‐matched cases with immunoglobulin A nephropathy (IgAN). the glomerular expression of ICAM‐1 was signifcantly correlated with the glomerular infiltration of leucocyte function associated antigen (LFA)‐1+ leucocytes in both diseases, and with that of CR3+ leucocytes in HSPN. the expression of ICAM‐1 was closely localized with the infiltration of LFA‐1+ leucocytes in the study with double immunostaining. the incidence and intensity of glomerular deposition of FRA were significantly higher in HSPN than in IgAN (P< 0.001), and those of C3c were significantly lower in HSPN than in IgAN (P< 0.001). the glomerular deposition of FRA was significantly correlated with the glomerular infiltration of CR4+ leucocytes in HSPN (P<0.05) but not in IgAN. In contrast, the glomerular deposition of C3c was significantly correlated with the glomerular infiltration of CR4+ leucocytes in IgAN (P<0.05), but not in HSPN. Studies with double immunostaining revealed a close association of CR4+ leucocytes with FRA deposition in HSPN and with C3c deposition in IgAN, respectively. the number of glomerular leucocytes bearing β2 integrins was significantly correlated with urinary protein at the time of renal biopsy in both diseases. These results suggested the differential roles of β2 integrins in the induction of glomerular injury in HSPN and IgAN. the ICAM‐1/LFA‐1 interaction may commonly be involved in the glomerular infiltration of leucocytes in both diseases. the ICAM‐1/CR3 interaction may be involved only in HSPN. Complement receptor 4 may function as a fibrin/fibrinogen receptor in HSPN, while CR4 may function as a complement receptor in IgAN.  相似文献   
46.
Transabdominal resection for esophagocardial cancer and reestablishment of alimentary continuity using bypass methods were performed in 76 patients. Thirteen underwent a bypass with a gastric tube and in 30, a colonic segment was prepared. In the remaining 33, a jejunal segment was used as a bypass organ, with considerable success. The 5 year survival rates were 68.8 per cent in those with stages (I+II), 16.5 per cent in those with stage III, 12.6 per cent in those with stage IV and 22.5 per cent in all cases, indicating similar results compared to those with cancer located in the upper third of the stomach with the limited proximal extension within the esophagocardial junction and operated on during the same period.  相似文献   
47.
48.
We report a metastatic pulmonary tumor resected by video-assisted thoracoscopic surgery. A 63-year-old female was found to have four nodules of hepatocellular carcinoma (HCC) in January 1991; after non-surgical treatment, the tumors had become necrotic. In June 1992, a new HCC nodule was found. After infusion chemotherapy, it became necrotic. In September 1993, a solitary lung tumor, 2.4 cm in diameter, appeared at the periphery of the right lung. Because the tumor was considered to be a metastatic HCC rather than a primary lung cancer, it was removed by thoracoscopic wedge resection. Although whether metastasectomy contributes to prolongation of survival is still controversial, thoracoscopic pulmonary resection may be indicated for solitary peripheral metastasis, if the primary HCC is well controlled by multidisciplinary treatment.  相似文献   
49.
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   
50.
Key words  intractable pain - celiac plexus neurolysis - ultrasonography  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