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   35853篇
  免费   1726篇
  国内免费   304篇
耳鼻咽喉   267篇
儿科学   652篇
妇产科学   414篇
基础医学   4799篇
口腔科学   1003篇
临床医学   2056篇
内科学   8832篇
皮肤病学   853篇
神经病学   2515篇
特种医学   1259篇
外科学   6570篇
综合类   134篇
一般理论   1篇
预防医学   953篇
眼科学   630篇
药学   2091篇
中国医学   123篇
肿瘤学   4731篇
  2023年   182篇
  2022年   157篇
  2021年   872篇
  2020年   451篇
  2019年   648篇
  2018年   848篇
  2017年   660篇
  2016年   779篇
  2015年   804篇
  2014年   1084篇
  2013年   1378篇
  2012年   2238篇
  2011年   2621篇
  2010年   1479篇
  2009年   1220篇
  2008年   2236篇
  2007年   2468篇
  2006年   2308篇
  2005年   2485篇
  2004年   2399篇
  2003年   2409篇
  2002年   2420篇
  2001年   374篇
  2000年   329篇
  1999年   454篇
  1998年   587篇
  1997年   458篇
  1996年   434篇
  1995年   371篇
  1994年   327篇
  1993年   298篇
  1992年   220篇
  1991年   201篇
  1990年   190篇
  1989年   178篇
  1988年   158篇
  1987年   129篇
  1986年   108篇
  1985年   102篇
  1984年   112篇
  1983年   87篇
  1982年   73篇
  1981年   88篇
  1980年   82篇
  1979年   66篇
  1978年   46篇
  1977年   34篇
  1976年   25篇
  1975年   25篇
  1973年   25篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
71.
We describe a case of type B aortic dissection with large ascending aortic aneurysm occurring 12.8 years after aortic root replacement (Cabrol procedure) in a non-Marfan patient with cystic medial necrosis of the aorta. We have successfully performed an extended total aortic arch replacement using a four-branched graft through the “L-indsion” approach (a combination of a left anterior thoracotomy and upper half median sternotomy). Of note, a histological specimen from the aneurysmal ascending aortic wall revealed “healed aortic dissection” with fibrous tissue replacing the media and intima in addition to multiple foci of cystic medial necrosis.  相似文献   
72.
The roles of glutathione (GSH), cysteine, vitamin C., liposome-encapsulated superoxide dismutase (L-SOD) and vitamin E in preventing oxidative DNA damage and cytotoxicity in the rat kidney after administration of potassium bromate (KBrO3) to male F344 rats were investigated by measuring 8-hydroxydeoxyguanosine (8-OH-dG), an oxidative DNA product, lipid peroxidation (LPO) levels and relative kidney weight (RKW). Combined pre- and posttreatment of animals with 2 × 800 mg/kg GSH i.p. inhibited the increase of 8-OH-dG, LPO levels and RKW caused by 80 mg/kg KBrO3 i.p. administration. In contrast, pretreatment with 0.3 ml/kg diethylmaleate (DEM) i.p., a depletor of tissue GSH, was associated with elevation of 8-OH-dG, LPO levels and RKW after a 20 mg/kg KBrO3 i.p. treatment, which itself caused no change. Administration of KBrO3 itself reduced renal non-protein thiol levels, but this was inhibited by the two doses of exogenous GSH. Combined treatment with DEM and KBrO3 lowered the non-protein thiol level in the kidney more than did DEM treatment alone. Protective effects against the oxidative damage caused by KBrO3 were also observed for pre- and posttreatment with 400 mg/kg cysteine i.p., another sulfhydryl compound, and daily i.g. application of 200 mg/kg vitamin C for 5 days. However, no influence was evident after pre- and posttreatment with 18,000 U/kg L-SOD i.p. or daily i.g. 100 mg/kg of vitamin E for 5 days. The results suggest that intracellular GSH plays an essential protective role against renal oxidative DNA damage and nephrotoxicity caused by KBrO3.  相似文献   
73.
Four patients with untreated renal tubular acidosis had a urinary excretion of low-molecular-weight (LMW) proteins which was restored to normal by alkali therapy. Hypokalaemic proximal tubular damage in untreated patients with distal renal tubular acidosis is believed to be the cause of LMW proteinuria. An examination of urinary excretion of LMW proteins is useful for determining hypokalaemic proximal tubular dysfunction, as well as the efficiency of alkali therapy.  相似文献   
74.
This report presents the effect of repeated heating every 24 hrs using bleomycin (BLM) which, although seemingly contrary to the usual agreement that hyperthermia should be carried out with a long interval due to thermotolerance, holds many possibilities. FM3A cells on the foot pad of C3H mouse were immersed in a heated water bath at 43 and 44°C for 30 min. The effect of repeated heating was appreciated by an improved growth curve and 50 day survival compared to mice which received heating twice with a 96-hr interval. Repeated heating every 24 hrs 5 times with BLM suppressed tumor growth significantly as compared to heating twice with a 96-hr interval without BLM. The longest survival time was obtained by the repeated heating with BLM among all protocols. There is therefore a good possibility that more effective results could be obtained clinically by repeated heating over a short period.  相似文献   
75.
Lewis Y (Ley) antigen, a difucosylated tetrasaccharide found on type 2 blood group oligosaccharides of glycolipids and glycoproteins, is thought to be a phenotypic marker predictive of cell differentiation. The distribution of this antigen in human anagen hair follicles was examined by immunohistochemical staining using a monoclonal antibody (AH-6) to Ley. In the bulbar and suprabulbar portion of anagen hair follicles, Ley antigen was detected in the three layers of the inner root sheath. Subsequently, the positive staining became translocated to the innermost layer of the outer root sheath in the middle part of the hair follicles. In the upper portion of the hair follicles, Ley antigen was found in the outer cells of the outer root sheath. These findings suggested that the expression of Ley antigen in the anagen hair follicles was correlated with the processes of keratinization or terminal differentiation.  相似文献   
76.
To evaluate clinical and pathological factors present at the initial consultation which affect disease progression, we reviewed data from 223 patients with superficial bladder cancer (pTa and pT1) who were initially treated at Nagoya University Hospital between January 1973 and December 1987. The factors included in the present analysis were age, sex, symptoms, interval between initial symptoms and first consultation, location of tumor, size, number, endoscopic shape, histological pattern of growth, grade and stage. The median duration of the follow-up after initial treatment was 46 months. Of the 223 patients, 17 died: 8 (3.6%) of bladder cancer and the remaining 9 (4.0%) of unrelated causes. Disease progression developed in 12 patients (5.4%): muscle invasion of the bladder wall in 11 and lung metastasis in one. The interval between initial treatment and progression ranged from 4 to 108 months, with a median of 11.5 months. Of the 12 patients, 9 (75%) had disease progression within 2 years. Progression was significantly associated with poor prognosis (p less than 0.001): the 5-year actuarial survival rates were 47.1% and 92.8% in patients with and without progression, respectively. Univariate analysis by Cox's proportional hazards model demonstrated that characteristics such as irritative bladder symptoms, higher-grade tumors, invasion into lamina propria, and nonpapillary growth seen at initial consultation were significantly related to disease progression. Cox's proportional hazards model produced hazard ratios of 10.2 in irritative bladder symptoms (yes vs. no), 6.3 in histological grade (grade 3 vs. grades 0-2), 4.9 in stage (pT1 vs. pTa), and 4.7 in pattern of growth (papillary vs. nonpapillary).(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
77.
Design of a Centrifugal Blood Pump with Magnetic Suspension   总被引:1,自引:0,他引:1  
Abstract: A new concept blood pump, whose impeller is suspended by permanent magnets and a mechanical pivot without seals or ball bearings, is presented in this paper. The primary aim of the blood pump is an application to implantable artificial hearts. The prototype model is of a centrifugal type with a four-vaned semiopen impeller 50 mm in diameter. Since this mechanism has no seals or ball bearings, flow stagnation or heat generation that might cause blood cell denaturation is expected to be small. The results of performance testing for the prototype model 2 were satisfactory regarding pump head and efficiency. The radial-suspension magnets and the magnetic coupling were stable. As a result, the present mechanism has been verified to be a candidate applicable to implantable artificial hearts.  相似文献   
78.
Low-dose γ-irradiation of mouse embryonic fibroblast C3D2F1 3T3-a cells caused Gl arrest along with G2 arrest and inhibition of replicative DNA synthesis. When the cells were cultured in the presence of inhibitors of poly(ADP-ribose) polymerase [EC 2.4.2.30], such as 3-aminobenzamide, benzamide and luminol, Gl arrest of C3D2F1 3T3-a cells was suppressed and enhancement of G2 arrest was observed. In contrast, 3-aminobenzoic acid, a non-inhibitory analog of 3-aminobenzamide, did not suppress Gl arrest following γ-irradiation. These results suggest that the poly(ADP-ribosyDation reaction is critical for the pathway of Gl arrest and is also involved in the pathway of G2 arrest.  相似文献   
79.
Because gastric cancers located in the upper third of the stomach are difficult to detect at an early stage, the surgical results remain poor. We performed R4 gastrectomy as a radical procedure for 25 patients, involving complete resection of the latero-aortic and interaorticovenous lymph modes above and below the left renal vein, in combination with the ordinary R2 or R3 gastrectomy (the R4 group). These patients were compared with 156 others who underwent R2 gastrectomy alone (the R2 group). There were no significant differences in operation time, blood loss, or the incidence of complications between the two groups; however, when the survival rates of the patients with tumors invading beyond the subserosa were compared, the 5-year survival rate was found to be significantly higher in the R4 group than in the R2 group. Furthermore, in patients with para-aortic nodal involvement, a significant survival advantage was observed in the R4 group, as compared with the R2 group. These results suggest that the R4 gastrectomy is a rational approach for patients with advanced gastric cancer located in the upper third of the stomach.  相似文献   
80.
Magnetic resonance cholangiopancreatography (MRCP) was performed in 35 patients to evaluate the feasibility of its use as a postsurgical imaging technique after resection of the pancreas. The surgical procedures performed were: pancreatoduodenectomy in 22 patients, segmental pancreatectomy in 1, distal pancreatectomy in 7, and pyroluspreserving pancreatoduodenectomy in 5. The pancreatic duct was shown in its entirety in 24 of the 35 patients (68.6%) and was partially visualized in 8 patients (22.9%), but the intrahepatic and extrahepatic bile ducts were visualized completely in all patients. Furthermore, MRCP was able to demonstrate lesions in 3 of 6 patients who had shown clinical evidence of recurrence. The visualization of the pancreatic and bile duct system was satisfactory despite anatomical changes brought about by resection of the pancreas. Thus, we conclude that MRCP is an appropriate follow-up screening test for patients with suspected abnormalities of the biliary and pancreatic duct system.  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