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   5145篇
  免费   304篇
  国内免费   17篇
耳鼻咽喉   58篇
儿科学   139篇
妇产科学   96篇
基础医学   721篇
口腔科学   118篇
临床医学   400篇
内科学   1246篇
皮肤病学   149篇
神经病学   421篇
特种医学   250篇
外科学   661篇
综合类   11篇
一般理论   1篇
预防医学   244篇
眼科学   60篇
药学   415篇
中国医学   4篇
肿瘤学   472篇
  2023年   32篇
  2022年   58篇
  2021年   78篇
  2020年   60篇
  2019年   84篇
  2018年   100篇
  2017年   90篇
  2016年   99篇
  2015年   100篇
  2014年   140篇
  2013年   157篇
  2012年   303篇
  2011年   345篇
  2010年   207篇
  2009年   172篇
  2008年   302篇
  2007年   340篇
  2006年   309篇
  2005年   334篇
  2004年   258篇
  2003年   285篇
  2002年   269篇
  2001年   84篇
  2000年   105篇
  1999年   98篇
  1998年   83篇
  1997年   50篇
  1996年   50篇
  1995年   39篇
  1994年   31篇
  1993年   39篇
  1992年   69篇
  1991年   58篇
  1990年   63篇
  1989年   48篇
  1988年   31篇
  1987年   42篇
  1986年   37篇
  1985年   47篇
  1984年   51篇
  1983年   40篇
  1982年   21篇
  1981年   24篇
  1980年   25篇
  1979年   28篇
  1978年   32篇
  1977年   22篇
  1974年   15篇
  1973年   14篇
  1970年   12篇
排序方式: 共有5466条查询结果,搜索用时 78 毫秒
61.
The effect of a new antitumor antibiotic on the fertility was studied using SD rats. (2"R)-4'-O-Tetrahydropyranyladriamycin (THP) was administered to each rat at 0.01, 0.03 or 0.1 mg/kg daily. Males were given the drug intravenously for 63 days prior to mating and during the mating period; females were given the drug intravenously from 14 days prior to mating until day 7 of pregnancy. All the pregnant rats were sacrificed on day 20 of pregnancy, followed by external, visceral and skeletal observations of their fetuses. Results were summarized as follows. THP, at 0.1 mg/kg, suppressed body weight gain in females during the late period of pregnancy but did not affect body weight gain in males. THP, at 0.1 mg/kg, increased the numbers of dead fetuses and of resorptions. It caused no external, visceral or skeletal anomalies at any dose levels. The results suggest that, in rats, the maximum "no effect" dose of THP is 0.03 mg/kg/day intravenously regarding fertility and fetal development.  相似文献   
62.
During the coronavirus disease 2019 (COVID-19) pandemic, autopsies have provided valuable insights into the pathogenesis of COVID-19. The precise effect of this pandemic on autopsy procedures in Japan, especially in instances unrelated to COVID-19, has not yet been established. Therefore, we conducted a questionnaire survey from December 2020 to January 2021 regarding the status of pathological autopsy practices in Japan during the first year of the COVID-19 pandemic. The questionnaire was sent to 678 medical facilities with pathologists, of which 227 responded. In cases where a confirmed diagnosis of COVID-19 was not made at the time of autopsy, many facilities counted them as suspected COVID-19 cases if pneumonia was suspected clinically. At around half of the sites, autopsies were prohibited for suspected COVID-19 cases. In addition, the number of autopsies of non-COVID-19 cases during the pandemic period was also investigated, and a significant decrease was observed compared with the incidence in the pre-pandemic period. The COVID-19 pandemic has affected not only the autopsies of COVID-19 cases but also the entire practice of pathological autopsies. It is necessary to establish a system that supports the implementation of pathological autopsy practices during the pandemic of an emerging infectious disease.  相似文献   
63.
PURPOSE: To investigate the interrelationships between the bronchial and pulmonary circulations including the existence of precapillary bronchopulmonary arterial anastomoses. MATERIAL AND METHODS: CT of bronchial arteriography (BAG-CT) was performed in 10 patients and BAG-CT during a pulmonary artery block test (PA-block) in 5 patients with lung cancer. Bronchial and pulmonary circulations were evaluated in 5 autopsied normal lungs by injecting silicone rubber with different colors into the bronchial and pulmonary arteries. RESULTS: BAG-CT correlated well with the findings at silicone rubber injection into lung autopsy samples. BAG-CT demonstrated inflow of contrast medium into the pulmonary artery during PA-block in all cases, while no inflow was observed before and following reversal of PA-block. Mixed silicone rubber was observed in the lobar to subsubsegmental bronchial arteries in all cases and in the subsubsegmental pulmonary artery in one case. CONCLUSION: Precapillary bronchopulmonary arterial anastomoses may exist at the level of the lobar bronchi to the periphery. If either the pulmonary or bronchial circulation is disturbed, flow occurs inside the anastomoses to supplement the other flow, especially flow from the bronchial to the pulmonary arteries via the anastomoses, which occurs within 30 min.  相似文献   
64.
Endovascular treatment of intracranial aneurysms using plantinum coils was performed in 10 patients over 80 years of age. The patients ranged in age from 81 to 96 years. Preoperative Hunt and Kosnik grading revealed one patient in grade I, 4 in grade II, 3 in grade III, and 2 in grade IV. The aneurysms were located in the internal carotid artery in 6 patients, in the anterior communicating artery in 1, and in the middle cerebral artery in 3 respectively. Intra-aneurysmal occlusion was accomplished in 8 patients with total or subtotal occlusion in 6 and partial occlusion in 2. In one patient with a peripheral middle cerebral artery aneurysm, the parent artery was occluded just proximal to the aneurysm. In the remaining one patient in grade III, an aneurysm associated with wide neck could not be occluded because of coil protrusion into the parent artery. In 9 patients who were successfully treated, all five patients in grade I or II and one in grade III resulted in good outcome, but the other three patients in grade III and IV showed poor outcome. No evidence of recurrent hemorrhage was noted during the follow-up period ranging from 2 months to 4 years. Endovascular coil embolization is a useful therapeutic alternative for treating ruptured intracranial aneurysms in patients over 80 years of age, especially those in Grade I or II.  相似文献   
65.
Four new antibiotics, TMC-171A (2), B (3), C (4) and TMC-154 (5) have been isolated from the fermentation of fungal strains Gliocladium sp. TC 1304 and TC 1282, respectively. Spectroscopic and degradation studies have shown that TMC-171s and TMC-154 were new members of the TMC-151 class of antibiotics, unique polyketides modified with a D-mannose and a D-mannitol or a D-arabitol. These compounds showed moderate cytotoxicity to various tumor cell lines.  相似文献   
66.
Blood pressure responses to lycorenine were investigated in rats and dogs. Lycorenine (10--40 mg/kg p.o.) produced a decrease in blood pressure in conscious rats which was greater in hypertensive rats than in normotensive rats. In conscious dogs, lycorenine (5 or 10 mg/kg i.v.) produced rises in blood pressure and heart rate except for a few instances, while it produced a decrease in blood pressure in pentobarbital anesthetized dogs. Thus, there are species differences in cardiovascular effects of lycorenine between conscious rats and dogs. The development of tachyphylaxis to the vasodepressor actions of lycorenine and its related compounds was related to their alpha-adrenergic blocking activities at the time of the second injection in anesthetized rats. Desipramine which abolished or diminished the development of tachyphylaxis to the vasodepressor action of lycorenine (5 or 7.5 mg/kg i.v.), shortened the duration of its vasodepressor action and reduced its alpha-adrenergic blocking action. These results indicate that the development of tachyphylaxis to the vasodepressor action of lycorenine is ascribed to maintenance of its alpha-adrenergic blocking action.  相似文献   
67.
E1 mice had higher levels of brain dopamine (DA) and serotonin (5-HT) and a lower level of brain norepinephrine (NE) compared with the other strains of inbred mice. In the interictal stage of "stimulated" E1 mouse, the brain DA, NE and 5-HT levels were significantly lower compared with the non-stimulated E1 mouse. The administration of 5-hydroxytryptophan with MK486 markedly depressed the incidence of seizures in the E1 mouse. Evidence of abnormal DA, NE and 5-HT metabolism was found at the development age when the seizures became frequent. These results show that 5-HT may be closely related to the E1 mouse seizure susceptibility.  相似文献   
68.
PURPOSE: The aim of this study was to determine whether collagen XVIII expression is correlated with circulating serum endostatin and whether this has any prognostic value in patients with non-small cell lung cancer (NSCLC). EXPERIMENTAL DESIGN: Serum endostatin levels were measured quantitatively by a competitive enzyme immunoassay, and collagen XVIII expression in tumor tissue was investigated with an immunohistochemical method in a series of 94 patients who underwent surgery for NSCLC. RESULTS: Sixty cases (63.8%) had positive immunohistochemical staining with anticollagen XVIII polyclonal antibodies, including strongly positive staining in 11 (11.7%) cases. The mean (+/- SD) serum endostatin level was 41.6 +/- 34.4 ng/ml in the patient group and 16.3 +/- 10.3 ng/ml in the control group (P < 0.0001). The 11 cases who were strongly collagen XVIII-positive had significantly higher serum endostatin levels than the cases who were negative or weakly positive (P = 0.0297). The 5-year survival rates of negative, weakly positive, and strongly positive patients were 77.8%, 56.9%, and 43.8%, respectively. The cases with strongly positive collagen XVIII expression had a significantly poorer outcome than cases with negative expression (P = 0.0027). A multivariate analysis with Cox proportional hazards model for disease-specific survival revealed that expression of collagen XVIII (strongly positive versus negative; weakly positive versus negative), tumor classification, and regional lymph node classification were independent prognostic factors. CONCLUSIONS: Our results suggest that expression of collagen XVIII in tumor tissue is strongly associated with a poorer outcome in NSCLC and correlates with elevated levels of circulating serum endostatin.  相似文献   
69.
We report a case of a long-term survivor with malignant melanoma of the anus who did not undergo radical surgery. A 71-year-old woman who presented with anal bleeding and anal tumor underwent an excisional biopsy in September 1985. The biopsy specimen was a lobulated, polypoid, pigmented mass 2 cm in diameter, that had been located on the anterior wall of the anus. A satellite nodule 7 mm in diameter was found on the left wall of the anus at the level of the dentate line. Both tumors were histologically diagnosed as malignant melanoma. The primary tumor was 6 mm thick. Melanoma cells were present microscopically at the cut end of the rectum. Because of her history of ischemic heart disease, the patient rejected our recommendation that she undergo radical surgery, and received 10 courses of carboplatin 20 mg intramuscularly and OK-432 10 K.E. (Klinische Einheit) intradermally every week. A single, pigmented metastatic inguinal lymph node developed and was excised in June 1987. A recurrent tumor was detected in the rectum in October 1992, so again we recommended radical surgery. The patient rejected radical surgery again, and received 12 courses of carboplatin 10 mg intramuscularly every 2 weeks. She died of disease at home in July 1993 after surviving for 7 years and 10 months. An autopsy was not performed. This case shows that local excision of the primary lesion may be appropriate to preserve the quality of life of patients with early-stage malignant melanoma of the anus.  相似文献   
70.
Social skill deficits in schizophrenia profoundly affect patients' life-long outcome, although the profile of the underlying cognitive dysfunction still remains a matter of debate. In the present study, we investigated the relationship between social skills and event-related potentials (ERPs) in an auditory selective attention task, in addition to the neurocognitive indices obtained from the degraded-stimulus continuous performance test (CPT) and clinical indices, such as Brief Psychiatric Rating Scale (BRPS) and global assessment of function (GAF) scores. Social skills were assessed using a Japanese version of the structured role play test. Fourteen persons with schizophrenia participated in the study. Non-verbal skills showed a positive correlation with GAF, the performance level, N1 and N2b amplitude in the ERP task, and hit rate in the CPT, and a negative correlation with reaction time in the CPT. Verbal communication skills showed a positive correlation with GAF, the performance level and N2b amplitude in the ERP task, and hit rate in the CPT, and a negative correlation with reaction time in the CPT. Processing skills showed a positive correlation with the performance level and N1 amplitude in the ERP task and a negative correlation with reaction time in the CPT. These findings suggested that the social skill deficits of persons with schizophrenia were related to the vigilance level and controlled stimulus detection processing.  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