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   22248篇
  免费   1506篇
  国内免费   240篇
耳鼻咽喉   377篇
儿科学   319篇
妇产科学   297篇
基础医学   3800篇
口腔科学   391篇
临床医学   1862篇
内科学   4359篇
皮肤病学   735篇
神经病学   1918篇
特种医学   1180篇
外科学   3047篇
综合类   92篇
一般理论   4篇
预防医学   797篇
眼科学   483篇
药学   2130篇
中国医学   295篇
肿瘤学   1908篇
  2023年   143篇
  2022年   99篇
  2021年   824篇
  2020年   424篇
  2019年   593篇
  2018年   690篇
  2017年   524篇
  2016年   793篇
  2015年   1010篇
  2014年   1152篇
  2013年   1369篇
  2012年   2026篇
  2011年   1942篇
  2010年   1119篇
  2009年   912篇
  2008年   1408篇
  2007年   1315篇
  2006年   1214篇
  2005年   1103篇
  2004年   953篇
  2003年   831篇
  2002年   725篇
  2001年   427篇
  2000年   403篇
  1999年   342篇
  1998年   158篇
  1997年   124篇
  1996年   114篇
  1995年   100篇
  1994年   81篇
  1993年   78篇
  1992年   106篇
  1991年   104篇
  1990年   80篇
  1989年   81篇
  1988年   80篇
  1987年   68篇
  1986年   51篇
  1985年   52篇
  1984年   35篇
  1983年   41篇
  1982年   28篇
  1981年   19篇
  1980年   26篇
  1979年   40篇
  1978年   20篇
  1977年   15篇
  1976年   16篇
  1972年   15篇
  1969年   15篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
Rat astrocytes, immunologically competent glial cells of the central nervous system (CNS), released a variety of cytokines after activation. Lipopolysaccharide-stimulated astrocytes produced tumor necrosis factor (TNF) as demonstrated by Northern blot analysis using a mouse TNF probe and by functional assay. Biological activity of rat astrocyte-derived TNF was neutralized by rabbit antiserum against recombinant murine TNF. Stimulation of astrocytes by lipopolysaccharide also activated the interleukin 1 and interleukin 6 genes. We have also investigated whether a neurotropic paramyxovirus, Newcastle disease virus, triggers cytokine production by astrocytes. This virus induced astrocytes to produce TNF, lymphotoxin, interleukin 6, and alpha- and beta-interferons. Thus, stimulation by endotoxin and virus activated distinct, yet overlapping, sets of cytokine genes. We propose that astrocytes and the cytokines they produce may play a significant role in the pathogenesis of immunologically and/or virally mediated CNS disease, in CNS intercellular communication, and in the interactions between the nervous and immune systems.  相似文献   
52.
The reconstruction of large bone and joint defects after the resection of malignant tumors remains a major challenge. Chemotherapy has significantly lowered the risk of metastasic disease, but complications associated with reconstructive techniques continue to result in late morbidity. In the present study, biomechanical torsion testing, gait analysis, and histomorphometric and scanning electron microscopic evaluations of 24 dogs were used to examine the effects of preoperative and postoperative administration of cisplatin on the biologic fixation of a porous-coated segmental replacement prosthesis. The chemotherapy consisted of four cycles of cisplatin administered at a dosage of 75 mg/m:2 preoperatively or postoperatively. The healing was enhanced by use of an autogenous corticocancellous bone graft. The graft was placed evenly around the prosthesis and the adjacent femoral cortex. Mechanical analyses of torsional stiffness, yield strength, and maximum strength revealed no statistically significant differences between the groups at 12 weeks. Such lack of difference was mainly due to the penetration of highly organized fibrous tissue into the porous surface; this provided strong fixation of the implant to bone even in the absence of bone ingrowth. Although bone ingrowth into the prostheses was not affected, electron microscopic, histomorphometric, and radiologic analyses showed a clear difference in the formation of new bone around the prosthesis. Preoperative chemotherapy did not alter the formation of new bone, but specimens from animals treated postoperatively with cisplatin showed significantly less bone graft resorption and less new bone formation. Hence, the effect of cisplatin administration caused only a temporary delay, not a permanent effect, on extracortical capsule formation. The formation of extracortical bone and soft tissue might prevent debris-incised osteolysis and, therefore, prevent late complications by forming a tight capsule around the bone-prosthetic interface.  相似文献   
53.
Immunoscintigraphy with radiolabelled monoclonal antibodies is widely used to detect solid tumours, but only a few trials have been carried out concerning the specific in vivo localization of an inflammatory process. The purpose of this study was to investigate the detectability of tuberculous foci utilizing this method with radiolabelled bacillus Calmette-Guérin (BCG)-specific F(ab')2 in rabbits. All of the tuberculous lesions (n = 8) were clearly visualized on serial scintigraphy for up to 48 h after injection of the antibody. Immunohistochemical and Ziel-Neelson staining of the tuberculous lesions confirmed the presence of the tuberculous antigens and bacilli. It failed to demonstrate any sustained retention of the BCG-specific antibody fragment in the control group with syphilitic orchitis (n = 2). Therefore, the specific in vivo localization of tuberculosis is feasible by immunoscintigraphy.  相似文献   
54.
We considered performing living donor liver transplantation (LDLT) in a larger-size recipient. When the recipient was large-sized, or when the donor liver was severely steatotic or had a right-to-left volume discrepancy. We devised dual living donor liver transplantation (DLDLT) to make up for graft size insufficiency and to secure the donor's safety. However, portal vein thrombosis (PVT) presented a challenge for DLDLT because of the need for intact right and left portal veins for the implantation of both liver grafts. Our 52-year-old male patient with hepatitis B cirrhosis had suffered from repeated esophageal and gastric variceal bleeding and underwent 2 trials of a transjugular intrahepatic portosystemic shunt (TIPS). He developed TIPS occlusion and PVT involving the area just above the spleno-mesenteric confluence to the right and left PV. Also, the right PV orifice was destructed and difficult to isolate because of severe periportal inflammation and neointima growth in the TIPS mesh. The patient's two sons were inadequate for donation because of right-to-left volume discrepancy. Therefore, DLDLT using 2 left lobes was necessary to compensate for graft-size insufficiency and to secure donor safety, and we substituted an intact umbilical portion of recipient's left PV for the destroyed right PV. The patient recovered well, and liver function has been normal for more than a year. In conclusion, the umbilical portion of recipient's left PV can be a useful vascular substitute for the reconstruction of a thrombosed main portal branch in DLDLT.  相似文献   
55.
We present a case of benign osteoblastoma of the occipital bone. Benign osteoblastoma is an uncommon primary bone tumor, which usually involves the vertebrae and the long bones. This tumor rarely develops in the calvaria, showing a preference for the temporal and frontal bones when it does. To the best of our knowledge, this case is only the eighth reported case of benign osteoblastoma confined to the occipital bone. A 20‐year‐old male presented with a mild tender mass lesion of the occipital area, just below the lambda. Plain X‐ray films and CT scans demonstrated an osteolytic mass surrounded by the sclerotic rim within the diploic space. MRI proved to be effective for the evaluation of the intracranial and intraosseous extensions of the tumor. However, it was very difficult to formulate a differential diagnosis against other osteoblastic tumors, or osteoid osteoma, in view of its radiological appearance. The final diagnosis was obtained by careful consideration of the histopathological characteristics of the tumor combined with its clinical and radiological features. Although generally regarded as benign, a complete resection is preferred over conventional curettage as this can guard against possible recurrence and malignant transformation.  相似文献   
56.
The pharmacokinetics of oral Alminoprofen, a nonsteroidal anti-inflammatory drug, were studied in five elderly patients with rheumatoid arthritis and spondylosis deformans after 200 mg (three times a day) repeated dose for 5 days. The pharmacokinetic parameters after oral administration of Alminoprofen were analyzed by the one-compartment open model method. The maximum plasma concentrations (Cmax) were 16.1 +/- 2.5 micrograms/ml, after dosing on day 1, 25.2 +/- 1.6 micrograms/ml on day 3 and 21.6 +/- 2.7 micrograms/ml on day 5. The maximum time (Tmax) were about 2 hours after the medication in al cases. The area under the curve in drug concentration in plasma versus time (AUC) were 58.5 +/- 6.3 micrograms hr/ml on day 1, 58.5 +/- 3.1 micrograms hr/ml on day 3 and 58.1 +/- 8.5 micrograms hr/ml on day 5. The biological half-lives (t1/2) were 2.45 +/- 0.35, 2.09 +/- 0.82 and 2.49 +/- 0.63 hours, after dosing on day 1, day 3 and day 5, respectively. The analysis of moment in pharmacokinetics revealed that the mean residence time (MRT) on day 1, day 3 and day 5 observed were 2.31 +/- 0.03, 2.15 +/- 0.09 and 2.15 +/- 0.07 hours, respectively. The variance residence times (VRT) observed were 0.95 +/- 0.05 hour2 on day 1, 0.88 +/- 0.09 hour2 on day 3 and 1.06 +/- 0.07 hour2 on day 5. The ratios of accumulation calculated were 1.16 +/- 0.05 in both the morning medication on day 3 day 5, and it therefore appears that the steady-state equilibrium is established within 3 days after commencement of dosage.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
57.
58.
From October, 1980, to June, 1987, thirty-eight infants less than one year old underwent correction for total anomalous pulmonary venous connection (TAPVC). Overall operative mortality and late mortality were 13% and 6%, respectively. Residual pulmonary hypertension was noted in 4 patients: three had pulmonary venous obstruction at the site of atrial anastomosis (PVOA) and one had supracardiac (Ia) lesion left after repair of mixed type (IV: Ia + III) of TAPVC. Two late deaths occurred in these with PVOA. Twenty-two patients with supracardiac (I) or infracardiac (III) TAPVC were divided into three groups according to the technical development in atrial anastomosis: the large anastomosis in which venous incision reached into at least one pulmonary vein beyond common pulmonary vein and the continuous running suture were used in 10 patients (group 1), the appropriate size of anastomosis in which venous incision limited within the common pulmonary vein and the continuous running suture used in 4 patients (group 2), and the appropriate size of anastomosis and the interrupted suture in 8 patients (group 3). PVOA were 3 (33%) in group 1, but 0 (0%) in group 2 and 3. Two late death occurred all in group 1 with PVOA. Cardiopulmonary bypass time and aortic clamp time in group 3 were 91 min and 74 min respectively, which did not become longer than those in both group 1 and group 2. Interrupted suture technique does not make operating time longer than continuous running suture one. PVOA is one of the important factors predicting late operative result.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
59.
60.
Heterotopic heart transplantation: a radiographic review   总被引:1,自引:0,他引:1  
Heterotopic heart transplantation can be performed in the presence of high pulmonary vascular resistance. The authors call attention to a rare, but potentially life-saving procedure.  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