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   30786篇
  免费   2237篇
  国内免费   701篇
耳鼻咽喉   312篇
儿科学   624篇
妇产科学   242篇
基础医学   3639篇
口腔科学   2155篇
临床医学   2057篇
内科学   2484篇
皮肤病学   72篇
神经病学   578篇
特种医学   2140篇
外科学   11334篇
综合类   3417篇
预防医学   1062篇
眼科学   65篇
药学   1385篇
  10篇
中国医学   714篇
肿瘤学   1434篇
  2024年   41篇
  2023年   256篇
  2022年   651篇
  2021年   768篇
  2020年   652篇
  2019年   630篇
  2018年   833篇
  2017年   692篇
  2016年   941篇
  2015年   1058篇
  2014年   1804篇
  2013年   1834篇
  2012年   1550篇
  2011年   1824篇
  2010年   1551篇
  2009年   1734篇
  2008年   1670篇
  2007年   1694篇
  2006年   1609篇
  2005年   1607篇
  2004年   1310篇
  2003年   1123篇
  2002年   854篇
  2001年   754篇
  2000年   789篇
  1999年   632篇
  1998年   527篇
  1997年   510篇
  1996年   413篇
  1995年   391篇
  1994年   348篇
  1993年   295篇
  1992年   259篇
  1991年   223篇
  1990年   192篇
  1989年   158篇
  1988年   173篇
  1987年   139篇
  1986年   151篇
  1985年   138篇
  1984年   113篇
  1983年   59篇
  1982年   108篇
  1981年   89篇
  1980年   82篇
  1979年   97篇
  1978年   77篇
  1977年   72篇
  1976年   47篇
  1973年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Summary Total body bone mineral (TBBM) content in rats was measured by dual photon absorptiometry (DPA). TBBM showed significant increases over 4 weeks in control groups with significant bone loss over the same time in prednisolone-injected rats on low calcium feed. Daily injections of calcitonin significantly reduced loss of bone mass. Both prednisolone- and prednisolone-calcitonin-injected groups showed significantly elevated serum alkaline phosphatase with the prednisolone-calcitonin group also exhibiting elevated serum calcium and phosphate levels, confirming the impact of the experimental protocol. TBBM measured by DPA in all groups correlated well (r=0.928,P<0.001 n=20) with the total ash weight suggesting that the method reflects total skeletal mineral content in the small animal. TBBM measurement by DPA proves well-suited to monitoring bone mineral in a small animal experimental setting.  相似文献   
92.
Summary Precision of dual-photon absorptiometry (DPA) measurements was determined in a lumbar spine phantom and in humans. Approximately half of the measurements were made before and half after a153gadolinium source change. The phantom was measured with different amounts of acrylic, which simulates human soft tissue, in order to evaluate the influence of body thickness on bone mineral density (BMD). Results of scans analyzed with two software versions from Lunar Radiation Corp., the widely used 08B and a prototype 08C, are compared. DPA with a cold source significantly overestimated BMD in the phantom in the presence of large amounts (more than 25 cm) of soft tissue equivalent with version 08B but not with the newer version 08C. Similiarly, in nine subjects, there was a significant decrease in spine BMD after a source change when scans were analyzed with version 08B (mean difference 0.026 g/cm2,P=0.002) but not with 08C (0.01 g/cm2,P=0.234). No systematic effect of source change on femoral BMD measurements was observed. The SD of the mean difference of two measurements of the nine subjects was 0.019 g/cm2 (1.6% of the mean value) for the spine with software version 08B and 0.024 g/cm2 (2.0%) with version 08C, 0.03 g/cm2 (3.3%) for the femur neck, 0.03 g/cm2 (4.0%) for the greater trochanter, and 0.04 g/cm2 (4.9%) for Ward's triangle region of the proximal femur. The spine phanton was scanned on two other commercial bone densitometers in order to assess inter-instrument variation. Phantom measurements of L2-4 BMD made on two Lunar Radiation Corp model DP3 scanners which differed by 2% were 10 and 12% higher than those with a Norland Corp. model 2600 scanner.  相似文献   
93.
Summary The paucity of information on the effect of long-term high-dose salmon calcitonin administration on normal bone mineral metabolism and histology prompted an investigation of the influence of high-dose synthetic calcitonin in the rat. Serum ionized calcium, osteocalcin or BGP (bone gla protein), and immunoreactive PTH were measured serially during calcitonin administration and bone histomorphometry analyzed at 6 weeks (after sacrifice). Daily injections of salmon calcitonin, 0.4 IU/100 g (group B) and 2 IU/100 g (group C), resulted in significant hypocalcemia at 4 hours for both experimental groups (P<0.004). Serium iPTH was significantly higher over the study period for both groups administered calcitonin. Serum BGP levels were significantly lower than controls during the study in group C (P<0.002) and to a lesser extent in group B (P<0.05). In group C, bone histomorphometry revealed increased resorption (onteoclast count), decreased trabecular bone volume, and decreased double-labeled tetracycline surface (bone formation). In group B an increase in osteoclast count but no alteration in bone formation was observed. To assess the role of PTH in the above findings, high-dose calcitonin was administered to parathyroidectomized rats. All of the above changes in bone histomorphometry were not observed in this group of animals. In conclusion, high doses of calcitonin promote hypocalcemia, secondary hyperparathyroidism, and osteoclastosis in the normal rat in a dose-dependent manner with very high-dose calcitonin impairing bone formation.  相似文献   
94.
国产 89SrCl2治疗肿瘤骨转移灶所致骨痛临床多中心研究   总被引:1,自引:1,他引:0  
目的 验证上海科兴药业公司提供的89SrCl2 注射液治疗转移性骨肿瘤所致骨痛的疗效。方法 试验采用随机、双盲、阳性药物 (英国Amersham公司生产的Metastron)对照 ,5个中心参加验证。对 90例原发病灶诊断明确的恶性肿瘤骨转移患者进行骨痛镇痛治疗 ,其中资料完整的Ⅰ组(验证组 ) 5 9例 ,Ⅱ组 (对照组 ) 2 9例 ,余 2例患者剔除。Ⅰ组中男 30例 ,女 2 9例 ,年龄 2 5~ 80 (5 9 95±13 80 )岁 ;原发性恶性肿瘤肺癌 2 1例 ,乳腺癌 2 4例 ,前列腺癌 12例 ,胃癌、肝癌各 1例 ;治疗前骨痛评分为 6~ 12 (7 5 9± 1 5 9)。Ⅱ组中男 11例 ,女 18例 ,年龄 35~ 91(5 8 93± 14 6 0 )岁 ;原发性恶性肿瘤肺癌 10例 ,乳腺癌 12例 ,前列腺癌 6例 ,胃癌 1例 ;治疗前骨痛评分为 6~ 9(7 14± 1 4 6 )。入选患者均以 14 8MBq静脉注射给药 ,疼痛得分大于 6 ,体力状况评分平均≤ 70分 ,患者预期生存期至少大于3个月。全身99Tcm 亚甲基二膦酸盐 (MDP)骨显像示多发骨骼放射性浓聚灶 ,并经实验室及其他影像学检查证实。治疗后观察 3个月。结果 Ⅰ组镇痛有效率为 6 2 71% (37 5 9例 ) ;其中无效占 15 2 4 %(9 5 9例 ) ,好转占 2 2 0 3% (13 5 9例 ) ,显效占 5 5 93% (33 5 9例 ) ,完全缓解占 6 78% (4 5 9例 )。Ⅱ组镇  相似文献   
95.
目的探讨抗感染重组合异种骨(anti-infective reconstituted bone xenograft,ARBX)对犬污染性桡骨缺损的一期植骨修复的效果. 方法在重组合异种骨(reconstituted bone xenograft,RBX)基础上,结合抗生素局部缓释技术,制备具有较强抗感染能力和较高成骨作用的ARBX.取成年杂种犬8只,于双侧桡骨中上段制成15 mm节段性骨缺损,在缺损处注入5×106 CFU/ml金黄色葡萄球菌1 ml,静置15分钟后,于双侧缺损区分别植入ARBX、RBX,并用钢板固定.术后6个月对存活的6只犬进行取材,通过解剖学、X线片、组织学及细菌学检查,比较ARBX和RBX一期植骨修复犬污染性桡骨缺损的效果. 结果术后6个月,ARBX侧有5只完全修复,1只中央部3 mm缺损未修复,均无骨髓炎表现,标本细菌培养均为阴性.RBX侧有1只部分修复,5只未能修复,残留8~13 mm缺损,均有明显骨髓炎表现,标本细菌培养均为阳性. 结论 ARBX具有较高成骨活性和较强的抗菌能力,能够一期植骨修复细菌污染性骨缺损.  相似文献   
96.
目的寻找一种治疗骨不连接所需植骨材料,利用碱性成纤维细胞生长因子的活性诱导作用,促进骨修复.方法13例成人骨不连患者,选择4-10个月龄胎颅骨(FCB)作可吸收载体,结合碱性成纤维细胞生长因子(bFGF)制备成复合碱性成纤维细胞生长因子胎颅骨(bFGF/FCB),植入受骨区,以适当的内固定重新构建骨修复支架.结果所有患者均得到骨性修复,且成骨效应明显.结论胎颅骨作为植骨材料既可以起到植骨作用,增大植骨面,增加骨再生诱发点,屏蔽了骨断面,也避免了自体植骨的手术创伤;碱性成纤维细胞生长因子可以诱导和促进骨修复,二者复合物是治疗骨不连接的一种较好材料.  相似文献   
97.
目的 为了减轻免疫诱导过程中对受体的侵袭 ,进一步探讨以家兔为动物模型 ,通过异体骨髓移植诱导同种皮肤移植免疫耐受。方法 通过骨髓腔内直接注射异体骨髓细胞 ,进行骨髓移植。结果 皮片的平均存活时间是 (88.0± 6 .0 )天 (P <0 .0 0 1 )。为了探讨其普遍性 ,我们用此诱导方法 ,还进行了同种全耳移植。平均存活时间是 (1 4 6 .0± 1 5 .1 )天 ,并有 1只移植耳存活时间已超过 1年 ,未见任何排斥反应。结论 本研究证明了以家兔为动物模型 ,在不使用免疫抑制剂的情况下 ,通过骨髓腔内直接注射异体骨髓细胞 ,进行骨髓移植的方法 ,不仅在皮肤移植上可以诱导长期稳定的特异性免疫耐受 ,而且在实质性器官耳的同种移植上取得了良好的效果  相似文献   
98.
Osteoarthrosis (OA) is often associated with pain and disability, which are relieved after total knee arthroplasty (TKA), but the nature of bone changes associated with OA is controversial. We examined preoperative hip and contralateral knee bone mineral density (BMD) in patients requiring TKA and monitored the BMD changes postoperatively. Sixty-nine patients, scheduled to have TKA for osteoarthrotic knees, had both hips and contralateral knee BMD measured by dual-energy X-ray absorptiometry (DXA) at the time of operation (baseline) and at 1 yr after operation. X-rays of the knee joints were also taken to evaluate the severity of OA. Preoperatively, 27% and 38% of the patients had total hip BMD Z-score more than 1 SD in the operated side and contralateral hips, respectively. In all regions of interest (ROI), the mean baseline BMD of the affected side proximal femur was significantly lower than that of the contralateral side (p < 0.0005-0.019). The severity of OA was not associated with BMD. During 1-yr follow-up, the postoperative knee status and the physical activity of the patients (AKS score) improved. However, neither the hip nor the nonoperated knee BMDs increased. Knee OA is associated with significantly lower BMD values in the affected side compared with the contralateral hip, and these levels remained similar or decreased during a 1-yr follow-up. We conclude that improved mobility after TKA does not improve the effects of preoperative disuse-associated bone loss in the short term.  相似文献   
99.
逆行交锁髓内钉治疗股骨远段骨折   总被引:11,自引:0,他引:11  
目的 总结股骨逆行交锁髓内钉应用的适应证、优点及其疗效。方法 2001年6月~2003年6月,采用切开复位股骨逆行交锁髓内钉内固定,治疗股骨远段骨折21例,早期行膝关节功能锻炼。结果 18例获随访,全部骨性愈合,功能恢复良好,无膝痛、跛行、膝关节僵直等。结论 股骨逆行交锁髓内钉治疗股骨远段骨折具有明显优势,固定牢固、坚强,功能恢复快,并发症少等优点,手术不需要C臂X线机和骨科手术牵引床,适合基层医院临床应用。  相似文献   
100.
大鼠骨髓间充质干细胞转染人TH基因的实验研究   总被引:1,自引:1,他引:0  
目的评价酪氨酸羟化酶(tyrosine hydroxylase,TH)基因修饰骨髓间充质干细胞(mesenchymalstem cells,MSCs)后TH的表达情况及转染TH基因对MSCs的影响.方法构建含人TH基因的pCMV/hTH质粒,用脂质体转染原代培养的大鼠MSCs;Western blot及免疫细胞化学染色鉴定TH基因的表达及MSCs的分化情况;MTT比色法测定转染后的MSCs细胞活性,并与未转染的MSCs进行细胞活性比较.结果构建的pCMV/hTH质粒经ECoRI酶切后产生1.9okb和5.3kb的片段,与回收的目的基因及载体基因片段大小相符;转基因后的MSCs Western blot及免疫细胞化学染色显示TH染色阳性;转染后MSCs未见有NeuN,GFAP的表达;MTT比色法测定细胞活性,未转染与转染者差异无显著性.结论构建的TH基因能在体外培养的鼠MSCs中较好的表达,转染不会诱导MSCs向神经样细胞分化,对MSCs细胞活性无明显影响.  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