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   248篇
  免费   21篇
  国内免费   27篇
耳鼻咽喉   1篇
儿科学   20篇
妇产科学   3篇
基础医学   36篇
口腔科学   18篇
临床医学   45篇
内科学   59篇
皮肤病学   8篇
神经病学   5篇
特种医学   25篇
外科学   20篇
综合类   18篇
预防医学   8篇
药学   14篇
中国医学   1篇
肿瘤学   15篇
  2023年   1篇
  2022年   2篇
  2021年   1篇
  2020年   2篇
  2019年   3篇
  2018年   5篇
  2017年   6篇
  2016年   7篇
  2015年   6篇
  2014年   7篇
  2013年   12篇
  2012年   3篇
  2011年   4篇
  2010年   10篇
  2009年   11篇
  2008年   5篇
  2007年   15篇
  2006年   5篇
  2005年   13篇
  2004年   4篇
  2003年   1篇
  2002年   7篇
  2001年   9篇
  2000年   4篇
  1999年   8篇
  1998年   21篇
  1997年   18篇
  1996年   17篇
  1995年   13篇
  1994年   14篇
  1993年   3篇
  1992年   4篇
  1991年   3篇
  1990年   3篇
  1989年   7篇
  1988年   5篇
  1987年   5篇
  1986年   10篇
  1985年   4篇
  1982年   2篇
  1981年   2篇
  1980年   1篇
  1978年   3篇
  1977年   3篇
  1976年   4篇
  1975年   3篇
排序方式: 共有296条查询结果,搜索用时 31 毫秒
91.
目的:研究Down’s 综合征动物模型trisomy 16 结肠神经系发育和先天性巨结肠(HD) 病变肠管蛋白基因产物9-5(protein gene product9 .5 ,PGP9-5) 的神经表达。方法:Trisomy 16 鼠培育;细胞遗传学分析;Trisomy 16 鼠结肠和HDPGP9-5 免疫组织化学。结果:(1)Trisomy 16 鼠结肠神经系发育异常,肌间神经丛发育迟缓,粘膜下神经丛缺失,结肠末端有5 mm 的无神经节区,但结肠系膜神经发育良好;(2)HD狭窄段肠管PGP9-5 阳性神经纤维大量增生,神经节细胞缺如。结论:(1)Trisomy 16 鼠具有稳定的遗传学特征,可能伴先天性巨结肠。(2) 由于HD 狭窄段肠管神经节细胞缺失,增生的PGP9-5 阳性神经纤维是肠道外源性神经的代偿,对其神经元的性质尚有待确定。(3)HD有遗传倾向  相似文献   
92.
The degradation of fibrillar type II collagen is a major feature of cartilage destruction in rheumatoid arthritis (RA). Since collagenase 3 is produced by chondrocytes and preferentially degrades type II cartilage collagen, it seemed likely that this enzyme would have a prominent role in the destruction of rheumatoid joints. Using immunolocalization techniques, we have examined and compared the production and distributions of collagenase 1 and collagenase 3 in cells and tissues derived from rheumatoid knee arthroplasties. Primary cultures of chondrocytes stimulated with interleukin-1 beta showed that most of the cells produced collagenase 1, whereas only a minority (approximately 5-10%) produced collagenase 3; a few chondrocytes demonstrated the co-ordinate production of both enzymes. Primary cultures of rheumatoid synoviocytes produced collagenase 1, but not collagenase 3. Both enzymes were demonstrated in the rheumatoid lesion. Collagenase 1 was more commonly observed in both synovium and cartilage (22 of the 28 specimens), was especially prominent at cartilage erosion sites, and most of the positive specimens demonstrated extracellular enzyme. By contrast, collagenase 3 was observed less frequently (7/28 specimens) and was produced by relatively few chondrocytes and synovial cells, this usually being much less than that observed for chondrocytes of osteoarthritic cartilage. These observations suggest different regulatory mechanisms for the production of collagenases 1 and 3 in the rheumatoid lesion, and demonstrate that the distribution and production of collagenase 1 are far more prevalent than those for collagenase 3.   相似文献   
93.
Kanno  H; Wei  DC; Chan  LC; Mizoguchi  H; Ando  M; Nakahata  T; Narisawa  K; Fujii  H; Miwa  S 《Blood》1994,84(10):3505-3509
We identified four distinct point mutations in homozygous pyruvate kinase (PK) variants in Japanese and Chinese patients with chronic nonspherocytic hemolytic anemia. All gene abnormalities were missense mutations that caused single amino acid substitutions. 1261A (Q421K) and 1436A (R436H), which were identified in PK Sendai and PK Shinshu, had been found in unrelated Japanese and Amish PK variants, respectively. The clinical severity and extremely low residual erythrocyte PK activity of PK Shinshu as well as of the Amish PK might be caused partly by aberrant splicing, because the 1436A mutation changes a nucleotide at the last nucleotide in the exon 10. Recently, we diagnosed a 42-year-old Japanese woman with chronic nonspherocytic hemolytic anemia as having a homozygous PK deficiency. DNA sequencing of the variant PK gene showed a homozygous missense mutation at 1403GCT- ->GTT, resulting in a single amino acid substitution from 468la-->Val. The gene mutation is likely to impair the allostericity of this enzyme, speculated from the tertiary structure. A homozygous missense mutation in PK Hong Kong, a boy of a non-Han southern Chinese minority group, was identified in exon 7 of the human L-PK gene, 941ATT-->ACT, resulting in a single amino acid substitution from 314lle-->Thr. The R- PK activity is expected to be severely affected, because the mutated amino acid residue is located between the 313 Lys and the 315 Glu, which are very important for acid-base catalysis and magnesium binding, respectively. Both the R- and M2-type PK were shown by polyacrylamide gel electrophoresis of the PK Hong Kong erythrocyte lysate, and this is the first report of a homozygous individual whose erythrocytes contain the immature (M2)-type isozyme.  相似文献   
94.
The palliative radiotherapeutic management of unresectable non‐small‐cell lung cancer is controversial, with various fractionation (Fx) schedules available. We aimed to determine patient’s choice of Fx schedule after involvement in a decision‐making process using a decision board. A decision board outlining the various advantages and disadvantages apparent in the Medical Research Council study of Fx schedules (17 Gy in two fractions vs 39 Gy in 13 fractions) was discussed with patients who met Medical Research Council eligibility criteria. Patients were then asked to indicate their preferred Fx schedules, reasons and their level of satisfaction with being involved in the decision‐making process. Radiation oncologists (RO) could prescribe radiotherapy schedules irrespective of patients’ preferences. Of 92 patients enrolled, 55% chose the longer schedule. English‐speaking patients were significantly more likely to choose the longer schedule (P = 0.02, 95% confidence interval: 1.2–7.6). Longer Fx was chosen because of longer survival (90%) and better local control (12%). Shorter Fx was chosen for shorter overall treatment duration (80%), cost (61%) and better symptom control (20%). In all, 56% of patients choosing the shorter schedule had their treatment altered by the treating RO, whereas only 4% of patients choosing longer Fx had their treatment altered (P < 0.001). Despite this, all (100%) patients were satisfied with being involved in the decision‐making process. The decision board was useful in aiding decision‐making, with both Fx schedules being acceptable to patients. Interestingly, despite the longer average survival associated with longer Fx, nearly half of the patients believed that this was not as important as a shorter duration of treatment and lower cost. Despite patients’ preferences, there were significant alterations of preferred schedules because of RO’s own biases.  相似文献   
95.

Background  

Several humoral immune factors are responsible for a successful pregnancy. There are a few studies, which demonstrate the role of antipaternal cytotoxic antibodies (APCA) and mixed lymphocyte reaction blocking factor (MLR-Bf) in the maintenance of pregnancy. However, these factors have not been studied in women with history of recurrent spontaneous abortion (RSA). We designed this study to review the role of APCA and MLR-Bf in normal pregnancy as well as in women with a history of RSA.  相似文献   
96.
氯屈膦酸二钠合成工艺改进   总被引:1,自引:0,他引:1  
目的:对氯屈膦酸二钠的合成工艺进行了研究。方法:以二溴甲烷和亚膦酸三异丙酯为原料,经缩合,氯化,热裂解和成盐反应得到氯屈膦酸二钠。结果:合成产物的化学结构经元素分析,红外光谱,质谱和核磁共振谱确证,总收率为60.3%。结论:此合成路线是完全可行的。  相似文献   
97.
98.
Extracorporeal formation of mineralized bone-like tissue is still an unsolved challenge in tissue engineering. Embryonic stem cells may open up new therapeutic options for the future and should be an interesting model for the analysis of fetal organogenesis. Here we describe a technique for culturing embryonic stem cells (ESCs) in the absence of artificial scaffolds which generated mineralized miromasses. Embryonic stem cells were harvested and osteogenic differentiation was stimulated by the addition of dexamethasone, ascorbic acid, and ß-glycerolphosphate (DAG). After three days of cultivation microspheres were formed. These spherical three-dimensional cell units showed a peripheral zone consisting of densely packed cell layers surrounded by minerals that were embedded in the extracellular matrix. Alizarine red staining confirmed evidence of mineralization after 10 days of DAG stimulation in the stimulated but not in the control group. Transmission electron microscopy demonstrated scorching crystallites and collagenous fibrils as early indication of bone formation. These extracellular structures resembled hydroxyl apatite-like crystals as demonstrated by distinct diffraction patterns using electron diffraction analysis. The micromass culture technique is an appropriate model to form three-dimensional bone-like micro-units without the need for an underlying scaffold. Further studies will have to show whether the technique is applicable also to pluripotent stem cells of different origin.  相似文献   
99.
LC 《健康之友》2011,(10):148-148
七月盛夏,宝岛台湾却惬意非常!浙江卫视女主播朱丹带领许多媒体朋友一同到南台湾做了一个很特别的美丽之旅,这一次,胶原蛋白不仅可以喝,还能被“看”出来。  相似文献   
100.
Perineal hernia is a rare complication following laparoscopic abdominoperineal resection (APR) for rectal cancer. We present two case reports of perineal hernia following laparoscopic APR and discuss their management. We suggest that they developed because the pelvic peritoneum was left open during laparoscopic APR and propose that closure of the pelvic peritoneum should be routine in this operation.  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