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   1750篇
  免费   295篇
  国内免费   39篇
耳鼻咽喉   17篇
儿科学   102篇
妇产科学   19篇
基础医学   101篇
口腔科学   34篇
临床医学   293篇
内科学   589篇
皮肤病学   60篇
神经病学   176篇
特种医学   279篇
外科学   188篇
综合类   31篇
预防医学   66篇
眼科学   16篇
药学   57篇
中国医学   1篇
肿瘤学   55篇
  2024年   9篇
  2023年   52篇
  2022年   13篇
  2021年   29篇
  2020年   90篇
  2019年   14篇
  2018年   89篇
  2017年   69篇
  2016年   68篇
  2015年   62篇
  2014年   94篇
  2013年   110篇
  2012年   45篇
  2011年   36篇
  2010年   80篇
  2009年   109篇
  2008年   42篇
  2007年   46篇
  2006年   43篇
  2005年   28篇
  2004年   15篇
  2003年   17篇
  2002年   15篇
  2001年   32篇
  2000年   14篇
  1999年   25篇
  1998年   80篇
  1997年   96篇
  1996年   78篇
  1995年   68篇
  1994年   50篇
  1993年   52篇
  1992年   31篇
  1991年   16篇
  1990年   25篇
  1989年   54篇
  1988年   43篇
  1987年   27篇
  1986年   22篇
  1985年   23篇
  1984年   18篇
  1983年   11篇
  1982年   14篇
  1981年   15篇
  1980年   15篇
  1979年   9篇
  1977年   9篇
  1976年   11篇
  1975年   8篇
  1971年   8篇
排序方式: 共有2084条查询结果,搜索用时 31 毫秒
21.
As more mutations are identified in genes of known sequence, there is a crucial need in the areas of medical genetics and genome analysis for rapid, accurate and cost-effective methods of mutation detection. We have developed a multiplex allele-specific diagnostic assay (MASDA) for analysis of large numbers of samples (> 500) simultaneously for a large number of known mutations (> 100) in a single assay. MASDA utilizes oligonucleotide hybridization to interrogate DNA sequences. Multiplex DNA samples are immobilized on a solid support and a single hybridization is performed with a pool of allele-specific oligonucleotide (ASO) probes. Any probes complementary to specific mutations present in a given sample are in effect affinity purified from the pool by the target DNA. Sequence-specific band patterns (fingerprints), generated by chemical or enzymatic sequencing of the bound ASO(s), easily identify the specific mutation(s). Using this design, in a single diagnostic assay, we tested samples for 66 cystic fibrosis (CF) mutations, 14 beta-thalassemia mutations, two sickle cell anemia (SCA) mutations, three Tay-Sachs mutations, eight Gaucher mutations, four mutations in Canavan disease, four mutations in Fanconi anemia, and five mutations in BRCA1. Each mutation was correctly identified. Finally, in a blinded study of 106 of these mutations in > 500 patients, all mutations were properly identified. There were no false positives or false negatives. The MASDA assay is capable of detecting point mutations as well as small insertion or deletion mutations. This technology is amenable to automation and is suitable for immediate utilization for high-throughput genetic diagnostics in clinical and research laboratories.   相似文献   
22.
Oocyte morphology predicts outcome of intracytoplasmic sperm injection   总被引:10,自引:14,他引:10  
To examine the influence of cytoplasmic morphology on the success rate of intracytoplasmic sperm injection (ICSI), the morphology of 837 metaphase II oocytes was assessed after cumulus stripping. The main abnormalities detected were excessive granularity, cytoplasmic inclusions such as vacuoles, smooth endoplasmic reticulum clustering and refractile bodies. Microinjection was performed in 538 oocytes with normal cytoplasm, 142 out of 161 with excessive granularity and 112 out of 138 with cytoplasmic inclusions. Very poor oocytes were not injected. No difference was found in fertilization rate. The embryos achieved cleaved normally and a similar number of good quality embryos among the three groups was noted. The outcome of transfer of embryos derived solely from normal oocytes (group A: 72 patients, 183 embryos) was compared with those from oocytes with cytoplasmic abnormalities (group B: 34 patients, 85 embryos). In group A, 17 clinical pregnancies (24% per patient, implantation rate 10%) were established. In group B, only one clinical pregnancy (3% per patient, implantation rate 1%) was established, from the transfer of embryos derived from oocytes with homogeneous granularity of the cytoplasm. No pregnancy resulted following the transfer of embryos from eggs with cytoplasmic inclusions. The difference was statistically significant. The outcome of ICSI is dependent on the quality of the oocytes retrieved. Normal fertilization and early embryo development were achieved in oocytes with abnormal cytoplasm morphology, but the resulting embryos failed to demonstrate the same implantation potential as those derived from oocytes with normal cytoplasm.   相似文献   
23.
24.
25.
26.
Biochemical, genetic, and morphological criteria were used to demonstrate that human cytomegalovirus penetrates permissive fibroblasts and nonpermissive Chinese hamster ovary (CHO) cells by pH-independent fusion between the virus envelope and the host cell plasma membrane and not by low pH-induced fusion within endosomes. Viral immediate early (IE) gene expression and infectivity were unaffected by conditions which block various stages of endocytosis or agents that alter the acidic pH of the endosome. IE gene expression was also evident in a mutant CHO cell line which is defective in endosomal acidification. Morphological analysis of the entry process at the electron microscopic level revealed viral particles in various stages of virion-plasma membrane fusion. In contrast, intact enveloped virions were not observed sequestered within coated pits or vesicular structures. Collectively, the data indicate that the entry pathway by which HCMV gains access to the cytoplasm of fibroblasts and CHO cells in order to initiate infection is via pH independent, virion envelope-plasma membrane fusion.  相似文献   
27.
Cicatricial conjunctivitis may be a sequel to systemic disorders (eg, Stevens-Johnson syndrome, cicatricial pemphigoid) or local disorders such as chemical burns. The cicatrisation is often associated with corneal epithelial changes that cause visual loss. These have been attributed to encroachment of the conjunctival epithelium over the cornea. However, the epithelial anomalies are poorly understood. We investigated the corneal epithelial changes in cicatricial conjunctivitis with an immunohistochemical study of intermediate filaments in normal and pathological specimens. Our results show that the normal corneal epithelium is immunoreactive for cytokeratin 3 (CK 3) but not cytokeratin 19 (CK 19), whereas normal conjunctival epithelium is CK 3 negative and CK 19 positive. Conjunctiva artificially transposed over the cornea (after therapeutic conjunctival flap reconstruction) retained the normal pattern of conjunctival cytokeratin expression (CK 3 negative, CK 19 positive). Conversely, the entire corneal epithelium exhibited the normal cytokeratin pattern (CK 3 positive, CK 19 negative) in 82% of Stevens-Johnson, 80% of cicatricial pemphigoid, and 69% of chemical burns specimens. The findings suggest that conjunctival encroachment is not responsible for the changes at the corneal surface in cicatricial conjunctivitis and that the abnormal corneal epithelium is derived from native corneal cells in these diseases.  相似文献   
28.
李承青  彭德民  王彩霞 《医学争鸣》2000,21(12):1439-1439
0 引言 急性乳腺炎是产后妇女的常见病 .我们采用针头挑拨治疗急性乳腺炎 32例 ,疗效显著 .1 临床资料 患者 32例 ,年龄 2 3~ 34 (平均 2 5 .3)岁 ,均为产后哺乳产妇 .其中患乳胀痛为共有症状 .伴发热 10例 ;右侧乳腺炎 14例 ,左侧乳腺炎 16例 ,双侧乳腺炎 2例 ;外上象限胀痛 6例 ,外下象限胀痛 8例 ,内上象限胀痛 7例 ,内下象限胀痛 6例 ,二象限同时胀痛 5例 .乳头均无破损 .患者取卧位 ,显露患乳 ,乳头以碘伏严密消毒后 ,术者持五号针头以指腹常规触诊患乳 ,触摸到肿胀部位后 ,沿乳腺管走行方向找到对应的乳头腺管口 ,以针尖轻轻挑拨…  相似文献   
29.
30.
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