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   442篇
  免费   40篇
  国内免费   2篇
耳鼻咽喉   18篇
儿科学   14篇
妇产科学   4篇
基础医学   76篇
口腔科学   9篇
临床医学   41篇
内科学   116篇
皮肤病学   9篇
神经病学   22篇
特种医学   33篇
外科学   35篇
综合类   10篇
预防医学   47篇
眼科学   7篇
药学   26篇
中国医学   1篇
肿瘤学   16篇
  2021年   8篇
  2020年   4篇
  2018年   8篇
  2017年   4篇
  2016年   10篇
  2015年   6篇
  2014年   14篇
  2013年   25篇
  2012年   14篇
  2011年   13篇
  2010年   9篇
  2009年   19篇
  2008年   16篇
  2007年   16篇
  2006年   14篇
  2005年   17篇
  2004年   19篇
  2003年   21篇
  2002年   6篇
  2001年   19篇
  2000年   22篇
  1999年   11篇
  1998年   11篇
  1997年   10篇
  1996年   10篇
  1995年   4篇
  1994年   6篇
  1993年   5篇
  1992年   6篇
  1990年   8篇
  1989年   4篇
  1988年   8篇
  1987年   8篇
  1986年   8篇
  1985年   4篇
  1984年   5篇
  1983年   3篇
  1982年   4篇
  1981年   4篇
  1980年   5篇
  1979年   7篇
  1978年   5篇
  1977年   3篇
  1976年   6篇
  1975年   7篇
  1974年   6篇
  1973年   6篇
  1972年   9篇
  1971年   4篇
  1970年   4篇
排序方式: 共有484条查询结果,搜索用时 24 毫秒
1.
The effect of long-term treatment with the calcium antagonist nisoldipine on development of hypertension, cardiac hypertrophy, and plasma levels of atrial natriuretic peptides (ANP) was determined in spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY) of the same age. Measurement of immunoreactive ANP in plasma provided a sensitive marker for the severity of hypertension and the associated cardiac overload. Long-term treatment with nisoldipine prevented the development of hypertension, the associated heart failure, and the increase of plasma levels of ANP in SHR but had no effect on systolic blood pressure, heart weight, and plasma levels of ANP in WKY. In addition, nisoldipine had a therapeutic effect in old SHR with manifest cardiac failure in end-stage hypertension, as evidenced not only by the reduction of blood pressure but also by the reduction of cardiac hypertrophy, of elevated immunoreactive ANP in plasma, and of increased plasma renin activity.  相似文献   
2.
3.
Neuroimaging in Pineal Tumors   总被引:4,自引:0,他引:4  
F Reis  MD  AV Faria  MD  PhD  VA Zanardi  MD  PhD  JR Menezes  MD  F Cendes  MD  PhD  LS Queiroz  MD  PhD 《Journal of neuroimaging》2006,16(1):52-58
BACKGROUND AND PURPOSE: The authors report radiological findings in 11 tumors in the pineal region, which were histologically diagnosed as germinomas, pineocytomas pineoblastomas, ependymomas, teratomas, and astrocytomas. METHODS: Computed tomography (CT) was performed in seven patients and magnetic resonance imaging (MRI) was performed in all patients. RESULTS: CT showed a solid or solid/cystic mass with variable contrast enhancement. MRI showed a heterogeneous mass, with hypointense signal on T1 and iso/hyperintense signal on T2-weighted images (WI) and gadolinium enhancement. Extension to adjacent structures occurred in five patients and spread through the cerebral spinal fluid (CSF) in two. CONCLUSIONS: Pineal region tumors have no pathognomonic imaging pattern. MRI and CT are complementary in diagnosis and are important to determine localization, extension, and meningeal spread.  相似文献   
4.
5.
The synthesis of aryldiazonium and arylazido derivatives of carfentanil, etonitazene, and naltrexone and of a triazaspirodecane derivative is described. The chemical stability and the spectral characteristics of these compounds were verified, and their binding affinity constants for the different opioid receptor classes were determined, in the absence of light, from competition experiments. With the exception of the naltrexyl derivatives, which remained nonselective, all compounds tested displayed a pronounced mu-binding selectivity with mu/delta and mu/kappa ratios ranging from 12 to 1000. After irradiation, only the arylazido probes led to an irreversible mu-binding-site inactivation. This inactivation fulfilled the criteria for photoaffinity labeling such as protection against inactivation by other opiate ligands and absence of an effect of scavengers on the extent of the inactivation. Most of the photoactivatable probes formed long-lasting reversible complexes with the opioid binding sites: an efficient dissociation procedure was thus required to discriminate between pseudoirreversible and covalent complexes. The marked differences in labeling efficacy between aryldiazonium salts and their corresponding arylazido derivatives are discussed.  相似文献   
6.
It was previously proposed that an immunological cross-reaction between two denatured proteins is evidence for an homology betweeen their amino sequence (Arnon &; Maron, 1971; Arnheim et al., 1971) and that detection of such a cross-reaction could then be a rapid method to detect sequence homologies (Zakin et al., 1978). In order to test the possibilities of such a methodology, using proteins of known structure, glyceraldehyde 3-phosphate dehydrogenases from different sources are compared by immunochemical techniques. The antibodies raised against the native enzyme from E. coli K 12 can only recognize the homologous antigen, the glyceraldehyde 3-phosphate dehydrogenase from B. stearothermophilus and to a lesser extent that from halibut. In contrast, the antibodies raised against the denatured enzyme from E. coli K 12 can recognize the glyceraldehyde 3-phosphate dehydrogenases from man, ostrich, chicken, sturgeon, halibut, lobster and yeast, when in their denatured state. The present results show unambiguously that through exposure of buried sequences, the immunochemical detection of sequence homologies among proteins is more discriminating when unfolded proteins are used, rather than native ones. It is also proposed that the use of denatured proteins both as immunogens and antigens would be a useful tool in studying biochemical evolution.  相似文献   
7.
Specificity of in vitro reconstitution of bromegrass mosaic virus   总被引:1,自引:0,他引:1  
Cuillel M  Herzog M  Hirth L 《Virology》1979,95(1):146-153
Bromegrass mosaic virus (BMV) RNA was allowed to compete with yeast tRNA or alfalfa mosaic virus (AMV) RNA for in vitro encapsidation by BMV protein. Various proportions of 32P-labeled foreign RNAs were added to a reassembly mixture (BMV protein: BMV RNA, 4:1) and the reassembly products were observed by analytical and rate-zonal sedimentation, and the RNA contents of the nucleocapsids were examined by gel electrophoresis. Incubation of BMV protein with tRNA alone produced 56 S particles containing five or six tRNA molecules per particle, but with both tRNA and BMV RNA present very little of the tRNA was incorporated. AMV 12 S RNA led to 64 S particles containing one AMV RNA molecule: with both AMV and BMV RNAs present, the smallest BMV RNA outcompeted the AMV RNA about fourfold, even though the two RNAs have similar molecular weights and biological functions. Evidently BMV protein does to some extent specifically recognise its own RNA molecules.  相似文献   
8.
9.
A pilot study was designed to examine whether the outcome of embryo transfer in women with a hydrosalpinx might be improved by surgical drainage of the hydrosalpinx at the time of oocyte collection for in- vitro fertilization treatment. A comparative, controlled but retrospective analysis of the results was performed of all women with infective tubal damage aged <40 years old, who had ovulatory cycles, a normal uterus and a partner with normal spermatozoa. A standardized treatment regimen was used. A maximum of three embryos were transferred. Hydrosalpinx was defined by prior hysterosalpingography and/or laparoscopy with transcervical dye injection. A total of 237 embryo transfer cycles in women with hydrosalpinges (tubal distension not visible in 151, visible but not drained in 30 and drained in 56) were compared with 705 embryo transfer cycles in women with tubal disease but no hydrosalpinx. Results were analysed in the first three cycles but also separately in the first cycle to check for bias. Success rates were higher in the first cycle, but did not significantly influence overall differences. Implantation rates were significantly reduced overall in the hydrosalpinx group (8.0 versus 13.2% for controls; P < 0.001), being 8.3% (P < 0.01) in the subgroup without evident tubal distension and 7.5% (not significant) in the drained hydrosalpinx group. This study shows that tubal damage with distal occlusion is associated with a marked reduction in embryo implantation, even in the absence of obvious fluid distension. Surgical drainage of distended hydrosalpinges appears to offer no benefit.   相似文献   
10.
目的对十年前后精神分裂症患者用药情况的变化进行调查分析.方法对十年前后两个五年段的各500份符合精神分裂症诊断标准的病历进行回顾性调查,并对各项指标进行对比分析.结果两组折算用药剂量经t检验差异无显著性(P>0.05);两组合并用药、合并抗胆碱药及疗效经χ2检验差异有显著性(P<0.01);十年后非典型抗精神病药物氯氮平在临床上的应用比例明显增大并上升为首位.结论十年前后两组抗精神病药的应用发生了明显变化,疗效好、副作用轻的非典型抗精神病药的应用比例明显增加.  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