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   1845篇
  免费   135篇
  国内免费   3篇
耳鼻咽喉   29篇
儿科学   61篇
妇产科学   46篇
基础医学   309篇
口腔科学   38篇
临床医学   151篇
内科学   355篇
皮肤病学   31篇
神经病学   167篇
特种医学   46篇
外科学   312篇
综合类   15篇
一般理论   1篇
预防医学   119篇
眼科学   16篇
药学   132篇
中国医学   19篇
肿瘤学   136篇
  2023年   19篇
  2022年   20篇
  2021年   66篇
  2020年   45篇
  2019年   42篇
  2018年   68篇
  2017年   40篇
  2016年   53篇
  2015年   56篇
  2014年   73篇
  2013年   95篇
  2012年   114篇
  2011年   136篇
  2010年   70篇
  2009年   59篇
  2008年   108篇
  2007年   109篇
  2006年   111篇
  2005年   69篇
  2004年   83篇
  2003年   81篇
  2002年   65篇
  2001年   39篇
  2000年   46篇
  1999年   30篇
  1998年   12篇
  1997年   14篇
  1996年   18篇
  1995年   11篇
  1993年   6篇
  1992年   34篇
  1991年   15篇
  1990年   14篇
  1989年   16篇
  1988年   23篇
  1987年   7篇
  1986年   9篇
  1985年   13篇
  1984年   14篇
  1983年   4篇
  1981年   4篇
  1979年   4篇
  1978年   6篇
  1977年   4篇
  1976年   4篇
  1973年   9篇
  1971年   7篇
  1969年   3篇
  1967年   4篇
  1966年   4篇
排序方式: 共有1983条查询结果,搜索用时 31 毫秒
101.
BACKGROUND: Neurologic impairment after coronary artery bypass grafting is associated with cerebral embolization. An important cause of embolism is aortic manipulation. Constructing both distal and proximal anastomoses during a single period of aortic cross-clamping avoids this source of embolism and may reduce neurologic injury after coronary artery bypass grafting. METHODS: Fifty consecutive patients undergoing coronary artery bypass grafting were prospectively randomized to group 1, in which a single aortic cross-clamping was used to construct distal and proximal anastomoses, or to group 2, in which the proximal anastomoses were each constructed with a partial occluding aortic clamp. Levels of S-100 and troponin-T release were measured preoperatively and postoperatively. RESULTS: Aortic cross-clamp time was significantly longer in group 1, but other preoperative and intraoperative variables were equally represented in both groups. Control group levels of S-100 and troponin-T were similar. Postoperative S-100 levels were significantly higher in group 2 than in group 1 (p < 0.015). No significant difference was found between the groups in postoperative troponin-T levels. CONCLUSIONS: The results of this trial suggest improved cerebral protection is associated with the single aortic cross-clamp technique for coronary artery bypass grafting with no increase in myocardial damage. The single aortic cross-clamp technique is simple and inexpensive. We recommend its wider use.  相似文献   
102.
103.
Background: A 7-valent pneumococcal conjugate vaccine (7vPnC) has markedly reduced invasive pneumococcal disease (IPD) in routine use in the USA and is in clinical development in Japan. But a 13-valent pneumococcal conjugate vaccine (13vPnC) would cover even more serotypes. Because vaccines are administered to children by s.c. injection in Japan but by i.m. injection in the USA, a phase I study of s.c. injected 13vPnC in healthy Japanese adults was appropriate before commencing trials in Japanese children and older adults.
Methods: This was a randomized comparison in healthy Japanese adults of s.c. administered 13-valent pneumococcal conjugate vaccine and s.c. administered 23-valent plain polysaccharide pneumococcal vaccine (23vPn). Local and systemic reactions were recorded in a daily diary for 14 days after injection. IgG antibodies to serotype-specific capsular polysaccharide were measured on enzyme-linked immunosorbent assay on samples taken before and approximately 1 month after immunization.
Results: A total of 15 subjects were evaluable for safety review in each treatment group. There was a trend towards more local reactions in the 13vPnC group, which may be associated with s.c. administration of aluminum-containing vaccines as used routinely in Japan; but the local reactogenicity was mostly mild or moderate. Both 13vPnC and 23vPn were immunogenic for all types, with the exception of 6A, which is not included in 23vPn and for which only 13vPnC was immunogenic.
Conclusions: Overall, immunogenicity and tolerance was adequate to lead to studies of 13vPnC in both infants and older adults in Japan, using the s.c. route if appropriate.  相似文献   
104.
105.
BACKGROUND: Ankle sprains are frequent, especially in athletes, soldiers, or others who perform high levels of physical activity. Although prevention is a primary goal, little is known about the risk factors. We evaluated the association of the structure of the medial arch of the foot to the occurrence of acute and recurrent ankle sprains in 83 female infantry recruits. We found no previous studies on ankle sprains in women in the English literature. METHODS: Arch height was quantified using the Chippaux-Smirak index, and each arch was classified as high, normal, or low. Retrospective data were obtained from questionnaires in which the soldiers noted whether or not they had had ankle sprains in the past, the grade of the sprain, and recurrence. Prospective data were accumulated in the 4 months of basic training, during which time every ankle sprain was documented and classified according to its grade and cause. RESULTS: The retrospective data showed more frequent ankle sprains in the low arch group than in the normal arch group, mainly in the right foot (RR of 2.9, p <0.05). Recurrent sprains studied retrospectively also showed that more sprains occurred in the low arch group than in the normal arch and high arch groups (RR of 10.3, p <0.05). The prospective data suggested a pattern toward the same outcome (50% in the low arch as opposed to 36% in the normal arch group, RR, 1.3), but with no statistical significance. CONCLUSIONS: We concluded that a low arch of the foot might be a risk factor for ankle sprains. However, our study consisted of a relatively small population, and further studies are needed.  相似文献   
106.
107.
108.
Potential O-acetylation of the sialic acid residues of Escherichia coli K1, groups W-135, Y, and C meningococci, and group B Streptococcus capsular polysaccharides modifies their immunogenicity and susceptibility to glycosidases. Despite the biological importance of O-acetylation, no sialic or polysialic acid O-acetyltransferase has been identified in any system. Here we show that the E. coli K1 O-acetyltransferase encoded by neuO is genetically linked to the endo-neuraminidase tail protein gene of a chromosomal accretion element, designated CUS-3, with homology to lambdoid bacteriophage. Molecular epidemiological analysis established concordance between O-acetyltransferase and CUS-3 in a set of E. coli K1 strains. Deleting neuO eliminated enzymatic activity, which was restored by complementation in trans, and confirmed by (13)C-NMR analysis of the acetylated product. Analysis of mutants that accumulate intracellular polysialic acid because of export defects (kpsM and kpsS) or an inability to synthesize the sialic acid precursor, N-acetylmannosamine (neuC), indicated that NeuO does not require constant association with its substrate for activity. DNA sequencing and PCR analysis of neuO from strains that had undergone random capsule form variation showed that slip strand DNA mispairing or unequal recombination resulted in gain or loss of (5'-AAGACTC-3')(n) heptanucleotide repeats (where n approximately equals 14-39) located in the neuO 5' region. These repeats code for a previously undescribed structure designated the poly(Psi) motif. The unexpected discovery of the neuO contingency locus (hypervariable gene controlling expression of a surface epitope) in E. coli, and of a potential phage for redistributing variant neuO alleles, provides a robust system for investigating the functions of localized hypermutability in pathogen evolution.  相似文献   
109.
The behavioral test described by Porsolt in 1977 for screening potential antidepressant drugs is extensively used both in basic research and in the pharmaceutical industry. The measured behavior is the immobility time during the swimming test (preformed in rodents), which decreases upon acute antidepressant treatment. Several research groups have suggested some modifications on the original Porsolt paradigm and its analysis. Nevertheless, there are still inaccuracies resulting from either undefined intermediate behaviors or from considering the movement of the whole body as one unit without analyzing the motion of the limbs. Herein, we propose a novel and simple scoring method, based on continuous measurement of the limbs motion, using a joystick, a computer screen and simple software. We validated the method, using antidepressant drugs and studied examples of false positives and false negatives of the traditional Porsolt paradigm. The proposed method is easy to use, it accounts for all range of movements and the analysis is relatively fast. Moreover, the results obtained using this analysis method show a normal Gaussian distribution in a population of rats (while the traditional Porsolt analysis does not) which allows selective breeding of 'motivated' and 'depressed' lines of animals.  相似文献   
110.
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