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   916篇
  免费   63篇
  国内免费   20篇
耳鼻咽喉   2篇
儿科学   57篇
妇产科学   46篇
基础医学   66篇
口腔科学   57篇
临床医学   96篇
内科学   220篇
皮肤病学   4篇
神经病学   56篇
特种医学   184篇
外科学   79篇
综合类   23篇
预防医学   36篇
眼科学   5篇
药学   32篇
  2篇
肿瘤学   34篇
  2019年   4篇
  2018年   10篇
  2017年   7篇
  2016年   6篇
  2015年   11篇
  2014年   9篇
  2013年   13篇
  2012年   13篇
  2011年   18篇
  2010年   14篇
  2009年   18篇
  2008年   19篇
  2007年   22篇
  2006年   16篇
  2005年   24篇
  2004年   18篇
  2003年   23篇
  2002年   22篇
  2001年   19篇
  2000年   23篇
  1999年   39篇
  1998年   36篇
  1997年   37篇
  1996年   40篇
  1995年   24篇
  1994年   29篇
  1993年   26篇
  1992年   26篇
  1991年   24篇
  1990年   21篇
  1989年   53篇
  1988年   27篇
  1987年   42篇
  1986年   31篇
  1985年   49篇
  1984年   28篇
  1983年   23篇
  1982年   14篇
  1981年   13篇
  1980年   17篇
  1979年   17篇
  1978年   4篇
  1977年   15篇
  1976年   11篇
  1975年   5篇
  1974年   4篇
  1973年   5篇
  1969年   4篇
  1968年   3篇
  1967年   6篇
排序方式: 共有999条查询结果,搜索用时 11 毫秒
41.
42.
Nasopharyngeal carriage of Haemophilus influenzae and Streptococcus pneumoniae was studied in 621 healthy Chinese children and 300 healthy Vietnamese children aged from 2 months to 5 years in Hong Kong. The carriage rate of H, influenzae type b in Vietnamese children was 1.3% (CI 0.04-2.63%); it was zero in Chinese. The carriage rate of non-typable H. influenzae was 5.8% (CI 1.4-7.6%) in Chinese and 65.4% (CI 58.9-69.8%) in Vietnamese. The carriage rates of S. pneumoniae were 10.8% (CI 8.3-13.2%) and 55.7% (CI 50.1-61.3%) in Chinese and Vietnamese children, respectively. Univariate and multivariate logistic regression analyses were performed to search for factors associated with differences in carriage rates of both H. influenzae and S. pneumoniae between Chinese and Vietnamese children. Although older age, smaller living area and parental smoking were associated with higher carriage rates, these could not explain the remarkably low carriage rates of both bacteria in Chinese children.  相似文献   
43.
SUMMARY: Radiology has been abounding with technological advances since the chest film first became the mainstay in diagnosing thoracic disease, and yet the conventional chest examination has endured as a front-line tool. The ability to perceive structural alterations is facilitated by a solid foundation in anatomy, which should be easy to achieve in a practice environment in which CT has become so commonplace. Not only is knowledge of anatomic nuances important for analysis of conventional radiographs, but it can only be an asset as multiplanar imaging is increasingly utilized and new modalities are developed over time. Some fundamental anatomic variations are revisited here through correlating the perspective provided by the lateral radiograph with the equally common one provided by routine axial CT images.  相似文献   
44.
45.
In order to prevent disease, one must understand the factors that contribute to the variance of the illness. In an effort to better understand factors that contribute to bulimia nervosa (BN), a study was designed to investigate explanatory factors in BN. Of particular interest to the researchers in the study was the effect of the Hispanic subculture on the variance of BN. Female participants (n = 372) and male participants (n = 109) from the ages of 17-49 agreed to serve in the study. A self-report scale designed to assess the symptoms of BN was the criterion variable in the study. Predictor variables included in the regression model were drive for thinness, body mass index (BMI), age, and ethnicity (Hispanic or Anglo). Separate analyses were run for males and females. Based on the results of the analysis it seems that the desire to be thinner and an individual's BMI contribute to the variance in BN for females, but not for males. There was no difference in the attitudes associated with BN between Hispanic (n = 27) and Anglo (n = 321) females.  相似文献   
46.
We present genealogical and longitudinal clinical observations and autopsy findings of a previously reported kindred, Family C (German-American), with late-onset autosomal dominant parkinsonism with evidence for linkage on chromosome 2p13. The clinical phenotype includes the cardinal features of idiopathic Parkinson's disease. In addition, postural tremor and dementia are detected in some individuals. Two members of the kindred, one affected and one unaffected have recently come to autopsy. The unaffected family member was an 82-year-old woman whose brain showed only mild age-related pathology and no evidence of subclinical Lewy body disease. In contrast, the affected family member was an 83-year-old man whose brain had neuronal loss, gliosis and Lewy bodies in the substantia nigra and other monoaminergic brain stem nuclei, as well as the basal forebrain and amygdala. Lewy bodies and Lewy neurites had a distribution typical of cases of idiopathic Parkinson's disease. Thus, the clinical and pathological findings in this family with autosomal dominant parkinsonism are similar to those of sporadic Parkinson's disease.  相似文献   
47.
48.
OBJECTIVE: The Delta valve is a pressure differential valve with a siphon control device. The valve mechanism is normally closed, but is designed to open in response to positive ventricular pressure, thereby avoiding overdrainage of cerebrospinal fluid (CSF). As a result, the incidence of subdural fluid collections as well as postural symptoms is purportedly reduced. In addition, the valve might reduce the number of obstructions as there would be no negative pressure sucking tissue and debris into the shunt system. In order to assess whether use of the Delta valve reduced the number of shunt-related problems as compared with two other pressure differential valves without an antisiphon component, we performed a retrospective review of all children undergoing CSF diversion procedures at our institution. METHODS: We reviewed the charts of 1, 193 patients. Cases included 2,325 ventriculoperitoneal (V-P) shunt insertions or revisions from January 1, 1985, to December 31, 1994, performed at our institution. The Delta valve and two pressure differential valves without antisiphon function were exclusively inserted during the following time periods: Holter-Hausner (H-H): January 1, 1985, to August, 1987; Heyer-Schulte (H-S): August, 1987, to June, 1991, and Delta: June, 1991, to December 31, 1994. RESULTS: Of the cases reviewed, 475 patients underwent insertion of a V-P shunt at the Childrens Hospital of Los Angeles and had a total of 686 shunt operations. Median follow-up was 3 years and ranged up to 10 years. Kaplan-Meier analysis documented that 67% of H-H, 71% of H-S and 70% of the Delta valves were functioning at 1-year follow-up. At 2-year follow-up, 66% of H-H, 64% of H-S and 65% of the Delta valves were functioning. The difference was not statistically significant. The occurrence rate for symptomatic subdural fluid collections was 0.7% (1/130) for H-H, 2.2% (3/139) for H-S and 1.0% (2/206) for the Delta valve (p = 0.52). The combined breakage/obstruction rate for the series was 7.7% (10/130) for H-H, 2.9% (4/139) for H-S and 4.9% (10/206) for the Delta valve (p = 0.19). No Delta valves malfunctioned secondary to fibrous capsule affecting the antisiphon device. CONCLUSIONS: In conclusion, it appears that performance of the Delta valve was not significantly different from the H-H and H-S valves, two valves without an antisiphon device. There was no significant difference in the occurrence of symptomatic subdural fluid collections based upon valve type, or in the combined valve breakage/obstruction rates based upon valve type.  相似文献   
49.
Odell JA  Alvarez S  Cvitkovich DG  Cortese DA  McComb BL 《Chest》2000,118(5):1503-1505
An occurrence of multiple chronic lung abscesses managed by lobectomy is described. These abscesses were present for 13 years in the patient, a nonimmunocompromised wood pulp worker. The patient had hemoptysis at presentation. The organism isolated was Ochroconis gallopavum, a dematiaceous fungus known to cause disease in immunocompromised patients and epidemic encephalitis in poultry. The fungus is typically found in warm environments and in decaying compost; for this reason, we postulate that his illness was occupationally acquired.  相似文献   
50.
The toxicity of Ni(II), Co(II) and Cu(II) in animals, and that of Cd(II) in cultured cells, has been associated with generation of the promutagenic lesion 8-oxo-7,8-dihydroguanine (8-oxoguanine) in DNA, among other effects. One possible source of this base may be 8-oxo-7,8- dihydro-2'-deoxyguanosine-5'-triphosphate (8-oxo-dGTP), a product of oxidative damage to the nucleotide pool, from which it is incorporated into DNA. To promote such incorporation, the metals would have to inhibit specific cellular 8-oxo-dGTPases that eliminate 8-oxo-dGTP from the nucleotide pool. The present study was designed to test such inhibition in vitro on 8-oxo-dGTPases from two different species, the human MTH1 protein and Escherichia coli MutT protein. In the presence of Mg(II), the natural activator of 8-oxo-dGTPases, all four metals were found to inhibit both enzymes. For MTH1, the IC50 values (+/- SE; n = 3-4) were 17 +/- 2 microM for Cu(II), 30 +/- 8 microM for Cd(II), 376 +/- 71 microM for Co(II) and 801 +/- 97 microM for Ni(II). For MutT, they were 60 +/- 6 microM for Cd(II), 102 +/- 8 microM for Cu(II), 1461 +/- 96 microM for Ni(II) and 8788 +/- 1003 microM for Co(II). Thus, Cu(II) and Cd(II) emerged as much stronger inhibitors than Ni(II) and Co(II), and MTH1 appeared to be generally more sensitive to metal inhibition than MutT. Interestingly, in the absence of Mg(II), the activity of the enzymes could be restored by Co(II) to 73% of that with Mg(II) alone for MutT, and 34% for MTH1, the other metals being much less or non-effective. The difference in sensitivity to metal inhibition between the two enzymes may reflect the differences in the amino acid ligands, especially the cysteine ligand, outside their evolutionarily conserved Mg(II)-binding active sites, which might indicate predominantly non-competitive or uncompetitive mechanism of the inhibition. The overall results suggest that inhibition of 8-oxo- dGTPases may be involved in the mechanisms of induction of the 8- oxoguanine lesion in DNA by the metal ions studied, especially the non- redox-active Cd(II) cation.   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