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   2040篇
  免费   169篇
  国内免费   5篇
耳鼻咽喉   13篇
儿科学   98篇
妇产科学   33篇
基础医学   316篇
口腔科学   69篇
临床医学   146篇
内科学   507篇
皮肤病学   85篇
神经病学   126篇
特种医学   60篇
外科学   226篇
综合类   30篇
预防医学   129篇
眼科学   48篇
药学   171篇
中国医学   18篇
肿瘤学   139篇
  2023年   15篇
  2022年   39篇
  2021年   93篇
  2020年   66篇
  2019年   61篇
  2018年   78篇
  2017年   54篇
  2016年   69篇
  2015年   63篇
  2014年   97篇
  2013年   119篇
  2012年   138篇
  2011年   138篇
  2010年   81篇
  2009年   67篇
  2008年   102篇
  2007年   109篇
  2006年   88篇
  2005年   67篇
  2004年   55篇
  2003年   54篇
  2002年   32篇
  2001年   32篇
  2000年   27篇
  1999年   32篇
  1998年   24篇
  1997年   16篇
  1996年   18篇
  1995年   17篇
  1993年   11篇
  1992年   30篇
  1991年   32篇
  1990年   22篇
  1989年   21篇
  1988年   18篇
  1987年   11篇
  1986年   11篇
  1985年   18篇
  1984年   15篇
  1983年   10篇
  1982年   9篇
  1981年   16篇
  1979年   10篇
  1978年   12篇
  1977年   17篇
  1976年   15篇
  1975年   8篇
  1974年   12篇
  1973年   9篇
  1969年   8篇
排序方式: 共有2214条查询结果,搜索用时 15 毫秒
1.
Background: Ingestion of coins is a common clinical problem in children. Many of the coins are ferromagnetic and can be retrieved with the help of a magnet. We describe the use of a novel endoscopic accessory for removing ferromagnetic coins. Material and methods: Two magnet discs of 1.5 cm diameter were joined to a 200 cm steel wire of 0.75 mm thickness with a terminal 5 cm spring. A Teflon tube (160 cm, 7 F) was used along with this instrument as a sleeve. The use of this accessory was analyzed prospectively in subjects presenting with a history of coin ingestion. The time taken for removal of coins, complications during the procedure and failure rate was noted. Effect of the magnet on cardiac rhythm was also noted during the procedure. Results: A total of 55 children (mean age 5.1 ± 2.3 years) with coin ingestion presented over a period of 1 year. Forty‐four coins were ferromagnetic. All ferromagnetic coins were removed successfully. Mean time for removal was 68 ± 22 s. No complications were encountered. Conclusion: The novel magnetic instrument is precise, safe and quick for the removal of ferromagnetic coins under direct vision.  相似文献   
2.
An international collaborative study was carried out to determine the suitability of the current WHO II-IX-X concentrate standard, 84/681, for assigning potency to the more highly purified factor IX concentrates. Three Coagulation Factor IX (Human) preparations and one Factor IX Complex preparation were assayed by the one stage method against WHO 84/681 following predilution to 1.0 u/ml in buffer, 1% albumin, or factor IX deficient plasma. There were no cases of non-parallelism between any of the preparations and the current WHO standard. Predilution of the Coagulation Factor IX (Human) preparations in 1% albumin or factor IX deficient plasma gave similar potency values. Predilution in buffer gave significantly lower (p less than 0.01) potency values. For the Factor IX Complex preparation, potency estimates were significantly different (p less than 0.01) with each prediluent. The overall precision was similar within each predilution for all preparations with predilution in buffer being less precise than predilution in albumin or in deficient plasma. WHO standard 84/681 appears to be a suitable standard for the potency determination of the more highly purified factor IX preparations. Predilution in 1% albumin or factor IX deficient plasma is recommended as they give equivalent results with the least variability.  相似文献   
3.
Twenty-four cases of trichotillomania attending psychiatry outpatient department and child guidance clinic at Kalawati Saran Children's and Smt Sucheta Kriplani Hospitals over a period of 2 years from July, 1985 to November 1987 were studied. Females (66.7%) outnumbered the males (33.3%). Majority of cases belonged to age group 6-10 years (54.2%) and nuclear family (68.5%). Nail-biting (25.0%) was the commonest associated neurotic trait, followed by enuresis (20.9%), temper-tantrum (12.5%), etc. A past history of hysterical fits and neurotic depression was found in 3 cases (12.5%) and 2 cases (8.3%) respectively. Family history of neurosis was seen in mothers and fathers of 20.9% and 12.5% cases respectively. Trichobezoars and trichophytobezoars were found in 6 cases (25.0%) and 3 cases (12.5%) respectively. Majority of patients of trichobezoars presented with vague complaints like heaviness in the stomach (55.6%), inability to gain weight (44.4%), etc, while 22.2% cases were asymptomatic and detected only on screening.  相似文献   
4.
The effects of selected modulators of GABAergic transmission, either alone or in combination, were tested for their potency on the seizure pattern and mortality induced by convulsant drugs in rat. Pentobarbital and diazepam were effective against both tonic and clonic seizure components induced by bicuculline and picrotoxin. The anticonvulsant profile of ethanol closely resembled that of pentobarbital. Pentobarbital, diazepam and ethanol did not modify seizures induced by strychnine. In contrast, progabide, a central gamma-aminobutyric acid (GABA) receptor agonist, caused significant protection only against convulsions induced by strychnine and its lethality, but did not protect against seizures induced by bicuculline or picrotoxin. Data on interaction of drugs with subprotective doses of these agents clearly demonstrated potentiation of the anticonvulsant actions of these modulators. Thus, seizures induced by bicuculline were more sensitive to the inhibition by pentobarbital in combination with diazepam or ethanol, while pentobarbital with progabide was equally effective against convulsions induced by GABA antagonists. Diazepam, in combination with progabide, blocked only convulsions induced by picrotoxin. Ethanol, in combination with either pentobarbital or with diazepam, was effective against all the three convulsant drugs. These results are consistent with the concept that drugs which facilitate GABAergic transmission are effective against seizures related to an impairment of GABA transmission. Further, the present data indicate that tonic seizures are more susceptible to the actions of drugs than the clonic component. Smaller doses of these drugs, alone or in combination, modified the seizure patterns and mortality, whereas at larger doses, the possible involvement of a nonspecific depressant action cannot be ruled out.  相似文献   
5.
Behavioural studies were conducted on a random sample of 38 glass bangle workers engaged in various occupations and exposed to high ambient temperature (38.2 +/- 3.4 degrees C) and radiant heat (46.2 +/- 5.1 degrees C) during their work in the glass bangle industries at Firozabad, India. Twenty-two control subjects of similar age and socio-economic status unexposed to heat during their work were also studied for comparison. The digit span test, digit symbol test, Bourdon-Wiersma vigilance test, flicker fusion test and Maudsley personality inventory (MPI) were used to assess the behavioural changes induced by the existing heat stress. The mean scores of immediate memory were much lower in the exposed population than in the controls thereby indicating impairment of immediate memory in the study group. The visuo-motor coordination and vigilance were also significantly affected. Visual perception showed a downward trend among the glass bangle workers, although the MPI test indicated no personality changes.  相似文献   
6.
7.

Background  

Sustained use of antiretroviral therapy has been consistently shown to be one of the primary predictors of long-term effectiveness. Switching and discontinuation reflect patient and provider decisions that may limit future treatment options. In this study, we utilize data reported at semi-annual study visits from three prospective cohort studies, the AIDS Link to IntraVenous Exposure (ALIVE), the Women's Interagency HIV Study (WIHS), and the Multicenter AIDS Cohort Study (MACS), to investigate determinants of HAART modification with a particular focus on reported injection drug use (IDU).  相似文献   
8.
A novel modification of conventional video imaging techniques has been developed to determine the velocity of red blood cells (RBCs), which offers compatibility with existing video-based methods for determining blood oxygenation and hemoglobin concentration. Traditional frame-by-frame analysis of video recordings limits the maximum velocity that can be measured for individual cells in vivo to about 2 mm/s. We have extended this range to about 20 mm/s, by electronic shuttering of an intensified charge-coupled device camera to produce multiple images of a single RBC in the same video frame. RBCs were labeled with fluorescein isothiocyanate and the labeled cells (FRBCs) were used as probes to determine RBC velocities in microvessels of the hamster retractor muscle. Velocity was computed as the product of the distance between centroids of two consecutive image positions of a FRBC and the shuttering frequency of the camera intensifier. In vitro calibrations of the system using FRBC and Sephadex beads coated onto a rotating disk yielded an average coefficient of variation of about 6%. Flow conservation studies at bifurcations indicated that the maximum diameter of microvessels below which all the FRBCs in the lumen could be detected was 50 m. The technique was used to estimate mean-FRBC velocity distributions in vessels with diameters ranging from 8 to 50 m. The mean-FRBC velocity profiles were found to be blunter than would be expected for Poiseuille flow. Single FRBCs tracked along an unbranched arteriole exhibited significant temporal variations in velocity. © 1999 Biomedical Engineering Society. PAC99: 8719Tt, 8717Jj, 4279Pw, 8780Tq, 8719Ff, 4230Va, 0705Pj  相似文献   
9.
10.
This investigation dealt with 226 strains (1 isolate/patient) of Mycobacterium tuberculosis isolated in the French West Indies and French Guiana over a three-year period (1994-1996). The genotypic diversity of the isolates was investigated using various molecular markers; essentially two PCR-based rapid methods, namely spoligotyping and double-repetitive-element (DRE)-PCR, as well as three restriction fragment length polymorphism (RFLP)-based methods, namely IS6110-RFLP, DR-RFLP and PGRS-RFLP. Out of 226 isolates investigated, a total of 166 isolates were distributed in 31 spoligotype-defined clusters containing 2-31 strains, which corresponded to a rate of 73% of primary clustering. After secondary typing with DRE-PCR, IS6110-RFLP, DR-RFLP and/or PGRS-RFLP, molecular clonality was established for 73 isolates organised in 25 clusters (32% of clustered isolates). Considering one reactivation case per cluster, the rate of recent transmission was estimated to a minimal rate of 21%, however the available epidemiologic information led to the positive conclusion for only 14% of cases. The data obtained demonstrated the presence of common genotypes of M. tuberculosis among the three overseas French territories, i.e. Guadeloupe, Martinique and French Guiana. The results obtained during this retrospective study clearly indicate the importance of future prospective epidemiological investigations around the clustered cases of tuberculosis, so as to detect the persisting foci of endemic disease and characterize the chain of transmission as well as the subpopulations which are at an increased risk of contracting and/or propagating the disease. Last but not least, the present study also deals with a first phylogenetic approach of M. tuberculosis based on a comparison of the spoligotyping results obtained locally with those reported elsewhere in the world.  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