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   4700篇
  免费   239篇
  国内免费   6篇
耳鼻咽喉   42篇
儿科学   203篇
妇产科学   70篇
基础医学   546篇
口腔科学   346篇
临床医学   331篇
内科学   697篇
皮肤病学   82篇
神经病学   246篇
特种医学   95篇
外科学   911篇
综合类   85篇
一般理论   4篇
预防医学   199篇
眼科学   140篇
药学   584篇
  1篇
中国医学   38篇
肿瘤学   325篇
  2023年   42篇
  2022年   101篇
  2021年   178篇
  2020年   104篇
  2019年   130篇
  2018年   166篇
  2017年   129篇
  2016年   154篇
  2015年   165篇
  2014年   197篇
  2013年   289篇
  2012年   419篇
  2011年   437篇
  2010年   200篇
  2009年   204篇
  2008年   250篇
  2007年   234篇
  2006年   185篇
  2005年   147篇
  2004年   140篇
  2003年   123篇
  2002年   127篇
  2001年   67篇
  2000年   47篇
  1999年   51篇
  1998年   23篇
  1997年   17篇
  1996年   26篇
  1995年   18篇
  1993年   11篇
  1992年   49篇
  1991年   44篇
  1990年   44篇
  1989年   42篇
  1988年   29篇
  1987年   39篇
  1986年   27篇
  1985年   25篇
  1984年   25篇
  1983年   25篇
  1981年   17篇
  1980年   10篇
  1979年   15篇
  1978年   10篇
  1977年   17篇
  1976年   16篇
  1975年   14篇
  1974年   24篇
  1973年   13篇
  1972年   11篇
排序方式: 共有4945条查询结果,搜索用时 15 毫秒
71.
Tritiated dopamine was used to label the dopamine receptor in membranes isolated from the rat corpus striatum. Scatchard analysis of displacement of [3H]dopamine by nonradioactive dopamine indicated the presence of two binding sites. The similarities in affinity, capacity, and drug specificity of the high-affinity site in the striatal membranes from rat and the binding site in the membranes from the calf caudate nucleus suggest that [3H]dopamine labels the same site in both species. In order to determine what conformation of dopamine is preferred at the dopamine receptor site, conformationally restricted analogs of dopamine--namely, the cis and trans 2-amino-1(3,4-dihydroxyphenyl)cyclobutane hydrochlorides--were tested for their affinity to the receptor. Compared to the cis conformation, the trans-restricted analogs had more affinity for the receptor site, indicating that dopamine probably interacts with the receptor in the trans conformation.  相似文献   
72.
Current models for targeted-tracking are discussed and shown to be inadequate as a means of understanding the combined task of tracking, as in the Drury’s paradigm, and having a final target to be aimed at, as in the Fitts’ paradigm. It is shown that the task has to be split into components that are, in general, performed sequentially and have a movement time component dependent on the difficulty of the individual component of the task. In some cases, the task time may be controlled by the Fitts’ task difficulty, and in others, it may be dominated by the Drury’s task difficulty. Based on an experiment carried out that captured movement time in combinations of visually controlled and ballistic movements, a model for movement time in targeted-tracking was developed.  相似文献   
73.
74.
The identification of the etiology of breast cancer is a crucial research issue for the development of an effective preventive and treatment strategies. Researchers are exploring the possible involvement of Mouse Mammary Tumor Virus (MMTV) in causing human breast cancer. Hence, it becomes very important to use a consistent positive control agent in PCR amplification based detection of MMTV-Like Sequence (MMTV-LS) in human breast cancer for accurate and reproducible results. This study was done to investigate the feasibility of using genomic DNA of MCF-7 breast cancer cells to detect MMTV-LS using PCR amplification based detection. MMTV env and SAG gene located at the 3′ long terminal repeat (LTR) sequences were targeted for the PCR based detection. No amplification was observed in case of the genomic DNA of MCF-7 breast cancer cells. However, the 2.7 kb DNA fragment comprising MMTV env and SAG LTR sequences yielded the products of desired size. From these results it can be concluded that Genomic DNA of MCF-7 cell is not a suitable choice as positive control for PCR or RT-PCR based detection of MMTV-LS. It is also suggested that plasmids containing the cloned genes or sequences of MMTV be used as positive control for detection of MMTV-LS.  相似文献   
75.
Psychiatric Quarterly - Patients who abscond from acute inpatient psychiatric wards put themselves and others at risks of variable nature and severity. There is a limited understanding of what...  相似文献   
76.
Ropinirole hydrochloride (RPN), a nonergot dopamine D2-agonist used in the management of Parkinson’s disease, has poor oral bioavailability (52%) due to extensive hepatic metabolism. The intent of present research work was aimed at design and statistical optimization of RPN-loaded poly (lactic-co-glycolic acid) (PLGA)-based biodegradable nanoparticles (NPs) surface modified using natural emulsifier, vitamin E (d-α-tocopheryl polyethylene glycol 1000 succinate [TPGS]) for direct nose-to-brain delivery in order to avoid hepatic first-pass metabolism, and improve therapeutic efficacy with sustained drug release. RPN-NPs were prepared by modified nanoprecipitation technique and optimized using 23 factorial design of experiment. The effect of polymer and emulsifier concentration was evaluated on particle size and entrapment efficiency (EE%). Formulation PL6 was considered as desirable with highest EE% (72.3?±?6.1%), PS (279.4?±?1.8?nm), zeta potential (?29.4?±?2.6?mV), and cumulative drug diffusion of 96.43?±?3.1% in 24?h. The ANOVA results for the dependent variables demonstrated that the model was significant (p value?<?0.05) for response variables. Histopathological study of optimized batch (PL6) demonstrated good retention of NPs with no severe signs of damage on the integrity of nasal mucosa. Differential scanning calorimetry revealed the absence of any chemical interaction between RPN, PLGA, and TPGS while SEM study confirmed spherical shape of optimized NPs. Accelerated stability studies of freeze-dried optimized batch demonstrated negligible change in the average PS and EE% after storage at 25?±?2?°C/60?±?5% (relative humidity (RH) for the period of three months. The promising results of optimized batch suggested practicability of investigated system for enhancement of bioavailability and brain targeting of CNS acting drugs like RPN.  相似文献   
77.
PurposeThe study is an audit of reporting dose and volume specifications as per the ICRU 58 for MUPIT-based interstitial brachytherapy in gynecological cancers. Correlation between total reference air kerma (TRAK) and isodose surface was also evaluated to understand the intensity of treatment in interstitial brachytherapy.Methods and MaterialsForty-two patients underwent HDR MUPIT-based interstitial brachytherapy 20 Gy in five fractions after EBRT during 2017–2019. Treated volume, high and low-dose regions, mean central dose, Dose Homogeneity Index (DHI), organ at risk doses, and TRAK values were computed.ResultsHigh-dose regions V150 mean was 12.4 cc and V200 was 4.58 cc; and low-dose region was 75.92 cc. The mean treated volume was 59.8 cc. The mean central dose was 3.7 Gy. DHI was 79%. The mean D2cm3 bladder and rectum were 2.9 Gy and 2.8 Gy. The mean TRAK was 0.16 cGy per fraction per hour at 1 m. TRAK values showed significant correlation with various isodose volumes (TRAK and V100: r = 0.943 p < 0.0005; and TRAK and V50: r = 0.953; p < 0.0005). A positive correlation was observed between TRAK and the number of needles (r = 0.746; p < 0.0005). At a median followup of 16 months, 4 of 42 patients (9.5%) had local recurrences.ConclusionsOur study shows compliance with ICRU 58 recommendations along with certain deviations. Local recurrence rate is acceptable. TRAK shows correlation with surface isodose in MUPIT-based brachytherapy and should to be evaluated in future studies.  相似文献   
78.

Background:

Organ transplantation is the most preferred treatment modality for end-stage organ diseases. The need for the transplants is higher than the availability. Prerequisites for the success of transplantation program include awareness and positive attitudes.

Aim:

To assess the perceptions and attitudes of the people seeking health care in tertiary care centers towards organ donation in Mangalore, India.

Settings and Design:

This cross-sectional study included 863 people seeking general healthcare as outpatients.

Materials and Methods:

Face to face interviews were carried out using pretested tools which included the socio demographic data. Data was analyzed using Statistical Package for Social Sciences version 11.5.

Results:

Overall, 59.6% participants showed the willingness to donate organs. Females (64.1%) and participants from upper socio economic status (62.7%) had higher willingness rates for organ donations. Hindus (63.6%) and Christians (63.3%) had higher willingness rates for organ donations than Muslims (38.2%). Also, 23.7% participants showed willingness to donate eyes and 33.6% wished to donate any organ after death. Most of the participants (67%) were aware that money should not be accepted for donating organs, and 58.1% were aware that it is an offence to accept any benefit for organ donations. Forty percent participants had perceived risks associated with organ donation. Regarding donor cards, 42.3% of the participants knew about it and 3.7% already possessed it.

Conclusion:

It is apparent from the study that though there was high level of awareness about organ donation, a high proportion of the participants did not have positive attitudes towards organ donation.  相似文献   
79.

Purpose

The aim of the study was to assess the distribution of accessory foramina in the mandibular body with computed tomography (CT).

Materials and methods

The CT images of the mandibular body in 300 subjects (183 females and 117 males aged between 12 and 85 years) were retrospectively analysed for the presence of accessory foramina. The buccal and lingual surfaces were examined by dividing them into anterior and posterior quadrants.

Results

Of the 300 subjects, 26 presented with accessory foramina on buccal posterior aspect and 70 subjects presented on buccal anterior aspect. Further, on the lingual posterior aspect, 132 subjects presented with accessory foramina and 59 subjects presented on lingual anterior aspect. Most of the subjects with accessory foramina in the buccal posterior, buccal anterior and lingual anterior regions had accessory foramina on other aspects of the mandible as well.

Conclusion

A substantial number of subjects presented with accessory foramina on the lingual posterior aspect when compared to other aspects. Nevertheless, the number of subjects with accessory foramina on other aspects of the mandible was considerable and cannot be ignored. It is suggested that when an accessory foramen is identified in an individual on a particular aspect of the mandibular body, it is highly probable that he will exhibit accessory foramina on other aspects as well.  相似文献   
80.
Virus Genes - Citrus yellow mosaic badnavirus (CMBV) causes mosaic disease in all economically important citrus cultivars of India, with losses reaching up to 70%. CMBV belongs to the genus...  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