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   9665篇
  免费   572篇
  国内免费   65篇
耳鼻咽喉   76篇
儿科学   305篇
妇产科学   116篇
基础医学   1123篇
口腔科学   438篇
临床医学   862篇
内科学   2278篇
皮肤病学   229篇
神经病学   784篇
特种医学   462篇
外科学   1625篇
综合类   18篇
一般理论   1篇
预防医学   487篇
眼科学   92篇
药学   448篇
中国医学   11篇
肿瘤学   947篇
  2023年   122篇
  2022年   93篇
  2021年   364篇
  2020年   207篇
  2019年   321篇
  2018年   399篇
  2017年   265篇
  2016年   249篇
  2015年   298篇
  2014年   391篇
  2013年   462篇
  2012年   666篇
  2011年   732篇
  2010年   424篇
  2009年   390篇
  2008年   616篇
  2007年   597篇
  2006年   568篇
  2005年   558篇
  2004年   504篇
  2003年   452篇
  2002年   368篇
  2001年   166篇
  2000年   135篇
  1999年   118篇
  1998年   55篇
  1997年   62篇
  1996年   49篇
  1995年   43篇
  1994年   39篇
  1993年   37篇
  1992年   57篇
  1991年   46篇
  1990年   42篇
  1989年   42篇
  1988年   38篇
  1987年   34篇
  1986年   34篇
  1985年   26篇
  1984年   22篇
  1983年   23篇
  1982年   18篇
  1980年   11篇
  1979年   17篇
  1978年   11篇
  1977年   16篇
  1975年   14篇
  1974年   12篇
  1973年   13篇
  1968年   12篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
2.
BackgroundThe present analysis aims to compare the impact of 18F-fluorocholine (18F-choline) and gallium-68 prostate-specific membrane antigen (68Ga-PSMA) positron emission tomography (PET)-computed tomography (CT)–guided metastases-directed therapies (MDTs) in patients with castration-sensitive oligorecurrent prostate cancer (PC).Materials and MethodsInclusion criteria were: (1) histologically proven prostate adenocarcinoma; (2) evidence of biochemical relapse after primary tumor treatment; (3) ≤ 3 hypermetabolic oligorecurrent lesions detected by 18F-choline or 68Ga-PSMA PET-CT; (4) PET-CT imaging performed in a single nuclear medicine department; (5) patients treated with upfront stereotactic body radiotherapy (SBRT) without hormone therapy; and (6) SBRT delivered with a dose per fraction ≥ 5 Gy. In the case of oligoprogression (≤ 3 lesions outside the previous RT field) after MTD, a further course of SBRT was proposed; otherwise, androgen deprivation therapy (ADT) was administered.ResultsA total of 118 lesions in 88 patients were analyzed. Forty-four (50%) patients underwent 68Ga-PSMA PET-guided SBRT, and the remaining underwent choline PET-based SBRT. The median follow-up was 25 months (range, 5-87 months) for the entire cohort. Overall survival and local control were both 100%. Distant progression occurred in 48 (54.5%) patients, for a median distant progression-free survival of 22.8 months (range, 14.4-28.8 months). The median pre-SBRT prostate-specific antigen was 2.04 ng/mL in the choline PET cohort and 0.58 ng/mL in the PSMA-PET arm. Disease-free survival rates were 63.6% and 34%, respectively, in the 68Ga-PSMA and choline PET group (P = .06). The ADT administration rate was higher after choline-PET–guided SBRT (P = .00) owing to the higher incidence of polymetastatic disease after first-course SBRT compared with 68Ga-PSMA-based SBRT.ConclusionIn the setting of oligorecurrent castration-sensitive PC, PSMA-PET-guided SBRT produced a higher rate of ADT-free patients when compared with the 18F-choline-PET cohort. Randomized trials are advocated.  相似文献   
3.
An evolutionary hypothesis explaining failure of regeneration among vertebrates is presented. Regeneration derives from postembryonic processes present during the life cycles of fish and amphibians that include larval and metamorphic phases with broad organ reorganizations. Developmental programs imprinted in their genomes are re-utilized with variations also in adults for regeneration. When vertebrates colonized land adopting the amniotic egg, some genes driving larval changes, and metamorphosis were lost and new genes evolved, further limiting regeneration. These included neural inhibitors for maintaining complex nervous systems, behavior and various levels of intelligence, and adaptive immune cells. The latter, that in anamniotes are executioners of metamorphic reorganization, became intolerant to embryonic-oncofetal-antigens impeding organ regeneration, a process that requires de-differentiation of adult cells and/or expansion of stem cells where these early antigens are formed. The evolution of terrestrial lifecycles produced vertebrates with complex bodies but no longer capable to regenerate their organs, mainly repaired by regengrow. Efforts of regenerative medicine to improve healing in humans should determine the diverse developmental pathways evolved between anamniotes and amniotes before attempting genetic manipulations such as the introduction of “anamniote regenerative genes” in amniotes. This operation may determine alteration in amniote developmental programs leading to teratomes, cancer, or death.  相似文献   
4.
5.
The cytomorphologic evaluation of serous cavity specimens can quickly determine the cause of an effusion as well as the presence or absence of a neoplastic process. Ancillary tests such as immunohistochemistry and fluorescence in situ hybridization are frequently used to help to definitively identify malignant cells, determine a site of origin, and distinguish between malignant and reactive mesothelial proliferations. In recent years, microRNAs (miRNAs) have been increasingly evaluated in cytologic specimens, including those from serous cavities. The examination of miRNA is attractive because of the stability of miRNA in such specimens and data suggesting that miRNA can provide prognostic and therapeutic information in addition to its role in diagnosis. Furthermore, miRNAs exist within extracellular exosomes, and this allows for their analysis in specimens that contain only rare malignant cells, degenerated cells, or obscuring components. This review discusses the technical aspects of specimen processing for miRNA analysis, recent studies of miRNA expression in malignant serous cavity specimens, and the potential importance of miRNA expression analysis for serous cavity specimens in the near future.  相似文献   
6.
7.
8.

Background

Syphilis is resurgent in many developed countries and still prevalent in developing nations. Current and future control campaigns would benefit from the development of a vaccine, but although promising vaccine candidates were identified among the putative surface-exposed integral outer membrane proteins of the syphilis spirochete, immunization experiments in the rabbit model using recombinant antigens have failed to fully protect animals upon infectious challenge. We speculated that such recombinant immunogens, purified under denaturing conditions from Escherichia coli prior to immunization might not necessarily harbor their original structure, and hypothesized that enhanced protection would result from performing similar immunization/challenge experiments with native antigens.

Methods

To test our hypothesis, we engineered non-infectious Borrelia burgdorferi strains to express the tp0897 (tprK) and tp0435 genes of Treponema pallidum subsp. pallidum and immunized two groups of rabbits by injecting recombinant strains intramuscularly with no adjuvant. TprK is a putative integral outer membrane protein of the syphilis agent, while tp0435 encodes the highly immunogenic T. pallidum 17-kDa lipoprotein, a periplasmic antigen that was also shown on the pathogen surface. Following development of a specific host immune response to these antigens as the result of immunization, animals were challenged by intradermal inoculation of T. pallidum. Cutaneous lesion development was monitored and treponemal burden within lesions were assessed by dark-field microscopy and RT-qPCR, in comparison to control rabbits.

Results

Partial protection was observed in rabbits immunized with B. burgdorferi expressing TprK while immunity to Tp0435 was not protective. Analysis of the humoral response to TprK antigen suggested reactivity to conformational epitopes.

Conclusions

Immunization with native antigens might not be sufficient to obtain complete protection to infection. Nonetheless we showed that non-infectious B. burgdorferi can be an effective carrier to deliver and elicit a specific host response to T. pallidum antigens to assess the efficacy of syphilis vaccine candidates.  相似文献   
9.
10.
«Effectiveness of the measures aimed at containing Sars-cov-2 virus spreading in work settings: a survey in companies based in the Veneto region of Italy».Introduction:During the Sars-Cov-2 pandemic, occupational health physicians worked to respond to different needs of workers, employers, and health authorities. In collaboration with the Prevention Department of the Veneto region of Italy, a survey was promoted in nine manufacturing companies in the province of Padua, to investigate the prevalence of asymptomatic SarsCov-2 virus and the immunological status of 1,267 workers.Scope:The study was aimed at verifying the effectiveness of measures to contain the virus spread among workers in the workplace as required by the agreement between the social partners signed on March 14, 2020.Methods:The survey was carried out at workplaces by trained health physicians and almost all company workers enrolled on a voluntary basis. Each worker was tested for viral RNA using nasopharyngeal swab and for IgM and IgG antibodies by drawing venous or capillary blood, according to the availability of tests at that difficult period.Results:Swab-positive workers were 0.3%, and subjects with positive serological tests were 1.6% of the total workers examined.Discussion:The diagnostic test is based on the search for viral RNA through nasopharyngeal swab. To evaluate the immunological status of workers the CLIA or Elisa quantitative serological test should be preferred. Measures to contain the virus spreading at the workplace seem to be effective, as working settings do not entail any additional risk of SarsCov-2 infection.Key words: COVID-19, epidemiology, prevention at workplace  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