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   7589篇
  免费   592篇
  国内免费   28篇
耳鼻咽喉   114篇
儿科学   262篇
妇产科学   273篇
基础医学   1088篇
口腔科学   117篇
临床医学   915篇
内科学   1299篇
皮肤病学   131篇
神经病学   749篇
特种医学   195篇
外科学   742篇
综合类   58篇
一般理论   10篇
预防医学   876篇
眼科学   157篇
药学   492篇
中国医学   33篇
肿瘤学   698篇
  2024年   13篇
  2023年   57篇
  2022年   93篇
  2021年   205篇
  2020年   162篇
  2019年   195篇
  2018年   184篇
  2017年   145篇
  2016年   192篇
  2015年   190篇
  2014年   298篇
  2013年   378篇
  2012年   594篇
  2011年   568篇
  2010年   332篇
  2009年   325篇
  2008年   520篇
  2007年   501篇
  2006年   473篇
  2005年   438篇
  2004年   456篇
  2003年   450篇
  2002年   388篇
  2001年   63篇
  2000年   29篇
  1999年   64篇
  1998年   90篇
  1997年   77篇
  1996年   51篇
  1995年   58篇
  1994年   57篇
  1993年   53篇
  1992年   38篇
  1991年   33篇
  1990年   37篇
  1989年   29篇
  1988年   20篇
  1987年   19篇
  1986年   14篇
  1985年   25篇
  1984年   27篇
  1983年   18篇
  1982年   24篇
  1981年   22篇
  1978年   17篇
  1975年   13篇
  1973年   19篇
  1972年   19篇
  1971年   14篇
  1970年   11篇
排序方式: 共有8209条查询结果,搜索用时 15 毫秒
991.
Osteoarticular mycoses due to non-Aspergillus moulds are uncommon and challenging infections.A systematic literature review of non-Aspergillus osteoarticular mycoses was performed using PUBMED and EMBASE databases from 1970 to 2013.Among 145 patients were 111 adults (median age 48.5 [16–92 y]) and 34 pediatric patients (median age 7.5 [3–15 y]); 114 (79.7%) were male and 88 (61.9%) were immunocompromised. Osteomyelitis was due to direct inoculation in 54.5%. Trauma and puncture wounds were more frequent in children (73.5% vs 43.5%; P = 0.001). Prior surgery was more frequent in adults (27.7% vs 5.9%; P = 0.025). Vertebral (23.2%) and craniofacial osteomyelitis (13.1%) with neurological deficits predominated in adults. Lower limb osteomyelitis (47.7%) and knee arthritis (67.8%) were predominantly seen in children. Hyalohyphomycosis represented 64.8% of documented infections with Scedosporium apiospermum (33.1%) and Lomentospora prolificans (15.8%) as the most common causes. Combined antifungal therapy and surgery was used in 69% of cases with overall response in 85.8%. Median duration of therapy was 115 days (range 5–730). When voriconazole was used as single agent for treatment of hyalohyphomycosis and phaeohyphomycosis, an overall response rate was achieved in 94.1% of cases.Non-Aspergillus osteoarticular mycoses occur most frequently in children after injury and in adults after surgery. Accurate early diagnosis and long-course therapy (median 6 mo) with a combined medical-surgical approach may result in favorable outcome.  相似文献   
992.
Clinical therapy with T cells shows promise for cancer patients, but is currently challenged by incomplete responses and tumor relapse. The exact mechanisms that contribute to tumor relapse remain largely unclear. Here, we treated mouse melanomas with T cell receptor-engineered T cells directed against a human peptide-major histocompatibility complex antigen in immune-competent mice. T cells resulted in significant tumor regression, which was followed by relapse in about 80–90% of mice. Molecular analysis revealed that relapsed tumors harbored nonmutated antigen genes, not silenced by promoter methylation, and functionally expressed surface antigen at levels equal to nontreated tumors. Relapsed tumors resisted a second in vivo T cell treatment, but regained sensitivity to T cell treatment upon retransplantation in mice. Notably, relapsed tumors demonstrated decreased levels of CD8 T cells and monocytes, which were substantiated by downregulated expression of chemoattractants and adhesion molecules. These observations were confirmed when using T cells specific for a less immunogenic, endogenous mouse melanoma antigen. We conclude that tumors, when exposed to T cell treatment, can relapse without loss of antigen and develop a milieu that evades recruitment of effector CD8 T cells. Our findings support the concept to target the tumor milieu to aid T cell therapy in limiting tumor relapse  相似文献   
993.
Aseptic technique includes the use of sterile surgical gloves for survival surgeries in rodents to minimize the incidence of infections. Exam gloves are much less expensive than are surgical gloves and may represent a cost-effective, readily available option for use in rodent surgery. This study examined the effectiveness of surface disinfection of exam gloves with 70% isopropyl alcohol or a solution of hydrogen peroxide and peracetic acid (HP–PA) in reducing bacterial contamination. Performance levels for asepsis were met when gloves were negative for bacterial contamination after surface disinfection and sham ‘exertion’ activity. According to these criteria, 94% of HP–PA-disinfected gloves passed, compared with 47% of alcohol-disinfected gloves. In addition, the effect of autoclaving on the integrity of exam gloves was examined, given that autoclaving is another readily available option for aseptic preparation. Performance criteria for glove integrity after autoclaving consisted of: the ability to don the gloves followed by successful simulation of wound closure and completion of stretch tests without tearing or observable defects. Using this criteria, 98% of autoclaved nitrile exam gloves and 76% of autoclaved latex exam gloves met performance expectations compared with the performance of standard surgical gloves (88% nitrile, 100% latex). The results of this study support the use of HP–PA-disinfected latex and nitrile exam gloves or autoclaved nitrile exam gloves as viable cost-effective alternatives to sterile surgical gloves for rodent surgeries.Abbreviations: HP–PA, hydrogen peroxide and peracetic acidThe Guide for the Care and Use of Laboratory Animals (the Guide) states that “general principles of aseptic technique should be followed for all survival surgical procedures.”9‘Aseptic technique’ refers to practices that reduce microbial contamination to the lowest possible practical level and includes: preparation of the patient; preparation of the surgeon including decontaminated surgical attire, surgical scrub, and sterile surgical gloves; sterilization of instruments, supplies, and implanted materials; and careful tissue handling during surgery to reduce the likelihood of infection. The Guide also states that “The species of animal may influence the manner in which principles of aseptic technique are achieved.”9 Therefore, although aseptic technique should be followed for survival surgeries in rodents, flexibility exists in the means by which asepsis is achieved. Aseptic approaches that are more economical or efficient yet maintain performance standards should be acceptable to the IACUC overseeing the animal care program. The recommendation to wear sterile surgical gloves for survival surgeries in rodents exists to limit contamination of the surgical site by bacteria on the surgeon''s hands and thus reduce the likelihood of a postsurgical infection. Under the Association for Practitioners in Infection Control guidelines, sterilization is defined as “the complete elimination or destruction of all forms of microbial life.”19-21 However, many laboratory workers fail to wear the recommended type of gloves for rodent surgery, primarily due to the high cost of sterile surgical gloves.4The purpose of the current study was to evaluate the performance of more economical and efficient alternatives to sterile surgical gloves for use in rodent survival surgery. The alternatives chosen were surface disinfection with 70% alcohol, HP–PA, and autoclaving for preparation of standard nitrile and latex exam gloves. We evaluated latex and nitrile exam gloves because both are commonly available in the laboratory. Disinfectants are readily available in most animal use areas, inactivate most pathogenic microorganisms, and therefore represent a convenient option for aseptic glove preparation for rodent survival surgeries.20 Isopropyl alcohol (70%) is used as an antiseptic for a variety of procedures in a medical setting including injection site preparation and as part of surgical site preparation. The Guide, however, states that “alcohol is neither a sterilant nor a high-level disinfectant.”9 Alcohol is classified as an intermediate-level disinfectant, meaning that it does not kill bacterial spores or hydrophilic viruses.17 Nonetheless, alcohols at concentrations ranging from 60% to 90% are reported to have excellent microbicidal properties2 and significantly reduce the microbial load on contaminated surfaces,7 hands,15,17,18, 22 and gloves inoculated with test organisms.5 A recent study found that soaking the fingertips of sterile surgical gloves in 70% isopropyl alcohol for 30 s between 5 serial mouse laparotomies effectively disinfected the gloves and prevented bacterial contamination.10 Because unused exam gloves presumably have low levels of bacterial contamination, alcohol might render them aseptic.HP–PA solutions are common disinfectants within the animal vivarium for the disinfection of biosafety cabinets and gloves when working with SPF rodents. A solution comprising 1.00% hydrogen peroxide and 0.08% peracetic acid is considered to be a chemical sterilant suitable for use on critical items that come into contact with sterile patient tissues, as in surgery.21 Product availability to animal users and use applications make HP–PA solution a reasonable choice for exam glove disinfection.In addition to chemical disinfection of exam gloves, another readily available option in most animal facilities is steam sterilization in an autoclave. The surgical instruments used for rodent surgery are commonly prepared by using autoclaving, and the addition of standard exam gloves to the surgical pack is another possible alternative to sterile surgical gloves for rodent surgeries. The existing reports on autoclaving of medical gloves date back to the 1960s and refer to reusable surgical gloves. These studies found that autoclaving methods made the gloves unusable or increased breakage;6,14 however ,glove materials, manufacturing practices, and quality control criteria have changed greatly since then,23and the most recent updates to test procedures and acceptance criteria for medical gloves in the United States were made in 2006.3 The gloves we selected for evaluation conform to industry standards regarding leaks and visual defects, according to the manufacturer.For this study, we hypothesized that surface disinfection of exam gloves with 70% isopropyl alcohol or HP–PA solution would effectively decrease microbial contamination of exam gloves to a level equivalent to that of sterile surgical gloves and that the disinfection process would not predispose the gloves to contamination from the surgeon''s hands during use. In addition, we hypothesized that autoclaving of exam gloves would have a detrimental effect on performance compared with that of sterile surgical gloves and that autoclaving could render exam gloves unwearable, cause defects in the gloves, or increase the porosity of the glove materials.  相似文献   
994.
The α-subunit is common to the heterodimeric glycoprotein hormones and has been highly conserved throughout vertebrate evolution. In an effort to determine if wild-type and engineered human α analogs can serve as agonists or antagonists to the human thyroid-stimulating hormone (TSH) receptor (TSHR), a potent α mutant, obtained by replacing four amino acid residues with lysine (α4K), was assayed and compared with the wild-type α-subunit. When added to CHO cells expressing TSHR, α4K, and to a very limited extent the fused homodimer, α4K-α4K, but not α, exhibited ago-nistactivity as judged by cAMP production. When yoked to TSHR to yield fusion proteins, neither α, α4K, α-α, nor α4K-α4K activated TSHR, although yoked α4K and α4K-α4K were weak inhibitors of TSH binding to TSHR. The yoked subunit-receptor complexes were, however, functional as evidenced by increased cAMP production in cells co-expressing human TSHβ and α-TSHR, α4K-TSHR, α-α-TSHR, and α4K-α4K-TSHR. These results demonstrate that agonists to TSHR can be obtained with α-subunit analogs and suggest that rational protein engineering may lead to more potent α-based derivatives. The differences found between the experimental paradigms of adding free α analogs to TSHR and covalent attachment are attributed to conformational constraints imposed by fusion of the α-subunit analog and receptor, and may suggest an important role for a free (C-terminal) α-carboxyl in the absence of the β-subunit.  相似文献   
995.
996.
997.
998.
999.
Journal of Assisted Reproduction and Genetics - Excess embryos transferred (ET) (> plurality at birth) and fetal heartbeats (FHB) at 6 weeks’ gestation are associated with reductions...  相似文献   
1000.
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