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   4004篇
  免费   381篇
  国内免费   21篇
耳鼻咽喉   64篇
儿科学   129篇
妇产科学   107篇
基础医学   626篇
口腔科学   137篇
临床医学   368篇
内科学   884篇
皮肤病学   101篇
神经病学   293篇
特种医学   122篇
外科学   548篇
综合类   130篇
一般理论   21篇
预防医学   302篇
眼科学   105篇
药学   222篇
中国医学   1篇
肿瘤学   246篇
  2023年   26篇
  2022年   42篇
  2021年   75篇
  2020年   38篇
  2019年   58篇
  2018年   79篇
  2017年   57篇
  2016年   48篇
  2015年   87篇
  2014年   95篇
  2013年   151篇
  2012年   199篇
  2011年   210篇
  2010年   116篇
  2009年   132篇
  2008年   218篇
  2007年   190篇
  2006年   172篇
  2005年   192篇
  2004年   155篇
  2003年   142篇
  2002年   148篇
  2001年   86篇
  2000年   110篇
  1999年   98篇
  1998年   48篇
  1997年   40篇
  1996年   32篇
  1995年   34篇
  1993年   25篇
  1992年   71篇
  1991年   61篇
  1990年   38篇
  1989年   49篇
  1988年   53篇
  1987年   51篇
  1986年   38篇
  1985年   47篇
  1984年   31篇
  1983年   36篇
  1981年   48篇
  1980年   32篇
  1979年   49篇
  1978年   46篇
  1977年   28篇
  1976年   38篇
  1975年   49篇
  1974年   52篇
  1973年   34篇
  1967年   24篇
排序方式: 共有4406条查询结果,搜索用时 0 毫秒
91.
92.
93.
The human leukemia cell line K562, derived from a patient with Philadelphia chromosome-positive chronic myelogenous leukemia, contains amplified c-abl oncogenes and unrearranged C lambda genes. Using in situ hybridization techniques, we have determined that the amplified c-abl and C lambda DNA sequences of K562 cells are both located on the same abnormal acrocentric marker chromosome, which may represent an altered Philadelphia chromosome.  相似文献   
94.
Protein carboxymethylase, an enzyme capable of methylating proteins and polypeptides, was purified from bovine pituitary. The anterior pituitary hormones, luteinizing hormone, follicle-stimulating hormone, adrenocorticotropic hormone, growth hormone, thyroid-stimulating hormone, and prolactin, were found to be substrates for this enzyme. The posterior pituitary hormones, oxytocin and vasopressin, did not serve as substrates. With luteinizing hormone as the substrate, protein carboxymethylase had a pH optimum near pH 5.5. A limiting K(m) of 1.47 muM for S-adenosyl-L-methionine was obtained with luteinizing hormone as the methyl acceptor. Possible roles of this enzyme in the posterior and anterior pituitary are discussed.  相似文献   
95.
BACKGROUND: During the past years, major advances in the management of upper gastrointestinal diseases have been achieved. The aim of this study was to determine if changes in indications for upper gastrointestinal endoscopy and endoscopic findings have occurred during the last 15 years in our area. METHODS: Indications for upper gastrointestinal tract endoscopy and endoscopy findings of patients who underwent upper endoscopy in years 1990, 1995, 2000, and 2005 in our department were compared. RESULTS: Over the 15-year period, the number of diagnostic endoscopies performed in our department in years 1990, 1995, 2000, and 2005 increased (953, 1245, 2350, and 2528, respectively). Acute upper gastrointestinal bleeding had become less frequent (40%, 42.8%, 19.7%, 14.3%, P<0.001), but dyspepsia (24.4%, 33.6%, 54.3%, 51.3%, P=0.002) and reflux (1.8%, 1.3%, 5.1%, 10.8%, P=0.005) more frequent indications for upper endoscopy. The endoscopic findings of duodenal ulcer (39.1%, 22.5%, 20.5%, 9.3%, P<0.001), gastric ulcer (15.9%, 8.3%, 5.7%, 4.6%, P=0.036) as well as erosive gastroduodenitis (35.6%, 22.2%, 15.3%, 4.7%, P<0.001) decreased, whereas that of reflux esophagitis (3.1%, 10.1%, 12%, 16%, P=0.034) increased. Moreover, the percentage of patients with negative endoscopy or minimal endoscopic findings (eg, nonerosive gastritis) increased (12.8%, 33.7%, 54.1%, 64.4%, P<0.001). CONCLUSIONS: In south-western Greece, dyspepsia and reflux as an indication for upper endoscopy have been increasing, whereas acute upper gastrointestinal bleeding has been decreasing. The finding of peptic ulcers at the upper gastrointestinal tract endoscopy has become significantly less frequent, while the percentage of patients with negative results of endoscopy seems to have been increasing rapidly.  相似文献   
96.
Nguyen P  Moisini I  Geiger TL 《Blood》2003,102(13):4320-4325
Recent preclinical and clinical trials have demonstrated the therapeutic potential of T lymphocytes redirected with genetically engineered T-cell receptor (TCR) surrogates against infected, cancerous, or autoreactive cells. These surrogate TCRs link a ligand-recognition domain to signaling regions from the TCR. We previously compared the function of surrogate TCRs that include TCR or TCR and CD28 signaling regions. We found that primary murine T cells modified to specifically target Kb-restricted CD8+ T cells using either Kb-zeta or Kb-CD28-zeta receptors had similar functional activities, although the CD28-zeta receptor showed a 2-fold to 4-fold decreased expression. We have now identified a previously unrecognized dileucine motif in the murine CD28 signaling domain that accounts for this reduced expression. Inactivation of this motif increased chimeric receptor surface expression 2- to 5-fold. T cells expressing the dileucine-mutated CD28-zeta chimeric receptor demonstrated enhanced proliferation, cytokine production, and cytolytic activities. Further, cells expressing this dileucine-mutated receptor were highly effective in eliminating antigen-specific CD8+ T lymphocytes in vivo. These results therefore identify a critical motif limiting the function of receptor-modified T lymphocytes, demonstrate that inactivation of this motif enhances chimeric receptor function, and illustrate a potential novel application of receptor-modified T lymphocytes in the induction of immune tolerance.  相似文献   
97.
The recent position paper of the European Society of Cardiology (ESC) on cardiovascular toxicity of cancer treatments has attracted considerable interest by healthcare professionals, since it is the first concrete help in the difficult task of monitoring and approaching cardiovascular side effects of anticancer treatments. The ESC expert opinion was not intended as a clinical practice guideline; however, it reports major cardiovascular complications grouped into nine categories, addressing current clinical strategies for prevention and mitigation. In this point of view, we discuss key challenges emerging from critical appraisal of the ESC position paper: (1) the wide spectrum of cardiovascular toxicities associated with oncological drugs, focusing on targeted agents, (2) managing strategies in patients with cardiac implantable devices, (3) the underappreciated (but emerging) immune-related cardiovascular toxicities of checkpoint inhibitors, which may also result in severe heart failure and fulminant myocarditis, (4) the evolving role of anticoagulation in oncology, and the evidence supporting (or not) the use of direct-acting oral anticoagulants in cancer-associated thrombosis.  相似文献   
98.
Both substance use disorder and HIV infection continue to affect many individuals. Both have untoward effects on the brain, and the two conditions often co-exist. In the brain, macrophages and microglia are infectable by HIV, and these cells are also targets for the effects of drugs of abuse, such as the psychostimulant methamphetamine. To determine the interaction of HIV and methamphetamine, we isolated microglia and brain macrophages from SIV-infected rhesus monkeys that were treated with or without methamphetamine. Cells were subjected to single-cell RNA sequencing and results were analyzed by statistical and bioinformatic analysis. In the animals treated with methamphetamine, a significantly increased proportion of the microglia and/or macrophages were infected by SIV. In addition, gene encoding functions in cell death pathways were increased, and the brain-derived neurotropic factor pathway was inhibited. The gene expression patterns in infected cells did not cluster separately from uninfected cells, but clusters comprised of microglia and/or macrophages from methamphetamine-treated animals differed in neuroinflammatory and metabolic pathways from those comprised of cells from untreated animals. Methamphetamine increases CNS infection by SIV and has adverse effects on both infected and uninfected microglia and brain macrophages, highlighting the dual and interacting harms of HIV infection and drug abuse on the brain.  相似文献   
99.
100.
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