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:      
  示例: 沙坡头地区,人工植被区,变化  检索词用空格隔开表示必须包含全部检索词,用“,”隔开表示只需满足任一检索词即可!
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   2203篇
  免费   57篇
  国内免费   3篇
耳鼻咽喉   12篇
儿科学   127篇
妇产科学   18篇
基础医学   345篇
口腔科学   47篇
临床医学   189篇
内科学   363篇
皮肤病学   29篇
神经病学   145篇
特种医学   75篇
外科学   276篇
综合类   35篇
一般理论   3篇
预防医学   114篇
眼科学   72篇
药学   231篇
  1篇
中国医学   5篇
肿瘤学   176篇
  2024年   10篇
  2022年   23篇
  2021年   57篇
  2020年   29篇
  2019年   45篇
  2018年   53篇
  2017年   30篇
  2016年   57篇
  2015年   58篇
  2014年   77篇
  2013年   94篇
  2012年   145篇
  2011年   150篇
  2010年   89篇
  2009年   70篇
  2008年   120篇
  2007年   93篇
  2006年   106篇
  2005年   92篇
  2004年   74篇
  2003年   83篇
  2002年   71篇
  2001年   58篇
  2000年   49篇
  1999年   63篇
  1998年   33篇
  1997年   11篇
  1996年   11篇
  1995年   10篇
  1992年   28篇
  1991年   21篇
  1990年   25篇
  1989年   31篇
  1988年   14篇
  1987年   16篇
  1986年   12篇
  1985年   19篇
  1984年   14篇
  1983年   12篇
  1982年   10篇
  1980年   13篇
  1976年   9篇
  1975年   12篇
  1974年   15篇
  1973年   12篇
  1971年   14篇
  1970年   11篇
  1969年   10篇
  1968年   15篇
  1966年   13篇
排序方式: 共有2263条查询结果,搜索用时 0 毫秒
51.
52.
53.
  总被引:1,自引:1,他引:0       下载免费PDF全文
Transfusion of red blood cells (RBCs) into patients with anti-donor RBC antibodies (crossmatch-incompatible transfusion) can result in lethal antibody-mediated hemolysis. Less well appreciated is the ability of anti-RBC antibodies to specifically remove their target antigen from donor RBCs without compromising cell survival or adversely affecting the transfusion recipient. In an effort to elucidate the mechanistic details of this process, we describe the first animal model of nonhemolytic antibody-induced RBC antigen loss. RBCs from transgenic mHEL mice express surface hen egg lysozyme (HEL) as a transmembrane protein. Transfusion of mHEL RBCs into mice immunized with HEL results in selective loss of HEL antigen from donor RBCs without affecting other blood group antigens or reducing the circulatory life span of the transfused RBCs. While this process does not require the presence of a spleen, it requires both anti-RBC immunoglobulin G (IgG) antibodies and the FcgammaIII receptor. These studies provide mechanistic insight into the phenomenon of antigen loss during incompatible transfusion in humans.  相似文献   
54.
    
BACKGROUND: Alcohol (EtOH) alters the plasma and tissue content of insulin-like growth factor (IGF)-I, an important anabolic hormone. However, the bioavailability and bioactivity of IGF-I can also be modulated by changes in soluble proteins that bind IGF-I (IGFBPs). The purpose of the present study was to determine whether EtOH intoxication in rats alters the plasma concentration and tissue mRNA content of various IGFBPs. Based on initial results subsequent studies were performed to assess potential mechanisms by which EtOH increased IGFBP-1. METHODS: Rats were administered EtOH (75 mmol/kg) and blood and tissues collected at various times thereafter. Separate groups of rats were also pretreated with 4-methylpyrazole (4-MP; alcohol dehydrogenase inhibitor), cyanamide (inhibitor of acetaldehyde metabolism), RU486 (glucocorticoid receptor antagonist) or the tumor necrosis factor (TNF) antagonist (TNF(BP)) prior to EtOH administration. RESULTS: Acute EtOH intoxication did not alter the mRNA content of IGFBP-3, -4 or -5 in liver or kidney. However, EtOH increased IGFBP-1 in blood (5-fold), which was associated with an up-regulation of IGFBP-1 mRNA content in liver and kidney (2- to 3-fold). Likewise, the injection of the nonmetabolizable alcohol -butanol also increased IGFBP-1 in plasma, liver, and kidney. The increased IGFBP-1 in blood and tissues was not prevented by inhibiting alcohol metabolism with 4-MP. However, pretreatment with cyanamide markedly accentuated the EtOH-induced increase in IGFBP-1 in blood (20-fold), liver (3.5-fold), and kidney (12-fold), indicating that accumulation of acetaldehyde can enhance IGFBP-1 synthesis. A time course study indicated that EtOH increased plasma IGFBP-1 levels as early as 0.5-1 hr, and that this response was associated with elevated IGFBP-1 mRNA in liver but not kidney. Pretreatment with RU486 did not prevent or attenuate the EtOH-induced increase in IGFBP-1. However, the alcohol-induced increase in IGFBP-1 was attenuated by TNF(BP). CONCLUSIONS: These data suggest that the acute alcohol-induced increase in IGFBP-1 is mediated, at least in part, by TNF and is independent of EtOH metabolism and increases in endogenous glucocorticoids.  相似文献   
55.
    
Colorectal cancer accounts for a significant proportion of cancer deaths worldwide. The need to develop more chemotherapeutic agents to combat this disease is critical. Cyclin dependent kinases(CDKs), along with its binding partner cyclins, serve to control the growth of cells through the cell cycle. A new class of drugs, termed CDK inhibitors, has been studied in preclinical and now clinical trials. These inhibitors are believed to act as an anti-cancer drug by blocking CDKs to block the uncontrolled cellular proliferation that is hallmark of cancers like colorectal cancer. CDK article provides overview of the emerging drug class of CDK inhibitors and provides a list of ones that are currently in clinical trials.  相似文献   
56.
57.
Cannabinoids have been used medicinally for centuries, and in the last decade, attention has focused on their broad therapeutic potential particularly in seizure management. While some cannabinoids have demonstrated anticonvulsant activity in experimental studies, their efficacy for managing clinical seizures has not been fully established. This commentary will touch on our understanding of the brain endocannabinoid system’s regulation of synaptic transmission in both physiological and pathophysiological conditions, and review the findings from both experimental and clinical studies on the effectiveness of cannabinoids to suppress epileptic seizures. At present, there is preliminary evidence that non-psychoactive cannabinoids may be useful as anticonvulsants, but additional clinical trials are needed to fully evaluate the efficacy and safety of these compounds for the treatment of epilepsy.  相似文献   
58.
Medicare beneficiaries with incomes at or near the poverty level are also eligible for benefits provided by state Medicaid programs. The Medicare Modernization Act of 2003 details special provisions for these "dually eligible" individuals compared with other Medicare beneficiaries. Issues related to enrollment, benefits, and patient compliance are discussed, as well as challenges physicians face in caring for this vulnerable population.  相似文献   
59.
60.
Recent engine design and emission trends have led to the commercial use of Atmospheric Plasma Spray (APS) coatings for cylinder liner applications like the TiO2 APS coating. It was shown in our previous work that this type of coating showed better friction results compared to steel lubricated with MoDTC. To further investigate this feature, a parametric study was carried out involving the effect of MoDTC concentration, test temperature, Hertzian contact pressure and the change of counterpart materials from steel balls to ceramic balls (Al2O3 and ZrO2). Ball-on-flat tribotests were carried out on a reciprocating (ball-on-flat) tribometer lubricated with base oil containing MoDTC. Results show that for all the test conditions used including the concentration of MoDTC, test temperature and the contact pressure, lower friction and wear is observed for the TiO2 APS coating compared to reference steel. To explain the low friction behavior, tribofilm compositions were investigated and it was observed that MoS2 is always formed in the case of TiO2 APS with no oxysulphide species. For the reference steel, MoOxSy species are mainly detected in the tribofilms. XPS analyses performed on TiO2 APS flats when the counterpart material was changed from steel balls to ceramic balls suggested the formation of MoS2 (Mo in +iv oxidation state) and Mo–C (Mo in +iv or +ii oxidation state) species with a negligible amount of MoO3 (Mo in +vi oxidation state). It was also shown that a significant amount of molybdenum atoms inside the tribofilm, originating from MoDTC (Mo in +v oxidation state) were reduced in the tribological contact. A mechanism for the decomposition of MoDTC on the basis of tribocatalytic behaviour hypothesized in our previous work was proposed and discussed.

Tribocatalytic behaviour of TiO2 APS coatings in presence of MoDTC additive under boundary lubrication conditions – decomposition mechanism  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