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   1117篇
  免费   63篇
  国内免费   5篇
儿科学   6篇
妇产科学   3篇
基础医学   123篇
口腔科学   5篇
临床医学   61篇
内科学   445篇
皮肤病学   6篇
神经病学   42篇
特种医学   21篇
外科学   192篇
综合类   4篇
预防医学   32篇
眼科学   16篇
药学   14篇
肿瘤学   215篇
  2022年   10篇
  2021年   18篇
  2020年   15篇
  2019年   14篇
  2018年   12篇
  2017年   19篇
  2016年   26篇
  2015年   26篇
  2014年   39篇
  2013年   43篇
  2012年   83篇
  2011年   52篇
  2010年   57篇
  2009年   51篇
  2008年   66篇
  2007年   63篇
  2006年   52篇
  2005年   68篇
  2004年   76篇
  2003年   54篇
  2002年   62篇
  2001年   22篇
  2000年   34篇
  1999年   29篇
  1998年   17篇
  1997年   23篇
  1996年   21篇
  1995年   15篇
  1994年   14篇
  1993年   7篇
  1992年   14篇
  1991年   11篇
  1990年   6篇
  1989年   7篇
  1988年   6篇
  1987年   11篇
  1986年   6篇
  1985年   7篇
  1984年   5篇
  1983年   2篇
  1982年   2篇
  1981年   3篇
  1980年   1篇
  1977年   5篇
  1975年   2篇
  1974年   3篇
  1973年   1篇
  1971年   2篇
  1966年   1篇
  1962年   1篇
排序方式: 共有1185条查询结果,搜索用时 15 毫秒
1.
When stimulating the mixed nerve to record evoked potential, both sensory and motor fibers are activated before entering the spinal cord. The N10 potential has been described as an antidromic motor evoked potential based on results obtained by recording at the anterior midneck. In the present study, we examined the changes in latencies of Erb's potential, N10, and N13 by stimulating the median nerve distally at the wrist and proximally at the elbow. The conduction velocity of N10 calculated by the difference between N10 latencies at the two stimulation points was consistent with motor conduction velocity, although N13 conduction velocity estimated by the same method reflected a sensory conduction velocity. A positive relation was also observed between the indirect latency from the stimulation point to the anterior root as calculated using the equation (F - M - 1) / 2 (ms) and the direct latency to the negative peak of the N10 potential. Our data support the notion that N10 represents antidromic motor potential originating in the spinal entry zone of the anterior root.  相似文献   
2.
3.
4.
5.
Summary: Bis(phenoxy‐imine) Zr complexes with MAO activation can produce polyethylenes with well‐defined bimodal molecular weight distributions. Polymerization behavior indicates that minor changes in the ligand structures can have a significant effect on the modality of the resulting polyethylenes. Although there is no direct relationship between the bimodal catalytic behavior and the structure of a precatalyst complex in solution, a precatalyst complex having a methyl or methoxy group para to the phenoxy‐oxygen inclined to exhibit bimodal behavior whereas that with a pentafluorophenyl group on the imine‐nitrogen displayed unimodal behavior. Polymerization results suggest that bimodal behavior is linked to the presence of two kinds of cationic active species, which arise from different modes of ligand coordination. A qualitative correlation was found between the calculated amounts of possible cationic active species and the uni‐ and bimodal catalytic behavior. Based on the results obtained, we concluded that the bimodal polyethylenes are produced by two kinds of cationic active species having two available cis‐located sites with cis‐N, trans‐O and cis‐N, cis‐O arrangements. The results introduced herein are rare examples of the production of well‐defined bimodal polyethylenes using a single precatalyst.

Bis(phenoxy imine) Zr complexes can produce well‐defined bimodal polyethylenes.  相似文献   

6.
It is generally accepted that the interaction between CD40 and its ligand (CD154) plays a decisive role in contact-dependent help for T and B cells. In CD154-deficient MRL/Mp-Fas(lpr) (MRL/lpr) mice, however, high titres of IgG2a-type autoantibodies against small nuclear ribonucleoproteins (snRNPs) are observed. We successfully isolated two CD154-deficient MRL/lpr Th1 lines, which could provide B cell help for anti-snRNP antibody production. The proliferative responses of the Th1 cell lines were MHC class II (I-Ek)-restricted. Although syngeneic B cell proliferation was induced by Th1 lines in both a contact-dependent and -independent manner, the soluble form of TNF-alpha (sTNF-alpha) was not involved in contact-independent B cell proliferation. On the other hand, both anti-TNF-alpha and TNF-receptor 2 (TNF-R2, p75) monoclonal antibody (MoAb) blocked contact-dependent B cell proliferation, suggesting that the transmembrane form of TNF-alpha (mTNF-alpha)-TNF-R2 co-stimulation participates in B cell activation. Similarly, anti-TNF-alpha and TNF-R2 MoAb inhibited anti-snRNP antibody production in vitro, but anti-CD154 or TNF-R1 MoAb did not. These results indicate that the interaction of mTNF-alpha on activated Th1 cells with TNF-R2 on B cells may be involved in the autoimmunity seen in MRL mice, and that the blockade of CD40-CD154 co-stimulation may not always be able to suppress some Th1-related manifestations of lupus.  相似文献   
7.
Severe inflammatory responses after major surgeries, trauma, and infection develop multiple organ dysfunction. In the mechanisms of the pathogenesis of these responses, activated neutrophils are thought to be important in terms of their ability to produce various kinds of proteinases, which can degrade various proteins constructing human tissues. Among their proteinases, neutrophil elastase is the strongest serine proteinase secreted from activated neutrophils. Thus, we examined in this study the inhibitory effect and therapeutic efficacy of newly produced recombinant human Kunitz-type proteinase inhibitor (R-020), which coded the second domain of human urinary trypsin inhibitor. R-020 was effective in significantly improving the survival rate after induction of the rat lethal peritonitis model (cecal ligation and punctureinduced septic shock model). We suggest that various serine proteinases are implicated in the pathogenesis of neutrophil-related multiple organ failure and that recombinant human Kunitz-type proteinase inhibitor might be effective in the treatment of these kinds of organ dysfunction.  相似文献   
8.
The livers of DNase II-deficient mouse embryos contain many macrophages carrying undigested DNA, and the embryos die in utero. Here we report that erythroid precursor cells underwent apoptosis in the livers of DNase II-deficient embryos and that in the liver, interferon-beta mRNA was expressed by the resident macrophages. When the DNase II-deficient mice were crossed with mice deficient in type I interferon receptor, the resultant 'double-mutant' mice were born healthy. The double-mutant embryos expressed interferon-beta mRNA, but the expression of a subset of the interferon-responsive genes dysregulated in DNase II-deficient embryos was restored to normal. These results indicate that the inability to degrade DNA derived from erythroid precursors results in interferon-beta production that induces expression of a specific set of interferon-responsive genes associated with embryonic lethality in DNase II-deficient mice.  相似文献   
9.
Fas was recently demonstrated to be the major target molecule engaged by CD4+ cytolytic T lymphocytes (CTL). We examined Fas expression on various cloned T cell subpopulations and their susceptibility to lysis by CD4+ or CD8+ CTL. A reciprocal relationship in Fas and Fas-ligand expression was observed in CD4+ T helper (Th)1- and Th2-type clones, and Fas mRNA was predominantly detected in Th2 clones, whereas Fas-ligand mRNA was principally found in Th1 clones. The two Th0 clones tested expressed both Fas and Fas-ligand, but only one exhibited cytolytic activity, whereas both were sensitive to CD4-mediated lysis. A functional consequence of the inverse Fas-Fas-ligand expression pattern was that Th2 and Th0 cells were sensitive to lysis by both Th1 CD4+ CTL and a CD8+ CTL clone in a Fas-dependent manner. These results suggest that cytolytic CD4+ Th1 cells may play an immunomodulatory role, regulating a Th2/Th0 response by Fas-mediated lysis.  相似文献   
10.
Fermented foods such as Japanese traditional food “miso (fermented soy bean paste)” have been shown to be rich source of micronutrients with the potential to prevent various human diseases. We have introduced effects of a new dietary supplement of fermented grain foods mixture containing extracts from wheat germ, soybeans, rice bran, tear grass, sesame, wheat, citrus lemon, green tea, green leaf extract and malted rice under the trade name of antioxidant biofactor (AOB). Chemical analysis of AOB shows the presence of various phenolic compounds (catechins, rutin, genistin, daidzin, etc.). AOB has strong antioxidant properties and additional biological effects, which might be of importance in context with the prevention of degenerative diseases. This paper focuses on the effect of supplementing AOB in various animal models and humans.  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