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   900597篇
  免费   62494篇
  国内免费   2340篇
耳鼻咽喉   12480篇
儿科学   28757篇
妇产科学   26154篇
基础医学   126708篇
口腔科学   24735篇
临床医学   74824篇
内科学   183359篇
皮肤病学   19001篇
神经病学   71535篇
特种医学   36472篇
外国民族医学   336篇
外科学   142229篇
综合类   19033篇
一般理论   247篇
预防医学   64633篇
眼科学   20091篇
药学   63860篇
中国医学   1798篇
肿瘤学   49179篇
  2018年   9067篇
  2017年   7175篇
  2016年   7697篇
  2015年   8754篇
  2014年   12397篇
  2013年   19258篇
  2012年   25709篇
  2011年   27325篇
  2010年   16627篇
  2009年   15812篇
  2008年   26184篇
  2007年   27784篇
  2006年   27971篇
  2005年   27500篇
  2004年   26344篇
  2003年   25505篇
  2002年   25085篇
  2001年   41376篇
  2000年   42576篇
  1999年   36292篇
  1998年   9978篇
  1997年   9157篇
  1996年   9089篇
  1995年   8452篇
  1994年   8086篇
  1993年   7588篇
  1992年   28209篇
  1991年   26994篇
  1990年   26419篇
  1989年   25351篇
  1988年   23564篇
  1987年   23182篇
  1986年   22265篇
  1985年   21170篇
  1984年   15814篇
  1983年   13484篇
  1982年   8095篇
  1979年   14594篇
  1978年   10210篇
  1977年   8634篇
  1976年   8149篇
  1975年   8962篇
  1974年   10698篇
  1973年   10188篇
  1972年   9662篇
  1971年   8919篇
  1970年   8585篇
  1969年   8026篇
  1968年   7684篇
  1967年   7087篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Regulation of cell-mediated immunity in cutaneous leishmaniasis   总被引:1,自引:0,他引:1  
F Y Liew 《Immunology letters》1987,16(3-4):321-327
There is now good evidence that cell-mediated immunity (CMI) rather than humoral antibody plays a causal role in acquired immunity to leishmaniasis. In genetically susceptible strains of mice, the failure to control the disease progression is associated with a population of Lyt-2-T cells which can prevent the induction or expression of curative CMI and hence exacerbate disease development. Susceptible BALB/c mice can be rendered resistant to L. major infection by prior sublethal dose gamma-irradiation, anti-mu antibody treatment from birth, anti-L3T4 antibody treatment or intravenous (i.v.) or intraperitoneal (i.p.) route of immunisation with killed L. major promastigotes or isolated leishmanial antigens. The route of immunisation, however, appears crucial in the induction of prophylactic immunity. Subcutaneous (s.c.) and intramuscular routes of immunisation with killed promastigotes are not only ineffective, they induce a population of Lyt-2- L3T4+ T cells which inhibit the prophylactic effect of i.v. immunisation. Although both the disease-promoting T cells and the host-protective T cells express the same phenotypic cell surface markers, they differ functionally. Protective T cells produce interferon-gamma (IFN-gamma) and macrophage-activating factor (MAF) when cultured in vitro with leishmanial antigens, whereas the disease-promoting T cells do not. In addition, these latter cells are able to produce substances in their antigen-specific culture supernatant which inhibits the MAF activity of the host protective T cells.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
992.
993.
This article is concerned with a prospective study about the systematical, simultaneous and comparative assay of four biological markers (carcino-embryonic antigen, lactate dehydrogenase, gammaglutamyl transferase and phosphohexose isomerase). This study was conducted in a department of Hematology and oncology on 258 patients. The dosage of each marker separately does not appear to be of diagnostical interest because of a lack of sensibility and specificity. But when there is a positive statistical correlation between several makers, their simultaneous dosage may allow the diagnostic of cancer and sometimes the determination of its origin.  相似文献   
994.
995.
996.
148 patients with various forms of cerebrovascular disease (CVD) were studied by means of a multiparametric analysis ofin vitro platelet aggregation, based on the following six parameters: ADP and epinephrine primary and secondary aggregation thresholds and percent maximum aggregation induced by optimal concentrations of ADP and epinephrine. These patients were assigned to four study groups, according to clinical diagnosis supported by CT scan, of transient ischemic attack and reversible neurological deficit (TIA-RIND), or completed stroke, in the presence or absence respectively of antiplatelet medical treatment at the time of the study. A statistically significant increase of thein vitro platelet aggregation was found in 44.4% of the untreated TIA-RIND patients and in 33.9% of the untreated stroke patients. However this last group showed a higher percentage of very marked hyperaggregation. Differences between the two treated study groups and controls were not signicant. No difference was found in collagen-and ristocetin-induced aggregation between the patient groups and the controls.
Sommario 148 pazienti con varie forme di malattia cerebrovascolare, sono stati studiati con analisi multiparametriche dell'aggregazione piastrinica in vitro sulla base dei seguenti sei parametri: le soglie di aggregazione primaria e secondaria e l'aggregazione massima percentuale indotta da ADP ed Epinefrina. Questi pazienti sono stati suddivisi in 4 gruppi di studio in accordo con la diagnosi clinica confortata dai dati della TAC e cioè: TIA, RIND, o rammollimento in presenza o in assenza rispettivamente di un trattamento antiaggregante nel momento dello studio. è stato trovato un aumento statisticamente significativo dell'aggregazione in vitro delle piastrine nel 44.4% dei casi TIA, RIND non trattati e nel 33,9% dei casi di rammollimento non trattati. Quest'ultimo gruppo, però, ha dimostrato una più alta percentuale di iperaggregazione molto marcata. Le differenze tra i 2 gruppi di studio trattati con antiaggreganti e i controlli non erano significative. Inoltre nessuna differenza è stata riscontrata tra i gruppi e i controlli nell'aggregazione indotta da collageno e ristocetina.
  相似文献   
997.
The in vitro exposure of rat bronchial smooth muscle to the acetylcholinesterase inhibitor soman (0-[1,1,2-trimethylpropyl]-methylphosphonofluoridate) reduced the potassium (51 mM) evoked release of 3H-acetylcholine (3H-ACh). Exposure to 1.0 and 100 microM soman for 15 min inhibited the acetylcholinesterase (AChE) activity completely and reduced the potassium evoked release by 23.1% and 34.4% respectively. In the presence of scopolamine (0.3 microM), however, there was a large enhancement (87.0%) of potassium evoked release during soman inhibited (100%) AChE-activity. Furthermore, soman (1.0 microM) did not reduce the spontaneous release of 3H-ACh. The results indicate that the presynaptic effect of soman is due to the enhanced concentration of ACh following AChE-activity inhibition in the synaptic region. This induces a stimulation of presynaptic muscarinic receptors and thereby modulation of the ACh release only during evoked release.  相似文献   
998.
Urinary excretion of N-acetyl-beta-glucosaminidase (NAG) is an early marker of nephrotoxicity. NAG activity was assayed by the fluorimetric method of Leaback and Walker in 17 patients treated (22 courses) with carboplatin (CBDCA, 220-550 mg/m2) before infusion and 24, 48, 72 and 96 h after. Increased excretion of NAG, a sensitive index of renal tubular damage, was observed following 10 of the 22 courses. A transient increase in plasma creatinine and/or abnormal proteinuria was observed in 6 cases. Impaired renal function prior to therapy seems to be a predisposing factor to the nephrotoxicity.  相似文献   
999.
Since the beginning of this century, trans- naso-sphenoidal resection of the pituitary fossa tumors has been widely used clinically. It has more merits than other operative approaches used before. In China it has been adopted by both ENT doctors and neurosurgeons since 1959.1 In order to afford some relevant anatomical data, we measured 137 adult sagittal plane skulls with distinct landmarks.  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