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   1102篇
  免费   62篇
  2023年   4篇
  2022年   15篇
  2021年   15篇
  2020年   11篇
  2019年   13篇
  2018年   19篇
  2017年   12篇
  2016年   36篇
  2015年   48篇
  2014年   51篇
  2013年   76篇
  2012年   82篇
  2011年   77篇
  2010年   49篇
  2009年   42篇
  2008年   75篇
  2007年   70篇
  2006年   56篇
  2005年   51篇
  2004年   45篇
  2003年   50篇
  2002年   48篇
  2001年   17篇
  2000年   11篇
  1999年   11篇
  1998年   15篇
  1997年   7篇
  1996年   23篇
  1995年   10篇
  1994年   7篇
  1993年   6篇
  1992年   7篇
  1991年   4篇
  1990年   6篇
  1989年   7篇
  1988年   7篇
  1987年   5篇
  1986年   6篇
  1985年   4篇
  1984年   11篇
  1983年   4篇
  1982年   7篇
  1981年   4篇
  1980年   4篇
  1978年   4篇
  1973年   3篇
  1972年   4篇
  1969年   3篇
  1966年   3篇
  1964年   5篇
排序方式: 共有1164条查询结果,搜索用时 247 毫秒
11.
Recurrent ocular herpes is an insoluble problem for the clinician. As cellular immunity plays an important role in controlling herpes relapses, and other studies have shown the efficacy of HSV-specific transfer factor (TF) for the treatment of herpes patients, an open clinical trial was undertaken in 134 patients (71 keratitis, 29 kerato-uveitis, 34 uveitis) suffering from recurrent ocular herpetic infections. The mean duration of the treatment was 358 days, and the entire follow-up period 189121 before, and 64062 days after TF treatment. The cell-mediated immune response to the viral antigens, evaluated by the lymphocyte stimulation test (LST) and the leucocyte migration test (LMT) (P<0.001), was significantly increased by the TF treatment. The total number of relapses was decreased significantly during/after TF treatment, dropping from 832 before, to 89 after treatment, whereas the cumulative relapse index (RI) dropped, during the same period, from 13.2 to 4.17 (P<0.0001). No side effects were observed. It is concluded that patients with relapsing ocular herpes can benefit from treatment with HSV-specific TF.  相似文献   
12.
Foreword     
  相似文献   
13.
Concentrations of 8 trace elements (Fe, Cu, Zn, Se, Br, Pb, Rb, and Sr) at different lactation time were measured by the PIXE multi-elemental technique. Time dependence and interelement correlations were studied. A total of 200 milk samples from 32 lactating mothers were supplied from 2 to 120 d after delivery of 26 full-term and 6 preterm infants. All elements showed a lognormal frequency-distribution. The Fe, Cu, Zn, and Se contents in preterm milk were found to be somewhat different with respect to full-term milk. Cu, Zn, Se, Br, Pb, and Rb concentrations declined with lactation time, both in pre- and full-term samples. Sr and Fe contents did not show any change with time. Detailed analysis of data by partial correlation and multiple regression methods was performed. No substantial differences between preterm and full-term samples were found in the results of partial correlation analysis. Cu and Zn were found to be correlated with lactation time, whereas the measured time dependence for the other elements has to be attributed to the effect of the existing interelement correlation. All the measured elements appeared to be correlated with at least one other element. In particular, Se was inversely correlated with Zn and directly with Cu. The zinc and copper contents in milk can therefore depend on the variation in the mother selenium intake.  相似文献   
14.
The murine white (W) spotting locus is the site of the c-kit gene and encodes a tyrosine kinase receptor while the complementary Steel (Sl) iocus encodes its ligand. Mutations at either locus have profound effects on hematopoiesis, particularly erythroid and mast cell proliferation. We added c-kit antisense oligonucleotides to long-term suspension cultures of enriched human umbilical cord progenitor cells. This resulted in the suppression of c-kit gene expression and the preferential suppression of the generation of erythroid burst-forming cells (BFU-E) which extended over the life of the culture (3 weeks). The results provide an in vitro model of the “W phenotype” in human hematopoiesis and confirm the importance of c-kit gene function in early erythropoiesis. Because the generation of BFU-E was suppressed even after c-kit gene expression had recovered, this gene product may be critical to the erythroid commitment process. © 1993 Wiley-Liss, Inc.  相似文献   
15.
Abstract: Mice infected with the LP-BM5 murine leukemia virus mixture develop severe immunosuppression and an encephalopathy characterized by spatial learning deficits. Twelve weeks after infection of C57BL/6J mice with LP-BM5, significant (50–60%) reductions in Met-enkephalin and substance P levels were observed in the striatum, whereas somatostatin levels were unchanged. In addition, a 39% decrease in hypothalamic substance P concentrations was observed, with no alteration in Met-enkephalin levels. The apparent selectivity of the decrease in neuropeptide concentrations indicates that a functional alteration of the primary striatal efferent neurons occurs in this infection, which may contribute to the impairment of spatial learning observed in these mice. Moreover, this decrease in striatal neuropeptide levels is similar to the neuropathological changes in basal ganglia observed in HIV-infected individuals and is consistent with previous studies suggesting that the LP-BM5-infected mouse may serve as a useful model of AIDS dementia.  相似文献   
16.
Extracts from autoclaved maize culture ofFusarium tumidum strain R-5823 were toxic towardsArtemia salina. Bioassay-guided fractionation of the organic extract led to the isolation of the toxic compound that was identified as the trichothecene toxin neosolaniol (NEOS) by1H,13C nuclear magnetic resonance spectroscopy and low-resolution electronic impact mass spectrometry. The amount of NEOS produced by the strain R-5823 was 300 mg/kg maize culture. NEOS was also detected by HPLC in cultures of four out of seven additional strains ofF. tumidum andGibberella tumida with different origin, in amounts ranging from 1 to 311 mg/kg. This is the first report on the production of a trichothecene toxin byF. tumidum.  相似文献   
17.
Two chlorophenyl-containing antibiotics have been isolated from a strain ofActinoplanes (ATCC 33002). Antibiotic A 15104 Y is a chlorinated phenylpyrrole compound whose structure has been confirmed by chemical synthesis. Antibiotic A 15104 Z is a chlorophenol derivative for which a structural formula is proposed on the basis of its physicochemical properties. A 15104 Y shows antimicrobial activity against Gram-positive, Gram-negative, and acid-fast bacteria, yeasts, fungi, and protozoa, while A 15104 Z possesses a low activity against Gram-positive bacteria andTrichophyton. A 15104 Y has a weak activity in curing experimentally infected mice, at a dose that is one-fifth the LD50 for the same species. This is the first example of a chloropyrrole derivative isolated from an actinomycete.  相似文献   
18.
Single doses of naloxone (0.025 to 0.5 mg/kg) or of one of four quaternary narcotic antagonists (i.e. nalorphine allobromide, nalorphine methobromide, naloxone methobromide or naltrexone methobromide, 1 to 60 mg/kg) were given s.c. to rats before morphine, 5 mg/kg i.v. In the absence of antagonists morphine reduced G.I. transit of a charcoal meal to about 15% of drug-free controls and consistently delayed nociceptive reactions (55°C hot plate) in all animals. Doses of antagonists slightly reducing morphine antinociception (centrally effective = A) and restoring G.I. transit to about 50% of drug-free rats (peripherally effective = B) were estimated. The A:B ratio, indicating peripheral selectivity, was at least 8 for any of the quaternary antagonists given 10 min before morphine, but prolonging this interval may have resulted in a lower figure (i.e. less peripheral selectivity) because of reduced A and increased B. This was definitely so for naltrexone methobromide (A:B, > 60 at 10 min, about 1 at 80 min) and was not apparent for nalorphine methobromide according to available data, which for nalorphine allobromide and to a lesser extent for naloxone methobromide showed only an increase in B at intervals longer than 10 min. Both morphine-induced antinociception and inhibition of G.I. transit were reduced by naloxone at the lower doses tested and were fully prevented at the higher. These findings indicate that, unlike naloxone, the investigated quaternary narcotic antagonists are interesting prototype drugs for selective blockade of opiate receptors outside the CNS, although certain critical aspects, possibly biological N-dealkylation to the corresponding tertiary antagonists, condition peripheral selectivity.  相似文献   
19.
Bilitranslocase, a plasma membrane protein involved in bilirubin and other organic anion uptake by the liver, exhibits a high molecular weight (170 000) when isolated in the presence of deoxycholate. This value is decreased to approx. 100 000 if deoxycholate is not included in the isolation medium. Both preparations can be resolved into two kinds of subunit, α and β, of 37 000 and 35 500, respectively, by reduction with 2-mercaptoethanol and addition of sodium dodecyl sulfate. Under these conditions the two subunits are still capable of high-affinity sulfobromophthalein binding and, despite the presence of the detergent, may be isolated by preparative polyacrylamide gel electrophoresis still associated with the dye. It may be suggested that the physiological subunit composition of bilitranslocase is α2-β.  相似文献   
20.
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