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   3591篇
  免费   466篇
  国内免费   10篇
耳鼻咽喉   32篇
儿科学   158篇
妇产科学   325篇
基础医学   278篇
口腔科学   82篇
临床医学   1159篇
内科学   427篇
皮肤病学   119篇
神经病学   174篇
特种医学   302篇
外科学   292篇
综合类   86篇
一般理论   5篇
预防医学   269篇
眼科学   59篇
药学   182篇
肿瘤学   118篇
  2023年   50篇
  2021年   35篇
  2020年   47篇
  2019年   53篇
  2018年   84篇
  2017年   114篇
  2016年   108篇
  2015年   128篇
  2014年   145篇
  2013年   146篇
  2012年   93篇
  2011年   141篇
  2010年   147篇
  2009年   145篇
  2008年   120篇
  2007年   126篇
  2006年   108篇
  2005年   113篇
  2004年   102篇
  2003年   97篇
  2002年   69篇
  2001年   90篇
  2000年   74篇
  1999年   81篇
  1998年   110篇
  1997年   123篇
  1996年   123篇
  1995年   108篇
  1994年   71篇
  1993年   62篇
  1992年   48篇
  1991年   51篇
  1990年   47篇
  1989年   69篇
  1988年   71篇
  1987年   54篇
  1986年   62篇
  1985年   63篇
  1984年   46篇
  1983年   38篇
  1982年   36篇
  1981年   32篇
  1979年   30篇
  1978年   30篇
  1977年   29篇
  1976年   24篇
  1975年   33篇
  1971年   25篇
  1970年   20篇
  1968年   20篇
排序方式: 共有4067条查询结果,搜索用时 0 毫秒
101.

Background

Gloriosa superba produces an array of alkaloids including colchicine, a compound of interest in the treatment of various diseases. The tuber of Gloriosa superba is a rich source of colchicine which has shown anti-gout, anti-inflammatory, and anti-tumor activity. However, this promising compound remains expensive and Gloriosa superba is such a good source in global scale. Increase in yield of naturally occurring colchicine is an important area of investigation.

Materials and Methods

The effects of inoculation by four arbuscular mycorrhizal (AM), fungi, Glomus mossae, Glomus fasciculatum, Gigaspora margarita and Gigaspora gilmorei either alone or supplemented with P-fertilizer, on colchicine concentration in Gloriosa superba were studied. The concentration of colchicine was determined by high-performance thin layer chromatography.

Results

The four fungi significantly increased concentration of colchicine in the herb. Although there was significant increase in concentration of colchicine in non-mycorrhizal P-fertilized plants as compared to control, the extent of the increase was less compared to mycorrhizal plants grown with or without P-fertilization. This suggests that the increase in colchicine concentration may not be entirely attributed to enhanced P-nutrition and improved growth. Among the four AM fungi Glomus mossae was found to be best. The total colchicine content of plant (mg / plant) was significantly high in plants inoculated with Glomus mossae and 25 mg kg−1phosphorus fertilizer (348.9 mg /plant) while the control contain least colchicine (177.87 mg / plant).

Conclusion

The study suggests a potential role of AM fungi in improving the concentration of colchicine in Gloriosa superba tuber.  相似文献   
102.
Research to develop and validate novel methods for diagnosis of aspergillosis based on detection of galactomannan requires the use of clinical specimens that have been stored frozen. Data indicating that galactomannan remains stable when frozen are scant. The objective of this study was to determine the stability of galactomannan in clinical specimens stored at −20°C that were positive in the Platelia Aspergillus enzyme immunoassay when initially tested. Prospective real-time testing of serum and bronchoalveolar lavage (BAL) fluid pools from positive and negative patient specimens showed no decline in galactomannan index (GMI) over 11 months at −20°C and no development of positive reactions in the negative-control pool. Retrospective testing of positive specimens that had been stored at −20°C for 5 years showed that 28 of 30 serum (n = 15) or BAL (n = 15) specimens remained positive. These findings support the use of frozen serum or BAL specimens stored for at least 5 years in evaluation of diagnostic tests based on detection of galactomannan.  相似文献   
103.

Objective

infants of women with diabetes in pregnancy are at increased risk of hypoglycaemia. If the infant's blood glucose is low and the mother is unable to breast feed/provide sufficient expressed breast milk, infants are often given formula. Some hospitals encourage women with diabetes to express breast milk before birth. However, there is limited evidence for this practice, including its impact on labour and birth, e.g. causing premature birth may be a concern. A pilot study was undertaken to establish the feasibility of conducting an adequately powered randomised controlled trial to evaluate this practice.

Design

consecutive eligible women with pre-existing or gestational diabetes (requiring insulin), planning to breast feed and attending the study hospital were offered participation. Inclusion criteria: 34-36 weeks of gestation; singleton pregnancy; cephalic presentation; and able to speak, read and write in English. Exclusion criteria: history of spontaneous preterm birth, antepartum haemorrhage, placenta praevia and suspected fetal compromise. Women were encouraged to express colostrum twice a day from 36 weeks of gestation, and advised how to store the colostrum, which was frozen for their infant's use after birth. They were asked to keep a diary documenting their expressing. Data: demographic questionnaire, telephone interview at six and 12 weeks postpartum and medical record data.

Setting

a public, tertiary, women's hospital in Melbourne, Australia.

Participants

43 women with diabetes in pregnancy (requiring insulin).

Findings

cardiotocographs were undertaken after the first expressing episode and none of the infants showed any sign of fetal compromise. Forty per cent of infants received formula in the 24 hours postpartum. The proportion of infants receiving any breast milk at six weeks was 90%, and this decreased to 75% at 12 weeks. No women showed evidence of hypoglycaemia post expressing. The intervention was positively received by most women; 95% said that they would express antenatally again if the practice proved to be beneficial. The amount of colostrum varied according to the number of expressions, the length of time in the study and the time spent expressing, with a median of 14 days expressing and 39.6 ml of colostrum obtained.

Key conclusions

the small number of women in this pilot was not an adequate number to examine safety or efficacy, but this study does provide evidence that it would be feasible and desirable to conduct a randomised controlled trial of antenatal milk expressing for women with diabetes requiring insulin in pregnancy.

Implications for practice

it is important that this widespread practice undergoes rigorous evaluation to assess both efficacy and safety. Until such evidence is available, the authors suggest that the routine encouragement of antenatal milk expressing in women with diabetes in pregnancy should cease.  相似文献   
104.
105.
106.
The sting of Giant Asian honeybee (Apis dorsata) or Bambara in Sinhala and Karunge Kulavi in Tamil is a common environmental hazard in Sri Lanka known to cause immediate allergic reactions, which could be fatal in sensitized individuals. We reported myocardial infarction, bowel gangrene and fatal anaphylaxis in a prospectively proven case series and the association of these uncommon complications with delayed removal of stingers from the patients' skin.  相似文献   
107.
Basal tubulobulbar complexes (TBCs) that occur at attachment sites between neighboring Sertoli cells are subcellular machines that internalize intercellular junctions during movement of spermatocytes from basal to adluminal compartments of the seminiferous epithelium. Each complex consists of an elongate tubular extension of two attached plasma membranes, and is capped at its distal end by a clathrin‐coated pit. The tubular region is surrounded by a cuff of actin arranged in a dendritic network. Near the end of the complex, a bulbous region forms that lacks the actin cuff but is closely associated with cisternae of endoplasmic reticulum. The bulb eventually buds from the complex and enters endocytic compartments of the Sertoli cell. Previous research has shown that when the actin network is perturbed using the actin filament–disruptor, cytochalasin D, apical tubulobulbar complexes that are associated with spermatids were associated with lower levels of actin, patchy actin networks and swollen tubular regions. Here we explored the effects of actin network perturbation on the morphology of basal tubulobulbar complexes in stage V seminiferous tubules. Isolated rat testes were perfused ex vivo for one hour with oxygenated Krebs‐Henseleit buffer (with BSA) containing either 40 μM cytochalasin D or control solution containing DMSO and perfusion‐fixed for electron microscopy. Compared to control, actin cuffs in drug‐treated TBCs appeared less uniform and patchy. In addition, the tubular regions of the complexes appeared swollen. Our results are consistent with the conclusion that intact networks of actin filaments are required for maintaining the structural integrity of basal TBCs. Anat Rec, 299:1449–1455, 2016. © 2016 Wiley Periodicals, Inc.  相似文献   
108.
Analysis of penicillin-nonsusceptible Streptococcus pneumoniae (PNSP) isolates in Hong Kong by use of a combination of antibiogram typing, serotyping, multilocus sequence typing, and pulsed-field gel electrophoresis indicated that the dissemination of PNSP was the result of the spread of international clones: variants of the Spain(23F)-1 or Spain(6B)-2 clones were the predominant PNSP isolates from 1994 to 1997 and remained so, but Taiwan(19F)-14 and Taiwan serotype 6B clones were disseminated in Hong Kong in 1999 and 2000. Concomitant changes in antibiotic susceptibility profiles, with the rate of susceptibility to chloramphenicol rising from 10% in the period from 1994 to 1997 to 31% (P < 0.001) in 1999 and 2000, were noted to accompany the shift of clones.  相似文献   
109.
A 42-kDa fragment from the C terminus of major merozoite surface protein 1 (MSP1) is among the leading malaria vaccine candidates that target infection by asexual erythrocytic-stage malaria parasites. The MSP1(42) gene fragment from the Vietnam-Oak Knoll (FVO) strain of Plasmodium falciparum was expressed as a soluble protein in Escherichia coli and purified according to good manufacturing practices. This clinical-grade recombinant protein retained some important elements of correct structure, as it was reactive with several functional, conformation-dependent monoclonal antibodies raised against P. falciparum malaria parasites, it induced antibodies (Abs) that were reactive to parasites in immunofluorescent Ab tests, and it induced strong growth and invasion inhibitory antisera in New Zealand White rabbits. The antigen quality was further evaluated by vaccinating Aotus nancymai monkeys and challenging them with homologous P. falciparum FVO erythrocytic-stage malaria parasites. The trial included two control groups, one vaccinated with the sexual-stage-specific antigen of Plasmodium vivax, Pvs25, as a negative control, and the other vaccinated with baculovirus-expressed MSP1(42) (FVO) as a positive control. Enzyme-linked immunosorbent assay (ELISA) Ab titers induced by E. coli MSP1(42) were significantly higher than those induced by the baculovirus-expressed antigen. None of the six monkeys that were vaccinated with the E. coli MSP1(42) antigen required treatment for uncontrolled parasitemia, but two required treatment for anemia. Protective immunity in these monkeys correlated with the ELISA Ab titer against the p19 fragment and the epidermal growth factor (EGF)-like domain 2 fragment of MSP1(42), but not the MSP1(42) protein itself or the EGF-like domain 1 fragment. Soluble MSP1(42) (FVO) expressed in E. coli offers excellent promise as a component of a vaccine against erythrocytic-stage falciparum malaria.  相似文献   
110.
The immunogenicity of recombinant protein or anti-viral DNA vaccines can be significantly improved by the addition of tandem copies of the complement fragment C3d. We sought to determine if the efficacy of a circumsporozoite protein (CSP)-based DNA vaccine delivered to mouse skin by gene gun was improved by using this strategy. Instead, we found that C3d suppressed the protective immunity against Plasmodium berghei malaria infection and deviated immunity, most notably by suppressing the induction of antibodies specific for the CSP C-terminal flanking sequence and by suppressing the induction of CSP-specific IL-4-producing spleen cells. We further showed that C3d bound to the C-terminal flanking sequence of the CSP, which may explain the immune deviation observed in CS/C3d chimeric antigen. We have thus identified C3d-mediated epitope masking and shifting of both the humoral and cellular immune responses as a potential novel escape mechanism, which plasmodia may use to divert the induction of protective immunity.  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