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   862058篇
  免费   70650篇
  国内免费   1840篇
耳鼻咽喉   12801篇
儿科学   24626篇
妇产科学   25096篇
基础医学   124210篇
口腔科学   25486篇
临床医学   75305篇
内科学   164617篇
皮肤病学   16973篇
神经病学   70107篇
特种医学   35201篇
外国民族医学   171篇
外科学   136157篇
综合类   24605篇
现状与发展   2篇
一般理论   263篇
预防医学   66865篇
眼科学   20517篇
药学   64688篇
中国医学   1595篇
肿瘤学   45263篇
  2018年   7334篇
  2015年   7724篇
  2014年   11105篇
  2013年   16783篇
  2012年   22712篇
  2011年   23827篇
  2010年   13861篇
  2009年   13060篇
  2008年   22567篇
  2007年   24616篇
  2006年   24485篇
  2005年   24133篇
  2004年   23696篇
  2003年   22827篇
  2002年   21923篇
  2001年   35826篇
  2000年   36465篇
  1999年   30893篇
  1998年   9219篇
  1997年   8545篇
  1996年   8475篇
  1995年   8006篇
  1994年   7723篇
  1992年   26662篇
  1991年   26109篇
  1990年   25620篇
  1989年   24680篇
  1988年   23220篇
  1987年   22883篇
  1986年   21740篇
  1985年   21097篇
  1984年   16385篇
  1983年   13996篇
  1982年   8854篇
  1981年   8201篇
  1980年   7671篇
  1979年   16737篇
  1978年   12114篇
  1977年   10182篇
  1976年   9328篇
  1975年   10147篇
  1974年   12641篇
  1973年   12137篇
  1972年   11538篇
  1971年   10685篇
  1970年   10218篇
  1969年   9909篇
  1968年   8900篇
  1967年   8231篇
  1966年   7654篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
PCP and related compounds inhibit 3H-mazindol binding to the cocaine receptor on dopamine transporters. The relative potencies of these compounds are such that some of the behavioral effects of PCP could be related to its action at the cocaine receptor; however, the affinity of PCP at the cocaine site (Ki = 1.59 microM) is less than its affinity at its own receptor (Ki about 0.12 microM). More data will be needed to conclusively implicate the cocaine receptor in the action of PCP.  相似文献   
63.
64.
65.
Treatment versus no treatment in chronic open angle glaucoma   总被引:1,自引:0,他引:1  
In a controlled randomized study 15 patients (20 eyes) with chronic open angle glaucoma and visual field defects were followed by greater than 1 year, 12 of them were followed for 3 years. Half of the group were untreated controls, the other half treated with pressure reducing medical therapy. At least 5 consecutive computerized visual fields were recorded (COMPETER) on each eye, and the linear regression coefficient was calculated. With the reservation for uncontrolled compliance no significant difference in the line of favourable effect of pressure reduction could be spotted, in spite of an average pressure reduction in the treated group of 4 mmHg. More important than this result, which is open to criticism for the smallness of the material, uncontrolled compliance etc, is the lesson that a randomized experiment with treated and non-treated glaucoma cases carried out in accordance with the Helsingfors convention is hardly feasible.  相似文献   
66.
67.
Polyploidization and centrosome hyperamplification in inflammatory bronchi   总被引:1,自引:0,他引:1  
OBJECTIVE AND DESIGN: Inflammatory and tumorous bronchi were screened in order to obtain new tumor relevant cytogenetic parameters. MATERIAL OR SUBJECTS: Bronchial cells of 32 patients were cultivated by standard cell culture procedures. METHODS: Tetraploidy and aneuploidy was determined by enumeration of chromosome 7 and 8 versus the number of centrosomes. The resulting data were correlated with histopathological data. RESULTS: Tetra- and aneuploidy of epithelial cells were detectable in 76% of tumor cell cultures, 75% of high grade inflammatory tissues and 40% of non- and low grade-inflammatory tissues. Additionally, we observed centrosome hyper-amplification and multipolar mitoses not only in the tumor but also in the early stages of inflammation. CONCLUSION: Inflammatory bronchi already show tumor-specific features and may consequently represent the preliminary genetic stage of cancer development in bronchi.  相似文献   
68.
OBJECTIVES: The incidence of bacterial microleakage, pulp inflammation and necrosis associated with dentine etching treatments prior to restoration are not known. Consequently, to resolve some of the controversy surrounding the effects and importance of vital dentine etching, the authors investigated these factors. METHODS: 110 standardised class V cavities were cut into buccal dentine, without exposing the pulp of teeth scheduled for extraction for orthodontic reasons. Cavities were either left unetched, or etched with the non-equivalent treatments of phosphoric acid gel for 60s or Ethylenediaminetetraacetic acid (EDTA) for 30s, prior to placement of composite resin. Teeth were collected and pulp responses were evaluated according to ISO guidelines, using pathohistomorphometric analysis and ANOVA statistics. RESULTS: Etching was found to be correlated to bacterial microleakage (p=0.0001) and tertiary dentine formation (p=0.0023). Bacterial microleakage was correlated to inflammatory activity (p=0.0001). The frequency of bacterial microleakage was: no etching (65%), EDTA (51%) and phosphoric acid (PA) (20%). SIGNIFICANCE: Vital dentine etching treatment is of extreme importance for the placement of RC to minimise bacterial microleakage. PA etching proved to be more effective at preventing bacterial microleakage than non-etching, and etching with EDTA.  相似文献   
69.
The infertility distress scale (IBS) has been designed to assess the stress perceived by andrological patients resulting from infertility. This review presents findings from different studies with a total of 769 patients. The scale consists of eight items. The stability of scores is very high even for a mean follow-up of 2 years. The scale correlates highly with an already validated measure of infertility distress. Correlations with measures of depressiveness are in the low to medium range. All in all, the psychometric results indicate that the IBS is a factor-stable, reliable and valid instrument for assessing chronic infertility distress in andrological patients. After the presentation of normative data, the usefulness of the IBS as a screening instrument for identifying highly distressed patients is discussed. Findings supporting the scale's sensitivity to change are also presented. The scale is a useful tool in clinical practice as well as in research.  相似文献   
70.
BACKGROUND: The responses of mice to the mite allergen Der p 1 have been used to study the mechanisms of allergic sensitization and the development of new types of immunotherapy. Many of the studies require a knowledge of the T cell epitopes, and because Der p 1 is polymorphic, the effect of natural amino acid substitution in the allergen. The intranasal administration of peptides containing T cell epitopes can induce a mucosal tolerance but it is not known if the major activity is limited to stimulatory peptides and if, as found for autoimmunity, some epitopes are not inhibitory. OBJECTIVE: To determine and compare the sequences of Der p 1 which contain stimulatory epitopes for the high responding H-2(b) and H-2(q) mice and the sequences which induce tolerance by intranasal administration of peptides. METHODS: T cell responses of mice immunized with Der p 1 were measured by in vitro T cell stimulation assays so an extensive study of epitope recognition and intranasal tolerance could be made. Synthetic peptides were used to examine the stimulatory and inhibitory ability of all Der p 1 sequences and to map the major H-2(b) epitope in detail. This included the effect of the common polymorphic amino acid 124 substitution found within this epitope. RESULTS: Three and two regions, respectively, were found to contain stimulatory T cell epitopes for H-2(b) and H-2(q) mice. The peptides in these regions were also the most active at inducing intranasal tolerance for the responding haplotype. The correspondence between inhibitory and stimulatory peptides was maintained for the fine mapping of the major H-2(b) epitope. This was found about a core region of 118-126 which was overlapping but separate to a consensus sequence for the binding of endogeneous peptides. Peptides with alanine at the naturally polymorphic residue 124 stimulated and inhibited responses to Der p 1 more effectively, while peptides with the valine 124 variant were immunogenic but poorly cross-reactive. CONCLUSIONS: The intranasal administration of peptides representing each of five epitopes recognized by two strains of mice were able to induce mucosal tolerance and the major tolerizing activity was limited to these epitopes. The position of the core major epitope for C57 mice, which differs from a previously predicted epitope, and its specificity for the natural alanine 124 variant is described.  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