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   3348篇
  免费   112篇
耳鼻咽喉   13篇
儿科学   75篇
妇产科学   111篇
基础医学   223篇
口腔科学   81篇
临床医学   675篇
内科学   920篇
皮肤病学   135篇
神经病学   120篇
特种医学   3篇
外科学   364篇
综合类   16篇
一般理论   27篇
预防医学   275篇
眼科学   50篇
药学   309篇
中国医学   1篇
肿瘤学   62篇
  2017年   21篇
  2016年   48篇
  2015年   55篇
  2014年   58篇
  2013年   131篇
  2012年   33篇
  2010年   97篇
  2009年   108篇
  2008年   28篇
  2007年   32篇
  2006年   47篇
  2005年   21篇
  2003年   18篇
  2001年   44篇
  2000年   36篇
  1999年   106篇
  1998年   133篇
  1997年   200篇
  1996年   212篇
  1995年   148篇
  1994年   110篇
  1993年   111篇
  1992年   99篇
  1991年   108篇
  1990年   87篇
  1989年   104篇
  1988年   92篇
  1987年   65篇
  1986年   72篇
  1985年   67篇
  1984年   69篇
  1983年   59篇
  1982年   65篇
  1981年   73篇
  1980年   62篇
  1979年   57篇
  1978年   46篇
  1977年   41篇
  1976年   48篇
  1975年   27篇
  1974年   31篇
  1971年   25篇
  1970年   18篇
  1968年   18篇
  1959年   20篇
  1958年   27篇
  1957年   26篇
  1956年   25篇
  1955年   26篇
  1954年   22篇
排序方式: 共有3460条查询结果,搜索用时 46 毫秒
51.
52.
Sex differences in home range size and spatial ability are predictive of sex differences in the relative size of the hippocampus in rodents. Such differences in behavior and hippocampal volume are presumed to be, in part, the result of differences in perinatal exposure to hormones. We predicted from differences in the size of home ranges of male and female Mongolian gerbils (Meriones unguiculatus) in the wild that the hippocampus of male gerbils would be relatively larger than that of females. We examined the effect of prenatal hormonal influences on hippocampal size by comparing hippocampal volume of males and females from 2F and 2M intrauterine positions to that of randomly selected males and females. We found that, as predicted, randomly selected males had a significantly larger hippocampus, relative to telencephalon, than did randomly selected females. However, males and females from 2F and 2M intrauterine positions did not differ in relative hippocampal size. Possible explanations for the absence of a sex difference in hippocampal size in male and female gerbils from 2F and 2M intrauterine positions are discussed.  相似文献   
53.
This article examines the state of the art in health promotionindicator development over the past few years and presents fiveconclusions from this review, The authors put forward proposalsfor the development of health promotion indicators based onthe question, "What research in health promotion will lead toappropriate indicators?". The authors illustrate some areasof concern both for researchers and policymakers and suggesta number of indicators, appropriate to each of these groups,for important dimensions of health, health-related processesand health resources. The dialogue between health researchersand health decision-makers is growing and links are being made;it is important to continue this process.  相似文献   
54.
Guthrie R M, Ruoff G E, Rofman BA, Ginsberg D, Karp R R, BrownS M and Schulz GA. Aetiology of acute pharyngitis and clinicalresponse to empirical therapy with erythromycin versus amoxicillin.Family Practice 1988; 5: 29–35. One hundred and eighty-nine adults with acute pharyngitis hadculture and serological evaluation for groupA beta haemolyticstreptococci (GABHS), Mycoplasma pneumoniae, and Branhamellacatarrhalis. Sixteen patients had evidence for infection withGABHS, none for M. pneumoniae, and one for B. catarrhalis. Forthose with GABHS, there was no significant difference betweenempirical treatment by erythromycin or amoxicillin. For thosewithout GABHS, empirical treatment with erythromycin appearedto result in a statistically significant reduction in coughand a noticeable but less than significant reduction of othersymptoms when compared to empirical treatment with amoxicillin.The new formula tion of erythromycin utilized in this study(PCE) may be associated with a reduction in gastrointestinalintolerance from that reported with other erythromycin products.  相似文献   
55.
PROBLEM: Infection has been proposed to initiate abortion, and the role of viruses in spontaneous resorption in mice has not been tested. METHOD: The anti-viral drug ribavirin (1-β-D-ribofuranosyl-1,2,4-triazole-3-carboxamide) was fed to CBA/J and C3H/HeJ female mice beginning on the morning after mating with DBA/2J males. RESULTS: Ribavirin treatment increased the rate of abortion (resorption) on day 13.5, and this was associated with retardation of the rate of embryo development and hypoplasia of the trophoblast. There was a reduction in trophoblast-dependent decidua-associated soluble suppressor activity, but there was no maternal mononuclear cell infiltrate of the type reported in association with resorption of semiallogeneic and xenogeneic mouse embryos. This may be due to an immunosuppressive effect of ribavirin. Ribavirin was able to potently suppress proliferation of mouse trophoblast and mastocytoma cell lines in vitro. CONCLUSIONS: There are several drug-induced murine abortion models that provide useful insights into potential mechanisms underlying spontaneous pregnancy failure, but in the ribavirin model, a direct impairment of trophoblast development appears to be responsible.  相似文献   
56.
Alpha‐fetoprotein (AFP) is the major serum protein during development. AFP is one of the earliest proteins to be synthesised by the embryonic liver. The synthesis of AFP decreases dramatically after birth and only trace amounts are expressed in the adult liver. The tissue distribution of AFP in early human embryogenesis has not been defined. We have studied the expression pattern of AFP mRNA in human and mouse embryos by in situ hybridisation. In humans, AFP is expressed in the hepatic diverticulum at 26 d postovulation as it differentiates from the foregut endoderm (i.e. in the most primitive hepatocytes). It is also expressed in the endoderm of the gastrointestinal tract and in the yolk sac at this age. AFP is subsequently expressed in the mesonephros and transiently in the developing pancreas. In the mouse, no expression of AFP was observed in the mesonephros but other sites of expression were similar. Thus AFP has a distinct temporospatial expression pattern during the embryonic period and this differs between human and mouse species. It is interesting that AFP is expressed by tumours such as primitive gastrointestinal, renal cell and pancreatic tumours as well as those of hepatocyte origin. This distribution reflects the sites of AFP expression during development.  相似文献   
57.
Immunohistochemistry using the PC10 antibody to proliferating cell nuclear antigen (PCNA) was applied to archival material from mucosa adjacent to gastric carcinoma ('normal', hyperplasia, complete and incomplete intestinal metaplasia and dysplasia) and non-cancer controls (normal and complete intestinal metaplasia). Overall, increased PCNA indices, with expansion and altered location of the proliferative zones, were observed in carcinoma fields and compared with controls ( P ≤0.001). These differences were particularly significant in 'normal' mucosa far from carcinoma as compared with normal in controls ( P ≤0.001). In carcinoma 'fields' distinct patterns of PCNA expression were noted in complete and incomplete intestinal metaplasia. Similarly, in dysplastic lesions high PCNA indices were present either throughout the gland or found predominantly in the upper compartment. We conclude that these differences in PCNA index and staining patterns might prove useful in monitoring the evolution of the disease in the follow-up of patients at risk of developing gastric cancer.  相似文献   
58.
ABSTRACT: Antisperm antibodies may play a role in the pathogenesis of infertility, particularly in the male. One of the standardized methods for detecting antisperm antibodies is the tray agglutination test (TAT). Unfortunately, this assay requires fresh motile spermatozoa. Tests for binding of antibody to fixed sperm or sperm extracts have been developed as enzyme-linked immunosorbent assays (ELISA), and we compared the results of using one such ELISA method with the TAT to detect antisperm antibodies in a panel of known positive and negative sera from infertile and control patients. With respect to the TAT assay, the ELISA gave a 75% false-positive test rate and a 63% false-negative rate. It is important to validate new assays such as the ELISA before widespread application to patient screening particularly since patients judged to have antisperm antibodies may be treated with high-dose corticosteroid drugs that are not without significant side effects.  相似文献   
59.
Cerebral blood flow (CBF) and oxygen consumption (CMRO2) were measured during acute and long-term ethanol intoxication in the rat. The purpose was to investigate whether the adaptive changes (development of tolerance) occurring in the CNS during ethanol intoxication were associated with changes in CBF and/or CMRO2. Consistent with other studies we found that acute severe ethanol intoxication (median blood alcohol concentration (BAC=5.4 mg/ml)) caused a significant decrease in CBF and CMRO2. After 3–4 days of severe intoxication (BAC of 6.6 mg/ml) these physiological variables were less affected indicating that functional tolerance had developed: CMRO2 and CBF during acute ethanol intoxication were 9.3 ml/100 g/min and 60 ml/100 g/min respectively; after the long term intoxication period these variables reached 11.2 ml/100 g/min and 78 ml/100 g/min respectively, i.e. values not significantly lower than those of the control group. After induction of hypercapnia (PaCO2 about 80 mmHg) CBF increased by 360% in the control group; in the acutely intoxicated group CBF increased by only 127% and in the long term intoxicated group by 203 % indicating that the cerebrovascular CO2-reactivity had also adapted to the ethanol intoxication. It is concluded that adaptive changes of the CNS to chronic ethanol intoxication comprise alterations in CMRO2, CBF and cerebrovascular reactivity.  相似文献   
60.
Diagnostic criteria for opioid dependence is presented. Five methods are described to assess the presence and/or severity of the opioid dependence syndrome:
  • 1 Self-report.
  • 2 Physical examination
  • 3 Toxicological analysis
  • 4 Observation of withdrawal symptoms
  • 5 Naloxone (Narcan) test.
Problems in determining actual amounts of heroin in “street deals’ is also discussed. It is emphasised that assessment of heroin-related problems in particular, requires a comprehensive lifestyle assessment in addition to the specific diagnosis of opioid dependence based largely on physical symptomatology as outlined in this paper.  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