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   22148篇
  免费   2112篇
  国内免费   43篇
耳鼻咽喉   193篇
儿科学   831篇
妇产科学   493篇
基础医学   2903篇
口腔科学   448篇
临床医学   2471篇
内科学   4530篇
皮肤病学   168篇
神经病学   2125篇
特种医学   760篇
外科学   3141篇
综合类   389篇
一般理论   12篇
预防医学   2450篇
眼科学   468篇
药学   1534篇
中国医学   26篇
肿瘤学   1361篇
  2022年   142篇
  2021年   342篇
  2020年   205篇
  2019年   394篇
  2018年   389篇
  2017年   260篇
  2016年   318篇
  2015年   342篇
  2014年   578篇
  2013年   872篇
  2012年   1207篇
  2011年   1228篇
  2010年   678篇
  2009年   606篇
  2008年   1128篇
  2007年   1223篇
  2006年   1147篇
  2005年   1121篇
  2004年   1092篇
  2003年   1071篇
  2002年   1060篇
  2001年   486篇
  2000年   511篇
  1999年   457篇
  1998年   264篇
  1997年   223篇
  1996年   234篇
  1995年   228篇
  1994年   220篇
  1993年   215篇
  1992年   374篇
  1991年   310篇
  1990年   337篇
  1989年   340篇
  1988年   277篇
  1987年   285篇
  1986年   309篇
  1985年   277篇
  1984年   253篇
  1983年   241篇
  1982年   189篇
  1981年   197篇
  1980年   153篇
  1979年   219篇
  1978年   186篇
  1977年   129篇
  1976年   147篇
  1975年   141篇
  1974年   148篇
  1973年   147篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
We have examined the actions of vasoactive intestinal peptide (VIP) and certain other known immune modulators on a nuclear pool(s) of protein kinase C (PKC) in isolated rat splenocyte nuclei. Rat splenocyte nuclei pure by enzymatic and electron microscope criteria demonstrated a time- and concentration-dependent activation of nuclear PKC (nPKC) by VIP. A biphasic pattern of three bell-shaped curves was observed with peak phosphorylation at 10−15, 10−9 and 10−6M VIP. The phosphorylation of endogenous nuclear substrates was characterized as a PKC-mediated event by use of three known PKC inhibitors, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7), sphingosine, and staurosporine, which produced similar phosphate incorporation measurements. Also, this activity was blocked with the addition of a monoclonal antibody to PKC. Inhibitors of the ability of VIP to activate nPKC included somatostatin, 8-bromo-cAMP, peripheral benzodiazepine receptor modulators, and the PKC inhibitors, sphingosine and staurosporine. These data have direct relevance to our knowledge of cell-mediated immunity.  相似文献   
72.
This paper reviews the important concepts about varicella-zoster virus (VZV) infection, varicella (chickenpox), and herpes zoster (shingles, zoster) during pregnancy and the peripartum period. The majority of the U.S. population has had chickenpox during childhood, leaving only about 10% of adults over the age of 15 susceptible to the virus. However, nonimmune adults, including pregnant women, are at greater risk for complications and mortality when they contrac varicella. The virus is also teratogenic. The implication of VZV infection during pregnancy and the perinatal period are presented. Risks such as varicella pneumonia and congenital defects can be serious even though the incidence during pregnancy is low, one to five per 10,000 pregnancies. Management and treatment plans are presented. Counseling and education aimed at prevention or modification of the infection in the mother and baby is outlined.  相似文献   
73.
74.
Engineering of a variety of rodent tumour cells to secrete either interleukin 2 (IL-2), or interleukin 4 (IL-4), has been demonstrated to reduce their tumorigenicity. However the mechanisms of action of secreted IL-2 and IL-4 have not been compared in a single rodent tumour. Here we demonstrate that the weakly immunogenic murine fibrosarcoma FS29 had reduced growth rate and in some cases was rejected by syngeneic animals, when modified to secrete either IL-2 or IL-4, but not IL-5. Immunohistochemical analysis of tumour nodules undergoing regression showed stimulation of a largely lymphocytic infiltrate by IL-2 and a macrophage and granulocyte infiltrate, with a small number of lymphocytes by IL-4. Indeed, secretion of low levels of IL-2 and IL-4 in combination resulted in optimal rejection, suggesting that the two cytokines might mobilise different and complementary effector cell mechanisms. Both IL-2 and IL-4-secreting cells failed to induce the rejection of admixed, unmodified FS29 cells. The loss of cytokine secreting cells from such admixtures occurred more rapidly for IL-2-secreting cells. Injection of IL-4-secreting, but not IL-2-secreting FS29 cells could protect mice from a delayed challenge with unmodified FS29 cells. These data suggest that IL-4 secretion stimulates the better long-term host anti-tumour response.  相似文献   
75.
The effect of attention on memory was examined in three studies. In all three, the subjects were instructed to remember the items of one color from an array that contained items of two colors. Subsequently, the subjects were asked to reproduce items of both colors. Almost all of the items that the subjects remembered were those to which they had attended. The parameters of sex, color, and mode of presentation (verbal and drawing) were not significant. Head injury did not disrupt this effect. On the basis of this effect, it was theorized that the strength of a memory store is related directly to the strength of attention.  相似文献   
76.
Menorrhagia management options.   总被引:1,自引:0,他引:1       下载免费PDF全文
A prospective study of the management of menorrhagia in new patients presenting to gynaecological outpatients was undertaken at four centres in Northern Ireland and two in Great Britain. 325 patients were enrolled, the majority of whom (87%) had severe menorrhagia. Patients in all six centres were similar in relation to age, marital status, parity, use of contraception and severity of symptoms. 62% of the patients were managed medically, improved and were discharged. The rates of surgical intervention, in particular in women aged less than 40, appeared higher in the Northern Ireland hospitals than Great Britain. There is a need to review and audit current practices in the management of menorrhagia.  相似文献   
77.
78.
79.
80.
BACKGROUND. Long-term use of nonsteroidal antiinflammatory drugs (NSAIDs) may lead to inflammation of the small intestine associated with occult blood and protein loss. The aim of this study was to investigate the prevalence and structural correlates of this enteropathy. METHODS. We examined the stomach, duodenum, and small intestine of 713 patients post mortem. Of these patients, 249 had had NSAIDs prescribed during the six months before death and 464 patients had not. All visible small intestinal lesions were removed for histologic examination, and specific etiologic factors were sought. The prevalence of nonspecific small-intestinal ulcers and ulcers of the stomach and duodenum was compared in the two groups of patients. RESULTS. Nonspecific small-intestinal ulceration was found in 21 (8.4 percent) of the users of NSAIDs and 3 (0.6 percent) of the nonusers (difference, 7.8 percent; 95 percent confidence interval, 5.0 to 10.6 percent; P less than 0.001). Three patients who were long-term users of NSAIDs were found to have died of perforated nonspecific small-intestinal ulcers. Ulcers of the stomach or duodenum were found in 54 (21.7 percent) of the patients who used these drugs and 57 (12.3 percent) of those who had not (difference, 9.4 percent; 95 percent confidence interval, 3.9 to 15.1 percent; P less than 0.001). CONCLUSIONS. Patients who take NSAIDs have an increased risk of nonspecific ulceration of the small-intestinal mucosa. These ulcers are less common than ulcers of the stomach or duodenum, but can lead to life-threatening complications.  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