全文获取类型
收费全文 | 22048篇 |
免费 | 2081篇 |
国内免费 | 43篇 |
专业分类
耳鼻咽喉 | 193篇 |
儿科学 | 832篇 |
妇产科学 | 493篇 |
基础医学 | 2867篇 |
口腔科学 | 452篇 |
临床医学 | 2460篇 |
内科学 | 4521篇 |
皮肤病学 | 166篇 |
神经病学 | 2125篇 |
特种医学 | 757篇 |
外科学 | 3103篇 |
综合类 | 387篇 |
一般理论 | 12篇 |
预防医学 | 2441篇 |
眼科学 | 459篇 |
药学 | 1518篇 |
中国医学 | 26篇 |
肿瘤学 | 1360篇 |
出版年
2022年 | 142篇 |
2021年 | 341篇 |
2020年 | 203篇 |
2019年 | 394篇 |
2018年 | 392篇 |
2017年 | 260篇 |
2016年 | 318篇 |
2015年 | 340篇 |
2014年 | 578篇 |
2013年 | 868篇 |
2012年 | 1207篇 |
2011年 | 1222篇 |
2010年 | 675篇 |
2009年 | 600篇 |
2008年 | 1125篇 |
2007年 | 1220篇 |
2006年 | 1139篇 |
2005年 | 1114篇 |
2004年 | 1089篇 |
2003年 | 1068篇 |
2002年 | 1060篇 |
2001年 | 487篇 |
2000年 | 507篇 |
1999年 | 450篇 |
1998年 | 264篇 |
1997年 | 220篇 |
1996年 | 232篇 |
1995年 | 228篇 |
1994年 | 220篇 |
1993年 | 214篇 |
1992年 | 370篇 |
1991年 | 304篇 |
1990年 | 335篇 |
1989年 | 340篇 |
1988年 | 278篇 |
1987年 | 286篇 |
1986年 | 311篇 |
1985年 | 277篇 |
1984年 | 254篇 |
1983年 | 238篇 |
1982年 | 185篇 |
1981年 | 197篇 |
1980年 | 153篇 |
1979年 | 216篇 |
1978年 | 185篇 |
1976年 | 147篇 |
1975年 | 140篇 |
1974年 | 148篇 |
1973年 | 147篇 |
1972年 | 126篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
61.
The cattle major histocompatibility complex (MHC) class II DR gene product is a heterodimer encoded by the BoLA-DRA and -DRB3 genes. Several groups have isolated cDNA and genomic clones for these genes, but their full genomic organization has not been described. We used a combination of long-range polymerase chain reaction (PCR), cloning and sequencing to define the organization of the DRB3 gene on existing genomic clones and in genomic DNA. We estimate the size of the coding region to be 11.4 kbp. Sequencing of full-length PCR clones from two different haplotypes confirmed that they carried complete DRB3 genes and allowed the design of probes and primers to isolate and characterize the DRB3 promoter and 3' end. Fragments carrying the 5' end of the DRB3 gene and its promoter were identified on bacterial artificial chromosome (BAC) clones carrying the BoLA-DR genes. A 10-kbp promoter fragment was subcloned from one clone and a 1.7-kbp region including exon 1 and the promoter was sequenced. A 3-kbp fragment encoding exons 4-6 and the entire 3' untranslated region of the DRB3 gene was isolated from lambda clone A1 and sequenced. This provides us with improved characterization of the DRB3*0101 and DRB3*2002 alleles, and also subcloned 5' and 3' flanking regions of the polymorphic DRB3 gene for use in functional studies. 相似文献
62.
Frank P MacMaster Aileen Russell Yousha Mirza Matcheri S Keshavan S Preeya Banerjee Rashmi Bhandari Courtney Boyd Michelle Lynch Michelle Rose Jennifer Ivey Gregory J Moore David R Rosenberg 《Neuropsychopharmacology》2006,59(3):252-257
BACKGROUND: Abnormalities in the limbic-hypothalamic-pituitary-adrenal (LHPA) axis have been implicated in the pathogenesis of obsessive-compulsive disorder (OCD). To our knowledge, however, no prior study has measured pituitary gland volume in OCD. METHODS: Volumetric magnetic resonance imaging studies were conducted in 31 psychotropic drug-na?ve children (10 boys, 21 girls) aged 8-17 years and 31 case-matched healthy comparison subjects. RESULTS: Pituitary volume was significantly smaller in patients with OCD as compared with healthy control subjects (11% smaller). Smaller pituitary volume in patients with OCD was associated with increased compulsive but not obsessive symptom severity. Boys with OCD had smaller pituitary gland volumes compared with control boys (20% smaller). No significant differences in pituitary volume were observed between girls with OCD and control girls. Boys with OCD had significantly smaller pituitary volumes than girls with OCD (31% smaller), whereas control boys also had smaller pituitary gland volumes compared with control girls (21% smaller). CONCLUSIONS: These findings provide new evidence of reduced pituitary volume in pediatric OCD that seems to be more prominent in male patients. The observed alterations in pituitary volume are consistent with neuroendocrine studies that have reported abnormalities in the LHPA axis in OCD. 相似文献
63.
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
64.
Lynette K. Russell 《Journal of Midwifery & Women's Health》1992,37(1):17-24
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
65.
66.
P. M. Patel C. L. Flemming S. J. Russell I. A. McKay K. A. MacLennan G. M. Box S. A. Eccles M. K. Collins 《British journal of cancer》1993,68(2):295-302
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
67.
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
68.
69.
C F Russell 《The British journal of surgery》1992,79(9):861-862
70.
Gastrointestinal damage associated with the use of nonsteroidal antiinflammatory drugs. 总被引:29,自引:0,他引:29
M C Allison A G Howatson C J Torrance F D Lee R I Russell 《The New England journal of medicine》1992,327(11):749-754
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