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   14540篇
  免费   1282篇
  国内免费   43篇
耳鼻咽喉   119篇
儿科学   595篇
妇产科学   283篇
基础医学   1745篇
口腔科学   299篇
临床医学   1655篇
内科学   2840篇
皮肤病学   157篇
神经病学   1351篇
特种医学   757篇
外科学   2015篇
综合类   373篇
一般理论   18篇
预防医学   1383篇
眼科学   369篇
药学   1067篇
  1篇
中国医学   10篇
肿瘤学   828篇
  2022年   131篇
  2021年   235篇
  2020年   151篇
  2019年   252篇
  2018年   307篇
  2017年   232篇
  2016年   248篇
  2015年   304篇
  2014年   385篇
  2013年   531篇
  2012年   808篇
  2011年   800篇
  2010年   466篇
  2009年   404篇
  2008年   714篇
  2007年   712篇
  2006年   708篇
  2005年   671篇
  2004年   699篇
  2003年   577篇
  2002年   606篇
  2001年   370篇
  2000年   351篇
  1999年   331篇
  1998年   243篇
  1997年   218篇
  1996年   224篇
  1995年   153篇
  1994年   170篇
  1993年   172篇
  1992年   301篇
  1991年   262篇
  1990年   214篇
  1989年   229篇
  1988年   213篇
  1987年   218篇
  1986年   189篇
  1985年   184篇
  1984年   140篇
  1983年   116篇
  1982年   96篇
  1981年   96篇
  1980年   101篇
  1979年   89篇
  1978年   87篇
  1977年   84篇
  1976年   95篇
  1974年   75篇
  1973年   95篇
  1972年   87篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
The significance of life stress, coping, and social support was examined in relation to depressive symptomatology in a sample of 160 asymptomatic and mildly symptomatic HIV-antibody-positive (HIV+) men. The participants (mean age = 32 years) were interviewed about the life stress that they had experienced in the previous 6  相似文献   
13.
A commonly encountered problem in orthopedics is bone and cartilage tissue injury which heals incompletely or without full structural integrity. This necessitates development of improved methods for treatment of injuries which are not amenable to treatment using current therapies. An already large and growing number of growth factors which play significant roles in bone remodeling and repair have been identified in the past few years. It is well established that bone morphogenic proteins induce the production of new bone and cartilage. An efficient method of delivery of these growth factors by conventional pharmacological means has yet to be elucidated. We wished to evaluate the use of retroviral vector-mediated gene transfer to deliver genes of therapeutic relevance for bone and cartilage repair. To determine the feasibility of using amphotropically packaged retroviral vectors to transduce primary rabbit mesenchymal stem cells of periosteal origin, primary periosteal cells were isolated from New Zealand white rabbits, transduced in vitro with a retroviral vector bearing both the nuclear localized lacZ marker gene and the neo(r) gene, and selected in G418. We used a convenient model for analysis of in vivo stability of these cells which were seeded on to polymer scaffold grafts and implanted into rabbit femoral osteochondral defects. The nuclear localized beta-galactosidase protein was expressed in essentially 100% of selected cells in vitro and was observed in the experimental explants from animals after both 4 and 8 weeks in vivo, while cells transduced with a retroviral vector bearing only the neo(r) gene in negative control explants showed no blue staining. We extended our study by delivering a gene of therapeutic relevance, human bone morphogenic protein 7 (hBMP-7), to primary periosteal cells via retroviral vector. The hBMP-7 gene was cloned from human kidney 293 cell total RNA by RT-PCR into a retroviral vector under control of the CMV enhancer/promoter. Hydroxyapatite secretion, presumably caused by overexpression of hBMP-7, was observed on the surface of the transduced and selected periosteal cells, however, this level of expression was toxic to both PA317 producer and primary periosteal cells. Subsequently, the strong CMV enhancer/promoter driving the hBMP-7 gene was replaced in the retroviral vector by a weaker enhancer/promoter from the rat beta-actin gene. Nontoxic levels of expression of hBMP-7 were confirmed at both the RNA and protein levels in PA317 producer and primary periosteal cell lines and cell supernatants. This work demonstrates the feasibility of using a gene therapy approach in attempts to promote bone and cartilage tissue repair using gene-modified periosteal cells on grafts.  相似文献   
14.
Islet cell carcinomas of the pancreas: a twenty-year experience   总被引:16,自引:0,他引:16  
Unlike its lethal exocrine counterpart, islet cell carcinoma of the pancreas is an indolent neuroendocrine neoplasm. The majority of these tumors are hormonally active. When functioning, a number of clinical syndromes (for example, hyperinsulinism, Zollinger-Ellison and Cushing's syndromes) may be evident. Fifty-eight patients surgically treated between 1965 and 1984 were retrospectively analyzed. The purpose of this study was to determine the distribution of functioning versus nonfunctioning tumors and the response to type of therapy. Mean postoperative follow-up was 7.4 years. Survival and prognostic indices were calculated by the Kaplan-Meier method and compared with log-rank tests. Of the group, 54% had functioning and 46% nonfunctioning tumors. Gastrinomas were the most common functioning tumors encountered (19%). Of interest was the finding that nonfunctioning tumors increased steadily during the last 15 years of the study (25% to 65%). Curative resections were performed in 15 (26%) and noncurative procedures in 43 patients (74%), with an overall operative mortality rate of 3%. Symptomatic improvement was achieved in 90% (curative) and 51% (noncurative). Survival at 3 years was 87% and 66% for the curative and noncurative groups, respectively (p less than 0.1), with an overall 5-year survival of 42%. The absence of hepatic metastases was a major predictor of survival at 3 years (82% vs 56%, p less than 0.05). Survival was statistically better at 3 years in those patients with gastrinomas compared with patients with nonfunctioning tumors (91% vs 58%, p less than 0.05). Although surgical cure is rare, significant long-term palliation may be achieved in a large percentage of patients with an aggressive surgical approach, occasional total gastrectomy, combination chemotherapy, H2 blockade, when indicated, and, most recently, with the new long-acting analogue of somatostatin.  相似文献   
15.
16.
1. Epidermal growth factor is a potent mitogen that causes natriuresis, diuresis and inhibition of arginine vasopressin-induced water reabsorption. 2. The aim of this study was to determine any interaction between epidermal growth factor and the V1 (vascular) and/or V2 (antidiuretic) arginine vasopressin receptor subtypes. 3. Radioligand binding displacement assays demonstrated that although arginine vasopressin related peptides displaced both radioligands from renal medullary membranes at low concentrations epidermal growth factor displaced neither. 4. Arginine vasopressin V2 receptor second messenger cyclic adenosine monophosphate (CAMP) production was inhibited by epidermal growth factor (IC50 2 ± 10?7 mol/L) as was sodium fluoride cAMP production but only at much higher concentrations. 5. Therefore the diuretic effect of epidermal growth factor is not via direct antagonism of arginine vasopressin receptors but seems mediated via inhibition of the V2 second messenger system.  相似文献   
17.
18.
Aim This paper seeks to illumine how families with children and adult members with intellectual disabilities manage to manifest a buoyant and durable capacity over time. It is therefore concerned centrally with the idea of resilience. Method Drawing from diverse theoretical literatures from child development and protection and gerontology, the paper begins with a review of constructions of resilience. In an attempt to assess where there seems to be support for resilience in families, the core of the paper tests empirical evidence about positive experiences of families supporting children and adults with intellectual disabilities against the theoretical literature on resilience. Result and Conclusions The findings are used to suggest conditions under which resilience is produced and maintained, and to identify emergent elements of a psycho‐social model of resilience in families with children and adult members with intellectual disabilities.  相似文献   
19.
20.
The purpose of the study was to determine the epidemiological relationships in three unrelated cases of neonatal late-onset Group B streptococcal (GBS) disease and maternal breast-milk infection with GBS. All deliveries were by cesarean section; case 1 was at term, and cases 2 and 3 were at 32- and 33-wk gestation, respectively. Case 1 relates to a mother with clinical mastitis and recurrent GBS infection in a 20-day-old male infant. Following antibiotic therapy and cessation of breast-feeding, the infant recovered without sequelae. Case 2 refers to a mother with clinical mastitis and the occurrence of late-onset GBS disease in 5-wk-old male twins. Despite intervention, one infant died and the second became ill. Following antibiotic therapy and cessation of breast-feeding, the surviving infant recovered without sequelae. Case 3 refers to a mother with sub-clinical mastitis and late-onset GBS infection occurring in a 6-day-old female twin. Following intervention, the infant recovered but suffered a bilateral thalamic infarction resulting in developmental delay and a severe seizure disorder. Following recovery of GBS from an inapparent mastitis and cessation of breast-feeding, the second infant remained well. Blood cultures from all affected infants and maternal breast milk were positive for GBS. Epidemiological relationships between neonatal- and maternal-derived GBS isolates were confirmed by a random amplified polymorphic DNA polymerase chain reaction assay (RAPD-PCR). This study is significant in that it has demonstrated that maternal milk (in cases of either clinical or sub-clinical mastitis) can be a potential source of infection resulting in either late-onset or recurrent neonatal GBS disease.  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