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   11016篇
  免费   1073篇
  国内免费   40篇
耳鼻咽喉   61篇
儿科学   442篇
妇产科学   209篇
基础医学   1409篇
口腔科学   255篇
临床医学   1224篇
内科学   2140篇
皮肤病学   111篇
神经病学   773篇
特种医学   762篇
外国民族医学   1篇
外科学   2040篇
综合类   344篇
一般理论   12篇
预防医学   961篇
眼科学   180篇
药学   607篇
中国医学   10篇
肿瘤学   588篇
  2023年   84篇
  2022年   106篇
  2021年   231篇
  2020年   151篇
  2019年   216篇
  2018年   267篇
  2017年   201篇
  2016年   185篇
  2015年   225篇
  2014年   319篇
  2013年   464篇
  2012年   557篇
  2011年   577篇
  2010年   404篇
  2009年   328篇
  2008年   465篇
  2007年   514篇
  2006年   478篇
  2005年   420篇
  2004年   406篇
  2003年   387篇
  2002年   375篇
  2001年   238篇
  2000年   234篇
  1999年   219篇
  1998年   248篇
  1997年   222篇
  1996年   200篇
  1995年   171篇
  1994年   152篇
  1993年   135篇
  1992年   201篇
  1991年   192篇
  1990年   172篇
  1989年   185篇
  1988年   171篇
  1987年   154篇
  1986年   174篇
  1985年   164篇
  1984年   118篇
  1983年   113篇
  1982年   92篇
  1981年   70篇
  1980年   82篇
  1979年   99篇
  1978年   92篇
  1976年   75篇
  1975年   77篇
  1973年   72篇
  1972年   70篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
OBJECTIVES: To investigate outcome in children with mild traumatic head injury (THI) at 1 week and 3 months postinjury and to identify factors associated with persisting problems. DESIGN: Postconcussional symptomatology, behavior ratings, and neuropsychological test performance were examined at 1 week and 3 months postinjury. SETTING: Participants were recruited from successive presentations to emergency departments of two major hospitals. PARTICIPANTS: 130 Children with mild THI were compared with 96 children having other minor injuries as controls. RESULTS: Children with mild THI experienced headaches, dizziness, and fatigue but exhibited no cognitive impairments, relative to controls, at 1 week postinjury. By 3 months, symptoms had resolved. However, 17% of children showed significant ongoing problems. They were more likely to have a history of previous head injury, learning difficulties, neurological or psychiatric problems, or family stressors. CONCLUSIONS: Persisting problems following mild head injury in children are more common in those with previous head injury, preexisting learning difficulties, or neurological, psychiatric, or family problems. These "at-risk" children should be identified in the emergency department and monitored.  相似文献   
92.
Sertoli cells enhance the survival of co-transplanted dopamine neurons   总被引:5,自引:0,他引:5  
One of the major issues in neural transplantation is the low survival rate (<5%) of transplanted dopamine (DA) neurons [3]. Recently it has been shown that it is possible to enhance the survival of these neurons, which in turn may decrease the amount of tissue that is required for each transplantation patient. The present paper demonstrates a novel approach for enhancing neuronal survival by co-transplantation of neuronal tissue with Testis-derived Sertoli cells (SC). This strategy could improve neuronal survival through the provision of trophic support.  相似文献   
93.
BACKGROUND: Percutaneous renal biopsy, based on the use of an aspiration needle and the patient in the sitting position, was first described by Iversen and Brun in 1951. In 1954, Kark and Muehrcke described the use of the cutting Vim-Silverman needle on patients in the prone position, with a substantial improvement in the rate of success. The 1961 CIBA Foundation Symposium on renal biopsy marked the coming of age of this technique. During the 1950s in Italy, several individuals played a part in promoting and developing percutaneous renal biopsy. Because this pioneer work has received insufficient attention, we describe the contributions of Italians to the early introduction of this technique. METHODS: The Italian and international literature about percutaneous renal biopsy of the period 1951 through 1965 was reviewed. In addition, structured interviews with surviving members of the Italian researchers who first used renal biopsy were conducted. RESULTS: The first renal biopsies in Italy were performed in 1951 in Pisa by the group of Ernico Fiaschi (1913-1989). In their hands, renal biopsy became a tool to investigate the pathogenesis of renal diseases in particular, while simultaneously using the early application of immunofluorescence and electron microscopy. In 1954, Pietro Leonardi (1914-1991) and Arturo Ruol (born 1924) introduced renal biopsy in Padova; they used this technique extensively and published one of the first monographs on the subject. In 1957, Vittorio Bonomini (born 1928) introduced renal biopsy in Bologna, and in subsequent years used this technique to focus on the study of pyelonephritis. CONCLUSIONS: Our historical research shows that Italian groups were among the first to use and develop percutaneous renal biopsy both as a clinical tool and an investigative tool. This article gives international credit to their work.  相似文献   
94.
95.
In April 1998 an outbreak of salmonellosis amongst guests at a wedding feast was investigated. Of the 58 attendees interviewed 38 (66%) subsequently developed gastrointestinal symptoms. Stool cultures from 7 cases grew Salmonella Typhimurium RDNC A045. Food samples were culture-negative for Salmonella spp. A cohort study implicated spatchcock (RR 2.5, 95% CI 1.09-5.77) and scampi (RR 2.0, 95% CI 1.05-3.89). Temperature abuse and cross-contamination within the kitchen during preparation and cooking are likely to have been the main contributing factors to this outbreak. Control measures included staff education in safe food handling and improvements in poultry processing methods to minimise carcass contamination.  相似文献   
96.

Purpose

We evaluated the use of renal ultrasound for monitoring pyelocaliectasis after pyeloplasty in children.

Materials and Methods

Changes in pyelocaliceal dilatation following pyeloplasty were assessed by serial ultrasound. Of 104 children 0 to 12 years old who underwent pyeloplasty between 1982 and 1992, 44 (47 renal units) were monitored with serial ultrasound for at least 2 years (range 2 to 9, mean 3.8). Patient ages at pyeloplasty were 0 to 3 months (17), 4 to 12 months (8), 1 to 6 years (13) and 7 to 12 years (6). Preoperative and postoperative ultrasound was reviewed by a single pediatric radiologist blinded to the date of surgery. The degree of pyelocaliectasis was graded as 0 to 4 according to the classification of the Society for Fetal Urology.

Results

Preoperative ultrasound revealed grade 4 pyelocaliectasis in 26 kidneys (55 percent) and grade 3 disease in 21 (45 percent). Grade was the same or worse 1 month after pyeloplasty in the majority of kidneys (92 percent) studied at this interval. Of the 47 renal units assessed 43 (91 percent) showed improvement in pyelocaliectasis during postoperative followup. Only 38 percent of the kidneys improved during the first 6 months of followup, while 81 percent were improved 2 years postoperatively. Improvement to grade 0 or 1 dilatation occurred in only 9 kidneys (19 percent). The rate of resolution of pyelocaliectasis was not related to preoperative grade or patient age at pyeloplasty.

Conclusions

Improvement on renal ultrasound after pyeloplasty appears to be gradual. Less than half of the patients had improvement in the initial 6 months after pyeloplasty and pyelocaliectasis rarely resolved completely. While renal ultrasound can provide an accurate and cost-effective means of monitoring children on a long-term basis after pyeloplasty, sonographic evaluation in the early postoperative period commonly shows increased or unchanged pyelocaliectasis.  相似文献   
97.
98.
The vasa vasorum and angioplasty   总被引:2,自引:0,他引:2  
Interruption of flow in the vasa vasorum may lead to medial necrosis and aneurysm formation. The purpose of this study was to determine whether angioplasty produces significant alterations in the morphology or blood flow of the vasa vasorum of the dilated artery. The morphology of the canine vasa vasorum was studied before and after angioplasty; in a separate experiment vessel wall blood flow (VWBF) in canine carotid arteries was measured after angioplasty to determine whether physiologic regulation of the blood flow was disrupted by arterial dilation. No morphologic changes could be demonstrated in the vasa vasorum of the dilated artery; however, VWBF was increased by 1194 +/- 215% (mean +/- standard error, p less than 0.01) between 90 and 120 minutes after angioplasty. VWBF in the adjacent nondilated arterial segment was also increased (720 +/- 177% between 10-30 minutes, p less than 0.01) but returned toward normal after 60 minutes. Adenosine caused a "paradoxical" decrease in VWBF (p less than 0.05) of the dilated arterial segment while causing increased VWBF (p less than 0.05) in the thoracic aorta. Angioplasty appears to produce persistent hyperemia in the dilated arterial wall. A paradoxical response to adenosine suggests that vasa vasorum in the dilated arterial segment are maximally vasodilated. This may be due to mechanical disruption of vasomotor tone or to release of vasoactive substances.  相似文献   
99.
Climatic droplet keratopathy with corneal amyloidosis   总被引:1,自引:0,他引:1  
Climatic droplet keratopathy (CDK) is a degenerative disease of the cornea, highly prevalent in Saudi Arabia. It is characterized by aggregates of small, golden-yellow globules that accumulate in the subepithelial layers, Bowman's layer, and the superficial stroma of the cornea. The authors report on 22 patients (40 eyes) with CDK and lattice lines in the cornea. The condition occurred late in life (mean age, 67 years). It was bilateral in 82% of patients, with no family history of lattice dystrophy or systemic amyloidosis. These lines were found in all layers of the stroma. Results of histopathologic and electron microscopic examination of the lattice lines confirmed the presence of amyloid. Results of immunohistochemical examination showed evidence of deposition of AP protein. The cause of these deposits in the cornea is not known, but the authors speculate that environmental factors causing CDK also may play a role in the deposition of protein AP in the cornea. The contribution of trachoma to the degenerative changes in the cornea and secondary amyloidosis could not be ruled out, as all patients had inactive trachoma. Climatic droplet keratopathy with corneal amyloidosis, therefore, represents a form of "lattice degeneration" of the cornea.  相似文献   
100.
Organotin compounds have been shown to interfere with cardiovascular system. We have studied the in vitro and in vivo effects of tributyltin bromide (TBT), triethyltin bromide (TET) and trimethyltin chloride (TMT) on the cardiac SR Ca2+ pump, as well as on protein phosphorylation of SR proteins, in order to understand the relative potency of these tin compounds. All the three tin compounds inhibited cardiac SR45Ca uptake and Ca2+-ATPase in vitro in a concentration-dependent manner. The order of potency for Ca2+-ATPase as determined by IC50, is TBT (2 M) > TET (63 M) > TMT (280 M). For45Ca uptake, it followed the same order i.e., TBT (0.35 M) > TET (10 M) > TMT (440 M). In agreement with the in vitro results, both SR Ca2+-ATPase and45Ca uptake were significantly inhibited in rats treated with these tin compounds, indicating that these tin compounds inhibit cardiac SR Ca2+ transport. cAMP significantly elevated (70–80%) the32P-binding to SR proteins in vitro in the absence of any organotin. In the presence of organotins, cAMP-stimulated32P-binding to proteins was significantly reduced, but the decrease was concentration dependent only at lower concentrations. The order of potency is TBT > TET > TMT. In agreement with in vitro studies, cAMP-dependent32P bound to proteins was significantly reduced in rats treated with TBT, TET and TMT. SDS-polyacrylamide gel electrophoresis of the cardiac SR revealed at least 30 Coomassie blue stainable bands ranging from 9 to 120 kDa. Autoradiographs from samples incubated in the presence of cAMP indicated32P incorporation in seven bands. Of these, the band corresponding to about 24 kDa molecular weight protein decreased in its intensity with the treatment of organotins. These results suggest that triorganotins may be affecting Ca2+ pumping mechanisms through the alteration of phosphorylation of specific proteins in rat cardiac SR.This work has been presented in part at the Annual meeting of Society of Toxicology, 1990 at Miami Beach, FL. The Toxicologist 10: 35 & 108 (1990).  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