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   9958篇
  免费   889篇
  国内免费   31篇
耳鼻咽喉   65篇
儿科学   366篇
妇产科学   306篇
基础医学   1282篇
口腔科学   80篇
临床医学   1436篇
内科学   1850篇
皮肤病学   117篇
神经病学   1122篇
特种医学   182篇
外科学   891篇
综合类   84篇
一般理论   15篇
预防医学   1700篇
眼科学   89篇
药学   734篇
中国医学   3篇
肿瘤学   556篇
  2024年   28篇
  2023年   174篇
  2022年   180篇
  2021年   352篇
  2020年   274篇
  2019年   382篇
  2018年   407篇
  2017年   353篇
  2016年   384篇
  2015年   331篇
  2014年   455篇
  2013年   634篇
  2012年   852篇
  2011年   867篇
  2010年   451篇
  2009年   341篇
  2008年   612篇
  2007年   639篇
  2006年   554篇
  2005年   484篇
  2004年   457篇
  2003年   401篇
  2002年   375篇
  2001年   82篇
  2000年   59篇
  1999年   67篇
  1998年   71篇
  1997年   47篇
  1996年   58篇
  1995年   41篇
  1994年   37篇
  1993年   39篇
  1992年   42篇
  1991年   34篇
  1990年   41篇
  1989年   33篇
  1988年   29篇
  1987年   18篇
  1986年   24篇
  1985年   20篇
  1984年   22篇
  1983年   10篇
  1982年   9篇
  1980年   7篇
  1979年   7篇
  1978年   7篇
  1975年   7篇
  1973年   8篇
  1972年   7篇
  1969年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
INTRODUCTION: Clinical examination of suspected scaphoid fractures is sensitive, but not specific, and initial plain radiographs lack sensitivity. A variety of second-line imaging techniques have been proposed to improve immediate diagnosis and reduce overtreatment. Different sample populations and methods of reporting test performance have made side-by-side comparison difficult. The aim of this study is to describe the epidemiology of clinically suspected scaphoid fracture and determine the prevalence of true fracture. These data are used to compare second-line imaging techniques in our population. PATIENTS AND METHODS: 200 consecutive patients attending a trauma service with clinically suspected scaphoid fracture were followed through diagnosis to discharge. RESULTS: The prevalence of true fracture was 16% and was associated with male sex and injury playing sport. Magnetic resonance imaging has the best diagnostic performance, with the added benefit of soft tissue evaluation, but was the most expensive option. Ultrasound examination was least effective in detecting true fractures. CONCLUSIONS: Future studies should further evaluate the clinical and economic sequelae of overtreatment of suspected fractures. Clinicians should examine alternatives to "empirical" treatment without definite diagnosis based on their local facilities and patient demographics.  相似文献   
82.
The contribution of somatic cells to nonrodent male germ cell transplantation success has not been well established due to lack of cell type-specific markers to distinguish donor cells from host cells. In the present study, we first screened antibodies and a lectin to identify markers suitable for unequivocal distinction between germ cells and Sertoli cells in bovine testes compared with mouse testes. Anti-vimentin and the Dolichos biflorus agglutinin (DBA) lectin detected only bovine Sertoli cells and spermatogonia, respectively; anti-NONO and anti-GCNA1 detected only mouse Sertoli and germ cells, respectively. The outcome of transplanting bovine testis cells into nude mouse testes was then studied using these markers. Our results clearly showed that immature bovine Sertoli cells survive and colonize mouse testes at 2.5 months after transplantation and that tubular structures composed of donor Sertoli cells formed adjacent to murine tubules within the host mouse testis. Bovine germ cell colonization and survival in mouse testes after transplantation were confirmed, but this was restricted to areas of bovine Sertoli cell colonization. In addition, ectopic grafts of intact bovine testis tissue and cell aggregates from hanging drop cultures were placed under the back skin and testis capsule of nude mice. Bovine Sertoli cells in ectopic grafts and aggregates were able to form tubular structures, and some bovine germ cells were observed around 2 months after implantation. This study therefore identifies a practical strategy to assess the outcome of testicular cell transplantation using different antibodies and a lectin to distinguish bovine cells from mouse cells. It identifies an approach that can readily be adapted to study other nonrodent species.  相似文献   
83.
BACKGROUND: Antagonists of growth hormone-releasing hormone (GHRH) could extend the duration of response of androgen sensitive prostate cancers to androgen deprivation. METHODS: We investigated the effect of new GHRH antagonists MZ-J-7-118 and MZ-J-7-138 and luteinizing hormone-releasing hormone (LHRH) antagonist Cetrorelix or castration on androgen sensitive MDA-PCa-2b and LuCaP-35 prostate cancer models xenografted into nude mice. Animals bearing androgen-independent LuCaP-35V prostatic cancer model were also treated with MZ-J-7-118. RESULTS: Receptors for LHRH and GHRH were present in MDA-PCA-2b, LuCaP-35, and LuCaP-35V tumors. GHRH antagonists increased the inhibitory effect of surgical castration and LHRH antagonists on androgen sensitive MDA-PCa-2b and LuCaP-35 tumors. The time to relapse of androgen-dependent LuCaP-35 tumors was extended by GHRH antagonists. Growth of androgen-independent LuCaP-35V xenografts was also significantly inhibited by MZ-J-7-118. In MDA-PCa-2b tumors treatment with MZ-J-7-118 caused a significant decrease of VEGF and Cetrorelix or its combination with MZ-J-7-118 reduced EGF. The B(max) of EGF receptors was significantly reduced by Cetrorelix, MZ-J-7-118 and their combination. CONCLUSIONS: Our findings suggest that the use of a combination of antagonists of GHRH and LHRH could improve the therapy for androgen sensitive prostate cancer. Antagonists of GHRH could be also considered for treatment of androgen-independent prostate cancers.  相似文献   
84.
OBJECTIVE: To determine whether extended transthoracic esophagectomy for adenocarcinoma of the mid/distal esophagus improves long-term survival. BACKGROUND: A randomized trial was performed to compare surgical techniques. Complete 5-year survival data are now available. METHODS: A total of 220 patients with adenocarcinoma of the distal esophagus (type I) or gastric cardia involving the distal esophagus (type II) were randomly assigned to limited transhiatal esophagectomy or to extended transthoracic esophagectomy with en bloc lymphadenectomy. Patients with peroperatively irresectable/incurable cancer were excluded from this analysis (n = 15). A total of 95 patients underwent transhiatal esophagectomy and 110 patients underwent transthoracic esophagectomy. RESULTS: After transhiatal and transthoracic resection, 5-year survival was 34% and 36%, respectively (P = 0.71, per protocol analysis). In a subgroup analysis, based on the location of the primary tumor according to the resection specimen, no overall survival benefit for either surgical approach was seen in 115 patients with a type II tumor (P = 0.81). In 90 patients with a type I tumor, a survival benefit of 14% was seen with the transthoracic approach (51% vs. 37%, P = 0.33). There was evidence that the treatment effect differed depending on the number of positive lymph nodes in the resection specimen (test for interaction P = 0.06). In patients (n = 55) without positive nodes locoregional disease-free survival after transhiatal esophagectomy was comparable to that after transthoracic esophagectomy (86% and 89%, respectively). The same was true for patients (n = 46) with more than 8 positive nodes (0% in both groups). Patients (n = 104) with 1 to 8 positive lymph nodes in the resection specimen showed a 5-year locoregional disease-free survival advantage if operated via the transthoracic route (23% vs. 64%, P = 0.02). CONCLUSION: There is no significant overall survival benefit for either approach. However, compared with limited transhiatal resection extended transthoracic esophagectomy for type I esophageal adenocarcinoma shows an ongoing trend towards better 5-year survival. Moreover, patients with a limited number of positive lymph nodes in the resection specimen seem to benefit from an extended transthoracic esophagectomy.  相似文献   
85.

Background/Purpose

The purpose of this paper was to examine the effect of prenatal counseling in the Advanced Fetal Care Center (AFCC) on the well-being of parents of infants with congenital diaphragmatic hernia (CDH).

Methods

From 2008 through 2012, 26 mothers and fathers of surgically repaired CDH patients who received prenatal counseling at our institution, and 15 who received no prenatal counseling, each completed the Short-Form 36 version 1 (SF-36v1) at the appropriate time points: prenatal, two weeks, and six months post-surgery.

Results

Parents in both groups did not differ by demographic characteristics. Patients who received prenatal counseling had significantly longer ventilatory time and length of stay (LOS) in the ICU and in the hospital compared to those who did not receive prenatal counseling (all P < .01). Mothers and fathers had similar SF-36v1 mental and physical component summary (MCS, PCS) post-surgery scores when compared by counseling status. Prenatal MCS scores for mothers and fathers (47 vs. 41; P = .24) were similar to those at six months post-surgery (47 vs. 47; P = .90).

Conclusions

When hospital LOS was controlled between groups stratified by AFCC counseling status, MCS scores were comparable prenatally and were sustained at six months post-surgery for both parents. These findings may reflect the support services parents received beginning in the prenatal period.  相似文献   
86.
In order to improve the treatment of children born with long‐gap esophageal atresia, a porcine model was developed for studying esophageal regrowth using a bridging graft composed of a silicone stented Biodesign mesh. The aim of the study was to investigate how leakage and contact between the native muscle and Biodesign mesh affected the early healing response. Resection of 3 cm of intrathoracic esophagus was performed in 10 newly weaned piglets. They were fed through a gastrostomy 8–10 days prior to sacrifice. In order to achieve nonleaking anastomoses, the silicone stent and suturing technique had to be adjusted between the first four and second six piglets. The technical adjustment decreased leakage. A nonleaking anastomosis could not be achieved when the native muscle layers were sewn less central on the bridging graft compared with the mucosa. If there was leakage, the inflammatory response increased, with islets of perivascular T‐lymphocytes and infiltration of macrophages in the native muscle layers. In the bridging area, new vessels were seen in the submucosa in 9 of 10 piglets between 4 and 10 days after surgery. Smooth muscle cells also appeared to move from the cut muscle edges of both the muscularis mucosa and the lamina muscularis and were seen as a layer of several cells under newly formed mucosa. Double staining of the basal membrane of the ingrowing vessels and the pericytes showed that the basal membrane was thinner over some of the pericytes, but there was no accumulation of immature‐looking cells in the submucosa of the bridging area. In this porcine model, where esophageal regrowth was studied by using a bridging graft composed of a silicone stented Biodesign mesh, we can conclude that leakage increased the inflammatory response in early healing. Ingrowth of new vessels was seen in the bridging area and movement of smooth muscle cells was found under newly formed mucosa.  相似文献   
87.
BackgroundOpen Ladd's procedure is the gold standard for the correction of intestinal malrotation and laparoscopic approach remains controversial. This study aimed to evaluate our experience in laparoscopic management of malrotation.MethodsSingle center retrospective study including patients who underwent a laparoscopic assessment of intestinal malrotation with correction if appropriate between 2007 and 2017.ResultsSixty-five patients (median age 7 months) had a laparoscopic assessment with and without correction of malrotation. Forty-five (69%) were symptomatic, including 16 (25%) with a midgut volvulus. The procedure was completed laparoscopically in 55 (86%) patients in 110 min (30–190). Conversions happened more frequently at the beginning of the experience. With a follow-up of 12.5 months (8 days–5.3 years), morbidity rate was 15% and 4 (6%) patients underwent a redo surgery, all in the first 5 months after surgery, compared with 3/53 (6%) in a contemporaneous group undergoing open Ladd's.ConclusionThis is the largest series reported so far of the laparoscopic management of malrotation. Laparoscopic Ladd's procedure is reliable but still exposes to open conversion which may be in part owing to a learning curve. A low conversion threshold is important in cases with volvulus. The redo rate is similar to that of the open procedure.Level of evidenceLevel III retrospective comparative treatment study.  相似文献   
88.
αv integrins play an important role in myofibroblast differentiation   总被引:1,自引:0,他引:1  
Transforming growth factor-beta1 is a potent mediator of the differentiation of fibroblasts into myofibroblasts, which is characterized by the appearance of the cytoskeletal protein alpha-smooth muscle actin. The aim of this study was to investigate the role of integrin extracellular matrix receptors in transforming growth factor-beta1-induced myofibroblast differentiation. We show that blockade of the alphav and/or beta1 integrins prevents the transforming growth factor-beta1-induced myofibroblast differentiation, seen by the increased expression of alpha-smooth muscle actin and enhanced collagen gel contraction in three human fibroblast cell lines (from the mouth, skin, and kidney). Further, blockade of alphav specific integrins alphavbeta5 and alphavbeta3 suppressed myofibroblast differentiation in fibroblasts from the mouth and skin; however, in the kidney cells, the prevention of differentiation was seen only with blockade of alphavbeta5 integrin but not alphavbeta3. A possible reason for this result may be different degrees of responsiveness to transforming growth factor-beta1 treatment seen from different anatomical origins of the cell lines. These data indicate a novel role for alphav integrins in the differentiation of human fibroblasts from the mouth, skin, and kidney into myofibroblasts and suggest that there is a common differentiation pathway.  相似文献   
89.
We used cultured adult mouse retinae as a model system to follow and quantify the retraction of dendrites using diolistic labelling of retinal ganglion cells (RGCs) following explantation. Cell death was monitored in parallel by nuclear staining as ‘labelling’ with RGC and apoptotic markers was inconsistent and exceedingly difficult to quantify reliably. Nuclear staining allowed us to delineate a lengthy time window during which dendrite retraction can be monitored in the absence of RGC death. The addition of brain‐derived neurotrophic factor (BDNF) produced a marked reduction in dendritic degeneration, even when application was delayed for 3 days after retinal explantation. These results suggest that the delayed addition of trophic factors may be functionally beneficial before the loss of cell bodies in the course of conditions such as glaucoma.  相似文献   
90.
We present two cases of recurrent progressive multifocal leukoencephalopathy (PML) in patients with long standing virally suppressed human immunodeficiency virus (HIV) and normal CD4+ T cell count who were taking stable regimens of highly active antiretroviral therapy (HAART). This has significant implications for other patients with a past history of PML, not just those with HIV but also those on medications such as natalizumab or fumarates.  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