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   26636篇
  免费   2788篇
  国内免费   36篇
耳鼻咽喉   326篇
儿科学   786篇
妇产科学   524篇
基础医学   3573篇
口腔科学   538篇
临床医学   3171篇
内科学   4622篇
皮肤病学   247篇
神经病学   2879篇
特种医学   851篇
外科学   4216篇
综合类   673篇
一般理论   5篇
预防医学   3011篇
眼科学   547篇
药学   1682篇
中国医学   12篇
肿瘤学   1797篇
  2021年   356篇
  2020年   218篇
  2019年   404篇
  2018年   492篇
  2017年   341篇
  2016年   346篇
  2015年   413篇
  2014年   577篇
  2013年   957篇
  2012年   1331篇
  2011年   1296篇
  2010年   696篇
  2009年   687篇
  2008年   1209篇
  2007年   1186篇
  2006年   1151篇
  2005年   1060篇
  2004年   1100篇
  2003年   1049篇
  2002年   907篇
  2001年   884篇
  2000年   920篇
  1999年   737篇
  1998年   314篇
  1997年   268篇
  1996年   289篇
  1995年   274篇
  1994年   242篇
  1993年   276篇
  1992年   638篇
  1991年   622篇
  1990年   591篇
  1989年   598篇
  1988年   561篇
  1987年   581篇
  1986年   513篇
  1985年   517篇
  1984年   393篇
  1983年   343篇
  1982年   234篇
  1981年   206篇
  1980年   201篇
  1979年   362篇
  1978年   205篇
  1977年   201篇
  1976年   224篇
  1975年   184篇
  1974年   241篇
  1973年   228篇
  1972年   188篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
41.
Genetic aspects of immotile cilia syndrome   总被引:3,自引:0,他引:3  
The genetics of the immotile cilia syndrome has been analyzed in a series of 46 affected individuals from 38 families. Both sexes were equally affected: there were 20 males and 26 females in this series. All patients had upper and lower respiratory disease with chronic sinusitis, otitis, and chronic cough from early childhood. Bronchiectasis was common in older children and adults. Situs inversus occurred randomly, affecting 11 males and 15 females. Biopsies of nasal and bronchial mucosa from these subjects have been investigated by electron microscopy and identified as having specific ultrastructural defects of respiratory tract cilia including deficiencies in outer dynein arms (19), inner dynein arms (3), both inner and outer dynein arms (15), radial spoke defect (5); and microtubular transposition anomaly (4). Segregation analysis of proband sibships was consistent with autosomal recessive inheritance. However, the different ultrastructural defects that underly the immotile cilia syndrome involve presumably different genetic determinants, and the different types have not been analyzed separately. Examination of paternal age and birth order gave no evidence of new autosomal dominant mutation in the series.  相似文献   
42.
Interaction with adenosine A1 receptors is a possible contributory mechanism to the anticonvulsant effects of carbamazepine (CBZ) and the dihydropyridine calcium antagonists. We measured the binding of [3H]cyclohexyladenosine to adenosine A1 receptors in mouse brain stem, cerebellum, and cortex after oral administration of nifedipine, nimodipine (NMD), and CBZ for 7 days and compared the results with binding in control mice. Equilibrium dissociation constant (Kd) and receptor numbers (Bmax) were calculated using Scatchard and saturation isotherm analyses. Mean Kds (SEM) in control brain stem, cerebellum, and cortex were 2.09 (0.31), 2.39 (0.2), and 3.12 (0.28) nM, respectively. Results of Bmax for the same areas were 188 (26), 280 (24), and 449 (54) fmol/mg protein. Nifedipine (p less than 0.005) and NMD (p less than 0.02) raised the Kd of A1 receptors only in the cerebellum, and CBZ increased cerebellar Bmax (p less than 0.05). These minor effects on A1 receptors in CF1 mice, when given in doses previously shown to have anticonvulsant properties in these animals, do not suggest that alteration in A1 receptor activity is an important mechanism for the anticonvulsant effects of these drugs.  相似文献   
43.
Cleft closure for the treatment of unhealed perineal sinus   总被引:2,自引:0,他引:2  
OBJECTIVE: Despite improvements in surgical practice, persistent perineal wound sinus is still a common complication after proctectomy. This study presents the success of a modified cleft closure technique in dealing with this problem. METHODS: From May 1997 patients with a persistent perineal sinus after surgery underwent a cleft closure - similar to that performed for patients with pilonidal sinus disease. RESULTS: Eight patients (6 male, 2 female) with an average age of 52 years underwent a cleft closure for a persistent perineal sinus after surgery. Four patients had undergone a proctocolectomy (ulcerative colitis), 2 an abdominoperineal excision of the rectum (adenocarcinoma) and 2 a proctectomy (1 Crohn's disease, 1 complication of diverticular disease). Symptoms had been present for an average of 41 months (range 5-152 months) and 3 patients had undergone other procedures attempted previously to deal with the problem. The first three patients had the procedure as an inpatient with an average stay of 4.7 days. The next 5 patients had the procedure as a day case (2 local anaesthetic, 3 general anaesthetic). Two patients developed a postoperative wound infection and all but one wound had healed completely by 8 weeks. In this patient the procedure was repeated to achieve healing. There was no other associated morbidity and no postoperative deaths. There have been no recurrences to date. CONCLUSION: Modified cleft closure for persistent perineal sinus is a simple procedure with low morbidity that can be performed under local anaesthetic in the day surgery unit.  相似文献   
44.
BACKGROUND: Pre-clinical and clinical studies suggest that transplantation of bone marrow-derived stem cells can improve global cardiac function. However, no quantitative assessment of regional systolic contraction and correlation with phenotype has been made. Therefore, we used our model of cryoinfarcted rabbit myocardium for intracardiac transplantation of a mixed population of bone marrow-derived cells and assessed both regional function and myogenic conversion of the cells. METHODS: Nineteen New Zealand white rabbits underwent cryoinjury of the left ventricle. Autologous bone marrow (BM) cells were expanded in vitro. After 2 weeks, either 1 x 10(8) mixed BM-derived progenitor cells (BM group, n = 11) or vehicle (control group, n = 8) were injected into the cryoinjured region. Regional systolic function was measured using micromanometry and sonomicrometry before and 4 weeks after cell injection; cell phenotype was evaluated histologically. RESULTS: All animals in the BM group significantly improved both systolic shortening (0.11 +/- 0.7 vs -0.05 +/- 0.05 mm in the control group, p < 0.05) and regional stroke work when compared with control (9.6 +/- 2.4 vs -1.2 +/- 1.2 mm . mm Hg, p < 0.003). In addition, the BM group had improved global diastolic function, as measured by minimum dP/dt and end-diastolic pressure. On histologic assessment, BM cells differentiated toward a myogenic phenotype. CONCLUSIONS: Transplanting a mixed population of marrow-derived cells that can adopt a myogenic phenotype improves regional contractility and diastolic relaxation after myocardial infarction.  相似文献   
45.
46.
47.
The many uses of the U tube   总被引:2,自引:0,他引:2  
U tube placement was employed as an adjunct to complicated biliary procedures in 14 patients. We found the transhepatic tubes to be useful for stenting biliary anastomoses, maintaining biliary drainage, delivering localized irradiation, and acting as permanent external conduits. The tubes remained in placed an average of 15 months and as long as 40 months. The frequency of cholangitis was minimized by frequent tube exchange. The U-shaped configuration makes tube exchange easy and inexpensive to perform.  相似文献   
48.
49.
The emergence of a near-haploid clone of cells in blast phase chronic myelogenous leukemia is an unusual event. We report such a case and review eight other cases described in the English literature. The significance of the substantial loss of genetic material is discussed as is the phenotypic and genotypic heterogeneity observed in this group of patients.  相似文献   
50.
The goal of the present study is to develop a technique for laparoscopic aortobifemoral bypass.Piglets weighing between 60 and 78 kg were anesthetized with halothane. The lateral retroperitoneal approach was preferred to the more familiar anterior transperitoneal approach and was successfully completed in 19 piglets. The piglets were placed in the right lateral decubitus position. The first port (2 cm) was inserted halfway between the tip of the 12th rib and the iliac crest. Four other trocars were placed in the retroperitoneum after balloon inflation had allowed creation of a space which permitted visualization of the aorta from the left renal artery down to the aorto-iliac junction. After evacuation of the retropneumoperitoneum, the cavity was maintained using an abdominal lift device and a retractor.Using this approach, we performed four aortobifemoral bypasses (end-to-end aortic anastomosis) after conventional intravenous heparinization (100 IU/kg) in less than 4 h. Blood loss did not exceed 250 ml and the hematocrit remained stable. Postmortem evaluation of the grafts revealed they were positioned as in a conventional bypass, their limbs having followed in the created retroperitoneal tunnels along the path of the native arteries. No mortality occurred before sacrifice of the animals. We believe that this first performed series of totally retroperitoneal laparoscopic aortobifemoral bypasses in the porcine model is useful in preparation for human application due to the anatomical similarities in the periaortic region.  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