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   32306篇
  免费   2996篇
  国内免费   125篇
耳鼻咽喉   328篇
儿科学   1061篇
妇产科学   629篇
基础医学   4548篇
口腔科学   410篇
临床医学   3882篇
内科学   7046篇
皮肤病学   761篇
神经病学   3437篇
特种医学   1035篇
外国民族医学   1篇
外科学   4683篇
综合类   239篇
一般理论   29篇
预防医学   2749篇
眼科学   393篇
药学   1898篇
中国医学   65篇
肿瘤学   2233篇
  2023年   113篇
  2022年   234篇
  2021年   552篇
  2020年   478篇
  2019年   862篇
  2018年   969篇
  2017年   803篇
  2016年   809篇
  2015年   1007篇
  2014年   1222篇
  2013年   1709篇
  2012年   1998篇
  2011年   2201篇
  2010年   1409篇
  2009年   1301篇
  2008年   1914篇
  2007年   1986篇
  2006年   1930篇
  2005年   1991篇
  2004年   1917篇
  2003年   1937篇
  2002年   1994篇
  2001年   317篇
  2000年   256篇
  1999年   327篇
  1998年   394篇
  1997年   367篇
  1996年   292篇
  1995年   330篇
  1994年   271篇
  1993年   258篇
  1992年   183篇
  1991年   195篇
  1990年   170篇
  1989年   143篇
  1988年   156篇
  1987年   162篇
  1986年   145篇
  1985年   142篇
  1984年   154篇
  1983年   125篇
  1982年   176篇
  1981年   171篇
  1980年   155篇
  1979年   97篇
  1978年   103篇
  1977年   93篇
  1976年   74篇
  1975年   66篇
  1972年   72篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
51.
Specific immunotherapy   总被引:6,自引:5,他引:1  
Jean  Bousquet  M.D. François-B.  Michel  M.D. 《Allergy》1988,43(S8):16-22
  相似文献   
52.
We investigated the natural history of atopic dermatitis (AD) in a population-based birth cohort and assessed whether children at risk of visible eczema at 5 years of age can be identified from total immunoglobulin E (IgE) levels measured at 8, 12 and 18 months. AD data collected included a whole body examination for visible eczema at 49 months (4 years) and 61 months (5 years) of age and parent completed questionnaire data throughout their early lives. Children were divided into four groups based on their natural history of early AD: persistent (AD at 1, 6, 18, 30 and 42 months, n  = 34), intermittent early onset (before 18  months of age, n  = 495), intermittent late onset (18–42 months of age, n  = 273) and unaffected ( n  = 429). Visible eczema at 5 years of age was present in 12.2% (117/957) (95% confidence interval [CI] 10.1–14.3%) of the children. Levels of total IgE at 8, 12 and 18 months of age were associated with early onset of AD, but not with AD of later onset. For all four natural history groups, the geometric mean total IgE at 12 months was higher in those who subsequently had visible eczema than those who did not. However, the degree of overlap was such that total IgE at 12 months of age was a poor predictor of eczema at age five. A cutoff point of 78 kU/l had the highest positive predictive value for visible eczema at 5 years of age of 28.6%, with a sensitivity of 12% and specificity of 95%.  相似文献   
53.
Periosteal bone turnover is poorly understood. We documented intramembranous periosteal bone turnover in the femoral neck in intact nonhuman primates and an increase in osteoclast numbers at the periosteal surface in sex steroid-deficient animals. Our studies are the first to systematically document periosteal turnover at the femoral neck. INTRODUCTION: Bone size is an important determinant of bone strength, and cellular events at the periosteal surface could alter bone dimensions. We characterized periosteal cellular activity with dynamic histomorphometric studies of nonhuman primate femoral neck and shaft. MATERIALS AND METHODS: Femur specimens from 16 intact adult male and female nonhuman primates (Rhesus [Macaca mulatta, n = 9] and Japanese Macaque [Macaca fuscata, n = 7]) were analyzed. Animals were double-labeled with tetracycline, and necropsy was performed 2-7 days after the last dose. We characterized periosteal resorptive activity in an additional group of five intact and four castrate female animals. Multiple group comparisons in intact animals were performed by one-way ANOVA followed by a Fisher PLSD posthoc test. In gonadectomized animals, Fisher's exact test was used for dichotomous and Mann-Whitney U-test for continuous variables. RESULTS: Bone turnover in the periosteum of the femoral neck in intact animals was more rapid than at the femoral shaft but slower than in femoral neck cancellous bone. Similarly, in these intact animals, the eroded surface of cortical bone at the femoral neck periosteal surface was significantly greater than in the cancellous bone compartment (p < 0.0001) or on the femoral shaft (p < 0.0001). Gonadectomized female animals showed an increase in osteoclast number on the periosteal surface compared with intact controls (p < 0.01). CONCLUSIONS: We documented intramembranous periosteal bone turnover in the femoral neck by histomorphometric analyses. The tissue level bone formation rate was sufficient to add substantively to femoral neck size over time. Periosteal osteoclastic activity was not the result of the emergence of intracortical tunneling at the bone surface. Sex steroid deficiency produced an increase in osteoclast numbers at the periosteal surface. This is the first systematic documentation of periosteal turnover at the femoral neck.  相似文献   
54.
55.
The uptake of radiolabeled somatostatin analogs by tumor cells through receptor-mediated internalization is a critical process for the in vivo targeting of tumoral somatostatin receptors. In the present study, the somatostatin receptor internalization induced by a variety of somatostatin analogs was measured with new immunocytochemical methods that allow characterization of trafficking of the somatostatin receptor subtype 2 (sst2), somatostatin receptor subtype 3 (sst3), and somatostatin receptor subtype 5 (sst5) in vitro at the protein level. METHODS: Human embryonic kidney 293 (HEK293) cells expressing the sst2, sst3, or the sst5 were used in a morphologic immunocytochemical internalization assay using specific sst2, sst3 and sst5 antibodies to qualitatively and quantitatively determine the capability of somatostatin agonists or antagonists to induce somatostatin receptor internalization. In addition, the internalization properties of a selection of these agonists have been compared and quantified in sst2-expressing CHO-K1 cells using an ELISA. RESULTS: Agonists with a high sst2-binding affinity were able to induce sst2 internalization in the HEK293 and CHO-K1 cell lines. New sst2 agonists, such as Y-DOTA-TATE, Y-DOTA-NOC, Lu-DOTA-BOC-ATE (where DOTA is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid; TATE is [Tyr3, Thr8]-octreotide; NOC is [1-NaI3]-octreotide; and BOC-ATE is [BzThi3, Thr8]-octreotide), iodinated sugar-containing octreotide analogs, or BIM-23244 were considerably more potent in internalizing sst2 than was DTPA-octreotide (where DTPA is diethylenetriaminepentaacetic acid). Similarly, compounds with high sst3 affinity such as KE108 were able to induce sst3 internalization. In sst2- or sst3-expressing cell lines, agonist-induced receptor internalization was efficiently abolished by sst2- or sst3-selective antagonists, respectively. Antagonists alone had no effect on sst2 or sst3 internalization. We also showed that somatostatin-28 and somatostatin-14 can induce sst5 internalization. Unexpectedly, however, potent sst5 agonists such as KE108, BIM-23244, and L-817,818 were not able to induce sst5 internalization under the same conditions. CONCLUSION: Using sensitive and reproducible immunocytochemical methods, the ability of various somatostatin analogs to induce sst2, sst3, and sst5 internalization has been qualitatively and quantitatively determined. Whereas all agonists triggered sst2 and sst3 internalization, sst5 internalization was induced by natural somatostatin peptides but not by synthetic high-affinity sst5 agonists. Such assays will be of considerable help for the future characterization of ligands foreseen for nuclear medicine applications.  相似文献   
56.
OBJECTIVE: To compare the efficacy, safety, and duration of effect of four doses of botulinum toxin type A in the treatment of glabellar rhytids in females. DESIGN: Double-blind, randomized, parallel-group, dose-ranging trial followed by an open-label extension. SETTING: Private dermatologic clinic. SUBJECTS: Eighty female subjects with moderate to severe wrinkles at maximum frown entered the study. The first 40 subjects completing the double-blind phase entered the open-label extension. INTERVENTION: Random administration of 10, 20, 30, or 40 U botulinum toxin type A in divided doses. Open-label trial: 30 U botulinum toxin type A at the same sites in divided doses. MAIN OUTCOME MEASUREMENTS: Trained observer and subject assessments of wrinkle severity at maximum frown and repose using the Facial Wrinkle Scale (0 = none to 3 = severe), subject satisfaction, and adverse events. Follow-up monthly for up to 1 year postinjection. RESULTS: Relapse rates and responder rates revealed benefits lasting 3 to 6 months or longer. Objectively, 10 U of botulinum toxin type A was significantly less effective than 20, 30, or 40 U. The relapse rate at 4 months was significantly higher in the 10 U group (83%) versus 40, 30, or 20 U (28%, 30%, and 33%, respectively). Subject satisfaction was high in all groups. Duration of effect and response rates were sustained during the open-label extension. Adverse effects were mild and infrequent. CONCLUSION: Twenty to 40 U botulinum toxin type A doses were significantly more effective at reducing glabellar lines than 10 U. Most subjects experienced benefits for 3 to 4 months; some subjects demonstrated effect for up to 12 months.  相似文献   
57.
58.
The objective of this study was to evaluate the epidemiology, diagnosis, pathophysiology, and treatment of bone loss related to anorexia nervosa. Earlier onset and longer duration of anorexia nervosa are associated with more severe bone loss. Osteoporosis develops in 38 to 50% of cases. Bone mineral density measurement by dual-energy X-ray absorptiometry is useful for assessing bone mass, and bone marker assays provide information on bone turnover. Bone loss in anorexia nervosa is probably multifactoriel. Estrogen deficiency was long felt to be the major factor. However, in contrast to postmenopausal osteoporosis, bone loss associated with anorexia nervosa is related mainly to inadequate bone formation, with only a slight increase in bone resorption. This suggests a role for nutritional factors, such as disturbances in the growth hormone-somatomedin C axis (GH/IGF-I) related to malnutrition. The best treatment strategy for correcting bone mass in patients with anorexia nervosa is not agreed on. Resumption of menstrual cycles and weight gain seem necessary but not always sufficient. Studies found no benefits with estrogen therapy, but this was usually given as estrogen–progestin contraceptives. No vast studies evaluating hormone replacement therapy have been reported. Bone formation enhancers such as IGF-I seem to provide the best results, most notably when used in combination with estrogens. This suggests that complex treatment strategies combining bone formation enhancers and bone resorption inhibitors may deserve evaluation.  相似文献   
59.
Background: Intravenous infusion of lidocaine decreases postoperative pain and speeds the return of bowel function. The authors therefore tested the hypothesis that perioperative lidocaine infusion facilitates acute rehabilitation protocol in patients undergoing laparoscopic colectomy.

Methods: Forty patients scheduled to undergo laparoscopic colectomy were randomly allocated to receive intravenous lidocaine (bolus injection of 1.5 mg/kg lidocaine at induction of anesthesia, then a continuous infusion of 2 mg [middle dot] kg-1 [middle dot] h-1 intraoperatively and 1.33 mg [middle dot] kg-1 [middle dot] h-1 for 24 h postoperatively) or an equal volume of saline. All patients received similar intensive postoperative rehabilitation. Postoperative pain scores, opioid consumption, and fatigue scores were measured. Times to first flatus, defecation, and hospital discharge were recorded. Postoperative endocrine (cortisol and catecholamines) and metabolic (leukocytes, C-reactive protein, and glucose) responses were measured for 48 h. Data (presented as median [25-75% interquartile range], lidocaine vs. saline groups) were analyzed using Mann-Whitney tests. P < 0.05 was considered statistically significant.

Results: Patient demographics were similar in the two groups. Times to first flatus (17 [11-24] vs. 28 [25-33] h; P < 0.001), defecation (28 [24-37] vs. 51 [41-70] h; P = 0.001), and hospital discharge (2 [2-3] vs. 3 [3-4] days; P = 0.001) were significantly shorter in patients who received lidocaine. Lidocaine significantly reduced opioid consumption (8 [5-18] vs. 22 [14-36] mg; P = 0.005) and postoperative pain and fatigue scores. In contrast, endocrine and metabolic responses were similar in the two groups.  相似文献   

60.
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