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   3122篇
  免费   778篇
  国内免费   17篇
耳鼻咽喉   86篇
儿科学   114篇
妇产科学   53篇
基础医学   63篇
口腔科学   10篇
临床医学   1094篇
内科学   805篇
皮肤病学   131篇
神经病学   267篇
特种医学   99篇
外科学   585篇
综合类   31篇
一般理论   1篇
预防医学   136篇
眼科学   95篇
药学   63篇
中国医学   2篇
肿瘤学   282篇
  2024年   16篇
  2023年   142篇
  2022年   48篇
  2021年   128篇
  2020年   206篇
  2019年   73篇
  2018年   223篇
  2017年   169篇
  2016年   210篇
  2015年   178篇
  2014年   274篇
  2013年   310篇
  2012年   121篇
  2011年   93篇
  2010年   212篇
  2009年   273篇
  2008年   127篇
  2007年   97篇
  2006年   120篇
  2005年   91篇
  2004年   56篇
  2003年   44篇
  2002年   51篇
  2001年   73篇
  2000年   53篇
  1999年   62篇
  1998年   54篇
  1997年   61篇
  1996年   55篇
  1995年   48篇
  1994年   26篇
  1993年   16篇
  1992年   21篇
  1991年   24篇
  1990年   15篇
  1989年   15篇
  1988年   11篇
  1987年   4篇
  1986年   13篇
  1985年   17篇
  1984年   13篇
  1983年   8篇
  1982年   4篇
  1978年   7篇
  1975年   6篇
  1974年   3篇
  1958年   3篇
  1955年   6篇
  1954年   4篇
  1949年   6篇
排序方式: 共有3917条查询结果,搜索用时 15 毫秒
31.
Background: No published studies have compared the effectiveness of several treatments proposed to reduce cat allergenicity. Cat washing studies demonstrating efficacy involved very small sample sizes or infrequent washings. Allerpet-C (Allerpet, Inc., New York, N.Y.), a widely advertised topical spray, and acepromazine, a tranquilizer advocated as efficacious in subsedating doses, have never been scientifically studied. Objective: We compared the effects of cat washing, Allerpet-C spray, and acepromazine with that of no treatment on the shedding of the primary cat allergen, Felis domesticus I by cats. Methods: In a blinded, comparative, controlled study, we measured the amounts of Fel d I shed during an 8-week treatment period with a sample of 24 female mongrel cats randomly assigned to four groups; one group received weekly distilled water washings, one received weekly Allerpet-C spray applications, one received daily oral acepromazine, and one had no treatment (control). Thirty-minute, twice-weekly air samples were collected from each cat with a laminated plastic–acrylic chamber and air sampler. Results: One-sample, two-sided t tests comparing baseline to final-week measurements revealed no significant change in Fel d I within each group (mean change ±SD: washing; 487.6 ± 1896.4 mU per 30 minutes, p = 0.63; Allerpet-C spray, 429.2 ± 871.6 mU per 30 minutes, p = 0.46 acepromazine; −620.6 ± 1031.2, p = 0.52 per 30 minutes). Furthermore, analysis of covariance revealed no significant change in Fel d I levels between groups (p = 0.72). Conclusions: Our data do not show significant reductions in Fel d I shedding as a result of any of these treatments. Therefore we cannot recommend them to patients allergic to cats. (J ALLERGY CLIN IMMUNOL 1995;95:1164-71.)  相似文献   
32.
33.
Prospective trials demonstrate that sentinel node (SN) biopsy after neo-adjuvant chemotherapy (NACT) has a significant false-negative rate (FNR) when only 1 or 2 SNs are removed. It is unknown whether this increased FNR correlates with an elevated risk of recurrence. Tumor Registry data at an NCI-Designated Comprehensive Cancer Center were reviewed from 2004 to 2018 for patients having a negative SN biopsy after NACT. Among 190 patients with histologically negative nodes after NACT having 1 (n = 42), 2 (n = 46), and ≥3 (n = 102) SNs, axillary recurrences occurred in 7.14%, 0%, and 1.96% (p = 0.09), breast recurrences occurred in 2.38%, 6.52%, and 0.98% (p = 0.12), and distance recurrences occurred in 16.67%, 8.70%, and 7.84% (p = 0.27), respectively. Time to first recurrence did not differ by SN count (p = 0.41). After adjustment for age, race, clinical stage, and receptor status, there were no differences in the rates of axillary (p = 0.26), breast (p = 0.44), or distance recurrence (p = 0.24) by numbers of SNs harvested. Median follow-up was 46.8 months. Despite higher post-NACT FNRs reported in randomized trials for patients having <3 sentinel nodes, recurrence rates were not significantly different for 1 versus 2 versus ≥3 SNs. This suggests that patients having 1 or 2 post-NACT SNs identified may not necessitate axillary dissection.  相似文献   
34.
35.
The purpose of this study was to characterize presenting imaging findings in women younger than 40 diagnosed with invasive breast cancer in the context of pathology and clinical course. Retrospective chart and imaging reviews were performed in patients under 40 diagnosed with breast cancer between July 1, 2004, and December 31, 2013. Patient demographic, imaging, pathology, and clinical data were collected. Overall and recurrence-free survival were estimated using the Kaplan-Meier method. Univariate Cox proportional hazards models were performed to identify factors associated with recurrence-free survival. Our study cohort consisted of 110 patients with invasive mammary carcinoma. One hundred one (91.8%) presented with a palpable mass. The mean size of all lesions on imaging was 3.5 cm ± 2.9 cm. Malignant calcifications were present in 54 (49.1%) cases. Imaging demonstrated multifocal or multicentric disease in 45 (40.9%) cases. Seventy four (67.3%) cancers were high grade. Luminal genomic subtypes were the most common (n = 61, 55.5%). At presentation, 4 (3.6%) patients had bilateral malignancy and 8 (7.3%) patients had distant metastatic disease. Ninety seven (88.2%) underwent neoadjuvant chemotherapy and 67 (60.9%) underwent radiation therapy. Seventy five (68.2%) of the patients underwent mastectomy. The restricted mean time to recurrence was 9.01 years (standard error 3.162 months). ER positivity was associated with compromised recurrence-free survival. The overall survival rate was 0.962 at 10 years. Young patients diagnosed with breast cancer typically present with advanced breast imaging findings and undergo aggressive treatment. Recurrence often occurs >5 years from diagnosis, and ER positive subtypes are at increased risk for recurrence.  相似文献   
36.
Summary Ivermectin levels were measured in breastmilk and plasma of 4 healthy mothers after an oral 150 g/kg dose. Mean ± S.D. plasma and milk values were 37.9±0.54 and 14.13±0.43 (ng/ml) respectively. Steady-state ivermectin levels in milk were low. Our results suggest that exclusion of lactating mothers from mass chemotherapy with ivermectin may be unnecessary.  相似文献   
37.
Objective: Our purpose was to determine whether primary and preventive care is practiced by a university obstetrician-gynecologist group practice.Study design: A retrospective chart review spanning 2 years of four academic physicians' private practices was performed. A total of 335 patients were reviewed with 739 patient encounters and 1032 patient problems identified. The definition of a primary care physician according to The American College of Obstetricians and Gynecologists was used to standardize data collection and evaluation.Results: Obstetric complaints accounted for 27.7% of all visits, whereas 65.4% were for gynecologic problems. Almost 7% of all complaints were neither obstetric nor gynecologic, and of those 74.6% were primary care problems completely managed by the obstetrician-gynecologist. Only 19.7% of these were referred for management. More than 89% of all encounters () involved some element of primary care.Conclusion: This study provides evidence that the majority of health care provided by the obstetrician-gynecologists is primary care.  相似文献   
38.
The radiographic findings of a 15-year-old Brazilian male with diagnosis of multiple myeloma are described. He presented with claudication and recent onset of tender painful swelling of the right mid leg. Radiographs showed wide spread soap bubble lesions of the skull, long bones, spine, pelvis, ribs, shoulders, and clavicles. The diagnosis was confirmed by the presence of a plasmacytoma on tissue biopsy (femur), serum IgG gammopathy and Bence-Jones proteinuria.Supported by grants (CA-20180 and CA-21765) from the National Cancer Institute and the American Lebanese Syrian Associated Charities (ALSAC)  相似文献   
39.
OBJECTIVES: Our purpose was to determine (1) whether a fetal acoustic stimulation test results in more palpable fetal movement compared with a mock test (control) and (2) whether palpated fetal movements after a fetal acoustic stimulation test are accompanied by a reactive nonstress test.STUDY DESIGN: In a randomized controlled trial we studied women seen in the labor and delivery suite for various indications. Women were excluded for multiple gestation, <31 weeks' gestational age, treatment with magnesium sulfate or narcotics, or ruptured membranes. Informed consent was obtained from eligible women, who were then randomized to a test or control group. We placed an acoustic stimulator on the abdomen of each woman, but only the test group was stimulated. We assessed fetal movement by a grading system: 0 = no fetal movement felt by patient or tester, 1 = fetal movement felt by patient only, 2 = fetal movement felt by tester, 3 = visual movement seen by tester. A positive fetal acoustic stimulation test result was defined as one with any fetal movement felt or seen by the tester (grades 2 or 3). We then performed a nonstress test. We compared rates of a positive fetal acoustic stimulation test in the test and control groups with the χ2 test. A p value <0.05 was considered significant.RESULTS: We randomized 297 women to the test group and 280 women to the control (mock test) group. Of women tested with the fetal acoustic stimulation test, 81% had fetal movement by palpation or visualization (grades 2 or 3) compared with 19% of the control group (p < 0.0001, odds ratio 19.29, 95% confidence interval 12.42 to 30.07). Of the test group, 283 (95%) had a reactive nonstress test and 14 (5%) had nonreactive tests; the control group had 267 (95%) reactive and 13 (5%) nonreactive nonstress tests. Of 242 patients in the test group with a positive fetal acoustic stimulation test, 236 (98%) had a reactive nonstress test. Of those in the test group with fewer than three contractions per 10 minutes, 164 (89%) had a positive fetal acoustic stimulation test. Of these, 162 (99%) had a reactive nonstress test.CONCLUSION: The fetal acoustic stimulation test evokes significantly more palpated or visualized fetal movement than in controls. Palpated or visualized fetal movement after acoustic stimulation was almost always accompanied by a reactive nonstress test. (Am J Obstet Gynecol 1997;176:1386-8.)  相似文献   
40.
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