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   22314篇
  免费   1306篇
  国内免费   63篇
耳鼻咽喉   203篇
儿科学   676篇
妇产科学   425篇
基础医学   2986篇
口腔科学   734篇
临床医学   1550篇
内科学   5735篇
皮肤病学   559篇
神经病学   1850篇
特种医学   610篇
外科学   3087篇
综合类   130篇
一般理论   9篇
预防医学   1710篇
眼科学   673篇
药学   1117篇
中国医学   104篇
肿瘤学   1525篇
  2023年   171篇
  2022年   312篇
  2021年   741篇
  2020年   416篇
  2019年   612篇
  2018年   756篇
  2017年   483篇
  2016年   480篇
  2015年   634篇
  2014年   774篇
  2013年   1043篇
  2012年   1664篇
  2011年   1759篇
  2010年   956篇
  2009年   896篇
  2008年   1521篇
  2007年   1538篇
  2006年   1508篇
  2005年   1323篇
  2004年   1159篇
  2003年   1140篇
  2002年   1050篇
  2001年   274篇
  2000年   241篇
  1999年   265篇
  1998年   168篇
  1997年   150篇
  1996年   135篇
  1995年   121篇
  1994年   116篇
  1993年   96篇
  1992年   87篇
  1991年   88篇
  1990年   82篇
  1989年   69篇
  1988年   69篇
  1987年   70篇
  1986年   55篇
  1985年   54篇
  1984年   59篇
  1983年   45篇
  1982年   41篇
  1981年   54篇
  1980年   28篇
  1979年   43篇
  1978年   37篇
  1977年   35篇
  1976年   39篇
  1974年   23篇
  1973年   25篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
The Childrens Cancer Study Group has assessed serum follicle-stimulating hormone (FSH), luteinizing hormone (LH), and pubertal development in 97 long-term female survivors of childhood acute lymphoblastic leukemia (ALL). All patients received identical induction and maintenance therapy with either 18 or 24 Gy of radiation therapy (RT) to one of the following fields: cranial, craniospinal, or craniospinal plus 12 Gy abdominal RT including the ovaries. Thirty-six percent (35 patients) were found to have above normal levels of FSH and/or LH. The percentages of elevated values for RT fields were 93% for craniospinal plus abdominal RT, 49% for craniospinal RT, and 9% for cranial RT (P less than .001). A dose-response relationship was observed between 18 Gy and 24 Gy in females receiving only craniospinal RT (P = .01). Craniospinal plus abdominal RT and abnormal FSH/LH levels were significantly associated with lack of pubertal development and delayed onset of menses. Duration of maintenance chemotherapy was not associated with abnormal gonadotropin levels or the development of secondary sexual characteristics. Additional follow-up of this cohort is needed to establish the ultimate pubertal development and fertility of these patients.  相似文献   
22.
In order to avoid gentamicin toxicity trough serum concentrations when drug monitoring is not available, a correction factor for serum creatinine was calculated and evaluated. In a first group of 35 patients under aminoglycoside treatment with variable serum creatinine (SCr) values, the regression plot of SCr concentrations versus half-life (T1/2) values was established: log T1/2 = log 2.28 + 1.45 log SCr, r = 0.90, p less than 0.01. A second group of 18 patients was treated with doses of 1.0 mg/kg of gentamicin. Dose intervals equivalent to 3 T1/2 were daily adjusted. The T1/2 was calculated from SCr according to the relationship established for the patients of the first group. All the patients studied maintained trough levels within the therapeutic range.  相似文献   
23.
The standard treatment for patients with advanced ovarian cancer (AOC) has been cyclophosphamide and cisplatin (CP). Recently, the results of a large randomized comparative trial demonstrated that the combination of paclitaxel and cisplatin (TP) provided a progression-free survival benefit of 5 months. In this study, a cost–utility analysis was performed from a Canadian health care system perspective to estimate the incremental cost-effectiveness of the TP combination. Twelve AOC patients who received treatment with TP were matched for age and disease stage on a 1-to-2 basis with a CP control. Total hospital resource consumption was then collected for all patients. Treatment preferences were estimated from a cohort of 20 patients and 40 healthy female volunteers using the time trade-off technique. The outcomes were then generated through a decision-analytic model. First-line treatment costs with TP were approximately fourfold greater on a per-cycle basis than the CP alternative (Can$1911 vs Can$459). When progression-free survival benefit and patient treatment preferences were incorporated into the analysis, the results of the decision model revealed an incremental cost between Can$12,000 and Can$24,000 per quality-adjusted progression-free year with the TP protocol. Even though the TP combination has a considerably higher drug acquisition cost, the results of the current analysis suggest that this new chemotherapy regimen does provide patients with substantial quality-adjusted progression-free survival benefit at a reasonable cost to the Canadian health care system.  相似文献   
24.
25.
An important aspect of preventive medicine is to identify subjects at risk as soon as possible, so preventive strategies can be introduced at early ages. The justification for this strategy is twofold: firstly, the assumption that children maintain a particular high value of a risk factor for disease throughout life; and secondly, the assumption that lowering the level of the risk factor in early life will have a greater impact on the disease than will risk factor changes in later life. In epidemiology the analysis of such factors over time is referred to as tracking. Tracking analysis has been applied to risk factors for cardiovascular diseases (CVD) in pediatric years. The aims of this study were: I) to analyze the stability of biological risk factors [high blood pressure (BP), high percentage of fat mass (%FM) and high total cholesterol (TC)] and lifestyle risk factors [low physical activity index (PAI)] in isolation; and II) to analyze the stability of zero, one, two or three biological risk factors. There were two evaluations in 692 children and adolescents (325 boys and 367 girls), aged between 8 and 15 years. The quartiles, adjusted for age and gender, were the criterion used to identify subjects with biological risk factors (fourth quartile) and with lifestyle risk factors (first quartile) for CVD. The stability was calculated through the relative frequency of subjects who maintained or changed quartile between the two evaluations. There is stability for biological risk factors as well as for behavioral and/or lifestyle risk factors. However, the highest stability is seen in biological risk factors.  相似文献   
26.
We have isolated an H-2 deficient cell line (LR.4) from the T-cell lymphoma L5178Y which grew without restrictions in the peritoneal cavity of different inbred strains of mice. The use of polyclonal anti-H-2 antiserum and complement indicated that LR.4 cells did not express class I determinants on the cell membrane. Southern blots of genomic DNA of LR.4 cells showed that B2m genes were severely damaged and that class I H-2 genes were extensively methylated. Consequently, LR.4 cells failed to transcribe mRNAs for both B2m and class I H-2 genes. On the other hand, specific immunity to LR.4 was demonstrated in C57BL/6J mice since, in subsequent challenges with either LR.4 or EL4.4, LR.4 did not grow, whereas EL4.4 grew and killed the mice. In C57BL/6J mice, rejection of LR.4 was accompanied by the production of cytotoxic antibodies. The immune response induced in C57BL/6J mice was determined by non-H-2 antigenic determinants in LR.4 cells.  相似文献   
27.
28.
Eighteen patients with chronic constipation were diagnosed as having paradoxical puborectalis contraction (PPC) as the cause for their constipation. The diagnosis of PPC was made after office evaluation, colonic transit study, manometry, cinedefecography, and electromyography (EMG). These 18 patients had a mean duration of symptoms of 26.9 years; none of these patients had unassisted bowel movements. Fourteen patients had a mean of 4.6 laxative-induced bowel evacuations per week, and 11 patients had a mean of 4.4 enema-induced bowel evacuations per week. Patients underwent a mean of 8.9 one-hour EMG-based biofeedback sessions. At a mean follow-up of 9.1 (range, 0.5–12) months, these 18 patients had a mean of 7.3 unassisted bowel actions per week ( P <0.0001). In addition, persistent laxative use was reported by only two patients, and, in both cases, this was once a week or less ( P <0.001). Similarly, enema use was reported by only three patients, one once weekly and the other two thrice weekly ( P <0.002). No biofeedback-related complications were identified. EMG-based biofeedback is a valuable technique associated with an 89 percent success rate in the treatment of PPC.Read at the meeting of The American Society of Colon and Rectal Surgeons, Boston, Massachusetts, May 12 to 17, 1991.  相似文献   
29.
INTRODUCTION: It is still controversial whether subjects with white-coat hypertension (WCHT) exhibit higher cardiovascular risk compared to normotensive subjects (NT). In subjects with WCHT it is not known whether the abnormal blood pressure (BP) reaction in the office also occurs at other times of day, particularly on arising and immediately after waking, i.e. the times at which the majority of cardiovascular events are reported to occur. OBJECTIVE AND METHODS: To evaluate with 24h ambulatory BP measurement the values of morning BP surge, BP on arising and BP variability in subjects with WCHT in comparison with age-, gender- and weight-matched normotensives (BP) and untreated sustained hypertensives (BP). RESULTS: Groups of BP, WCHT and BP were matched for age, gender and body weight: BP: n=69, age 49 +/- 7 years, 54 % female, BMI 26 +/- 1, casual BP 126/79 +/- 5/4 mmHg, daytime BP 124/80 +/- 6/6 mmHg; WCHT: n=74, age 52 +/- 8 years, 57% female, BMI 26 +/- 2, casual BP 152/95 +/- 7/7 mmHg, daytime BP 126/80 +/- 5/6 mmHg; HT: n=79, age 53 +/- 7 years, 56% female, BMI 27 +/- 2, casual BP 154/97 +/- 9/8 mmHg, daytime BP 143/89 +/- 12/10 mmHg. Of the three groups, subjects with WCHT exhibited BP on arising (121/81 +/- 13/8 mmHg) similar to that of NTs (120/80 +/- 13/9 mmHg, NS), both significantly lower than that of HTs (137/92 +/- 17/10 mmHg, p < 0.01), suggesting the absence of an alerting BP reaction in WCHT at that time. By contrast, subjects with WCHT showed higher values of systolic morning BP surge vs. NTs (25 +/- 10 vs. 22 +/- 11 mmHg, p < 0.05), both lower than that observed in hypertensives (33 +/- 11 mmHg, p < 0.01 vs. NT and WCHT) and greater daytime variability (systolic BP standard variation), i.e. 12 2 vs. 10 +/- 2 mmHg, p < 0.05, both lower than that observed in hypertensives (14 +/- 3 mmHg, p < 0.01 vs. NT and WCHT). CONCLUSIONS: Although subjects with WCHT did not show any alerting blood pressure reaction on arising, morning BP surge and BP variability were greater in these subjects than in control normotensives, although lower than sustained hypertensives. Although this is still speculative, we cannot exclude the possibility that even a slight increase in morning BP surge might in the long term constitute an additional load on the circulation that could increase cardiovascular risk in subjects with WCHT compared to matched normotensives.  相似文献   
30.
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