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   133210篇
  免费   7598篇
  国内免费   768篇
耳鼻咽喉   1299篇
儿科学   4080篇
妇产科学   3131篇
基础医学   19257篇
口腔科学   5403篇
临床医学   11951篇
内科学   29960篇
皮肤病学   3516篇
神经病学   12799篇
特种医学   2944篇
外国民族医学   1篇
外科学   11643篇
综合类   502篇
一般理论   66篇
预防医学   13538篇
眼科学   2150篇
药学   9592篇
中国医学   545篇
肿瘤学   9199篇
  2024年   159篇
  2023年   1345篇
  2022年   2935篇
  2021年   4936篇
  2020年   3011篇
  2019年   4128篇
  2018年   4783篇
  2017年   3534篇
  2016年   3907篇
  2015年   4399篇
  2014年   5786篇
  2013年   7451篇
  2012年   11313篇
  2011年   11755篇
  2010年   6308篇
  2009年   5335篇
  2008年   9108篇
  2007年   9040篇
  2006年   8252篇
  2005年   7591篇
  2004年   6788篇
  2003年   5988篇
  2002年   5370篇
  2001年   626篇
  2000年   422篇
  1999年   661篇
  1998年   906篇
  1997年   740篇
  1996年   612篇
  1995年   502篇
  1994年   480篇
  1993年   392篇
  1992年   322篇
  1991年   214篇
  1990年   212篇
  1989年   194篇
  1988年   183篇
  1987年   153篇
  1986年   165篇
  1985年   119篇
  1984年   141篇
  1983年   140篇
  1982年   170篇
  1981年   122篇
  1980年   135篇
  1979年   75篇
  1978年   82篇
  1977年   72篇
  1976年   62篇
  1974年   55篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
The reproducibility of myocardial motion trajectories calculated from cine phase-contrast (PC) velocity data is reduced by artifacts due to the inconsistent motion of intracardiac blood. Spatial presaturation reduces these artifacts but requires a longer sequence TR, with a potentially negative effect on trajectory accuracy and reproducibility. We investigated the effect of spatial presaturation on trajectory reproducibility. A midventricular transaxial slice was imaged in five normal volunteers. The same slice was imaged three times each with sequences using spatial presaturation or not. Because the most serious artifacts originate in the heart chambers and propagate in the phase-encoded direction, myocardial regions that were in line with the heart chambers (in the phase-encode direction) had the highest artifact level in the scans without spatial presaturation. The reproducibility of trajectories for regions placed in these areas (the anterior wall, septum and posterior wall in the transaxial scans with phase encoding in the anterior-posterior direction) improved by a factor of two when presaturation was used (P < .001). In areas that were not in line with the heart chambers (eg, the anterior aspect of the lateral wall in the transaxial scans), the effect of presaturation was not significant. These results correlate well with the measured reduction in artifact level. The reproducibility of myocardial motion trajectories over large areas of the heart is improved to approximately 1 mm when presaturation is used. Therefore, use of presaturation is recommended for myocardial motion studies using cine PC velocity data.  相似文献   
82.
83.
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   
84.
Forty-seven cases with anorexia nervosa (including a total population group) and 47 sex-, age-, and school-matched comparison cases were subjected to chromosome analyses in a blind fashion. No major abnormalities were found in any of the cases. Sex chromatin was analysed in buccal smears from the girls. No differences between the anorexia nervosa and the comparison cases were found. It seems that chromosomal/sex chromatin analyses in anorexia nervosa are not warranted.  相似文献   
85.
We tested the ability of normal subjects to make changes in the conjugacy of their saccades. Subjects dichoptically viewed a grid the size of which was 10% larger in one eye. The grids were centred onto a flat screen at 57 cm or 1 m from the subject. Horizontal saccades immediately became larger in the eye viewing the larger grid. For some subjects this disconjugacy persisted even under subsequent monocular viewing. Such persistent changes occurred mainly in the field where the required disconjugacy was divergent for centrifugal saccades, convergent for centripetal saccades. Vertical saccades also developed compensatory disconjugacy; its amplitude was smaller but less variable. To explain these results we propose a fast associative learning mechanism that pairs peripheral disparity with saccades and is capable of producing saccade disconjugacy even in the absence of disparity. For horizontal saccades a secondary conditioning of monocular depth cues by the disparity would also be involved.  相似文献   
86.
BACKGROUND: When and whether early enteral nutrition (EN) benefits critically ill patients is debatable. This prospective clinical audit aimed to evaluate the feasibility of an early EN protocol and to identify factors that may hinder EN delivery in critically ill patients. METHODS: Thirty-six medical patients with severe respiratory failure under invasive ventilation and scheduled to receive early EN, with a length of ICU stay >72 hours, were included. As asserted by the Society of Critical Care Medicine, 8% of patients were priority 1, 72% priority 2, and 20% priority 3 for intensive therapeutic and vital support interventions. RESULTS: Overall, because of gastrointestinal complications, only 39% of the prescribed EN was administered; only 8 (22%) patients did tolerate EN within the first 48 hours after admission and did achieve their minimum nutritional requirements. The most frequent complication (78%) was high volume of gastric residuals followed by abdominal distention (61%), both associated with hemodynamic instability (HI). Gastrointestinal dysfunction was associated with high Acute Physiologic and Chronic Health Evaluation II score (p = .01), total calorie intake (p = .02), total carbohydrate intake (p = .02), HI (p = .03), malnutrition (p = .04), volume of IV saline (p = .04), and concurrent vasoactive drug administration (p = .05). CONCLUSIONS: This audit in extremely severe intensive care patients identified several factors that impair gastrointestinal function and preclude EN at any stage, namely early EN. Nutrition management must take into account concurrent therapies, given their potential interference with nutrition and organ function.  相似文献   
87.
88.
Zusammenfassung Anamnese und Diagnostik: Ein 75-jähriger Patient wies neben unspezifischen anamnestischen Symptomen (Appetitverlust, Merkfähigkeitsstörung und Muskelschwäche) klinisch diskrete Beinödeme, abgeschwächte Muskeleigenreflexe und eine deutliche Gedächtnisstörung auf. Aufgrund einer euvolämischen, laborchemisch hypoosmolaren Hypoatriämie und eines Urinnatriums im Normbereich wurde als Arbeitsdiagnose von einem Syndrom der inadäquaten ADH-Sekretion (SIADH) ausgegangen. Während sich weder in der Anamnese noch in den folgenden Untersuchungen eine dem SIADH zugrunde liegende Pathologie eruieren ließ, ergab sich in den weiteren Laboruntersuchungen der Befund einer ausgeprägten Hypothyreose. Die Hyponatriämie bei Hypothyreose spiegelt eine Komponente der renalen Funktionsstörung bei Schilddrüsenhormonmangel wider. Therapie und Verlauf: Nach Flüssigkeitsrestriktion und Hormonsubstitution erreichte der Patient schnell normale Natriumwerte und zeigte eine deutliche Besserung seiner kognitiven Fähigkeiten. Schlussfolgerung: Als Schlussfolgerung aus dieser Kasuistik wird Zurückhaltung bei der Diagnose eines SIADH empfohlen, bevor nicht eine sorgfältige Untersuchung des Nebennieren- und Schilddrüsenhormonstatus erfolgt ist. Abstract Case History and Diagnosis: A 75-year-old male patient presented with a history of anorexia, muscle weakness, and increasing memory loss. He had mild pedal edema and decreased deep tendon reflexes. As the laboratory tests showed hypoosmolar hyponatremia and urinary sodium within the normal range, a syndrome of inappropriate ADH secretion (SIADH) was presumed. While neither the medical history nor any of the diagnostic procedures revealed any underlying pathology explaining the SIADH, laboratory tests showed significant hypothyroidism. Hypothyroid states are associated with significant changes in renal function, one of which is hypoosmolar hyponatremia. Treatment and Course: Treatment included fluid restriction and hormone substitution and resulted in a quick correction of the hyponatremia and a clear improvement of the patient's cognitive function. Conclusion: It is concluded that the diagnosis of SIADH should only be made after thorough investigation of the adrenal and thyroid hormone status.  相似文献   
89.
Abstract: Red cell phospholipids (PLs) were assessed in 11 patients with essential thrombocythemia and 5 patients with polycythemia vera. Platelet and plasma PLs were also determined in 10 of these patients, and the results were compared with studies performed in 16 healthy volunteers. The amount of platelet PLs in patients was similar to controls (556 ± 90 nmol/109cells, versus 481 ± 91 nmol/109cells), as was the percentage of the main specimens of these compounds, including phosphatidylserine (11.1 ± 0.8%), which is relevant for platelet procoagulant activity. We did not find differences between red cell PLs of patients (300 ± 60 nmol/109cells), versus controls (289 ± 71 nmol/109cells), and the sphingomyelin/phosphatidylcholine ratio in these cells was the same in both groups (0.75 ± 0.1). Finally, we did not detect any alteration in the amount of plasma PLs specimens.  相似文献   
90.
ABSTRACT: A case study of the creation and implementation of a four-tier, integrated system of health care services in a sparsely populated, rural province in Argentina is described and discussed. Begun in 1970 in a diverse geographical area with a tradition of poor health status and inadequate health care resources, the provincial government set out to develop the human, physical and technological resources needed to provide a system of preventive and curative services appropriate to the health care needs of its residents. Innovative programs included training in management techniques, and epidemiological perspective of high risk, an emphasis on personnel development through a rural general medicine residency and an expanded nursing program as well as programs to attack infectious diseases, poor sanitation and dental problems were all developed in response to the distinctive features of the physical and social environment of the province. Improvements in traditional health indicators are reviewed and attributed to the program and administrative structures that were developed.  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