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   10088篇
  免费   416篇
  国内免费   40篇
耳鼻咽喉   202篇
儿科学   807篇
妇产科学   500篇
基础医学   1013篇
口腔科学   227篇
临床医学   822篇
内科学   1904篇
皮肤病学   546篇
神经病学   404篇
特种医学   207篇
外科学   1486篇
综合类   335篇
一般理论   2篇
预防医学   1015篇
眼科学   263篇
药学   519篇
  1篇
中国医学   13篇
肿瘤学   278篇
  2021年   51篇
  2018年   56篇
  2017年   66篇
  2016年   68篇
  2015年   87篇
  2014年   103篇
  2013年   161篇
  2012年   187篇
  2011年   201篇
  2010年   171篇
  2009年   188篇
  2008年   171篇
  2007年   177篇
  2006年   201篇
  2005年   146篇
  2004年   95篇
  2003年   72篇
  2002年   109篇
  2001年   98篇
  2000年   85篇
  1999年   107篇
  1998年   177篇
  1997年   200篇
  1996年   228篇
  1995年   183篇
  1994年   181篇
  1993年   176篇
  1992年   158篇
  1991年   144篇
  1990年   143篇
  1989年   137篇
  1988年   119篇
  1987年   137篇
  1986年   118篇
  1985年   90篇
  1984年   90篇
  1983年   84篇
  1982年   73篇
  1981年   72篇
  1980年   55篇
  1979年   58篇
  1977年   62篇
  1959年   343篇
  1958年   762篇
  1957年   870篇
  1956年   776篇
  1955年   804篇
  1954年   782篇
  1949年   186篇
  1948年   126篇
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
51.
52.
We report the results and one-year follow-up of 20 elderly patients (age range 70-82 years) with severe rheumatic mitral stenosis treated by mitral balloon valvuloplasty (MBV). All 20 were breathless at rest despite treatment with diuretics and digoxin. At cardiac catheterization, successful dilatation was achieved in 17 patients: mean transvalvular mitral gradient fell by 45%, mean cardiac output rose by 24% and mean valve area increased by 76%. There was no procedure-related mortality. At one month, 15 patients had experienced an improvement in symptoms of at least one New York Heart Association class and, at one year, ten had maintained this improvement. Three patients proceeded to mitral valve replacement because of a suboptimal symptomatic result. Mitral balloon valvuloplasty can be successfully performed with significant symptomatic benefit in frail elderly patients unfit for surgery and may also be offered to other selected elderly patients as an alternative to surgical treatment.  相似文献   
53.
Background: Interleukin-6 is a pleiotropic cytokine with a wide range of physiological activities. It plays an important role in the immuno-neuro-humoral axis during stress and surgery.
Methods: Serum interleukin-6 in parturients was measured on hospital admission, immediately after birth and 12 and 24 hours later. All parturients had uncomplicated pregnancies, and delivered vaginally without (n=31) or with (n=20) epidural analgesia, or underwent Caesarean section under epidural (n=20) or general (n=10) anaesthesia.
Results: Serum interleukin-6 assayed immediately following Caesarean section was low, but peaked 12 hours later, irrespective of the anaesthetic technique or other foetomaternal characteristics. Patients who delivered vaginally showed the highest interleukin-6 levels immediately after delivery. These were positively correlated with serum interleukin-6 on admission and duration of labour. Serum interleukin-6 was significantly higher in parturients who had epidural analgesia, and was significantly lower in those receiving intravaginal prostaglandins compared to those without prostaglandins.
Conclusion: The interleukin-6 response after Caesarean section can be explained by a generalized acute phase response to surgery, with no anaesthetic, maternal or neonatal interference. The rapid increase in peripartum serum interleukin-6 levels after vaginal delivery reflects, in part, cervical ripening or labour, their physiological triggers and psychological or physical stress. Regional anaesthesia, duration of labour and exogenous prostaglandin administration can modulate the peripartum interleukin-6 response and subsequently the physiological effects of this cytokine.  相似文献   
54.
Office-based intraocular surgery has been carried out for three years and over 1400 procedures have been performed. There have been no systemic complications or infections. The establishment of an office-based facility is a complex venture. Apart from medicolegal, ethical and financial considerations there are regulations relating to structural requirements, sterilisation of instruments, air-conditioning, electrical hazards and other technical matters. Office-based surgery is convenient for both the patient and the surgeon. The patient remains calm and relaxed from the time of initial counselling to the end of postoperative convalescence. We have borrowed systems used in the United States for management of ambulatory surgical patients, in particular the counselling techniques. This, in our opinion, has been a significant factor for calm relaxed surgery. Patient acceptance and preference for ambulatory surgery will ensure that it is here to stay. A case can be made out for an economic and ethical obligation for this form of surgery to be implemented on a more widespread basis. It is not, however, the universal solution to ocular surgery. There are still specific indications and contraindications, in terms of both the doctor and the patient. At a time when government involvement is being felt more and more in the practice of medicine, any proven alternative method of health care delivery, provided entirely by the private sector, must be worthy of serious consideration.  相似文献   
55.
Objective: To study the relationship between transaldolase activity, protein expression and testosterone synthesis in Leydig cells of pubertal mice. Methods: Leydig cells were cultured for 2 hours and 8 hours, to the Stimulation Group, hCG was added and to the Controls, only the vehicle. The testosterone concentration was then determined by enzyme-linked immunoadsordent assay (ELISA) and the transaldolase activity and protein expression by Western blot. Results: (1) Both the testosterone concentration and the transaldolase activity in both Stimulation Groups were significantly higher than those in the corresponding Controls (2 h: p<0.05-0.01; 8 h: P<0.001); (2) The ratios of the A isoform, the B isoform and the total transaldolase protein to β-actin between the Stimulation and Control Groups did not differ signifi-cantly. Conclusion: hCG stimulates the transaldolase activity as well as the testosterone synthesis in the Leydig cells of pubertal mice, indicating a positive relationship between them.  相似文献   
56.
Scintigraphic visualization of intrathecal liposome biodistribution   总被引:1,自引:0,他引:1  
Background: Liposomes containing local anaesthetics have been administered intrathecally and in the epidural space. Poor attention has been given to the pharmacokinetics of liposomes as drug carriers. Therefore, we observed the biodistribution of liposomes after intrathecal injection in rats by scintigraphic imaging during 24 h.
Methods: We administered 99Tc-labeled multilamellar (MLV) and small unilamellar vesicles (SUV) of defined size and volume dispersities into the cerebrospinal fluid at the lumbar level. Those vesicles were free of contamination by radiolabeled colloids as visualized by light and electron microscopy and of neurotoxic products from phosphatidylcholine hydrolysis and peroxidation, both during the preparation process and after 24 h incubation in cerebrospinal fluid at 37°C in vitro.
Results: SUV immediately diffused from the lumbar site of injection to the head and were cleared between 1 and 24 h after injection. MLV were cleared more slowly from the spinal space and appeared in the head region 1 h after injection where they accumulated up to 24 h. These differences were explained in terms of vesicle sizes and volumes. SUV with 0.05 μm diameters were rapidly absorbed into the blood through the arachnoid granulations. In contrast, particles larger than the upper size limit of the arachnoid granulations permeability (±8 μm) could accumulate in the head with a slow elimination rate.
Conclusion: This difference in clearance from the intrathecal space outlines the importance of defining the size of the liposomes, the distribution of a tracer or a drug inside the liposomal preparation, the chemical stability and the absence of toxic degradation products of liposome formulations before clinical use.  相似文献   
57.
The records of 28 patients who underwent free jejunal graft reconstruction after resection for cancer involving the pharynx were analysed. Seven patients had a T3 carcinoma, 15 patients T4 and six patients recurrence after laryngectomy. Ten patients had received radiotherapy in the past. Post-operatively, 15 patients (54%) had complications and two patients (7%) died. No significant difference was observed in the complication rate between the group that received radiotherapy in the past and those who did not. Nineteen patients received post-operative radiotherapy. Nine patients had no radiotherapy on the basis of complete resection or because of serious complications. For the whole group the 2-year recurrence free period and survival were 42% and 51% respectively. The postoperative radiotherapy group had a significantly better survival (73%) and recurrence free period (63%) than the group without post-operative radiotherapy (0%). Thus, post-operative radiotherapy seems indicated irrespective of resection margins.  相似文献   
58.
59.
We report on the mechanisms, the environmental changes and patient compliance with regard to conventional and new dust and mite avoidance measures to prevent allergic symptoms caused by mite allergens, taking into account both allergen contamination and the developmental success of pyroglyphid Acari. Twenty patients with persisting rhinitic complaints were selected and matched. Although the patients had performed some conventional dust and mite avoidance measures (patient compliance was 90%), the dwellings proved to be a stimulus for mite development. Moisture problems due to faulty construction and excessive moisture production were common. Since humidity conditions could not be changed at short notice, the 20 homes were subjected to the new variants of mite allergen avoidance based on intensive cleaning without (control) and with an acaricide incorporated (acaricidal cleaner [Acarosan]). After the carrying out of conventional avoidance measures, these patients still had allergic symptoms, and dust from only 23 to 52% of their textile objects was under the proposed guanine (mite faeces indicator) risk level. Only the acaricidal cleaner was able to decrease the allergenic mite load (and the burden of the patients) significantly in this 12 month period. With respect to mite-extermination, acaricidal cleaning was 88% better than intensive cleaning. Reduction of guanine was 38% better in the Acarosan treatment group. Clinical results have been reported elsewhere. A significant difference in favour of the acaricidal cleaning was seen in both subjective (as regards symptoms) and in objective data (total IgE). Another 50 patients were questioned. About 90% were willing to spend two weekends (70%), or at the most one weekend (20%) per year sanitizing the dwelling by cleaning it with the whole family. The authors of this report consider acaricidal cleaning to be a significant improvement in the management of mite-allergic diseases, such as rhinitis. Compared with the replacement of home textiles, this treatment is less expensive and more effective. Patient compliance is acceptable, but depends on acceptance by physicians and the initial motivation and consequent burden on the patient.  相似文献   
60.
Extrapulmonary tuberculosis. A review.   总被引:2,自引:0,他引:2  
The increase in cases of tuberculosis that has occurred with the increasing number of individuals infected with the human immunodeficiency virus (HIV) has focused attention on the problems in diagnosing and treating tuberculosis. While it is primarily considered a pulmonary disease, tuberculosis has the potential to infect almost every organ system via lymphohematogenous dissemination during the initial pulmonary infection. Since 1984 the incidence of extrapulmonary tuberculosis has increased at an even faster rate than that of pulmonary tuberculosis. Extrapulmonary tuberculosis is considered a diagnostic criterion in the case definition of the acquired immunodeficiency syndrome. Immunocompromised individuals, such as patients with HIV, are at increased risk for extrapulmonary tuberculosis. The clinical manifestations are often nonspecific and insidious, and diagnosis may be delayed for years. Cases of miliary and meningeal tuberculosis are an exception, and they often constitute medical emergencies. Tuberculosis skin tests should be performed on all individuals suspected of having tuberculosis, but a negative test result does not exclude the diagnosis. Chest roentgenograms will often show signs of old or active pulmonary tuberculosis. Microscopic examination and culture of infected body fluids and/or tissue are necessary for definitive diagnosis. Treatment is with standard antituberculous medications. Short-course therapy (6 or 9 months) is probably adequate in most patients with extrapulmonary tuberculosis, but patients with human immunodeficiency viral infection need longer treatment. Extrapulmonary tuberculosis is a persistent problem in the United States and will become more prevalent as the number of patients with HIV increases. A high index of suspicion is needed to diagnose and treat extrapulmonary tuberculosis in a timely and health-preserving manner.  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