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   202759篇
  免费   4434篇
  国内免费   472篇
耳鼻咽喉   2813篇
儿科学   7639篇
妇产科学   6039篇
基础医学   26254篇
口腔科学   6145篇
临床医学   16367篇
内科学   36374篇
皮肤病学   4574篇
神经病学   12517篇
特种医学   10863篇
外国民族医学   97篇
外科学   30336篇
综合类   1123篇
一般理论   7篇
预防医学   16910篇
眼科学   4417篇
药学   14112篇
  2篇
中国医学   145篇
肿瘤学   10931篇
  2018年   3721篇
  2017年   4023篇
  2016年   3386篇
  2015年   4992篇
  2014年   4502篇
  2013年   3787篇
  2012年   10220篇
  2011年   5248篇
  2010年   2605篇
  2009年   4282篇
  2008年   2603篇
  2007年   3314篇
  2006年   3562篇
  2005年   11649篇
  2004年   13064篇
  2003年   8632篇
  2002年   3844篇
  2001年   4400篇
  2000年   1749篇
  1999年   5927篇
  1998年   620篇
  1996年   432篇
  1992年   6910篇
  1991年   7143篇
  1990年   7366篇
  1989年   6972篇
  1988年   6517篇
  1987年   6265篇
  1986年   5993篇
  1985年   5288篇
  1984年   3635篇
  1983年   2957篇
  1982年   1054篇
  1981年   805篇
  1980年   877篇
  1979年   3866篇
  1978年   2402篇
  1977年   1819篇
  1976年   1591篇
  1975年   2508篇
  1974年   3118篇
  1973年   2753篇
  1972年   2768篇
  1971年   2752篇
  1970年   2561篇
  1969年   2477篇
  1968年   2256篇
  1967年   2178篇
  1966年   1903篇
  1965年   1131篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
941.
Hepatic encephalopathy is ameliorated by drugs acting on the central GABAA-benzodiazepine receptor complex. To investigate whether these effects are specific for hepatic encephalopathy or just reflect a nonspecific arousal reaction, various benzodiazepine antagonists like flumazenil or with inverse agonistic properties (Ro 15-4513, Ro 15-3505) were studied in uremic encephalopathy in rats after bilateral ureteral ligation (n = 20) and compared with hepatic encephalopathy caused by thioacetamide-induced acute liver failure (n = 33). As soon as the animals developed clear signs of metabolic encephalopathy, their motor activity was recorded in an animal activity meter for 10 min. Furthermore, a composite score was calculated by grading various behavioral signs from 0 = absent to 3 = apparently normal. Rats were then injected with coded preparations of Ro 15-4513 (0.5, 2.5 and 5 mg/kg body wt intraperitoneally), flumazenil (2.5, 10, 25 and 40 mg/kg), Ro 15-3505 (10 mg/kg) or vehicle, and the measurements were repeated. The code was broken after the completion of the study. Pretreatment motor activity was decreased both in hepatic and uremic encephalopathy (20.7 +/- 6.4 [S.E.M.] and 41.3 +/- 37.1 movements/10 min). In hepatic encephalopathy motor activity and the composite score were improved both by 5 mg/kg Ro 15-4513 (by 293%, p less than 0.05) and by 10 mg/kg Ro 15-3505 (by 509%, p greater than 0.01), whereas vehicle and flumazenil had no effects. In uremic encephalopathy neither drug was effective in improving the neurobehavioral status.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
942.
Factorial experimental design was used to study the protective effects of Zn and Cu on cadmium-metallothionein(CdMT)-induced nephrotoxicity in male Wistar rats. In the factorial design two levels of Zn (0 and 25 mg/kg body weight), two levels of Cu (0 and 12.5 mg/kg), and two levels of CdMT (0.1 and 0.4 mg of Cd/kg) were used as varied factors. The factorial design was complemented with a center point with all three variables at an intermediate setting, i.e., Zn at 12.5 mg/kg, Cu at 6.25 mg/kg, and CdMT at 0.25 mg Cd/kg. Each of the nine combinations of settings was administered to one of nine groups with six rats in each. Zn and Cu were injected sc 24 hr prior to the injection of CdMT. The concentrations of protein and Ca in urine and Ca in renal cortex were used as effects. The relationship between the experimental design settings and the effects were modeled with multiple regression. The multiple regression analysis revealed that for the high dose of CdMT (i) the enhanced values of protein in urine caused by CdMT injection could be more efficiently reduced by Zn than by Cu, and (ii) excessive Ca in urine and renal cortex could be more efficiently reduced by Cu than by Zn. No significant synergism or antagonism between Cu and Zn was found. These models can be used to estimate the dose levels of Zn and Cu which will reduce the toxic effects of CdMT. The treatment of 20.4 mg/kg Zn, for example, will reduce the effects of 0.4 mg Cd/kg as CdMT on protein in urine, and 2.8 mg/kg Cu will reduce the Ca in urine to the levels of those caused by 0.25 mg Cd/kg (no Zn and Cu). Similarly, the effect of 0.4 mg Cd/kg on Ca level in renal cortex can be reduced to that of 0.28 mg Cd/kg as CdMT by 7.98 mg Cu/kg, which is three times as efficient as Zn. The obtained results might be of importance in understanding the mechanism of cadmium toxicity and the potential risk to the health of the population exposed to cadmium occupationally or environmentally.  相似文献   
943.
944.
The finding of large quantities of blood group A-active oligosaccharides in the feces of a blood group A breast-fed infant motivated a search for the origin of these compounds. Using an affinity chromatographic technique, the nature of A-active oligosaccharides in human milk is demonstrated. The amounts of A-active tetrasaccharide (A-tetra) and the Lewis b-active lacto-N-difucohexaose I (LND-I) varied between 19-375 mg/L for A-tetra and 14-710 mg/L for LND-I. Using the same technique, the amounts of A-tetra and LND-I in milk samples from five women of different blood groups were compared with those in the feces of their breast-fed infants. The A-tetra was present only in feces from infants of blood group A or AB mothers and the amount per 24 h corresponded roughly to that in a I-L portion of milk. One of the milk samples was also analyzed for the presence of larger A-active oligosaccharides (A-pentasaccharide, A-hexasaccharide, and A-heptasaccharide). Their amounts were much less as compared to the amounts present in feces. These results indicate that milk is a possible source for the smallest A-tetrasaccharide found in the feces of breast-fed infants, while the larger A-active oligosaccharides might be the result of an intestinal metabolic modification.  相似文献   
945.
In the last few years a group of verotoxinogenic E. coli bacteria has been defined as a causative agent of hemorrhagic colitis and haemolytic uremic syndrome. The corresponding toxins (verotoxins, Shiga-like-toxins) released from these bacteria play a key role in the pathogenesis and are responsible for the severity of the respective illness. Therefore, besides the clinical and other paraclinical investigations the detection of SLT-producing E. coli or of the corresponding toxins directly in the stool as early as possible has to be included into strategies for diagnostics and therapy. Moreover, it is necessary to avoid the release of huge amounts of toxins (e.g. by antibiotic therapy) and to take care for suitable measures to neutralize or eliminate the toxins. First isolations of enterohaemorrhagic E. coli (EHEC, VTEC) in stool samples from patients suffering from diarrhoeal diseases and HUS in the vicinity of Wernigerode demonstrate the necessity for further bacteriological and epidemiological investigations in order to evaluate frequency and importance of these EHEC bacteria in the pediatric praxis.  相似文献   
946.
Ocular motility in thalidomide embryopathy   总被引:1,自引:0,他引:1  
Twenty-one individuals, aged 28 to 29 years, with documented thalidomide embryopathy were examined in Sweden. The most noteworthy ophthalmologic finding was the high prevalence of incomitant horizontal strabismus, primarily of the Duane syndrome type. Less frequently seen were cases of both marked abduction and adduction limitation similar to a gaze paresis with no observable fissure changes, as well as a few cases of isolated abduction weakness or inferior oblique under-action. There were many examples of aberrant lacrimation, facial nerve palsy, and ear anomalies combined with horizontal incomitant forms of strabismus. Ear and facial nerve palsies are known to occur with ingestion of thalidomide early in the sensitive period (approximately days 21 to 26 after conception).  相似文献   
947.
The subjects in the study were 114 persons receiving a disability pension or referred for disability assessment. They were placed in two groups of 57 persons each, one with marked cervicobrachial syndrome and the other without. The latter group was chosen by the method of equivalent pairs with regard to sex and age. All subjects underwent a clinical examination and a standardized questionnaire was completed. The questionnaire pertained to the state of health, focussing on the amount and type of physical burdening at the workplace and on activities outside the workplace. Sixty-five percent of the subjects were aged from 51 to 60 years. A statistically significant difference was established between earlier occupation and cervicobrachial syndrome. Cervicobrachial syndrome was found in 31.6% of unskilled workers and 12.3% of the controls (P < 0.05). A forced body posture during work was recorded in 74% of the subjects with the syndrome and in 50% of the control subjects (P < 0.05). Repetitive movements at work were reported by a large number of subjects with cervicobrachial syndrome (71.9:49.1%; P < 0.05) who also claimed to strain the arms (84.2:61.4%; P < 0.05) and burden the cervical spine (68.5:40.4%; P < 0.05) during household activities to a significantly greater extent than the controls. A possible preventive approach to the occurrence and progression of cervicobrachial syndrome is discussed.  相似文献   
948.
The incidence of lymphoid malignancies (acute leukemias and myelomatosis excluded) during 1969-1987 in the County of Uppsala was calculated on the basis of the regional cancer register and local registers from the only oncological, hematological, dermatological and pathological departments in this well-defined geographical area. Of the 774 patients included, 639 had histopathological specimens available, all of which were re-examined. Seventy-nine patients were diagnosed on the basis of bone marrow investigations (greater than 70% re-examined, all had a low-grade non-Hodgkin's lymphoma = NHL) and 54 on fine-needle aspiration biopsies (not re-examined). Seventy-nine of the lymphoma diagnoses were based on autopsy specimens. The overall age standardized incidence was 16.2/100,000/year (NHL: 13.6, Hodgkin's disease = HD: 1.5) according to the Swedish 1970 census (according to world standard population: 10.2); male: 20.9 (12.9) and female: 12.4 (7.9). The annual change in trend was +3.0% +/- 2.6 (NHL: +3.6% +/- 2.4, HD: no change). The omission of the 54 'fine needle cases' led to an overall incidence of 15.0 (9.7) and an annual change in trend of +3.5% +/- 1.9. Among the histopathological specimens, an NHL was found in 524 patients and HD in 69. In 46 registered patients, the diagnosis malignant lymphoma was wrong. The diagnosis changed to NHL in 43 patients registered as HD.  相似文献   
949.
A prospectively recorded series of 107 patients with clinical neck node metastases from head and neck squamous cell carcinomas, treated in 1983-1988, and with initial local control, is evaluated. Eighty-eight patients received preoperative, and were operated 4-6 weeks after radiotherapy, and 19 received postoperative radiotherapy. Forty-four of the neck specimens in the preoperatively treated patients showed vital tumor tissue, 7 with positive and 37 with negative resection margins. Nine of the latter 37 patients died due to regional recurrence. Twenty-three of the preoperatively treated patients had no palpable residual tumor following radiotherapy, but histological examination showed vital tumor tissue in five, of whom two had N1 neck disease. The overall regional failure rate was 19%. Eleven patients (10%) died from local recurrence and 11 from distant metastases. Forty-one patients (38%) are alive without evidence of disease and three (3%) alive with disease (mean observation time 30 months). Combined treatment is recommended for all cases of neck node metastases.  相似文献   
950.
Follow-up examinations of 52 anginal patients who have received combined treatment involving plasma sorption indicate a good response in 77%, satisfactory in 11.5% and no response in 11.5% of the examinees. Exercise tolerance and performance increased by 34.3 and 52.1%, respectively. The scope of chemotherapy was related to the initial severity of the disease. Clinical remission after plasma sorption lasted 8.4 +/- 0.7 months.  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