全文获取类型
收费全文 | 520716篇 |
免费 | 34613篇 |
国内免费 | 624篇 |
专业分类
耳鼻咽喉 | 7052篇 |
儿科学 | 17138篇 |
妇产科学 | 13727篇 |
基础医学 | 85853篇 |
口腔科学 | 14689篇 |
临床医学 | 44948篇 |
内科学 | 95524篇 |
皮肤病学 | 12389篇 |
神经病学 | 36692篇 |
特种医学 | 18677篇 |
外国民族医学 | 63篇 |
外科学 | 78324篇 |
综合类 | 8494篇 |
一般理论 | 120篇 |
预防医学 | 39601篇 |
眼科学 | 12306篇 |
药学 | 40889篇 |
中国医学 | 1036篇 |
肿瘤学 | 28431篇 |
出版年
2018年 | 5178篇 |
2016年 | 4260篇 |
2015年 | 4698篇 |
2014年 | 6334篇 |
2013年 | 9890篇 |
2012年 | 13266篇 |
2011年 | 14745篇 |
2010年 | 8617篇 |
2009年 | 8002篇 |
2008年 | 14059篇 |
2007年 | 15087篇 |
2006年 | 15338篇 |
2005年 | 14722篇 |
2004年 | 14382篇 |
2003年 | 13709篇 |
2002年 | 13581篇 |
2001年 | 24323篇 |
2000年 | 25371篇 |
1999年 | 20773篇 |
1998年 | 5488篇 |
1997年 | 4750篇 |
1996年 | 5089篇 |
1995年 | 4667篇 |
1994年 | 4350篇 |
1992年 | 15835篇 |
1991年 | 16413篇 |
1990年 | 16513篇 |
1989年 | 15885篇 |
1988年 | 14622篇 |
1987年 | 14471篇 |
1986年 | 13639篇 |
1985年 | 13020篇 |
1984年 | 9657篇 |
1983年 | 8273篇 |
1982年 | 4573篇 |
1981年 | 4242篇 |
1979年 | 9444篇 |
1978年 | 6870篇 |
1977年 | 5779篇 |
1976年 | 5615篇 |
1975年 | 6416篇 |
1974年 | 7652篇 |
1973年 | 7153篇 |
1972年 | 6982篇 |
1971年 | 6705篇 |
1970年 | 6190篇 |
1969年 | 5910篇 |
1968年 | 5578篇 |
1967年 | 5021篇 |
1966年 | 4459篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Oilseed rape and seasonal symptoms: epidemiological and environmental studies. 总被引:2,自引:1,他引:1 下载免费PDF全文
BACKGROUND--There is widespread concern that the cultivation of oilseed rape leads to seasonal epidemics of respiratory symptoms in populations living in the neighbourhood, and it has been suggested that the plant is a potent allergen. A study was therefore undertaken to determine the prevalence of seasonal symptoms in rural populations close to and far from areas of oilseed rape cultivation, and to measure the levels of allergen and other potentially harmful substances released by the crop. METHODS--Random samples of 1000 adults from the general practice populations of two villages surrounded by oilseed rape fields, and 1000 adults from one village far from such cultivation, were taken. The subjects completed a previously validated questionnaire on respiratory and other symptoms, including questions on symptom seasonality, occupation, and smoking habits. Pollen and fungal spore counts were made around fields of oilseed rape and in the villages. The chemicals released by oilseed rape were measured in the field. RESULTS--Overall, 86.8% of the subjects completed the questionnaires and the populations of the two samples were generally comparable. Spring and summer exacerbations of symptoms occurred equally in the two areas in approximately 25% of the population. There were small but significant excesses of cough, wheeze, and headaches in spring in the oilseed rape area (2.3% v 1.1%, 6.8% v 4.6%, and 4.8% v 2.8%, respectively), and cough, wheeze, and itchy skin were more prevalent in smokers. Counts of oilseed rape pollen were generally low except adjacent to fields, and counts of fungal spores were mostly higher in the rape than the non-rape areas. Oilseed rape was shown to give off terpenes and these were detected close to fields. CONCLUSIONS--While it is likely that a proportion of the spring symptoms occurring in people living in close proximity to oilseed rape is caused by the plant, the excess of such symptoms is small. This, together with the low levels of pollen in the area, suggests that allergy to oilseed rape pollen is uncommon. The general prevalence of seasonal symptoms in rural areas is of interest, and a proportion of these cases is likely to be caused by factors other than allergy. Release of chemicals by plants and natural rises in summer ozone levels may be contributors. 相似文献
982.
M Tanenbaum M D Gossman D J Bergin H I Friedman D Lett P Haines C D McCord 《Ophthalmic surgery》1992,23(6):418-425
We describe a tarsorrhaphy technique whereby an ipsilateral upper-eyelid tarsal pillar is sutured to a corresponding lower-eyelid recipient site. This technique allows maintenance of a narrowed interpalpebral fissure indefinitely, yet is easy to reverse without incurring lid-margin damage. Additionally, the procedure can be adjusted postoperatively to either narrow or widen the initial surgical result. We report our combined surgical experience in 35 consecutive procedures using this technique to treat eyes with exposure-related keratopathy of varied etiology, including facial nerve palsies, combined facial nerve palsy and trigeminal neuropathy with an anesthetic cornea, Graves' disease, congenital craniofacial anomalies, and severe keratitis sicca syndrome. The procedure was successful in improving exposure keratopathy symptoms in all 35 cases. Complications, reflecting the authors' learning curve with this new procedure, included intermarginal pyogenic granulomas, stretching of the tarsal pillar, minor lower-eyelid-margin eversion, and tarsal pillar dehiscence. 相似文献
983.
Purified murein from Thiobacillus neapolitanus was poorly digested by lysozyme. It's sensitivity to the enzyme greatly increased after N-acetylation. The murein was found to contain 30 to 35% glucosamine residues lacking N-acetyl groups. It also contained phosphomuramic acid. Further modifications included amidation of diaminopimelic acid in the peptide side chains and a low alanine content. None of these modifications were found in the murein of another sulphur bacterium, Thiobacillus versutus. 相似文献
984.
A L Usala I Wexler A Posch M K Gupta 《American journal of diseases of children (1960)》1992,146(9):1074-1077
OBJECTIVE--To determine the course of maternally derived elevations in thyrotropin-binding inhibitory immunoglobulins in a neonate. DESIGN--Case report. SETTING--University pediatric endocrinology clinic and endocrine immunology laboratory in Ohio. PARTICIPANTS--An infant with elevated thyrotropin levels but near-normal total thyroxine levels, and her mother. INTERVENTIONS--None. MEASUREMENTS/MAIN RESULTS--Thyroid hormone, thyrotropin, and thyrotropin-blocking immunoglobulin concentrations were serially measured in a woman and her infant, who was found to have elevated thyrotropin levels (234 mU/L) and borderline low thyroxine levels (95 nmol/L). As infant thyroxine concentrations remained normal (125 to 145 nmol/L), no thyroxine supplementation was given. Thyrotropin levels decreased concomitantly with thyrotropin-blocking inhibitory immunoglobulin levels, and normalized by day 56 of life. The apparent elimination half-life of thyrotropin-blocking immunoglobulins was 7.5 days. CONCLUSIONS--The observed parallel elimination kinetics suggest that the thyrotropin receptor antibody acts as a thyrotropin antagonist, resulting in compensatory thyrotropin elevations. The duration of such elevations may be predicted on the basis of such elimination. 相似文献
985.
986.
H I Abdalla 《British journal of hospital medicine》1992,48(1):28-33
Management of infertility is slow, time consuming and, paradoxically, costly. It needs to be streamlined so that diagnosis and management go hand in hand with proper division between primary physicians at district level and highly trained specialists at regional level. Incorporation of assisted conception techniques is the key to the success of such an approach. 相似文献
987.
J Béres T Tauszik M Horányi I Pazonyi J Szelényi Z Hollán G Flatz 《Orvosi hetilap》1992,133(30):1869-1873
In 1984 a late malaria endemic area, called Bodrogk?z was studied. This was a reexamination of the population genetic work performed by Walter, Nemeskéri. In six villages of Bodrogk?z 328 persons were tested for AB0, Rh blood groups, haptoglobins, haemoglobin concentration, haematocrit, erythrocyte amount, the MCV, the MCH and the G-6-PD were analyzed. The quantitative determination of HbF and HbA2, red cell osmotic resistance and thalassemia were measured as well. Thalassemia heterozygote carriers and an increased level of HbF were revealed. The frequency of G-6-PD deficiency was 0.39%. In Bodrogk?z the frequencies of AB0, Rh and haptoglobin types were similar in the present and all previous studies. The background of this similarity might be the genetic similarity between two following generations. On the basis of these facts, the Hb0 Arab and partially DNA work we suggested an alternative hypothesis that these mutant genes got into Bodrogk?z by the rather later migration than with ancient Hungarian people during the period of conquest of Hungary. 相似文献
988.
989.
The authors described a 7 weeks old cervical pregnant case, whome was administered 250 mg methotrexate in infusion to eliminate the throphoblastic tissue. 3 days later the HCG was negative in the urine. After the dilatation of cervix by laminaria, the collapsed amniotic sac came from the cervix with minimal hemorrhage. They suggest the method is suitable to prevent the serious complications of cervical pregnancy. 相似文献
990.
Human immunodeficiency virus type 1 (HIV-1) prototype, HIV1 LAV, and a Zairian virus HIV1 NDK, an isolate highly cytopathic for CD4+ lymphocytes, were used to infect eleven different CD4 negative non-lymphoid human cell lines. Eight of the lines were derived from carcinomas wherein human papillomavirus was thought to have been etiologic. All these cell lines lacked CD4 receptor and CD4 specific mRNA. After cocultivation with sensitive CEM cells, HIV-1 LAV was rescued from six infected cell lines and HIV-1 NDK from nine. Shedding of free virus into the culture medium was observed in three cell lines infected by HIV-1 NDK and in only one cell line infected by HIV-1 LAV. The infectibility of CD4 negative cell lines indicates that both HIV-1 strains were able to use a CD4 independent mechanism to infect the cells; however, HIV-1 NDK showed the higher efficiency of infection. This virus was also able to overcome the intracellular block of viral reproduction. These results suggest that a broader spectrum of cell types of non-lymphoid origin lacking the CD4 receptor can serve as a viral reservoir. In some cases they are direct producers of infectious HIV-1 particles. This suggests, that in addition to immunosuppressive mechanisms, HIV-1 could play a more direct role in induction of neoplastic changes. 相似文献