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   3402篇
  免费   336篇
  国内免费   7篇
耳鼻咽喉   59篇
儿科学   207篇
妇产科学   65篇
基础医学   449篇
口腔科学   109篇
临床医学   297篇
内科学   584篇
皮肤病学   26篇
神经病学   178篇
特种医学   208篇
外科学   434篇
综合类   64篇
一般理论   4篇
预防医学   475篇
眼科学   107篇
药学   229篇
中国医学   1篇
肿瘤学   249篇
  2021年   32篇
  2019年   37篇
  2018年   39篇
  2017年   35篇
  2016年   28篇
  2015年   35篇
  2014年   60篇
  2013年   107篇
  2012年   95篇
  2011年   114篇
  2010年   76篇
  2009年   62篇
  2008年   120篇
  2007年   128篇
  2006年   134篇
  2005年   124篇
  2004年   143篇
  2003年   140篇
  2002年   127篇
  2001年   122篇
  2000年   108篇
  1999年   94篇
  1998年   63篇
  1997年   63篇
  1996年   73篇
  1995年   61篇
  1994年   60篇
  1993年   50篇
  1992年   74篇
  1991年   69篇
  1990年   88篇
  1989年   87篇
  1988年   81篇
  1987年   63篇
  1986年   71篇
  1985年   74篇
  1984年   63篇
  1983年   62篇
  1982年   34篇
  1981年   36篇
  1980年   38篇
  1979年   60篇
  1978年   56篇
  1977年   37篇
  1976年   46篇
  1975年   27篇
  1974年   42篇
  1972年   31篇
  1970年   36篇
  1969年   28篇
排序方式: 共有3745条查询结果,搜索用时 15 毫秒
81.
PURPOSE: To describe the neurologic and neurosensory deficits in children with brain tumors (BTs), compare incidence of these deficits with that of a sibling control group, and evaluate the factors associated with the development of these deficits. PATIENTS AND METHODS: Detailed questionnaires were completed on 1,607 patients diagnosed between 1970 and 1986 with a primary CNS tumor. Neurosensory and neurologic dysfunctions were assessed and results compared with those of a sibling control group. Medical records on all patients were abstracted, including radiotherapy dose and volume. RESULTS: Seventeen percent of patients developed neurosensory impairment. Relative to the sibling comparison group, patients surviving BTs were at elevated risk for hearing impairments (relative risk [RR], 17.3; P = <.0001), legal blindness in one or both eyes (RR, 14.8; P = <.0001), cataracts (RR, 11.9; P = <.0001), and double vision (RR, 8.8; P = <.0001). Radiation exposure greater than 50 Gy to the posterior fossa was associated with a higher likelihood of developing any hearing impairment. Coordination and motor control problems were reported in 49% and 26%, respectively, of survivors. Children receiving at least 50 Gy to the frontal brain regions had a moderately elevated risk for motor problems (RR, 2.0; P <.05). Seizure disorders were reported in 25% of patients, including 6.5% who had a late first occurrence. Radiation dose of 30 Gy or more to any cortical segment of the brain was associated with a two-fold elevated risk for a late seizure disorder. CONCLUSION: Children surviving BTs are at significant risk for both early and late neurologic or neurosensory sequelae. These sequelae need to be prospectively monitored.  相似文献   
82.
OBJECTIVE: Because the survival rate has increased for extremely low birth weight neonates, many have raised the concern that the rate of developmental disability among survivors will also increase. To address this concern, we analyzed changes over time in survival and major neurosensory impairment in a sample of extremely low birth weight infants born between July 1, 1979, and June 30, 1994. METHODS: The study sample included 513 infants with birth weights of 501 to 800 g who were cared for in either of the two neonatal intensive care units that serve a 17-county region in northwest North Carolina and who were born to mothers residing in that region. At 1 year of age (corrected for gestation), survivors were examined by a pediatrician and were tested using the Bayley Scales of Infant Development. Major neurosensory impairment was defined as cerebral palsy, a Bayley Mental Developmental Index <68, or blindness. A total of 209/216 (97%) of survivors were examined at 1 year of age. Epoch of birth was defined as follows: epoch 1, July 1, 1979 to June 30, 1984; epoch 2, July 1, 1984 to June 30, 1989; and epoch 3, July 1, 1989 to June 30, 1994. RESULTS: Survival rates for epochs 1, 2, and 3 were, respectively, 24/120 (20%), 63/175 (36%), and 129/218 (59%). In contrast, the proportions with a major neurosensory impairment did not increase over time; rates for successive epochs were 6/24 (25%), 17/61 (28%), and 26/124 (21%). Rates of cerebral palsy were 3/24 (13%), 12/61 (20%), and 9/124 (7%); rates of delayed mental development were 4/24 (17%), 12/61 (20%), and 17/124 (14%); and rates of blindness were 2/24 (8%), 0/62, and 5/124 (4%), respectively. CONCLUSIONS: This analysis suggests that the increasing survival of extremely low birth weight neonates since the late 1970s has not resulted in an increased rate of major developmental problems identifiable at 1 year of age.  相似文献   
83.
Accepted 30 January 1997
OBJECTIVE—To evaluate the efficiency of the screening programme for congenital hypothyroidism in Scotland and to determine the outcome in the cohort of children with positive testing for thyroid stimulating hormone (TSH).
DESIGN—Establishment of comprehensive database for all Scottish infants with high TSH, detected on Guthrie screening.
SUBJECTS—344 infants born between August 1979 and December 1993 with TSH greater than 40 mU/l on initial Guthrie, or 15-40 mU/l on repeat Guthrie.
MAIN OUTCOME MEASURES—Ages at time of: (a) Guthrie collection, (b) notification of positive result by laboratory, and (c) start of treatment; audit of late diagnosis/missed cases; categorisation of positive cases into definite and probable congenital hypothyroidism, transient TSH elevation, and uncertain status; educational status of children with definite and probable congenital hypothyroidism.
RESULTS—344 positive cases were categorised as having definite (224) and probable (11) congenital hypothyroidism, transient TSH elevation (88), and status uncertain (21). The overall incidence of definite/probable congenital hypothyroidism was 1 in 4400 live births. For the definite/probable groups median age of Guthrie collection was consistently between 6 and 7 days from 1983 onwards but for the whole cohort was later than 10 days in 10.5%. Median age of notification fell from 14days in 1980 to 11 days in 1993. Median age of starting treatment ranged between 11 and 15 days from 1983 onwards. Treatment was delayed in four cases, three due to failed or late Guthrie card submission. Of 149 children with definite/probable congenital hypothyroidism who were of school age, educational status was ascertained in 139 (93%). Only two children (1.4%) were attending special school, one of whom was known to have mild hypothyroidism. Sixteen children (11.5%) were receiving extra help in mainstream education compared with 18% of control children in the Scottish very low birth weight study.
CONCLUSION—The current screening programme is working well, but efficiency could be increased by earlier and more reliable Guthrie collection. A substantial proportion of children picked up on the screening programme have a transient rise in TSH rather than true congenital hypothyroidism. The incidence of special education and learning support in Scottish children with congenital hypothyroidism appears to be no different to that of the general population.

  相似文献   
84.
OBJECTIVE: To assess the efficacy of a longer acting preparation of the gonadotrophin releasing hormone (GnRH) analogue goserelin (Zoladex LA, 10.8 mg) in 12 girls with central precocious or early puberty. METHODS: Two girls started treatment de novo; the remainder had been on suppressive treatment for a median duration of 1.5 (range, 0.2-5.6) years. Assessment comprising auxology, pubertal staging, and pelvic ultrasound examination was carried out at weeks 0, 4, 8, 10, and 12 (first cycle) and weeks 8, 10, and 12 (second cycle) to evaluate the required injection frequency. Thereafter, assessment was performed on the day of injection. Zoladex LA was given every 12 weeks unless pubertal progression occurred. RESULTS: Satisfactory control was achieved in eight patients using this regimen, and three patients required more frequent injections. One girl was removed from the study because of clinical progression and extreme mood swings. No serious adverse effects occurred. Mean height velocity during the study period was 4.5 cm/year (range, 3.1-6.6) compared with 6.5 cm/year (range, 3.8-9.6) before treatment in nine patients for whom data were available. CONCLUSIONS: Zoladex LA was effective in controlling precocious puberty in girls when given at intervals of 9-12 weeks and it is recommended that an initial assessment is made eight weeks after beginning treatment.  相似文献   
85.
The beta2 integrin (CD 18/CD 11 a, b, c) family of proteins mediate adherence of leukocytes to vascular endothelium and the associated ligand, intercellular adhesion molecule-1 (ICAM-1; CD 54), interacts with beta2 integrin proteins to allow transendothelial migration of leukocytes into sites of inflammation. The present study examines the function of these proteins in a murine model of acute cutaneous inflammation induced following topical application of 12-O- tetradecanoylphorbol-13-acetate (TPA) to the dorsal epidermis of SENCAR mice and in a model of skin multistage carcinogenesis. At 24 h following topical application of TPA to the dorsal epidermis of mice, dermal leukocytes expressed higher levels of beta2 integrin protein compared with the lower levels of beta2 integrin protein expression by peripheral blood leukocytes. ICAM-1 protein was localized to epidermal keratinocytes and vascular endothelium in TPA-treated skin and to proliferating papilloma cells. Intravenous (i.v.) injection of either 50 microg anti-beta2 integrin antibody alone or in combination with anti-ICAM-1 antibody significantly inhibited both TPA-stimulated neutrophil infiltration into the dermis (P < 0.001) and myeloperoxidase (MPO) activity (P < 0.03 anti-beta2 integrin antibody; P < 0.01 anti- beta2 integrin + ICAM-1 adhesion molecule antibodies), but had no effect on TPA-induced epidermal hyperplasia. In addition, injection of either anti-ICAM-1 adhesion molecule antibody alone (P < 0.004) or in combination with anti-beta2 integrin antibody (P < 0.001) significantly inhibited TPA-induced production of 7,8-dihydroxy-2'-deoxyguanosine (8- OHdG) immunoreactive proteins by epidermal keratinocytes. Beta2 integrin/ICAM-1 adhesion molecules work in concert to regulate migration, retention and functional activation of leukocytes within the dermis during TPA-induced skin inflammation and within stromal tissue of papillomas that form during multi-stage carcinogenesis. Agents that inhibit these receptor/ligand interactions may be useful in defining the roles of specific cell populations in cutaneous inflammation and multistage carcinogenesis and may also have potential as anti-promoting and anti-progression agents.   相似文献   
86.
McKeown-Eyssen (Cancer Epidemiol. Biomarkers Prevent., 3, 687-695, 1994) and Giovannucci (Cancer Causes Control, 6, 164-179, 1995), noting the striking similarity in lifestyle risk factors for colorectal cancer and insulin resistance, proposed that the hyperinsulinemia, glycemia and hypertriglyceridemia associated with insulin resistance promotes colon cancer. To compare the effect of diet on colon cancer promotion and insulin resistance in the F344 rat, we assessed the effect of fat, n-3 fatty acids and energy in pairwise comparisons on average size of aberrant crypt foci (ACF) and on glucose intolerance in the same animals in a single experiment. Diets high in fat and energy increased and diets with increased n-3 fatty acids and calorie restriction decreased both ACF growth and glucose intolerance compared with control diets. The measures of promotion of colon cancer and insulin resistance were strongly correlated (n = 98, r = 0.67, P < 0.001). In addition, both were highly correlated with daily energy intake (r = 0.62 and 0.66) and were also correlated with basal (post-prandial) insulin, glucose and triglycerides (r = 0.31-0.53, P < 0.01). We concluded that ACF growth and glucose intolerance are correlated for a wide range of diets and that increased circulating energy (glucose and triglycerides) may lead to both colon cancer promotion and insulin resistance.   相似文献   
87.
88.
89.
Objective We investigated whether available epidemiological and toxicological data suggest an increased risk of mesothelioma among workers exposed to synthetic vitreous fibers (SVF). Methods We conducted a systematic review of epidemiological studies on the risk of mesothelioma among workers exposed to SVF, and toxicological studies on SVF and mesothelioma. Results Seven cohort studies were conducted among workers employed in production of rock/slag wool, glass wool, or continuous glass filament in the United States, Canada, and Europe. Of the six deaths from mesothelioma identified in these studies, three had exposure to asbestos. A review of death certificates in a study of rock wool production workers identified one additional probable death. A formal comparison with expected deaths is not feasible. Four community-based case–control studies were identified, of which three reported an increased risk among SVF-exposed workers. The number of cases not exposed to asbestos was less, and residual confounding from asbestos exposure misclassification may explain the association in these studies. The toxicology review of SVF suggested that they present a low hazard mostly due to their low biopersistence, typically with a half-life in rat studies of tens of days compared to amphibole asbestos which has a half-life of 400–500 days. Conclusions The combined evidence from epidemiology and toxicology provide little evidence that exposure to SVF increases the risk of mesothelioma.  相似文献   
90.
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