全文获取类型
收费全文 | 12628篇 |
免费 | 1176篇 |
国内免费 | 23篇 |
专业分类
耳鼻咽喉 | 196篇 |
儿科学 | 436篇 |
妇产科学 | 241篇 |
基础医学 | 1690篇 |
口腔科学 | 207篇 |
临床医学 | 1350篇 |
内科学 | 2126篇 |
皮肤病学 | 413篇 |
神经病学 | 1282篇 |
特种医学 | 379篇 |
外科学 | 1868篇 |
综合类 | 273篇 |
一般理论 | 5篇 |
预防医学 | 1520篇 |
眼科学 | 231篇 |
药学 | 859篇 |
中国医学 | 9篇 |
肿瘤学 | 742篇 |
出版年
2022年 | 88篇 |
2021年 | 200篇 |
2020年 | 112篇 |
2019年 | 203篇 |
2018年 | 238篇 |
2017年 | 196篇 |
2016年 | 177篇 |
2015年 | 186篇 |
2014年 | 329篇 |
2013年 | 492篇 |
2012年 | 590篇 |
2011年 | 669篇 |
2010年 | 400篇 |
2009年 | 335篇 |
2008年 | 653篇 |
2007年 | 719篇 |
2006年 | 645篇 |
2005年 | 616篇 |
2004年 | 589篇 |
2003年 | 561篇 |
2002年 | 538篇 |
2001年 | 355篇 |
2000年 | 408篇 |
1999年 | 331篇 |
1998年 | 174篇 |
1997年 | 111篇 |
1996年 | 114篇 |
1995年 | 112篇 |
1994年 | 112篇 |
1993年 | 105篇 |
1992年 | 272篇 |
1991年 | 225篇 |
1990年 | 254篇 |
1989年 | 210篇 |
1988年 | 212篇 |
1987年 | 195篇 |
1986年 | 175篇 |
1985年 | 207篇 |
1984年 | 132篇 |
1983年 | 92篇 |
1982年 | 107篇 |
1980年 | 75篇 |
1979年 | 115篇 |
1978年 | 100篇 |
1977年 | 77篇 |
1976年 | 89篇 |
1975年 | 80篇 |
1974年 | 94篇 |
1973年 | 96篇 |
1972年 | 74篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Kaposi sarcoma-associated herpesvirus (KSHV) is the most important etiopathological factor of Kaposi's sarcoma (KS) and some specific types of malignant lymphomas. One of the viral lytic genes encodes the KSHV complement control protein (KCP), which functionally mimics human complement inhibitors. Although this protein provides an advantage for evading the complement attack, it can serve as target for adaptive immune response. Herein, we identified anti-KCP IgG antibodies in patients with KS and KSHV-related lymphomas. KCP-specific antibodies were only detected in sera of those patients who had high titres of antibodies against lytic or latent KSHV antigens. Complement control protein domain 2 (CCP2) was found to be the most immunogenic part of the KCP protein. Furthermore, pre-incubation of KCP-expressing CHO cells with patient sera containing anti-KCP antibodies resulted in an increased complement deposition when incubated with human serum. 相似文献
992.
T A Lieu S B Black P Ray M Chellino H R Shinefield N E Adler 《American journal of public health》1994,84(10):1621-1625
OBJECTIVES. Improving the timely delivery of childhood immunizations has become a national imperative. This study aimed to identify nonfinancial predictors of delayed immunization among patients with good financial access to preventive care. METHODS. This prospective cohort study used telephone interviews and a computerized immunization tracking system to evaluate 13-month-old children (n = 530) in a regional group-model health maintenance organization. RESULTS. More than one third of parents interviewed did not know when the next immunization was due. Thirteen percent were late for the measles-mumps-rubella immunization, recommended at 15 months of age, by 90 days or more. Independent predictors of delayed immunization included having a larger number of children (odds ratio [OR] = 1.4, P < .01), not having a regular doctor (OR = 2.9, P < .05), not knowing when the shot was due (OR = 2.0, P < .01), and not worrying about the risks of shots (OR = 1.4, P < .05). CONCLUSIONS. Financial access alone does not guarantee timely childhood immunization. In managed care settings, which may cover increasing numbers of children under health care reform, interventions are needed to better inform parents of when immunizations are due. 相似文献
993.
Xiaoming Li Bonita Stanton Maureen M. Black Daniel Romer Izabel Ricardo Linda Kaljee 《Journal of urban health》1994,71(2):252-266
The scientific literature and popular media suggest that variations in housing structure and neighborhood influence risk behaviors among youths living in low-income urban communities. To explore the importance of these factors on early sexual intercourse, substance use, drug trafficking, and school truancy, data from a community-based survey, conducted in six public housing developments in a major eastern metropolis, were analyzed. The survey group consisted of 300 youths aged 9 through 15 years. There were minimal differences in three potential mediators of risk behaviors (e.g., perceived social support, parenting style, and perceived risk exposure) and in self-reported adolescent risk behaviors among youths residing in different housing developments and between youths residing in high-rise and in low-rise structures. These findings do not support the hypothesis that within a risk-dense low-income environment, variations in building structure or in neighborhood are associated with differences in adolescent risk behaviors. 相似文献
994.
Social determinants are gaining momentum in public health practice. Many proposed solutions for tackling social determinants are outside the scope of local public health professionals. This article reviews the literature to find possible moderating variables which may buffer the effects of the social determinants of health at the local level, and allow social determinants to be addressed within the purview of local health departments. The systematic approach employed for this article entailed searches of electronic academic databases (PubMed, EBSCO and Medline) and additional searches using Internet search engines and relevant websites for articles published between 1,975 and May 2010. The search revealed 2,554 articles, and 36 were determined appropriate for inclusion. The purpose of the search was to identify published articles relating to social determinants of health, social capital and effective approaches for addressing both at the level of the local health department. The search was then expanded to include unpublished material, to include the perspectives of local health departments. This process resulted in the inclusion of content from five sources. In this article, the case is made for focusing on social capital interventions to mitigate health problems associated with social determinants. Examples of successful interventions are provided to aid public health professionals in developing locale-specific solutions for addressing social determinants. 相似文献
995.
Effects of zearalenone on in utero development in rats. 总被引:1,自引:0,他引:1
Thomas F X Collins Robert L Sprando Thomas N Black Nicholas Olejnik Robert M Eppley Hamida Z Alam James Rorie Dennis I Ruggles 《Food and chemical toxicology》2006,44(9):1455-1465
Zearalenone (ZE), an estrogenic mycotoxin produced by Fusarium graminearum or F. roseum, is one of the most common contaminants of cereal grains world-wide. The objective of this study was to determine the effects of ZE on in utero development of rats. Pregnant female Charles River Sprague-Dawley rats were gavaged once daily with ZE (in corn oil) at doses of 0, 1, 2, 4, or 8 mg/kg body weight on gestation days (GD) 6-19. All females survived to cesarean section on GD 20. At cesarean section, reproductive and developmental parameters were measured and blood was taken for hormone analysis. Dose-related decreases were seen in maternal feed consumption and body weight gain in all treated groups. Delayed fetal development was linked to maternal toxicity. Fetal body weight was significantly decreased in both sexes in all treated groups. ZE retarded skeletal ossification at 4 and 8 mg/kg. Fetal anogenital index (anogenital distance normalized for body weight) was increased in all treated groups, indicating an androgenic effect of ZE during fetal development. Fetal viability was significantly decreased at 8 mg/kg; significant decreases were observed in number of viable fetuses, and number of litters totally resorbed. At 4 and 8 mg/kg, maternal liver-body weight ratios were significantly increased and organ-brain weight ratios for weights of liver, heart, spleen, kidneys, and ovaries were significantly decreased. Gonadotropins (LH, FSH, and prolactin) and sex steroids (progesterone and estradiol) were analyzed from the blood serum obtained at cesarean section. LH in the 0, 1, 2, and 4 mg/kg groups showed minimal variation, and slightly increased at 8 mg/kg. FSH was decreased in the 1, 2, and 4 mg/kg groups, but the level at 8 mg/kg was slightly higher than the control level. Prolactin level was not affected at 1 mg/kg, slightly increased at 2 and 4 mg/kg, and significantly increased at 8 mg/kg. Progesterone was decreased at 2, 4, and 8 mg/kg and the decreases were significant at 2 and 4 mg/kg. Estradiol level was not affected at 1mg/kg, but dose-related decreases were observed at 2, 4, and 8 mg/kg. Only the 8 mg/kg level of estradiol was significantly decreased. In summary, ZE was maternally toxic and fetotoxic but not teratogenic. The increased anogenital distance observed in male and female fetuses was considered a hormonal change rather than a teratologic response. The increased anogenital distance indicated an androgenic effect. Based on the dose-related maternal and fetal toxicity in all treated groups, the NOEL for reproductive and teratogenic effects was less than 1 mg/kg. 相似文献
996.
Incidence of childhood brain and other non-haematopoietic neoplasms near nuclear sites in Scotland, 1975-94 下载免费PDF全文
OBJECTIVES: To examine the risk of cancers other than leukaemia and non- Hodgkin's lymphoma in children resident in the vicinity of nuclear sites in Scotland. METHODS: The study dataset comprised registrations of cancer other than leukaemia and non-Hodgkin's lymphoma diagnosed in children aged under 15 in the period 1975-94. These were validated for completeness and accuracy and analysed in two groups: (a) tumours of the central nervous system and (b) other malignant tumours (excluding leukaemia and non-Hodgkin's lymphoma). Around each nuclear site observed cases (O) were enumerated and expected numbers (E) calculated with adjustment for age, sex, deprivation, and an urban-rural category. Stone's maximum likelihood ratio test (MLR) was used to determine whether there was any evidence of increased risk of these neoplasms among children living within 25 km of one of the nuclear sites investigated. The significance level of each MLR statistic was estimated by simulation. RESULTS: More tumours of the central nervous system were observed than expected within 25 km of Dounreay (O/E = 1.14), Hunterston (1.14), and Rosyth (1.22). These results were based on 2, 26, and 136 observed cases, respectively. The unconditional MLR was significant only for Rosyth (p = 0.006). The conditional application of the MLR test for Rosyth was not significant (p = 0.771). For the group of other malignant neoplasms, the unconditional MLR test was not significant for any of the seven sites. CONCLUSIONS: There was no evidence for generally increased risk of either tumours of the central nervous system or other malignant tumours in children living near nuclear sites. The significant excess of tumours of the central nervous system around Rosyth is likely to be due to the high incidence of these tumours in east central Scotland. Further investigations in this area are warranted.
相似文献
997.
998.
Analysis of the effects of alpha 1-adrenoceptor antagonists on noradrenaline-mediated contraction of rat small mesenteric artery. 下载免费PDF全文
P. H. Van der Graaf N. P. Shankley J. W. Black 《British journal of pharmacology》1996,118(5):1308-1316
1. In this study, we examined the interaction between noradrenaline (NA) and phenylephrine (PE) with seven antagonists (prazosin, tamsulosin, phentolamine, WB-4101, 5-methylurapidil, spiperone and HV 723) in an attempt to characterize the alpha 1-adrenoceptor population of the rat isolated small mesenteric artery (SMA) preparation. 2. Six of the seven antagonists investigated produced concentration-dependent, parallel, rightward shift of the NA concentration-effect (E/[A]) curves. The exception was tamsulosin, which produced significant decrease of the upper asymptote. In the case of 5-methylurapidil and HV723, the Schild plot slope parameters were not significantly different from unity over the range of concentrations used. However, the Schild plot slopes obtained for the other antagonists were all significantly greater than unity, inconsistent with expectations for simple competitive antagonism. 3. HV723, prazosin and tamsulosin were also tested using PE as an agonist. All three antagonists produced concentration-dependent, parallel, rightward shifts of the PE curves and Schild analysis yielded slope parameters not significantly different from unity. The pKB estimates obtained for tamsulosin and prazosin were not significantly different from the pA2 values obtained when NA was used as agonist. In the case of HV723, the 95% confidence intervals for the pKB values yielded with NA and PE did not overlap (pKB = 8.80-9.13 and 8.15-8.77 for NA and PE, respectively). 4. In the absence of evidence to indicate that the steep Schild plots were due to failure to satisfy the basic criteria for quantitative analysis in a one-receptor system, we considered the possibility that the complexity was caused by an action of NA at inhibitory D1 receptors. The selective D1 receptor antagonists, SCH-23390 (10 nM), had no significant effect on the NA E/[A] control curve, but the apparent potency of 100 nM prazosin was reduced by approximately 3.5 fold. 5. This study indicates that the steep Schild plots obtained from the interaction between NA and alpha 1-adrenoceptor antagonists were due to the simultaneous activation of inhibitory D1 receptors by NA. Notwithstanding this complexity, our explanatory model of the system (see Appendix) suggests that the antagonist affinity values estimated in the absence of D1 receptor block were not significantly affected by this other action of NA. The low affinity estimate obtained for prazosin suggests that the pharmacologically-defined alpha IL-subtype operates in the SMA. 相似文献
999.
Analysis of variation in L-365,260 competition curves in radioligand binding assays. 总被引:1,自引:0,他引:1 下载免费PDF全文
E. A. Harper S. P. Roberts N. P. Shankley J. W. Black 《British journal of pharmacology》1996,118(7):1717-1726
1. For several years, we have used the cholecystokinin (CCK)B/gastrin receptor selective antagonist, L-365,260, as a reference compound in a variety of studies in CCKB/gastrin receptor radioligand binding assays. Here, we have analysed the competition curve data sets obtained between L-365,260 and [125I]-BH-CCK8S in guinea-pig gastric gland and mouse and rat cerebral cortex preparations. 2. Competition curves obtained for L-365,260 in the mouse cortex assay were not different from rectangular hyperbolae (slope = 1.01 +/- 0.02) implying the presence of a single population of binding sites (pKI = 8.41 +/- 0.01; data from 47 experiments, slope constrained to unity). However, in the rat cortex and guinea-pig gastric gland assays, the mean slope of the competition curves was significantly less than one and the mean apparent pKI significantly lower than that obtained in the mouse cortex (slope = 0.85 +/- 0.03, 0.90 +/- 0.03; apparent pKI = 7.98 +/- 0.05, 8.07 +/- 0.05; 48 and 45 experiments, in rat and guinea-pig, respectively). The distribution of the individual pKI and slope estimates of the competition curves in these two assays was consistent with expectations for the variable expression (in terms of absolute number and proportion) of two binding sites. The two sites were characterized by pKI values for L-365,260 of 8.50 +/- 0.04 and 8.48 +/- 0.04 for the high affinity site and 7.32 +/- 0.04 and 7.22 +/- 0.06 for the low affinity site in guinea-pig and rat, respectively. 3. The affinity estimates for L-365,260, although obtained on different tissues, are consistent with data obtained from the analysis of L-365,260 antagonism of pentagastrin-stimulated responses in mouse and rat stomach (acid secretion) and guinea-pig gastric muscle (isotonic contraction) assays. To this extent, these data suggest the existence of two CCKB/gastrin receptor subtypes. 相似文献
1000.
R L Davis D Rubanowice H R Shinefield N Lewis D Gu S B Black F DeStefano P Gargiullo J P Mullooly R S Thompson R T Chen 《JAMA》1999,282(6):547-553
CONTEXT: Studies have noted that health care professionals may not conform to proper immunization schedules for premature and low-birth-weight infants in the United States. Little is known about the success of current efforts to immunize these high-risk infants. OBJECTIVE: To describe current immunization practices for premature and low-birth-weight infants and ascertain risk factors for poor immunization status, using large population-based data sources. DESIGN AND SETTING: Cohort and case-control analyses of immunization data tracked from March 1991 through March 1997 for 3 large health maintenance organizations (HMOs) participating in the Centers for Disease Control and Prevention's Vaccine Safety Datalink project. PARTICIPANTS: A total of 11580 low-birth-weight and premature infants were enrolled from birth to age 2 months; 6832 of these were continuously enrolled from birth to age 24 months. At age 2 months, there were 173373 full-term, normal-birth-weight infants enrolled as controls; at age 24 months, there were 103 324. MAIN OUTCOME MEASURES: Age-specific immunization status by prematurity and birth weight (<1500 g, 1500-2500 g, born at <38 weeks' gestation with birth weight of >2500 g, or full-term with normal birth weight) and patient characteristics associated with up-to-date status. RESULTS: At each age, infants weighing less than 1500 g at birth had lower up-to-date immunization levels than other infants. At age 6 months, 52% to 65% of infants weighing less than 1500 g were up-to-date at each of the 3 HMOs compared with 69% to 73% of those weighing 1500 to 2500 g, 66% to 80% of premature infants weighing more than 2500 g, and 65% to 76% of full-term, normal-birth-weight infants. By age 24 months, 78% to 86% of infants weighing less than 1500 g were up-to-date, significantly less than heavier infants, who had levels of 84% to 89%. Well-child preventive care strongly predicted immunization status, while concomitant pulmonary disease did not. CONCLUSIONS: Our data suggest that infants born prematurely are vaccinated at levels approaching that of the general population, but levels of vaccination for very low-birth-weight infants lag slightly behind. 相似文献