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   22120篇
  免费   1384篇
  国内免费   38篇
耳鼻咽喉   144篇
儿科学   749篇
妇产科学   769篇
基础医学   3000篇
口腔科学   283篇
临床医学   3612篇
内科学   4239篇
皮肤病学   227篇
神经病学   2168篇
特种医学   449篇
外科学   1655篇
综合类   269篇
一般理论   32篇
预防医学   2906篇
眼科学   204篇
药学   1258篇
中国医学   15篇
肿瘤学   1563篇
  2023年   98篇
  2022年   177篇
  2021年   354篇
  2020年   233篇
  2019年   393篇
  2018年   427篇
  2017年   318篇
  2016年   396篇
  2015年   445篇
  2014年   661篇
  2013年   1045篇
  2012年   1513篇
  2011年   1496篇
  2010年   817篇
  2009年   818篇
  2008年   1433篇
  2007年   1422篇
  2006年   1436篇
  2005年   1446篇
  2004年   1372篇
  2003年   1357篇
  2002年   1290篇
  2001年   206篇
  2000年   195篇
  1999年   228篇
  1998年   266篇
  1997年   247篇
  1996年   199篇
  1995年   204篇
  1994年   179篇
  1993年   189篇
  1992年   181篇
  1991年   175篇
  1990年   162篇
  1989年   159篇
  1988年   151篇
  1987年   156篇
  1986年   113篇
  1985年   124篇
  1984年   148篇
  1983年   120篇
  1982年   146篇
  1981年   118篇
  1980年   119篇
  1979年   94篇
  1978年   84篇
  1977年   63篇
  1976年   70篇
  1975年   46篇
  1974年   63篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Families of persons with mental illness often benefit from participating in interventions which provide education and support. The present study describes outcomes reported by 424 families who participated in one such intervention, the Journey of Hope (JOH) program. Hierarchical regression analyses found that program outcomes—increased knowledge of the causes and treatment of mental illness, increased understanding of the mental health service system, and improved morale—were predictive of one another. JOH therefore may provide families with the knowledge and support they need to strengthen their ability to cope with their relative's mental illness.  相似文献   
982.
Association studies on susceptibility to breast cancer using single nucleotide polymorphisms (SNP) in the progesterone receptor (PGR) gene have been previously published, but the results have been inconclusive. We used a comprehensive SNP-tagging approach to search for low-penetrance susceptibility alleles in a study of up to 4,647 cases and 4,564 controls, in a two-stage study design. We identified seven tagging SNPs using genotype data from the National Institute of Environmental Health Sciences (NIEHS) Environmental Genome Project and typed these, and an additional three SNPs, in 2,345 breast cancer cases and 2,284 controls (set 1). Three SNPs showed no evidence for association and were not studied further, whereas seven SNPs (rs11571171, rs7116336, rs660149, rs10895068, rs500760, rs566351, and rs1042838) exhibited significant associations at P < 0.1 using either a heterogeneity or trend test and progressed to be genotyped in set 2. After both stages, only one SNP was significantly associated with an increased risk of breast cancer - the PGR-12 (rs1042638) V660L valine to leucine polymorphism [VL heterozygotes (odds ratio, 1.13; 95% confidence interval, 1.03-1.24) and the LL homozygotes (odds ratio, 1.30; 95% confidence interval, 0.98-1.73), P(het) = 0.008, P(trend) = 0.002]. Similar estimates were obtained in a combined analysis of our data with those from three other published studies. We conclude that the 660L allele may be associated with a moderately increased risk of breast cancer, but that other common SNPs in the PGR gene are unlikely to be associated with a substantial risk of breast cancer.  相似文献   
983.
Previous studies have identified low patient accrual in large-scale cancer clinical trials, particularly for underrepresented groups, such as ethnic minorities, females, and patients >65 years. As there have been few studies examining participation in cancer genetics epidemiologic research, our objective was to identify clinical and demographic factors predicting enrollment in these studies. A total of 1,111 patients diagnosed with colorectal cancer presenting to a gastrointestinal oncology clinic were approached to enroll in a study investigating the role of the MSH6 gene in familial colorectal cancer. Patient consent was sought for providing a blood specimen for DNA analysis and review of medical records/tumor specimens and contacting family members to confirm the family history of cancer. Seven predictor variables for enrollment (age, sex, ethnicity, family history of colorectal cancer in a first-degree relative, presence of children, insurance type, and type of visit) were analyzed using logistic regression analysis to determine the effect on decision to enroll. Of 1,111 patients approached, 696 (62.6%) enrolled in the study. Of these approached individuals, 4.2% were of nonwhite ethnicity and 33.5% were age > or =65 years. Patients of white ethnicity [odds ratio (OR), 2.10; P = 0.018], males (OR, 1.47; P = 0.002), those ages < or =65 years (OR, 1.42; P = 0.009), and those with a first-degree relative with colorectal cancer (OR, 1.57; P = 0.005) were significantly more likely to enroll. Fewer than 4% of all participants denied permission for the study researchers to access information from medical records or to be recontacted by researchers to discuss the enrollment of additional family members. Our data suggest that, once subjects decided to enroll, the majority (88%) was comfortable with consenting to all study components, including the creation of cell lines and future recontact. Low participation rates for ethnic minorities, females, and elderly patients are similar for both cancer genetics and clinical trial studies.  相似文献   
984.
Apoptotic markers and tumor-associated antigens might be suitable to indicate the response to radiochemotherapy early. We analyzed the courses of nucleosomes, CEA, CA 19-9 and CYFRA 21-1 in 25 colorectal cancer patients during radiochemotherapy (4 postoperative, 13 preoperative, 8 local relapse therapy). Blood was taken before therapy, daily during the first week, once weekly during the following weeks, and at the end of the radiochemotherapy. After a temporary decline 6 h after the first irradiation, nucleosomes rose in most patients rapidly reaching a maximum during the first days which was followed by a subsequent decrease. In patients receiving postoperative therapy after complete resection of tumor, nucleosome levels generally were lower than in patients with preoperative or relapse therapy. Correspondingly, CEA, CA 19-9 and CYFRA 21-1 levels of postoperatively treated patients were the lowest whereas those with tumor relapse had the highest ones. During preoperative therapy, lower nucleosome concentrations were found in patients with response to therapy resulting in a smaller area under the curve of days 1-3 (AUC) than in those with progressive disease (p = 0.028). The other parameters did not indicate the response to therapy at the initial treatment phase. In conclusion, the course of nucleosomes (AUC) might be valuable for the early prediction of therapy response in preoperatively treated colorectal cancer patients.  相似文献   
985.
CONTEXT: Through medical decision making, physicians in the U.S. influence the spending of >$1.3 trillion or 15% of the gross domestic product. U.S. physicians are challenged to identify areas of clinical practice to improve while cutting cost and increasing access. Primary screening for colorectal cancer is a good example to illustrate this point.OBJECTIVE: To apply a population-based method of medical decision making in the area of primary screening for colorectal cancer in order to illustrate a reduction in health care costs while increasing access and maintaining quality of care.DESIGN: We used a combination of (a) census population data, (b) National Cancer Institute Survey data on screening rates, and (c) charge data to estimate the current costs of colorectal cancer screening. We also estimated cost and capacity increases that would occur under various other screening scenarios. These included all currently screened subjects receiving annual fecal occult blood testing (FOBT), all currently unscreened individuals undergoing either colonoscopy every decade or annual FOBT, and all eligible subjects undergoing annual FOBT.Main outcome measures: Cost and access differences between current screening activity and other potential scenarios compliant with guidelines.RESULTS: Screening for colorectal cancer with yearly, six-window, rehydrated FOBT for all normal-risk individuals over the age of 50 has the potential to screen 3,813,095 more Americans for colon cancer yearly than are currently being screened, while costing $8.7 billion less per decade than what is currently being spent on screening a fraction of the population. Looking into the future, it is possible to increase screening rates from 50% to 100%, while saving almost $10 billion per decade by using FOBT for all eligible Americans. In practice, some proportion of these benefits would be realized as the calculations assume a 100% patient compliance rate.CONCLUSIONS: Considering a population-based approach and the balance among quality, accessibility, and cost parameters, we recommend primary screening for colorectal cancer to be based on yearly six-window, rehydrated FOBT. Colonoscopy due to cost and access issues should be relegated to secondary screening and case finding.  相似文献   
986.
Newborn hearing screening: costs of establishing a program.   总被引:3,自引:0,他引:3  
OBJECTIVE: To evaluate the costs and performance characteristics associated with the start-up phase of Universal Newborn Hearing Screening Programs, one utilizing automated auditory brainstem response (AABR) and the other using transient evoked otoacoustic emissions (TEOAE). STUDY DESIGN: Economic and performance data were collected at the initiation of both screening programs. Data were collected until 1500 newborn infants were screened or until a referral rate for further audiologic evaluation at hospital discharge of less than or equal to 5% was achieved. Data collected included screening pass/fail rates, referral rates and personnel, equipment, and supply utilization. Actual costs of personnel, equipment, and supplies were used. Statistical comparisons of proportions using z-statistic with the one-tailed test and an alpha of 0.01 were made. RESULTS: Screening in the AABR program was performed by neonatal nurses, whereas screening in the TEOAE program was performed by master's level audiologists. The average age at initial screen was 29 hours for TEOAE, and 9.5 hours for AABR. Eighty-four percent of infants was screened within 24 hours in the AABR program, in contrast to 35% in the TEOAE program. Throughout the duration of the study, the referral rate at hospital discharge remained approximately 15% for the TEOAE program. The AABR referral rate began at 8% and was less than 4% at the completion of the study. Pre-discharge total costs for initiating and establishing the programs were US$49,316 for TEOAE and US$47,553 for AABR. Cost per infant screened was US$32.23 and US$33.68, respectively. When post-discharge screening and diagnostic evaluation costs were included, the total cost per infant screened was US$58.07 for TEOAE and US$45.85 for AABR. CONCLUSION: AABR appears to be the preferred method for universal newborn hearing screening. AABR was associated with the lowest costs, achieved the lowest referral rates at hospital discharge, and had the quickest learning curve to achieve those rates.  相似文献   
987.
Lack of WRN results in extensive deletion at nonhomologous joining ends.   总被引:7,自引:0,他引:7  
Loss of WRN causes the genomic instability progeroid syndrome, Werner syndrome. WRN encodes a multifunctional nuclear protein with 3'-->5' exonuclease and 3'-->5' helicase activities. Linear plasmids with noncompatible ends introduced to Werner syndrome cells underwent extensive deletions at nonhomologous joining ends, particularly at the 3' protruding single-stranded end. This extensive deletion phenotype was complemented by wild-type WRN. These results suggest that WRN can out-compete other exonucleases that participate in double-strand break repair or stabilize the broken DNA end.  相似文献   
988.
A randomized isoflavone intervention among premenopausal women.   总被引:1,自引:0,他引:1  
Isoflavones, phytoestrogens contained in soy foods, may play a role in breast cancer prevention. This randomized double-blinded trial with 34 premenopausal women investigated whether 100 mg of isoflavones per day versus placebo affects the ovulatory cycle during 1 year. Compliance with the study regimen was confirmed by the increase of urinary isoflavone excretion among the intervention group. Blood samples were taken 5 days after ovulation as determined by an ovulation kit, at baseline, and at months 1, 3, 6, and 12. Serum levels of estrone, estradiol, estrone sulfate, progesterone, sex hormone-binding globulin, follicle-stimulating hormone, and luteinizing hormone were quantified by immunoassay; free estradiol was calculated. We applied the method of least squares to fit general linear models to test for an intervention effect while taking into account the repeated measurement design. Except for a small difference in age, the two groups were comparable at baseline. Menstrual cycle length did not change significantly during the intervention [F(1,32) = 0.69; P = 0.44]. During 1 year, we did not observe any significant changes in hormone levels by treatment group. The difference in change between intervention and control group was -13.0 pg/ml (95% confidence interval, -57.5 to 31.5) for estradiol and 6.9 pg/ml (95% confidence interval, -17.8 to 31.5) for estrone. Exclusion of 22 non-ovulatory cycles, noncompliant women, or non-Asian women did not affect the results. These findings do not support the hypothesis that isoflavones affect the ovulatory cycles of premenopausal women over a 1-year period. However, isoflavones alone may have different effects on the reproductive cycle than isoflavones present in soy foods.  相似文献   
989.
Although most colorectal cancers arise from adenomatous polyps, most adenomas do not progress to invasive cancer. Understanding the epidemiology of advanced adenomas, specifically those with severe dysplasia, carcinoma in situ, or intramucosal carcinoma, is crucial to uncovering why some adenomas progress and some do not. Using data from four colonoscopy-based adenoma case-control studies, we compared two case groups: subjects with advanced adenomas (those with severe dysplasia, carcinoma in situ, or intramucosal carcinoma; n = 119) and subjects with nonadvanced adenomas (those with none, mild, or moderate dysplasia; n = 441) to a polyp-free control group (n = 1866) in regard to frequently studied risk factors for colorectal neoplasia. All of the cases were newly diagnosed and had no prior history of adenomas. We used an unordered polytomous logistic model to calculate multivariate odds ratios for advanced and nonadvanced adenoma cases relative to polyp-free controls. Among women, ever use of hormone replacement therapy was more strongly associated with reduced risk of advanced adenomas relative to polyp-free controls [odds ratio (OR), 0.4; 95% confidence interval (CI), 0.2-0.9] than with reduced risk of nonadvanced adenomas (OR, 0.7; 95% CI, 0.4-1.0). Among men, increased physical activity (>or=2 h/week) was more strongly associated with reduced risk for advanced adenomas (OR, 0.4; 95% CI, 0.2-1.0) than with reduced risk for nonadvanced adenomas (OR, 0.8; 95% CI, 0.5-1.2). Apart from these differences, most other risk factors, including body size and cigarette smoking were similar in their association with advanced and nonadvanced adenomas, suggesting that many risk factors for colorectal neoplasia may be important to adenoma formation but not to dysplasia per se.  相似文献   
990.
The purpose of this study was to optimize the antitumor andantiangiogenic activities of pegylated IFN-alpha (PEG-IFN-alpha)alone or in combination with paclitaxel against SKOV3ip1 human ovarian cancer cells growing orthotopically in female nude mice. Seven days after the i.p. implantation of tumor cells, groups of mice (n = 10) were injected s.c. once per week (for 4 weeks) with different doses of PEG-IFN-alpha (3,500, 7,000, 35,000, and 350,000 units). PEG-IFN-alpha at 7,000 units significantly decreased tumor incidence and volume. At doses exceeding 7,000 units, PEG-IFN-alpha was less efficacious. In another set of studies conducted 7 days after the i.p. implantation of SKOV3ip1 cells, groups of mice (n = 10) received (once per week for 4 weeks) either s.c. administrations of PEG-IFN-alpha (7,000 units), i.p. injections of paclitaxel (100 microg/wk), or a combination of PEG-IFN-alpha and paclitaxel. The mice were killed 7 days after the last treatment, and tumor burden was assessed. Administration of PEG-IFN-alpha at the optimal biological dose (7,000 units) in combination with paclitaxel significantly decreased angiogenesis and progressive growth of human ovarian carcinoma cells in a synergistic fashion. The combination therapy produced the most significant inhibition in expression of the proangiogenic molecules basic fibroblast growth factor and matrix metalloproteinase-9. Decreased microvessel density, decreased proliferating cell nuclear antigen staining, and increased endothelial cell apoptosis also correlated with therapeutic success. Collectively, the data suggest that combining the optimal biological dose of PEG-IFN-alpha with paclitaxel may provide a novel and effective approach to the treatment of human ovarian carcinoma.  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