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   2026篇
  免费   137篇
  国内免费   27篇
耳鼻咽喉   10篇
儿科学   58篇
妇产科学   17篇
基础医学   255篇
口腔科学   31篇
临床医学   286篇
内科学   325篇
皮肤病学   12篇
神经病学   305篇
特种医学   221篇
外科学   119篇
综合类   42篇
预防医学   175篇
眼科学   25篇
药学   194篇
中国医学   2篇
肿瘤学   113篇
  2023年   7篇
  2022年   9篇
  2021年   29篇
  2020年   13篇
  2019年   15篇
  2018年   24篇
  2017年   21篇
  2016年   22篇
  2015年   26篇
  2014年   30篇
  2013年   59篇
  2012年   69篇
  2011年   64篇
  2010年   44篇
  2009年   47篇
  2008年   70篇
  2007年   91篇
  2006年   70篇
  2005年   62篇
  2004年   71篇
  2003年   89篇
  2002年   60篇
  2001年   68篇
  2000年   68篇
  1999年   56篇
  1998年   51篇
  1997年   63篇
  1996年   39篇
  1995年   44篇
  1994年   40篇
  1993年   29篇
  1992年   48篇
  1991年   45篇
  1990年   45篇
  1989年   55篇
  1988年   59篇
  1987年   52篇
  1986年   53篇
  1985年   57篇
  1984年   46篇
  1983年   28篇
  1982年   34篇
  1981年   19篇
  1980年   28篇
  1979年   27篇
  1978年   26篇
  1977年   19篇
  1976年   29篇
  1975年   15篇
  1969年   6篇
排序方式: 共有2190条查询结果,搜索用时 31 毫秒
51.
52.
OBJECTIVE To investigate the expression of Coxsackie and Adenovirus receptor (CAR) in renal-cell carcinoma and the relationship of the CAR to the biological behavior of the carcinomas.METHODS The immunohistochemical SP method was used to detect the expression of Coxsaekie and Adenovirus receptor in 48 cases of renalcell carcinoma and in 12 cases of normal renal tissue 2 cm away from the tumor tissue.RESULTS The positive rates of CAR were 100% in 12 cases of para-tumcr normal renal tissue and 35.4% in 48 cases of renal-cell carcinoma respectively. The difference of CAR expression between them was significant (P<0.05). The grades of the tumor were as follows: 22 in Grade Ⅰ, 17in Grade Ⅱ and 9 in Grade Ⅲ with the CAR positive rate being 54.5%,23.5% and 11.1%, respectively. There was a negative correlation between CAR expression and tumor grading (P<0.05). In addition, the number of the cases in stages Ⅰ to ⅣV were 19, 13, 11 and 5 respectively, with the respective positive rates being 57.9%, 30.8%, 18.2% and 0.0%, i.e. there also was a negative relationship between CAR expression and the stage (P<0.05).CONCLUSION CAR expression is down-regulated in renal-cell carcinoma compared with normal tissue. The level of CAR may be a sensitive predictor of differentiation, invasion and metastasis. Loss of CAR expression correlates with the invasive phenotype in our analysis of renal-cell carcinoma.  相似文献   
53.
We study the effects of differentially private (DP) noise injection techniques in a survey data setting, using the release of cost of early care and education estimates from the National Survey of Early Care and Education as a motivating example. As an example of how DP noise injection affects statistical estimates, our analysis compares the relative performance of DP techniques in the context of releasing estimates of means, medians, and regression coefficients. The results show that for many statistics, basic DP techniques show good performance provided that the privacy budget does not need to be split over too many estimates. Throughout, we show that small decisions, such as the number of bins in a histogram or the scaling of a variable in a regression equation, can have sometimes dramatic effects on the end results. Because of this, it is important to develop DP techniques with an eye towards the most important aspects of the data for end users.  相似文献   
54.
55.
56.
In the last decade, public attention to the problem of commercially sexually exploited children (CSEC) has grown. This exploratory qualitative study examines adolescent pimping relationships, including how urban youth perceive these types of relationships. Study data stem from interviews with three young adult informants with first-hand knowledge of adolescent pimping, as well as three gender-specific focus group discussions with a convenience sample of 26 urban high school students who have first- or second-hand knowledge of adolescent pimping. Findings indicate that respondents believe teen pimping exists in their schools and communities, and that those exploited typically do not self-identify as victims. Respondents also believed that younger pimps are more likely to use violence to induce compliance among the girls they exploit, whereas older pimps are more likely to emotionally manipulate young women into exploitation. Further, respondents indicated that some young people agreed to exchange or sell sex for money as a favor to their boyfriends or girlfriends, and some young people believed that selling sex is acceptable under certain circumstances. The growing attention to CSEC provides an important opportunity to expand prevention efforts to reach those most affected and at risk for exploitation. The findings highlight critical areas for augmenting traditional content in school-based HIV/STI and sexuality education classes.  相似文献   
57.
Eppig  JT; Barker  JE 《Blood》1989,73(5):1373-1379
The efficacy and outcome of bone marrow transplantation therapy following lethal irradiation were examined in syngeneic mice that had a hereditary macrocytic anemia (an/an) or were genotypically normal (+/+). Successful RBC and WBC replacement, based on blood cell parameters and donor genetic markers, were observed in all combinations of transplant therapy. Nevertheless, the an/an mice died prematurely several months after treatment, whether they received +/+ or an/an marrow cells. In contrast, the +/+ recipients of either +/+ or an/an marrow cells survived for at least 1 year after transplantation. Premature death of the an/an mice was associated with lymphopenia, anemia, kidney lesions, and severe pathogen-free pneumonitis. On the basis of our results, we hypothesize that the premature deaths of an/an mice are caused by a kind of chronic irradiation damage to which an/an mice are especially susceptible.  相似文献   
58.
By the end of May 2000, 54 definite cases and 13 probable cases of vCJD had been notified in the United Kingdom by the National CJD Surveillance Unit set up in 1990. All definite cases for whom data are available are methionine homozygous at codon 129 of  相似文献   
59.
Valproic acid has been previously associated with hematologic toxicity, including a reversible myelodysplasia-like syndrome without chromosomal abnormalities. We now report three cases of acute leukemia with features of secondary leukemia associated with valproic acid therapy: two cases of acute myelogenous leukemia with multilineage dysplasia, one with trisomy 8 and one with monosomy 7, and one case of secondary acute lymphoblastic leukemia with del (7) (q22q34), del (9) (q21.11q22), del (11) (q12q23). One patient had a previous myelodysplastic syndrome while on valproic acid. Valproic acid has been previously shown to be a histone deacetylase inhibitor. Inhibition of histone deacetylase causes a relaxation of chromatin structure and thus increases susceptibility to DNA damage and sensitizes cells to radiation. We propose that valproic acid therapy may lead to secondary leukemia by increasing DNA damage through chronic inhibition of histone deacetylase.  相似文献   
60.
OBJECTIVE: To evaluate the impact of using central venous catheters (CVCs) impregnated with the combination of minocycline and rifampin on nosocomial bloodstream infections (BSIs), morbidity, and mortality in cancer patients in the ICU. DESIGN: Prospective surveillance study consisting of the following two time periods: September 1997 through August 1998 (ie, fiscal year [FY] 1998); and from September 1998 through August 1999 (ie, FY 1999). SETTING: ICUs of a tertiary care hospital in Houston, TX. PATIENTS: Cancer patients in the medical ICU (MICU) and surgical ICU (SICU). INTERVENTIONS: ICUs started using CVCs impregnated with the minocycline-rifampin combination at the beginning of FY 1999. Measurements and main results:The rates of nosocomial BSIs and other patients' characteristics were compared for the two study periods to determine the impact of using the impregnated catheters in the ICU. Patients' characteristics, including antibiotic use, were comparable for the two study periods in both the MICU and the SICU. The rate of nosocomial BSIs in the MICU unit decreased from 8.3 to 3.5 per 1,000 patient-days (p < 0.01), and decreased in the SICU from 4.8 to 1.3 per 1,000 patient-days (p < 0.01) in FY 1999. Nosocomial vancomycin-resistant enterococcus (VRE) bacteremia also decreased significantly (p = 0.004). Length of stay in the MICU and SICU significantly decreased in FY 1999 (p < 0.01 and p = 0.03, respectively). The duration of hospitalization decreased for MICU and SICU patients (p = 0.06 and p < 0.01, respectively). The rate of catheter-related infections decreased from 3.1 to 0.7 per 1,000 patient-days in FY 1999 (p = 0.02). The decrease in infections resulted in net savings of at least $1,450,000 for FY 1999. CONCLUSIONS: The use of antibiotic-impregnated CVCs in the MICU and SICU was associated with a significant decrease in nosocomial BSIs, including VRE bacteremia, catheter-related infections, and lengths of hospital and ICU stays.  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