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   1466457篇
  免费   116552篇
  国内免费   3463篇
耳鼻咽喉   19110篇
儿科学   47755篇
妇产科学   42142篇
基础医学   207977篇
口腔科学   39963篇
临床医学   130399篇
内科学   298141篇
皮肤病学   34723篇
神经病学   121776篇
特种医学   55083篇
外国民族医学   464篇
外科学   218082篇
综合类   33018篇
现状与发展   3篇
一般理论   507篇
预防医学   114851篇
眼科学   32578篇
药学   102258篇
  1篇
中国医学   3546篇
肿瘤学   84095篇
  2021年   11852篇
  2019年   12707篇
  2018年   18400篇
  2017年   13764篇
  2016年   15372篇
  2015年   17741篇
  2014年   24330篇
  2013年   36006篇
  2012年   50270篇
  2011年   52619篇
  2010年   30446篇
  2009年   28707篇
  2008年   48354篇
  2007年   50971篇
  2006年   51773篇
  2005年   49998篇
  2004年   47417篇
  2003年   45033篇
  2002年   43405篇
  2001年   73962篇
  2000年   75767篇
  1999年   62207篇
  1998年   17167篇
  1997年   15556篇
  1996年   15715篇
  1995年   14917篇
  1994年   13487篇
  1993年   12677篇
  1992年   45944篇
  1991年   43577篇
  1990年   41555篇
  1989年   39631篇
  1988年   36232篇
  1987年   35400篇
  1986年   32922篇
  1985年   31343篇
  1984年   23907篇
  1983年   20076篇
  1982年   12276篇
  1981年   10843篇
  1979年   20741篇
  1978年   14614篇
  1977年   12118篇
  1976年   11396篇
  1975年   11643篇
  1974年   14021篇
  1973年   13558篇
  1972年   12640篇
  1971年   11487篇
  1970年   10923篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Demographic and clinical data are presented on 4,138 veterans assessed in the 20-site Department of Veterans Affairs (VA) Domiciliary Care for Homeless Veterans program during its first year of operation. More than two-thirds of the veterans who were screened had been hospitalized in VA medical centers during the year before assessment, and 34 percent were hospitalized at the time of assessment. Compared with veterans who were not admitted for residential treatment, veterans who were admitted were more likely to be previously involved in mental health treatment, literally homeless rather than at risk for homelessness, and without public financial support. Specialized service programs for the homeless such as the VA domiciliary care program may also be called on to play a broader role in the discharge and rehabilitative efforts of public mental health service systems.  相似文献   
992.
BACKGROUND. A health risk appraisal (HRA) is a tool for health promotion. Conversational microcomputer-based HRAs may be more cost effective than other HRA formats. The acceptability of conversational HRAs, however, has not been demonstrated for older adults. METHODS. We studied the acceptability of a conversational microcomputer-based HRA in a sample of 247 adults at the Minnesota State Fair and the Senior Options Exposition. All users were offered the appraisal via mouse or keyboard interface. Acceptability was measured in terms of user-reported helpfulness, intent to change, time of use, and willingness to view HRA health recommendations. Data on completion time and willingness to view HRA recommendations were collected for Senior Exposition users only. Regression analyses were used to examine the combined impact of interface (mouse or keyboard), location (State Fair or Senior Exposition), age, and sex on user acceptability. Results. Interface and location had no effect on helpfulness or change ratings. Older users rated the appraisal more helpful (P less than .007). Both older and female users reported more intent to change behavior (P = .016, both). Time to use the appraisal was related to interface, age, and sex. Mouse users (P less than .0001), older users (P less than .0001) and female users (P less than .05) took significantly longer to use the appraisal. Significantly more mouse users declined to see recommendations (P less than .02). CONCLUSIONS. Older users can derive as much or more value from conversational health risk appraisals as younger users; however, a mouse interface may be less effective for this age group.  相似文献   
993.
Multiphase radon generation and transport in porous materials   总被引:5,自引:0,他引:5  
Radon generation and transport in porous materials involve solid, liquid, and gas phases in the processes of emanation, diffusion, advection, absorption, and adsorption. Oversimplifications, such as representing moist soil systems by air-phase emanation and transport models, cause theoretical inconsistencies and biases in resulting calculations. Detailed Rn rate balance equations for solid, liquid, and gas phases were analyzed and combined using phase equilibrium constants to derive a single diffusive-advective rate balance equation in the traditional form. The emanation, diffusion, and permeability coefficients in the new equation have expanded definitions and interpretations to include Rn phase transfer. Radon adsorption was characterized by an exponential moisture dependence, and diffusion and permeability constants utilized previous moisture relationships. Correct boundary and interface conditions were defined, and the unified theoretical approach was applied to field data from a diffusion-dominated system and to laboratory data from an advection-dominated system. Measured 222Rn fluxes and concentrations validated the modeled values within the measurement variability in both applications.  相似文献   
994.
Thirteen patients with a malignant germ cell tumor of the ovary have been treated with a combination of vinblastine, bleomycin, and cisplatin (VBP). In 12 patients a complete remission was reached, which was maintained in 10 of these patients. One patient with large tumor residues and a partial remission became CR after surgery. The tumor recurred in 2 patients after 6 and 27 months. Overall, 11 of these patients are in long-term remission, from 14 to 84 months after the start of treatment. VBP is an effective treatment for malignant germ cell tumors of the ovary, even in patients with large tumor residuals.  相似文献   
995.
996.
There is limited information regarding oral health status and other predictors of oral health‐related quality of life. An association between oral health status and perceived oral health‐related quality of life (OHQOL) might help clinicians motivate patients to prevent oral diseases and improve the outcome of some dental public health programs. This study evaluated the relationship between older persons' OHQOL and their functional dentition, caries, periodontal status, chronic diseases, and some demographic characteristics. A group of 733 low‐income elders (mean age 72.7 ISD=4.71, 55.6% women, 55.1% members of ethnic minority groups in the U.S. and Canada) enrolled in the TEETH clinical trial were interviewed and examined as part of their fifth annual visit for the trial. OHQOL was measured by the Geriatric Oral Health Assessment Index (GOHAI); oral health and occlusal status by clinical exams and the Eichner Index; and demographics via interviews. Elders who completed the four‐year assessment had an average of 21.5 teeth (SD=6.9). with 8.5 occluding pairs (SD=4.6), and 32% with occlusal contacts in all four occluding zones. Stepwise multiple regressions were conducted to predict total GOHAI and its subscores (Physical, Social, and Worry). Functional dentition was a less significant predictor than ethnicity and being foreign‐bom. These variables, together with gender, years since immigrating, number of carious roots, and periodontal status, could predict 32% of the variance in total GOHAI, 24% in Physical, 27% in Social, and 21 % in the Worry subscales. These findings suggest that functional dentition and caries influence older adults' OHQOL, but that ethnicity and immigrant status play a larger role.  相似文献   
997.
BACKGROUND: Adjustable gastric banding is a popular bariatric operation in Europe. About 1500 patients per year undergo a such procedures in Germany. Clinical data on the rate of long-term complications such as pouch dilatation, slippage, and band migration are available in only a few long-term studies with small numbers of patients. Meta-analyses report on comordities and reduction in weight. The rate and management of long-term complications were examined at this inquiry. METHODS: Ninety hospitals were asked about rates of band implantation, follow-up, and complications. Thirty-eight hospitals (42.2%) participated in the study. The management of complications including slippage, pouch dilatation, and band migration was analyzed. RESULTS: At 35 hospitals, 4138 patients underwent gastric banding procedures in 25 hospitals over more than 5 years. The mean follow-up rate is presently 85.3%. Long-term complications were described in 8.6% of the patients. Pouch dilatation occurred in 5.0%, slippage in 2.6%, and band migration in 1.0%. CONCLUSIONS: Laparoscopic adjustable gastric banding can effectively achieve weight loss. However, band-related and functional complications influence late outcome. The rate of long-term complications was equivalent to that already in the literature.  相似文献   
998.
OBJECTIVE: To estimate the gestational age ranges that result in optimal birth outcomes for each of four risk-defined groups. STUDY DESIGN: Retrospective cohort study of singleton late third-trimester deliveries at a large urban teaching hospital between July 1995 and September 2003. Low-risk, advanced maternal age, hypertensive and diabetic patients were identified and grouped. Rates, by day of gestation at delivery, of cesarean delivery, major maternal perineal trauma, low 5-min APGAR score and NICU admission were determined for each study group. RESULTS: Each study group had meaningful changes in rates of obstetric outcomes as a function of gestational age at delivery and these patterns differed from group to group. A unique optimal time of delivery (OTD) was estimated for each group. The low-risk group OTD was calculated to be 37 weeks 1 day to 41 weeks 0 day; the advanced maternal age group OTD was 38 weeks 5 days to 39 weeks 6 days; the hypertension group OTD was 39 weeks 2 days to 40 weeks 1 day; and the diabetes mellitus group OTD was 40 weeks 3 days to 41 weeks 1 day. CONCLUSIONS: The OTD varied based on obstetrical risk. Strategies to increase the proportion of deliveries that occur within the OTD for specific risk-defined groups could theoretically improve birth outcomes.  相似文献   
999.
Introduction     
Raymond C. Read 《Hernia》2006,10(6):454-455
  相似文献   
1000.
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