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   49537篇
  免费   4066篇
  国内免费   80篇
耳鼻咽喉   634篇
儿科学   1316篇
妇产科学   1416篇
基础医学   7052篇
口腔科学   1296篇
临床医学   6008篇
内科学   8634篇
皮肤病学   609篇
神经病学   3962篇
特种医学   2075篇
外国民族医学   1篇
外科学   6377篇
综合类   880篇
一般理论   24篇
预防医学   5549篇
眼科学   1113篇
药学   3673篇
  5篇
中国医学   62篇
肿瘤学   2997篇
  2021年   758篇
  2020年   441篇
  2019年   739篇
  2018年   831篇
  2017年   668篇
  2016年   636篇
  2015年   753篇
  2014年   1004篇
  2013年   1559篇
  2012年   2278篇
  2011年   2361篇
  2010年   1260篇
  2009年   1045篇
  2008年   1972篇
  2007年   2120篇
  2006年   2085篇
  2005年   2090篇
  2004年   1890篇
  2003年   1723篇
  2002年   1757篇
  2001年   1629篇
  2000年   1726篇
  1999年   1470篇
  1998年   627篇
  1997年   502篇
  1996年   507篇
  1995年   520篇
  1994年   437篇
  1993年   442篇
  1992年   1265篇
  1991年   1165篇
  1990年   1150篇
  1989年   1074篇
  1988年   991篇
  1987年   1001篇
  1986年   922篇
  1985年   917篇
  1984年   714篇
  1983年   625篇
  1982年   446篇
  1981年   389篇
  1980年   402篇
  1979年   658篇
  1978年   523篇
  1977年   415篇
  1976年   403篇
  1974年   453篇
  1973年   438篇
  1972年   454篇
  1971年   426篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
CONTEXT: Vaccine-preventable diseases among adults are major contributing causes of morbidity and mortality in the United States. However, adult immunizations continue to be underutilized in both urban and rural areas. PURPOSE: To evaluate the effectiveness of a community-wide education campaign and mailed reminders promoting pneumococcal immunizations to rural Medicare beneficiaries. METHODS: We implemented a community-wide education campaign, and mailed reminders were sent to Medicare beneficiaries in 1 media market in Montana to increase pneumococcal immunizations. In a second distinct media market, mailed reminders only were sent to beneficiaries. FINDINGS: The proportion of respondents aged 65 years and older aware of pneumococcal immunizations increased significantly from baseline to follow-up among respondents both in the education-plus-reminder (63% to 78%, P = 0.04) and the reminder-only (64% to 74%, P = 0.05) markets. Overall from 1998 to 1999, there was a 3.7-percentage-point increase in pneumococcal immunization claims for Medicare beneficiaries in the education-plus-reminder market and a 1.5-percentage-point increase in the reminder-only market. Medicare beneficiaries sent reminders in the education-plus-reminder market compared to those in the reminder-only market were more likely to have a claim for pneumococcal immunization in 1999 (odds ratio 1.18, 95% confidence interval 1.08 to 1.28). The results suggest that these quality improvement strategies (community education plus reminders and reminders alone) modestly increased pneumococcal immunization awareness and pneumococcal immunization among rural adults. Mailed reminder exposure was associated with an increased prevalence of pneumococcal immunizations between 1998 and 1999 and was augmented somewhat by the education campaign.  相似文献   
52.
53.
The leading cause of postoperative morbidity in patients undergoing major head and neck surgical procedures is postoperative infection. This prospective randomized multi-institutional clinical trial was designed to compare the effectiveness of clindamycin phosphate and high-dose cefazolin sodium therapy in preventing postoperative wound sepsis in patients undergoing contaminated head and neck surgical procedures in which flap reconstruction was required. Either clindamycin phosphate (900 mg) or cefazolin sodium (2 g) therapy was instituted intravenously prior to surgery and continued every 8 hours, for a total of 24 hours. The patients received postoperative follow-up, and the wounds were graded according to the worst condition observed. One hundred cases were evaluated. Fifty-one patients received clindamycin and 49 patients received high doses of cefazolin; wound infection developed in 10 patients (19.6%) and 11 patients (21.6%), respectively. This difference was not statistically significant. The average duration of surgery was approximately 8 hours for both the infected and the noninfected groups of patients. High-dose cefazolin and clindamycin have similar efficacy when administered prophylactically under these circumstances. Reconstruction with free vascularized tissue may aid in reducing postoperative wound infection.  相似文献   
54.
The Toronto Sexual Contact Study comprises a cohort of 249 male sexual contacts of men with HIV disease which has been followed every 3 months for almost 5 years. On enrollment 143 were seropositive and 16 seroconverted during the follow-up period. By 31 December 1989, 41 of the 159 seropositive cohort members had developed AIDS. Using Cox relative risk regression models, we investigated the association of a number of laboratory and clinical variables and progression to AIDS. Fixed covariate models examined laboratory variables from the enrollment visit of cohort members, with time calculated from this date. In models assessing time dependent covariates, time was calculated from the estimated date of HIV infection. In the univariate models of either fixed or time dependent covariates, many variables were significantly associated with risk of progression to AIDS (T4 cell count, T4/T8 ratio, blastogenic responses to phytohemagglutinin, concanavalin A, and pokeweed mitogen, serum IgA, appearance of p24 antigen, and the development of oral hairy leukoplakia, thrush, or herpes zoster). Appearance of persistent generalized lymphadenopathy was not associated with increased risk of progression. In the multivariate model which evaluated fixed laboratory covariates, T4/T8 ratio, IgA level, and PHA response at enrollment were significantly associated with elevated risk.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
55.
The bedside assessment of dysphagia may be difficult, due to the inability to witness the act of swallowing directly. The milk test described in this paper gives a good assessment of swallowing, is cheap and easily portable and allows an instant decision to be made without recourse to special investigations.  相似文献   
56.
Despite interest in the in vivo control of gonadotropin release, valid assessment of the physiological regulation of the pulsatile secretion of the gonadotropin FSH has been hampered by the uncertain validity and reliability of available FSH peak detection algorithms. Difficulties in identifying FSH peaks accurately are believed to arise in part because of the slow metabolic clearance of this glycoprotein hormone. Here, we have used two complementary strategies to test the validity of FSH pulse detection. First, by means of a computer-assisted mathematical model for simulating episodic hormone secretion, we evaluated the effects of various putative FSH secretory pulse amplitudes and half-lives on the sensitivity and positive accuracy of peak detection. Secondly, we used an in vivo primate animal model, in which presumptively true FSH pulses were evaluated independently by continuous electrophysiological monitoring of mediobasal hypothalamic multiunit activity. These two approaches allowed us to define optimal pulse analysis parameters that yield maximal sensitivity and positive accuracy for detecting FSH peaks in synthetic and biological time series. We found (as predicted intuitively) that increasing half-times of hormone disappearance decrease both the sensitivity and positive accuracy of peak detection for any given peak detection thresholds and hormone secretory amplitudes. However, adequately sampled episodic FSH time series could be analyzed for FSH pulsatility by an appropriately constrained, objective computerized algorithm with reasonable (less than 10-15%) false negative and false positive errors, such that resultant sensitivity and positive accuracy exceed 85-90%. Of interest, computer simulations and the in vivo animal model exhibited similar discriminative capabilities. We conclude that increasing half-times of hormone (e.g. FSH) removal do impair hormone peak detection sensitivity and positive accuracy. Nevertheless, gonadotropin time series can be analyzed for FSH pulsatility in a valid manner with adequately constrained false negative and false positive error rates.  相似文献   
57.
58.
The human squamous carcinoma-reactive murine monoclonal antibody PF1/D was used to derive a conjugate with the Vinca derivative 4-desacetylvinblastine-3-carboxyhydrazide (PF1/D-DAVLBHYD). This immunoconjugate was shown to be largely aggregate free and there was no loss of immunoreactivity postconjugation. When tested in vivo in a 3-day-established human squamous carcinoma nude mouse xenograft model, the PF1/D-DAVLBHYD conjugate eliminated tumor growth with three injections (days 3, 6, and 9) at 2 mg/kg Vinca content. Significant tumor suppression was also observed with 0.5 mg/kg conjugate doses. In contrast, free PF1/D antibody had minimal antitumor activity and no activity was seen with identical doses of a control non-tumor-binding IgG-DAVLBHYD conjugate. Together, these data demonstrate the specificity of the PF1/D-DAVLBHYD antitumor effects.  相似文献   
59.
60.
During the first 24 months of the Oregon Liver Transplantation Program, which began in October 1988, 94 patients were formally evaluated and 47 adults underwent 54 liver transplantations. Thirty-four percent of patients were veterans. The recipient operation lasted a mean of 7.4 hours (range: 4 to 16 hours). Veno-venous bypass was used routinely at first but selectively later (7 of the last 26 cases), resulting in reduced operating time. Hepatic artery reconstruction was end-to-end anastomosis in 52 cases and iliac conduit in 2. No arterial thrombosis occurred. Biliary reconstruction was choledochocholedochostomy in 83% and choledochojejunostomy in 17%. Biliary complications occurred in 28%. Operative mortality was 2%, and 1-year actual survival was 80%. Patients with hepatitis B fared worse, with four of six dying at a mean of 7.6 months. Overall, the median hospital stay was 30 days. Patients surviving more than 3 months had a mean Karnofsky score of 82%. No significant difference in outcome was noted in patients receiving prophylactic OKT3 monoclonal antibody (used in 45%) versus conventional immunosuppressive therapy. Overall, allograft rejection occurred in 55% of patients. Retransplantation was required in seven patients, three for primary graft nonfunction, two for uncontrolled rejection during induction therapy with OKT3, and two for graft failure secondary to recurrent hepatitis B.  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