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   8932篇
  免费   917篇
  国内免费   15篇
耳鼻咽喉   75篇
儿科学   304篇
妇产科学   140篇
基础医学   1193篇
口腔科学   322篇
临床医学   1101篇
内科学   1811篇
皮肤病学   117篇
神经病学   616篇
特种医学   446篇
外科学   1264篇
综合类   243篇
一般理论   6篇
预防医学   844篇
眼科学   200篇
药学   661篇
  1篇
中国医学   1篇
肿瘤学   519篇
  2021年   91篇
  2020年   66篇
  2019年   109篇
  2018年   129篇
  2017年   131篇
  2016年   129篇
  2015年   151篇
  2014年   151篇
  2013年   257篇
  2012年   370篇
  2011年   396篇
  2010年   266篇
  2009年   240篇
  2008年   334篇
  2007年   357篇
  2006年   355篇
  2005年   388篇
  2004年   311篇
  2003年   363篇
  2002年   324篇
  2001年   262篇
  2000年   290篇
  1999年   253篇
  1998年   174篇
  1997年   186篇
  1996年   175篇
  1995年   146篇
  1994年   150篇
  1993年   128篇
  1992年   214篇
  1991年   195篇
  1990年   173篇
  1989年   199篇
  1988年   185篇
  1987年   191篇
  1986年   156篇
  1985年   188篇
  1984年   135篇
  1983年   123篇
  1982年   89篇
  1981年   88篇
  1980年   68篇
  1979年   114篇
  1978年   75篇
  1977年   82篇
  1976年   67篇
  1973年   86篇
  1972年   75篇
  1971年   74篇
  1970年   62篇
排序方式: 共有9864条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
The MMPI was administered during the patient-perceived best time of the menstrual cycle and during the patient-perceived worst time of the cycle in order to examine the stability of MMPI profile configurations. Subjects were 214 women who were referred to two metropolitan outpatient premenstrual syndrome (PMS) clinics for moderate to severe premenstrual complaints. This sample was selected from 1,849 intake files after screening by strict selection criteria for PMS. The results indicate that there are wide fluctuations in profile patterns between the best and worst times of the menstrual cycle for a large number of patients. Caution in using the MMPI is strongly advised.  相似文献   
5.
6.
Summary Cytosine arabinsodie (ara-C) and etoposide (VP-16) display synergy in the laboratory. Twenty-six patients participated in a phase I study of high-dose ara-C in combination with VP-16. The dose of VP-16 was held constant at 50 mg/m2 as an intermittent infusion over 33 h; escalating doses of ara-C were given as infusions during hours 9–12 and 21–24. Myelosuppression was the dose-limiting toxicity and occurred with doses considerably less than those expected from studies of the two drugs as single agents. The suggested initial doses for phase II trials with this schedule are 750 mg/m2×2 doses of ara-C and 50 mg/m2 of VP-16. Nonhematologic toxicity was minimal; therefore, further dose escalation is feasible in patients in whom myelosuppression is acceptable.Supported in part by grants from the National Cancer Institute (CA-12197 and CA-09422) and the American Cancer Society CF-85-182  相似文献   
7.
Power spectral and discriminant analysis techniques were used to compare EEG records obtained at term and at 3 months past term from 5 groups of varying risk and developmental outcome. The groups were: healthy full-terms; healthy pre-terms with normal outcomes; sick pre-terms with normal outcomes; sick pre-terms with delayed development; sick pre-terms with later neurological problems. The EEG samples recorded at term were identified as belonging to the correct subject group at 52-70% accuracy, 20% being chance for 5 groups. The accuracy varied with the 4 classes of EEG patterns used. The individual subjects were also classified into their correct groups with few exceptions. Similar success was obtained with EEG samples selected from recording at 3 months past term. The predominant power spectral discriminating features were changes in intra- and inter-hemispheric coherence, and increased power, particularly in the middle and higher frequency range. Thus, computer analyses of EEG samples, using features not readily identified visually, differentiated risk from non-risk infants and also differentiated infants with substantial neonatal medical complications who have good or poor developmental outcomes.  相似文献   
8.
Coccidiosis of chickens, caused by species of Eimeria (Protozoa, Apicomplexa), is an intestinal disease of major economic importance worldwide. In the present study, the reproductive characteristics of a precocious line (designated E. tenella Rt3+15) from Australia were investigated in chicken embryos and the implications of the findings briefly discussed.  相似文献   
9.
To investigate the mechanism of CD4(+) T-cell help during the activation and differentiation of directly alloreactive CD8(+) T cells, we examined the development of obliterative airways disease (OAD) following transplantation of airways into fully mismatched recipient mice deficient in CD4(+) T cells. BALB/c trachea allografts became fibrosed significantly less frequently in B6 CD4(-/-) recipients as compared to wildtype controls. Furthermore, class I-directed cytotoxicity failed to develop in the absence of CD4(+) T cells. The infiltration of graft tissue by primed L(d)-specific directly alloreactive 2C CD8(+) T cells was not found to depend on the presence of CD4(+) T cells. Nevertheless, graft-infiltrating 2C CD8(+) T cells failed to express CD69 and granzyme B when CD4(+) T-cell help was unavailable. Importantly, reconstitution of B6 CD4(-/-) recipient mice with graft peptide-specific TCR-Tg CD4(+) T cells (OT-II or TEa) capable of recognizing antigen only on recipient APC allowed for full expression of CD69 and granzyme B by the directly alloreactive CD8(+) T cells and restored the capacity of recipients to reject their allografts. These results demonstrate that indirectly alloreactive CD4(+) T cells ensure the optimal activation and differentiation of graft-infiltrating directly alloreactive CD8(+) T cells independent of donor APC recognition.  相似文献   
10.
Nuclear magnetic resonance (NMR) spectroscopy has been reported as an alternative method for quantitating deuterium oxide concentrations in the evaluation of total-body-water in humans. However, the presence of dissolved plasma proteins results in an underestimation of deuterium NMR (2H-NMR) intensity ratios, thereby causing an overestimation (5-6%) of total-body-water (TBW) values determined from nonsublimed patient plasma samples. We demonstrate that plasma samples must be corrected for the volume percentage of water in plasma. Correction of initial 2H-NMR intensity ratios with a factor of 0.93 results in intensity ratios comparable to those determined from plasma samples subjected to vacuum sublimation to remove all plasma solutes.  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