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   714篇
  免费   44篇
  国内免费   2篇
耳鼻咽喉   4篇
儿科学   40篇
妇产科学   20篇
基础医学   72篇
口腔科学   32篇
临床医学   61篇
内科学   132篇
皮肤病学   12篇
神经病学   30篇
特种医学   45篇
外科学   71篇
综合类   52篇
预防医学   28篇
眼科学   83篇
药学   35篇
肿瘤学   43篇
  2023年   4篇
  2022年   14篇
  2021年   21篇
  2020年   9篇
  2019年   13篇
  2018年   23篇
  2017年   17篇
  2016年   20篇
  2015年   26篇
  2014年   21篇
  2013年   26篇
  2012年   34篇
  2011年   33篇
  2010年   35篇
  2009年   26篇
  2008年   29篇
  2007年   28篇
  2006年   29篇
  2005年   25篇
  2004年   27篇
  2003年   21篇
  2002年   18篇
  2001年   12篇
  2000年   13篇
  1999年   12篇
  1998年   22篇
  1997年   20篇
  1996年   17篇
  1995年   15篇
  1994年   12篇
  1993年   8篇
  1992年   7篇
  1991年   12篇
  1990年   9篇
  1989年   8篇
  1988年   6篇
  1987年   10篇
  1986年   5篇
  1985年   11篇
  1984年   6篇
  1983年   8篇
  1982年   3篇
  1980年   4篇
  1979年   5篇
  1978年   9篇
  1977年   4篇
  1976年   7篇
  1975年   4篇
  1973年   2篇
  1971年   2篇
排序方式: 共有760条查询结果,搜索用时 15 毫秒
1.
2.
3.
Tumor vascular signals in renal masses: detection with Doppler US   总被引:3,自引:0,他引:3  
Ramos  IM; Taylor  KJ; Kier  R; Burns  PN; Snower  DP; Carter  D 《Radiology》1988,168(3):633-637
The vascularity of 49 renal masses (26 malignant and 23 benign lesions) was investigated with duplex Doppler ultrasound. Doppler signals obtained at the margins of renal masses were defined as "tumor signals" when the Doppler-shifted frequency of the lesion exceeded the frequency shift in the ipsilateral main renal artery. These exceeded 2.5 kHz with a 3-MHz insonating frequency. Among the 26 renal masses that subsequently proved to be malignant, tumor signals were obtained in 15 of 18 (83%) untreated renal cell carcinomas, in three of four Wilms tumors, and in two patients with metastases to the kidney, but not in the one patient with lymphoma. None of the 23 benign renal masses demonstrated tumor signals. Tumor vascularity in malignant lesions gives rise to abnormal, high-velocity, Doppler-shifted signals that can help in the differential diagnosis of renal masses.  相似文献   
4.
5.
Molecular and chemical characteristics often provide complementary information in the differentiation of closely related organisms. The genus Brucella consists of a highly conserved group of organisms. Identification of the four species pathogenic in humans (Brucella melitensis, Brucella abortus, Brucella suis, and Brucella canis) is problematic for many clinical laboratories that depend primarily on serology and phenotypic characteristics to differentiate species. PCR amplification of the 16S-23S ribosomal DNA interspace region was evaluated for species-specific polymorphism. B. abortus, B. melitensis, B. suis, and B. canis produced identical PCR interspace profiles. However, these PCR products were unique to brucellae, allowing them to be readily distinguished from other gram-negative bacteria (including Bartonella spp. and Agrobacterium spp.). Carbohydrate profiles differentiated B. canis from the other three Brucella species due to the absence of the rare amino sugar quinovosamine in the three other species. PCR of the rRNA interspace region is useful in identification of the genus Brucella, while carbohydrate profiling is capable of differentiating B. canis from the other Brucella species.  相似文献   
6.
7.
Thoracic spiracle length and its index was examined for their ability to discriminate two ecological variants, type form and mysorensis, of Anopheles stephensi in the adult stage. The type form is exclusively domestic in all seasons, whereas the mysorensis variant occupies the outdoor niche during monsoon and postmonsoon seasons, with spillover into domestic sites during summer ecological stress periods. A statistically significant co-relation was established between the ridge count of the egg and two adult measurements, the thoracic spiracle length, and the spiracular index. In An. stephensi type form, average spiracle length was 0.11-0.12 mm and average spiracular index was 8.09-9.23, whereas in mysorensis, the corresponding figures were 0.09-0.10 mm and 6.82-7.60. These parameters showed consistent variations in population of mosquitoes that emerged during monsoon and summer season. The thoracic lengths in both variants remained constant, and only spiracular lengths showed fluctuations in three seasonal populations. These measures provide discrimination of adult variants--identifications that are essential in malaria control programs.  相似文献   
8.
9.
Purpose

Smoking during pregnancy may be linked to other problematic prenatal health behaviors in women. We examined interrelationships among prenatal smoking, prenatal health behaviors and mental health. The objective of this study was to examine factors that may contribute to variations in prenatal health practices among women who smoke during pregnancy.

Methods

Birth mothers from an adoption study (N?=?912) were interviewed about prenatal smoking, health behaviors, and mental health symptoms at 5 months postpartum.

Results

One-quarter of participants (N?=?222) reported smoking 6 or more cigarettes daily for at least 1 trimester. For mothers who smoked more than 6 cigarettes daily, higher levels of antisocial behaviors (β?=????.14, p?=?.03) and depressive symptoms (β?=????.17, p?=?.03) were associated with less frequent prenatal folate use; antisocial behaviors and depressive symptoms were not associated for prenatal folate use among women who did not smoke more than 6 cigarettes daily. For mothers who did not smoke more than 6 cigarettes daily, more depressive symptoms were associated with fewer prenatal care visits (β?=?.12, p?=?.01). Antisocial behaviors and anxiety symptoms were not associated with prenatal care visits in either group of mothers.

Conclusions for Practice

Maternal antisocial behaviors and depressive symptoms during pregnancy may be markers for poorer adherence to recommendations for folate supplementation among women who smoke 6 or more cigarettes daily during pregnancy, independent of adequacy of prenatal care.

  相似文献   
10.
Taking a patient-oriented approach to developing lifestyle interventions includes incorporating the patient into the program’s design, delivery, and evaluation. This commentary assumes that a patient-oriented approach has not yet been implemented and tested in exercise-based interventions designed for pregnant women. We outline and define a patient-oriented approach to conduct exercise-based research and review previous physical activity interventions designed for pregnant women to determine whether a patient-oriented approach was applied. In addition, pregnant women living with obesity may have unique barriers to engaging in prenatal exercise interventions that have not been previously addressed, such as having experienced weight stigma before pregnancy in healthcare and fitness settings. We propose suggestions for future trials to effectively take a patient-oriented approach when designing and implementing prenatal exercise interventions to address patient-informed barriers and incorporate suggested facilitators for physical activity. Given that prenatal activity levels are low and pregnant women may have unique barriers to engaging in exercise interventions, a patient-oriented approach may be an effective strategy to improve inclusivity and equity and, as a result, increase uptake and adherence to the intervention.  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