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   6654篇
  免费   525篇
  国内免费   12篇
耳鼻咽喉   72篇
儿科学   232篇
妇产科学   182篇
基础医学   932篇
口腔科学   145篇
临床医学   668篇
内科学   1327篇
皮肤病学   123篇
神经病学   885篇
特种医学   377篇
外国民族医学   1篇
外科学   961篇
综合类   120篇
一般理论   1篇
预防医学   397篇
眼科学   44篇
药学   269篇
中国医学   6篇
肿瘤学   449篇
  2021年   96篇
  2020年   52篇
  2019年   68篇
  2018年   95篇
  2017年   65篇
  2016年   80篇
  2015年   130篇
  2014年   175篇
  2013年   207篇
  2012年   307篇
  2011年   324篇
  2010年   165篇
  2009年   152篇
  2008年   305篇
  2007年   343篇
  2006年   295篇
  2005年   347篇
  2004年   330篇
  2003年   337篇
  2002年   319篇
  2001年   198篇
  2000年   198篇
  1999年   157篇
  1998年   119篇
  1997年   90篇
  1996年   68篇
  1995年   60篇
  1994年   50篇
  1993年   41篇
  1992年   113篇
  1991年   110篇
  1990年   103篇
  1989年   86篇
  1988年   116篇
  1987年   117篇
  1986年   107篇
  1985年   86篇
  1984年   85篇
  1983年   80篇
  1982年   55篇
  1981年   46篇
  1980年   49篇
  1979年   65篇
  1978年   65篇
  1977年   57篇
  1976年   49篇
  1974年   44篇
  1973年   47篇
  1972年   55篇
  1969年   44篇
排序方式: 共有7191条查询结果,搜索用时 15 毫秒
1.
PurposeThe aim of this study was to determine how female age at the end of the reproductive spectrum effects success of natural cycle intrauterine insemination (IUI) or IUI in combination with ovarian stimulation.MethodsWe performed a retrospective cohort study of women 43 years of age and older at the time of IUI in a single academic fertility center between January 2011 and March 2018. Primary outcomes were both pregnancies and live births per cycle of IUI. Data are presented as percentage or mean ± SD. Fisher exact and chi-squared analyses were performed.ResultsThere were 9334 IUI cycles conducted during the study period. Of these cycles, 325 IUIs (3.5%) were for women aged 43 years and over at the time of insemination (43.6 ± 0.8, range 43 to 47 years). Analysis of these 325 IUI cycles revealed 5 biochemical pregnancies (1.5%) and only 1 live birth (0.3%). The pregnancy rate did not differ between IUIs using donor sperm (N = 1/49, 2.0%) compared to IUIs with partner sperm (N = 4/276, 1.4%). The pregnancy rate did not differ between IUIs with gonadotropins (N = 2/211, 0.9%), clomiphene or letrozole (N = 2/78, 2.6%), or natural cycle (N = 1/36, 2.8%).ConclusionsThe use of intrauterine inseminations in women 43 years of age and older is an ineffective treatment strategy. This is irrespective of the use of ovarian stimulation or donor sperm. Costly gonadotropin injections did not increase the chance of pregnancy nor did oral medication when compared to natural cycle IUIs.  相似文献   
2.
ObjectiveClinical specialty societies recommend long-acting reversible contraceptives (LARCs) as first-line contraception for adolescent women. We evaluated whether a combined educational and process improvement intervention enhanced LARC placement in primary care within an integrated health care system.MethodsThe intervention included journal clubs, live continuing education, point-of-care guidelines, and new patient materials. We conducted a retrospective cohort study across 3 time periods: baseline (January 2013?September 2015), early implementation (October 2015–March 2016), and full implementation (April 2016–June 2017). The primary outcome was the proportion of LARCs placed by primary care clinicians among women aged 13 to 18 years compared with gynecology clinicians.ResultsKaiser Foundation Health Plan of Colorado cared for approximately 20,000 women aged 13 to 18 years in each calendar quarter between 2013 and 2017. Overall, LARC placement increased from 7.0 per 1000 members per quarter at baseline to 13.0 per 1000 during the full intervention. Primary care clinicians placed 6.2% of all LARCs in 2013, increasing to 32.1% by 2017 (P < .001), including 45.5% of contraceptive implants. Clinicians who attended educational sessions were more likely to adopt LARCs than those who did not (17.9% vs 6.4% respectively, P = .009). Neither overall LARC placement rates (relative risk, 1.9; 95% confidence interval, 0.7?5.6) nor contraceptive implant rates (relative risk, 3.0; 95% confidence interval, 0.9?9.8) increased significantly in clinicians who attended educational activities.ConclusionsThis multimodal intervention was associated with increased LARC placement for adolescent women in primary care. The combination of education and process improvement is a promising strategy to promote clinician behavior change.  相似文献   
3.
Constitutional trisomy 21 is the most prominent predisposing factor to childhood leukemia, whereas the t(12;21)(p13;q22) with its molecular genetic counterpart, the TEL/AML1 fusion gene, is the most common acquired chromosomal rearrangement in childhood B-cell precursor (BCP) acute lymphoblastic leukemia (ALL). Thus, it was somewhat surprising that according to the currently available literature the incidence of TEL/AML1+ BCP ALL is extremely low in patients with Down syndrome (DS). To further investigate this issue in a population-based fashion, the authors retrospectively assessed the number of DS patients with a TEL/AML1+ ALL in two consecutive Austrian ALL multicenter trials. Accordingly, they were able to analyze 8 of 10 individuals with DS and a BCP ALL, including 2 who suffered from a TEL/AML1+ leukemia. Based on this observation we concluded that individuals with a constitutional trisomy 21 may have the similar likelihood to develop a TEL/AML1+ leukemia as BCP ALL patients without this specific predisposing factor.  相似文献   
4.
Zusammenfassung Dieser Artikel stellt eine Übersetzung der im Jahr 2006 herausgegebenen Empfehlungen zur Behandlung von Patienten mit spontaner intrazerebraler Blutung der Europäischen Schlaganfallinitiative (EUSI) für das Europäische Schlaganfall-Council (ESC), die Europäische Neurologische Gesellschaft (ENS) und die Europäische Förderation Neurologischer Gesellschaften (EFNS) dar.Diese EUSI-Empfehlungen werden von dem European Stroke Council (ESC), der European Neurological Society (ENS) und der European Federation of Neurological Societies (EFNS) unterstützt.  相似文献   
5.
6.
(1) The estrous cycle in the rat may be used to study recurrent changes in motor behaviors and motivation which are strongly related to cyclic hormonal and CNS changes. (2) The peak in motivated behaviors occurs during a sharply defined period on the night between proestrus and estrus and is evident in facilitated wheel-running, lordosis, and intracranial self-stimulation. (3) Behaviors without a clearly motivated character do not show an estrous cyclicity. (4) The estrous cyclic variation in intracranial self-stimulation was observed at a specific locus — the pars campacta of the substantia nigra. (5) A neurochemical link between sexually motivated behavior, wheel running and intracranial self-stimulation is suggested. This link is in part dopaminergic but is probably also activated by many other systems.  相似文献   
7.
A design technique (Control of Uncertain Systems with Bounded Inputs, Tarbouriech S, Garcia G, (Eds), Lecture Notes in Control and Information Sciences, vol. 227 , Springer: Berlin, 1997; 173–186) recently proposed for stabilization of a linear system with rate‐limited actuators is utilized to design feedback laws that cause the system output to track a desired command signal. This design technique combines two design techniques recently developed for linear systems with position limited actuators, piecewise‐linear LQ control (Automatica, 1994; 30 : 403–416) and low‐and‐high gain feedback (IEEE Trans. Automat. Control, 1996; 41 : 368–378), and hence takes advantage of both design techniques, while avoiding their disadvantages. In the case that only the output is available for feedback, the performance of the state feedback law is preserved by the use of a fast observer. An open‐loop exponentially unstable fighter aircraft is used to demonstrate the effectiveness of the proposed control design method. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
8.
9.
10.
OBJECTIVES: To assess the long-term mortality in patients with thrombosis of the vena cava, iliac and femoral veins. DESIGN: Registry study. MATERIALS: Between 1992 and 2000, 212 consecutive patients with acute pelvic vein thrombosis diagnosed by duplex sonography were examined by magnetic resonance imaging (MRI) to determine the most proximal extent of the thrombus. MRI revealed a thrombosis in the inferior vena cava in 46 patients (22%), in the iliac vein in 142 patients (67%), and in the femoral vein in 24 patients (11%). METHODS: The vital status of the patients was investigated in April 2004 using the Austrian National Registry and the Cause of Death Register. RESULTS: A total of 211 patients of the original 212 patients were monitored over a mean follow-up period of 91 months. Seventy-two of 211 patients (34%) had died. There was no significant difference in the long-term mortality, the survival period or the occurrence of fatal pulmonary embolism (PE) between previously diagnosed vena cava, iliac vein, or femoral vein thrombosis. CONCLUSIONS: Extension of a thrombus into the inferior caval vein in patients considered to have a pelvic vein thrombosis has no impact on long-term mortality or the development of fatal PE compared to those patients with thrombus limited to more distal veins.  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