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   16004篇
  免费   763篇
  国内免费   106篇
耳鼻咽喉   263篇
儿科学   330篇
妇产科学   176篇
基础医学   1998篇
口腔科学   432篇
临床医学   1085篇
内科学   3968篇
皮肤病学   279篇
神经病学   1176篇
特种医学   756篇
外科学   2598篇
综合类   77篇
预防医学   509篇
眼科学   467篇
药学   1149篇
中国医学   29篇
肿瘤学   1581篇
  2023年   85篇
  2022年   149篇
  2021年   339篇
  2020年   205篇
  2019年   257篇
  2018年   331篇
  2017年   262篇
  2016年   314篇
  2015年   319篇
  2014年   394篇
  2013年   493篇
  2012年   853篇
  2011年   925篇
  2010年   525篇
  2009年   419篇
  2008年   780篇
  2007年   818篇
  2006年   871篇
  2005年   849篇
  2004年   791篇
  2003年   736篇
  2002年   771篇
  2001年   437篇
  2000年   490篇
  1999年   468篇
  1998年   220篇
  1997年   177篇
  1996年   163篇
  1995年   151篇
  1994年   98篇
  1993年   91篇
  1992年   243篇
  1991年   257篇
  1990年   260篇
  1989年   268篇
  1988年   256篇
  1987年   251篇
  1986年   207篇
  1985年   197篇
  1984年   160篇
  1983年   105篇
  1982年   59篇
  1981年   66篇
  1980年   46篇
  1979年   96篇
  1976年   48篇
  1974年   45篇
  1972年   62篇
  1970年   48篇
  1969年   59篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Background: Lay belief systems about the malleability of human attributes have been shown to impact behavior change in multiple domains. Addiction mindset—i.e., beliefs about the permanence (vs. malleability) of addiction — may affect cigarette smokers’ ability to quit, but this has never been examined. Objectives: The aims of the present research were to develop a measure of addiction mindset (study 1) and examine its associations with various psychological aspects of quitting smoking (study 2). Methods: In Study 1, using factor analysis of current smokers’ and nonsmokers’ (n?=?600) responses to 22 items designed to measure addiction mindset, we developed a reliable six-item Addiction Mindset Scale (AMS). In Study 2, adult smokers (n?=?200) completed the AMS, and measures of a number of psychological processes related to smoking. Results: Higher scores on the AMS, indicative of the belief that addiction is malleable (referred to as a growth mindset), were positively and significantly associated with greater motivation to quit, greater commitment to quitting, greater self-efficacy to abstain, less attribution of failure to lack of ability to change addiction, and fewer self-reported barriers to cessation (all p’s < .05). Conclusions: The results of this study show a relationship between the beliefs about the permanence of addiction and psychological processes relevant to quitting smoking. The findings underscore the potential of future research exploring how addiction mindsets relate to successful smoking cessation as well as other types of addictive behavior and how they can be applied to change people’s behavior.  相似文献   
2.
3.
4.
PURPOSE: The purpose of this study was to assess the relationship between the amount of scirrhous component in invasive ductal carcinoma and its MR characteristics. MATERIALS AND METHODS: We retrospectively reviewed 71 consecutive patients with invasive ductal carcinoma smaller than 25 mm (average, 16.6 mm) in diameter. The scirrhous component was defined as invasive foci in small clusters of cancer cells showing desmoplasia. Invasive ductal carcinoma was subclassified into 3 groups in accordance with the amount of the scirrhous component (scirrhous component degree; SCD): SCD I (scirrhous component less than 20%), SCD II (intermediate), and SCD III (more than 80%). Dynamic magnetic resonance (MR) imaging was performed using volumetric interpolated sequence. Prior to dynamic study, T2*-weighted first-pass perfusion images were obtained before, during, and after bolus injection of 0.1 mmol Gd-DTPA/kg. RESULTS: Twenty-eight lesions were classified as SCD I, 14 as SCD II, and 29 as SCD III. Mass margin and signal intensity loss in the perfusion study were significantly different among the 3 SCD groups (P<0.001). The kinetic patterns were significantly different among the 3 SCD groups (P=0.04), and between SCD I/II and SCD III (P=0.03). The presence of enhancing internal septations was significantly different between SCD I/II and SCD III carcinomas (P=0.05). Central enhancement was only observed in SCD I carcinoma (4%; 3/71). CONCLUSION: The histological predominance of the scirrhous component in invasive ductal carcinoma may be one explanation for the differences in morphologic and kinetic patterns on MR imaging.  相似文献   
5.
We examined stochastic resonance with a differential coding scheme using a multilayer feedforward neural network which is composed of intra-layer connections. We show that the network, with random synaptic connections in each layer, encodes an input signal into a spike coherence that represents temporal differences among the inputs. We also demonstrate that both internal and external noise enhance the detection of weak signals. Finally, we discuss how the feedforward network with intra-layer random connections is similar to a membrane in its sensitivity to and amplification of a change in stimulus and suggest that the intensity of internal noise may be tuned in a real brain.  相似文献   
6.
Background During anterior cruciate ligament (ACL) reconstruction, placement of the reconstructed ligament affects the clinical results. To accomplish accurate and reproducible placement of the tibial bone tunnel, we employed a fluoroscopic navigation system for endoscopic ACL reconstruction. In this study, preciseness of the tibial tunnel placement was evaluated, and the advantages and disadvantages of this navigation system for endoscopic ACL reconstruction are discussed. Methods Altogether, 16 knees of 16 patients who had undergone ACL reconstruction using this system (navi group) were evaluated regarding the positioning of the tibial tunnel against Blumensaat's line using X-p and the route of the graft by magnetic resonance imaging (MRI). Another 16 knees of 16 patients who underwent endoscopic ACL reconstruction without the navigation system were the controls (control group). Results At the 1-year follow-up, maximally extended lateral knee X-p revealed that the anterior edge of the tibial tunnel and Blumensaat's line were almost aligned and that roof impingement was avoided; the T2-weighted MR images showed that the graft was placed close to and parallel to the intercondylar roof in all the knees of the navi group. The ratio of the distance between Blumensaat's line and the anterior edge of the tibial tunnel at the level of the tibial plateau to the anteroposterior width in fully extended true lateral radiographs was 2.7% ± 3.4% in the navi group and 8.4% ± 7.4% in the control group. Conclusions The computer-assisted fluoroscopic navigation system improves accuracy and decreases dispersion of the tibial tunnel placement against Blumensaat's line in single-bundle ACL reconstruction. This innovative device renders the reconstruction procedure more reliable, eliminating the problem of skeletal variation among patients. However, the function of this navigation system for femoral tunnel placement is insufficient at present. Further refinement of the system is necessary, and the method of application requires improvement.  相似文献   
7.
We report the case of a 4-year-old girl who had quadricuspid aortic valve regurgitation with tetralogy of Fallot and pulmonary atresia. This combination is very uncommon. Aortic valve replacement was performed successfully due to aortic regurgitation which had progressed one year after the total repair. The dilated aortic annulus plus quadricuspid aortic valve may result in progressive aortic regurgitation for a short period.  相似文献   
8.
To elucidate the effects of teeth on muscle fibers in the tongue during the developmental process, we examined the expression of muscle contractile proteins and the genes for those proteins in normal mice and microphthalmic (mi/mi) mice with impaired tooth eruption. The mice were observed during the growth period, including weaning, which is when feeding movements undergo major changes. Expression of the myosin heavy chain (MyHC)-2a protein, whose contraction speed is relatively slow, disappeared after weaning in normal mice, while it remained in high concentrations even after weaning in mi/mi mice. The presence of MyHC-2a after weaning in mice with no tooth eruption was attributed to a compensation for lack of proper masticatory function and sucking-like movements, as MyHC-2a is necessary for these movements.  相似文献   
9.
Experiments were performed on spinalized rats, transected at the Cl level. The intravenous administration of TRH and its analog YM-14673 (N alpha-[(S)-4-oxo-2-azetidinyl) carbonyl]-L-histidyl-L-prolinamide dehydrate) produced marked increases in the amplitude of mono- and polysynaptic reflex potentials and those of the withdrawal flexor reflexes. The effects of YM-14673 were stronger and longer-lasting than those of TRH. The stimulant action of TRH and YM-14673 on the flexor reflexes was not antagonized by prazosin, chlorpromazine, haloperidol or cyproheptadine, suggesting no involvement of the release of catecholamines or serotonin in the stimulant effects of TRH and its analog. Therefore, YM-14673 may be beneficial for the treatment of several spinal motor neuron diseases.  相似文献   
10.
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