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   62452篇
  免费   4660篇
  国内免费   1852篇
耳鼻咽喉   831篇
儿科学   1354篇
妇产科学   843篇
基础医学   6251篇
口腔科学   1149篇
临床医学   6824篇
内科学   9199篇
皮肤病学   2000篇
神经病学   4364篇
特种医学   2495篇
外国民族医学   5篇
外科学   3666篇
综合类   8328篇
现状与发展   4篇
一般理论   2篇
预防医学   6742篇
眼科学   893篇
药学   8712篇
  70篇
中国医学   3229篇
肿瘤学   2003篇
  2024年   144篇
  2023年   846篇
  2022年   1638篇
  2021年   2424篇
  2020年   2174篇
  2019年   2004篇
  2018年   2104篇
  2017年   2090篇
  2016年   1971篇
  2015年   2124篇
  2014年   3932篇
  2013年   4300篇
  2012年   3766篇
  2011年   3989篇
  2010年   3310篇
  2009年   3001篇
  2008年   2991篇
  2007年   3056篇
  2006年   2678篇
  2005年   2346篇
  2004年   1970篇
  2003年   1727篇
  2002年   1458篇
  2001年   1228篇
  2000年   1073篇
  1999年   1044篇
  1998年   811篇
  1997年   787篇
  1996年   715篇
  1995年   700篇
  1994年   649篇
  1993年   513篇
  1992年   555篇
  1991年   514篇
  1990年   458篇
  1989年   456篇
  1988年   419篇
  1987年   377篇
  1986年   321篇
  1985年   375篇
  1984年   309篇
  1983年   258篇
  1982年   262篇
  1981年   234篇
  1980年   196篇
  1979年   136篇
  1978年   111篇
  1977年   93篇
  1976年   80篇
  1975年   55篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
目的 观察中药干预对术后食管癌患者的生活质量及生存时间的影响.方法 选取180例经手术治疗的食管癌患者并依据知情同意的原则分为3个治疗组,分别是单纯化疗组、单纯中药组及中药+化疗组,每组各60例.采用生活质量核心问卷(QLQ-C30)和生存分析评估患者的生存质量和生存时间.结果 中药组、中药+化疗组和化疗组患者的临床症状及身体功能经干预均有一定改善,但总体而言,化疗+中药组的改善效果最佳,与另2组比较差异有统计学意义(P<0.05);化疗+中药组及单纯中药组患者经干预后,机体的免疫水平改善,而化疗组患者的免疫状况下降;化疗组患者的生存时间为(27.21±3.55)个月,中药组患者的生存时间为(28.56±4.19)个月,化疗+中药组患者的生存时间为(34.58±3.24)个月;经Log-Rank检验,3组差异有统计学意义(χ2=5.698,P=0.037).结论 食管癌患者术后服用中药,其生活质量、免疫状况、生存时间均明显改善,可在临床推广中药+化疗的综合干预方案.  相似文献   
992.
Several functional MR imaging studies evaluating the lateralisation of linguistic functions in patients who underwent Wada testing have been reported. There is extensive variance in the Laterality index (LI) calculation across the studies, and the optimal calculation method remains unclear. We attempted to calculate the LI in different ways in the same subjects, in order to find the LI calculation method with the highest correlation to the Wada test. Fifteen patients (10 females, 5 males) suffering from medically intractable temporal lobe epilepsy (TLE) (12 left, 3 right) were admitted for the study. The patients underwent a standardized bilateral intracarotid short-acting barbiturate test. Language testing included spontaneous speech, oral comprehension, reading, object and picture naming, and repetition. All the tasks were scored separately in order to increase the possibility of correlation between Wada and LI. A silent phonemic verbal fluency task (VFT) was used as a language paradigm for functional measurement. Regions of interest (ROIs), with a known association with language function (Broca’s area, the lateral prefrontal cortex, etc.), were defined. First, the LIs were calculated from the ROIs using a previously reported method (simple suprathreshold count). Next, we used several new methods of LI calculation (t–weighting of voxels, methods independent of the choice of the statistical threshold, etc.) The most significant correlation with Wada was proven in the LIs that were evaluated from Broca’s area (up to R = 0.94, P = 1 × 10−7). However, the new LI calculation methods used in the present study did not produce a statistically significant benefit in comparison to previously reported methods.  相似文献   
993.
The serial reaction time task (SRTT) is a well-established experimental tool to study cognitive and neural mechanisms of sequential performance in humans. We have recently developed a rodent version of the human serial reaction time task, in which rats have to respond to visual stimuli by nose-poking into one of four spatial locations in order to obtain food reward. In this task, rats display superior performance under sequential as compared to random conditions of stimulus presentation. Specifically, the subjects are able to profit from sequential regularities in terms of faster reaction times and higher response accuracy. Here, we studied the effects of violating a single stimulus in rats, which had been intensively trained under sequential conditions, and we asked whether these subjects, when confronted with sequence violations, still attend to the actual stimulus order (that is, show correct responses), or whether their behavior has become fully automated (leading to specific incorrect responses to violated stimulus positions). In two independent experiments using partly differing instrumental set-ups, we found that the responses to non-cued violations of single stimulus positions were mostly correct, that is, the animals were apparently attending to the stimuli. Nevertheless, these reaction times were slowed, which probably reflects cognitive resources necessary to respond correctly to the unexpected irregularities. When quantifying the minority of responses, which were incorrect, we found that most of them were directed to the position, where the stimulus would have appeared if the sequence had not been violated. These responses were faster than the correct ones (to the violated stimulus), which indicates that sequential responding had become partly automated. Together, our data show that both, attention and skill play a role for sequential performance in our SRT task, and that they can be dissected by quantification of specific response types. In future work, the neural correlates underlying these functional mechanisms will have to be addressed.  相似文献   
994.
This study focused on the evaluation of anticonvulsant properties of isonicotinic acid benzylamide (iso-Nic-BZA) in numerous experimental seizure models (maximal electroshock [MES]-, bicuculline [BIC]-, pentylenetetrazole [PTZ]-, pilocarpine [PILO]-, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid [AMPA]-, kainic acid [KA]- and N-methyl-d-aspartic acid [NMDA]-induced seizures). Moreover, acute adverse-effect profile of the agent with respect to impairment of motor coordination was assessed in animals subjected to the chimney test. The evaluation of time-course and dose-response relationships for iso-Nic-BZA provided evidence that the compound produced the peak to maximum antielectroshock action and acute adverse effects at 5min after its systemic (i.p.) administration. Iso-Nic-BZA exerted a clear-cut anticonvulsant action against maximal electroshock-induced seizures in mice and its ED(50) value was 70.6 (56.4-88.4)mg/kg. The assessment of acute adverse effects in the chimney test revealed that the agent produced acute neurotoxic effects and its TD(50) value was 135.6 (108.8-169.0)mg/kg. Additionally, iso-Nic-BZA showed the anticonvulsant activity in numerous chemically-induced seizures (AMPA-, BIC-, KA-, and PTZ-evoked clonic convulsions), remaining virtually ineffective (at doses up to 200mg/kg) in PILO- and NMDA-induced seizures in mice. Based on this study, one can conclude that iso-Nic-BZA due to the short time to peak of its maximum anticonvulsant effects (5min after its i.p. administration), deserves more attention as a potential antiepileptic drug for patients in status epilepticus.  相似文献   
995.
Congenital stationary night blindess-2 (incomplete congenital stationary night blindness (iCSNB) or CSNB-2) is a nonprogressive, X-linked retinal disease which can lead to clinical symptoms such as myopia, hyperopia, nystagmus, strabismus, decreased visual acuity, and impaired scotopic vision. These clinical manifestations are linked to mutations found in the CACNA1F gene which encodes for the Ca(v)1.4 voltage-gated calcium channel. To better understand the physiological effects of these mutations, three missense mutants, F742C, G1007R and R1049W, previously shown to be mutated in patients with CSNB-2, were transiently expressed in human embryonic kidney (HEK) tsA-201 cells and characterized using whole-cell patch clamp. The G1007R mutation is located in transmembrane segment 5 (S5) of domain III and R1049W is located in the extracellular linker between S5 and the P-loop of domain III. Both mutants produced full length proteins that targeted to the membrane but did not support ionic currents. In 20 mM Ba(2+), F742C (S6 domain II) produced a approximately 21 mV hyperpolarizing shift in half activation potential (V(a[1/2])) and a approximately 23 mV hyperpolarizing shift in half inactivation potential (V(h[1/2])). Additionally, F742C displayed slower inactivation kinetics and a smaller whole cell conductance (G(max)). In physiological 2 mM Ca(2+), F742C produced a approximately 19 mV hyperpolarizing shift in V(a[1/2]). These findings suggest that the pathology of CSNB-2 in patients with these missense mutations in the Ca(v)1.4 calcium channel is the result in either a gain of function (F742C) or a loss of function (G1007R, R1049W).  相似文献   
996.
Locked nucleic acids (LNA) based real time PCR was used in particular situations where there are difficulties in primer design due to sequence complexity. In this study a new real time RT-PCR assay was developed using LNA modified primers and LNA molecular beacon probes to monitor hepatitis C virus (HCV) viral load in plasma and serum samples. The technique did not suffer from an heterogeneity of the HCV genome and, in addition, an internal RNA control was amplified in the same reaction tube with different short primers and beacon probe. Due to the short consensus LNA primers length, the PCR efficiency was close to 100% with no formation of hairpin loop structures. In summary a new LNA molecular beacon based real time RT-PCR assay was used successfully to measure quantitatively the total level of HCV RNA in both experimental and clinical specimens. The high sensitivity (50 IU/ml), the wide range of genotype detection, increased specificity and robustness obtained with this test are particularly useful for screening large number of specimens and measuring viral loads to monitor the progress of the disease.  相似文献   
997.
The Concealed Information Polygraph Test has been advocated as the preferred method for the physiological detection of deception. In this study, we further examined the validity of the Concealed Information Test in antisocial individuals. Physiological responding to concealed information was assessed in 48 male prisoners, and compared with responding in 31 male community volunteers. Based upon the association between antisociality and autonomic hyporesponsivity, lower detection rates were expected in the prisoners. Participants were questioned on five personally significant items (e.g., day of birth), instructed to deny recognition of this information, and promised a financial reward when able to hide recognition. Prisoners showed reduced autonomic reactivity in comparison to the community volunteers. This hyporesponsivity had little impact on the sensitivity of the Concealed Information Test. Detection efficiency in the prisoners was significantly above chance (d=2.67; a=0.82; 79%), and did not differ significantly from that obtained in the community volunteers (d=3.04; a=0.85; 87%). The present data support the validity of the Concealed Information Test in criminal populations.  相似文献   
998.
Ependymomas usually develop from neuroectodermal organs. Here, we present an ependymoma arising from the pelvic cavity. A 27-year-old Korean female was admitted to the hospital with a sensation of abdominal fullness. Imaging studies revealed a huge heterogeneous nodular mass in the pelvis and lower abdomen. Laparotomy showed that two large masses with multiple nodules were located between the uterus and rectum and uterus and bladder, respectively. Histologically, the tumor was characterized by compact columnar neoplastic cells divided by fibrovascular septae. The neoplastic cells formed true ependymal rosettes and perivascular pseudorosettes. Immunohistochemical staining showed a strong positive reaction for glial fibrillary acidic protein (GFAP) and vimentin and a partial positive reaction for S100 and EMA. The tumor was thus diagnosed as an ependymoma arising from the pelvic cavity. The patient was treated with a debulking operation and chemotherapy based upon the in vitro chemosensitivity test results. The patient was free of cancer for 4 years following surgery. This is a rare case of extraneural ependymoma for which an in vitro chemosensitivity test was critical in determining the multidisciplinary approach for treatment.  相似文献   
999.
1000.
Motor vehicle crashes are the leading cause of death in the United States for people ages 3-33, and rollover crashes have a higher fatality rate than any other crash mode. At the request and under the sponsorship of Ford Motor Company, Autoliv conducted a series of dynamic rollover tests on Ford Explorer sport utility vehicles (SUV) during 1998 and 1999. Data from those tests were made available to the public and were analyzed in this study to investigate the magnitude of and the temporal relationship between roof deformation, lap-shoulder seat belt loads, and restrained anthropometric test dummy (ATD) neck loads. During each of the three FMVSS 208 dolly rollover tests of Ford Explorer SUVs, the far-side, passenger ATDs exhibited peak neck compression and flexion loads, which indicated a probable spinal column injury in all three tests. In those same tests, the near-side, driver ATD neck loads never predicted a potential injury. In all three tests, objective roof/pillar deformation occurred prior to the occurrence of peak neck loads (F ( z ), M ( y )) for far-side, passenger ATDs, and peak neck loads were predictive of probable spinal column injury. The production lap and shoulder seat belts in the SUVs, which restrained both driver and passenger ATDs, consistently allowed ATD head contact with the roof while the roof was contacting the ground during this 1000 ms test series. Local peak neck forces and moments were noted each time the far-side, passenger ATD head contacted ("dived into") the roof while the roof was in contact with the ground; however, the magnitude of these local peaks was only 2-13% of peak neck loads in all three tests. "Diving-type" neck loads were not predictive of injury for either driver or passenger ATD in any of the three tests.  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