全文获取类型
收费全文 | 8595篇 |
免费 | 721篇 |
国内免费 | 244篇 |
专业分类
耳鼻咽喉 | 67篇 |
儿科学 | 125篇 |
妇产科学 | 544篇 |
基础医学 | 981篇 |
口腔科学 | 282篇 |
临床医学 | 748篇 |
内科学 | 859篇 |
皮肤病学 | 110篇 |
神经病学 | 595篇 |
特种医学 | 293篇 |
外国民族医学 | 3篇 |
外科学 | 688篇 |
综合类 | 1439篇 |
预防医学 | 582篇 |
眼科学 | 237篇 |
药学 | 656篇 |
9篇 | |
中国医学 | 436篇 |
肿瘤学 | 906篇 |
出版年
2024年 | 28篇 |
2023年 | 137篇 |
2022年 | 246篇 |
2021年 | 358篇 |
2020年 | 291篇 |
2019年 | 205篇 |
2018年 | 219篇 |
2017年 | 276篇 |
2016年 | 302篇 |
2015年 | 262篇 |
2014年 | 498篇 |
2013年 | 518篇 |
2012年 | 520篇 |
2011年 | 512篇 |
2010年 | 443篇 |
2009年 | 432篇 |
2008年 | 426篇 |
2007年 | 396篇 |
2006年 | 417篇 |
2005年 | 314篇 |
2004年 | 277篇 |
2003年 | 221篇 |
2002年 | 181篇 |
2001年 | 186篇 |
2000年 | 131篇 |
1999年 | 132篇 |
1998年 | 124篇 |
1997年 | 141篇 |
1996年 | 81篇 |
1995年 | 102篇 |
1994年 | 90篇 |
1993年 | 88篇 |
1992年 | 84篇 |
1991年 | 59篇 |
1990年 | 83篇 |
1989年 | 67篇 |
1988年 | 70篇 |
1987年 | 46篇 |
1986年 | 44篇 |
1985年 | 83篇 |
1984年 | 71篇 |
1983年 | 42篇 |
1982年 | 58篇 |
1981年 | 61篇 |
1980年 | 53篇 |
1979年 | 42篇 |
1978年 | 37篇 |
1977年 | 25篇 |
1976年 | 34篇 |
1975年 | 15篇 |
排序方式: 共有9560条查询结果,搜索用时 15 毫秒
81.
The relationship between sensation seeking and the orienting reflex (OR) using skin conductance change is investigated in two experiments. In Experiment I, high sensation seekers gave a greater initial OR In novel visual stimuli while not differing in habituation on subsequent trials. In Experiment II. the paradigm was extended to include auditory as well as visual stimuli. Again, high sensation seekers were found to be more arousable with respect to initial ORs while not differing in habituation rates. The results suggest that sensation seekers may be characterized as having strong excitatory CNS processes. In Experiment II, anxiety (trait and state) was also related to the OR. There were no effects due to trait anxiety but state anxiety did yield significant differences. The more highly anxious (state) subjects had weaker initial ORs than lows in both novel tones, but not to repeated tones. The findings with state anxiety are consistent with findings by others using anxiety neurotics as subjects. 相似文献
82.
介绍了用图像处理及模式识别技术对显微细胞图像的自动分析和分类的方法,并针对医学图像分析中的难点,提出了基于归一化彩色空间和RGB,HSV彩色模型的分割方法:利用模式识别技术中关于特征向量空间聚类的方法实施真彩色分割.这种方式有效地利用了多维特征空间对于分割目标所提供的信息,使分割的准确性有了较大的提高,解决了图像分割过程中的单个细胞检出问题. 相似文献
83.
Paul A. Knepper Ralph K. Losey Jennifer A. Collins David G. McLone Hyman G. Weinstein Moira Breen 《Neurobiology of aging》1983,4(2):163-168
The glycosaminoglycan distribution patterns of the cerebrospinal fluid (CSF) outflow pathway, dura mater and cerebral cortex of young New Zealand red rabbits and 1-, 3- and 12-week-old C-57 mice were identified by analyses of the glycosaminoglycan moieties and by the use of zone electrophoresis. The glycosaminoglycans were identified by specific degradation procedures, i.e., hyaluronate lyase, chondroitin ABC lyase, endo-gb-D-galactosidase and nitrous acid treatment. The CSF outflow pathway and dura mater glycosaminoglycan components were primarily hyaluronic acid and chondroitin sulfatedermatan sulfate, whereas the cerebral cortex glycosaminoglycan components were hyaluronic acid, chondroitin sulfatedermatan sulfate, keratan sulfate and heparan sulfate. The glycosaminoglycan components of the dura mater and cerebral cortex decreased and those of the CSF outflow pathway increased as a function of age. These results demonstrate the feasibility of analyses of the CSF outflow pathway glycosaminoglycan components and suggest that topographical changes in the glycosaminoglycan distribution profiles may contribute to the pattern of cerebrospinal fluid outflow. 相似文献
84.
Khutoryan BM 《Neuroscience and behavioral physiology》2005,35(1):5-7
A quantitative assessment of the cellular elements present in the nuclei of the human cerebellum was performed using subjects aged 22-90 years. A series of horizontal sections of cerebellar nuclei was studied. stained with hematoxylin and eosin. The numbers of neurons and gliocytes per unit area were measured on sections, with subsequent calculation of their ratios (the glial index). These experiments showed that aging is associated with decreases in the content of neurons and increases in the content of gliocytes. The extent of these changes increases as ontogenesis proceeds. 相似文献
85.
Akao T Kurkin S Fukushima K 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2004,158(1):129-132
Clear vision of objects that move in depth toward or away from an observer requires vergence eye movements. The vergence system must interact with the vestibular system to maintain the object images on the foveae of both eyes during head movement. Previous studies have shown that training with sinusoidal vergence-vestibular interaction improves the frequency response of vergence eye movements during pitch rotation: vergence eye velocity gains increase and phase-lags decrease. To further understand the changes in eye movement responses in this adaptation, we examined latencies of vergence eye movements before and after vergence-vestibular training. Two head-stabilized Japanese monkeys were rewarded for tracking a target spot moving in depth that required vergence eye movements of 10°/s. This target motion was synchronized with pitch rotation at 20°/s. Both target and chair moved in a trapezoidal waveform interspersed with random inter-trial intervals. Before training, pitch rotation in complete darkness without a target did not induce vergence eye movements. Mean latencies of convergence and divergence eye movements induced by vergence target motion alone were 182 and 169 ms, respectively. After training, mean latencies of convergence and divergence eye movements to a target synchronized with pitch rotation shortened to 65 and 53 ms, and vergence eye velocity gains (relative to vergence target velocity) at the normal latencies were 0.68 and 1.53, respectively. Pitch rotation alone without a target induced vergence eye movements with similar latencies after training. These results indicate that vestibular information can be used effectively to initiate vergence eye movements following vergence-vestibular training. 相似文献
86.
Thy Thy Vanem Tordis Böker Gunhild F. Sandvik Eva Kirkhus Hans‐Jørgen Smith Kai Andersen Liv Drolsum Rigmor Lundby Cecilie Røe Kirsten Krohg‐Sørensen Odd R. Geiran Benedicte Paus Svend Rand‐Hendriksen 《American journal of medical genetics. Part A》2020,182(2):397-408
The age‐dependent penetrance of organ manifestations in Marfan syndrome (MFS) is not known. The aims of this follow‐up study were to explore how clinical features change over a 10‐year period in the same Norwegian MFS cohort. In 2003–2004, we investigated 105 adults for all manifestations in the 1996 Ghent nosology. Ten years later, we performed follow‐up investigations of the survivors (n = 48) who consented. Forty‐six fulfilled the revised Ghent criteria. Median age: females 51 years, range 32–80 years; males 45 years, range 30–67 years. New aortic root dilatation was detected in patients up to 70 years. Ascending aortic pathology was diagnosed in 93 versus 72% at baseline. Sixty‐five percent had undergone aortic surgery compared to 39% at baseline. Pulmonary trunk mean diameter had increased significantly compared to baseline. From inclusion to follow‐up, two patients (three eyes) developed ectopia lentis, four developed dural ectasia, four developed scoliosis, three developed incisional or recurrent herniae, and 14 developed hindfoot deformity. No changes were found regarding protrusio acetabuli, spontaneous pneumothorax, or striae atrophicae. The study confirms that knowledge of incidence and progression of organ manifestations throughout life is important for diagnosis, treatment, and follow‐up of patients with verified or suspected MFS. 相似文献
87.
Joseph Rogers Michael A. Silver William J. Shoemaker Floyd E. Bloom 《Neurobiology of aging》1980,1(1):3-11
A within-subjects design was used to assess age changes in cerebellar Purkinje neurons. Four groups of naive male Sprague-Dawley rats, aged 3, 10, 20, and 28 months, underwent single cell recording for electrophysiological assessment of Purkinje cell firing patterns, followed by perfusion for glyoxylic acid induced catecholamine fluorescence. Cerebellar sections were photographed first by fluorescence microscope for catecholamines, and 2–3 weeks later for quantification of lipofuscin autofluorescence. Finally, these same tissues were treated with cresyl violet and photographed a third time to permit quantitative estimates of age changes in the number of Nissl staining Purkinje neurons. Electrophysiological studies revealed significant effects of age on a number of Purkinje cell firing parameters: in particular, increasing numbers of aberrant, very slow-firing cells were encountered in older animals. These cells showed normal climbing fiber mediated burst activity, but spontaneous simple spike firing rates 3–5 times less than normal. Rats exhibiting the highest numbers of such abnormal cells also exhibited the poorest Nissl staining. Conversely, good Nissl staining of Purkinje neurons in an old rat was a reliable predictor of relatively normal Purkinje cell firing. Lipofuscin was found to accumulate measurably in Purkinje neurons by 20 months of age, and to increase significantly thereafter. Deposition of the substance occurred almost exclusively at the apical pole of the soma. Our data suggest, however, that accumulation of lipofuscin in Purkinje neurons, as well as its reported accumulation in the inferior olive, is not a primary cause of electrophysiological dysfunction. There was no apparent age change in glyoxylic acid induced catecholamine fluorescence nor, in separate pharmacological studies, could any senescent alteration in cerebellar catecholamine levels be found. 相似文献
88.
Reflections on experimental and human pathology of aggression 总被引:1,自引:0,他引:1
L Valzelli 《Progress in neuro-psychopharmacology & biological psychiatry》1984,8(3):311-325
On the basis of the already proposed distinction between "normal" and "pathological" aggression in laboratory animals, it is essayed an integration of the experimental findings derived from a specific animal model of aggression with the available clinical information on human violent behavior. The too disregarded importance of the role played by the inhibitory control of brain functions, appears instead reportedly essential in the regulation of emotions and behavior, and is of great relevance in explaining the behavioral changes that follow induced or spontaneous impairment of the serotonergic system of the brain. As a matter of fact, the numerous evidences indicate that genetic predisposition and induced or acquired defects of serotonergic inhibitory control greatly concur to precipitate anomalous strong aggression. Interestingly, the cluster of symptoms presented by laboratory rats in consequence of the serotonergic discontrol, has many unexpected similarities with several pathological conditions of man. This fact confers to laboratory experiments the value of a tool aimed at a better understanding of the biological mechanisms which underlie corresponding alterations of human conduct, with special reference to pathological aggression and violence. In this line, some specific nutrient defects and/or malabsorption conditions can be important in the facilitation or elicitation of mental illness including human aggression. In addition, the efficacy and neurochemical action of those substances capable to partially or completely block or prevent experimental aggression, will likely assume equal relevance in the management or prevention of human violent behavior. 相似文献
89.
以某生物安全实验室典型核心工作间为例,阐述了其负荷情况。并结合笔者单位近两年检测的28个生物安全三级实验室项目中的98间核心工作间,分析了换气次数的分布频次与室内洁净度的关系,探讨了高等级生物安全实验室的节能措施。 相似文献
90.
目的探讨合体细胞滋养层细胞外囊泡(STB-EV)阻止母体恶性肿瘤侵袭、转移至胎儿的相关机制。 方法选择2015年6月,于四川大学华西第二医院进行剖宫产术分娩的1例妊娠合并宫颈癌(CCP)患者被肿瘤侵犯的胎盘组织为研究对象。宫颈癌细胞系SiHa细胞和人滋养层细胞系HTR-8细胞,均由本院西部妇幼医学研究院-分子与转化医学实验室馈赠。其中,本例CCP患者被肿瘤侵犯的胎盘组织制作组织切片后,于光学显微镜(×400)和电子显微镜(×2 000)下,观察其组织形态学、STB-EV及合体细胞滋养层(STB)旁宫颈癌细胞自噬性死亡情况等;而SiHa细胞与HTR-8细胞培养后,用于Transwell迁移实验与细胞划痕实验。将SiHa与HTR-8细胞共培养,纳入研究组;单独培养的SiHa细胞,纳入对照组。对2组细胞进行Transwell迁移实验及细胞划痕实验,2组Transwell小室穿膜细胞数、细胞迁移率等比较,采用成组t检验。本研究遵循的程序符合2013年新修订的《世界医学协会赫尔辛基宣言》要求。 结果①对本例CCP患者被肿瘤侵犯的胎盘组织制作组织切片后,于光学显微镜(×400)下观察结果显示,与STB相邻宫颈癌细胞自噬性死亡、凋亡和固缩性坏死显著。电子显微镜(×2 000)下观察结果显示,宫颈癌细胞累及胎盘绒毛组织时,STB分泌的STB-EV水平显著高于正常胎盘组织。②2组细胞Transwell迁移实验结果显示,研究组穿膜细胞数为(597.6±87.7)个/视野,显著低于对照组的(1 358.4±203.0)个/视野,并且差异有统计学意义(t=14.490、P<0.001)。③2组细胞划痕实验结果显示,划痕后48 h时,研究组细胞迁移率为(26.6±3.8)%,显著低于对照组的(45.9±3.7)%,并且差异有统计学意义(t=3.122、P=0.035)。 结论STB分泌的STB-EV可能参与母体肿瘤细胞广泛自噬性死亡,从而阻止母体肿瘤细胞侵袭胎盘、影响胎儿发育。 相似文献