全文获取类型
收费全文 | 4285篇 |
免费 | 341篇 |
国内免费 | 96篇 |
专业分类
耳鼻咽喉 | 39篇 |
儿科学 | 39篇 |
妇产科学 | 27篇 |
基础医学 | 542篇 |
口腔科学 | 55篇 |
临床医学 | 374篇 |
内科学 | 337篇 |
皮肤病学 | 62篇 |
神经病学 | 308篇 |
特种医学 | 132篇 |
外科学 | 383篇 |
综合类 | 969篇 |
预防医学 | 325篇 |
眼科学 | 47篇 |
药学 | 388篇 |
6篇 | |
中国医学 | 320篇 |
肿瘤学 | 369篇 |
出版年
2024年 | 8篇 |
2023年 | 64篇 |
2022年 | 145篇 |
2021年 | 214篇 |
2020年 | 209篇 |
2019年 | 120篇 |
2018年 | 129篇 |
2017年 | 166篇 |
2016年 | 168篇 |
2015年 | 137篇 |
2014年 | 312篇 |
2013年 | 314篇 |
2012年 | 293篇 |
2011年 | 284篇 |
2010年 | 204篇 |
2009年 | 171篇 |
2008年 | 191篇 |
2007年 | 218篇 |
2006年 | 141篇 |
2005年 | 112篇 |
2004年 | 107篇 |
2003年 | 110篇 |
2002年 | 83篇 |
2001年 | 88篇 |
2000年 | 62篇 |
1999年 | 47篇 |
1998年 | 41篇 |
1997年 | 51篇 |
1996年 | 40篇 |
1995年 | 44篇 |
1994年 | 41篇 |
1993年 | 28篇 |
1992年 | 33篇 |
1991年 | 35篇 |
1990年 | 23篇 |
1989年 | 19篇 |
1988年 | 19篇 |
1987年 | 27篇 |
1986年 | 21篇 |
1985年 | 18篇 |
1984年 | 29篇 |
1983年 | 20篇 |
1982年 | 28篇 |
1981年 | 17篇 |
1980年 | 19篇 |
1979年 | 19篇 |
1978年 | 14篇 |
1977年 | 15篇 |
1976年 | 12篇 |
1971年 | 3篇 |
排序方式: 共有4722条查询结果,搜索用时 93 毫秒
31.
32.
目的:探讨血小板活化因子(PAF)、癌胚抗原(CEA)、糖类抗原724(CA-724)在结直肠癌(CRC)患者术前血清中的阳性表达率及与临床病理特征的关系、发病的独立危险因素。方法:选取2019年12月至2021年10月于包头医学院第一附属医院就诊的CRC患者75例为CRC组,另选取同时期在本院体检的健康志愿者75例为对照组。采用酶联免疫吸附(ELISA)法分别检测CRC患者术前及对照组的晨空腹外周静脉血PAF含量;回顾性分析上述入组患者术前血清CEA、CA-724含量,进行统计分析。结果:(1)CRC组PAF、CEA、CA-724单独检测和联合检测的阳性率分别为25.33%、42.67%、30.67%、74.67%,均高于对照组,且联合检测的阳性率均高于单独检测指标的阳性率,组间差异均具有统计学意义(P<0.05);(2)单因素方差分析结果显示,血清CEA表达水平的影响因素为患者的淋巴结转移(P<0.05);血清CA-724表达水平的影响因素为患者的年龄(P<0.05);(3)二元Logistic回归分析结果显示,PAF表达在临床病理特征之间的差异无统计学意义(P&... 相似文献
33.
Summary Muscle force recovery from short term intense exercise was examined in 16 physically active men. They performed 50 consecutive
maximal voluntary knee extensions. Following a 40-s rest period five additional maximal contractions were executed. The decrease
in torque during the 50 contractions and the peak torque during the five contractions relative to initial torque were used
as indices for fatigue and recovery, respectively. Venous blood samples were collected repeatedly up to 8 min post exercise
for subsequent lactate analyses. Muscle biopsies were obtained from m. vastus lateralis and analysed for fiber type composition,
fiber area, and capillary density.
Peak torque decreased 67 (range 47–82%) as a result of the repeated contractions. Following recovery, peak torque averaged
70 (47–86%) of the initial value.
Lactate concentration after the 50 contractions was 2.9±1.3 mmol·l−1 and the peak post exercise value averaged 8.7±2.1 mmol·l−1. Fatigue and recovery respectively were correlated with capillary density (r=−0.71 and 0.69) but not with fiber type distribution. A relationship was demonstrated between capillary density and post
exercise/peak post exercise blood lactate concentration (r=0.64). Based on the present findings it is suggested that lactate elimination from the exercising muscle is partly dependent
upon the capillary supply and subsequently influences the rate of muscle force recovery.
Dr. Tesch was on leave from Department of Clinical Physiology, Karolinska Hospital, Stockholm, Sweden 相似文献
34.
Dilatational, hypertrophic, aneurysmal, and endocardial variants of remodeling were revealed in the postinfarction heart. The most prevalent dilatational remodeling is characterized by uniform or nonuniform elongation of ventricular cavities and increase in ventricular volume. Characteristic features of the hypertrophic type are hypertrophied interventricular septa and left ventricular wall and reduced or unchanged left ventricular volume. Pronounced changes in the configuration of the left ventricle due to the formation of single or multiple aneurysms were typical of aneurysmal remodeling. Endocardial remodeling was characterized by cicatricial changes and smoothed relief of the parietal endocardium. These variants and forms of remodeling determine disturbances in intracardial hemodynamic and thanatogenesis in the postinfarction period. 相似文献
35.
Single fibres of three different types, which had been characterized histochemically with regard to differences in myofibrillar adenosine triphosphatase (ATPase) activity and its pH stability, were microdissected from freeze dried preparations of the closer muscle in walking legs of the crab Eriphia spinifrons. Shortening velocities were determined in slack tests and under constant load conditions in maximally Ca2+-activated skinned muscle fibres. Force/pCa relationships were also measured for the different types of fibres. Compared with data on vertebrate muscles, all crab muscle fibres required large length changes to reach zero force and showed low Ca2+ sensitivity for isometric force generation. The length/time relationship obtained from slack tests had a biphasic course. Maximal velocity of filament sliding differed in the three types of fibres investigated. The filament sliding of type IV fibres was about 3 times faster than that of type I fibres. The values obtained for type II fibres ranged in between. These data are positively correlated with myofibrillar ATPase activity determined histochemically. Ca2+ sensitivity of force generation was lowest in the fast type IV fibres. It was high in the slow type I and the faster contracting type II fibres. Ca2+ sensitivity in crab muscle seems not to be correlated with speed of shortening. 相似文献
36.
The effects of different types of clothing on human deep body temperature were studied with six healthy male subjects in a supine posture. Two clothing ensembles were employed for the present study: A covered the whole body area with garments except the face (1.97 clo) and B covered only the trunk and the upper half of the extremities with garments (1.53 clo). The experiment was carried out in a climatic chamber at 55% ± 5% relative humidity under cooling and warming temperatures: the temperature was changed from 22°C to 10°C (cooling) and returned to 22°C again (warming). The major findings were: rectal temperature (T
re) continued to decrease gradually in A throughout the experiment, whereas in B it increased during cooling, and returned to previous levels during warming. As a result, Tre and chest skin temperature were maintained at a higher level in B than in A. Internal tissue conductances were greater in A than in B both during cooling and during warming. Thermal comfort appeared to have been influenced more by the rate of skin temperature change than by the level of skin temperature per se. It was concluded that peripheral vasoconstriction in B induced less heat flow from core to shell, and, thus, the core temperature was maintained at a higher level in B than in A. 相似文献
37.
Silvia Obenauer Christian Sohns Carola Werner Eckhardt Grabbe 《Journal of digital imaging》2006,19(3):258-263
The goal of this study was to evaluate the performance of a computer-aided detection (CAD) system in full-field digital mammography
(Senographe 2000D, General Electric, Buc, France) in finding out carcinomas depending on the parenchymal density. A total
of 226 mediolateral oblique (MLO) and 186 craniocaudal (CC) mammographic views of histologically proven cancers were retrospectively
evaluated with a digital CAD system (ImageChecker V2.3 R2 Technology, Los Altos, CA, USA). Malignant tumors were detected
correctly by CAD in MLO view in 84.85% in breasts with parenchymal tissue density of the American College of Radiology (ACR)
type 1, in 70.33% of the ACR type 2, in 68.12% of the ACR type 3, and in 69.70% of the ACR type 4. For the CC view, similar
results were found according to the ACR types. Using the chi-square and McNemar tests, there was no statistical significance.
However, a trend of better detection could be seen with decreasing ACR type. In conclusion, there seems to be a tendency for
breast tissue density to affect the detection rate of breast cancer when using the CAD system. 相似文献
38.
K.-M. Zhang Ping Hu Shang-Wu Wang Leon D. Wright Andrew S. Wechsler John A. Spratt F. N. Briggs 《Pflügers Archiv : European journal of physiology》1997,433(6):766-772
Using an immunohistochemical double-labeling technique, we observed that different isoforms of sarcoplasmic reticulum Ca-ATPase
are co-expressed in single fibers of canine fast-twitch skeletal muscles stimulated chronically at low frequency. By 7 days
of neuromuscular stimulation, the population of hybrid fibers expressing both SERCA1 and SERCA2a [fast- and slow-twitch isoforms
of sarco(endo)plasmic reticulum Ca2+-ATPase] had increased from 1.5% to 9.2% of fibers. By 14 days of stimulation 90% of the pure fast-twitch fibers (expressing
only SERCA1) were replaced by hybrid fibers. An additional 28 days of stimulation caused all fast-twitch fibers to express
SERCA2a at the same level as found in nonstimulated slow-twitch fibers (expressing only SERCA2a). At this time, one-half of
the previously hybrid fibers had become pure slow-twitch fibers. The remaining one-half of the hybrid fibers expressed SERCA1
at a very low level. Extending stimulation to 70 days did not further change the percentage of fibers that were slow-twitch
or hybrid. Immunoblot studies at the whole-muscle level confirmed that changes in SERCA expression at 42 days of neuromuscular
stimulation were complete. Immunohistochemical analysis of longitudinal sections of muscle showed that the changes in SERCA
protein were uniform along the length of the muscle fiber, indicating that nuclei along its length responded equally to chronic
stimulation.
Received: 12 November 1996 / Received after revision and accepted: 16 December 1996 相似文献
39.
Summary Serial sections (15 m, 120 m, and 400 m) of nine brain stems treated with a combined lipofuscin pigment-Nissl stain were examined in order to delineate the three-dimensional conformation and subdivisions as well as the neuronal types of the human oral raphe system. Characteristic lipofuscin deposits within the somata of various cell types facilitated the demarcation of the oral raphe nuclei from surrounding structures. The dorsal, central, and linear raphe nuclei, e.g. the major subdivisions of the oral raphe system, share common traits as far as neuronal composition and pigmentation is concerned. The interfascicular subnucleus, the dorsofascicular subnucleus, and the intercalate subnucleus are minor subdivisions of the dorsal raphe nucleus. The intercalate one cannot be differentiated from surrounding areas in preparations solely stained for Nissl-material, while it can facilely be identified in combined pigment-Nissl preparations by virtue of differences in the pigmentation pattern. Our architectonical concept of the oral raphe system is in good accordance with the one derived from immunocytochemical investigations of serotonin-containing neurons in the human brain stem. Furthermore, five main neuronal types are described which constitute the oral raphe nuclei. They have been differentiated according to their characteristics as seen in combined pigment-Nissl preparations. I) Large ovoid to polygonal neurons with densely packed and intensely stained pigment granules. II) Similarily featured cells displaying dust-fine and faintly stained pigment granules. III) Medium-sized, ovoid to polygonal neurons with loosely distributed, small pigment granules. IV) Small ovoid neurons devoid of pigment or with only few, intensely stained granules. V) Small spindleshaped nerve cells with various amounts of intensely stained pigment granules. The morphometrical examination has revealed considerable overlapping in size between types I and II. A fact that would not allow a distinction in preparations solely stained for Nissl-material. 相似文献
40.
大学生网络成瘾类型问卷的初步编制 总被引:14,自引:2,他引:14
目的:编制适用我国大学生的网络成瘾类型问卷。方法:根据访谈、开放式问卷施测结果,编制大学生网络成瘾类型问卷;调查样本为733名武汉地区大学生,91名大学生作为重测样本;检验了问卷的同质信度、重测信度、结构效度等。结果:探索性因素分析获得3个因素,即网络游戏成瘾、网络人际关系成瘾及网络信息成瘾,各因子负荷在0·50~0·82之间。总问卷及各分问卷的同质性信度(Cronbachα)、分半信度及重测信度分别为0·80~0·92、0·79~0·90和0·81~0·91。验证性因素分析结果表明问卷的三因素模型各项参数(RMSEA=0·07,CFI=0·98,NFI=0·97,IFI=0·98,TLI=0·97,RFI=0·96)均达到可以接受的水平。结论:该问卷具有较好的信度和效度,可用于大学生网络成瘾类型的测试。 相似文献