全文获取类型
收费全文 | 5966篇 |
免费 | 521篇 |
国内免费 | 142篇 |
专业分类
耳鼻咽喉 | 19篇 |
儿科学 | 39篇 |
妇产科学 | 46篇 |
基础医学 | 656篇 |
口腔科学 | 89篇 |
临床医学 | 308篇 |
内科学 | 1116篇 |
皮肤病学 | 16篇 |
神经病学 | 327篇 |
特种医学 | 83篇 |
外科学 | 117篇 |
综合类 | 423篇 |
预防医学 | 1508篇 |
眼科学 | 70篇 |
药学 | 1326篇 |
中国医学 | 227篇 |
肿瘤学 | 259篇 |
出版年
2023年 | 68篇 |
2022年 | 143篇 |
2021年 | 242篇 |
2020年 | 140篇 |
2019年 | 154篇 |
2018年 | 225篇 |
2017年 | 236篇 |
2016年 | 244篇 |
2015年 | 217篇 |
2014年 | 322篇 |
2013年 | 700篇 |
2012年 | 343篇 |
2011年 | 416篇 |
2010年 | 294篇 |
2009年 | 255篇 |
2008年 | 275篇 |
2007年 | 277篇 |
2006年 | 236篇 |
2005年 | 178篇 |
2004年 | 179篇 |
2003年 | 174篇 |
2002年 | 135篇 |
2001年 | 138篇 |
2000年 | 87篇 |
1999年 | 85篇 |
1998年 | 75篇 |
1997年 | 60篇 |
1996年 | 53篇 |
1995年 | 61篇 |
1994年 | 64篇 |
1993年 | 46篇 |
1992年 | 33篇 |
1991年 | 36篇 |
1990年 | 29篇 |
1989年 | 16篇 |
1988年 | 33篇 |
1987年 | 27篇 |
1986年 | 28篇 |
1985年 | 46篇 |
1984年 | 23篇 |
1983年 | 43篇 |
1982年 | 23篇 |
1981年 | 35篇 |
1980年 | 22篇 |
1979年 | 30篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1976年 | 11篇 |
1975年 | 11篇 |
1973年 | 14篇 |
排序方式: 共有6629条查询结果,搜索用时 15 毫秒
41.
Kazuya Takeda Shuhei Sakakibara Kazuo Yamashita Daisuke Motooka Shota Nakamura Marwa Ali El Hussien Jun Katayama Yohei Maeda Masanobu Nakata Shigeyuki Hamada Daron M. Standley Masaki Hayama Takashi Shikina Hidenori Inohara Hitoshi Kikutani 《The Journal of allergy and clinical immunology》2019,143(3):1163-1175.e15
42.
Central amygdaloid nucleus lesions in rats had no effect on recovery of preoperative body weight and food consumption levels. The brain damaged rats also recovered preoperative levels of water consumption as rapidly as control rats but then developed a mild but persistent hypodipsia. The experimental rats also drank less than control rats when food deprived and showed marginally reliable decreases in 0.1% quinine solution consumption and latency to consume a novel food. There was no detectable lesion effect on 0.1% saccharin solution consumption, exploration of a novel environment or formation of a learned taste aversion. It is suggested that the central amygdaloid nucleus has a role in mediating the relationship between food and water intake and in some taste mediated consummatory behavior. 相似文献
43.
Feeding and drinking rhythms were studied in rats maintained under 24-hr light-dark (LD) cycles with various photoperiods, under two-pulse (2P) and one-pulse (1P) skeleton photoperiods, and under constant dark (DD). Rhythmic waveforms were similar under complete LD cycles and corresponding skeleton photoperiods, indicating that these rhythms mainly reflect the entrainment of underlying circadian pacemakers. Little or no role was found for masking effects of light on circadian feeding and drinking waveforms. Entrainment was found to depend mainly on the timing of the dawn light signal, whether it was a 15-min light pulse or a dark-to-light transition initiating a complete photoperiod. Furthermore, the use of 1P schedules revealed that a dawn signal was sufficient for entrainment. These results closely match those obtained for motor activity measures in other nocturnal rodent species, and generally conform to the predictions of Pittendrigh's nonparametric theory of entrainment. Furthermore, the close correspondence of the two rhythms during entrainment, phase-jumps, and free-running (DD) conditions indicates that they are controlled by common circadian pacemakers. 相似文献
44.
Masumura K Kuniya K Kurobe T Fukuoka M Yatagai F Nohmi T 《Environmental and molecular mutagenesis》2002,40(3):207-215
Heavy-ion radiation accounts for the major component of absorbed cosmic radiation and is thus regarded as a significant risk during long-term manned space missions. To evaluate the genetic damage induced by heavy particle radiation, gpt delta transgenic mice were exposed to carbon particle irradiation and the induced mutations were compared with those induced by reference radiations, i.e., X-rays and gamma-rays. In the transgenic mouse model, deletions and point mutations were individually identified as Spi(-) and gpt mutations, respectively. Two days after 10 Gy of whole-body irradiation, the mutant frequencies (MFs) of Spi(-) and gpt were determined. Carbon particle irradiation significantly increased Spi(-) MF in the liver, spleen, and kidney but not in the testis, suggesting an organ-specific induction of mutations by heavy-ion irradiation. In the liver, the potency of inducing Spi(-) mutation was highest for carbon particles (3.3-fold increase) followed by X-rays (2.1-fold increase) and gamma-rays (1.3-fold increase), while the potency of inducing gpt mutations was highest for gamma-rays (3.3-fold increase) followed by X-rays (2.1-fold increase) and carbon particles (1.6-fold increase). DNA sequence analysis revealed that carbon particles induced deletions that were mainly more than 1,000 base pairs in size, whereas gamma-rays induced deletions of less than 100 base pairs and base substitutions. X-rays induced various-sized deletions and base substitutions. These results suggest that heavy-ion beam irradiation is effective at inducing deletions via DNA double-strand breaks but less effective than X-ray and gamma-ray irradiation at producing oxidative DNA damage by free radicals. 相似文献
45.
Alcohol use disorders in persons with co-occurring psychiatric disorders are associated with high rates of psy-chosocial instability and poorer treatment outcomes. Thus, assessment of alcohol use and abuse should become an integral part of psychiatric care. Because setf-report-based measures are frequently used, issues of reliability and validity in this population should be critically examined. The purpose of this article is to review and critique the existing empirical literature that has evaluated the psychometric integrity of self- report-based measures in psychiatric settings, and to outline a research agenda that promises to enhance the accuracy of alcohol assessment by persons receiving psychiatric treatment. 相似文献
46.
Rats were permanently hypodipsic when offered a quinine adulterated fluid on a chronic basis. Plasma osmolarity and Na concentration were normal, but the quinine drinkers showed a slight hyperkalemia compared to water drinking controls. The quinine-drinking rats maintained hydromineral equilibrium through the excretion of a small amount of concentrated urine. The quinine intake was closely matched to need, and fell to near zero when food was removed or water was supplied intravenously. This harmony of intake and output was disrupted after acute hypertonic NaCl load: while the obligatory salt diuresis was no different between water and quinine drinkers, the latter did not drink (except at the lowest level of adulteration) within several hours. However, by 24 hr all had shown a delayed drinking response. This delay in drinking of quinine was also evident after non-painful intravenous NaCl infusions, but no drinking occurred after nephrectomy. Quinine drinkers were also unresponsive to isoproterenol and intracranial dipsogens. These data are discussed in terms of their implication for definitions of regulatory drinking behavior. 相似文献
47.
W. G. L. Kerrick D. A. Malencik P. E. Hoar J. D. Potter R. L. Coby S. Pocinwong E. H. Fischer 《Pflügers Archiv : European journal of physiology》1980,386(3):207-213
The mechanism of contraction in rabbit fast-twitch, and bovine and rabbit cardiac muscle was examined using functionally skinned fibers, ATPase activity of myofibrils, and cardiac or skeletal troponintropomyosin regulated actin heavy meromyosin. The Ca2+ and Sr2+ activation properties for the different measures of contraction were evaluated. (1) Tension in rabbit and bovine cardiac skinned fibers and rabbit cardiac myofibrillar ATPase were activated equally well by either Ca2+ or Sr2+. By contrast, rabbit adductor magnus (fast-twitch) skinned fibers required substantially higher [Sr2+] than [Ca2+] for activation, as did rabbit myofibrils from back muscle (fast-twitch). (2) Substantially more Sr2+ than Ca2+ was also required for activation of skeletal muscle actin heavy meromyosin ATPase, controlled by either the skeletal or cardiac troponin-tropomyosin complex, similar to the activation of fast-twitch muscle. (3) The absence of correlation between the divalent cation selectivity properties of actin heavy meromyosin ATPase controlled by cardiac troponin-tropomyosin and cardiac muscle tension or myofibrillar ATPase activation by Ca2+ and Sr2+ suggests that troponin, if primarily responsible for the activation of cardiac muscle, has very different in vivo and in vitro binding properties. (4) The close correlation between percentage of maximal Ca2+- and Sr2+-activated myofibrillar ATPase and tension in skinned fibers strongly justifies the use of myofibrillar ATPase, in contrast to a reconstituted troponin-tropomyosin actin heavy meromyosin ATPase system, as a biochemical measure of contraction. 相似文献
48.
Histochemical methods are routinely used to delineate skeletal muscle fiber types. In the present investigation, this qualitative determination of fiber type composition was compared to the electrophoretically determined myosin heavy chain (MHC) content from a large number of human muscle biopsy samples. Biopsies were taken from the vastus lateralis muscle at the beginning and every 2 weeks during 8 weeks of highi-ntensity resistance training from men (n = 13) and woman (n = 8). Muscle was also extracted from nontraining men (n = 7) and women (n = 5) at the same periods. Six muscle fiber types (I, IC, IIAC, IIA, IIAB, and IIB) were determined using basic myofibrillar adenosine triphosphatase histochemistry. Cross-sectional areas were determined for the three major fiber types (I, IIA, and IIB) and used to calculate the percentage area of these types. Electrophoretic techniques were used to separate and quantify the percentage MHC content in these same biopsy samples, and these data were then used to compare with the percentage fiber type area. Correlation analyses suggest a relationship between the histochemically assessed percentage fiber type area and the electrophoretically assessed MHC content in human limb musculature. However, because of possible histochemical misclassification of some fibers (especially in trained muscle) both techniques may be essential in yielding important information about fiber type composition and possible fiber type transformations. 相似文献
49.
Characterization of idiotopes on MOPC 315 IgA using monoclonal antiidiotypic antibodies 总被引:1,自引:0,他引:1
Terresa Nusair Reuben Baumal Robert Rosenstein Trond Jørgensen Alexander Marks 《Molecular immunology》1983,20(5):537-547
The isologous antiidiotypic response in BALB/c mice to immunization with the DNP-binding IgA myeloma protein, MOPC 315, alters the expression of the anti-DNP antibody repertoire and confers immunity against MOPC 315 myeloma tumors. In order to characterize the idiotopes on MOPC 315 IgA which elicit this response we have isolated four monoclonal antiidiotypic antibodies (AIA), D10 (IgG2a), A2(IgG1), G3 (IgG2b) and F1 (IgG2a), produced by splenocytes of BALB/c mice immunized with MOPC 315 IgA in three independent fusion experiments. These AIA react with MOPC 315 IgA. reassociated H315 L315 and F315V but not with free H315, L315, V315H or V3152. In addition the AIA do not react with the closely related DNP-binding IgA myeloma protein, MOPC 460, suggesting that they are directed against private idiotopes on MOPC 315 IgA. These idiotopes can be divided into two groups. Group I, defined by D10, A2 and G3 consists of two overlapping idiotopes, one of which is related to the hapten-binding site. The two idiotopes are formed by an interaction of amino acids in H315 and L315. Group II defined by F1 consists of one idiotope which is related to the hapten-binding site. This idiotope is comprised of an aminoacid sequence on H315 which requires an interaction with either L315 or L460 for expression. A2 and G3 react identically with the same idiotope but were derived from two independent fusion experiments. This indicates an identity of AIA clonotypes among individual mice and suggests that the isologous AIA response to MOPC 315 IgA is restricted. 相似文献
50.