全文获取类型
收费全文 | 15309篇 |
免费 | 706篇 |
国内免费 | 400篇 |
专业分类
耳鼻咽喉 | 102篇 |
儿科学 | 193篇 |
妇产科学 | 135篇 |
基础医学 | 2513篇 |
口腔科学 | 929篇 |
临床医学 | 766篇 |
内科学 | 2042篇 |
皮肤病学 | 128篇 |
神经病学 | 1147篇 |
特种医学 | 251篇 |
外科学 | 2314篇 |
综合类 | 1353篇 |
现状与发展 | 1篇 |
预防医学 | 731篇 |
眼科学 | 68篇 |
药学 | 3057篇 |
5篇 | |
中国医学 | 376篇 |
肿瘤学 | 304篇 |
出版年
2023年 | 102篇 |
2022年 | 241篇 |
2021年 | 311篇 |
2020年 | 277篇 |
2019年 | 305篇 |
2018年 | 342篇 |
2017年 | 302篇 |
2016年 | 318篇 |
2015年 | 340篇 |
2014年 | 784篇 |
2013年 | 828篇 |
2012年 | 708篇 |
2011年 | 790篇 |
2010年 | 627篇 |
2009年 | 724篇 |
2008年 | 705篇 |
2007年 | 684篇 |
2006年 | 658篇 |
2005年 | 611篇 |
2004年 | 481篇 |
2003年 | 453篇 |
2002年 | 411篇 |
2001年 | 354篇 |
2000年 | 331篇 |
1999年 | 364篇 |
1998年 | 316篇 |
1997年 | 305篇 |
1996年 | 274篇 |
1995年 | 286篇 |
1994年 | 289篇 |
1993年 | 229篇 |
1992年 | 218篇 |
1991年 | 171篇 |
1990年 | 184篇 |
1989年 | 165篇 |
1988年 | 139篇 |
1987年 | 181篇 |
1986年 | 140篇 |
1985年 | 205篇 |
1984年 | 175篇 |
1983年 | 137篇 |
1982年 | 153篇 |
1981年 | 117篇 |
1980年 | 111篇 |
1979年 | 104篇 |
1978年 | 81篇 |
1977年 | 77篇 |
1976年 | 63篇 |
1975年 | 46篇 |
1973年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
The Farr assay for the detecton of antibodies to double stranded (ds) DNA is influenced by the DNA preparations used as antigen. To elucidate this the molecular weight of the antigen preparation, contamination with proteins and presence or absence of single stranded (ss) regions were studied with the following conclusions: 1) The degree of DNA binding by antibodies is linearly dependent on the molecular weight of the DNA, provided that this does not exceed 10 X 10(6). 2) Deproteinization of E. coli DNA by chromatography on methylated albumin-kieselguhr(MAK) columns results in lower binding by most sera. 3) ds DNA preparations sometimes contain ss regions which bind antibodies to ss DNA. The difference in behaviour of different ds DNA preparations may be ascribed entirely to these factors and not to differences in antigenic determinants. We have standardized the Farr assay and enhanced its specificity by the use of circular DNA isolated from bacteriophage PM2. 相似文献
142.
Association between HLA and Japanese patients with rheumatoid arthritis 总被引:12,自引:0,他引:12
N Ohta Y K Nishimura K Tanimoto Y Horiuchi C Abe Y Shiokawa T Abe M Katagiri T Yoshiki T Sasazuki 《Human immunology》1982,5(2):123-132
Japanese patients with rheumatoid arthritis (RA) were observed to have a statistical association with HLA-DR4, MT3. Strong association between the clinical severity of RA and HLA was also observed. Male patients had a stronger association with HLA than female patients. Males are more resistant to RA than females. This suggested that the threshold of liability for RA is higher in males than in females. Japanese patients with RA with systemic vasculitis were negative for HLA-Bw44 and had antilymphocytotoxic autoantibody, indicating that RA with systemic vasculitis is different in etiology from RA without systemic vasculitis. 相似文献
143.
P. D. BALSOM K. S
DERLUND B. SJ
DIN B. EKBLOM 《Acta physiologica (Oxford, England)》1995,154(3):303-310
Seven male subjects performed repeated bouts of high-intensity exercise, on a cycle ergometer, before and after 6 d of creatine supplementation (20 g Cr H2O day-1). The exercise protocol consisted of five 6-s exercise periods performed at a fixed exercise intensity, interspersed with 30-s recovery periods (Part I), followed (40 s later) by one 10 s exercise period (Part II) where the ability to maintain power output was evaluated. Muscle biopsies were taken from m. vastus lateralis at rest, and immediately after (i) the fifth 6 s exercise period in Part I and (ii) the 10 s exercise period in Part II. In addition, a series of counter movement (CMJ) and squat (SJ) jumps were performed before and after the administration period. As a result of the creatine supplementation, total muscle creatine [creatine (Cr) + phosphocreatine (PCr)] concentration at rest increased from (mean + SEM) 128.7 (4.3) to 151.5 (5.5)mmolkg_1 dry wt (P < 0.05). This was accompanied by a 1.1 (0.5) kg increase in body mass (P < 0.05). After the fifth exercise bout in Part I of the exercise protocol, PCr concentration was higher [69.7 (2.3) vs. 45.6 (7.5) mmol kg“‘ dry wt, P < 0.05], and muscle lactate was lower [26.2 (5.5) vs. 44.3 (9.9) mmol kg”1 dry wt, P < 0.05] after vs. before supplementation. In Part II, after creatine supplementation, subjects were better able to maintain power output during the 10-s exercise period (P < 0.05). There was no change in jump performance as a result of the creatine supplementation (P > 0.05). These findings show that enhanced fatigue resistance during short duration high-intensity exercise following creatine supplementation is associated with a greater availability of PCr and a lower accumulation of lactate in the muscle. The finding that jump performance was not enhanced suggests that short-term creatine feeding does not influence peak power output. 相似文献
144.
A. P. Somlyo A. V. Somlyo T. Kitazawa M. Bond H. Shuman D. Kowarski 《Annals of biomedical engineering》1983,11(6):579-588
Filamentous myosin is present in both relaxed (myosin light chains unphosphorylated) and contracted (light chains phosphorylated)
vascular smooth muscle. The organization of myosin and actin filaments and the insertion of the latter on cytoplasmic and
plasma membrane bound dense bodies is consistent with a mini sarcomere-like organization and a sliding filament mechanism
of contraction in smooth muscle.
Mitochondria are high capacity, low affinity Ca stores in smooth muscle. They do not play a role in the regulation of cytoplasmic
Ca2+ at physiological levels.
The localization and Ca content of the junctional sarcoplasmatic reticulum (SR) is consistent with this organelle being the
major intracellular source of activator Ca released by excitatory transmitters.
Repeated contractions in the absence of extracellular Ca2+ (thought to represent recycling of intracellular activator Ca2+) can be demonstrated if the excitatory agent is not allowed to remain in contact with the smooth muscle throughout relaxation;
the demonstration of “recycling” is facilitated if the efflux of cellular Ca2+ is blocked.
The rise in total cytoplasmic calcium measured with electron probe analysis during a maintained (30 min) contracture in rabbit
portal-anterior mesenteric vein smooth muscle (∼0.9 mmol/kg dry cytoplasm) is greater than the amount of Ca that could be
bound to calmodulin. 相似文献
145.
Masahiro Kamouchi Takanari KitazonoTetsuro Ago Masanori WakisakaJunya Kuroda Kuniyuki NakamuraNoriko Hagiwara Hiroaki OoboshiSetsuro Ibayashi Mitsuo Iida 《Neuroscience letters》2007
Objective: The aims of the present study were to elucidate the interaction of reactive oxygen species (ROS) and Ca2+ response in central nervous system (CNS) pericytes. Methods: The intracellular Ca2+ concentration was measured using fluorescent Ca2+ indicator, fura-2, in cultured CNS pericytes. Results: Hydrogen peroxide evoked a dose-dependent increase in cytosolic Ca2+, which was completely inhibited by catalase. Removal of external Ca2+ or addition of nicardipine (1 μM) during application of hydrogen peroxide did not affect Ca2+ response. Incubation of the cells in Ca2+ free solution did not abolish but slightly reduced Ca2+ response by hydrogen peroxide. Ca2+ response to hydrogen peroxide was not altered by the depletion of intracellular Ca2+ by thapsigargin (1 μM). Pretreatment of the cells with tyrosine kinase inhibitor genistein (100 μM) or tyrphostin A47 (30 μM) significantly reduced Ca2+ increase by hydrogen peroxide. Conclusions: These results indicate that hydrogen peroxide evokes Ca2+ increase predominantly by release from intracellular Ca2+ store, which may be regulated by tyrosine kinases. 相似文献
146.
Yusuf E. Karakullukçu Tayfun Özçelik Nuran Gökhan 《Pflügers Archiv : European journal of physiology》1987,410(6):657-663
Reperfusion of hearts with a Ca2+-containing medium after a perfusion period in Ca2+-free medium results in irreversible cell damage (calcium paradox). In this investigation we have studied coronary flow and cyclic AMP and cyclic GMP levels after several periods of Ca2+-free perfusion in isolated rat hearts. We also investigated the effects of papaverine (Pap), noradrenaline (NA), acetylcholine (ACh) and absence of inorganic phosphate during Ca2+-free perfusion on coronary flow (CF) and cyclic nucleotide levels. Inability of the heart to recover contractile activity with development of contracture during the reperfusion period was accepted as indicative of the calcium paradox. Ca2+-free perfusion alone and NA and absence of inorganic phosphate during the Ca2+-free perfusion period increased CF, whereas Pap and ACh decreased it. However, only Ca2+-free perfusion and NA elevated cyclic AMP. On the other hand, Pap and ACh increased cyclic GMP (with a transient rise of cyclic AMP in Pap infusion), and absence of inorganic phosphate decreased both cyclic AMP and cyclic GMP. Pap, ACh and absence of phosphate prevented the calcium paradox. Our study suggests that increased cyclic AMP during the Ca2+-free perfusion may contribute, with the other factors, to the occurrence of the calcium paradox. 相似文献
147.
K. Schäfer H. A. Braun F. Bretschneider P. F. M. Teunis R. C. Peters 《Pflügers Archiv : European journal of physiology》1990,417(1):100-105
The response properties of ampullary electroreceptors have been studied in the catfish Ictalurus nebulosus at skin temperatures between 5 and 35 °C. A unimodal relationship between spontaneous activity and temperature was obtained. Mean (±SEM) peak discharge rate was 57.3 ±1.8 impulses s–1 at 25 ° C; the receptors were active at 5 °C (15.0 impulses s–1) and at 35 °C (31.5 impulses s–1). There were no dynamic responses to temperature changes in either the warming or cooling direction. The shape of the frequency characteristic depended on temperature: the peak of the gain curve shifted to low frequencies at low temperatures. There was a concomitant change of the phase characteristic: the intersection at zero degree phase angle shifted to higher frequencies with an increase of temperature, thus increasing the lead at lower frequencies and decreasing the lag at higher frequencies. Latency after combined excitatory and inhibitory impulse stimulation was temperature dependent, ranging from 16.4 ms (5 °C) to 5.6 ms (35 °C). Application of the specific calcium channel blocker menthol (0.2 mM) suppressed spontaneous activity, the effect becoming more prominent at higher temperatures. Sensitivity to sinusoidal electrical stimulation was also impaired, but to a lesser degree and mainly at lower temperatures. We conclude that the filter properties of the receptor organ can be modelled by a band-pass filter in series with a latency, both of which are temperature dependent. These filter properties might be partially based on the activation kinetics of the tranduction channels. 相似文献
148.
A method for studying inhibitory activity in whole urine 总被引:4,自引:0,他引:4
Summary A method has been developed for inducing and quantifying calcium oxalate crystallisation in whole human urine. The propensity of a given urine to induce crystal formation was described in two ways: 1) its ability to resist spontaneous nucleation of calcium oxalate crystals was assessed by titrating 20 mls of the urine with increasing quantities of sodium oxalate (0–150 mol) to determine its practical metastable limit. This limit was inversely related to the endogenous calcium concentration. 2) its capacity to inhibit crystal growth was quantified by determining the rate of growth of calcium oxalate crystals precipitated in response to a fixed oxalate load (30 mol) above its metastable limit. The crystals produced were predominantly calcium oxalate dihydrate and were morphologically identical to those occurring naturally in urine. Citrate had no effect on the metastable limits of 3 urines examined, but markedly inhibited crystal growth. Pyrophosphate had a similar effect on crystal growth, and in addition, raised the metastable limit of one of the urine samples. 相似文献
149.
KAHAN A.; FOULT J. M.; WEBER S.; AMOR B.; MENKES C. J.; DEGEORGES M. 《European heart journal》1985,6(8):702-705
The efficacy of nifedipine and prazosin in the treatment ofRaynaud's phenomenon was assessed in a prospective double-blindrandomized cross-over trial in 15 patients. Each patient receivedone week of nifedipine 20 mg TID, one week of prazosin 1 mgTID, and 2 weeks of placebo. Nifedipine was shown to be effectivein reducing both the frequency and the severity of Raynaud'sphenomenon, whereas prazosin was ineffective. Before initiationof therapy in the 15 patients, pressor responses to the intravenousalpha1-agonist phenylephrine were assessed in the basal state,30 min after 20 mg oral nifedipine, and 30 min after 1 mg oralprazosin; the shift to the right of the log dose-vasopressorresponse curves to phenylephrine was similar with nifedipineand prazosin. 相似文献
150.
The effects of verapamil upon cerebrospinal fluid pressure (CSFP) were studied in twenty surgical patients without intracranial pathology who were divided into two groups of ten patients each: verapamil 0.075mg·kg–1 was given in group 1 and 0.15mg·kg–1 was given in group 2. A spinal needle was inserted into the subarachnoid space to permit continuous measurement of CSFP. Intravenous verapamil as a bolus produced a statistically significant increase in CSFP: from 6.0 ± 3.5 (mean ± SD) to 10.5 ± 4.3mmHg in group 1 (P < 0.01), and from 6.2 ± 3.1 to 12.6 ± 3.8mmHg in group 2 (P < 0.01). CSFP after verapamil attained its maximum in 0.5–1.5min, then gradually returned to control levels. Changes in CSFP were always associated with statistically significant decreases in arterial blood pressure and cerebral perfusion pressure, while the heart rate showed variable changes. It is concluded that a clinical dose of verapamil showed variable changes. It is concluded that a clinical dose of verapamil (0.075–0.15mg·kg–1) has no neurological side effects in patients without intracranial hypertension. However, it must be emphasized that verapamil may increase CSFP to undesirable levels and should be avoided in patients with compromised intracranial compliance.(Nishikawa T, Namiki A: The effects of verapamil on cerebrospinal fluid pressure in surgical patients. J Anesth 1: 132–136, 1987) 相似文献