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   1171篇
  免费   89篇
  国内免费   9篇
耳鼻咽喉   2篇
儿科学   52篇
妇产科学   20篇
基础医学   165篇
口腔科学   11篇
临床医学   174篇
内科学   254篇
皮肤病学   14篇
神经病学   99篇
特种医学   148篇
外科学   74篇
综合类   18篇
预防医学   36篇
眼科学   12篇
药学   153篇
  1篇
中国医学   6篇
肿瘤学   30篇
  2023年   8篇
  2022年   8篇
  2021年   16篇
  2020年   8篇
  2019年   15篇
  2018年   18篇
  2017年   11篇
  2016年   11篇
  2015年   15篇
  2014年   22篇
  2013年   34篇
  2012年   37篇
  2011年   31篇
  2010年   43篇
  2009年   36篇
  2008年   36篇
  2007年   50篇
  2006年   44篇
  2005年   37篇
  2004年   26篇
  2003年   32篇
  2002年   31篇
  2001年   35篇
  2000年   37篇
  1999年   34篇
  1998年   37篇
  1997年   39篇
  1996年   47篇
  1995年   42篇
  1994年   37篇
  1993年   26篇
  1992年   17篇
  1991年   20篇
  1990年   18篇
  1989年   37篇
  1988年   39篇
  1987年   33篇
  1986年   30篇
  1985年   29篇
  1984年   23篇
  1983年   15篇
  1982年   13篇
  1981年   12篇
  1980年   20篇
  1979年   8篇
  1978年   12篇
  1977年   12篇
  1976年   10篇
  1975年   5篇
  1973年   4篇
排序方式: 共有1269条查询结果,搜索用时 0 毫秒
1.
2.
Western transfer and immunoenzymatic staining with affinity-purified monospecific antiserum was used to detect a 38-Kd protein that bound to native and denatured DNA cellulose. This protein has previously been shown to be a delayed early herpes simplex virus type-2 specific protein.  相似文献   
3.
Reports on individual nonbehavioral child and adolescent psychotherapy since 1963 are reviewed. Inclusion criteria required some minimal contrasting group. Forty-three studies were assessed for basic methodological adequacy and main findings. The authors conclude that summary impressions from this body of literature cannot be made due to the magnitude of the flaws in basic psychotherapy research methodology. Suggestions are made regarding the future of child and adolescent psychotherapy research.  相似文献   
4.
1 Within the context of neural regulation of the activity of sinus node pacemaker cells, the study of heart rate variability, as explored in the frequency domain by spectral analysis, was proposed about 15 years ago as a quantitative tool for the evaluation of short-term autonomic cardiovascular control. It has since been postulated that the two main oscillations observed, one at low and the other at high frequency, may respectively be markers of sympathetic vs. vagal efferent cardiac activity, and that the low- and high-frequency signals may reflect a reciprocal or ‘push–pull’ relationship between sympathetic and parasympathetic control. 2 In our power spectra assessment, ECG R–R intervals were submitted to fast Fourier transformation analysis in order to study the mechanisms underlying the control of heart beats in rats. Data were acquired in conditions of steady arterial blood pressure and cardiac and respiratory activity (spontaneous or artificially stimulated) in diethyl-ether-anaesthetized and pithed rats, as well as in a group of control rats, all in the presence and absence of l-hyoscyamine. 3 With increasing doses of the parasympathetic antagonist, the fractal dimension of the time-series structure remained stable in most cases. The low-frequency spectral component narrowed with increasing drug doses and the high-frequency band underwent either no, or only very slight, changes. 4 In these rodent assays, the low- and high-frequency signals cannot be interpreted as a push–pull relationship between sympathetic and parasympathetic control.  相似文献   
5.
We had previously shown that inhibition of cyclooxygenase in vitro by indomethacin can cause increased formation of products of the 5-lipoxygenase pathway of arachidonic acid metabolism in leukocytes. To determine if this effect also occurred in vivo, we studied leukocyte arachidonic acid metabolism in 12 volunteers before and after ingestion of 150 mg indomethacin daily for 3 days. Blood was collected before treatment and 2 hours, 2 days, and 5 days after the final dose of indomethacin. Serum thromboxane B2, a measure of platelet cyclooxygenase activity, was profoundly suppressed 2 hours after the final dose of indomethacin but had recovered to control values at 2 days. Mixed leukocyte suspensions and purified neutrophil suspensions were prepared and stimulated with calcium ionophore A23187 and the resultant 5-lipoxygenase metabolites were quantified by HPLC. Two hours after the final dose of indomethacin, the stimulated levels of 5-hydroxyeicosatetraenoic acid, leukotriene B4, and leukotriene C4 were significantly increased to 247% +/- 68%, 135% +/- 14%, and 149% +/- 23% of pretreatment values, respectively. Two days after the final dose of indomethacin, 5-hydroxyeicosatetraenoic acid levels were still significantly elevated. By 5 days all parameters had returned to baseline. Similar effects were not observed in purified neutrophil suspensions, probably because of the loss of indomethacin from the cells during the multiple washing procedures used in their preparation. This is in accord with the reversible nature of the inhibitory effect of indomethacin on cyclooxygenase. We conclude that indomethacin at a commonly used dose increases the ability of circulating leukocytes to produce 5-lipoxygenase products.  相似文献   
6.
To facilitate the safe and thorough evacuation of cortical lens debris in extracapsular extractions the author has modified the coaxial irrigating-aspirating cannula. The modified needle has a 45 degrees bend 10 mm from its tip. The tip is rendered slightly bulbous, thus eliminating the step between the outer sleeve and the coaxial portion. This prevents snagging of the posterior capsule and eliminates sleeve slide. The needle has been found especially helpful in deeply recessed eyes, and, when it was rotated, cortical cleaning from the equatorial and superior portions of the capsular bag was easier than with a straight needle. There were no posterior capsular breakages in 54 consecutive cases of the use of this needle.  相似文献   
7.
We have looked at the role played by alpha 1 and alpha 2 adrenoceptors in the control of blood pressure in the anaesthetised spontaneously hypertensive rat (SHR) by examining the blood-pressure-lowering effects of the alpha 1-adrenoceptor antagonist prazosin and the alpha 2-adrenoceptor antagonist rauwolscine in 5 groups of animals: unoperated, adrenal demedullated, shamoperated, sympathectomised with 6-hydroxydopamine, and vehicle treated. Prazosin (1 mg/kg) produced significant falls in diastolic blood pressure (DBP) in all groups of rat but the fall was significantly less in sympathectomised animals. In the presence of prazosin (1 mg/kg), rauwolscine (0.1-1 mg/kg) lowered DBP in all groups of rat except the adrenal demedullated animals. In the absence of prazosin, rauwolscine (0.1 mg/kg) produced a significant fall in DBP only in sympathectomised animals. These results demonstrate that alpha 2 adrenoceptors are involved in blood pressure control in the intact or sympathectomised SHR but not following adrenal demedullation, suggesting that circulating catecholamines rather than neurally released noradrenaline (NA) are responsible for these alpha 2-adrenoceptor-mediated pressor effects. In contrast, only alpha 1-adrenoceptor-mediated pressor responses are reduced by sympathectomy, suggesting that neurally released NA acts mainly on alpha 1-adrenoceptors.  相似文献   
8.
1. We have examined the effects of a series of alpha 2-adrenoceptor antagonists against isometric contractions to noradrenaline in human saphenous vein, and correlated these potencies with affinities for the alpha 2A-ligand binding site of human platelet and the alpha 2B-ligand binding site of rat kidney. 2. The alpha 2B-selective adrenoceptor antagonists, prazosin, ARC 239 and HV 723 showed high, and the alpha 2A-selective antagonist BRL 44408 showed low, potency in human saphenous vein. 3. Potency in human saphenous vein correlated better with affinity for the alpha 2B-ligand binding site (r = 0.71, n = 12, P less than 0.01) than with affinity for the alpha 2A-ligand binding site (r = 0.56, n = 12, non significant). 4. It is concluded that the postjunctional alpha 2-adrenoceptor of human saphenous vein resembles an alpha 2B-ligand binding site more than an alpha 2A-ligand binding site.  相似文献   
9.
Intestinal schistosomiasis japonica: CT-pathologic correlation   总被引:1,自引:0,他引:1  
  相似文献   
10.
1. We have investigated the mechanism of regulation of 5-HT3 receptor channel sensitivity in voltage-clamped (-80 mV) NG108-15 neuroblastoma cells. 2. The 5-HT-induced inward current activated rapidly. The fast onset was followed by a biphasic decay which was characterized by two time constants, tau 1 (1.1 +/- 0.21s) and tau 2 (8.9 +/- 1.6s), respectively. Brief applications of 5-HT, applied at 2 min intervals, induced a decrease in the amplitude of the 5-HT3 receptor-mediated peak inward currents. 3. Buffering of intracellular calcium with the calcium chelator BAPTA (10 mM) instead of EGTA (10 mM) attenuated the 5-HT-induced loss of responsiveness of 5-HT3 receptors. Omission of calcium from the extracellular medium yielded a similar attenuation of loss of responsiveness. 4. Inclusion of the protein kinase inhibitor, staurosporine (1 microM) or of okadaic acid (1 microM), an inhibitor of protein phosphatases 1 and 2A, in the intracellular buffer solution did not affect 5-HT3 receptor sensitivity. 5. Injection of cyclosporin A-cyclophilin A complex (20 nM), which potently inhibits calcineurin, did not affect the time constants of the biphasic decay of the 5-HT response tau 1 (1.4 +/- 0.28s) and tau 2 (11.3 +/- 1.7s). The complex, however, prevented the loss of 5-HT3, receptor responsiveness upon repeated application of 5-HT. A similar, but weaker effect was observed after intracellular application of the autoinhibitory peptide domain of calcineurin (1 microM). 6. The recovery of desensitized 5-HT3 receptors upon a second application of 5-HT (1 microM) showed a half-life time (tau 1/2) of 2.6 +/- 0.12 min in control cells which was reduced to 1.6 +/- 0.09 min in cells treated with cyclosporin A-cyclophilin A (20 nM) complex. 7. We conclude that calcineurin does not affect the fast decay of the 5-HT3 receptor response but may be involved in a slower process which regulates channel activity.  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