全文获取类型
收费全文 | 17034篇 |
免费 | 1646篇 |
国内免费 | 636篇 |
专业分类
耳鼻咽喉 | 258篇 |
儿科学 | 176篇 |
妇产科学 | 345篇 |
基础医学 | 1448篇 |
口腔科学 | 466篇 |
临床医学 | 1532篇 |
内科学 | 1851篇 |
皮肤病学 | 102篇 |
神经病学 | 713篇 |
特种医学 | 690篇 |
外国民族医学 | 8篇 |
外科学 | 3197篇 |
综合类 | 2849篇 |
现状与发展 | 4篇 |
一般理论 | 1篇 |
预防医学 | 928篇 |
眼科学 | 138篇 |
药学 | 2197篇 |
27篇 | |
中国医学 | 989篇 |
肿瘤学 | 1397篇 |
出版年
2024年 | 35篇 |
2023年 | 248篇 |
2022年 | 437篇 |
2021年 | 622篇 |
2020年 | 563篇 |
2019年 | 539篇 |
2018年 | 636篇 |
2017年 | 591篇 |
2016年 | 631篇 |
2015年 | 582篇 |
2014年 | 1018篇 |
2013年 | 1229篇 |
2012年 | 923篇 |
2011年 | 977篇 |
2010年 | 778篇 |
2009年 | 749篇 |
2008年 | 818篇 |
2007年 | 715篇 |
2006年 | 721篇 |
2005年 | 651篇 |
2004年 | 649篇 |
2003年 | 614篇 |
2002年 | 579篇 |
2001年 | 448篇 |
2000年 | 426篇 |
1999年 | 367篇 |
1998年 | 366篇 |
1997年 | 302篇 |
1996年 | 292篇 |
1995年 | 274篇 |
1994年 | 233篇 |
1993年 | 199篇 |
1992年 | 166篇 |
1991年 | 162篇 |
1990年 | 114篇 |
1989年 | 98篇 |
1988年 | 69篇 |
1987年 | 63篇 |
1986年 | 41篇 |
1985年 | 54篇 |
1984年 | 54篇 |
1983年 | 39篇 |
1982年 | 34篇 |
1981年 | 23篇 |
1980年 | 23篇 |
1979年 | 19篇 |
1978年 | 25篇 |
1977年 | 23篇 |
1976年 | 18篇 |
1975年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
J. J. HOORWEG J. A. RAUWERDA G. A. CROLL A. J. C. MACKAAY E. K. J. RISSE N. DE VRIES R. M. TIWARI 《Clinical otolaryngology》1994,19(6):496-501
The records of 28 patients who underwent free jejunal graft reconstruction after resection for cancer involving the pharynx were analysed. Seven patients had a T3 carcinoma, 15 patients T4 and six patients recurrence after laryngectomy. Ten patients had received radiotherapy in the past. Post-operatively, 15 patients (54%) had complications and two patients (7%) died. No significant difference was observed in the complication rate between the group that received radiotherapy in the past and those who did not. Nineteen patients received post-operative radiotherapy. Nine patients had no radiotherapy on the basis of complete resection or because of serious complications. For the whole group the 2-year recurrence free period and survival were 42% and 51% respectively. The postoperative radiotherapy group had a significantly better survival (73%) and recurrence free period (63%) than the group without post-operative radiotherapy (0%). Thus, post-operative radiotherapy seems indicated irrespective of resection margins. 相似文献
32.
林劲秋 《南方医科大学学报》2002,22(6):530-532
目的探讨外源性补充抗氧化性维生素对骨髓移植病人抗氧化力及脂质过氧化的影响。方法将19名骨髓移植病人随机分为实验和对照组,实验组在预处理前给予维生素C(300 mg/d)和维生素E(600 mg/d),对照组不予补充,其余处理两者相同。测定移植前后两组病人的血浆总抗氧化力、丙二醛、全血谷胱甘肽过氧化物酶及红细胞超氧化物歧化酶水平。结果(1)移植前后实验组血浆总抗氧化力、谷胱甘肽过氧化物酶和红细胞超氧化物歧化酶值一直处于正常或正常值附近,对照组则低于正常值,两组相比有显著差异;(2)移植后实验组丙二醛值很快降至正常,对照组则一直处于较高水平,两组有显著差异。结论移植前外源性补充抗氧化性维生素可提高骨髓移植病人机体的抗氧化力,减少了脂质过氧化物的产生,有效缓解移植前大剂量放、化疗对病人机体造成的高氧化胁迫压力。 相似文献
33.
Carl Ganter 《Magnetic resonance in medicine》2004,52(2):368-375
A previously developed eigenvector formalism is adapted to off-resonance in the transient response of quasiperiodic steady-state free precession (SSFP) sequences, including TrueFISP as a special case. The effective relaxation rates for essentially parallel and perpendicular deviations from the steady state are determined analytically in leading order perturbation theory. The latter are a known cause of oscillatory artifacts and therefore constitute the main target of a variety of preparation techniques. In addition, the former also play a dominating role in applications such as inversion recovery (IR) TrueFISP, which intentionally measure far away from the equilibrium. For both components, the approach toward equilibrium turns out to depend sensitively on field inhomogeneities, especially for smaller ratios of T2/T1. For the perpendicular deviations, the calculations show that--except very close to banding artifacts, where the steady-state signal is almost zero--field inhomogeneities additionally increase their effective relaxation rate almost as much as in the free induction decay (FID). The analytical results are tested against numerical simulation and MR measurements. 相似文献
34.
Magnetization prepared segmented acquisition requires a view order that maximizes signal contrast during the acquisition of the central portion of k-space. Steady state free precession (SSFP) acquisition further requires a view order that minimizes changes in phase-encoding gradients from one repetition to the next in order to minimize eddy current artifacts. In this article, optimal view ordering schemes satisfying these two requirements are formulated and applied to inversion prepared 3D SSFP contrast-enhanced MR angiography (MRA). Experiments on phantoms and pigs demonstrated improved background suppression and reduced image artifacts. 相似文献
35.
汉防己甲素抑制三种神经递质引起的新生大鼠脑细胞内游离钙的升高 总被引:1,自引:0,他引:1
《中国药理学通报》1995,(3)
应用Pura-2技术测定游离新生大鼠脑[Ca2+]i浓度的技术、研究了Tet对静息脑[Ca2+]i和3种递质引起的脑[Ca2]i变化的影响。Tet(1,10和20μmol·L-1)对静息脑[Ca2+]i无明显影响。Tet(10μmol·L-1)可降低L-Gln(0.1、1.0和10μmol·L-1)引起的脑(Ca2+)i的升高。在Hank's液Ca2+为1.3mmol·L-1时,Tet10μmol·L-1可降低His(50和100μmol·L-1)和5-HT(0.1、1.0、10和100μmol·L-1)引起的脑[Ca2+]i的升高。但不能降低Hank's液无Ca2+时His和5-HT引起的脑[Ca2+]i的升高。研究表明Tet可阻滞L-Gin、His和5-HT受体调控的钙通道。但对His和5-HT引起的细胞内贮存钙的释放并无明显影响。Tet的这种降低脑[Ca2+]i的作用可能是其治疗脑缺血性疾病的机理之一。P<0.01在Tet10μmol·L-1作用下,相同浓度的细胞外液钙和His(0、50和100μmol·L-1),脑[Ca2+]i分别是221±5、245±5和302±6nmol·L-1。增加了11.8? 相似文献
36.
本文报道1000例正常人发自由基的电子自旋共振波谱饱和功率(ESR-SP)的检测结果。所得正常值的全组中位数为2.496mw;95%上下限分别为2.989及1.720mw。如按性别统计,则女性下限(1.617mw)较男性(1.983mw)为低,(P<0.05)。按年龄分别统计,则40岁以上的中位数(2.376mw)及其下限(2.009mw)高于40岁以下的中位数(2.548mw)及其下限(1.597mw),两者差异有显著性(P<0.05)及极显著性(P<0.01)。因此在使用此正常值指标时,必须注意性别与年龄因素。 相似文献
37.
The effects of combined use of earthworm extract(912)and HpD-laser on the produc-tion of reactive oxygen and the biosynthesis of DNA in S_(180) tumor cells were studied throughchemiluminescence measurement and[~3H]-TdR incorporation assay.The results showed that as com-pared with the control,the intensity of chemiluminescence emitted by tumor cells treatedsimultaneously with 912 and HpD-laser was enhanced more than ten-folds,while that treated with912 or HpD-laser alone was increased only 2~4 folds.The[~3H]-TdR incorporation into tumorcells of the former group was inhibited upto 74.1%,and that of the latter groups decreased onlyby 42.2% and 40.0%,respectively.In accordance with these biochemical changes,the ultrastructuraldamage of tumor cells of the former,combinedly treated group appeared to be the most serious.This suggests an additive effect of 912 with HpD-laser on tumor cells.In addition,if free radicalscavengers,such as catalase and superoxide dismutase,were added to the reaction systembefore chemiluminescence assay,the luminescent enhancement effect mentioned above was dramaticallyalleviated,implying the presence of O_2~ and H_2O_2 in the system.Therefore,as to the toxic effecton tumor cells,912 and HpD-laser are not only additive in efficiency,but also similar in theunderlying mechanism of action. 相似文献
38.
Shun'Ichi Abe Hiroshi Yoshimura Hideki Tabara Mitsuo Tachibana Naomi Monden Teruhisa Nakamura Saburou Nagaoka 《Journal of surgical oncology》1995,59(4):226-229
Patients with stage T3N0~2M0 gastric carcinoma (n = 108) were studied for relevant prognostic factors. Peritoneal lavage cytology (PLC) was performed in all. In univariate analysis, 5-year survival rates were better with smaller serosal invasion (diameter <3.0 cm vs. ≥3.0 cm, 61% vs. 37%, P < 0.05) and fewer metastatic nodes (≤5 vs. ≥6, 57% vs. 29%, P < 0.05). In multivariate analyses, only these two factors were significant. The predictive value of PLC was not shown in both univariate and multivariate analyses. Peritoneal recurrence occured in 14 (22%) of 77 patients with negative PLC, and in 3 (18%) of 17 with positive PLC, the difference being not significant. Our results indicate that PLC is insensitive in predicting the development of peritoneal recurrence. Its role in the estimation of survival is limited, as many will die of visceral or locoregional recurrence if not of peritoneal dissemination. 相似文献
39.
A M Abdel Gader A A Al-Mishari S A Awadalla N M Buyuomi T Khashoggi M Al-Hakeem 《International journal of gynaecology and obstetrics》2006,95(3):248-253
OBJECTIVE: To clarify the role played by tissue factor pathway inhibitor (TFPI) in pregnancy hypertension. METHODS: Using enzyme-linked immunosorbent assays, hemostatic measurements were obtained for women with pre-eclampsia (n=51), nonproteinuric hypertension of pregnancy (n=62), postpartum pre-eclampsia 24 h after childbirth (n=31), and no hypertension (healthy pregnant controls, n=100). RESULTS: There was a significant increase in circulating free TFPI levels in women with pre-eclampsia (9.7+/-6.2 ng/mL) or nonproteinuric hypertension of pregnancy (8.3+/-5.3 ng/mL) compared with healthy controls (5.3+/-2.1 ng/mL). In women with pre-eclampsia the levels remained elevated after placental delivery (10.6+/-4.0 ng/mL). Free protein S levels were significantly higher in women with pre-eclampsia (40.0%+/-10.7%), nonproteinuric hypertension of pregnancy (37.1%+/-12.5%), or postpartum pre-eclampsia (39.3%+/-9.1%) than in healthy pregnant controls (32.2%+/-8.5%). CONCLUSION: Increased levels of the physiologically active free forms of TFPI and free protein S, 2 coagulation inhibitors, may protect women with pregnancy-induced hypertension from the risks of hemostatic activation. 相似文献
40.
Multicoil Dixon chemical species separation with an iterative least-squares estimation method. 总被引:1,自引:0,他引:1
Scott B Reeder Zhifei Wen Huanzhou Yu Angel R Pineda Garry E Gold Michael Markl Norbert J Pelc 《Magnetic resonance in medicine》2004,51(1):35-45
This work describes a new approach to multipoint Dixon fat-water separation that is amenable to pulse sequences that require short echo time (TE) increments, such as steady-state free precession (SSFP) and fast spin-echo (FSE) imaging. Using an iterative linear least-squares method that decomposes water and fat images from source images acquired at short TE increments, images with a high signal-to-noise ratio (SNR) and uniform separation of water and fat are obtained. This algorithm extends to multicoil reconstruction with minimal additional complexity. Examples of single- and multicoil fat-water decompositions are shown from source images acquired at both 1.5T and 3.0T. Examples in the knee, ankle, pelvis, abdomen, and heart are shown, using FSE, SSFP, and spoiled gradient-echo (SPGR) pulse sequences. The algorithm was applied to systems with multiple chemical species, and an example of water-fat-silicone separation is shown. An analysis of the noise performance of this method is described, and methods to improve noise performance through multicoil acquisition and field map smoothing are discussed. 相似文献