全文获取类型
收费全文 | 12634篇 |
免费 | 978篇 |
国内免费 | 160篇 |
专业分类
耳鼻咽喉 | 104篇 |
儿科学 | 280篇 |
妇产科学 | 583篇 |
基础医学 | 1549篇 |
口腔科学 | 168篇 |
临床医学 | 1384篇 |
内科学 | 2750篇 |
皮肤病学 | 160篇 |
神经病学 | 959篇 |
特种医学 | 743篇 |
外科学 | 1663篇 |
综合类 | 241篇 |
一般理论 | 3篇 |
预防医学 | 684篇 |
眼科学 | 257篇 |
药学 | 933篇 |
中国医学 | 68篇 |
肿瘤学 | 1243篇 |
出版年
2023年 | 74篇 |
2022年 | 132篇 |
2021年 | 311篇 |
2020年 | 185篇 |
2019年 | 329篇 |
2018年 | 383篇 |
2017年 | 259篇 |
2016年 | 252篇 |
2015年 | 400篇 |
2014年 | 497篇 |
2013年 | 691篇 |
2012年 | 930篇 |
2011年 | 884篇 |
2010年 | 550篇 |
2009年 | 516篇 |
2008年 | 727篇 |
2007年 | 660篇 |
2006年 | 629篇 |
2005年 | 658篇 |
2004年 | 597篇 |
2003年 | 494篇 |
2002年 | 436篇 |
2001年 | 388篇 |
2000年 | 329篇 |
1999年 | 335篇 |
1998年 | 106篇 |
1997年 | 80篇 |
1996年 | 72篇 |
1995年 | 75篇 |
1994年 | 51篇 |
1993年 | 48篇 |
1992年 | 189篇 |
1991年 | 157篇 |
1990年 | 134篇 |
1989年 | 109篇 |
1988年 | 123篇 |
1987年 | 122篇 |
1986年 | 106篇 |
1985年 | 112篇 |
1984年 | 106篇 |
1983年 | 53篇 |
1982年 | 43篇 |
1981年 | 28篇 |
1980年 | 27篇 |
1979年 | 49篇 |
1978年 | 42篇 |
1977年 | 35篇 |
1975年 | 45篇 |
1974年 | 34篇 |
1973年 | 27篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Natural killer cell activity in patients with urologic cancer 总被引:1,自引:0,他引:1
Cell-mediated cytotoxicity in patients with urologic cancer was studied using the K562 cell line as target cell by a 4-hour chromium-51 release assay. Lysis of target cells by mononuclear cells of a healthy subject, over an 8-hour incubation period, demonstrated a linear function of incubation time and effector:target ratio. Natural killer (NK) cell activity was found decreased (mean 30.6%) in peripheral blood lymphocytes from 42 untreated patients with urologic cancer when compared to 20 healthy subjects (63.6%) and to 10 patients with varicocele, stone disease and benign prostatic hypertrophy (58.1%; p less than 0.05). There was no correlation between NK cell activity and the grade or stage status in bladder cancer patients. No age-dependent changes in NK cell activity could be found between young and aged groups of healthy subjects. Healthy male subjects have higher levels of NK cell activity (77.7%) than healthy female subjects (49.5%). Postoperative NK activity rose in 5 out of 6 cancer patients. It indicates that tumors may have an inhibitory effect on the surveillance activity of NK cells. 相似文献
992.
T Ohmori T Koyama C C Chen E K Yeh B V Reyes I Yamashita 《Progress in neuro-psychopharmacology & biological psychiatry》1986,10(2):229-235
It is known that aldehyde dehydrogenase (ALDH) responsible for metabolism of acetaldehyde deriving from ethanol has two distinct forms of isozymes: ALDH-I (low Km ALDH) and ALDH-II (high Km ALDH), and that many Orientals lack ALDH-I isozyme genetically. In the present study, the role of ALDH isozyme variance in the alcohol sensitivity, drinking habits formation and the development of alcoholism was investigated in Japan, Taiwan and the Phillipines. Isozyme analysis using isoelectric focusing of hair roots specimens from normal volunteers or schizophrenics revealed that about 42% of Japanese, 35% of Taiwanese and 12% of Phillipines were ALDH-I deficient. Questionnaire study of Japanese volunteers indicated that ALDH-I deficient individuals showed flushing, palpitation and other uncomfortable somatic signs, due to reduced metabolism of acetaldehyde, much more frequently than ALDH-I positive ones. Consequently, it occurred that only 19% (8/42) of ALDH-I deficient persons, in contrast to 49% (29/59) of ALDH-I positive ones, were drinking habitually. Patients with alcoholism showed much smaller percentages of ALDH-I deficiency: 4% (5/113) in Japan and 10% (3/29) in Taiwan, than those of control subjects. Summarizing these data, a hypothesis can be presented that genetically derived difference of ALDH activities is one of the determining factors in the sensitivity to alcohol, formation of drinking habits, and finally in the development of alcoholism, at least among Oriental peoples. 相似文献
993.
Extraosseous localization of bone-seeking radiopharmaceuticals has been reported in various tumors, presumably on the basis of active calcium deposition in the tumors. We report a case of oat cell carcinoma in which the initial localization of Tc-99m-HMDP in the tumor disappeared after irradiation and chemotherapy. The disappearance of tracer uptake coincided with regression of the mass as seen in the chest radiograph. This finding may have potential application in determining tumor response to anticancer therapy. 相似文献
994.
Chun-Chuan Shih Yi-Chang Su Chien-Chang Liao Jaung-Geng Lin 《BMC health services research》2010,10(1):191
Background
Medical pluralism (MP) can be defined as the employment of more than one medical system or the use of both conventional and complementary and alternative medicine (CAM) for health and illness. A population-based survey and linkage with medical records was conducted to investigate MP amongst the Taiwanese population. Previous research suggests an increasing use of CAM worldwide. 相似文献995.
996.
When a DNA probe hybridizes a DNA target and generates a G/A mismatch in the probe-target DNA heteroduplex, the mismatch enzyme, mutY, will cut the A base at the site of the mismatch. This specific cleavage at the mismatched A on the known probe will reveal the complementary DNA sequences of the targets. This study shows mismatch cleavage assays identify the complementary sequence of cryptic plasmid target in the extract of chlamydia infected cells in culture. In addition, the specific cleavage at a single base permits differentiation of two sequences with one base difference. This was shown in differentiating the subtypes of human immunodeficiency virus (HIV) type 1. The addition of amines in the assays increases the sensitivity by freeing the target for recycling. The combined assay system of high sensitivity and demonstrated specificity allows further evaluation for direct identification of pathogenic microorganisms in patient samples. 相似文献
997.
Jian‐Liang Fu Hong‐Mei Zhang Hua Zhang Amrita Kamat Chih‐Ko Yeh Bin‐Xian Zhang 《Journal of pineal research》2013,55(4):364-370
Mitochondrial complex III (MC‐3) plays a pivotal role in electron transfer and oxidative phosphorylation. Impaired MC‐3 functions may contribute to a variety of diseases by interrupting normal bioenergetics and increasing reactive oxygen production and oxidative stress. Currently, MC‐3 function is assessed by measuring the cytochrome c reductase activity spectrophotometrically in isolated mitochondria or MC‐3. The cytoplasmic microenvironment critical for mitochondrial complex functions may be depleted during these isolation processes. The development of a reliable method to measure MC‐3 activities in intact cells or tissues is highly desirable. This report describes a novel fluorescence‐based method to assess MC‐3 functions, i.e., Qi site electron transfer, in the intact cells. Human mesangial and teratocarcinoma NT2 cells were used to demonstrate that melatonin‐induced oxidation of 2′,7′‐dichlorodihydrofluorescein (H2DCF) was inhibited by antimycin A, the MC‐3 Qi site‐specific inhibitor, but not by myxothiazol, the MC‐3 Qo site‐specific inhibitor, nor rotenone, the mitochondrial complex I inhibitor. These results indicate that melatonin‐induced oxidation of H2DCF is reflecting MC‐3 Qi site electron transfer activities. Modifying structures of the side groups at the R3 and R5 positions of the indole ring of melatonin diminished its efficacy for inducing H2DCF oxidation, suggesting a specific interaction of melatonin with the MC‐3 Qi site. These results suggest that the fluorogenic property of melatonin‐induced H2DCF oxidation provides a MC‐3 Qi site electron transfer‐specific measurement in intact cells. Interestingly, using this method, the Qi site electron transfer activity in transformed or immortalized cells was found to be significantly higher than the nontransformed cells. 相似文献
998.
SUMMARY: Recent studies have suggested that green tea polyphenols (GTP) are promising agents for preventing bone loss in women. Findings that GTP supplementation resulted in increased urinary GTP concentrations and bone mass via an increase of antioxidant capacity and/or a decrease of oxidative stress damage suggest a significant role of GTP in bone health of women. INTRODUCTION: Recent studies suggested that green tea polyphenols (GTP) are promising agents for preventing bone loss in women. However, the mechanism related to the possible protective role of GTP in bone loss is not well understood. METHODS: This study evaluated bioavailability, mechanisms, bone mass, and safety of GTP in preventing bone loss in middle-aged rats without (sham, SH) and with ovariectomy (OVX). A 16-week study of 2 (SH vs. OVX) x 3 (no GTP, 0.1% GTP, and 0.5% GTP in drinking water) factorial design using 14-month-old female rats (n = 10/group) was performed. An additional 10 rats in baseline group were euthanized at the beginning of study to provide baseline parameters. RESULTS: There was no difference in femur bone mineral density between baseline and the SH+0.5% GTP group. Ovariectomy resulted in lower values for liver glutathione peroxidase activity, serum estradiol, and bone mineral density. GTP supplementation resulted in increased urinary epigallocatechin and epicatechin concentrations, liver glutathione peroxidase activity and femur bone mineral density, decreased urinary 8-hydroxy-2'-deoxyguanosine and urinary calcium levels, but no effect on serum estradiol and blood chemistry levels. CONCLUSION: We conclude that a bone-protective role of GTP may contribute to an increase of antioxidant capacity and/or a decrease of oxidative stress damage. 相似文献
999.
Yu-Chang Yeh Tzu-Fu Lin Chen-Hua Wang Yong-Ping Wang Chen-Jung Lin Wei-Zen Sun 《台湾医志》2008,107(6):478-484
BACKGROUND/PURPOSE: Admixing an ultralow dose of naloxone with intravenous morphine patient-controlled analgesia (PCA) has been shown to decrease postoperative nausea. However, the cut-off ratio of the naloxone-morphine admixture for antiemetic effects has not been investigated. The purpose of this study was to investigate the cut-off ratio of naloxone-morphine admixture in PCA for antiemesis after gynecologic surgery. METHODS: This double-blind study enrolled 120 female patients who were scheduled for gynecologic surgery under general anesthesia. Patients were randomly allocated to one of three groups (n = 40 for each group). The concentration of naloxone and morphine respectively was 0 microg/mL and 1 mg/mL in group 1, 0.1 microg/mL and 1 mg/mL in group 2 (1:10,000), and 1 microg/mL and 1 mg/mL in group 3 (1:1000). Morphine consumption, verbal rating score of wound pain at rest and with exertion, and morphine-related side effects were investigated at 1, 2, 4 and 24 hours postoperatively. RESULTS: A total of 112 patients completed the study (37 in group 1, 36 in group 2, 39 in group 3). The incidence of nausea during the postoperative 4-24 hours was significantly lower in group 3 than in group 1 (23.1% vs. 56.8%, p < 0.05). Furthermore, the overall incidence of severe nausea was significantly lower in group 3 than in group 1 (2.6% vs. 24.3%, p < 0.05) as was the rescue antiemetic requirements (5.1% vs. 24.3%, p < 0.05). However, there were no significant differences between groups 2 and 1. The pain scores (at rest and with exertion) and 24-hour morphine consumption were not significantly different among the three groups. CONCLUSION: The antiemetic efficacy of ultralow-dose naloxone combined with PCA morphine is limited by a cut-off ratio of naloxone to morphine of 1:10,000. 相似文献
1000.
H H Shih S N Chen 《The Southeast Asian journal of tropical medicine and public health》1990,21(3):475-481
Juvenile worms of Angiostrongylus cantonensis recovered from subarachnoid spaces and pulmonary arteries of rats, respectively, at 28 days post-infection have been compared with respect to their surface composition, antigenicity of surface proteins and morphological appearance. Quantitative and qualitative differences were shown between surface proteins of these two stages of worms. One major and 6 minor proteins appeared on brain stage worm's surface as assessed by surface-labelling and SDS-PAGE techniques. The same, but more predominant banding pattern, with one additional major protein of Mr 80,000 kDa presented on the lung stage worm's surface. Surface components from both stages were antigenic in permissive rat hosts but refractory in nonpermissive human hosts. The surface antigens are common to both stages within the rat. Observed by scanning electron microscopy, the surface appearance of brain stage worms is thickened, rough and irregular. Besides, particle clusters adhere randomly, without cluster adherence but transverse and longitudinal clefts were shown on the surface, before the outer layer was shed. The possible mechanisms of evasion from the host's immune attack with the surface-shedding phenomenon remain to be elucidated. 相似文献