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   28924篇
  免费   1653篇
  国内免费   152篇
耳鼻咽喉   362篇
儿科学   940篇
妇产科学   612篇
基础医学   4090篇
口腔科学   2058篇
临床医学   2637篇
内科学   5658篇
皮肤病学   716篇
神经病学   2622篇
特种医学   1113篇
外国民族医学   4篇
外科学   3035篇
综合类   361篇
一般理论   21篇
预防医学   2728篇
眼科学   465篇
药学   1844篇
  5篇
中国医学   244篇
肿瘤学   1214篇
  2023年   269篇
  2022年   534篇
  2021年   939篇
  2020年   624篇
  2019年   781篇
  2018年   994篇
  2017年   724篇
  2016年   748篇
  2015年   927篇
  2014年   1249篇
  2013年   1479篇
  2012年   2107篇
  2011年   2065篇
  2010年   1211篇
  2009年   1050篇
  2008年   1484篇
  2007年   1585篇
  2006年   1351篇
  2005年   1347篇
  2004年   1299篇
  2003年   1134篇
  2002年   972篇
  2001年   613篇
  2000年   578篇
  1999年   491篇
  1998年   232篇
  1997年   196篇
  1996年   149篇
  1995年   139篇
  1994年   116篇
  1993年   122篇
  1992年   256篇
  1991年   261篇
  1990年   240篇
  1989年   211篇
  1988年   235篇
  1987年   201篇
  1986年   159篇
  1985年   160篇
  1984年   130篇
  1983年   90篇
  1982年   83篇
  1981年   67篇
  1980年   65篇
  1979年   110篇
  1978年   87篇
  1975年   67篇
  1974年   86篇
  1973年   87篇
  1971年   73篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
Long-term dopamine replacement therapy of Parkinson's disease leads to the occurrence of dyskinesias. Altered firing patterns of neurons of the internal globus pallidus, involving a pathological synchronization/desynchronization process, may contribute significantly to the genesis of dyskinesia. Levetiracetam, an antiepileptic drug that counteracts neuronal (hyper)synchronization in animal models of epilepsy, was assessed in the MPTP-lesioned marmoset model of Parkinson's disease, after coadministration with (1) levodopa (L-dopa) or (2) ropinirole/L-dopa combination. Oral administration of levetiracetam (13-60 mg/kg) in combination with either L-dopa (12 mg/kg) alone or L-dopa (8 mg/kg)/ropinirole (1.25 mg/kg) treatments was associated with significantly less dyskinesia, in comparison to L-dopa monotherapy during the first hour after administration. Thus, new nondopaminergic treatment strategies targeting normalization of abnormal firing patterns in basal ganglia structures may prove useful as an adjunct to reduce dyskinesia induced by dopamine replacement therapy without affecting its antiparkinsonian action.  相似文献   
24.
We report on a boy with severe radial hypoplasia, absent thumbs and patellae, short stature, persistent diarrhea, slender nose and normal intelligence as another example of the RAPADILINO syndrome. © 1992 Wiley-Liss, Inc.  相似文献   
25.
This study was undertaken to explore early differences in cytokine production during nonlethal and lethal blood-stage murine malaria infections. Cytokine analysis of spleens during these infections showed that the principal difference between two nonlethal and two lethal Plasmodium species was the production of gamma interferon 24 h after infection with nonlethal parasites. In contrast, no increases in interleukin-4 production were observed in the first 24 h and tumor necrosis factor alpha levels increased equally in both nonlethal and lethal infections. During the later phase of infection with nonlethal parasites, both gamma interferon and interleukin-4 levels increased markedly a few days before parasite clearance. Early increases in gamma interferon production in nonlethal infections of Plasmodium yoelii and Plasmodium chabaudi were dose related and increased significantly with the size of the inoculum. Studies with the nonlethal P. yoelii suggest that the early gamma interferon response is mediated by T cells and natural killer cells, as it was reduced in athymic mice and in mice depleted of their natural killer cells by treatment with specific antiserum. Infecting mice with increasing numbers of lethal P. yoelii and Plasmodium berghei parasites did not increase the amount of gamma interferon, interleukin-4, and tumor necrosis factor alpha produced in a dose-dependent fashion. We conclude that one consequence of the early production of gamma interferon and tumor necrosis factor-alpha, particularly after nonlethal P. yoelii infection, may be to adjust the balance of T-helper cell subset activation, and probably that of other immune responses, so as to enhance the mechanisms that are essential for elimination of the parasites. This suggests that a successful vaccine should contain antigens capable of inducing such responses.  相似文献   
26.
27.
28.
OBJECTIVES: This article examines the differences found between clientele with severe mental health problems and their key health workers in terms of assessing service users' needs in 6 Quebec service areas. METHOD: We questioned 165 pairs of users and staff, using the Camberwell Assessment of Needs questionnaire. The profile of serious and overall problems encountered by clientele from each of the sites was compared. RESULTS: The sites with the greatest degree of user-staff agreement in identifying problems were also the ones where users considered that local services best met their needs. CONCLUSIONS: The study demonstrated that, in needs assessment, major differences exist between the perceptions of users and their key workers in the various sites. These differences can be explained in part by users' individual characteristics, by types of needs, by local particularities, and by service use.  相似文献   
29.
A combination of psyllium fiber with nutrients in a commercially available wafer (Fiberall-Ciba Consumer Pharmaceutical) was evaluated for its effectiveness in reducing food intake and appetite. Each of 15 nonobese healthy women received no wafers and four different amounts (39, 104, 169, and 234 kcal) of the fiber wafer with water, in a ratio of 13 kcal (and 0.565 g psyllium) wafer per 41.67 g water, 30 minutes prior to a test meal of macaroni and beef, on nonconsecutive days. Intake of the test meal and hunger ratings were both significantly reduced after intake of the two largest wafer amounts (169 and 234 kcal, respectively), in comparison with the two smaller amounts and none at all. The reduction produced by the largest amount compared to none at all was 122 kcal (about half the energy of the amount given). There were no significant differences in intake and hunger ratings among the two smaller amounts and none at all. Thus the threshold for intake reduction by this product with water lies between 104 and 169 kcal. Methodologically, this work underscores the importance of testing the satiating effects of foods at multiple levels before conclusions are drawn about their satiating effectiveness, and suggests that the threshold for significant reduction should be considered as a measure of the product's satiating effectiveness. The relative contributions of the nutrients, the fiber, and the water to the satiating effect still need to be determined.  相似文献   
30.
ADP plays a key role in thrombogenesis in rats   总被引:3,自引:0,他引:3  
The relative importance of ADP, arachidonic acid metabolites and serotonin as thrombogenic factors was evaluated in rats by comparing, after oral administration, the effects of two inhibitors of ADP-induced platelet aggregation (ticlopidine and PCR 4099), three cyclo-oxygenase inhibitors (aspirin, triflusal and indobufen) and a selective serotonin 5HT2 receptor antagonist (ketanserin) on platelet aggregation, in four platelet-dependent thrombosis models and on bleeding time. Platelet aggregation induced by ADP and collagen was completely inhibited by ticlopidine and PCR 4099 whereas only the collagen aggregation was reduced by the cyclo-oxygenase inhibitors. Ketanserin or a depletion of platelet serotonin by reserpine did not affect platelet aggregation. Ticlopidine and PCR 4099 greatly prolonged rat tail transection bleeding time. This is probably related to their known ability to inhibit ADP-mediated platelet aggregation. In contrast, the cyclooxygenase inhibitors did not affect bleeding time at all. Reserpine and ketanserin prolonged bleeding time by interfering with the action of serotonin on the vascular wall. Ticlopidine and PCR 4099 were very potent antithrombotics in all the models. Aspirin, only at a high dose, inhibited poorly thrombus formation on a silk thread in an arterio-venous shunt, suggesting that the inhibition of cyclo-oxygenase was not responsible. Triflusal was inactive in all models while indobufen slightly reduced thrombus formation in the silk thread and metallic coil models. Ketanserin and reserpine reduced thrombus only in the metallic coil model. Thrombus formation was greatly reduced in fawn-hooded rats, which lack ADP in their platelet dense granules because of a genetic storage pool deficiency.(ABSTRACT TRUNCATED AT 250 WORDS)  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