全文获取类型
收费全文 | 25721篇 |
免费 | 1922篇 |
国内免费 | 101篇 |
专业分类
耳鼻咽喉 | 217篇 |
儿科学 | 587篇 |
妇产科学 | 400篇 |
基础医学 | 3498篇 |
口腔科学 | 328篇 |
临床医学 | 2762篇 |
内科学 | 5790篇 |
皮肤病学 | 312篇 |
神经病学 | 2319篇 |
特种医学 | 848篇 |
外科学 | 4253篇 |
综合类 | 277篇 |
现状与发展 | 1篇 |
一般理论 | 25篇 |
预防医学 | 1886篇 |
眼科学 | 403篇 |
药学 | 1779篇 |
中国医学 | 44篇 |
肿瘤学 | 2015篇 |
出版年
2023年 | 259篇 |
2022年 | 453篇 |
2021年 | 996篇 |
2020年 | 513篇 |
2019年 | 811篇 |
2018年 | 926篇 |
2017年 | 649篇 |
2016年 | 665篇 |
2015年 | 759篇 |
2014年 | 1041篇 |
2013年 | 1307篇 |
2012年 | 2064篇 |
2011年 | 2087篇 |
2010年 | 1118篇 |
2009年 | 968篇 |
2008年 | 1609篇 |
2007年 | 1602篇 |
2006年 | 1461篇 |
2005年 | 1415篇 |
2004年 | 1342篇 |
2003年 | 1247篇 |
2002年 | 1224篇 |
2001年 | 180篇 |
2000年 | 141篇 |
1999年 | 217篇 |
1998年 | 247篇 |
1997年 | 202篇 |
1996年 | 160篇 |
1995年 | 159篇 |
1994年 | 160篇 |
1993年 | 126篇 |
1992年 | 112篇 |
1991年 | 76篇 |
1990年 | 95篇 |
1989年 | 69篇 |
1988年 | 72篇 |
1987年 | 90篇 |
1986年 | 76篇 |
1985年 | 64篇 |
1984年 | 94篇 |
1983年 | 80篇 |
1982年 | 89篇 |
1981年 | 81篇 |
1980年 | 84篇 |
1979年 | 49篇 |
1978年 | 56篇 |
1977年 | 44篇 |
1975年 | 36篇 |
1974年 | 34篇 |
1973年 | 34篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Ayala Stabholz Anne A. Nicholas Grenith J. Zimmerman Ulf M. E. Wikesjö 《Journal of clinical periodontology》1998,25(10):794-800
Abstract. 15 adults, each providing 4 non-adjacent untreated periodontal pockets with a probing depth (PD) exceeding 6 mm. volunteered for a randomized, split-mouth, double-blind, clinical study evaluating subgingival irrigation with chlorhexidine (CHX) or tetracycline HCl (TTC). The study protocol included oral hygiene instructions followed by scaling and root planing. Experimental and immediately adjacent teeth did not receive instrumentation. The 4 deep periodontal pockets in each patient were assigned to be irrigated with 150 ml CHX (0.12%). TTC (10 or 50 mg/ml; TTC10, TTC50), or sterile saline (control) in a single episode. Post-irrigation mechanical plaque control was supported by 2× daily CHX rinses throughout the 12-week observation interval. Recordings of oral hygiene (PlI), gingival health (GI). bleeding on probing (BoP). probing depth (PD), clinical attachment level (CAL), and microbial morphotypes from subgingival paper point samples were performed pre-irrigation. and at 1, 2, 4, 6, 8, 10, and 12 weeks post-irrigation. Mean post-irrigation PlI was low, fluctuating between 0.0 and 0.4, without significant differences between experimental groups. Mean pre-irrigation GI approximated 1.4 and reached 0.8 at the exit of study without significant differences between experimental groups. All experimental sites exhibited BoP pre-irrigation. BoP was significantly reduced in TTC50 compared to TTC10, CHX and control sites from week 8 post-irrigation. PDs were reduced for the experimental groups with TTC50 exhibiting the strongest reduction. CALs remained unaltered from pre-irrigation for TTC10. CHX and control sites over the 12-week observation interval, whereas TTC50 sites consistently improved to significantly differ from all other groups at week 10 and 12 post-irrigation. The distribution of bacterial morphotypes was significantly altered towards one of periodontal health for all experimental groups with a profound effect for TTC50 sites. Our results suggest that subgingival irrigation with TTC solutions at high concentrations may have a rôle in the management of adult periodontitis. 相似文献
92.
93.
94.
The understanding of the term "physical fitness" was determined for a randomly selected sample (n = 94) of a population using a self-administered mailed questionnaire. Subjects were asked to state and give a reason for their perceived level of physical fitness, to state their perceived performance level in a number of physical fitness tests (muscular strength, daily physical work capacity, fatness, level of regular physical exercise, exercise speed, and body flexibility), and to rate how well these tests measure physical fitness. The reason most frequently stated for perceived level of physical fitness was the level of habitual physical activity (43%); significantly less frequently (P less than 0.01-0.0001) cited were reasons related to health (23%), physical performance (12%), and obesity (3%). The variation in perceived level of physical fitness was best explained by the variation in imagined regular exercise and fatness (r2 = 0.66, P less than 0.0001) with no significant additional contribution from imagined performance in remaining fitness tests. The measurement of regular exercise was most favored as a test of physical fitness. These results, taken together with evidence of the physical and psychological health benefits of regular exercise, imply that the most appropriate measure of physical fitness for the average person is an assessment of the habitual physical activity level. 相似文献
95.
Brian D Perkins Claire S Nicholas Lisa M Baye Brian A Link John E Dowling 《Developmental dynamics》2005,233(2):680-694
Several molecules, such as growth factors and neurotrophic factors, are required both for the differentiation of specific retinal cell types and the long-term cell survival of all retinal neurons. As diffusible factors, these molecules act non-cell-autonomously. Here, we describe the loss of function phenotype for dazed (dzd), a gene that acts cell-autonomously for retinal cell survival and affects the differentiation of rod photoreceptors and the Muller glia. By 3 days after fertilization, dazed mutant embryos have small eyes and slight heart edema. Acridine orange staining indicated a significant degree of retinal cell death occurring by 48 hr after fertilization, and histological analysis revealed that dying cells were found in the inner and outer nuclear layers and near the marginal zones. Although molecular and morphological differentiation of the inner retina and cone photoreceptors occurred, rod photoreceptors failed to differentiate beyond a small patch in the ventral retina and rod precursors failed to respond to exogenously added retinoic acid, which normally potentiated rod differentiation. Mosaic analysis indicated that the dazed gene acts cell-autonomously for rod production and cell survival, as dazed clones failed to produce rods outside the ventral patch and dazed cells were not maintained in wild-type hosts. Raising mutants under constant light resulted in severe retinal degeneration, whereas raising embryos under constant darkness did not provide any additional protection from cell death. Behavioral analysis showed that a subpopulation of adult fish that were heterozygous for the dazed mutation had elevated visual thresholds and were night blind, suggesting that dazed may also be required for long-term dim-light vision. Taken together, our studies suggest a role for the dazed gene in rod and Muller cell development and overall retinal cell survival and maintenance. 相似文献
96.
Heijmans BT Beekman M Putter H Lakenberg N van der Wijk HJ Whitfield JB Posthuma D Pedersen NL Martin NG Boomsma DI Slagboom PE 《European journal of human genetics : EJHG》2005,13(10):1143-1153
Lipid levels in plasma strongly influence the risk for coronary heart disease. To localise and subsequently identify genes affecting lipid levels, we performed four genome-wide linkage scans followed by combined linkage/association analysis. Genome-scans were performed in 701 dizygotic twin pairs from four samples with data on plasma levels of HDL- and LDL-cholesterol and their major protein constituents, apolipoprotein AI (ApoAI) and Apolipoprotein B (ApoB). To maximise power, the genome scans were analysed simultaneously using a well-established meta-analysis method that was newly applied to linkage analysis. Overall LOD scores were estimated using the means of the sample-specific quantitative trait locus (QTL) effects inversely weighted by the standard errors obtained using an inverse regression method. Possible heterogeneity was accounted for with a random effects model. Suggestive linkage for HDL-C was observed on 8p23.1 and 12q21.2 and for ApoAI on 1q21.3. For LDL-C and ApoB, linkage regions frequently coincided (2p24.1, 2q32.1, 19p13.2 and 19q13.31). Six of the putative QTLs replicated previous findings. After fine mapping, three maximum LOD scores mapped within 1 cM of major candidate genes, namely APOB (LOD=2.1), LDLR (LOD=1.9) and APOE (LOD=1.7). APOB haplotypes explained 27% of the QTL effect observed for LDL-C on 2p24.1 and reduced the LOD-score by 0.82. Accounting for the effect of the LDLR and APOE haplotypes did not change the LOD score close to the LDLR gene but abolished the linkage signal at the APOE gene. In conclusion, application of a new meta-analysis approach maximised the power to detect QTLs for lipid levels and improved the precision of their location estimate. 相似文献
97.
Kenefick RW Mahood NV Hazzard MP Quinn TJ Castellani JW 《European journal of applied physiology》2004,92(4-5):565-570
Hyperosmotic hypovolemia impairs vasoconstriction during sedentary cold exposure. The purpose of this study was to determine whether hypohydration alters thermoregulation and cardiovascular responses to exercise in cold air. On four occasions, eight males [35.1 (2.7) years, 175.5 (3.1) cm, 73.3 (2.6) kg, 57.2 (2.6) ml kg–1 min–1 maximal oxygen uptake (O2max), 19.6 (2.4)% fat] walked, in t-shirt, shorts, and shoes, at 50% O2max, for 60 min in either a 4°C (Cold) or a 25°C (Temperate) environment in both hypohydrated state (HYPO, –4% body mass) and euhydrated state (EU). During exercise–cold stress, rectal temperature (Tre), mean weighted skin temperature, heart rate (HR), cardiac output (CO), and stroke volume (SV) were measured every 20 min. Mean weighted skin temperature values were not different between HYPO and EU but were lower (P<0.05) in Cold versus Temperate trials. Tre was not different (P>0.05) between HYPO–Cold and EU–Cold. CO and SV were not different within hydration states and were not different between Cold and Temperate trials (P<0.05). HR was not different between HYPO–Cold and EU–Cold. These data demonstrate that moderate intensity exercise in the cold while hypohydrated does not alter metabolic heat production, skin temperatures and heat loss, nor does it increase thermoregulatory and cardiovascular strain. 相似文献
98.
Nicholas E Jufas Ben Roediger Patricia J Armati 《Applied immunohistochemistry & molecular morphology》2008,16(1):83-86
The use of 2 monoclonal antibodies during double immunohistochemistry would enable the use of a greater variety of antibody combinations. Here, we demonstrate a simple, cost effective method of double indirect immunostaining of cultured cells using primary antibodies from the same species. This method uses microwaving of cell samples immediately after the application of the first secondary antibody, and significantly reduces the level of nonspecific staining. This technique does not elute the antibodies, nor raise the sample temperature above 37 degrees C. 相似文献
99.
William W. Yotis Nicholas Catsimpoolas Merlin S. Bergdoll Edward J. Schantz 《Infection and immunity》1974,9(5):974-976
Purified Staphylococcus aureus enterotoxins B and C(1), the causative agents of staphylococcal food poisoning, were resolved into several components by scanning isoelectric focusing in sucrose density gradients in the absence and presence of 6 M urea and 5 mM dithiothreitol. The observed heterogeneity persisted in the denaturing medium, which suggests that the primary structure of protein enterotoxins B and C(1) may be partly responsible for the isoelectric point differences of the various forms. To our knowledge, the scanning isoelectric focusing patterns of staphylococcal enterotoxins B and C(1) are reported for the first time. 相似文献
100.
Robert A. Kinsman Enrique Fernandez Marsha Schocket Jerald F. Dirks Nicholas A. Covino 《Journal of behavioral medicine》1983,6(4):339-357
Subjective symptoms and experiences were explored within a group of 146 severe, chronic bronchitis and emphysema patients. Eighty-nine symptoms and experiences, derived from initial interviews with 29 patients, were rated according to the frequency of occurrence during breathing difficulties. Key cluster analyses were used to derive a Bronchitis-Emphysema Symptom Checklist (BESC) measuring 11 symptom categories: Helplessness-Hopelessness, Decathexis, Fatigue, Poor Memory, Peripheral-Sensory Complaints, Dyspnea, Congestion, Sleep Difficulties, Irritability, Anxiety, and Alienation. The BESC symptom categories are highly reliable and the relationships among categories are stable across two subgroups of patients. The BESC provides one way to describe how patients cope with and experience chronic bronchitis and emphysema. 相似文献