全文获取类型
收费全文 | 10230篇 |
免费 | 999篇 |
国内免费 | 23篇 |
专业分类
耳鼻咽喉 | 125篇 |
儿科学 | 386篇 |
妇产科学 | 215篇 |
基础医学 | 1491篇 |
口腔科学 | 184篇 |
临床医学 | 1263篇 |
内科学 | 1988篇 |
皮肤病学 | 147篇 |
神经病学 | 841篇 |
特种医学 | 526篇 |
外国民族医学 | 1篇 |
外科学 | 1256篇 |
综合类 | 272篇 |
一般理论 | 3篇 |
预防医学 | 1024篇 |
眼科学 | 188篇 |
药学 | 726篇 |
中国医学 | 13篇 |
肿瘤学 | 603篇 |
出版年
2021年 | 118篇 |
2020年 | 88篇 |
2019年 | 127篇 |
2018年 | 168篇 |
2017年 | 105篇 |
2016年 | 105篇 |
2015年 | 171篇 |
2014年 | 243篇 |
2013年 | 322篇 |
2012年 | 476篇 |
2011年 | 443篇 |
2010年 | 271篇 |
2009年 | 283篇 |
2008年 | 428篇 |
2007年 | 458篇 |
2006年 | 448篇 |
2005年 | 449篇 |
2004年 | 417篇 |
2003年 | 363篇 |
2002年 | 384篇 |
2001年 | 359篇 |
2000年 | 351篇 |
1999年 | 277篇 |
1998年 | 191篇 |
1997年 | 159篇 |
1996年 | 165篇 |
1995年 | 159篇 |
1994年 | 140篇 |
1993年 | 134篇 |
1992年 | 260篇 |
1991年 | 190篇 |
1990年 | 225篇 |
1989年 | 243篇 |
1988年 | 204篇 |
1987年 | 201篇 |
1986年 | 161篇 |
1985年 | 158篇 |
1984年 | 141篇 |
1983年 | 139篇 |
1982年 | 89篇 |
1981年 | 104篇 |
1980年 | 88篇 |
1979年 | 124篇 |
1978年 | 114篇 |
1977年 | 82篇 |
1976年 | 75篇 |
1975年 | 86篇 |
1974年 | 85篇 |
1971年 | 72篇 |
1970年 | 70篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Robyn Stremler Ellen Hodnett Patricia Petryshen Bonnie Stevens Julie Weston Andrew R Willan 《分娩》2005,32(4):243-251
ABSTRACT: Background: Hands‐and‐knees positioning during labor has been recommended on the theory that gravity and buoyancy may promote fetal head rotation to the anterior position and reduce persistent back pain. A Cochrane review found insufficient evidence to support the effectiveness of this intervention during labor. The purpose of this study was to evaluate the effect of maternal hands‐and‐knees positioning on fetal head rotation from occipitoposterior to occipitoanterior position, persistent back pain, and other perinatal outcomes. Methods: Thirteen labor units in university‐affiliated hospitals participated in this multicenter randomized, controlled trial. Study participants were 147 women laboring with a fetus at ≥37 weeks’ gestation and confirmed by ultrasound to be in occipitoposterior position. Seventy women were randomized to the intervention group (hands‐and‐knees positioning for at least 30 minutes over a 1‐hour period during labor) and 77 to the control group (no hands‐and‐knees positioning). The primary outcome was occipitoanterior position determined by ultrasound following the 1‐hour study period and the secondary outcome was persistent back pain. Other outcomes included operative delivery, fetal head position at delivery, perineal trauma, Apgar scores, length of labor, and women's views with respect to positioning. Results: Women randomized to the intervention group had significant reductions in persistent back pain. Eleven women (16%) allocated to use hands‐and‐knees positioning had fetal heads in occipitoanterior position following the 1‐hour study period compared with 5 (7%) in the control group (relative risk 2.4; 95% CI 0.88–6.62; number needed to treat 11). Trends toward benefit for the intervention group were seen for several other outcomes, including operative delivery, fetal head position at delivery, 1‐minute Apgar scores, and time to delivery. Conclusions: Maternal hands‐and‐knees positioning during labor with a fetus in occipitoposterior position reduces persistent back pain and is acceptable to laboring women. Given this evidence, hands‐and‐knees positioning should be offered to women laboring with a fetus in occipitoposterior position in the first stage of labor to reduce persistent back pain. Although this study demonstrates trends toward improved birth outcomes, further trials are needed to determine if hands‐and‐knees positioning promotes fetal head rotation to occipitoanterior and reduces operative delivery. (BIRTH 32:4 December 2005) 相似文献
62.
Human immunodeficiency virus type 1 may preferentially integrate into chromatin occupied by L1Hs repetitive elements. 总被引:1,自引:1,他引:0 下载免费PDF全文
S W Stevens J D Griffith 《Proceedings of the National Academy of Sciences of the United States of America》1994,91(12):5557-5561
Human DNA flanking sites of eight human immunodeficiency virus type 1 (HIV-1) proviral integrations have been analyzed in isolates derived both from integrations in an infected individual and from tissue culture. Sequence analysis encompassing 80-3000 bp of human DNA on one or both sides of the site of integration revealed that seven of the eight HIV-1 proviruses had integrated directly into or within one nucleosome's distance from an L1Hs or Alu repetitive element. To compare this with the frequency at which human L1 or Alu elements sharing > or = 70% identity with L1Hs and Alu consensus sequences would be encountered at random, > 200 bp from each of 82 individual anonymously cloned segments of human DNA were sequenced: L1Hs elements were encountered in 8.5% of the 82 clones and Alu elements were encountered in 13.4+ by using these homology windows. From these data it appears that HIV-1 integrates into or near L1Hs elements with an approximately 6-fold higher frequency than would be expected if HIV-1 integration events were distributed uniformly throughout the genome. A cumulative binomial probability test shows that there is a 0.26% chance that one would arrive at these figures by chance and puts the data well within a 99% confidence interval. We propose that sites of L1Hs and Alu insertions originally occurred in regions of chromatin that were more easily accessible to the retroposon machinery and that these regions are now acting as preferred integration sites for HIV-1. 相似文献
63.
LIMITATIONS OF RADIOTHERAPY IN THE DEFINITIVE TREATMENT OF SQUAMOUS CARCINOMA OF THE TONSILLAR FOSSA
Christopher J. O'Brien Geeta K. Castle Graham N. Stevens G. Mac Halliday John K. Donovan Kenneth K. Lee Nicholas A. Packham Maurice J. Peat 《ANZ journal of surgery》1992,62(9):709-713
Between 1970 and 1990, 104 patients with squamous cell carcinoma (SCC) of the tonsil were treated. The median age was 58 years and 80% of patients were males. Distribution among clinical stages was: stage I, 19 patients; stage II, 12 patients; stage III, 23 patients; and stage IV, 48 patients. More than 70% of patients had initial radiotherapy as definitive treatment irrespective of stage, reflecting the treatment philosophy over much of this period. The overall survival rate was 26% at 5 years, with survival being significantly affected by T stage, clinical stage and age. Clinical node status did not significantly affect survival rates. Good local control of T1N0 cancers was achieved with radiotherapy alone, but patients with more advanced cancers did poorly. We have now moved away from a non-selective policy and use initial surgery combined with postoperative radiotherapy in most patients, reserving radiotherapy alone for mainly early tonsil cancers. 相似文献
64.
65.
Characterization of a benzyladenine binding-site peptide isolated from a wheat cytokinin-binding protein: sequence analysis and identification of a single affinity-labeled histidine residue by mass spectrometry 总被引:3,自引:1,他引:2 下载免费PDF全文
A C Brinegar G Cooper A Stevens C R Hauer J Shabanowitz D F Hunt J E Fox 《Proceedings of the National Academy of Sciences of the United States of America》1988,85(16):5927-5931
A wheat embryo cytokinin-binding protein was covalently modified with the radiolabeled photoaffinity ligand 2-azido-N6-[14C]benzyladenine. A single labeled peptide was obtained after proteolytic digestion and isolation by reversed-phase and anion-exchange HPLC. Sequencing by classical Edman degradation identified 11 of the 12 residues but failed to identify the labeled amino acid. Analysis by laser photodissociation Fourier-transform mass spectrometry of 10 pmol of the peptide independently confirmed the Edman data and also demonstrated that the histidine residue nearest the C terminus (underlined) was modified by the reagent in the sequence Ala-Phe-Leu-Gln-Pro-Ser-His-His-Asp-Ala-Asp-Glu. 相似文献
66.
67.
68.
CA Schroeter† L Kaas† JJ Waterval† PM Bos‡ HAM Neumann§ 《Journal of the European Academy of Dermatology and Venereology》2007,21(9):1170-1174
AIM: The aim of this pilot study was an investigation on photodynamic therapy (PDT) whether it is a good alternative for treating periungual and subungual warts of the hands. STUDY DESIGN: Twenty patients (mean age: 30.5 years) with a total of 40 periungual and subungual warts were treated with PDT. A photosensitizer, 20%delta-aminolevulinic acid was applied on the warts. After a mean incubation time of 4.6 h (SD: 1.2), the warts were irradiated with the VersaLight for 5-30 min (15.2 +/- 4.3 min). RESULTS: After a mean of 4.5 treatments a mean clearance of 100% was achieved in 90% of the patients. One patient (5%) showed a clearance of 50% and another showed no improvement. The subungual or periungual location of the wart had no influence on the number of treatments or end result (P > 0.05). There were two recurrences during the mean follow-up period of 5.9 months (SD: 7.6). Besides mainly pain and hyperpigmentation, most treatments had no side-effects. CONCLUSION: PDT can offer a good alternative for treating periungual warts of the hands. Larger studies are indicated. 相似文献
69.
N R Hill P C Hindmarsh R J Stevens I M Stratton J C Levy D R Matthews 《Diabetic medicine》2007,24(7):753-758
AIM: As the practice of multiple assessments of glucose concentration throughout the day increases for people with diabetes, there is a need for an assessment of glycaemic control weighted for the clinical risks of both hypoglycaemia and hyperglycaemia. METHODS: We have developed a methodology to report the degree of risk which a glycaemic profile represents. Fifty diabetes professionals assigned risk values to a range of 40 blood glucose concentrations. Their responses were summarised and a generic function of glycaemic risk was derived. This function was applied to patient glucose profiles to generate an integrated risk score termed the Glycaemic Risk Assessment Diabetes Equation (GRADE). The GRADE score was then reported by use of the mean value and the relative percent contribution to the weighted risk score from the hypoglycaemic, euglycaemic, hyperglycaemic range, respectively, e.g. GRADE (hypoglycaemia%, euglycaemia%, hyperglycaemia%). RESULTS: The GRADE scores of indicative glucose profiles were as follows: continuous glucose monitoring profile non-diabetic subjects GRADE = 1.1, Type 1 diabetes continuous glucose monitoring GRADE = 8.09 (20%, 8%, 72%), Type 2 diabetes home blood glucose monitoring GRADE = 9.97 (2%, 7%, 91%). CONCLUSIONS: The GRADE score of a glucose profile summarises the degree of risk associated with a glucose profile. Values < 5 correspond to euglycaemia. The GRADE score is simple to generate from any blood glucose profile and can be used as an adjunct to HbA1c to report the degree of risk associated with glycaemic variability. 相似文献
70.
Holly L Rosenzweig Manabu Minami Nikola S Lessov Sarah C Coste Susan L Stevens David C Henshall Robert Meller Roger P Simon Mary P Stenzel-Poore 《Journal of cerebral blood flow and metabolism》2007,27(10):1663-1674
Lipopolysaccharide (LPS) preconditioning provides neuroprotection against subsequent cerebral ischemic injury. Tumor necrosis factor-alpha (TNFalpha) is protective in LPS-induced preconditioning yet exacerbates neuronal injury in ischemia. Here, we define dual roles of TNFalpha in LPS-induced ischemic tolerance in a murine model of stroke and in primary neuronal cultures in vitro, and show that the cytotoxic effects of TNFalpha are attenuated by LPS preconditioning. We show that LPS preconditioning significantly increases circulating levels of TNFalpha before middle cerebral artery occlusion in mice and show that TNFalpha is required to establish subsequent neuroprotection against ischemia, as mice lacking TNFalpha are not protected from ischemic injury by LPS preconditioning. After stroke, LPS preconditioned mice have a significant reduction in the levels of TNFalpha (approximately threefold) and the proximal TNFalpha signaling molecules, neuronal TNF-receptor 1 (TNFR1), and TNFR-associated death domain (TRADD). Soluble TNFR1 (s-TNFR1) levels were significantly increased after stroke in LPS-preconditioned mice (approximately 2.5-fold), which may neutralize the effect of TNFalpha and reduce TNFalpha-mediated injury in ischemia. Importantly, LPS-preconditioned mice show marked resistance to brain injury caused by intracerebral administration of exogenous TNFalpha after stroke. We establish an in vitro model of LPS preconditioning in primary cortical neuronal cultures and show that LPS preconditioning causes significant protection against injurious TNFalpha in the setting of ischemia. Our studies suggest that TNFalpha is a twin-edged sword in the setting of stroke: TNFalpha upregulation is needed to establish LPS-induced tolerance before ischemia, whereas suppression of TNFalpha signaling during ischemia confers neuroprotection after LPS preconditioning. 相似文献