全文获取类型
收费全文 | 7516篇 |
免费 | 594篇 |
国内免费 | 30篇 |
专业分类
耳鼻咽喉 | 91篇 |
儿科学 | 312篇 |
妇产科学 | 152篇 |
基础医学 | 923篇 |
口腔科学 | 238篇 |
临床医学 | 843篇 |
内科学 | 1607篇 |
皮肤病学 | 109篇 |
神经病学 | 624篇 |
特种医学 | 661篇 |
外国民族医学 | 4篇 |
外科学 | 668篇 |
综合类 | 92篇 |
预防医学 | 625篇 |
眼科学 | 224篇 |
药学 | 634篇 |
1篇 | |
中国医学 | 6篇 |
肿瘤学 | 326篇 |
出版年
2021年 | 69篇 |
2019年 | 73篇 |
2018年 | 92篇 |
2017年 | 69篇 |
2016年 | 94篇 |
2015年 | 108篇 |
2014年 | 154篇 |
2013年 | 220篇 |
2012年 | 293篇 |
2011年 | 323篇 |
2010年 | 197篇 |
2009年 | 232篇 |
2008年 | 279篇 |
2007年 | 319篇 |
2006年 | 278篇 |
2005年 | 296篇 |
2004年 | 244篇 |
2003年 | 268篇 |
2002年 | 225篇 |
2001年 | 246篇 |
2000年 | 221篇 |
1999年 | 204篇 |
1998年 | 168篇 |
1997年 | 161篇 |
1996年 | 165篇 |
1995年 | 119篇 |
1994年 | 148篇 |
1993年 | 148篇 |
1992年 | 150篇 |
1991年 | 165篇 |
1990年 | 172篇 |
1989年 | 206篇 |
1988年 | 173篇 |
1987年 | 136篇 |
1986年 | 146篇 |
1985年 | 135篇 |
1984年 | 114篇 |
1983年 | 73篇 |
1982年 | 58篇 |
1981年 | 73篇 |
1980年 | 61篇 |
1979年 | 83篇 |
1978年 | 79篇 |
1977年 | 76篇 |
1976年 | 64篇 |
1975年 | 51篇 |
1974年 | 55篇 |
1973年 | 62篇 |
1972年 | 68篇 |
1971年 | 52篇 |
排序方式: 共有8140条查询结果,搜索用时 1 毫秒
61.
Until recently, resistive training for prepubescents has met largely with skepticism. Original, and possibly premature, conclusions with respect to the efficacy of weight training on prepubescents, considered insufficient circulating androgens in children as the predominant restriction to strength gains. Additionally, safety concerns regarding bone integrity, epiphyseal continuity and risk of injury have been common. A review of the most recent investigations overwhelmingly supports significant strength gains in prepubescents as a result of weight training. Further, based on recent findings of short-term prepubertal weight training, no damage to bone, epiphyses, growth tissue, or muscle has been reported. In light of these findings, weight training may be recommended provided expert professionals are consulted and strict supervision is maintained. It is also recommended that repetitions be maintained within the 6-10 range rather than utilizing maximum weight. J Orthop Sports Phys Ther 1989;11(3):96-99. 相似文献
62.
With regard to cadmium toxicity, Drosophila strains v;bw and Austin represent extremes in resistance and sensitivity, respectively. Both strains produced metallothionein (MT) in response to Cd ions in their diet. Austin produced more metallothionein than v;bw at Cd ion levels below 0.2 mM, when both strains were allowed lifetime development on Cd2+-containing media. When the rate of MT appearance was measured for 4 days in young adults the results showed no clear trend with time within a strain or between strains. The plot of LC50 vs. MT levels for identical developmental conditions revealed that for v;bw small increases in MT corresponded to large increases in resistance whereas for the sensitive Austin even large increases in MT had comparatively little effect on increasing LC50. Results given here suggest that differences in total MT content do not explain the genetically demonstrable difference in Cd2+-resistance between v;bw and Austin. However, since two MT genes are identified in Drosophila, differences in resistance could be reflective of greater relative amounts of one "more important" MT in the resistant fly. 相似文献
63.
64.
65.
Invasive fungal sinusitis and meningitis due to Arthrographis kalrae in a patient with AIDS 总被引:2,自引:0,他引:2
Chin-Hong PV Sutton DA Roemer M Jacobson MA Aberg JA 《Journal of clinical microbiology》2001,39(2):804-807
We report the first described case of Arthrographis kalrae pansinusitis and meningitis in a patient with AIDS. The patient was initially diagnosed with Arthrographis kalrae pansinusitis by endoscopic biopsy and culture. The patient was treated with itraconazole for approximately 5 months and then died secondary to Pneumocytis carinii pneumonia. Postmortem examination revealed invasive fungal sinusitis that involved the sphenoid sinus and that extended through the cribiform plate into the inferior surfaces of the bilateral frontal lobes. There was also an associated fungal meningitis and vasculitis with fungal thrombosis and multiple recent infarcts that involved the frontal lobes, right caudate nucleus, and putamen. Post mortem cultures were positive for A. kalrae. 相似文献
66.
Relative carriage rates of nuclear dehydrogenating clostridia in two populations of different colorectal cancer risk
下载免费PDF全文
![点击此处可从《Journal of clinical pathology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Carriage of nuclear dehydrogenating clostridia has been associated with colon cancer and implicated in its aetiology. This study has compared the carriage of these organisms in a British population at high risk for the development of colon cancer with a low risk Nigerian population. Clostridia were found in all of the stools from both populations. Nuclear dehydrogenating clostridia were only found in the stools of the British subjects (32%). These results support the suggestion that the carriage rate of nuclear dehydrogenating clostridia in a population is related to the risk of colon cancer. 相似文献
67.
Effect of an amber mutation in the herpes simplex virus thymidine kinase gene on polypeptide synthesis and stability 总被引:14,自引:0,他引:14
KG111 is a mutant of herpes simplex virus (HSV), strain KOS, that exhibits temperature-dependent drug resistance. For example, it is almost as resistant as a thymidine kinase (tk)-deficient virus at 39 degrees, but is relatively sensitive to acyclovir at 34 degrees, Using marker transfer techniques, we have mapped the mutation conferring temperature-dependent drug resistance in KG111 to the 5' portion of the tk gene. Sequencing of this region revealed an amber mutation at codon 44, which lies between the first and second methionine codons of the tk polypeptide. This mutation is identical to that found in TK4, an HSV mutant derived from Cl 101 (L. Haarr et al., 1985, J. Virol. 56, 512-519). Analyses of immunoprecipitated tk proteins from KG111- and TK4-infected cells showed that KG111 and TK4 do not synthesize full-length tk polypeptides, but instead produce a truncated form of the protein. Small amounts of a similar truncated tk polypeptide are also produced in wild-type-infected cells and are thought to arise from initiation at a downstream AUG. The relative amounts and size of the mutant tk proteins compared with those of the wild-type are consistent with the amber mutation eliminating translation of full-length polypeptide and causing a four- to fivefold increase in the utilization of downstream AUG codons for initiation. The truncated polypeptides specified by KG111 and TK4 are less stable than the full-length polypeptide at 39 degrees, which may contribute to the conditional drug-resistant phenotype. On the other hand, the truncated polypeptides normally expressed by wild-type virus at low levels and the more highly expressed truncated tk polypeptides from a deletion mutant are relatively stable at 39 degrees. These results suggest that stability of the truncated tk polypeptide is influenced by the amount of tk present. 相似文献
68.
Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability 总被引:1,自引:15,他引:1
La Spada AR; Peterson KR; Meadows SA; McClain ME; Jeng G; Chmelar RS; Haugen HA; Chen K; Singer MJ; Moore D; Trask BJ; Fischbeck KH; Clegg CH; McKnight GS 《Human molecular genetics》1998,7(6):959-967
X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG
repeat expansion in the first exon of the androgen receptor (AR) gene.
Disease-associated alleles (37-66 CAGs) change in length when transmitted
from parents to offspring, with a significantly greater tendency to shift
size when inherited paternally. As transgenic mice carrying human AR cDNAs
with 45 and 66 CAG repeats do not display repeat instability, we attempted
to model trinucleotide repeat instability by generating transgenic mice
with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions
in their genomic context. Studies of independent lines of AR YAC transgenic
mice with CAG 45 alleles reveal intergenerational instability at an overall
rate of approximately 10%. We also find that the 45 CAG repeat tracts are
significantly more unstable with maternal transmission and as the
transmitting mother ages. Of all the CAG/CTG repeat transgenic mice
produced to date the AR YAC CAG 45 mice are unstable with the smallest
trinucleotide repeat mutations, suggesting that the length threshold for
repeat instability in the mouse may be lowered by including the appropriate
flanking human DNA sequences. By sequence-tagged site content analysis and
long range mapping we determined that one unstable transgenic line has
integrated an approximately 70 kb segment of the AR locus due to
fragmentation of the AR YAC. Identification of the cis - acting elements
that permit CAG tract instability and the trans -acting factors that
modulate repeat instability in the AR YAC CAG 45 mice may provide insights
into the molecular basis of trinucleotide repeat instability in humans.
相似文献
69.
Weiss RD Kolodziej M Griffin ML Najavits LM Jacobson LM Greenfield SF 《Journal of affective disorders》2004,79(1-3):279-283
BACKGROUND: Bipolar disorder (BPD) is the Axis I disorder with the highest risk for coexisting substance use disorder. One explanation for this phenomenon is the 'self-medication hypothesis', which states that some patients experience improvement in psychiatric symptoms as a result of substance use. We thus investigated reasons for substance use and perceived substance-induced improvement in BPD symptoms among patients with current BPD and substance dependence. METHODS: A total of 45 patients received six monthly assessments; 21 also received integrated group therapy (IGT), focusing simultaneously on BPD and substance dependence, while 24 did not receive IGT. Patients reported at intake their current reasons for initiating substance use (including BPD symptoms) and the effects of substance use on those symptoms. RESULTS: Nearly all patients initiated substance use because of at least one BPD symptom, especially depression (77.8%) and racing thoughts (57.8%); most (66.7%) reported improvement in at least one BPD symptom as a result of substance use. Among patients reporting substance-induced improvement in BPD symptoms, those receiving IGT reported fewer days of drug use over the 6-month study period than those not receiving IGT; this difference was not significant among patients without substance-induced improvement in BPD symptoms. LIMITATIONS: The study is limited by its small sample size and by the potential inaccuracy of self-reports regarding the effects of substance use on mood. CONCLUSIONS: Substance dependent patients who report that substance use improves their BPD symptoms may benefit from treatment that focuses simultaneously on both disorders. 相似文献
70.