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   514篇
  免费   24篇
  国内免费   12篇
  550篇
  2024年   3篇
  2023年   16篇
  2022年   27篇
  2021年   22篇
  2020年   15篇
  2019年   22篇
  2018年   18篇
  2017年   16篇
  2016年   17篇
  2015年   11篇
  2014年   44篇
  2013年   86篇
  2012年   41篇
  2011年   28篇
  2010年   10篇
  2009年   19篇
  2008年   22篇
  2007年   13篇
  2006年   9篇
  2005年   9篇
  2004年   7篇
  2003年   10篇
  2002年   3篇
  2001年   8篇
  2000年   4篇
  1999年   4篇
  1998年   3篇
  1997年   1篇
  1996年   1篇
  1994年   3篇
  1993年   3篇
  1992年   3篇
  1990年   3篇
  1989年   1篇
  1988年   1篇
  1987年   3篇
  1986年   1篇
  1985年   2篇
  1984年   7篇
  1983年   5篇
  1982年   2篇
  1981年   5篇
  1980年   1篇
  1979年   3篇
  1978年   5篇
  1977年   5篇
  1976年   3篇
  1975年   1篇
  1974年   2篇
  1973年   2篇
排序方式: 共有550条查询结果,搜索用时 0 毫秒
461.
Types and the corresponding rules in the International Code of Zoological Nomenclature are crucial for taxonomy and are meant to provide nomenclatural stability. In the case of neotypification, especially diligent taxonomic work is required to retain continuity. In the present communication, we first outline the main principles of typification and neotypification. We then discuss a critical case, using a current example from the marine planktonic tintinnid genus Tintinnopsis Stein, 1867 (Alveolata, Ciliophora). This diverse and ubiquitous genus is nonmonophyletic, but its revision and the erection of new related genera is currently prevented by the uncertain affiliation of its type species.  相似文献   
462.
Clarification of the criteria for managing animal health is essential to increase the reliability of experiments and ensure transparency in animal welfare. For experiments performed in space, there is no consensus on how to care for animals owing to technical issues, launch mass limitation, and human resources. Some biological processes in mammals, such as musculoskeletal or immune processes, are altered in the space environment, and mice in space can be used to simulate morbid states, such as senescence acceleration. Thus, there is a need to establish a novel evaluation method and evaluation criteria to monitor animal health. Here, we report a novel method to evaluate the health of mice in space through a video downlink in a series of space experiments using the Multiple Artificial-gravity Research System (MARS). This method was found to be more useful in evaluating animal health in space than observations and body weight changes of the same live mice following their return to Earth. We also developed criteria to evaluate health status via a video downlink. These criteria, with “Fur condition” and “Respiratory” as key items, provided information on the daily changes in the health status of mice and helped to identify malfunctions at an early stage. Our method and criteria led to the success of our missions, and they will help establish appropriate rules for space experiments in the future.  相似文献   
463.
ObjectiveTo determine the prevalence of obesity and assess the cardiometabolic risk profile and treatments associated with obesity management in the type 1 diabetes mellitus adult population.MethodsWe reviewed the records of all patients with type 1 diabetes mellitus seen in our institution’s outpatient endocrinology clinic between 2015 and 2018. We stratified the patients into 4 weight categories on the basis of body mass index (BMI) (normal, overweight, obesity class I, and combined obesity class II and III) and evaluated their associated clinical characteristics and relevant medications.ResultsOf 451 patients, 64% had a BMI of >25 kg/m2, and 25% had a BMI of ≥30 kg/m2. Over 40% of patients with a BMI of >30 kg/m2 had a history of cardiovascular disease. The off-label use of the glucagon-like peptide 1 receptor agonist was 12% and the sodium glucose cotransporter 2 inhibitor use was 5% in those with obesity. Only 2 patients were prescribed phentermine and 3 had undergone bariatric surgery. Hemoglobin A1C and low-density lipoprotein did not significantly differ between the normal weight and obesity groups. The obesity groups had significantly higher levels of median triglycerides and lower high-density lipoprotein than the normal weight group.ConclusionObesity was prevalent in a population of patients with type 1 diabetes mellitus seen in a specialty clinic. Those with obesity had a higher prevalence of cardiovascular disease than their normal weight counterparts. The use of weight loss medications was scarce. Studies exploring the safety and efficacy of obesity-targeted therapy in the type 1 diabetes mellitus population are needed.  相似文献   
464.
AimWe sought to evaluate the effect of radiation therapy on post-prostatectomy urinary quality of life in prostate cancer patients.BackgroundIn some men with non-metastatic prostate cancer, radiation therapy is indicated following prostatectomy. The radiation toxicity and quality of life considerations are unique in the post-prostatectomy setting.Materials and methodsA total of 106 patients receiving post-prostatectomy radiation therapy completed the Expanded Prostate Cancer Index Composite questionnaire before radiation and at 2-year follow-up. The primary outcomes of this study were the urinary domain summary score and subscale scores. Planned analysis was performed based on time interval from prostatectomy to radiation therapy.ResultsAmong the 106 patients analyzed, the mean urinary domain summary score worsened at 2-year follow-up after radiation therapy, lowering from 77.23–72.51 (p = 0.0085). Similar worsening was observed in the subscales of function (p = 0.003), bother (p = 0.0397), and incontinence (p = 0.0003). Urinary incontinence showed the greatest observable change among subscales. While the summary score worsened (p = 0.0031) among patients receiving radiation therapy more than 1 year after prostatectomy, it did not show statistically significant change in those treated 1 year or less after prostatectomy.ConclusionOur results demonstrate that post-prostatectomy radiation therapy is associated with modest declines in reportable urinary quality of life. Patients receiving radiation therapy more than 1 year after prostatectomy showed greater worsening of urinary quality of life, which indicates that there may be no functional advantage to delaying radiation therapy beyond the initial postoperative period.  相似文献   
465.
进入生物经济时代以来,以生物医药产业为代表的生物技术产业正在引领人类新一波技术产业革命。我国针对生物医药产业作出的战略部署已经取得了明显成效,但与美国等生物医药强国相比仍有较大的竞争差距。采用波特钻石模型构建了生物医药产业国际竞争力理论分析框架,以美国为例分析其生物医药产业在要素状况、企业结构和竞争、需求条件、相关及支持性产业、政府和发展机会六个方面的竞争优势,并基于此提出了我国发展生物医药产业的政策建议,从而为我国生物医药产业发展提供政策参考。  相似文献   
466.
《Endocrine practice》2021,27(7):743-748
ObjectivesTo examine main factors that influence the decision to choose pediatric endocrinology as a career among pediatric endocrinologists and assess their work satisfaction or stress level and suggested strategies to increase interest in subspecialty training in pediatric endocrinology.MethodsA workforce survey was distributed among 1470 members of the Pediatric Endocrine Society.ResultsThe response rate was 37.4%, with 550 members responding. The most common reasons for the respondents choosing pediatric endocrinology were intellectual stimulation (79%), exposure to endocrinology during residency (57%) or medical school (43%), and ability to establish relationships with patients with chronic disorders (54%). Of the respondents, 97% considered intellectual stimulation as the most favorable aspect of the specialty, and 84% considered financial compensation as the most unfavorable aspect of pediatric endocrinology. Majority (77%) were satisfied or very satisfied with their work environment. The mean work-related stress score (0 [none] to 10 [worst]) was 5.7, standard deviation was 2.1, and median was 6 (Q1, Q3: 4, 7). Increased financial compensation for the services and loan payment or forgiveness option were the top strategies suggested to enhance interest among residents for training in the subspecialty. One third (37%) felt that reducing the duration of the fellowship to 2 years would increase interest in training in pediatric endocrinology.ConclusionThe pediatric endocrinologists reported overall excellent career satisfaction, indicating the potential to attract high-quality doctors to the specialty. Improving reimbursement and loan forgiveness were the top strategies suggested for increasing interest in subspecialty training in pediatric endocrinology.  相似文献   
467.
Summary The overall efficiency of insecticides with various egg, nymph and adult efficacy for brown planthopper control were analyzed using a simulation approach. Insecticides which have high nymphal efficacy are most effective. Nymphal efficacy contributes up to 71% of the potential efficiency while ovicidal efficacy contributes the remaining 29%. Adult efficacy alone appears to have negligible effects. Long residual efficacy provides better control, however, the increase in efficiency is not directly proportional to the residual period of the insecticide. A residual period of 10 to 15 days would suffice for BPH control.  相似文献   
468.
Marine sponges represent a rich source of uncharacterized microbial diversity, and many are host to microorganisms that produce biologically active specialized metabolites. Here, a polyphasic approach was used to characterize two Actinobacteria strains, P01-B04T and P01-F02, that were isolated from the marine sponges Geodia barretti (Bowerbank, 1858) and Antho dichotoma (Esper, 1794), respectively. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strains P01-B04T and P01-F02 are closely related to Streptomyces beijiangensis DSM 41794T, Streptomyces laculatispora NRRL B-24909T, and Streptomyces brevispora NRRL B-24910T. The two strains showed nearly identical 16S rRNA gene sequences (99.93%), and the average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) relatedness values were 99.96% and 99.6%, respectively, suggesting that these strains are affiliated with the same species. Chemotaxonomic and culture characteristics of both strains were also consistent with the genus Streptomyces, while phenotypic properties, genome-based comparisons, and phylogenomic analyses distinguished strains P01-B04T and P01-F02 from their closest phylogenetic relatives. In silico analysis predicted that the 8.9 Mb genome of P01-B04T contains at least 41 biosynthetic gene clusters (BGCs) encoding secondary metabolites, indicating that this strain could express diverse bioactive metabolites; in support of this prediction, this strain expressed antibacterial activity against Gram-positive bacteria including a clinical isolate of methicillin-resistant Staphylococcus aureus (MRSA) EAMC30. Based on these results, the marine sponge-associated isolates represent a novel species of the genus Streptomyces, for which the name Streptomyces poriferorum sp. nov. is proposed, with P01-B04T (=DSM 111306T = CCM 9048T) as the type strain.  相似文献   
469.
Replicate anthropometric measurements on 20 male and 22 female Eskimos were examined using analysis of variance, product-moment correlation coefficients, and canonical variates with Mahalanobis' D2 distances. Analysis of variance indicated that 12 of the 16 variables could be measured comparably by two investigators. Those variables with readily defined endpoints yielded the highest correlations between the results of two anthropometrists. The multivariate analysis demonstrated a high level of discrimination between two sets of data taken on the same group of subjects. This suggests that population comparisons using data from two or more investigators could be significantly affected by measurement error.  相似文献   
470.
BackgroundExternal beam radiation therapy (EBRT) is rarely used to treat patients with differentiated or medullary thyroid cancer. Although EBRT is generally administered to patients with high-risk or unresectable diseases, neither its indications for the use nor the associated outcomes are well-defined. We used a statewide cohort to assess the trends in EBRT use and postradiation outcomes in California.MethodsA population-based study of patients within the California Cancer Registry who underwent EBRT after surgery for nonanaplastic thyroid cancer (2003-2017) was conducted. The primary outcome was the annual utilization rate of EBRT. The secondary outcomes included Kaplan-Meier analysis for cause-specific survival and identifying factors associated with improved survival after EBRT.ResultsAmong the 57 607 patients with nonanaplastic thyroid cancer from 2003 to 2017, 344 (0.6%) patients received EBRT. EBRT was utilized in 0.4% of papillary, 1.1% of follicular, and 7.7% of medullary thyroid cancers in California. Overall, 99 (28.8%) patients treated with EBRT died of thyroid cancer. The 10-year cause-specific survival of all patients with thyroid cancer after EBRT was 61.5% (95% CI: 54.8%-69.1%) and that of patients without distant disease was 80.3% (95% CI: 73.5%-87.8%). The survival outcomes varied by tumor size, histology, disease stage, patient age at diagnosis, and the presence of extrathyroidal extension (P < .05).ConclusionsThe use of adjuvant EBRT for nonanaplastic thyroid cancer remained stable and low in California from 2003 to 2017. The comparative efficacy of EBRT was not discernible in this study, but disease control appeared durable in select patients. Well-controlled observational studies and/or prospective studies are needed to better define which patients benefit from EBRT.  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