全文获取类型
收费全文 | 15331篇 |
免费 | 1426篇 |
国内免费 | 7篇 |
专业分类
16764篇 |
出版年
2023年 | 41篇 |
2022年 | 90篇 |
2021年 | 171篇 |
2020年 | 125篇 |
2019年 | 133篇 |
2018年 | 172篇 |
2017年 | 179篇 |
2016年 | 350篇 |
2015年 | 570篇 |
2014年 | 645篇 |
2013年 | 763篇 |
2012年 | 1095篇 |
2011年 | 1168篇 |
2010年 | 768篇 |
2009年 | 694篇 |
2008年 | 924篇 |
2007年 | 1024篇 |
2006年 | 868篇 |
2005年 | 878篇 |
2004年 | 921篇 |
2003年 | 859篇 |
2002年 | 825篇 |
2001年 | 168篇 |
2000年 | 121篇 |
1999年 | 219篇 |
1998年 | 255篇 |
1997年 | 166篇 |
1996年 | 167篇 |
1995年 | 156篇 |
1994年 | 159篇 |
1993年 | 152篇 |
1992年 | 139篇 |
1991年 | 100篇 |
1990年 | 116篇 |
1989年 | 99篇 |
1988年 | 110篇 |
1987年 | 92篇 |
1986年 | 92篇 |
1985年 | 93篇 |
1984年 | 126篇 |
1983年 | 92篇 |
1982年 | 119篇 |
1981年 | 116篇 |
1980年 | 98篇 |
1979年 | 56篇 |
1978年 | 66篇 |
1977年 | 64篇 |
1976年 | 64篇 |
1975年 | 46篇 |
1974年 | 56篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Simon W.J. Gould Maureen Chadwick Paul Cuschieri Susan Easmon Anthony C. Richardson Robert G. Price & Mark D. Fielder 《FEMS microbiology letters》2009,297(1):10-16
Pinellia ternata , a traditional Chinese herb that has been used in China for over 1000 years, is susceptible to a soft rot disease, which may cause major loss of yield. The use of bacteria as potential antagonists against Pectobacterium carotovorum SXR1, the causal agent of the disease on P. ternata , was evaluated. Altogether, 1107 candidate bacteria were isolated from the rhizosphere and surface-sterilized plants of P. ternata . In Petri dish tests, 55 isolates inhibited the growth of strain SXR1, and 21 of these reduced the disease development on P. ternata slices by over 50%. Four selected antagonists significantly reduced the disease incidence on tissue culture seedlings, and also prevented the disease on the transplants. Agonist P-Y2-2 yielded a good prevention level of 81.9%. The four antagonists rapidly colonized the tissue culture seedlings and transplants, whereas greater populations of the antagonists (107 –109 CFU g−1 fresh tissues) were observed in the seedlings and in the preinoculated transplants than in those inoculated during transplanting. The use of pathogen-free tissue culture seedlings pre-inoculated with antagonist may provide a strategy for production of P. ternata plantlets resistant to soft rot disease. This is the first report on the efficacy of biocontrol agents against pathogens on P. ternata . 相似文献
993.
994.
995.
996.
Mario A. Pardo Tim Gerrodette Emilio Beier Diane Gendron Karin A. Forney Susan J. Chivers Jay Barlow Daniel M. Palacios 《PloS one》2015,10(3)
We inferred the population densities of blue whales (Balaenoptera musculus) and short-beaked common dolphins (Delphinus delphis) in the Northeast Pacific Ocean as functions of the water-column’s physical structure by implementing hierarchical models in a Bayesian framework. This approach allowed us to propagate the uncertainty of the field observations into the inference of species-habitat relationships and to generate spatially explicit population density predictions with reduced effects of sampling heterogeneity. Our hypothesis was that the large-scale spatial distributions of these two cetacean species respond primarily to ecological processes resulting from shoaling and outcropping of the pycnocline in regions of wind-forced upwelling and eddy-like circulation. Physically, these processes affect the thermodynamic balance of the water column, decreasing its volume and thus the height of the absolute dynamic topography (ADT). Biologically, they lead to elevated primary productivity and persistent aggregation of low-trophic-level prey. Unlike other remotely sensed variables, ADT provides information about the structure of the entire water column and it is also routinely measured at high spatial-temporal resolution by satellite altimeters with uniform global coverage. Our models provide spatially explicit population density predictions for both species, even in areas where the pycnocline shoals but does not outcrop (e.g. the Costa Rica Dome and the North Equatorial Countercurrent thermocline ridge). Interannual variations in distribution during El Niño anomalies suggest that the population density of both species decreases dramatically in the Equatorial Cold Tongue and the Costa Rica Dome, and that their distributions retract to particular areas that remain productive, such as the more oceanic waters in the central California Current System, the northern Gulf of California, the North Equatorial Countercurrent thermocline ridge, and the more southern portion of the Humboldt Current System. We posit that such reductions in available foraging habitats during climatic disturbances could incur high energetic costs on these populations, ultimately affecting individual fitness and survival. 相似文献
997.
Jonathan C. Hill Elaine Thomas Susan Hill Nadine E. Foster Danielle A. van der Windt 《PloS one》2015,10(4)
Objective
To develop and validate a patient report outcome measure (PROM) for clinical practice that can monitor health status of patients with a range of musculoskeletal (MSK) disorders.Methods
Constructs for inclusion in the MSK-PROM were identified from a consensus process involving patients with musculoskeletal conditions, clinicians, purchasers of healthcare services, and primary care researchers. Psychometric properties of the brief tool, including face and construct validity, repeatability and responsiveness were assessed in a sample of patients with musculoskeletal pain consulting physiotherapy services in the United Kingdom (n=425).Results
The consensus process identified 10 prioritised domains for monitoring musculoskeletal health status: pain intensity, quality of life, physical capacity, interference with social/leisure activities, emotional well-being, severity of most difficult thing, activities and roles, understanding independence, and overall impact. As the EuroQol (EQ-5D-5L) is a widely adopted PROMs tool and covers the first four domains listed, to reduce patient burden to a minimum the MSK-PROM was designed to capture the remaining six prioritised domains which are not measured by the EQ-5D-5L. The tool demonstrated excellent reliability, construct validity, responsiveness and acceptability to patients and clinicians for use in clinical practice.Conclusion
We have validated a brief patient reported outcome measure (MSK-PROM) for use in clinical practice to measure musculoskeletal health status and monitor outcomes over time using domains that are meaningful to patients and sensitive to change. Further work will establish whether the MSK-PROM is useful in other musculoskeletal healthcare settings. 相似文献998.
Kate Buchacz Miao-Jung Chen Maree Kay Parisi Maya Yoshida-Cervantes Erin Antunez Viva Delgado Nicholas J. Moss Susan Scheer 《PloS one》2015,10(3)
Background
Persons with unsuppressed HIV viral load (VL) who disengage from care may experience poor clinical outcomes and potentially transmit HIV. We assessed the feasibility and yield of using the San Francisco Department of Public Health (SFDPH) enhanced HIV surveillance system (eHARS) to identify and re-engage such persons in care.Methods
Using SFDPH eHARS data as of 4/20/2012 (index date), we selected HIV-infected adults who were alive, had no reported VL or CD4 cell count results in the past nine months (proxy for “out-of-care”) and a VL >200 copies/mL drawn nine to 15 months earlier. We prioritized cases residing locally for investigation, and used information from eHARS and medical and public health databases to contact them for interview and referral to the SFDPH linkage services (LINCS). Twelve months later, we matched-back to eHARS data to assess how HIV laboratory reporting delays affected original eligibility, and if persons had any HIV laboratory results performed and reported within 12 months after index date (‘new labs’).Results
Among 434 eligible persons, 282 were prioritized for investigation, of whom 75 (27%) were interviewed, 79 (28%) could not be located, and 48 (17%) were located out of the area. Among the interviewed, 54 (72%) persons accepted referral to LINCS. Upon match-back to eHARS data, 324 (75%) in total were confirmed as eligible, including 221 (78%) of the investigated; most had new labs.Conclusions
Among the investigated persons presumed out-of-care, we interviewed and offered LINCS referral to about one-quarter, demonstrating the feasibility but limited yield of our project. Matching to updated surveillance data revealed that a substantial minority did not disengage from care and that most re-engaged in HIV care. Verifying persons’ HIV care status with medical providers and improving timeliness of transfer and cross-jurisdictional sharing of HIV laboratory data may aid future efforts. 相似文献999.
Elizabeth F. Closson Matthew J. Mimiaga Susan G. Sherman Arunrat Tangmunkongvorakul Ruth K. Friedman Mohammed Limbada Ayana T. Moore Kriengkrai Srithanaviboonchai Carla A. Alves Sarah Roberts Catherine E. Oldenburg Vanessa Elharrar Kenneth H. Mayer Steven A. Safren for the HPTN study team 《PloS one》2015,10(3)
1000.
Stephanie Boehme Viktoria Ritter Susan Tefikow Ulrich Stangier Bernhard Strauss Wolfgang H. R. Miltner Thomas Straube 《PloS one》2015,10(6)
Disorder-relevant but task-unrelated stimuli impair cognitive performance in social anxiety disorder (SAD); however, time course and neural correlates of emotional interference are unknown. The present study investigated time course and neural basis of emotional interference in SAD using event-related functional magnetic resonance imaging (fMRI). Patients with SAD and healthy controls performed an emotional stroop task which allowed examining interference effects on the current and the succeeding trial. Reaction time data showed an emotional interference effect in the current trial, but not the succeeding trial, specifically in SAD. FMRI data showed greater activation in the left amygdala, bilateral insula, medial prefrontal cortex (mPFC), dorsal anterior cingulate cortex (ACC), and left opercular part of the inferior frontal gyrus during emotional interference of the current trial in SAD patients. Furthermore, we found a positive correlation between patients’ interference scores and activation in the mPFC, dorsal ACC and left angular/supramarginal gyrus. Taken together, results indicate a network of brain regions comprising amygdala, insula, mPFC, ACC, and areas strongly involved in language processing during the processing of task-unrelated threat in SAD. However, specifically the activation in mPFC, dorsal ACC, and left angular/supramarginal gyrus is associated with the strength of the interference effect, suggesting a cognitive network model of attentional bias in SAD. This probably comprises exceeded allocation of attentional resources to disorder-related information of the presented stimuli and increased self-referential and semantic processing of threat words in SAD. 相似文献