全文获取类型
收费全文 | 45343篇 |
免费 | 3370篇 |
国内免费 | 135篇 |
专业分类
耳鼻咽喉 | 592篇 |
儿科学 | 1139篇 |
妇产科学 | 552篇 |
基础医学 | 5665篇 |
口腔科学 | 475篇 |
临床医学 | 4758篇 |
内科学 | 9144篇 |
皮肤病学 | 481篇 |
神经病学 | 4470篇 |
特种医学 | 1777篇 |
外科学 | 8728篇 |
综合类 | 349篇 |
现状与发展 | 1篇 |
一般理论 | 56篇 |
预防医学 | 3757篇 |
眼科学 | 801篇 |
药学 | 2845篇 |
中国医学 | 34篇 |
肿瘤学 | 3224篇 |
出版年
2024年 | 61篇 |
2023年 | 479篇 |
2022年 | 853篇 |
2021年 | 2060篇 |
2020年 | 1068篇 |
2019年 | 1711篇 |
2018年 | 2066篇 |
2017年 | 1448篇 |
2016年 | 1468篇 |
2015年 | 1620篇 |
2014年 | 2328篇 |
2013年 | 2752篇 |
2012年 | 4352篇 |
2011年 | 4243篇 |
2010年 | 2229篇 |
2009年 | 1881篇 |
2008年 | 2965篇 |
2007年 | 3070篇 |
2006年 | 2579篇 |
2005年 | 2300篇 |
2004年 | 2016篇 |
2003年 | 1691篇 |
2002年 | 1477篇 |
2001年 | 168篇 |
2000年 | 132篇 |
1999年 | 170篇 |
1998年 | 258篇 |
1997年 | 201篇 |
1996年 | 142篇 |
1995年 | 122篇 |
1994年 | 99篇 |
1993年 | 75篇 |
1992年 | 59篇 |
1991年 | 44篇 |
1990年 | 38篇 |
1989年 | 39篇 |
1988年 | 38篇 |
1987年 | 43篇 |
1986年 | 33篇 |
1985年 | 38篇 |
1984年 | 38篇 |
1983年 | 34篇 |
1982年 | 39篇 |
1981年 | 27篇 |
1980年 | 32篇 |
1979年 | 15篇 |
1978年 | 17篇 |
1974年 | 19篇 |
1973年 | 17篇 |
1972年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
91.
Sheffield MV Simsir A Talley L Roberson AJ Elgert PA Chhieng DC 《American journal of clinical pathology》2003,119(3):367-373
We compared the interobserver reproducibility of estimating the adequacy of the squamous component of conventional Papanicolaou (Pap) smears using traditional and newly proposed criteria. Forty conventional Pap smears with varying degrees of squamous cellularity were reviewed by 13 observers who evaluated adequacy (satisfactory vs unsatisfactory) based on the traditional criterion of estimating 10% slide coverage. After being introduced to the new criterion and the reference images, the observers reevaluated adequacy on the same set of smears, using the new criterion and the reference images. With the original criterion of 10% slide coverage, 15 smears had a unanimous designation; the overall kappa value was 0.49 (P < .001). With the newly proposed adequacy criterion and reference images, 17 smears had a unanimous designation; the overall kappa value was 0.60 (P < .001). The difference in the kappa correlation coefficients was statistically significant (P = .007). While traditional and newly proposed criteria resulted in fair interobserver agreement, it seemed that the newly proposed criterion, along with the use of reference images, for evaluating adequacy of the squamous component of conventional Pap smears results in better interobserver reproducibility. 相似文献
92.
The Bioperl toolkit: Perl modules for the life sciences 总被引:36,自引:4,他引:36
Stajich JE Block D Boulez K Brenner SE Chervitz SA Dagdigian C Fuellen G Gilbert JG Korf I Lapp H Lehväslaiho H Matsalla C Mungall CJ Osborne BI Pocock MR Schattner P Senger M Stein LD Stupka E Wilkinson MD Birney E 《Genome research》2002,12(10):1611-1618
The Bioperl project is an international open-source collaboration of biologists, bioinformaticians, and computer scientists that has evolved over the past 7 yr into the most comprehensive library of Perl modules available for managing and manipulating life-science information. Bioperl provides an easy-to-use, stable, and consistent programming interface for bioinformatics application programmers. The Bioperl modules have been successfully and repeatedly used to reduce otherwise complex tasks to only a few lines of code. The Bioperl object model has been proven to be flexible enough to support enterprise-level applications such as EnsEMBL, while maintaining an easy learning curve for novice Perl programmers. Bioperl is capable of executing analyses and processing results from programs such as BLAST, ClustalW, or the EMBOSS suite. Interoperation with modules written in Python and Java is supported through the evolving BioCORBA bridge. Bioperl provides access to data stores such as GenBank and SwissProt via a flexible series of sequence input/output modules, and to the emerging common sequence data storage format of the Open Bioinformatics Database Access project. This study describes the overall architecture of the toolkit, the problem domains that it addresses, and gives specific examples of how the toolkit can be used to solve common life-sciences problems. We conclude with a discussion of how the open-source nature of the project has contributed to the development effort. 相似文献
93.
Naqvi SA D'Souza WD Earl MA Ye SJ Shih R Li XA 《Physics in medicine and biology》2005,50(17):4111-4124
For a given linac design, the dosimetric characteristics of a photon beam are determined uniquely by the energy and radial distributions of the electron beam striking the x-ray target. However, in the usual commissioning of a beam from measured data, a large number of variables can be independently tuned, making it difficult to derive a unique and self-consistent beam model. For example, the measured dosimetric penumbra in water may be attributed in various proportions to the lateral secondary electron range, the focal spot size and the transmission through the tips of a non-divergent collimator; the head-scatter component in the tails of the transverse profiles may not be easy to resolve from phantom scatter and head leakage; and the head-scatter tails corresponding to a certain extra-focal source model may not agree self-consistently with in-air output factors measured on the central axis. To reduce the number of adjustable variables in beam modelling, we replace the focal and extra-focal sources with a single phase-space plane scored just above the highest adjustable collimator in a EGS/BEAM simulation of the linac. The phase-space plane is then used as photon source in a stochastic convolution/superposition dose engine. A photon sampled from the uncollimated phase-space plane is first propagated through an arbitrary collimator arrangement and then interacted in the simulation phantom. Energy deposition kernel rays are then randomly issued from the interaction points and dose is deposited along these rays. The electrons in the phase-space file are used to account for electron contamination. 6 MV and 18 MV photon beams from an Elekta SL linac are used as representative examples. Except for small corrections for monitor backscatter and collimator forward scatter for large field sizes (<0.5% with <20 x 20 cm2 field size), we found that the use of a single phase-space photon source provides accurate and self-consistent results for both relative and absolute dose calculations. 相似文献
94.
Scharf MT Woo NH Lattal KM Young JZ Nguyen PV Abel T 《Journal of neurophysiology》2002,87(6):2770-2777
Spaced training is generally more effective than massed training for learning and memory, but the molecular mechanisms underlying this trial spacing effect remain poorly characterized. One potential molecular basis for the trial spacing effect is the differential modulation, by distinct temporal patterns of neuronal activity, of protein synthesis-dependent processes that contribute to the expression of specific forms of synaptic plasticity in the mammalian brain. Long-term potentiation (LTP) is a type of synaptic modification that may be important for certain forms of memory storage in the mammalian brain. To explore the role of protein synthesis in the trial spacing effect, we assessed the protein synthesis dependence of hippocampal LTP induced by 100-Hz tetraburst stimulation delivered to mouse hippocampal slices in either a temporally massed (20-s interburst interval) or spaced (5-min interburst interval) fashion. To extend our studies to the behavioral level, we trained mice in fear conditioning using either a massed or spaced training protocol and examined the sensitivity of long-term memory to protein synthesis inhibition. Larger LTP was induced by spaced stimulation in hippocampal slices. This improvement of synaptic potentiation following temporally spaced synaptic stimulation in slices was attenuated by bath application of an inhibitor of protein synthesis. Further, the maintenance of LTP induced by spaced synaptic stimulation was more sensitive to disruption by anisomycin than the maintenance of LTP elicited following massed stimulation. Temporally spaced behavioral training improved long-term memory for contextual but not for cued fear conditioning, and this enhancement of memory for contextual fear was also protein synthesis dependent. Our data reveal that altering the temporal spacing of synaptic stimulation and behavioral training improved hippocampal LTP and enhanced contextual long-term memory. From a broad perspective, these results suggest that the recruitment of protein synthesis-dependent processes important for long-term memory and for long-lasting forms of LTP can be modulated by the temporal profiles of behavioral training and synaptic stimulation. 相似文献
95.
96.
The Chinese hamster V79 cell metabolic cooperation assay indirectlymeasures an inhibition of intercellular communication throughgap junctions and can detect many tumor promoters. The experimentsdescribed here were designed to determine whether culture mediumosmolality and pH affect the endpoint of this assay, since hypertonicsolutions and cytoplasmic acidification can uncouple gap junctionsin other systems. Hypertonic concentrations of sucrose and mannitolin medium did inhibit metabolic cooperation, but these soluteswere active over different ranges of osmolalities. In similarexperiments, sodium chloride, choline chloride and sodium glucuronatehad no effect on metabolic cooperation. Furthermore, data wereobtained indicating that osmotic effects are not likely to contributeto the inhibition of metabolic cooperation by sodium saccharin.It is concluded that hypertonic culture conditions do not necessarilycause an inhibition of metabolic cooperation, and the propertiesof an added solute are important in determining the effectsobserved. Additionally, it was found that buffering the culturemedium pH between 6.6 and 7.7, during the period when test substancesare normally present, had no effect on metabolic cooperation. 相似文献
97.
Matthew M. Clark M.A. John R. Corbisiero M.A. Mary E. Procidano Ph.D. Saul A. Grossman Ph.D. 《Community mental health journal》1984,20(4):262-268
The usefulness of assertive training for elderly psychiatric outpatients was assessed through a quasi-experimental evaluation of a program at a community geriatric facility. Elderly clients are frequently labeled as untreatable and are therefore often denied therapeutic treatment. This study is an example of the potential effectiveness of applying treatment techniques which have been developed with younger populations to a geriatric population. Nineteen clients, aged 50–75, participated in the study, either as participants in the assertion training or as members of a no-treatment control group. The assertion training consisted of 14 semi-weekly sessions, with coaching and feedback provided by the therapists. Assertive behaviors were assessed through self-report, role play and staff ratings of adaptive behaviors of clients. Pre-intervention comparisons between the groups along these dimensions were nonsignificant. However, post-test assessment indicated a significant between group difference in self-reported assertiveness-(t(17)=2.69;p<.05). Dependent t-tests indicated that the experimental group became more assertive (t(9)=2.59;p<.05), but the control group did not. Changes as assessed by role play and staff rating did not reach statistical significance. Results which indicate the potential effectiveness of assertive training with this population are discussed in terms of a specificity conceptualization of assertiveness and implications for assertive training with this population.This paper is based upon their masters' theses. 相似文献
98.
Goodman William Downing Amy Allsop Matthew Munro Julie Taylor Claire Hubbard Gill Beeken Rebecca J. 《Quality of life research》2022,31(8):2435-2444
Quality of Life Research - Quality of life can be negatively impacted by the formation of a stoma and is influenced by a number of factors. Research to date treats people with a stoma as a... 相似文献
99.
Mak Susanne Hunt Matthew Boruff Jill Zaccagnini Marco Thomas Aliki 《Advances in health sciences education : theory and practice》2022,27(3):793-815
Advances in Health Sciences Education - Professional identity is believed to foster self-confidence and resilience in health care professionals. While literature exists describing professional... 相似文献
100.
Aaron Persinger Matthew Butawan Martina Faietti Ashley Pryke Kyley Rose Marie van der Merwe Richard J. Bloomer Melissa J. Puppa 《Nutrients》2021,13(5)
Time-restricted feeding (TRF) is becoming a popular way of eating in physically active populations, despite a lack of research on metabolic and performance outcomes as they relate to the timing of food consumption in relation to the time of exercise. The purpose of this study was to determine if the timing of feeding/fasting after exercise training differently affects muscle metabolic flexibility and response to an acute bout of exercise. Male C57BL/6 mice were randomized to one of three groups for 8 weeks. The control had ad libitum access to food before and after exercise training. TRF-immediate had immediate access to food for 6 h following exercise training and the TRF-delayed group had access to food 5-h post exercise for 6 h. The timing of fasting did not impact performance in a run to fatigue despite TRF groups having lower hindlimb muscle mass. TRF-delayed had lower levels of muscle HSL mRNA expression and lower levels of PGC-1α expression but displayed no changes in electron transport chain enzymes. These results suggest that in young populations consuming a healthy diet and exercising, the timing of fasting may not substantially impact metabolic flexibility and running performance. 相似文献