全文获取类型
收费全文 | 4009篇 |
免费 | 266篇 |
国内免费 | 86篇 |
专业分类
耳鼻咽喉 | 18篇 |
儿科学 | 44篇 |
妇产科学 | 57篇 |
基础医学 | 839篇 |
口腔科学 | 136篇 |
临床医学 | 206篇 |
内科学 | 479篇 |
皮肤病学 | 114篇 |
神经病学 | 743篇 |
特种医学 | 88篇 |
外科学 | 358篇 |
综合类 | 275篇 |
现状与发展 | 2篇 |
预防医学 | 195篇 |
眼科学 | 197篇 |
药学 | 293篇 |
1篇 | |
中国医学 | 107篇 |
肿瘤学 | 209篇 |
出版年
2024年 | 8篇 |
2023年 | 80篇 |
2022年 | 147篇 |
2021年 | 189篇 |
2020年 | 155篇 |
2019年 | 130篇 |
2018年 | 126篇 |
2017年 | 129篇 |
2016年 | 116篇 |
2015年 | 111篇 |
2014年 | 225篇 |
2013年 | 229篇 |
2012年 | 194篇 |
2011年 | 220篇 |
2010年 | 202篇 |
2009年 | 197篇 |
2008年 | 203篇 |
2007年 | 193篇 |
2006年 | 174篇 |
2005年 | 144篇 |
2004年 | 117篇 |
2003年 | 126篇 |
2002年 | 90篇 |
2001年 | 79篇 |
2000年 | 81篇 |
1999年 | 66篇 |
1998年 | 63篇 |
1997年 | 64篇 |
1996年 | 47篇 |
1995年 | 40篇 |
1994年 | 34篇 |
1993年 | 32篇 |
1992年 | 34篇 |
1991年 | 35篇 |
1990年 | 36篇 |
1989年 | 31篇 |
1988年 | 36篇 |
1987年 | 30篇 |
1986年 | 22篇 |
1985年 | 30篇 |
1984年 | 11篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1975年 | 4篇 |
1972年 | 4篇 |
1971年 | 4篇 |
排序方式: 共有4361条查询结果,搜索用时 0 毫秒
1.
2.
F. Spöler M. Först Y. Marquardt D. Hoeller H. Kurz H. Merk F. Abuzahra 《Skin research and technology》2006,12(4):261-267
BACKGROUND: Three dimensional skin equivalents are widely used in dermatopharmacological and toxicological studies and as autologous transplants in wound healing. In pharmacology, there is tremendous need for monitoring the response of engineered skin equivalents to external treatment. Transplantation of skin equivalents for wound healing requires careful verification of their quality prior to transplantation. Optical coherence tomography (OCT) is a non-contact, non-destructive imaging technique for living tissues offering the potential to fulfill these needs. This work presents an analysis of OCT for high-resolution monitoring of skin equivalents at different stages during the culture process. METHODS: We developed a high-resolution OCT imaging setup based on a commercially available OCT system. A broadband femtosecond laser light source replaces the original superluminescence diode. Tomograms of living skin equivalents were recorded with an axial resolution of 3 mum and correlated with histology and immunofluorescence images. Comparison with standard low-resolution OCT is presented to emphasize the advantages of high-resolution OCT for this application. RESULTS: OCT is particularly able to distinguish between different layers of skin equivalents including stratum corneum, epidermal and dermal layer as well as the basement membrane zone. The high-resolution OCT scans correlate closely with two key benchmarks, histology and immunofluorescence imaging. CONCLUSIONS: This study clearly demonstrates the benefits of high-resolution OCT for identifying living tissue structure and morphology. Compared with the current gold standard histology, OCT offers non-destructive tissue imaging, enabling high-resolution evaluation of living tissue morphology and structure as it evolves. 相似文献
3.
M. Sh. Verbitskii Ya. N. Gotsulyak 《Bulletin of experimental biology and medicine》1997,123(1):100-104
The effects of antiovarian antiserum and monoclonal antibodies to the oolemma antigens on the ultrastructure of mouse oocytes
and their microenvironment are studied. The antioolemma monoclonal antibodies cause more pronounced degenerative changes in
the oocyte that in its microenvironment. Antiovarian antiserum induces greater changes in the microenvironment than in the
oocyte. Changes induced in the oocyte by the antiserum are secondary relative to changes occurring in the microenvironment,
while changes observed in the oocyte treated with monoclonal antibodies are primary.
Translated fromByulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 123, No. 1, pp. 115–119, January, 1997 相似文献
4.
Purpose. In the National Heart, Lung, and Blood Institute Guidelines for the Diagnosis and Management of Asthma, the expert panel recommends that a written asthma action plan be provided for all patients with asthma. Studies evaluating the usefulness of the asthma action plan in children are limited. We aim to determine exacerbation frequency and usefulness of the asthma action plan in managing exacerbations that occur in a pediatric primary care setting. Methods. Caretakers of asthmatic children attending the general pediatric clinic in an inner-city hospital completed a one-page questionnaire covering topics such as asthma severity, frequency of exacerbations, and possession/usefulness of an asthma action plan. Although controversy exists over the definition of yellow and red zone exacerbations, we defined the yellow zone as symptoms that require albuterol more than three times a day or more than two nights in succession. The red zone was defined as symptoms requiring systemic corticosteroids and/or an urgent physician visit. Results. Seventy of 75 subjects completed the survey. Almost 80% of respondents carried the diagnosis of persistent asthma, whereas the remainder had intermittent asthma. Exacerbation frequency over a 3-month period was determined. Approximately 80% of children experienced at least one yellow zone episode: 42% had one or two yellow zone episodes, and 39.6% had between three and five episodes. Sixty-three percent of patients did not experience a single red zone exacerbation. Almost 75% (44 of 59) of subjects possessed an asthma action plan. Ninety percent (37 of 41) of respondents with action plans found the plan to be useful in managing exacerbations. Conclusion. Approximately four of every five asthmatic children seen in this primary care setting experienced a yellow zone exacerbation at least once during a 3-month period. One third experienced at least one red zone episode. Nine of every 10 caretakers with an action plan reported the asthma action plan to be of value in managing exacerbations. 相似文献
5.
人精子穿卵改良试验对不同生育状态男子生育力测定的价值 总被引:2,自引:0,他引:2
目的 本研究用一种经改良的人精子穿卵试验 (SPA)处理人精子 ,以探讨一种更简便、快速、经济 ,适合一般实验室要求的方法。方法 将精子体外获能液用磷酸氢二钠把pH值调理至 8.2± 0 .2 ;用普通隔水式恒温培养箱进行培养 ;对 75例不同生育状态男子生育力进行测定 (其中 2 5例有生育力男子 ;2 5例“原因不明”不育男子 ;及 2 5例输精管吻合术后 )。结果 3种不同生育状态男子的SPA值分别是 (4 7.12± 9.92 ) % ;(2 1.73± 9.91) % ,及 (2 8.0 4± 9.91) %。前两者在统计学上有显著差异 ,(P<0 .0 1) ;后两者在统计学上无明显差异 (P >0 .0 5 )。结果表明经用改良的精子获能液并在普通恒温培养箱培养后精子的活率和活力都有较大的提高 ,这有利于精子的长期获能及提高精子的穿透能力。结论 本研究提示改良后的人精子穿卵试验处理精子确实更简便、快速、经济 ,适合一般实验室要求 ,便于推广。 相似文献
6.
Transformation of Penicillium chrysogenum using the Aspergillus nidulans amdS gene as a dominant selective marker 总被引:5,自引:0,他引:5
Summary The Aspergillus nidulans acetamidase gene (amdS) has been used to transform Penicillium chrysogenum at low frequency. Several transformants were tested and shown to be mitotically stable. Southern blot analysis indicated that transforming DNA had integrated into the chromosomal DNA, possibly at multiple sites. 相似文献
7.
Steven D. Fenster Craig C. Garner 《International journal of developmental neuroscience》2002,20(3-5):161-171
Piccolo belongs to a family of presynaptic cytoskeletal proteins likely to be involved in the assembly and function of presynaptic active zones as sites of neurotransmitter release. Given that abnormalities in the formation of synaptic junctions are thought to contribute to cognitive dysfunction during brain development, we have analyzed and compared the gene structure of the Piccolo gene, PCLO, from humans and mice and determined their chromosomal localization. A comparison of the deduced amino acid sequence of cDNA clones encoding Piccolo from human, mouse, rat and chicken reveals the presence of distinct homology domains. Only subsets of these are also present in the structurally related active zone protein Bassoon indicating that Piccolo and Bassoon perform related but distinct functions at active zones. Characterization of the PCLO gene reveals the presence of 25 coding exons spread over 380kb of genomic DNA. The human PCLO gene maps to 7q11.23-q21.3, a region of chromosome 7 implicated as a linkage site for autism and Williams Syndrome suggesting that alterations in the expression of Piccolo or the PCLO gene could contribute to developmental disabilities and mental retardation. 相似文献
8.
New neurons are known to be generated in the brain of adult mammals throughout their entire life in the area of the lateral ventricles and the subgranular zone of the dentate gyrus. The regulatory mechanisms of neurogenesis are complex and poorly understood. Numerous studies performed during the last decade have shown that the intensity of generation of new cells in the germinative regions of the brain is significantly influenced by various environmental factors. Pronounced changes in neurogenesis were also found in the models of various pathologies of the central nervous system (such as neurodegeneration, brain ischemia, and epilepsy). This review is focused on the regulation of neurogenesis in the brain of adult mammals in the course of experimental epilepsy. The involvement of nitric oxide and gamma-aminobutyric acid in the regulation of the proliferation and differentiation of brain cells during seizure activity is discussed. 相似文献
9.
Schwann cell invasion of the conus medullaris: case report 总被引:1,自引:0,他引:1
As Schwann cells possess regenerative capabilities there is intense interest concerning their role in central nervous system (CNS) regeneration. We report on a case of an intramedullary schwannoma involving the conus medullaris and spinal cord above it. We discuss the possible origin of these cells and the mechanisms by which these cells may invade the CNS. We offer imaging and discuss experimental studies to support our hypothesis. This case concerns a 48-year-old man, who presented with a 6-month history of bilateral lower extremity weakness. Magnetic resonance imaging (MRI) revealed an intramedullary tumour extending from the conus to T11. At operation, following laminectomy and durotomy, a schwannoma was dissected free from the conus. Total gross resection of tumour was achieved. The patient made an uneventful and full recovery. This case shows that Schwann cells can invade the CNS. Manipulation of the transitional zone astrocytic barrier may offer a potential avenue for Schwann cells to enter the CNS in pathological states. 相似文献
10.
Edward J. Ciaccio PhD Hiroshi Ashikaga MD PhD Riyaz A. Kaba MD Daniel Cervantes MD Bruce Hopenfeld PhD Andrew L. Wit PhD Nicholas S. Peters MD PhD Elliot R. McVeigh PhD Hasan Garan MD James Coromilas MD 《Heart rhythm》2007,4(8):1034-1045
BACKGROUND: Infarct border zone (IBZ) geometry likely affects inducibility and characteristics of postinfarction reentrant ventricular tachycardia, but the connection has not been established. OBJECTIVE: The purpose of this study was to determine characteristics of postinfarction ventricular tachycardia in the IBZ. METHODS: A geometric model describing the relationship between IBZ geometry and wavefront propagation in reentrant circuits was developed. Based on the formulation, slow conduction and block were expected to coincide with areas where IBZ thickness (T) is minimal and the local spatial gradient in thickness (DeltaT) is maximal, so that the degree of wavefront curvature rho proportional, variant DeltaT/T is maximal. Regions of fastest conduction velocity were predicted to coincide with areas of minimum DeltaT. In seven arrhythmogenic postinfarction canine heart experiments, tachycardia was induced by programmed stimulation, and activation maps were constructed from multichannel recordings. IBZ thickness was measured in excised hearts from histologic analysis or magnetic resonance imaging. Reentrant circuit properties were predicted from IBZ geometry and compared with ventricular activation maps after tachycardia induction. RESULTS: Mean IBZ thickness was 231 +/- 140 microm at the reentry isthmus and 1440 +/- 770 microm in the outer pathway (P <0.001). Mean curvature rho was 1.63 +/- 0.45 mm(-1) at functional block line locations, 0.71 +/- 0.18 mm(-1) at isthmus entrance-exit points, and 0.33 +/- 0.13 mm(-1) in the outer reentrant circuit pathway. The mean conduction velocity about the circuit during reentrant tachycardia was 0.32 +/- 0.04 mm/ms at entrance-exit points, 0.42 +/- 0.13 mm/ms for the entire outer pathway, and 0.64 +/- 0.16 mm/ms at outer pathway regions with minimum DeltaT. Model sensitivity and specificity to detect isthmus location was 75.0% and 97.2%. CONCLUSIONS: Reentrant circuit features as determined by activation mapping can be predicted on the basis of IBZ geometrical relationships. 相似文献