全文获取类型
收费全文 | 18995篇 |
免费 | 1469篇 |
国内免费 | 30篇 |
专业分类
耳鼻咽喉 | 177篇 |
儿科学 | 702篇 |
妇产科学 | 604篇 |
基础医学 | 2548篇 |
口腔科学 | 209篇 |
临床医学 | 2481篇 |
内科学 | 3281篇 |
皮肤病学 | 297篇 |
神经病学 | 2248篇 |
特种医学 | 362篇 |
外科学 | 1761篇 |
综合类 | 182篇 |
现状与发展 | 1篇 |
一般理论 | 20篇 |
预防医学 | 2793篇 |
眼科学 | 185篇 |
药学 | 1210篇 |
1篇 | |
中国医学 | 15篇 |
肿瘤学 | 1417篇 |
出版年
2024年 | 35篇 |
2023年 | 230篇 |
2022年 | 356篇 |
2021年 | 778篇 |
2020年 | 485篇 |
2019年 | 679篇 |
2018年 | 759篇 |
2017年 | 575篇 |
2016年 | 646篇 |
2015年 | 652篇 |
2014年 | 794篇 |
2013年 | 1216篇 |
2012年 | 1726篇 |
2011年 | 1722篇 |
2010年 | 854篇 |
2009年 | 749篇 |
2008年 | 1158篇 |
2007年 | 1245篇 |
2006年 | 1098篇 |
2005年 | 1000篇 |
2004年 | 934篇 |
2003年 | 777篇 |
2002年 | 752篇 |
2001年 | 94篇 |
2000年 | 73篇 |
1999年 | 95篇 |
1998年 | 131篇 |
1997年 | 108篇 |
1996年 | 74篇 |
1995年 | 74篇 |
1994年 | 53篇 |
1993年 | 49篇 |
1992年 | 43篇 |
1991年 | 27篇 |
1990年 | 19篇 |
1989年 | 29篇 |
1988年 | 27篇 |
1987年 | 28篇 |
1986年 | 31篇 |
1985年 | 17篇 |
1984年 | 43篇 |
1983年 | 17篇 |
1982年 | 36篇 |
1981年 | 35篇 |
1980年 | 22篇 |
1979年 | 13篇 |
1978年 | 13篇 |
1977年 | 7篇 |
1976年 | 12篇 |
1975年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 23 毫秒
91.
Active maintenance of sentence meaning in working memory: evidence from EEG coherences. 总被引:3,自引:0,他引:3
The active maintenance of sentence meaning in working memory was investigated using event-related electroencephalogram (EEG) coherences. Participants read a sentence, retained it for 2.5 s, and then verified a statement about its meaning. The sentences contained either three semantically related nouns or unrelated nouns and started either with a what phrase (WH sentences) or not (non-WH sentences), imposing either a high or low demand on verbal working memory. Comprehension accuracy showed an interaction of semantic relatedness and sentence type due to the presence of a relatedness effect (lower accuracy in the unrelated condition) in WH sentences but not in non-WH sentences. During the post-sentence retention interval, EEG coherences also displayed this interaction of relatedness and sentence type. A semantic relatedness effect was obtained in the WH sentences (high demand) but not in the non-WH sentences (low demand). In addition, compared to a pre-sentence baseline and sentence presentation, coherences increased in the 10-14 Hz band during retention and decreased in the 4-6 Hz band. These coherence changes spanned prefrontal and posterior brain regions, possibly reflecting increased synchronization in projection loops between attention control systems in prefrontal cortex and activated meaning representations in semantic memory in posterior cortex. These findings suggest that short-term retention of the meaning of a sentence involves active maintenance in a capacity-limited working memory, accompanied by a heightened inner direction of attention after sentence presentation. 相似文献
92.
Grant-Tschudy KS Wira CR 《American journal of reproductive immunology (New York, N.Y. : 1989)》2004,52(4):252-262
PROBLEM: The effects of estradiol on epithelial cell function in the uterus may either be direct or indirect through the paracrine effects of underlying stromal cells. The aim of this study was to test whether estradiol-17beta (E(2)) acts directly to regulate uterine epithelial cell monolayer integrity. METHODS OF STUDY: Mouse uterine epithelial cells were isolated and grown on cell culture inserts to form confluent, polarized monolayers, as indicated by the development of high transepithelial resistance (TER). RESULTS: When polarized epithelial cells were treated with E(2), TER was significantly decreased within 24 hr of exposure. Epithelial cells remained hormonally responsive in culture for at least 10 days. In contrast to estradiol, incubation with progesterone, cortisol, aldosterone, and DHT had no effect on uterine epithelial cell TER. The ability of E(2) to decrease TER was inhibited following co-incubation with ICI 182,780, a pure estrogen receptor antagonist. To further investigate the mechanism involved in estradiol-induced decreases in TER, we tested the effect of TAPI-0, an inhibitor of matrix metalloproteinases. Our findings indicate that TAPI-0 reversed the inhibitory effect of E(2) on TER. CONCLUSIONS: These studies demonstrate that epithelial monolayer integrity is directly influenced by E(2) and ER mediated. Further, it suggests that the mechanism through which estradiol decreases TER is mediated by matrix metalloproteinases. 相似文献
93.
Biparental Phodopus campbelli and uniparental P. sungorus juvenile litters (2 males, 2 females) both consumed amniotic fluid and placenta during the birth of younger siblings. Three days later, P. campbelli juveniles were most responsive to a displaced younger sibling. Thus, P. campbelli are responsive to pups as juvenile alloparents and as new parents; however, at intervening ages, infanticidal attack (bite) was seen. At 5, 7, 9, 11, or 13 weeks of age, male and female P. campbelli were given a 5-min test with an unrelated, 3-day-old, anesthetized pup. Females attacked more often than males, yet pup-retrieval rates did not differ. Female aggression increased with age and was replaced by retrieval behavior 3 days after parturition. Male attack ceased after a birth, but parental behavior did not increase, remaining below the rate for new fathers tested with their own awake pup. Over repeated testing, behavior in one test did not predict behavior in another. Transitions from caregiving alloparent to infanticidal adult and back to parental care were clear in females, but less discrete with this stimulus paradigm in these highly paternal males. 相似文献
94.
Dawn E. Colwell Katherine A. Gollahon Jerry R. McGhee Suzanne M. Michalek 《Journal of immunological methods》1982,54(2):259-266
An immunization regimen has been developed which yields a high frequency of hybridomas producing IgA isotype, antigen-specific antibody when spleen cells from immunized mice are fused with non-immunoglobulin secreting murine myeloma cells. Germfree BALB/c mice were carrier-primed with sheep erythrocytes (SRBC) by gastric intubation (GI) for 2 consecutive days followed 1 week later by GI with trinitrophenyl (TNP)-haptenated SRBC. After 7 days, spleen cells were fused with non-immunoglobulin secreting myeloma cells (X63-Ag8.653), and 2–3 weeks later, culture wells were scored for hybrid clones. Of 240 culture wells plated, 157 wells (65.4%) exhibited clones producing anti-TNP antibodies as determined by enzyme-linked immunosorbent assay. A total of 50 specific cell lines were established, of which 27 clones (54%) produced IgA isotype anti-TNP antibodies, while the anti-TNP antibodies produced by the remaining 23 clones were approximately equally distributed between the IgM and IgG isotypes. The IgA and IgM monoclonal antibodies were more effective in hemagglutinating TNP-SRBC than were IgG isotype antibodies. This study describes a method for production of a high number of antigen-specific IgA hybridomas which will allow production of IgA monoclonal antibodies to important antigens on mucosally-associated pathogens, and thus allow elucidation of functions of IgA antibody at mucosal surfaces. 相似文献
95.
Katherine H. Tsai Andrew L. Moskowitz Roxanna E. Lynch Eric Daleiden Charles Mueller Jennifer L. Krull 《Journal of clinical child and adolescent psychology》2019,48(2):S72-S78
We investigated whether a service-planning document outlining recommendations for what providers should address in treatment (i.e., targets) and the associated clinical techniques they should employ (i.e., practices) influenced the targets and practices that providers reported actually implementing during the subsequent treatment episode. Participants included 94 youths ages 4 to 17 (M = 13.57, SD = 3.59) who received community-based mental health services from the Hawai'i Child and Adolescent Mental Health Division. Data on targets and practices were compared across initial Mental Health Treatment Plans and Monthly Treatment and Progress Summaries. Data were analyzed using two-level, generalized mixed effects models with two-way cross-classification or linear mixed effects models. Providers were more likely to report the use of targets and practices in treatment if they were included within the treatment plan. In addition, the more closely targets addressed during treatment followed the recommended targets from the treatment plan, the more closely implemented practices followed the recommended practices listed in the treatment plan. Furthermore, as providers shifted their focus to different targets, a shift in their use of practices was also evident over time. Last, practices for which there is demonstrated efficacy for particular targets were more likely to be used. Service planning documents appear to help organize care; however, results also suggest possible limitations to the current system. These findings highlight potential areas for improvement in planning and care delivery. 相似文献
96.
We previously demonstrated susceptibility of Leishmania sp. to glibenclamide, a K+-ATP transport blocker which interacts with members of the superfamily of adenosine 5′ triphosphate-binding cassette transporters.
In order to characterize the molecular differences between a sensitive Leishmania strain, NR(Gs), and an experimentally selected glibenclamide-resistant strain, NR(Gr), specific biochemical and functional
parameters have been evaluated both in the wild type and in the resistant strain. Most noteworthy, NR(Gr) exhibit an increased
expression of P-glycoprotein and a decreased activity of functional key enzymes such as acid phosphatase, a prominent virulent
factor of the parasite, and pyruvate kinase, a key control enzyme for both carbohydrate and protein metabolism. The specific
biochemical, metabolic and functional changes observed in the resistant strain correlated with a reduced infectivity of stationary
phase NR(Gr) in J774 macrophages and suggested a mechanism to overcome the effect of glibenclamide.
Received: 21 January 2000 / Accepted: 1 March 2000 相似文献
97.
Andrea M. Gross Megan Frone Karen W. Gripp Bruce D. Gelb Lisa Schoyer Lisa Schill Beth Stronach Leslie G. Biesecker Dominic Esposito Edjay Ralph Hernandez Eric Legius Mignon L. Loh Staci Martin Deborah K. Morrison Katherine A. Rauen Pamela L. Wolters Dina Zand Frank McCormick Sharon A. Savage Douglas R. Stewart Brigitte C. Widemann Marielle E. Yohe 《American journal of medical genetics. Part A》2020,182(4):866-876
RASopathies caused by germline pathogenic variants in genes that encode RAS pathway proteins. These disorders include neurofibromatosis type 1 (NF1), Noonan syndrome (NS), cardiofaciocutaneous syndrome (CFC), and Costello syndrome (CS), and others. RASopathies are characterized by heterogenous manifestations, including congenital heart disease, failure to thrive, and increased risk of cancers. Previous work led by the NCI Pediatric Oncology Branch has altered the natural course of one of the key manifestations of the RASopathy NF1. Through the conduct of a longitudinal cohort study and early phase clinical trials, the MEK inhibitor selumetinib was identified as the first active therapy for the NF1‐related peripheral nerve sheath tumors called plexiform neurofibromas (PNs). As a result, selumetinib was granted breakthrough therapy designation by the FDA for the treatment of PN. Other RASopathy manifestations may also benefit from RAS targeted therapies. The overall goal of Advancing RAS/RASopathy Therapies (ART), a new NCI initiative, is to develop effective therapies and prevention strategies for the clinical manifestations of the non‐NF1 RASopathies and for tumors characterized by somatic RAS mutations. This report reflects discussions from a February 2019 initiation meeting for this project, which had broad international collaboration from basic and clinical researchers and patient advocates. 相似文献
98.
Mark H. Pollack Michael W. Otto Gary S. Sachs Andrew Leon M. Katherine Shear Joseph A. Deltito Martin B. Keller Jerrold F. Rosenbaum 《Journal of affective disorders》1994,30(4):273-281
This study examines clinical predictors of outcome for patients with panic disorder and depression in a 16 week, placebo-controlled trial of alprazolam and imipramine (n = 126). Baseline global severity of illness and phobic avoidance were differentially predictive of acute response to treatment. Patients in the mild to moderate range of global distress experienced smaller degrees of improvement on alprazolam than on imipramine at week 4. At endpoint, the relative effectiveness of the active medication versus placebo was diminished in patients with higher levels of phobic avoidance. This relationship was not evident for completers, suggesting that the adverse effects of avoidance on outcome after sustained treatment was reduced. 相似文献
99.
Three influenza viruses, A/Puerto Rico/8/34-A/England/939/69 clone 7a (H3N2), A/Fiji/15899/83 (H1N1), and A/Victoria/3/75 (H3N2), induce different levels of apoptosis in vitro at equal moi; Clone 7a > A/Victoria > A/Fiji. Previous studies have shown that several viral proteins from clone 7a and A/Fiji, including PB2, NA, NS1, M1, and M2, induce apoptosis when expressed individually fused to the herpes simplex virus tegument protein, VP22. However, this did not reflect viral protein-protein-RNA interactions known to occur within infected cells. To explore the role of viral proteins in apoptosis under infection conditions, recombinant viruses with single or triple gene exchanges were generated using A/Victoria or clone 7a as the background virus. Inserting the A/Fiji NS or PB2 gene into A/Victoria or clone 7a significantly reduced the level of apoptosis compared to the parent virus while clone 7a PA or NP genes increased apoptosis. Inserting A/Fiji NA or HA or clone 7a NS, M, NA, or HA genes individually into A/Victoria had no significant effect on apoptosis. Surprisingly, inserting the M, NA, and HA genes of A/Fiji together into clone 7a reduced apoptosis, whereas inserting clone 7a M, NA, and HA together into A/Fiji increased apoptosis. These results suggest that no single virus protein induces apoptosis and that the combination of genes required may be strain specific, highlighting the difficulty of predicting the virulence of new strains that arise in nature. No support for the view that apoptosis is essential for high virus yields was obtained as high virus yields were obtained with viruses that induced both high and low levels of apoptosis. 相似文献
100.
Chorneyko K Giesler R Sabatino D Ross C Lobo F Shuhaibar H Chen V Elavathil L Denardi F Ansari S Salama S LeBlanc V Norman G Sheridan B Riddell R 《American journal of clinical pathology》2002,117(5):783-790
Telepathology (TP) uses telecommunication linkages to electronically capture, store, retrieve, and transmit images to distant sites. We assessed the feasibility of a dynamic real-time TP system for light microscopic (LM) diagnosis of anatomic pathology specimens, including frozen sections. Six pathologists, in 2 separate periods, read a set of 160 retrospectively retrieved slides (80 of which were frozen sections) by TP and LM. Reading times were recorded. Diagnoses were compared with the reference diagnosis (established by a group of 5 independent pathologists) and graded on a scale of 0 to 2 (2, correct; 1, incorrect but no clinical impact; 0, incorrect with clinical impact). Overall, LM was more accurate than TP compared with the reference diagnosis (score, 1.68 vs 1.54). There was no difference in accuracy between frozen section and paraffin-embedded tissue. Intraobserver agreement ranged from 82.5% to 88.2%. The average reading time was 6.0 minutes for TP and 1.4 minutes for LM. During the study, reading time decreased for TP but not for LM. These results show that despite marginally lower accuracy and longer reading times, TP isfeasible for routine light microscopic diagnosis, including frozen sections. 相似文献