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   10442篇
  免费   678篇
  国内免费   40篇
耳鼻咽喉   70篇
儿科学   234篇
妇产科学   185篇
基础医学   1524篇
口腔科学   289篇
临床医学   813篇
内科学   2305篇
皮肤病学   186篇
神经病学   875篇
特种医学   986篇
外科学   1731篇
综合类   75篇
一般理论   1篇
预防医学   544篇
眼科学   150篇
药学   514篇
  1篇
中国医学   8篇
肿瘤学   669篇
  2023年   96篇
  2022年   201篇
  2021年   370篇
  2020年   232篇
  2019年   282篇
  2018年   347篇
  2017年   210篇
  2016年   290篇
  2015年   336篇
  2014年   394篇
  2013年   429篇
  2012年   654篇
  2011年   625篇
  2010年   432篇
  2009年   349篇
  2008年   523篇
  2007年   532篇
  2006年   536篇
  2005年   530篇
  2004年   434篇
  2003年   363篇
  2002年   359篇
  2001年   127篇
  2000年   121篇
  1999年   121篇
  1998年   93篇
  1997年   97篇
  1996年   68篇
  1995年   55篇
  1994年   63篇
  1993年   53篇
  1992年   59篇
  1991年   70篇
  1990年   80篇
  1989年   51篇
  1988年   51篇
  1987年   62篇
  1986年   42篇
  1985年   53篇
  1984年   45篇
  1983年   32篇
  1981年   35篇
  1978年   34篇
  1932年   46篇
  1931年   31篇
  1929年   32篇
  1927年   37篇
  1924年   45篇
  1923年   52篇
  1922年   55篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Notfall + Rettungsmedizin - Der plötzliche Brust- und der plötzliche Unterleibsschmerz gehören zu den häufigsten Gründen, die Patienten in die Notaufnahme führen. Das...  相似文献   
92.
93.
Highly effective CFTR modulator drug therapy is increasingly available to those with cystic fibrosis. Multiple observational research studies are now being conducted to better understand the impacts of this important therapeutic milestone on long-term outcomes, patient care needs, and future research priorities. PROMISE is a large, multi-disciplinary academic study focused on the broad impacts of starting elexacaftor/tezacaftor/ivacaftor in the US population age 6 years and older. The many areas of investigation and rationale for each are discussed by organ systems, along with recognition of remaining important questions that will not be addressed by this study alone. Knowledge gained through this and multiple complementary studies around the world will help to understand important health outcomes, clinical care priorities, and research needs for a large majority of people treated with these or similarly effective medications targeting the primary cellular impairment in cystic fibrosis.  相似文献   
94.
Embryo implantation involves adhesion of trophoblast cells to the epithelial lining of the endometrium. Using an in-vitro model to simulate this initial interaction, we previously reported that attachment of human trophoblast-like JAR spheroids to human uterine epithelial RL95-2 cells provokes a Ca(2+) influx in RL95-2 cells depending on apically localized integrin receptors. Here, we demonstrate that adhesiveness of RL95-2 cells for JAR spheroids, measured by a centrifugal force-based adhesion assay, is dependent on Rho GTPases, most likely RhoA. Cellular expression and distribution of RhoA were studied by fluorescence confocal microscopy, focusing on the localization of RhoA and F-actin within the adhesion sites between JAR and RL95-2 cells. Contact areas contained high amounts of RhoA and F-actin fibres near the plasma membrane. To determine whether Rho GTPases may influence JAR cell binding, we treated RL95-2 cells with Clostridium difficile toxin A, which specifically inactivates Rho GTPases. Toxin A treatment changed the subcellular distribution of endogenous RhoA in RL95-2 cells and altered RhoA and F-actin colocalization. Adhesion of JAR spheroids to RL95-2 cells treated with toxin A was largely suppressed. These data indicate that Rho GTPases, most likely RhoA, play an important role in uterine epithelial RL95-2 cells for trophoblast binding, and suggest that RhoA may be involved in local signalling cascades during early embryo implantation in vivo.  相似文献   
95.
Summary Based on national mortality data, the frequency of hip fractures in elderly people was compared between Switzerland and Japan. Age-adjusted annual incidence rates per 100 000 population estimated for Swiss persons over 60 years were around 150 and 200 in males and around 450 in females, while for the Japanese they were only 132 in males and 285 in females. Age-adjusted death rates from hip fracture for the Swiss over 60 were 20.0 in males and 28.9 in females, while for the Japanese they were only 1.6 in males and 2.7 in females. The inclination of the age-dependent slope in hip fracture mortality rates was substantially the same in both countries, but there was a lag time of approximately 10 years in Japan. Remarkably, the proportion of deaths due to falls among all accidental deaths was several times greater in both sexes for the Swiss than for the Japanese. This differential might be an important underlying reason for the observed difference between death rates of hip fracture in Switzerland and Japan. Other known behavioral risk factors for hip fracture such as diet, exercise, estrogen use etc. are unlikely to explain the observed difference in hip fracture mortality and morbidity between Switzerland and Japan. However, given the doubts on the reliability and thus comparability of the available data on mortality and morbidity, the present findings should be regarded as preliminary. In conclusion, we believe that the unexplained and large difference in the burden of hip fracture between Switzerland and Japan merits further studies, including new aetiological hypotheses.
Zusammenfassung Gestützt auf nationale Sterbedaten wird die Häufigkeit von Hüftfrakturen bei Betagten in der Schweiz und Japan verglichen. Alterskorrigierte jährliche Inzidenzraten (bezogen auf 100 000 Einwohner) bezifferten sich bei den Schweizer Personen über 60 Jahren auf ca. 150–200 bei den Männern sowie ca. 450 bei den Frauen, während bei den Japanern die entsprechenden Inzidenzen lediglich 132 bei den Männern und 285 bei den Frauen betrugen. Die alterskorrigierte durch Hüftfrakturen bedinte Mortalität (pro 100000) betrug bei den Schweizern über 60 Jahren 20,0 bei den Männern und 28,9 bei den Frauen, während bei den Japanern die entsprechenden Werte bei 1,6 für Männer und 2,7 für Frauen lagen. Die Gerade, die das Verhältnis zwischen Alter und Hüftfraktur-Mortalität charakterisiert, zeigte in beiden Ländern ungefähr die gleiche Steigung, war in Japan jedoch um ca. 10 Jahre rechtsverschoben. Bemerkenswerterweise war der Anteil sturzbedingter Todesfälle unter allen unfallbedingten Todesfällen bei beiden Geschlechtern in der Schweiz wesentlich höher als in Japan. Dieser Unterschied könnte eine wichtige, zurgrundeliegende Ursache für die Differenz in der Hüftfrakturmortalität zwischen der Schweiz und Japan darstellen. Andere verhaltensabhängige Risikofaktoren für Hüftfraktur wie Ernährung, körperliche Bewegung, Oestrogenzufuhr usw. vermögen die beobachteten Unterschiede in der Mortalität und Morbidität an Hüftfraktur zwischen der Schweiz und Japan kaum zu erklären Angesichts der ungewissen Reliabilität und Vergleichbarkeit der zur Verfügung stehenden Daten müssen die vorliegenden Ergebnisse allerdings mit Vorsicht interpretiert werden. Zusammenfassend glauben wir, dass der grosse und weitgehend unerklärte schweizerisch-japanische Unterschied im Auftreten von Hüftfrakturen weiter abgeklärt werden sollte, unter Einschluss neuer ätiologischer Hypothesen.

Résumé Basée sur les données de mortalité nationales, la fréquence des fractures de hanche des personnes âgées est comparée entre la Suisse et le Japon. Les taux d'incidence annuels corrigés pour l'effet de l'âge chez les personnes suisses âgées de plus de 60 ans sont d'environ 150–200 chez les hommes (par rapport à 100 000 habitants), ainsi qu'environ 450 chez les femmes, tandis qu'au Japon les incidences correspondantes s'élèvent à 132 chez les hommes et 285 chez les femmes. La mortalité des fractures de hanche, corrigée pour l'effet de l'âge s'élève chez les Suisses âgés de plus de 60 ans à 20,0 (par 100 000) chez les hommes et à 28,9 chez les femmes, alors que chez les Japonais les taux correspondants sont 1,6 chez les hommes et 2,7 chez les femmes. La proportion de décès faisant suite à des chutes parmi l'ensemble des accidents mortels est remarquablement plus élevée en Suisse qu'au Japon, pour les femmes comme pour les hommes. Cette différence pourrait expliquer le taux élvé de décès suite à une fracture de hanche observé en Suisse. D'autres facteurs de risque pour la fracture de hanche liés au style de vie ne sont apparemment pas en mesure d'expliquer les différences de mortalité et de morbidité par fracture de hanche observées entre la Suisse et le Japon. Face aux doutes qui concernent la fiabilité et la comparabilité des données à disposition, ces résultats doivent être interprétés avec prudence. Toutefois, nous pensons que la différence substantielle des taux de fractures de hanche entre Suisse et Japon, qui reste inexpliquée, devrait être examinée plus en détail, également en ce qui concerne de nouvelles hypothèses étiologiques.
  相似文献   
96.
目的 研究妇科腹腔镜术后深静脉血栓的发生率。方法 在澳大利亚悉尼Liverpool医院 1997年 5月~ 1997年 9月 72例妇科腹腔镜手术采用Doppler超声检查静脉血流的通畅性和血管腔内的回声团用以诊断深静脉血栓。 61例患者充气时间 <60分钟为小手术组 ,11例 >60分钟为大手术组。每例患者在术后 2 4小时内及术后 7天行两次超声Doppler检查 ,所有 72人均行术后 2 4小时内的超声Doppler检查 ,小手术组 61例中 4 0例、大手术组 11例中 9例行二次超声检查。 2 3例未行二次超声检查者均行电话随访。结果 在我们的研究中两组患者均未发现DVT。本文同时报道北京复兴医院一例腹腔镜下右卵巢巧克力囊肿剥除术、左卵巢及部分输卵管切除术患者术后并发DVT ,其诊断及治疗经过。结论 这项研究证实妇科腹腔镜手术DVT虽发生率极低 ,一旦发生需及时诊治 ,以免发生肺栓塞等致命并发症。  相似文献   
97.
Organic, solid-state batteries require efficient solid electrolytes able to provide stable ion conduction. Here, solid electrolytes based on ionic liquid (IL) polymers with chloride counterions as electrolyte materials for batteries are presented. Acrylic monomers with imidazolium substituents with alkyl side groups that are linked by alkyl spacers to the acrylic group are employed. The IL monomers with chloride counterions are either converted by thermally initiated radical polymerization into linear homopolymers or incorporated into polymer networks by UV-initiated copolymerization utilizing a bifunctional, non-ionic cross-linker. Both procedures successfully yielded the desired materials, which is confirmed by NMR spectroscopy (linear homopolymers) or Raman spectroscopy (IL networks). The ionic conductivities at room temperature are measured by Electrochemical Impedance Spectroscopy. The ionic conductivities of the linear homopolymers are in the range of 10−4 to 10−6 S cm−1, while those of the IL networks are about two orders of magnitude lower. They increase to 10−4 S cm−1 at 70 °C. The electrochemical stability is examined by Linear Sweep Voltammetry and is proven in the voltage range of −2 to +2 V. The results reveal that the materials represent promising electrolytes for potential solid-state battery applications.  相似文献   
98.
Suspension-cultured tomato cells react to microbial signals, so-called elicitors, with rapid alkalinization of the growth medium and increased biosynthesis of the stress hormone ethylene. These responses to elicitors can be blocked by staurosporine and K-252a, two specific inhibitors of protein kinases. Here we show that calyculin A, a potent inhibitor of protein phosphatases, mimics the action of elicitors and, at nanomolar concentrations, induces medium alkalinization as well as a strong increase in the activity of 1-aminocyclopropane-1-carboxylate synthase, the key enzyme of ethylene biosynthesis. Both responses were strongly inhibited by K-252a, and calyculin A induced both responses more rapidly than did a fungal elicitor, xylanase. For example, the lag phase for medium alkalinization was only 0.2-0.4 min for calyculin A, compared with 2 min for xylanase. To study changes in the dynamics of protein phosphorylation, cells were labeled with 30-sec pulses of [33P]orthophosphate. Calyculin A strongly increased phosphorylation of several polypeptide bands within 40 sec of treatment. The same phosphorylated bands also appeared in response to xylanase, but only after a lag phase of 2-3 min. These results show that the protein phosphatase inhibitor calyculin A leads to rapid hyperphosphorylation of specific proteins in cultured cells and indicate that elicitor action could be based on inhibition of a protein phosphatase as well as on activation of a protein kinase.  相似文献   
99.
In recent years, the technology and methodology have been developed to help you identify, collect, analyze, and apply health status information about the community you serve. Called a population-based community health status assessment, this tool is not intended to help you identify "needs"--you probably already know what many of them are in your community. Rather, it allows you to develop precise indicators of the health status of the community in general as well as of specific subgroups with particular health problems and risk factors. The assessment is useful both for the data and insights it provides and for organizing, implementing, and evaluating community health improvement interventions. Seven steps for the successful design and implementation of a population-based community health status assessment follow.  相似文献   
100.
Non-invasive detection of small temperature changes (< 1 degree C) is pivotal to the further advance of regional hyperthermia as a treatment modality for deep-seated tumours. Magnetic resonance (MR) thermography methods are considered to be a promising approach. Four methods exploiting temperature-dependent parameters were evaluated in phantom experiments. The investigated temperature indicators were spin-lattice relaxation time T1, diffusion coefficient D, shift of water proton resonance frequency (water PRF) and resonance frequency shift of the methoxy group of the praseodymium complex (Pr probe). The respective pulse sequences employed to detect temperature-dependent signal changes were the multiple readout single inversion recovery (T One by Multiple Read Out Pulses; TOMROP), the pulsed gradient spin echo (PGSE), the fast low-angle shot (FLASH) with phase difference reconstruction, and the classical chemical shift imaging (CSI). Applying these sequences, experiments were performed in two separate and consecutive steps. In the first step, calibration curves were recorded for all four methods. In the second step, applying these calibration data, maps of temperature changes were generated and verified. With the equal total acquisition time of approximately 4 min for all four methods, the uncertainties of temperature changes derived from the calibration curves were less than 1 degree C (Pr probe 0.11 degrees C, water PRF 0.22 degrees C, D 0.48 degrees C and T1 0.93 degrees C). The corresponding maps of temperature changes exhibited slightly higher errors but still in the range or less than 1 degree C (0.97 degrees C, 0.41 degrees C, 0.70 degrees C, 1.06 degrees C respectively). The calibration results indicate the Pr probe method to be most sensitive and accurate. However, this advantage could only be partially transferred to the thermographic maps because of the coarse 16 x 16 matrix of the classical CSI sequence. Therefore, at present the water PRF method appears to be most suitable for MR monitoring of small temperature changes during hyperthermia treatment.  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