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   12238篇
  免费   1118篇
  国内免费   5篇
  2023年   57篇
  2022年   51篇
  2021年   157篇
  2020年   106篇
  2019年   129篇
  2018年   160篇
  2017年   138篇
  2016年   263篇
  2015年   350篇
  2014年   449篇
  2013年   581篇
  2012年   765篇
  2011年   794篇
  2010年   492篇
  2009年   474篇
  2008年   692篇
  2007年   657篇
  2006年   658篇
  2005年   632篇
  2004年   665篇
  2003年   611篇
  2002年   597篇
  2001年   161篇
  2000年   133篇
  1999年   172篇
  1998年   168篇
  1997年   146篇
  1996年   150篇
  1995年   116篇
  1994年   130篇
  1993年   133篇
  1992年   136篇
  1991年   114篇
  1990年   117篇
  1989年   99篇
  1988年   111篇
  1987年   111篇
  1986年   96篇
  1985年   99篇
  1984年   105篇
  1983年   104篇
  1982年   103篇
  1981年   101篇
  1980年   91篇
  1979年   73篇
  1978年   66篇
  1977年   60篇
  1976年   66篇
  1974年   64篇
  1973年   59篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
Three cases of xylene poisoning occurred after prolonged inhalation of paint fumes. Analysis showed that xylene comprised more than 90% of the solvent in the paint, the total solvent comprising 34% of the paint by weight. One patient was dead on admission, while the other two recovered after at least 15 hours'' loss of consciousness. Both patients had transient liver cell damage, and one temporary impairment of renal function.  相似文献   
122.
RA233, a new pyrimido-pyrimidine compound, is a powerful inhibitor of platelet function tested in vitro; it inhibits calcium and adenosine diphosphate (A.D.P.)-induced platelet aggregation, inhibits the retention of platelets by glass beads, decreases the release of platelet factor 3 by kaolin, and inhibits clot retraction. In some in-vitro systems RA233 is significantly more potent that its analogue RA433 in inhibiting platelet function.  相似文献   
123.
Space biomagnetics   总被引:1,自引:0,他引:1  
Astronauts who venture from their spacecraft onto the lunar surface and the surfaces of our neighboring planets will be exposed for a few hours in duration to magnetic-field intensities which are markedly less than that of the earth's field. The intensities of magnetic fields to which they will be exposed while inside their spacecraft can be stated only after completing a detailed survey of the contribution made to these fields by the functioning electronic components of spacecraft. Assessment of individuals regularly working in and exposed continuously for 10 days to magnetic fields less than 100 gammas in intensity indicate that extremely low-intensity magnetic fields encountered during a nominal Apollo moon mission should not affect astronaut health or performance. Careful physiological and psychological observations first on higher primates, then on man exposed to such fields for more prolonged periods of time must be carried out before this conclusion can be drawn for longer exposures.Recent technological advances in propulsion and radiation protection have made it possible that astronauts might also be exposed intermittently to high-intensity, relatively low-gradient magnetic fields during space missions. The duration of such exposures could range from less than an hour if an activated magnetohydrodynamic engine must be serviced, to several days if pure magnetic or plasma-radiation shielding is used for astronaut protection from solar flare radiation. From past experience with personnel who enter high-intensity magnetic fields for brief periods of time in their work, magnetic-field exposures while servicing magnetohydrodynamic engines should not be hazardous to astronauts. On the other hand, past exposures of man and sub-human systems to high-intensity magnetic fields do not indicate whether or not astronauts who are exposed for up to several days to currently estimated magnetic-field intensities associated with pure magnetic or plasma-radiation shielding could suffer impairment of their health or performance. This answer can be obtained only by carefully conducted experiments which closely simulate such exposures, and look closely for physiological, psychological and pathological changes, especially in exposed higher primates, before assessing the response of man to such exposures.Magnetic force is animate or imitates life; and in many things surpasses human life, while this is bound up in the organick body.Prepared under Contract NASr-115 at The Lovelace Foundation for Medical Education and Research, Albuquerque, N.M., U.S.A.  相似文献   
124.
Dried suspensions ofPenicillium roqueforti Thom, Coliphage T-1,Bacillus subtilis and tobacco mosaic virus were exposed to space on board the Gemini-IX-A and XII earth satellites and the Agena-VIII space rocket. All micro-organisms tested survived the direct exposure during the Gemini-IX-A experiment. In the Gemini-XII experiment only the T-1 phage survived the direct exposure. The survival was influenced by the suspending medium and depended on the species of the microorganism. After four months of space flight on the Agena-VIII space rocket surviving fractions between 2×10–3 and 1.0 were found in the unopened flight container. However, micro-organisms exposed on the cover of the container during this period were completely inactivated. Shielding against solar ultraviolet radiation during flight resulted in survival of micro-organisms exceeding to that of the transport controls, and the survival was considered complete.Sterile methylcellulose collection surfaces were exposed to space on board the Gemini-IX-A and XII satellites in an attempt to collect viable micro-organisms in space. None of the collection surfaces yielded viable micro-organisms.  相似文献   
125.
126.
The purpose of this study was to investigate the relationship between serum osmotic changes, water intake and water balance in four, fit young men during and after exercise in the heat, before and after artificial heat acclimatization. During exercise, before steady-state conditions were reached, voluntary water intakes generally paralleled but were not proportional to the serum osmotic pressure. In steady-state conditions, drinking was approximately proportional to the effective osmotic pressure of the serum. During the post-exercise recovery period, when serum osmolarity returned to normal levels, water intake also subsided even though there was a total body water (wt) deficit of about 3%. Body weight did not return to control levels until 62 to 86 hr following the exercise. This slow recovery could not be accounted for by a loss of water associated with glycogen utilization during exercise or by sweat electrolyte depletion. In general, the results supported Dill's hypothesis but plasma volume changes, in addition to osmotic factors,are very likely operative in the initiation and satiation of drinking under these conditions. Perhaps slower acting volume control mechanisms mediate the slow recovery of total body water.
Zusammenfassung Untersucht wurde die Beziehung zwischen osmotischen Veränderungen im Serum, Wasseraufnahme und Wassergleichgewicht bei 4 gesunden,jungen Männern während und nach körperlicher Arbeit in der Hitze vor und nach künstlicher Hitzeakklimatisation. Die freiwillige Wasseraufnahme während der Arbeit, ehe ein steady state erreicht wurde, war im allgemeinen gleichlaufend, aber nicht proportional dem osmotischen Serumdruck. Im steady state war die Trinkmenge ungefähr proportional dem effektiven osmotischen Serumdruck. Wenn die Serumosmolarität während der Erholungsphase zur normalen Werten zurückkehrte, liess die Wasseraufnahme ebenfalls nach,obwohl das Gesamtkörperwasserdefizit ungefähr 3% betrug.Die Körpergewichte erreichten die Ausgangswerte 62–86 Std nach der Arbeit. Diese langsame Erholung war nicht bedingt durch einen Wasserverlust dur Glykogenverwertung während der Arbeit oder durch Elektrolytverluste beim Schwitzen. Die Ergebnisse stützen Dill's Hypothese, doch unter diesen Bedingungen wirken Plasmavolumen-Veränderungen zusätzlich zu osmotischen Faktoren sehr wahrscheinlich mit bei der Auslösung des Trinkens und der Sättiging mit Wasser. Vielleicht vermitteln langsamer wirkende Volumenkontrollmechanismen die langsame Wiederherstellung der Gesamtkörper-Wasservorräte.

Resume On a examiné les relations existant chez 4 jeunes hommes sains entre les variations de la pression osmotiques du sérum d'une part,l'ingestion d'eau et l'équilibre acqueux du corps d'autre part et cela pendant et après un travail corporel à la chaleur tant avant qu'après une acclimatisation artificielle au chaud.L'ingestion volontaire d'eau évolue similairement à la pression osmotique du sérum, mais ne lui est pas proportionnel. Ce phénomène s'observe jusqu'à ce qu'un état dit stationnaire soit atteint. Dès ce moment, les quantités bues sont à peu près proportionnelles à la pression osmotique effective. Pendant la phase de récupération, la pression osmotique redevient normale et l'eau ingérée diminue bien que le déficit en eau pour le corps entier soit encore de 3% environ.Le poids du corps ne retrouve sa valeur initiale que 62 à 86 heures après la période de travail. Ce lent rétablissement n'est pas dû à des pertes d'eau par suite de l'utilisation de glycogènes pendant l'exercice ou par suite de la perte d'électrolytes par la sueur. Ces résultats viennent confirmer les hypothèses de Dill. Pourtant, dans ces conditions, les variations de volume du plasma agissent très vraisemblablement en plus des facteurs osmotiques dans le besoin de boire ou l'état de satiété. Il est possible que des mécanismes de contrôle du volume agissant plus lentement président aux phénomènes de rétablissement des réserves en eau dans son ensemble.


Results were presented in part at the "Symposium on Nutrition and Physical Activity", The Swedish Nutrition Foundation, Tylösand, Sweden, 15–17 August,1966.  相似文献   
127.
128.
129.
130.
The treatment of gas gangrene has been revolutionized by oxygen drenching of tissues infected with Clostridia. This was used in a massive infection of the abdominal wall following a traumatic abortion attempt. The clostridial infection was controlled, but the patient almost succumbed to a secondary infection of gram-negative organisms. This responded to drainage, antibiotics and general supportive measures. In the course of treatment, the value of a team approach to complicated special problems was documented.  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