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   31305篇
  免费   82篇
  国内免费   123篇
系统科学   304篇
丛书文集   563篇
教育与普及   99篇
理论与方法论   97篇
现状及发展   14629篇
研究方法   1141篇
综合类   14378篇
自然研究   299篇
  2012年   356篇
  2011年   684篇
  2009年   180篇
  2008年   494篇
  2007年   564篇
  2006年   494篇
  2005年   531篇
  2004年   549篇
  2003年   560篇
  2002年   495篇
  2001年   917篇
  2000年   960篇
  1999年   578篇
  1994年   363篇
  1992年   537篇
  1991年   431篇
  1990年   513篇
  1989年   480篇
  1988年   478篇
  1987年   496篇
  1986年   520篇
  1985年   621篇
  1984年   430篇
  1983年   431篇
  1982年   381篇
  1981年   411篇
  1980年   467篇
  1979年   986篇
  1978年   820篇
  1977年   791篇
  1976年   616篇
  1975年   701篇
  1974年   967篇
  1973年   834篇
  1972年   794篇
  1971年   1022篇
  1970年   1186篇
  1969年   1031篇
  1968年   946篇
  1967年   912篇
  1966年   787篇
  1965年   595篇
  1964年   211篇
  1959年   339篇
  1958年   572篇
  1957年   418篇
  1956年   347篇
  1955年   347篇
  1954年   334篇
  1948年   234篇
排序方式: 共有10000条查询结果,搜索用时 281 毫秒
1.
2.
If the general arguments concerning theinvolvement of variation and selection inexplanations of ``fit'' are valid, then variationand selection explanations should beappropriate, or at least potentiallyappropriate, outside the paradigm historisticdomains of biology and knowledge. In thisdiscussion, I wish to indicate some potentialroles for variation and selection infoundational physics – specifically inquantum field theory. I will not be attemptingany full coherent ontology for quantum fieldtheory – none currently exists, and none islikely for at least the short term future. Instead, I wish to engage in some partiallyspeculative interpretations of some interestingresults in this area with the aim ofdemonstrating that variation and selectionnotions might play a role even here. Ifvariation and selection can survive in even asinhospitable and non-paradigmatic a terrain asfoundational physics, then it can surviveanywhere.  相似文献   
3.
The shrink proofing on wool with treatment of protease named Argaenzyme STL was studied. The various pretreating auxiliaries, different parameters for protease treating process and the effect of stabilizer were discussed in detail. The varieties of some properties before and after protease treatment were also investigated.  相似文献   
4.
B S Qiu  C H Cho  C W Ogle 《Experientia》1992,48(4):389-391
Ten-day treatment with nicotine (5, 25 or 50 micrograms/ml drinking water) dose-dependently intensified gastric ulceration induced by cold-restraint, and emptying rate. Stomach contractions produced by graded doses of bethanechol i.v. were elevated further by nicotine treatment. It is suggested that chronic nicotine administration produces hypersensitivity of the gastric muscarinic receptors; stomach hypermotility contributes to the ulcer-worsening action of the alkaloid.  相似文献   
5.
Photon emission of phagocytes in relation to stress and disease.   总被引:1,自引:0,他引:1  
E M Lilius  P Marnila 《Experientia》1992,48(11-12):1082-1091
Phagocytes, the first-line cells of the body's defence mechanisms against invading pathogens, kill microorganisms by means of lysosomal degradative enzymes and highly toxic reactive oxygen intermediates. The reactive oxygen compounds are produced, in a process called the 'respiratory burst', by the NADPH oxidase complex in plasma membranes, and by myeloperoxidase in phagolysosomes after degranulation. These processes generate electronically excited states which, on relaxation, emit photons, giving rise to phagocyte chemiluminescence (CL). This paper describes the conditions for the measurement of CL, and reviews the activity of phagocytes from individuals undergoing stress or disease. The capability of phagocytes to emit photons reflects remarkably well the pathophysiological state of the host. In many cases even the magnitude of the stress, the presence of a pathogen in the body, or the activity of the disease can be estimated. Physiological changes, e.g. in the reproductive cycle, can also be predicted.  相似文献   
6.
7.
8.
9.
Summary The authors show the antibiotic activity of water-insoluble salts of hydrosoluble antibiotics in the case of penicillin G (salts of iron, copper, silver, gold, and uranium) and streptomycin (oleate).  相似文献   
10.
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