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   331176篇
  免费   15370篇
  国内免费   861篇
  2021年   1786篇
  2018年   15822篇
  2017年   14722篇
  2016年   11766篇
  2015年   3850篇
  2014年   4734篇
  2013年   6632篇
  2012年   12184篇
  2011年   22291篇
  2010年   18934篇
  2009年   14438篇
  2008年   18472篇
  2007年   20842篇
  2006年   7502篇
  2005年   7702篇
  2004年   8114篇
  2003年   8115篇
  2002年   7817篇
  2001年   9627篇
  2000年   9280篇
  1999年   7041篇
  1998年   2142篇
  1997年   1978篇
  1996年   1853篇
  1992年   5515篇
  1991年   5763篇
  1990年   5672篇
  1989年   5653篇
  1988年   5249篇
  1987年   4913篇
  1986年   4461篇
  1985年   4698篇
  1984年   3743篇
  1983年   3071篇
  1982年   2041篇
  1981年   1742篇
  1980年   1736篇
  1979年   3360篇
  1978年   2597篇
  1977年   2406篇
  1976年   2345篇
  1975年   2855篇
  1974年   3140篇
  1973年   3101篇
  1972年   3440篇
  1971年   3252篇
  1970年   2230篇
  1969年   2168篇
  1968年   2037篇
  1967年   1800篇
排序方式: 共有10000条查询结果,搜索用时 678 毫秒
951.
Eriocaulon raipurense (Eriocaulaceae) is described and illustrated as a new species from Madhya Pradesh, India. The species is closely allied to E. hamiltonianum but differs in the size and apex of involucral bancts, white-pilose nature of floral bracts and colour of female petals.  相似文献   
952.
953.
954.
Shallow-water vegetated estuarine habitats, notably seagrass, mangrove and saltmarsh, are known to be important habitats for many species of small or juvenile fish in temperate Australia. However, the movement of fish between these habitats is poorly understood, and yet critical to the management of the estuarine fisheries resource. We installed a series of buoyant pop nets in adjacent stands of seagrass, mangrove and saltmarsh in order to determine how relative abundance of fishes varied through lunar cycles. Nets were released in all habitats at the peak of the monthly spring tide for 12 months, and in the seagrass habitat at the peak of the neap tide also. The assemblage of fish in each habitat differed during the spring tides. The seagrass assemblage differed between spring and neap tide, with the neap tide assemblage showing greater abundances of fish, particularly those species which visited the adjacent habitats when inundated during spring tides. The result supports the hypothesis that fish move from the seagrass to the adjacent mangrove and saltmarsh during spring tides, taking advantage of high abundances of zooplankton, and use seagrass as a refuge during lower tides. The restoration and preservation of mangrove and saltmarsh utility as fish habitat may in some situations be linked to the proximity of available seagrass.  相似文献   
955.
Vesiculated fragments of chicken skeletal muscle transverse tubule (TT) membranes were analyzed for their content of loosely associated and integral membrane proteins. Of particular interest was the identification of the magnesium-stimulated ATPase (Mg-ATPase), which is characteristically located in native isolated TT vesicles of chicken skeletal muscle [R. A. Sabbadini and V. R. Okamoto (1983) Arch. Biochem. Biophys. 223, 107-119]. A number of the proteins found in vesicular TT preparations were found to be extractable by a mild Triton-X100 treatment and were identified as aldolase, enolase, creatine kinase, glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase, and pyruvate kinase. Approximately 60% of TT-associated protein was extracted with Triton, resulting in a twofold enrichment of the Mg-ATPase. Concommitantly, one core integral membrane protein possessing a Mr of 102,000 was enriched, suggesting that it is responsible for the Mg-ATPase activity present in chicken skeletal muscle TT membranes.  相似文献   
956.
957.
Histological and electron microscopy findings suggesting the effect of monochromatic coherent polarized red light on zymosan arthritis in rats are presented. The data obtained have confirmed that treatment of inflamed joints with laser rays exerts an evident therapeutic effect which is determined by activated function of macrophages and fibroblasts of the synovial membrane, resulting in a more rapid change of inflammation phases. Analysis of the cases where the rats were treated with ordinary red light has revealed no essential differences in the joints of the control and irradiated groups.  相似文献   
958.
Activity of phosphodiesterases disintegrating cAMP and cGMP in the cornea, sclera and ciliary body was investigated in health and in different stages of experimental herpetic keratitis. The problems concerning the role of the cyclase system in the pathogenesis of herpetic keratitis and the possibility of applying some of the drugs to the disease treatment are discussed.  相似文献   
959.
The proteins of submitochondrial particles solubilized with 0.1% Triton X-100 were separated by polyacrylamide gel electrophoresis. Hydrolysis of several proteinase substrates was registered directly in the gel after completion of electrophoresis. According to the data obtained the inner mitochondrial membrane contains one or two enzymes which catalyze hydrolysis of cytochrome c as well as one or two enzymes splitting synthetic substrate of trypsin-like proteinases, e. g. N-alpha-benzoyl-L-arginine-p-nitroanilide (BAPA) and N-alpha-benzoyl-L-arginine-beta-naphthylamide (BANA). Submitochondrial particles were shown to catalyze hydrolysis of 3H-labelled cytochrome c. This activity is suppressed by the same inhibitors as the hydrolysis of mitochondrial translation products, i. e. phenyl-methylsulfonylfluoride, p-chloromercuribenzosulfonate, leupeptin and antipain. Presumably these two processes are catalyzed by the same enzyme localized in the inner mitochondrial membrane. Physiological functions of BAPA- and BANA-hydrolyzing enzyme(s) are still unclear.  相似文献   
960.
The lipid dependence of pyrophosphatase activity was studied by treatment of liver and hepatoma microsomes with phospholipase C from Cl. perfringens and B. cereus and a subsequent incorporation of various classes of phospholipids into the delipidated microsomes. Phospholipase C hydrolysis sharply lowers the pyrophosphatase activity of liver and hepatoma microsomes. The enzyme activity is restored after introduction of phospholipids into delipidated liver microsomes, the maximal effect being achieved on incorporation of phosphatidylcholine. All the phospholipids tested exerted the same reactivation effects on the delipidated microsomes of hepatoma. However, a more complete delipidation of hepatoma microsomes by phospholipase C hydrolysis and a subsequent organic solvent extraction revealed a specific dependence of the enzyme activity on phosphatidylserine.  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