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   20500篇
  免费   1742篇
  国内免费   57篇
  2021年   228篇
  2020年   142篇
  2019年   199篇
  2018年   243篇
  2017年   200篇
  2016年   341篇
  2015年   624篇
  2014年   674篇
  2013年   1035篇
  2012年   1134篇
  2011年   1169篇
  2010年   717篇
  2009年   681篇
  2008年   1069篇
  2007年   1105篇
  2006年   1015篇
  2005年   1016篇
  2004年   949篇
  2003年   935篇
  2002年   908篇
  2001年   224篇
  2000年   183篇
  1999年   262篇
  1998年   265篇
  1997年   193篇
  1996年   190篇
  1995年   179篇
  1994年   197篇
  1993年   165篇
  1992年   179篇
  1991年   168篇
  1990年   144篇
  1989年   156篇
  1988年   172篇
  1987年   157篇
  1986年   147篇
  1985年   183篇
  1984年   199篇
  1983年   189篇
  1982年   205篇
  1981年   239篇
  1980年   206篇
  1979年   163篇
  1978年   191篇
  1977年   169篇
  1976年   141篇
  1975年   146篇
  1974年   161篇
  1973年   161篇
  1968年   112篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Onosma echioides Linn (Boraginaceae) is the most frequently used curative herb widely used for kidney obstruction, sciatic pain, and gout. The present study was designed to investigate the therapeutic effects of n-hexane bark extract of O. echioides (OE) L. root in vivo against Streptozotocin-induced diabetic neuropathy in SD rats. For in vivo activity, the experiment was categorized into five different groups (n = 5). Group-I was considered as nondiabetic/normal control (NC) treated with 0.5% carboxymethyl cellulose (CMC), Group II as diabetic control, Group-III, IV, and V served as diabetic treated with OE 50, OE 100, and pregabalin at a dose of 50, 100, and 10 mg/kg body weight, orally, respectively. Body weight, blood glucose, oral glucose tolerance test, behavioral studies (motor coordination test, thermal hyperalgesia, cold allodynia, locomotor activity, oxidative biomarkers (thio barbituric acid reactive substances [TBARS], superoxide dismutase [SOD], glutathione [GSH], and catalase), and histopathology of the sciatic nerve were performed. Treatment with OE showed a dose-dependent increase in neuroprotective activity by improving the myelination and decreasing the axonal swelling of nerve fibers. The verdicts of behavioral activities showed a remarkable effect on animals after the treatment of extract and standard drug pregabalin. In conclusion, our findings supported the traditional application of OE and explored its importance in the management of diabetic neuropathy. Additional clinical experiments may provide novel therapeutic drugs for diabetes and its complications.  相似文献   
63.
A method for the immobilization of lipoxygenase (LOX) in an alginate-silicate gel matrix was developed. In this method, a mixture of calcium alginate beads and LOX in borate buffer are dispersed into a hexane solution of tetramethoxy-ortho-silicate (TMOS). Hydrolysis of the TMOS gives products that permeate and co-polymerize with the alginate gel to form a colloid within the beads that entraps the LOX. Optimum reaction conditions for sol-gel entrapment of LOX are at pH 9.0 in 0.2M borate buffer. The composite gel, after isolation and vacuum drying, had excellent protein retention that has good enzyme activity and stability at room temperature. The activity of the entrapped LOX was less than the activity of the free enzyme. However, the activity of the immobilized LOX can be restored by the addition of borate buffer and glycerol, or borate buffer saturated with an organic solvent. In contrast to the free enzyme in solution, which loses its activity in less than one day, sol-gel entrapped LOX retains its activity at ambient temperature for at least 25 days and can be recycled. This report demonstrates that the sol-gel entrapment method for immobilizing LOX can be useful in developing a process for the oxidation of polyunsaturated fatty acids.  相似文献   
64.
65.
66.
67.
Egg shell membrane protein contains significant quantities of the lysine-derived aldehyde, allysine, and its aldol condensation product. NaB3H4 reduction followed by alkaline hydrolysis of purified protein revealed that there were six residues/1000 of both allysine and the reduced aldol while only traces of desmosine and isodesmosine were detected. The amino acid composition of the membrane protein did not resemble that of mammalian elastin.  相似文献   
68.
The integument of the paddlefish (Polyodon spathula) is unusual as a relatively small amount of mucus is produced by epithelial cells that are not modified into regular mucous gland cells. A thick compact epidermis and dermis compensate for the slight amount of mucus secreted. Paddlefish have a variety of scales formed of concentric bony lamellae containing osteocytes. There are five kinds of scales: dorsal and ventral fulcra on the caudal fin, rhomboidal scales on the caudal lobe, horny denticles over the pectoral girdle, calcareous denticles on the trunk, and anchor-shaped plates on the rostrum. Except for the fulcra, the scales are undoubtedly vestigial. The numerous surface pits on the rostrum, head, operculum, and throat are epithelial invaginations which are not connected to lateral line canals. No nerves lead to the pits. The spherical to cuboidal and often ciliated cells at the base of the pits are considered to be aplasic cells of unformed neuromasts.  相似文献   
69.
70.
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