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   20384篇
  免费   1893篇
  国内免费   12篇
  2023年   102篇
  2022年   264篇
  2021年   564篇
  2020年   266篇
  2019年   388篇
  2018年   438篇
  2017年   340篇
  2016年   589篇
  2015年   985篇
  2014年   1022篇
  2013年   1403篇
  2012年   1600篇
  2011年   1565篇
  2010年   967篇
  2009年   844篇
  2008年   1214篇
  2007年   1194篇
  2006年   1074篇
  2005年   1017篇
  2004年   919篇
  2003年   854篇
  2002年   827篇
  2001年   199篇
  2000年   155篇
  1999年   178篇
  1998年   168篇
  1997年   140篇
  1996年   117篇
  1995年   110篇
  1994年   116篇
  1993年   112篇
  1992年   119篇
  1991年   109篇
  1990年   97篇
  1989年   86篇
  1988年   93篇
  1987年   72篇
  1986年   66篇
  1985年   90篇
  1984年   96篇
  1983年   63篇
  1982年   82篇
  1981年   74篇
  1980年   68篇
  1979年   78篇
  1978年   55篇
  1977年   61篇
  1976年   65篇
  1975年   70篇
  1973年   55篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
151.
The concentration of lysophosphatidylcholine (monoacyl sn-glycerol 3-phosphorylcholine) in intima plus inner media of atherosclerotic aorta from squirrel monkeys was nearly eight times that in comparable control tissue. Plasma levels of the same compound were somewhat elevated in the atherosclerotic group. The metabolism of fatty acyl CoA's and lysophosphatides was studied in cell-free preparations of intima plus inner media from squirrel monkey aorta. Linoleic acid was incorporated predominantly into phosphatidylcholine (as opposed to other phospholipids) when linoleoyl-1-(14)C CoA was the substrate. The extent of this reaction was dependent on the concentration of lysophosphatidylcholine. Lysophosphatidylethanolamine (monoacyl sn-glycerol 3-phosphorylethanolamine) stimulated the incorporation of linoleate into phosphatidylethanolamine. 1-Palmitoyl-1'-(14)C sn-glycerol 3-phosphorylcholine ((14)C-lysophosphatidylcholine) was incorporated into phosphatidylcholine only in the presence of acyl CoA's or ATP plus CoA. Incorporation of (14)C with (14)C-lysophosphatidylcholine plus linoleoyl CoA equaled that with linoleoyl-1-(14)C CoA and lysophosphatidylcholine. Various other lines of evidence are presented to support the importance of the fatty acyl CoA:lysophosphatide fatty acyl transferase mechanism in aortic phospholipid metabolism. Cell-free preparations of aortic intima plus inner media from squirrel monkeys with early, nutritionally-induced atherosclerosis utilized linoleoyl-1-(14)C CoA more than preparations from control monkeys when incubations were carried out without added lysophosphatidylcholine and for long periods (30 min). With optimum levels of labeled linoleoyl CoA and unlabeled lysophosphatidylcholine, or unlabeled linoleoyl CoA and labeled lysophosphatidylcholine, there were no differences in substrate utilization between control and atherosclerotic tissues. We conclude that the concentrations of lysophosphatidylcholine, which are higher in atherosclerotic than in control aortic tissues, could be a factor controlling rates of fatty acid incorporation into phosphatidylcholine.  相似文献   
152.
Differences in the metabolic fate of antithyroid drugs influence the optimal frequency of administration and their therapeutic efficacy. 35S propylthiouracil differed from the 35S imidazoles (carbimazole and methimazole) in the more rapid absorption and excretion and the shorter biological half-life in the plasma of the former. Renal function may have a more important influence on the biological half-life of the drugs than thyroid status. Further work is required to determine the optimal frequency of administration for each compound.  相似文献   
153.
Cell Walls and Lysis of Mortierella parvispora Hyphae   总被引:1,自引:0,他引:1       下载免费PDF全文
Walls of Mortierella parvispora, Pullularia pullulans, Absidia repens, Fusarium oxysporum, and of several Penicillium species varied in their susceptibilities to digestion by glucanase and chitinase. Polysaccharides were present in the residues remaining after enzymatic digestion. Acid hydrolysates of the walls contained glucose, glucosamine, and a small amount of galactose. The walls of M. parvispora, which also contained fucose, were the least digested by these two enzymes. Much of the M. parvispora wall material was resistant to decomposition by a heterogeneous soil community, and viable hyphae were not lysed by a glucanase-chitinase mixture. Walls of this fungus were fractionated, and the chemical composition of the fractions was determined. The chitin which was abundant in one of the fractions was apparently largely shielded from chitinase hydrolysis by a glucan. The ecological significance of these findings is discussed.  相似文献   
154.
Incomplete phagelike particles were found in competent and incompetent cells of Haemophilus influenzae Rd (transformable) lysed after exposure to ultraviolet radiation.  相似文献   
155.
Zusammenfassung Es wurde fürRubus Gremlii die Chromosomenzahl 2n=28, fürRubus candicans 2n=21 festgestellt. Die Angabe vonMarks fürRubus candicans 2n=35 bezieht sich vielleicht aufRubus Linkianus, der wahrscheinlich mitRubus candicans nicht näher verwandt ist.  相似文献   
156.
Ninety patients who had a recurrence of thyrotoxicosis after thyroidectomy have been reviewed. All 10 patients who had a second operation and 18 out of 20 patients treated with a full course of antithyroid drugs relapsed. These results differ greatly from the results of treatment of the first episode of thyrotoxicosis, whether by thyroidectomy or antithyroid drugs. Radioiodine is the treatment of choice in this group of patients, despite the high incidence of hypothyroidism.  相似文献   
157.
158.
159.
160.
It has been well established that “normal” pregnancy gives rise to much anxiety whose source is variable. When not adequately dealt with, the anxiety may masquerade in the guise of physical symptoms such as fatigue, dizziness, nausea and vomiting, or, more often, as disquieting emotional counterparts, like irritability and depression.A study was undertaken in the outpatient obstetrical department at U.C.L.A. utilizing a group psychotherapeutic approach. The results helped the patients and offered training to staff in dealing with emotional problems of pregnancy. Patients were seen in groups of seven, twice a month for one-hour sessions. Participating in each group were an obstetrical resident, a psychiatric resident and a nurse. The subject material was not selected beforehand. Groups were similar in that the expected time of delivery of the patients was approximately the same. Results of the study suggested that the much needed emotional support may be supplied in this way with little to no additional time expenditure on the part of the physician or nurse.  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