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   31654篇
  免费   4547篇
  国内免费   912篇
耳鼻咽喉   531篇
儿科学   466篇
妇产科学   215篇
基础医学   6773篇
口腔科学   616篇
临床医学   1852篇
内科学   5342篇
皮肤病学   572篇
神经病学   4953篇
特种医学   303篇
外国民族医学   1篇
外科学   2593篇
综合类   1948篇
现状与发展   2篇
预防医学   964篇
眼科学   277篇
药学   4711篇
  4篇
中国医学   583篇
肿瘤学   4407篇
  2024年   46篇
  2023年   368篇
  2022年   809篇
  2021年   2402篇
  2020年   1378篇
  2019年   1324篇
  2018年   1201篇
  2017年   1412篇
  2016年   1357篇
  2015年   2255篇
  2014年   2092篇
  2013年   1737篇
  2012年   1789篇
  2011年   1841篇
  2010年   1613篇
  2009年   1328篇
  2008年   1542篇
  2007年   981篇
  2006年   923篇
  2005年   956篇
  2004年   850篇
  2003年   846篇
  2002年   679篇
  2001年   647篇
  2000年   510篇
  1999年   550篇
  1998年   671篇
  1997年   618篇
  1996年   472篇
  1995年   415篇
  1994年   383篇
  1993年   413篇
  1992年   279篇
  1991年   246篇
  1990年   217篇
  1989年   169篇
  1988年   185篇
  1987年   191篇
  1986年   266篇
  1985年   229篇
  1984年   188篇
  1983年   169篇
  1982年   152篇
  1981年   149篇
  1980年   101篇
  1979年   58篇
  1978年   31篇
  1977年   23篇
  1976年   17篇
  1975年   15篇
排序方式: 共有10000条查询结果,搜索用时 26 毫秒
81.
目的 :探讨系统性红斑狼疮 (SLE)女性患者血清肿瘤标志物CA12 5 ,CA199含量变化及临床意义。方法 :用化学发光法测定 30例正常女性和 38例SLE女性患者血清中CA12 5 ,CA199含量。结果 :正常组CA12 5含量为 11.14± 6 .4 8U/ml,CA199含量为 3.75± 2 .89U/ml;SLE组CA12 5 ,CA199分别为 2 2 .5 6± 2 0 .4 6U/ml,9.5 7± 9.34U/ml。SLE患者CA12 5 ,CA199阳性率分别为 2 1.1% ,7.89%。结论 :SLE患者血清CAl2 5 ,CA199含量较正常组增高 (P <0 .0 5 )。CA12 5 ,CA199在SLE女性患者中可出现阳性 ,对临床诊断SLE有一定价值。  相似文献   
82.
In the present study, we initially investigated the in vivo (acute and chronic) and in vitro effects of proline on cytochrome c oxidase (complex IV) activity in rat cerebral cortex to test the hypothesis that proline might alter energy metabolism and that this alteration could be provoked by oxidative stress. The action of alpha-tocopherol and ascorbic acid on the effects produced by proline was also evaluated. For acute administration, 29- and 60-day-old rats received one subcutaneous injection of proline (18.2 micromol/g body weight) or an equivalent volume of 0.9% saline solution (control) and were sacrificed 1h later. For chronic treatment, proline was injected subcutaneously twice a day at 10h intervals from the 6(th) to the 28(th) day of age. Rats were sacrificed 12h (29(th)) or 31 days (60(th)) after the last injection. Results showed that acute administration of proline significantly diminished the activity of cytochrome c oxidase in the cerebral cortex of 29- and 60-day-old rats. On the other hand, chronic hyperprolinemia reduced this complex activity only on day 29, but not on the 60(th) day of life. In another set of experiments, 22-day-old rats or 53-day-old rats were pretreated for 1 week with daily intraperitoneal administration of alpha-tocopherol (40 mg/kg) and ascorbic acid (100mg/kg) or saline. Twelve hours after the last antioxidant injection, rats received a single injection of proline or saline and were killed 1h later. In parallel to chronic treatment, rats received a daily intraperitoneal injection of alpha-tocopherol and ascorbic acid from the 6(th) to the 28(th) day of life and were killed 12h after the last injection. Results showed that the pretreatment with alpha-tocopherol and ascorbic acid before acute proline administration or concomitant to chronic proline administration significantly prevented these effects. We also observed that proline (3.0 microM-1.0 mM) when added to the incubation medium (in vitro studies) did not alter cytochrome c oxidase activity. Data suggest that the inhibitory effect of proline on cytochrome c oxidase activity is possibly associated with oxidative stress and that this parameter may be involved in the brain dysfunction observed in hyperprolinemia.  相似文献   
83.
It has been suggested that reward dependence, as measured by the Tridimensional Personality Questionnaire (TPQ), is related to central noradrenergic activity, a proposition supported by two studies of urinary norepinephrine metabolite. In the current investigation, 190 normal young Han Chinese were examined, with genetic polymorphisms determined for the norepinephrine transporter (1287G/A) and the α2c‐adrenoceptor (Del322–325) to test the association with TPQ personality traits. No significant association was demonstrated for these two polymorphisms and any of the TPQ personality‐factor scores, including reward dependence and its subscales. Our negative findings suggest that the investigated polymorphisms of the norepinephrine transporter and the α2c adrenoceptor do not play a major role in the reward‐dependence personality trait as assessed by TPQ. © 2002 Wiley‐Liss, Inc.  相似文献   
84.
BACKGROUND: Patients with renal failure have an increased susceptibility to infections. We therefore studied the recruitment of monocytes and their expression of adhesion molecules CD11b and CD62L at the site of interstitial inflammation in patients with renal failure. Furthermore, we studied if the capacity of monocytes to up-regulate CD11b in interstitial inflammation was determined by the interstitial concentration of chemotactic factors. METHODS: Three intensities of interstitial inflammation (0, intermediate and intense) were established in skin blister chambers. Leukocyte count, CD11b/CD62L expression, monocyte chemotactic protein-1 (MCP-1) and blister activity in terms of CD11b mobilization were determined. RESULTS: The CD62L expression on monocytes was lower in the peripheral circulation in patients with renal failure compared with healthy subjects (P<0.005 and P<0.001). At the site of interstitial inflammation patients had a higher expression of CD62L (intermediate, P<0.05; intense, P<0.005). Furthermore, monocytes from patients had an impaired capacity to mobilize CD11b both in the peripheral circulation (P<0.005) and at the intermediate and intense sites of interstitial inflammation (P<0.005 and P<0.001, respectively) compared with cells collected from healthy subjects. We incubated monocytes in blister exudates, in order to explore whether this phenomenon is caused by cellular factors and/or to the interstitial concentration of chemotactic mediators. The expression of CD11b on monocytes from healthy blood donors incubated in blister exudates from either patients or healthy subjects in vitro was similar. The interstitial concentration of MCP-1 at the site of intermediate inflammation was significantly lower in patients with renal failure compared with the corresponding blister exudate collected from healthy subjects (P<0.05), but no differences were observed at the site of intense inflammation. Furthermore, neutralizing the action of MCP-1 in blister exudates with monoclonal antibodies did not have any impact on monocyte CD11b expression following incubation in blister exudates. CONCLUSION: These studies indicate that the impaired capacity of monocytes to mobilize CD11b at the site of inflammation in patients with renal failure is more dependent on constitutive cellular factors than the concentration of CD11b mobilizing factors in the interstitium.  相似文献   
85.
We attempted to find out the role of α2-adrenoceptors of the medullary lateral reticular nucleus (LRN) in antinociception in rats. Spinal antinociception was evaluated using the tail-flick test, and supraspinal antinociception using the hotplate test. Antinociceptive effects were determined following local electric stimulation of the LRN, and following microinjections of medetomidine (an α2-adrenoceptor agonist; 1–10 μg), atipamezole (an α2-adrenoceptor antagonist; 20 μg) or lidocaine (4%) into the LRN. The experiments were performed using intact and spinalized Hannover-Wistar rats with a unilateral chronic guide cannula. Electric stimulation of the LRN as well as of the periaqueductal gray produced a significant spinal antinociceptive effect in intact rats. Medetomidine (1–10 μg), when microinjected into the LRN, produced no significant antinociceptive effect in the tail-flick test in intact rats. However, following spinalization, medetomidine in the LRN (10 μg) produced a significant atipamezole-reversible antinociceptive effect in the tail-flick test in the hot-plate test, medetomidine (10 μg) in the LRN produced a significant atipamezole-reversible increase of the paw-lick latency in intact rats. Microinjection of atipamezole (20 μg) or lidocaine alone into the LRN produced no significant effects in the tail-flick test. The results are in line with the previous evidence indicating brat the LRN and the adjacent ventrolateral medulla is involved in descending inhibition of spinal nocifensive responses. However, α2-adrenoceptors in the LRN do not mediate spinal antinociception but, on the contrary, their activation counteracts antinociception at the spinal cord level. The spinal aninociceptive effect of supraspinally administered medetomidine in spinalized rats can be explained by a spread of the drug (e.g., via circulation) which then directly activates α2-adrenoceptors at the spinal cord level.  相似文献   
86.
本文用C(3b)受体花环试验及IC花环试验分别测定了50例正常人及50例癫痫患者的红细胞C(3b)受体花环率及IC花环率。结果提示癫痫患者C(3b)受体花环率(8.46±3.98%)明显低于正常对照组(13.92±4.32%)(P<0.001),IC花环率(5.22±2.59%)稍低于正常对照组(5.90±1.67%)(P<0.05)。表明癫痫患者的红细胞免疫粘附功能是低下的。文章还对影响正常人及癫痫患者红细胞免疫粘附功能的因素进行了讨论。  相似文献   
87.
循环系统里的成熟红细胞在其生命过程里经历着氧化性衰老,相应细胞组份出现血红蛋白变性、膜蛋白交联、带3蛋白聚集以及带3蛋白降解等多种修饰。这些修饰作为红细胞膜上的衰老信号参与构成衰老细胞抗原,由此启动与IgG自身抗体(主要为带3蛋白抗体)的结合以及补体的沉淀,最终是免疫吞噬系统对异常细胞的识别清除.现就衰老红细胞与带3蛋白的关系作一综述。  相似文献   
88.
The CD16: ζ: γ receptor complex allows natural killer (NK) cells to recognize and eliminate antibody-coated target cells. Whereas the ectodomain of CD16 is the receptor for Fcγ domains of immunoglobulins, disulfide-linked homo- and heterodimers composed of ζ and γ are required for the cell surface expression, and signal transduction properties of the complex. Engagement of CD16 activates the tyrosine kinase pathway, which induces the tyrosine phosphorylation of several substrates, including the ζ subunit and the phospholipase C γ-1 and γ-2 isoforms. Here we show that CD 16 stimulation of either peripheral blood NK cells, leukemic NK cells, or Jurkat transformants expressing a CD16:ζ:γ receptor complex, results in the tyrosine phosphorylation of a 70 kDa ζ-associated protein (pp70). Similarly, a 70-kDa ζ-associated phosphoprotein in T cells has been shown to be a tyrosine kinase (ZAP-70). Peptide mapping analysis indicates that the 70-kDa ζ-associated phosphoproteins from T cells and NK cells are structurally indistinguishable. We conclude that the CD16:ζ:γ complex may use a ZAP-70-related non-receptor tyrosine kinase, in the CD16 signaling cascade leading to NK cell activation.  相似文献   
89.
The inhibition of [35S]t-butylbicyclophosphorothionate ([35S]TBPS) binding to the GABAA receptor by the insecticide γ-hexachlorocyclohexane, lindane, was studied in several brain regions and using different membrane preparation methods, both in vitro and after dosing the animals with the chemical. In the latter studies, the amount of lindane remaining in the membrane suspensions used for binding assays was determined. In vitro data showed values of IC50 from 150 to 1675 nM, varying in function of the membrane preparation method used. This may account for the discrepancies in IC50 values found in the literature. IC50 values within the range of 150–250 nM were determined using extensively washed membranes from several brain regions, so no evidence arose for brain regional differences in the affinity of lindane for the TBPS binding site. After different schedules of acute treatment with lindane, we found a manifest relationship between the extent of the observable inhibition of [35S]TBPS binding and the lindane amount remaining in the membrane suspensions used for binding assays. This relationship was in good agreement with the in vitro data, so no support for an in vivo acute regulation of the binding site was obtained.  相似文献   
90.
Molecular genetic analysis was performed in a patient with cytochrome b positive X-linked chronic granulomatous disease. A previous Southern blot study, using a cytochrome b heavy chain cDNA as probe, revealed a Pst I restriction fragment pattern for the cytochrome b heavy chain gene (CYBB) different to that of normal individuals. Since restriction length polymorphism with Pst I has never been observed in control individuals and no abnormal restriction fragment patterns in the patient's CYBB was detected with seven other enzymes used, we focussed on the single Pst I site in the CYBB cDNA as being the only mutation site responsible for his disease. A fragment of the patient's cDNA which included the Pst I site was amplified by reverse polymerase chain reaction, and loss of the Pst I site in the fragment was confirmed by incubation with Pst I. Subsequent sequence analysis of the fragment revealed a point mutation in the Pst I site (cytosine to adenine), substituting glutamic acid for alanine at position 57.  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