全文获取类型
收费全文 | 4277篇 |
免费 | 128篇 |
国内免费 | 26篇 |
出版年
2023年 | 8篇 |
2022年 | 7篇 |
2021年 | 66篇 |
2020年 | 17篇 |
2019年 | 9篇 |
2018年 | 26篇 |
2017年 | 25篇 |
2016年 | 300篇 |
2015年 | 1070篇 |
2014年 | 1369篇 |
2013年 | 147篇 |
2012年 | 225篇 |
2011年 | 167篇 |
2010年 | 102篇 |
2009年 | 67篇 |
2008年 | 89篇 |
2007年 | 64篇 |
2006年 | 52篇 |
2005年 | 85篇 |
2004年 | 89篇 |
2003年 | 54篇 |
2002年 | 53篇 |
2001年 | 49篇 |
2000年 | 28篇 |
1999年 | 20篇 |
1998年 | 16篇 |
1997年 | 13篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 21篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 17篇 |
1988年 | 9篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 4篇 |
1978年 | 4篇 |
1973年 | 4篇 |
1971年 | 4篇 |
1966年 | 3篇 |
1959年 | 3篇 |
1958年 | 3篇 |
1957年 | 7篇 |
1955年 | 3篇 |
1943年 | 3篇 |
排序方式: 共有4431条查询结果,搜索用时 15 毫秒
41.
自发性高血压大鼠血管α1肾上腺素受体亚型的改变 总被引:1,自引:0,他引:1
本工作在离体与整体条件下比较易卒中型自发性高血压(SHRSP)大鼠与WKY大鼠血管中α_1受体的两种亚型。在离体灌流的主动脉、肾动脉与肠系膜动脉,50μmol/L氯甲基可乐定(CEC)预温育30min可使α_1受体激动时引起的最大收缩张力在SHRSP与WKY大鼠分别降为对照时的31.4±8.3%与35.2±2.9%,68.4±8.2%与80.1±7.3%,68.4±6.3%与55.4±7.0%,两者间均无显著性差别。但10μmol/L硝苯吡啶对α_1受体收缩效应的阻断作用则在SHRSP大鼠大大超过WKY大鼠,最大收缩张力分别降为对照时的3.1±1.5%与56.5±4.8%(P<0.01),9.0±4.1%与23.6±3.5%(P<0.05),5.9±2.5%与28.0±0.8%(P<0.01)。整体动物实验也显示硝苯吡啶的降血压作用及对苯肾上腺素升血压效应的阻断作用在SHRSP大鼠都较WKY大鼠显著增强。离体主动脉a_1受体激动时的快速相与持续相收缩均主要由α_(1B)亚型激动引起,硝苯吡啶对快速相收缩的阻断作用在SHRSP与WKY大鼠无显著性差别,但对持续相收缩的阻断作用则在SHRSP大鼠显著强于WKY大鼠。上述结果提示SHRSP大鼠血管α_1受体两种亚型的分布没有显著改变,但α_(1B)受体激动时继发性细胞外Ca~(2+)进入的途径由非双氢吡啶敏感性钙通道转变为双氢吡啶敏感性钙通道。 相似文献
42.
43.
双波长分光光度法测定肝素钠效价 总被引:5,自引:0,他引:5
本文介绍了在室温条件下,以天青作显色剂,用双波长分光光度法测定肝素钠的效价。本法快速准确,测定浓度0—20u/ml,相对误差在±4%以内,标准偏差0.19,变异系数2.5‰,与羊血浆法测定结果相差±4u/ml以内。 相似文献
44.
Summary A prospective randomized trial compared the administration of intrapleural plus intravenous Corynebacterium parvum (C. parvum) versus placebo in patients with resected Stage I and Stage II non-small cell bronchogenic carcinoma. Treatment consisted of 7 mg C. parvum injected into the pleural space and 7 mg C. parvum intravenously once between days 6 and 12 postoperatively and 7 mg intravenously every 3rd month during the 1st year. Intrapleural administration of 35 cc of saline served as the placebo and the flush after intrapleural C. parvum.Of the 303 patients entered into this study, 286 were evaluable, with an average follow-up time of 3.5 years. More complications, especially fever, were observed in patients receiving C. parvum. A fever greater than 38 °C was observed in 9% of the patients assigned to placebo and 76% of the patients assigned to C. parvum. There was no significant difference between the treatments with respect to disease-free interval or survival.M. Kaufmann, J. Stjernswärd**, A. Zimmermann (Ludwig Institute for Cancer Research, Bern Branch); K. Stanley**, M. Isley, M. Zelen (Frontier Science & Tech. Research Foundation, Brookline, MA, USA); C. Mouritzen, P. Paulsen, U. Henriques (Dept. of Thoracic and Cardiovascular Surgery and Institute of Pathology, Kommunehospital, Aarhus, Denmark); N. Konietzko, W. Maassen, W. Hartung, W. Wierich (Ruhrland Clinic, Essen-Heidhausen, and Pathology Institute, Ruhr-University, Bochum, FRG); P. Oehl (Innere Klinik und Poliklinik Tumorforschung, Essen, FRG); J. Vogt-Moykopf, H. Toomes, W. Hofmann (Rohrbach Hospital, Clinic for Thoracic Medicine and Pathology Institute, Heidelberg, FRG); F. Krause, R. Rios, R. Spanel (Klinik Löwenstein, Löwenstein, and Pathology Institute, Ulm, FRG); J. Orel, B. Hrabar, D. Ferluga, T. Rott (University Medical Center, Thoracic Surgery and Pathology, Ljubljana, Yugoslavia); H. A. Rostad, J. R. Vale, P. Lexow (Rikshospital, Oslo, Norway); S. Hagen, S. Birkeland (Ulleval Hospital, Oslo, Norway); T. Harbitz, R. Nissen-Meyer (Aker Hospital, Oslo, Norway); E. Aspevik, H. Engedal, A. Mykin (Haukeland Hospital, Bergen, Norway); V. O. Björk, L. Rodriguez, K. Böök, J. Willems (Karolinska Sjukhuset, Thoracic Surgical Clinic and Pathology Department, Stockholm, Sweden); E. Grädel, J. Hasse, P. Dalquen (Kantonsspital, Dept of Surgery, Div. of Cardiac & Thoracic Surgery & Pathology Institute, Basel, Switzerland); L. Eckmann, K. Hänni, K. Zimmermann (Tiefenauspital Surg. Clinic, Univ. of Bern, Switzerland); B. Nachbur, H. U. Würsten, H. Cottier, A. Zimmermann (Inselspital Dept. of Thoracic and Cardiovascular Surg. and Pathology Institute, Bern, Switzerland); W. Maurer, M. Kaufmann (Bürgerspital, Surgical Department, Solothurn, Switzerland); H. Denck, E. Zwintz, St. Wuketich (Krankenhaus der Stadt Wien-Lainz, I. Chir. Dept., and Path. Inst., Vienna, Austria); N. Pridun, H. Hackl (Pulmonologisches Zentrum der Stadt Wien, and Path. Inst., Vienna, Austria); E. Moritz, W. Schlick, H. Holzner (II. Chir. University Clinic and Path. Inst., Vienna, Austria); K. Karrer (Institute for Cancer Research, Vienna, Austria); R. G. Crispen (ITR-Biomedical Research, University of Illinois, Chicago, USA); D. S. Freestone, R. Bomford, M. T. Scott, T. Priestman, L. Toy (The Wellcome Research Laboratories, Beckenham, England)** Present address: Cancer Unit, World Health Organization, Geneva, Switzerland
Offprint requests to: K. Stanley, Ludwig Institute for Cancer Research, Inselspital, CH-3010 Bern, SwitzerlandLudwig Lung Cancer Study Group: 相似文献
45.
酪氨酸对大鼠离体Leydig细胞睾酮和cAMP生成的影响 总被引:2,自引:0,他引:2
本实验采用胶原酶消化,Ficoll 密度梯度离心,制备大鼠睾丸 Leydig 细胞悬浮液进行体外培养(每管内含有10~6 细胞),以研究酪氨酸对 Leydig 细胞睾酮和cAMP 生成的影响。实验结果表明,hCG(100mIU)能明显地促进Leydig 细胞睾酮和 cAMP的生成。睾酮从对照组的3.08±0.58ng(X±SD,下同)增加到41.61±1.52ng,cAMP 含量从19.62±2.56pmol增加到153.24±5.92pmol。若将酪氨酸(60μg)与hCG同时加入到细胞培养液中,则睾酮和cAMP 含量分别下降到 19.22±.0.52ng(P<0.01)和92.63±6.02pmol(P<0.05)。但是,酪氨酸羟化酶抑制剂(α-甲基酪氨酸)对酪氨酸抗hCG致睾酮生成作用无阻断效应,而酪氨酸对外源cAMP(2.5mM)诱导的睾酮生成,则有明显的抑制作用,睾酮含量从27.56±1.53ng降至 19.50±0.47ng(P<0.01)。以上实验结果表明,酪氨酸抗hCG致睾酮生成的作用机理与cAMP有关。 相似文献
46.
On primary infection with the Bryan strain of Rous sarcoma virus (RSV), the growth curve of the virus in the brain of Japanese quail was similar to that observed in chicks and turkey poults. Infectious virus disappeared from the brain after inoculation. After an eclipse period during which no virus was detectable, infectious virus began to appear at 2 days and reached maximal titers in the brain samples at 7 days after inoculation. When Japanese quail were infected intracerebrally with RSV, relatively high titers of virus were recovered from brain tissue but not from liver, lung, kidney, or blood of moribund birds. Only tumors produced in the wing web of quail infected subcutaneously yielded high titers of virus. Other tissues yielded no virus, even though wing web tumors appeared as early as in chicks similarly infected. RSV could be propagated in the wing web of quail for at least 14 passages without any loss of infectivity. On the other hand, serial passage in quail brain resulted in a progressive loss of infectivity until virus was completely lost. 相似文献
47.
48.
49.
Characterization of membrane antigens on human cytomegalovirus-infected fibroblasts recognized by human antibodies. 总被引:2,自引:1,他引:1 下载免费PDF全文
The antigens on the surface of human cytomegalovirus (HCMV)-infected fibroblasts which are recognized by human HCMV antibody-positive sera were characterized. Three HCMV-induced polypeptides, with apparent molecular masses of 53 to 63, 94, and 94 to 120 kilodaltons, were precipitated from 125I-surface-labeled cell extracts with different sera obtained from healthy individuals. Renal transplant recipients who were suffering from active HCMV infections recognized the same set of antigens. By the use of monoclonal antibodies, these antigens were identified as polypeptides belonging to the gcI and gcIII families of HCMV glycoproteins. 相似文献
50.
本文报道了1984年在北京密云县古石峪进行的封山育林试验研究。五年中进行了三次复查,证明在植被盖度、灌木草本生物量、多样性指数方面都有增加。四类样地更新较好;两类阳坡干旱型样地更新不良,但引种栓皮栎获得成功。本研究还进行了山杨移根的试验。 相似文献