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   1641870篇
  免费   128648篇
  国内免费   3653篇
耳鼻咽喉   21888篇
儿科学   54907篇
妇产科学   47794篇
基础医学   236927篇
口腔科学   43695篇
临床医学   145568篇
内科学   326621篇
皮肤病学   38380篇
神经病学   133102篇
特种医学   62890篇
外国民族医学   501篇
外科学   247688篇
综合类   38767篇
现状与发展   4篇
一般理论   611篇
预防医学   126056篇
眼科学   37213篇
药学   115712篇
  1篇
中国医学   3912篇
肿瘤学   91934篇
  2021年   12510篇
  2019年   13314篇
  2018年   19225篇
  2017年   14638篇
  2016年   16585篇
  2015年   18542篇
  2014年   25980篇
  2013年   38938篇
  2012年   52138篇
  2011年   55099篇
  2010年   32899篇
  2009年   31242篇
  2008年   50893篇
  2007年   54053篇
  2006年   54523篇
  2005年   52782篇
  2004年   50467篇
  2003年   48063篇
  2002年   46250篇
  2001年   82733篇
  2000年   84563篇
  1999年   70025篇
  1998年   19382篇
  1997年   17583篇
  1996年   17607篇
  1995年   16725篇
  1994年   15231篇
  1993年   14293篇
  1992年   52291篇
  1991年   50194篇
  1990年   48209篇
  1989年   46135篇
  1988年   42121篇
  1987年   41099篇
  1986年   38351篇
  1985年   36669篇
  1984年   27763篇
  1983年   23400篇
  1982年   14235篇
  1981年   12469篇
  1979年   24440篇
  1978年   17306篇
  1977年   14434篇
  1976年   13504篇
  1975年   14081篇
  1974年   16902篇
  1973年   16424篇
  1972年   15359篇
  1971年   14007篇
  1970年   13400篇
排序方式: 共有10000条查询结果,搜索用时 24 毫秒
981.
1. Twenty-two patients hospitalized for treatment of depression were treated under conditions simulating those of home treatment. 2. Full doses of nortriptyline, from 100 to 150 mg/day, were started after baseline observations were made. 3. Two patients were dropped from the study, one for orthostatic hypotension, one for an aberrant response to nortriptyline. Two additional patients developed orthostasis which was easily managed. Otherwise no unusual side effects were noted. 4. After six days of treatment, 9 of 20 patients showed significant improvement with an overall reduction in scores on the Hamilton Depression Scale of 49% for the entire group. 5. Using the weight-adjusted dosage schedule, 18 of the 21 patients attained plasma concentrations of nortriptyline within the presumed therapeutic range; however, no clear relationship could be established between plasma concentrations and clinical response. 6. With proper selection of patients, it should be possible to treat at home some patients who currently are considered to require hospitalization.  相似文献   
982.
We have examined the immunolocalisation of the protein gene product (PGP) 9.5 during neurogenesis in the rat embryo. PGP9.5 was first present at 11.5 days gestation (E11.5): all morphologically recognisable nerve cell bodies and fibres were immunoreactive. In routinely processed, wax-embedded tissues, using a standard immunocytochemical technique, PGP9.5 polyclonal antibody specifically demonstrated the developing nervous system and primitive adrenal chromaffin cells.  相似文献   
983.
Patients treated with high doses of interleukin-2 (IL-2) because of cancer, develop hemodynamic and vasopermeability changes, that resemble those observed in sepsis. These patients thus provide a unique opportunity to study the early events in the development of septic shock. We analysed the changes that occurred in the contact system of coagulation in plasma from 4 patients, who together received seven 12-day cycles of high doses of IL-2. Levels of factor XII and prekallikrein during the cycles progressively fell to 50 and 30% of their initial levels, respectively, whereas significant increases in plasma factor XIIa- and kallikrein-C1-inhibitor complexes were not observed (in 3 out of 211 samples slightly increased levels of both complexes were found). The reductions in factor XII and prekallikrein were only in part due to protein leakage, since levels were still significantly lower, i.e., 80 and 50%, respectively, when corrected for albumin decreases. Levels of high molecular weight kininogen (HMWK) also decreased during IL-2 therapy, however, this decrease paralleled that of albumin. SDS-PAGE analysis of plasma HMWK did not reveal increased cleavage of this protein. The reduction of factor XII and prekallikrein, corrected for protein leakage, significantly correlated with albumin levels and inversely with daily cumulative weight gain in the patients. Thus, we demonstrate that factor XII and prekallikrein decrease during IL-2 therapy. As these decreases, already observed after 1 day treatment, were disproportional to that of albumin, a negative acute phase reactant, and correlated with signs of the vascular leak syndrome, we favor the explanation that they reflected activation rather than a decreased synthesis of the contact system proteins.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
984.
985.
Magnetic resonance imaging was employed to study the dependence of clot lysing patterns on two different modes of transport of urokinase into whole blood clots. In one group of clots (nonperfused clots, n1 = 10), access of urokinase to the fibrin network was possible by diffusion only, whereas in the other group (perfused clots, n2 = 10) bulk flow of plasma containing urokinase was instituted through occlusive clots by a pressure difference of 3.7 kPa (37 cm H2O) across 3 cm long clots with a diameter of 4 mm. It was determined separately that this pressure difference resulted in a volume flow rate of 5.05 +/- 2.4 x 10(-2) ml/min through occlusive clots. Perfused clots diminished in size significantly in comparison to nonperfused ones already after 20 min (p less than 0.005). Linear regression analysis of two-dimensional clot sizes measured by MRI showed that the rate of lysis was more than 50-times faster in the perfused group in comparison to the nonperfused group. It was concluded that penetration of the thrombolytic agent into clots by perfusion is much more effective than by diffusion. Our results might have some implications for understanding the differences in lysis of arterial and venous thrombi.  相似文献   
986.
BACKGROUND AND PURPOSE: Accurate and reproducible determination of the size and location of cerebral infarcts is critical for the evaluation of experimental focal cerebral ischemia. The purpose of this study was to compare intracardiac perfusion of 2,3,5-triphenyltetrazolium chloride with immersion of brain tissue in 2,3,5-triphenyltetrazolium chloride to delineate brain infarcts in rats. METHODS: After 6, 24, or 48 hours of ischemia induced by permanent middle cerebral artery occlusion, some rats were perfused with 2,3,5-triphenyltetrazolium chloride; other rats were given an overdose of barbiturates, after which brain sections were immersed in 2,3,5-triphenyltetrazolium chloride. Coronal sections were taken 4, 6, and 8 mm from the frontal pole, and infarct areas in perfused and immersed sections were compared; subsequently, the same sections were stained with hematoxylin and eosin. RESULTS: In rats subjected to 24 or 48 hours of occlusion, areas of infarction were clearly defined with both 2,3,5-triphenyltetrazolium chloride staining techniques, and the infarct sizes correlated well with the results of hematoxylin and eosin staining (r = 0.85-0.94). CONCLUSIONS: These results demonstrate that intracardiac perfusion of 2,3,5-triphenyltetrazolium chloride is an accurate, inexpensive, and efficient staining method to detect infarcted tissue 24 and 48 hours after the onset of ischemia in rats.  相似文献   
987.
Studies of adults suggest that metered-dose inhalers with spacers are as effective as hand-held nebulizers for bronchodilator delivery. We studied 13 children with acute asthma. They received two puffs every 2 minutes from metered-dose inhalers with spacers (range, 4 to 14 puffs) titrated until improvement stopped. Peak expiratory flow increased 34% for metered-dose inhalers with spacers after the first 2 puffs and increased 87% for metered-dose inhalers with spacers after dose titration. After titration, respiratory rate decreased by 12%, heart rate increased by 2%, and breath sounds improved in 92% of the patients. We concluded that the metered-dose inhalers with spacers are an effective device for the treatment of asthma in the pediatric emergency department and that the use of metered-dose inhalers with spacers with titration can achieve significant bronchodilation in the treatment of patients with acute asthma.  相似文献   
988.
Intratemporal vascular tumors: detection with CT and MR imaging   总被引:1,自引:0,他引:1  
The diagnostic contributions of computed tomography (CT) and magnetic resonance (MR) imaging were compared in 12 patients with benign intratemporal vascular tumors (hemangioma or vascular malformation). The tumors included six in the internal acoustic canal and six in the geniculate ganglion region. Clinical and histologic correlations were made. Two of the six patients with tumors in the internal acoustic canal underwent CT, and both required gas cisternography to show the tumor. Five patients in that group underwent MR imaging, and all five studies showed the tumor. All six patients with geniculate ganglion tumors underwent CT. Results in one study were questionable, and five showed the tumor. Five patients in this group underwent MR imaging, but the MR findings were positive in only two cases. MR imaging should therefore be performed before CT in the evaluation of facial nerve dysfunction, as it demonstrated all tumors in the internal acoustic canal and some in the geniculate ganglion region. If MR findings are negative, CT should then be performed to rule out a possible geniculate ganglion lesion.  相似文献   
989.
Several methods of collecting workload data for use in PharmaTrend, a computerized pharmacy management information system, are described. Although the number of indicators produced by PharmaTrend is limited by the input of the user, the integrity of the indicators that are produced is not compromised; this allows the user to implement PharmaTrend on a limited scale, such as for workload only. Workload data that can be used in PharmaTrend are collected routinely by most pharmacies. Many activities are already recorded in logs and other noncomputerized sources. The aid of members of the pharmacy department and other departments may be enlisted in collecting these data. Self-reporting through time sheets and cards can also be used to obtain data on the distribution of work hours. Recording is simplified if employees are told to record only exceptions to their usual job responsibilities. The PharmaTrend manual contains detailed definitions of the workload categories, but simpler and more practical definitions may have to be used. A computer spreadsheet program should probably be used for compiling data if they are collected from several sources; this will facilitate entry into PharmaTrend. Simple methods are available for capturing workload data for input into the PharmaTrend program.  相似文献   
990.
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